JPH03197165A - Image forming apparatus - Google Patents

Abstract

PURPOSE:To prevent that an image is formed on a drum by forming an image corresponding to the smaller size data among the size data from both of the first output means outputting the size data of a supplied recording medium and the second output means outputting the size data of the recording medium on the drum. CONSTITUTION:A cassette size sensor outputs the size data related to the size of the paper feed cassette mounted on an apparatus main body 1 by the first output means provided to the paper feed cassette 15. A detection part 13 as the second output means is arranged at the position becoming upstream from a thermal head 5 with respect to the rotary direction at a printing time of a platen drum 3 to judge the position of the paper wound around the platen drum 3 on the basis of the data detected by the detection part 13. When the sizes of the recording media outputted from the first and second output means are different, the control related to the formation of an image is performed corresponding to smaller side data. Therefore, even when a recording medium having a size different from a scheduled size is fed, an image is properly formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an image forming apparatus applied to electronic copying machines, laser printers, and the like.

(Prior Art) A conventional image forming apparatus stores paper of a predetermined size as a recording medium, and is provided with a removable paper feed cassette for taking out and feeding the stored paper one by one. After the paper fed from the paper feed cassette is wound around the platen drum, an image is formed on the paper by a thermal head.

In such conventional image forming apparatuses, when paper is fed from a paper cassette, information regarding the presence or absence of paper stored in the paper cassette and the size of the paper, so-called paper size (hereinafter referred to as size information), is stored in the paper cassette. ) is output. Therefore, control related to image formation, for example, the timing of starting or ending image formation, is determined in accordance with the size information output from the paper feed cassette.

(Problem to be Solved by the Invention) However, the paper size corresponding to each specified paper cassette is usually set in advance, and the size of the paper corresponding to the paper cassette is set in advance. If paper of a size other than the specified paper size is mixed in and stored, the paper of a size different from the size information output from the paper feed cassette will be wound around the platen drum and image formation will be performed. This may cause some inconvenience.

For example, if a paper smaller than the specified size that should be stored in the paper cassette is mixed into the paper cassette, the paper that is wrapped around the platen drum will be overflowed and printed directly onto the circumferential surface of the platen drum. There were times when I had to put it away. Therefore, when the next sheet of paper is wound around the platen drum, there is a problem in that the back side of this sheet becomes dirty.

Furthermore, if such a condition occurs as a result of deformation, there is a problem in that ink adheres to the platen drum, causing unevenness, making it difficult for the ink to adhere to the paper during image formation, and resulting in a decrease in quality. was.

[Structure of the Invention] (Means for Solving the Problem) The means provided by the present invention to achieve the above object are a supply means for supplying a recording medium and a size of the recording medium supplied by the supply means. a drum that rotates around which a recording medium supplied by the supply means is wound; an image forming means that forms an image on the recording medium on the drum; a second output means for detecting the size of the above recording medium and outputting size information of the recording medium; a size of the recording medium based on the size information from the first output means; and the second output. and a control means for comparing the size information of the recording medium based on the size information from the means and controlling the image forming means according to the smaller size information.

(Function) The present invention has a first information output means for outputting size information regarding the size of the recording medium supplied from the supply means when the recording medium is supplied from the supply means. . In addition, the recording medium wound around the drum is conveyed by the rotation of this drum, and the size of the recording medium being conveyed in this way is detected and the size information of the recording medium is output. A second output means is arranged. Comparing the size of the recording medium based on the size information output from the first output means and the size of the recording medium based on the size information output from the second output means,
If the sizes are different, image formation is controlled according to the smaller size information.

Therefore, even if a recording medium of a size different from the planned specific size is supplied by the supply means,
Image formation can be performed appropriately depending on the size of the recording medium actually supplied.

(Embodiment) An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic diagram of an image forming apparatus, such as a full-color copying apparatus, to which the present invention is applied.

On the upper side of the image forming apparatus main body (hereinafter simply referred to as the apparatus main body) 1, there is a document table 20 formed of a glass plate or the like on which a document is placed, and a document cover 22 that can be opened and closed on the top of this document table 20. It is provided.

The halogen lamp 24 is for irradiating light onto the document, and the glue deflector 26 serves as a reflector that collects the light from the halogen lamp 24 onto the surface of the document.
It is set up to cover.

The light reflected from the surface of the original enters the lens 32 via mirrors 28, 30a, and 30b. The light passing through the lens 3 is applied to a photoelectric converter 36 via mirrors 34a and 34b.

The charging converter 36 photoelectrically converts the light reflected from the original, and separates and outputs the image of the original as cyan, green, and yellow (or red, green, and blue) light color signals. It is mainly composed of image sensors and the like.

Further, a platen drum 3 is provided approximately at the center of the apparatus main body 1 . The periphery of the platen drum 3 is made of an elastic member such as black rubber, and has a support and transfer function similar to that of a so-called platen roller. Further, the length of the platen drum 3 is set to be longer than the length of the paper P used as a recording medium. Also, the platen drum 3 is
to form an image. That is, in the printing process for printing images, it rotates in the direction F1 shown in FIG. 1, and in the discharge process for discharging the printed paper P, it is rotationally driven in the direction F2 by a platen motor (not shown).

A thermal head 5 is provided below the platen drum 3. This thermal head 5 is attached to a heat sink 7. Further, an ink ribbon 9 is interposed between the thermal head 5 and the platen drum 3. The ink ribbon 9 is wound around the respective winding cores of the ink ribbon cartridges 11a and llb via a pinch roller 10. This ink ribbon cartridge lla, 11
Each winding core b is connected to a drive shaft of a ribbon motor via a drive force transmission mechanism (not shown), so that the ink ribbon 9 is transported in synchronization with the circumferential speed of the platen drum 3. Further, the pinch roller 10 is driven by a pinch roller solenoid (not shown).

Also, the left side of the platen drum 3, that is, the platen drum 3
A detection unit 13 as a second output means is arranged at a position upstream of the thermal head 5 with respect to the rotation direction F1 during image printing. This detection unit 13 is formed of a plurality of detectors, for example, seven optical sensors, and is configured to detect rotation of the platen drum 3 in a direction perpendicular to the conveyance direction in which the paper P wound around the platen drum 3 is conveyed. The optical sensors are arranged in a line along the axial direction at appropriate intervals so as to be able to detect the width of the maximum paper used. This sensor is a so-called reflection type sensor, which detects the difference in the amount of reflected light reflected from the surface of the platen drum 3 and the amount of reflected light reflected from the surface of the paper P wound around the platen drum 3. By this detection, the presence or absence of paper P can be detected.

Based on the information detected by the detection unit 13, the size of the paper wound around the platen drum 3, that is, the width and length of the actually fed paper is determined. Further, the size of the fed paper P is similarly determined based on the detection information from 13. That is, the width of the paper P is detected from the detection signals of a plurality of optical sensors, and the length of the paper P is determined from the detection signals of the leading and trailing edges of the paper P from predetermined optical sensors. Furthermore, the detection unit 1
Based on the detection information from 3, for example, the timing related to printing and the timing related to the paper ejection operation are determined depending on the timing at which the trailing edge of the paper is detected.

Note that the detection section 13 may be configured using an appropriate sensor such as a CCD type line image sensor.

A paper feed cassette 15 is attached to the lower side of the apparatus main body 1 so as to be freely attachable and detachable to the apparatus main body 1. This paper feed force cellar 15 accommodates paper P of a predetermined size.

Further, inside or near the paper feed cassette 15, there is a sensor 19 for detecting the presence or absence of paper P, and a sensor 19 for detecting the presence or absence of paper P.
a pickup roller 17 for taking out the sheets one by one;
A cam motor (not shown) for driving the pickup roller 17, a feed roller for transporting the paper P, a feed motor for driving the feed roller, and a pair of transport rollers 21 for transporting the paper P.
are provided to ensure that each sheet of paper P stored in the paper feed cassette 15 is fed to the platen drum 3 one by one.

The guide plate 23 holds the paper P fed from the paper cassette 15.
is guided to the paper clip 25.

The vapor clip 25 is fixed to the surface of the platen drum 3 and is used to pinch the leading edge of the paper P fed from the paper feed cassette 15 and wind and fix the paper P around the platen drum 3.

Further, pressure rollers 27 are provided at appropriate positions around the platen drum 3 so as to press the platen drum 3, and this pressure roller 27 prevents the paper P from floating up.

Further, two manual paper feed devices for manually feeding paper are provided above the paper feed cassette 15 described above.
The paper P fed by the manual paper feeder 29 is transported by a pair of transport rollers 21 as described above, and is transferred to the paper clip 25 via the guide plate 23.

When the leading edge of the paper P is fixed to the platen drum 3 by the vapor clip 25, the platen drum 3 is rotated in the direction F.
1, the paper P is wound around the surface of the platen drum 3.

Further, the paper P wound around the platen drum 3 is conveyed according to the rotation of the platen drum 3 in the direction F1,
When this paper P passes through the printing area 6, the aforementioned thermal head 5 is pressed against the platen drum 3, so that image formation, that is, printing is performed.

The printing process for the first color is completed when the platen drum 3 rotates approximately once in the direction F1. At this time, the pressure applied to the thermal head 5 is temporarily released, the ink ribbon 9 is wound up, and the next color is located.

Next, the platen drum 3 rotates again in the direction F1, printing is performed by the thermal head 5, and the next color is printed in an overlapping manner.

In this way, for full-color copying, yellow
Overlapping printing is performed four times corresponding to each color of magenta, cyan, and black. Further, when the colors to be printed are yellow, magenta, and cyan, three overlapping printings are performed. Further, if the color to be printed is a single color such as black, one printing operation is performed.

A paper discharge tray 31, a pair of rollers 33 for transporting the paper to the paper discharge tray 31, and a guide plate 35 for guiding the paper to the pair of rollers 33 are provided above the paper feed cassette 15.

When discharging the paper P on which the printing process has been completed to the paper discharge tray 31, the platen drum 3 is rotated in the direction F1 until the rear end of the paper P reaches the guide plate 35. When the trailing edge of the paper P reaches the guide plate 35, the platen drum 3 is rotated in the direction F.
2, the rear end of the paper P is separated from the platen drum 3 by a separation claw (not shown), and the paper P is guided to the guide plate 35. Then, the paper P is transferred to the paper output tray 31 by a pair of rollers 33, and at this time, the leading edge of the paper P is released from the paper clip 25, and this paper P is transferred to the paper output tray 31.
1.

Also, on the left side of the platen drum 3 are a plurality of printed circuit boards 3.
7 is included. The printed circuit board 37 is provided with various circuit sections such as a judgment processing circuit for performing various judgment processes based on the detection information from the detection section 13. The cooling fan 39 is for cooling the inside of the main body 1 of the apparatus. Further, a power supply 41 supplies a predetermined power to each part.

Next, with reference to FIG. 2, the configuration of the circuit section incorporated into the main body 1 of the apparatus will be explained.

A main control section 49 containing a microcomputer etc. is connected to an operation panel 50. The operation panel 50 is provided on the front panel of the image forming apparatus, and has various operation switches such as a copy switch for copying. Further, the operation panel 50 is connected to a sub-control section 51.

Command information, status information, etc. are exchanged between the sub-control section 51 and the main control section 49.

The sub-control unit 51 is connected to memories 52 and 53 via a pass line.
, an input port 54, and an output port 55. Further, a detection section 13 is connected to the sub-control section 5]. The detection unit 13 detects the size of the paper P conveyed by the rotation of the platen drum 3, and sends the detected size information of the paper P to the sub-control unit 51.

Further, a paper feed sensor 56 for detecting that paper P is fed from the paper feed cassette 15 and a cassette size sensor 57 are connected to the manual boat 54 .

This cassette size sensor 57 is a first output means provided in the paper feed cassette 15, and provides size information related to the size of the paper feed cassette 15 installed in the apparatus main body 1, that is, the paper specified by the paper feed cassette 15. Output size information regarding the size of P. Therefore, the sub-control unit 51
collects paper feed information from the paper feed sensor 56 and size information from the cassette size sensor 57 via the manual boat 54 .

Various motors and solenoids are connected to the drive circuit 64. That is, a cam motor 58 , a feed motor 59 , a platen motor 60 , a ribbon motor 61 , and a pinch roller solenoid 62 are connected to the drive circuit 64 . This drive circuit 64 is connected to the sub-control unit 51 via an output boat 55, and the drive circuit 64 drives a corresponding motor or solenoid based on a control command from the sub-control unit 51.

In addition, the output boat 55 includes a drive circuit 65 and a power supply circuit 67.
is connected. When a control signal for turning on the power supply 67 is sent from the sub-control unit 51 via the output port 55 at the timing of printing, the power supply circuit 67 outputs a predetermined power to the drive circuit 65. The thermal head 5 is connected to the drive circuit 65, and the output boat 55
The thermal head 5 is driven based on a control command from the sub-control unit 51 obtained through the control unit 51 .

Next, the action will be explained.

First, referring to FIG. 3, we will explain what happens when paper smaller than the predetermined size (hereinafter referred to as paper Pa) is mixed into the paper feed cassette 15 for storing paper P of a predetermined size. explain.

As shown in FIG. 3(A), when a copy switch for copying is turned on at time t1, processing for copying is started. When the paper Pa is fed from the paper feed cassette 5, the leading edge of the paper Pa is pinched by the vapor grip 25, and the paper Pa is wound around the platen drum 3. As this platen drum 3 rotates in the direction F1, the paper Pa is conveyed in the direction F1. Paper P
When the leading edge of the paper Pa reaches the detection section 13, the paper Pa is detected for a period T1 from time t3 to time t7, as shown in FIG. 3(B). The size information detected by the detection section 13 is sent to the sub-control section 51. Sub-control unit 5
1, based on the size information from the detection unit 13 as shown in FIG.
Period T1 from time t5 to time t9 as shown in D)
is determined as the period for printing.

On the other hand, the paper feed cassette 15 installed in the apparatus main body 1 is for storing paper P of a specific size, and the size information of the paper P to be stored in the paper feed cassette 15 is detected by the cassette size sensor 57. The signal is supplied to the sub-control unit 51 via the human-powered boat 54. Therefore, the sub-control unit 5
1, as shown in FIG. 3(C), from time t5 to time t based on the size information from the cassette size sensor 57.
The period T2 up to 11 is determined to be the period for printing.

The period T2 for printing determined based on the size information from the cassette size sensor 57 as described above;
If the period T1 for printing determined based on the size information from the detection unit 13 is different from that shown in FIG.
As shown in FIG. 2, the shorter period, that is, the period T1 based on the size information from the detection unit 13, is set as the period for printing. As a result, printing is performed only during the period T1 from time t5 to time t9. Therefore, even if paper Pa smaller than a predetermined size enters the paper feed cassette 15, this paper Pa
Printing is performed appropriately depending on the size of the image.

Next, with reference to FIG. 4, an explanation will be given of the operation when a sheet (hereinafter referred to as sheet pb) larger than the sheet P based on the size information from the cassette size sensor 57 is fed to the platen drum 3. .

When the paper pb conveyed in the direction F1 by the rotation of the platen drum 3 is detected by the detection unit 13, the state shown in FIG.
), the period T from time t23 to time t27
5, paper pb is detected. Based on the size information from the detection unit 13, the time t as shown in FIG.
The period T5 from time t31 to time t31 is determined to be the period for printing. The sub-control unit 51 also controls the size information from the cassette size sensor 57 as shown in FIG.
) The period T from time t25 to time t27 as shown in
6 is determined as the period for printing.

As described above, if the period T6 for printing determined based on the size information from the cassette size sensor 57 and the period T5 for performing printing determined based on the size information from the detection unit 13 are different, The shorter period, that is, the period T6 determined based on the size information from the cassette size sensor 57 as shown in FIG. 4(E), is set as the period for printing.

Therefore, it is possible to reliably prevent printing that exceeds the size of the paper wound around the platen drum 3 and directly onto the platen drum 3.

[Effects of the Invention] As explained above, according to the present invention, the size information output from the first output means and the second output means are compared, and the size information is determined according to the smaller size information. Since the image forming apparatus is configured to perform image formation, it is possible to eliminate the need for a circuit section for detecting an error in the size of the actually fed paper, and the overall circuit configuration can be simplified. Therefore, it is possible to further reduce costs.

Furthermore, since direct image formation on the drum can be reliably prevented, staining of the paper can be prevented, and the quality of image formation can be further improved.

[Brief explanation of drawings]

FIG. 1 is a side view of an image forming apparatus according to the present invention, FIG. 2 is a block diagram of a circuit section incorporated into the image forming apparatus of FIG. 1, and FIG. Figure 4 is a timing chart showing the effect when a smaller paper is fed, and Fig. 4 is a timing chart showing the effect when a paper larger than the size based on the size information from the cassette size sensor is fed. . 3...Platen drum 5...Thermal head 13...Detection section 15...Paper feed cassette 51...Sub-control section 57...Cassette size sensor cutter fr pusher Hidekazu Juzoyoshi

Claims (1)

[Scope of Claims] A supply means for supplying a recording medium; a first output means for outputting size information regarding the size of the recording medium supplied by the supply means; and a recording medium supplied by the supply means. a drum that rotates around the drum, an image forming means that forms an image on a recording medium on the drum, and a second drum that detects the size of the recording medium on the drum and outputs size information of the recording medium. An output means compares the size of the recording medium based on the size information from the first output means and the size of the recording medium based on the size information from the second output means, and determines whichever is smaller. An image forming apparatus comprising: a control means for controlling the image forming means according to information.