JP2004122681A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an image forming apparatus in which interior of the apparatus and a sheet are protected against contamination by limiting the print area of a print head within the sheet thereby preventing useless recording operation within the image forming apparatus. <P>SOLUTION: In the image forming apparatus, two recording heads 14a and 14b are mounted on a carriage 13 moving in the main scanning direction and ink is ejected from respective nozzle arrays. The carriage 13 has a sheet detection sensor 41 including a light emitting element and a light receiving element, detects one end part of a sheet 3 by reflected light therefrom, calculates a position of the other end part based on the position of one end part, and detects the range of the sheet. When each nozzle array deviates from the range of the sheet, image data is masked so that ink is not ejected from the nozzle array. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus which is applied to an ink jet recording apparatus or the like and detects a sheet width and limits a print area according to the sheet width.
[0002]
[Prior art]
An image forming apparatus that has a scanning unit that scans a sheet on a carriage with a recording head along a predetermined scanning direction, and that drives the recording head based on image data to form an image during scanning of the carriage. In the apparatus, a sensor is provided on the carriage and outputs a signal according to the presence or absence of a sheet at an opposing position, and the carriage is scanned while the sheet is conveyed to a scanning area of the carriage, and the carriage is scanned. Detecting means for detecting a starting position and an ending position of the sheet in the scanning direction based on a change in the output of a sensor; and driving the recording head after the scanning unit starts scanning the carriage in accordance with the starting position. The start position is determined to control the recording operation, and the utility specified on the basis of the interval between the start position and the end position. Image forming apparatus and a recording position adjustment means for controlling the recording width within the width has been known (see Patent Document 1).
Also, it has a sensor that can detect by scanning the paper in the main scanning direction, when the width of the paper detected by the sensor becomes an incorrect value with respect to the width represented by the information received from the host computer, A printer that stops execution of printing is also known (see Patent Document 2).
According to the conventional image forming apparatus, it is possible to keep the image position on the paper constant, but the detecting means needs to detect the start position and the end position of the paper based on the change in the output of the sensor. However, it is not sufficient from the viewpoint of shortening the image forming time.
[0003]
[Patent Document 1]
Patent No. 2958131
[Patent Document 2]
JP 2000-20274 A
[0004]
[Problems to be solved by the invention]
In a conventional image forming apparatus that conveys and prints a sheet of an arbitrary size, when a printing operation is performed on the sheet, the requested printing range may not be within the range of the actual sheet. In such a case, useless printing is performed inside the image forming apparatus or on a portion of the paper transport path where no paper is present. An adverse effect such as generation of dirt occurs.
Therefore, it is necessary to reduce these adverse effects as much as possible by limiting the print area of the print head to only a predetermined range, and it is necessary to detect the actual width of the paper in order to limit the print area.
In addition, particularly in an ink jet recording apparatus, the longer the time the print head (nozzle) is exposed to the outside air, the more adversely the ink in the nozzle dries and hardens. Need to be kept.
[0005]
The present invention has been made in view of the above circumstances, and the objects of the invention of each claim are as follows.
An object of the present invention is to suppress useless printing in an image forming apparatus by detecting a range of a sheet and performing printing only in a specific area.
It is an object of the present invention to estimate the expected position of the other end using the position information of one end of the sheet, and to reduce waste due to carriage movement for detection.
According to a third aspect of the present invention, the movement of the print head is restricted to half the position in the main scanning direction of the sheet transport path, and the determination when the end of the sheet cannot be detected is performed more quickly than in the second aspect of the invention. An object of the present invention is to reduce the time of unnecessary exposure to the outside air. According to a fourth aspect of the present invention, one end of the sheet is detected at the same time as printing, and when the end is detected, the mask release position is determined, and the position of the other end is calculated from the position of the one end. By determining the mask start position, printing can be performed simultaneously with the movement of the carriage, and the width of the image data can be determined by detecting the paper width. An object of the present invention is to eliminate carriage movement required only for detecting a width and improve productivity.
According to a fifth aspect of the present invention, if the carriage reaches half the length of the paper transport path in the main scanning direction and the end of the paper cannot be detected, it is determined that an abnormality has occurred, printing is stopped, and the determination of an abnormality is made. It is an object of the present invention to provide an improvement over the invention of Item 4.
According to a sixth aspect of the present invention, by applying the first to fifth aspects of the present invention, there is provided an ink jet recording apparatus which does not waste ink and the like, has a long print head life, and does not stain the inside of the apparatus and paper. The purpose is to:
[0006]
[Means for Solving the Problems]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the invention according to claim 1 is an image forming apparatus which performs printing by performing main scanning of a print head and sub-scanning of a sheet. A sensor that detects an end of the sheet and moves with the print head, and calculates a range of the sheet in the main scanning direction based on the position of one end of the sheet detected by the sensor. It is characterized in that printing is performed within the range of the paper, whereby the mask release of the image and the start position can be set according to the actually detected paper width, and an image forming apparatus such as a conveyance path other than the paper. To prevent unnecessary printing.
[0007]
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the print head is moved to one end of the sheet in order to detect a range of the sheet in the main scanning direction before starting printing on the sheet. The position of the other end of the sheet is calculated from the detected position of the one end of the sheet, and the width of the sheet in the main scanning direction is detected. Then, the paper width is detected in a shorter time than when both ends of the paper are acquired and the paper width is detected.
[0008]
According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, the print head is moved in a main scanning direction of a paper transport path in order to detect a range of the paper in the main scanning direction before starting printing on the paper. In the main scanning direction, the position of the other end of the sheet is calculated from the detected position of the one end, and the width of the sheet in the main scanning direction. Thus, the protection operation of the recording head can be started more quickly than in the second aspect of the invention, and the deterioration of the state of the head can be prevented.
[0009]
According to a fourth aspect of the present invention, in the image forming apparatus according to the first aspect, when performing movement for the first printing on the paper, one end of the paper in the main scanning direction is detected at the same time as printing. The position of the other end of the sheet is calculated from the detected position of one end of the sheet, and the calculated position is used as the width of the sheet in the main scanning direction. In addition, since there is no need to move only for detecting the positions of both ends of the sheet, productivity is improved.
[0010]
According to a fifth aspect of the present invention, in the image forming apparatus according to the first aspect, when performing the movement for the first printing on the paper, the print head is moved to a half of a main scanning direction of a paper transport path, or to perform printing. Move to the necessary movement range, detect one end of the paper in the main scanning direction at the same time as printing, and detect the position of the other end of the paper from the detected position of one end of the paper. And calculating the width of the sheet in the main scanning direction, whereby the abnormality can be determined more quickly than in the invention of claim 4, so that the print head protection operation can be performed more quickly in the event of an abnormality. The productivity when no abnormality occurs is also improved as compared with the third aspect.
[0011]
According to a sixth aspect of the present invention, in the image forming apparatus according to the first to fifth aspects, the print head is an ink jet print head, so that ink and the like are not wasted, and the print head life is extended. In addition, it is possible to provide an ink jet recording apparatus that does not stain the inside of the apparatus and the recording medium.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described based on examples shown in FIGS. 1 to 16. (Example 1)
FIG. 1 is a perspective view illustrating a mechanism of the inkjet recording apparatus according to the first embodiment. FIG. 2 is a side view of the mechanism of the inkjet recording apparatus illustrated in FIG.
The ink jet recording apparatus according to the first embodiment includes a carriage 13 movable in the main scanning direction inside a recording apparatus main body 1, a recording head 14 including an ink jet head mounted on the carriage, and a subtank (ink cartridge) for supplying ink to the recording head. A paper feed cassette 4 (or a paper feed tray) in which a printing mechanism unit 2 and the like constituted by 12 and the like are stored and a large number of sheets 3 can be loaded from the front side under the recording apparatus main body 1. Can be freely inserted and removed, and a manual tray (not shown) for manually feeding the paper 3 can be provided to be opened. As a result, the paper 3 fed from the paper feed cassette 4 or the manual feed tray is taken in, a required image is recorded by the printing mechanism unit 2, and then discharged to the paper discharge tray 6 mounted on the rear side.
[0013]
The printing mechanism 2 holds a carriage 13 slidably in a main scanning direction (a direction perpendicular to the paper of FIG. 2) by a main guide rod 11 which is a guide member which is laterally mounted on left and right side plates (not shown). Indicates that a recording head 14 composed of ink jet heads for discharging ink droplets of yellow (Y), cyan (C), magenta (M), and black (Bk) is mounted with the ink droplet discharging direction facing downward, Above 13, each sub-tank 12 for supplying each color ink to the recording head 14 is mounted.
[0014]
Each sub-tank 12 is connected to each of the ink tanks 15 that are exchangeably mounted via an ink supply tube 16, and receives supply of ink from the ink tank 15.
The carriage 13 is slidably fitted on the main guide rod 11 on the rear side (downstream side in the sheet conveying direction). In order to move and scan the carriage 13 in the main scanning direction, a timing belt 20 is stretched between a driving pulley 18 and a driven pulley 19 that are driven to rotate by a main scanning motor 17. It is fixed to.
[0015]
Although the recording heads 14 of each color are used here as the recording heads 14, a single recording head having nozzles for ejecting ink droplets of each color may be used. Further, the ink jet head used as the recording head 14 is a piezo type which pressurizes ink through a vibration plate forming a wall of a liquid chamber (ink flow path) by an electromechanical transducer such as a piezoelectric element, or a heating resistor. A bubble type in which bubbles are generated by film boiling to pressurize the ink, or a static pressure in which the diaphragm is displaced by an electrostatic force between a diaphragm forming an ink flow path wall surface and an electrode opposed thereto to pressurize ink. Although an electric type or the like can be used, in this embodiment, an electrostatic type ink jet head is used.
[0016]
On the other hand, in order to transport the paper 3 set in the paper feed cassette 4 to the lower side of the recording head 14, the paper feed roller 21 and the friction pad 22, which separate and feed the paper 3 from the paper feed cassette 4, and guide the paper 3 A guide member 23 to be fed, a transport roller 24 for transporting the fed paper 3 in reverse, a transport roller 25 pressed against the peripheral surface of the transport roller 24, and a feed angle of the paper 3 from the transport roller 24. A tip roller 26 is provided. The transport roller 24 is driven to rotate by a sub-scanning motor 27 via a gear train.
[0017]
Further, an electrostatic transport belt 29 that guides the sheet 3 sent from the transport roller 24 below the recording head 14 in accordance with the movement range of the carriage 13 in the main scanning direction is provided. The electrostatic transport belt 29 plays a role of adsorbing the transported paper 3 by being charged by the charger 30 and keeping the paper surface and the recording head surface in parallel. On the downstream side of the electrostatic transport belt 29 in the paper transport direction, a paper discharge roller 33 that sends out the paper 3 to the paper discharge tray 6 is provided.
[0018]
Further, a sheet reversing unit 8 and a sheet feeding unit 9 can be attached to the recording apparatus main body 1 as needed.
The paper reversing unit 8 includes a second transport roller 34 and a third transport roller 35. After printing on the surface of the paper 3 by the recording head 14, the transport roller 24 is reversed to draw the paper 3 into the recording apparatus main body 1. Then, the sheet 3 is reversed by passing through the second conveying roller 34 and the third conveying roller 35 in the sheet reversing unit 8 and sent to the conveying roller 24, and recording is performed with the back side of the sheet 3 facing the recording head 14 side. The sheet is conveyed below the head 14 and backside printing is performed.
The paper supply unit 9 includes a second paper supply roller 36, a friction pad 37, a carry-out roller 38, and the like, and can accommodate a large amount of paper of the same size or a different size as the paper stored in the paper supply cassette 4, Any one of the sheets can be appropriately selected and used.
[0019]
A reliability maintenance / recovery mechanism 39 for maintaining / recovering the reliability of the recording head 14 is disposed on the right end side in the moving direction of the carriage 13. The carriage 13 is moved toward the reliability maintenance / recovery mechanism 39 during the printing standby, and the recording head 14 is capped by the capping means or the like.
[0020]
Next, an operation relating to detection of an end position of a sheet in the main scanning direction and an image data mask will be described.
FIG. 3 is a cross-sectional view of a part of the inkjet recording apparatus as viewed from the front.
Two print heads 14a and 14b are mounted on the carriage 13, and the print heads 14a and 14b each have two nozzle rows 14a. ₁ , 14a ₂ , And 14b ₁ , 14b ₂ Are arranged, and ink is ejected from each nozzle row.
When the carriage 13 is at the position shown in FIG. 3, the recording head 14a is covered with a cap 39a, and the recording head 14b is covered with a suction / cap 39b to keep the recording head surface moist and hardly cause clogging of ink in the nozzle rows. Is protected.
The paper detection sensor 41 is installed on the left side when viewed from the front of the carriage 13.
[0021]
FIG. 4 is a diagram illustrating a state in which a sheet detection sensor is detecting a sheet, and FIG. 5 is a diagram illustrating a state in which a sheet is not being detected.
The paper detection sensor 41 has a light emitting element 42 and a light receiving element 43, and detects the presence or absence of the paper 3 from the reflection of light. The electrostatic transport belt 29 serves to transport the paper 3 while maintaining the flatness of the paper by adsorbing the paper 3 by static electricity.
As shown in FIG. 4, when the paper detection sensor 41 is on the paper 3, the light emitted from the light emitting element 42 is reflected by the paper 3 supported on the electrostatic transport belt 29, Received.
As shown in FIG. 5, when the sheet detection sensor 41 is not on the sheet 3, the light emitted from the light emitting element 42 is applied to the darkly applied electrostatic belt 29, so that the light receiving element 43 is not reflected. I can't get light. In this manner, the presence or absence of the paper 3 can be detected based on the presence or absence of the sensitivity of the light receiving element 43.
[0022]
FIG. 6 is a diagram showing a state where the carriage has moved in the main scanning positive direction from the capping position.
At the carriage position shown in FIG. 6, the sheet detection sensor 41 does not detect the sheet 3. FIG. 7 is a diagram showing a state in which the carriage has moved in the main scanning positive direction from the carriage position shown in FIG.
At the position in FIG. 7 where the carriage 13 has further advanced in the main scanning positive direction (left direction in the drawing), the sheet detection sensor 41 detects the sheet 3.
[0023]
FIG. 8 is a diagram showing the relationship between the sheet detection sensor and each nozzle row.
In FIG.
S1 is the sheet detection sensor 41 and the first nozzle row 14a ₁ Distance between
S2 is the sheet detection sensor 41 and the second nozzle row 14a ₂ Distance between
S3 is the sheet detection sensor 41 and the third nozzle row 14b ₁ Distance between
S4 is the paper detection sensor 41 and the fourth nozzle row 14b ₂ Distance between
Is shown.
[0024]
FIG. 9 is a block diagram illustrating a control system of the inkjet recording apparatus according to the first embodiment.
The CPU 50 drives the sub-scanning motor 27 and the paper feed clutch 59 by giving commands to the sub-scanning motor operation command circuit 56 and the paper feed clutch driver 58 to feed the paper 3 from the paper feed cassette 4 and to carry the paper. Do.
Further, the CPU 50 drives the main scanning motor 17 via the main scanning motor driver 55 by giving a command to the main scanning motor operation command circuit 54 to move the carriage 13 in the main scanning direction.
At this time, the CPU 50 can know the position of the carriage 13 by reading the output signal of the main scanning encoder 60 via the main scanning motor command circuit 54.
[0025]
The operation unit 53 includes an LCD, an LED, and the like (not shown), and has a role of notifying an operator (not shown) of the state of the apparatus according to a command from the CPU 50.
Reference numeral 51 denotes a non-volatile memory, which can hold written data even when the power is turned off, and is constituted by, for example, an SRAM or an E2PROM with a built-in battery.
Reference numeral 52 denotes an image memory which stores image data to be printed, and is constituted by, for example, an SDRAM.
[0026]
The image data read from the image memory 52 is decompressed from a compressed state by a decompression circuit 61, further processed by an image mask circuit 62 as to whether or not to be masked, and is processed by a recording head via an I / F circuit 63. 14.
Here, the decompression circuits 61, the image mask circuits 62, and the I / F circuits 63 are prepared by the number of nozzle rows, respectively, and can process data of each nozzle row in parallel.
An output signal of the main scanning encoder 60 is input to the I / F circuit 63, and image data is sent to the recording head 14 in synchronization with the main scanning position of the carriage 13.
Further, the CPU 50 can mask the output image at an arbitrary timing by giving a command to the image mask circuit 62.
The output signal of the paper detection sensor 41 is input to the CPU 50.
[0027]
Next, a process for detecting a sheet edge will be described.
FIG. 11 is a flowchart illustrating a process of detecting a sheet edge.
The CPU 50 feeds and transports the sheet 3 onto the electrostatic transport belt 29 (S1, S2).
After the transport operation is completed, the driving of the carriage 13 is started, and the carriage is moved in the main scanning positive direction (S3, 4).
Thereafter, the carriage position at the timing when the output of the paper sensor 41 changes from OFF to ON is read, and the position is stored as the right end position Pr of the paper (S5, 6).
The stored right end position Pr and the left end of the sheet expected from the center of the transport path are calculated, and the calculated position is stored as the left end position Pl of the sheet (S7).
When the left and right end positions of the sheet are detected in this way, the carriage is driven in the negative direction of the main scanning and returned to the cap position, and then the capping is performed to complete the sheet end position detection operation (S8, 9). .
The above operation can be performed simultaneously with the printing operation.
[0028]
Next, an image masking operation will be described.
FIG. 12 is a flowchart showing the processing of the mask operation.
here,
The coordinates Pms at which the masking of the image is started are determined by the right edge Pr of the sheet detected in the process of FIG.
The coordinates Pme at which the masking of the image is ended is determined by the left end Pl of the sheet calculated in the process of FIG.
Paper detection sensor 41 and first nozzle row 14a ₁ The distance between S1
Paper detection sensor 41 and second nozzle row 14a ₂ The distance between S2
Paper detection sensor 41 and third nozzle row 14b ₁ The distance between S3
Paper detection sensor 41 and fourth nozzle row 14b ₂ The distance between S4
Then
First nozzle row 14a ₁ Is the mask release start coordinate of Ps1 = Pr + S1
Second nozzle row 14a ₂ Is the mask release start coordinate of Ps2 = Pr + S2
Third nozzle row 14b ₁ Is the mask release start coordinate of Ps3 = Pr + S3
Fourth nozzle row 14b ₂ Is the mask release start coordinate of Ps4 = Pr + S4
First nozzle row 14a ₁ Is the mask release end coordinates of Pe1 = Pl + S1
Second nozzle row 14a ₂ Is the mask release end coordinates of Pe2 = Pl + S2
Third nozzle row 14b ₁ Is the mask release end coordinate of Pe3 = Pl + S3
Fourth nozzle row 14b ₂ Is the mask release end coordinate of Pe4 = Pl + S4
Is calculated.
[0029]
The CPU 50 feeds and transports the sheet 3 onto the electrostatic transport belt 29 (S11, 12).
After the transfer operation is completed, the image masks of all the nozzle rows are enabled (S13), and then the driving of the carriage 13 is started, and the carriage 13 is moved in the main scanning positive direction (S14, 15).
Thereafter, when the carriage position P reaches Ps4, the fourth nozzle row 14b ₂ Is released (S16, S17).
Third nozzle row 14b ₁ From the first nozzle row 14a ₁ Also, the mask release processing is performed at the position where the carriage 13 has reached the respective mask release start positions Psx (S18 to S23).
Thereafter, when the carriage position P reaches Pe4, the fourth nozzle row 14b ₂ Are enabled (S24, S25).
Third nozzle row 14b ₁ From the first nozzle row 14a ₁ Also, the mask valid processing is performed at the position where the carriage 13 has reached the respective mask release end positions Pex (S26 to S31).
When the carriage position P reaches the terminal end, the carriage is returned in the negative direction of the main scanning, capping is performed, and the movement is completed (S32, 33).
In the section from the start to the end of the image mask release of each nozzle array, the image mask circuit does not perform the process of masking the image, and the data supplied to the recording heads 14a and 14b during that period is ejected from the nozzle array as an effective image. You.
Conversely, in a section in which the mask of each nozzle row is not released, a process of masking an image is performed by the image mask circuit, during which white data is given to the recording heads 14a and 14b, and ink from the nozzle row is removed. Not injected.
[0030]
FIG. 10 is a block diagram showing a modification of the image mask circuit in the control system shown in FIG.
In the processing shown in the flowchart of FIG. 12, the CPU 50 controls the image mask circuit in real time while monitoring the carriage position P. However, by using a circuit as shown in the block diagram of FIG. 11, the processing load of the CPU is reduced. Can be lowered.
The CPU writes the mask release start position in the register 65 in advance.
When the carriage starts moving, a main scanning encoder signal is input to the main scanning counter 64, and the carriage position is measured by the main scanning counter 64.
Here, when the carriage position measured by the main scanning counter 64 matches the position written in the register 65, a mask release start signal is output from the comparator 66 and given to the image mask circuit 62 to start the image mask release. You.
Regarding the termination of the image mask release, the circuits 68 to 70 having the same configuration as those of 64 to 66 output a mask release end signal when the carriage reaches the image mask release end position, and are given to the image mask circuit 62. Then, the image mask release ends.
[0031]
(Example 2)
Second Embodiment An image forming apparatus according to a second embodiment will be described.
FIG. 13 is a diagram illustrating the positional relationship between the fed paper and the electrostatic transport belt.
In the case where the center of the fed sheet 3 and the center of the electrostatic transport belt 29 coincide with each other, it is possible to calculate the range of the sheet by acquiring the position information of one end of the sheet 3. It is possible to obtain the range of the sheet more quickly.
FIG. 14 is a flowchart illustrating a process performed by the image forming apparatus according to the second embodiment. When a print request is issued to the ink jet recording apparatus, after the paper feeding is completed (S41, 42), the carriage is moved from the home position until one edge of the paper can be detected (S43 to 45), and the end of the paper is moved. The position of the carriage at the time of detection is set as the position Pr of the right end of the sheet (S46, 47), and the movement of the carriage is stopped (S48).
With respect to the detected position Pr of the right end of the sheet, the other end Pl of the sheet is determined at a position symmetrical with respect to the center position of the conveyance path in the main scanning direction, so that the sheet can be moved with a minimum operation. Based on both ends in the main scanning direction, mask release and mask start position are determined based on this value to limit the printing range. If the end of the sheet cannot be detected even if the carriage is moved to the operable leftward position, it is determined as abnormal (S45, 49), and the printing operation is terminated (S50, 51).
[0032]
(Example 3)
Third Embodiment An image forming apparatus according to a third embodiment will be described.
As shown in FIG. 13, in the case of a configuration in which the center of the paper 3 to be fed and the center of the electrostatic transport belt 29 match, the carriage is moved until the sensor 41 on the carriage 13 passes through the center of the electrostatic transport belt. If the end of the sheet cannot be detected during the movement of the position 13, it is determined that the sheet is in an abnormal state in which the sheet cannot be detected, the operation of the carriage is stopped, and the operation returns to the reliability maintenance / recovery mechanism 39 to cap each nozzle. .
[0033]
(Example 4)
Fourth Embodiment An image forming apparatus according to a fourth embodiment will be described.
FIG. 15 is a flowchart illustrating a process performed by the image forming apparatus according to the fourth embodiment. After the paper is fed (S61, 62), the carriage of the carriage is started for printing after enabling the mask of the image (S63-65), and when the right end of the paper is detected (S66), the position of the carriage is determined. Is stored as the position Pr of the sheet edge (S67), and based on this position, the image mask release position of each nozzle row is set as in the processing shown in FIG. 12 (S68).
At the same time, the left end of the sheet is calculated from the detected position Pr and the center position of the transport path, and the value is set as the position Pl of the left end of the sheet (S69), and the mask start position is set as in the process shown in FIG. It is set (S70).
As described above, while the edge of the sheet is detected at the same time as printing, the mask release and the start of the mask are set for each nozzle row when the detection is completed. After the printing is completed, the carriage is moved to the position 0, and the cap is completed (S71).
[0034]
(Example 5)
An image forming apparatus according to the fifth embodiment will be described.
FIG. 16 is a flowchart illustrating a process performed by the image forming apparatus according to the fifth embodiment. The image forming apparatus according to the fifth embodiment performs the printing operation and the detection of the right edge of the sheet at the same time as the image forming apparatus according to the fourth embodiment. However, even if the carriage is moved to the center of the sheet transport path, the edge of the sheet cannot be detected. , The printing operation is stopped, and the recording head is returned and capped.
That is, in the flowchart showing the processing of the fifth embodiment, the main parts of S61 to S71 are similar to the flowchart shown in FIG. 15, and the carriage movement for printing is started after the image mask is enabled ( If the carriage reaches the center position of the electrostatic transport belt before the right edge of the sheet is detected, the right edge of the subsequent sheet cannot be detected, so that the recording head is returned and capped (S81, S82). Is added.
[0035]
【The invention's effect】
As is clear from the above description, the present invention has the following effects.
According to the first aspect of the present invention, since the sheet width can be detected, the mask release and the start position of the image can be set according to the actually detected sheet width. It is possible to suppress unnecessary printing in the forming apparatus.
[0036]
According to the second aspect of the invention, if only one end of the sheet is detected, the other end can be calculated. The paper width can be detected in a short time.
[0037]
According to the third aspect of the present invention, it is possible to determine an abnormal situation such as an inability to obtain the sheet width earlier than in the second aspect of the present invention. The print head can be prevented from deteriorating.
[0038]
According to the fourth aspect of the present invention, since the right end of the sheet can be detected simultaneously with the movement for printing, it is not necessary to move just to know the positions of both ends of the sheet as compared with the second aspect of the invention. Therefore, productivity is improved.
[0039]
According to the fifth aspect of the present invention, since the right edge of the sheet is detected simultaneously with printing, if the right edge of the sheet cannot be detected up to the center position in the main scanning direction of the sheet transport path, an abnormality is detected earlier than in the fourth aspect. Therefore, there is an effect that the print head protection operation can be performed quickly when an abnormality occurs, and the productivity when no abnormality occurs is also improved as compared with the third aspect of the present invention.
[0040]
According to the invention of claim 6, in the invention of claims 1 to 5, the print head is an ink jet recording head, so that ink and the like are not wasted, the life of the print head is long, and the inside of the apparatus and the recording medium are soiled. It is possible to provide an ink jet recording apparatus without any problem.
[Brief description of the drawings]
FIG. 1 is a perspective view illustrating a mechanism of an inkjet recording apparatus according to a first embodiment.
FIG. 2 is a side view showing a mechanism of the inkjet recording apparatus shown in FIG.
FIG. 3 is a cross-sectional view of a part of the inkjet recording apparatus shown in FIG. 1 as viewed from the front.
FIG. 4 is a diagram illustrating a state where a sheet detection sensor is detecting a sheet.
FIG. 5 is a diagram illustrating a state where a sheet detection sensor does not detect a sheet.
FIG. 6 is a diagram illustrating a state where a carriage has moved in a main scanning positive direction from a capping position.
7 is a diagram illustrating a state in which the carriage has moved in the main scanning positive direction from the carriage position illustrated in FIG. 6;
FIG. 8 is a diagram illustrating a relationship between a sheet detection sensor and each nozzle row.
FIG. 9 is a block diagram illustrating a control system of the inkjet recording apparatus according to the first embodiment.
FIG. 10 is a block diagram showing a modification of the control system shown in FIG.
FIG. 11 is a flowchart illustrating a process of detecting a sheet edge.
FIG. 12 is a flowchart illustrating processing of an image masking operation.
FIG. 13 is a diagram illustrating a relationship between an electrostatic transport belt and a sheet.
FIG. 14 is a flowchart illustrating processing performed by the image forming apparatus according to the second exemplary embodiment.
FIG. 15 is a flowchart illustrating a process performed by the image forming apparatus according to the fourth embodiment.
FIG. 16 is a flowchart illustrating a process performed by the image forming apparatus according to the fifth embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Recording device main body, 2 ... Printing mechanism part, 3 ... Paper, 4 ... Paper feed cassette (paper feed tray), 5 ... Manual feed tray, 6 ... Paper discharge tray, 8 ... Paper reversing unit, 9 ... Paper feed unit, 11: Main guide rod, 12: Sub tank, 13: Carriage, 13a: Paper sensor, 14, 14a, 14b: Recording head, 14a1, 14a2, 14b1, 14b2: Nozzle row, 15: Ink tank (ink cartridge) 15, 16 ... Ink supply tube, 17 ... Main scanning motor, 18 ... Drive pulley, 19 ... Driving pulley, 20 ... Timing belt, 21 ... Paper feed roller, 22 ... Friction pad, 23 ... Guide member, 24 ... Transport roller, 25 ... Transport Roller, 26: Tip roller, 27: Sub-scanning motor, 29: Electrostatic transport belt, 30: Charger, 33: Discharge roller, 34: Second transport Roller 35, a third transport roller 36, a second paper feed roller 37, a friction pad 38, an unloading roller 39, a reliability maintaining / recovering mechanism 39a a cap 39b a suction / cap, 41 a paper detection Sensor, 42: Light emitting element, 43: Light receiving element, 50: CPU, 51: Non-volatile memory, 52: Image memory, 53: Operation unit, 54: Main scanning motor operation command circuit, 55: Main scanning motor driver, 56 ... Sub-scanning motor operation command circuit, 55: Sub-scanning motor driver, 58: Feeding clutch driver, 59: Feeding clutch, 60: Main scanning encoder, 61: Decompression circuit, 62: Image mask circuit, 63: I / F circuit , 64, 68 ... main scanning counter, 65, 69 ... register, 66, 70 ... comparator.

Claims (6)

In an image forming apparatus that performs printing by performing main scanning of a print head and sub-scanning of paper,
A sensor that detects an end of the sheet in the main scanning direction and moves together with the print head, and calculates a range of the sheet in the main scanning direction based on the position of one end of the sheet detected by the sensor. An image forming apparatus, wherein the print head performs printing within a range of the sheet. The image forming apparatus according to claim 1,
Before starting printing on the sheet, the print head is moved until one end of the sheet is detected in order to detect a range of the sheet in the main scanning direction, and one end of the detected sheet is detected. An image forming apparatus that calculates the position of the other end of the sheet from the position of the sheet and uses the calculated position as the width of the sheet in the main scanning direction. The image forming apparatus according to claim 1,
Before starting printing on the paper, in order to detect the range of the paper in the main scanning direction, the print head is moved to half of the main scanning direction of the paper conveyance path, and one end of the paper is detected. An image forming apparatus that calculates a position of the other end of the sheet from the detected position of the one end and uses the calculated position as the width of the sheet in the main scanning direction. The image forming apparatus according to claim 1,
When performing the movement for the first printing on the paper, one end of the paper in the main scanning direction is detected at the same time as printing, and the other end of the paper is detected from the detected position of one end of the paper. An image forming apparatus comprising: calculating a position of an end portion; and setting a width of the sheet in a main scanning direction. The image forming apparatus according to claim 1,
When performing the movement for the first printing on the paper, the print head is moved to a half of the main scanning direction of the paper transport path or a movement range necessary for printing, and the printing is performed simultaneously with the main printing of the paper. Detecting one end of the sheet in the scanning direction, calculating the position of the other end of the sheet from the detected position of the one end of the sheet, and setting the width of the sheet in the main scanning direction. Image forming apparatus. The image forming apparatus according to claim 1, wherein
The image forming apparatus according to claim 1, wherein the print head is an inkjet print head.

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