JPH09301572A - Paper sheet detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the inside of a device main body from being soiled with toner by detecting that the paper sheet is run out as soon as the last paper sheet is fed regardless of the size of the paper sheet in a paper sheet cassette and eliminating the waste of toner caused by unnecessary image forming. SOLUTION: A paper sheet detecting device is provided with a paper feed roller 3 for taking out a topmost paper sheet 2 stacked in a paper sheet cassette 1, a rotating body 7 to be brought in contact with the back surface of the lowermost paper sheet 2 stacked in the paper sheet cassette 1, and a rotation detecting sensor 10 for detecting the rotation of the rotating body 7 by a skit provided on the rotating body 7, the transmission of light or the shield of light by the slit is detected according to the rotation of the rotating body 7, a continuous pulse from the rotation detecting sensor 10 is detected, and it is detected that the paper sheet is the last one.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper detection device for detecting the exhaustion of paper in a paper cassette such as an electrophotographic device for continuously forming images on paper.

[0002]

2. Description of the Related Art FIG. 6 is a perspective view showing a conventional sheet detecting device disclosed in, for example, Japanese Utility Model Laid-Open No. 6-67444. In the figure, 1 is a paper cassette, 2 is a paper, 3 is a paper feed roller that takes out the paper 2 from the paper cassette 1 and feeds it to an image printing mechanism, and 4 is a light reflection unit including a light emitting unit and a light receiving unit for detecting the paper 2. A sensor 5 is a reflection plate that reflects the light of the light reflection sensor 4 toward the light receiving portion, and a reference roller 6 is a registration roller that temporarily stops the paper 2 for adjusting the paper feed timing.

FIG. 6A shows a state where there is a sheet 2 in the sheet cassette 1, and FIG. 6B shows a state where there is no sheet 2 in the sheet cassette 1.

In the conventional paper detection device, when there is no paper 2 in the paper cassette 1, the light from the light emitting portion of the light reflection sensor 4 is reflected by the reflection plate 5 attached to the bottom of the paper cassette 1. The reflected light is detected by the light receiving portion of the light reflection sensor 4, and it is determined that there is no paper. When the paper 2 is present in the paper cassette 1, the light from the light reflection sensor 4 is blocked by the paper 2, and the reflected light from the reflection plate 5 attached to the bottom of the paper cassette 1 cannot be obtained. Is detected and judged.

In the conventional sheet detecting apparatus of this type configured as described above, the output of the light reflection sensor 4 is constantly monitored to detect the presence or absence of the sheet 2 during the sheet feeding operation. When the rear end of the sheet 2 disappears from the sheet cassette 1 and the light reflection sensor 4 can detect the absence of the sheet, if the light reflection sensor 4 can determine that there is a sheet at that time, the next printing is started.

[0006]

Generally, in the paper conveyance of an electrophotographic printer, a registration roller 6 is used to adjust the timing between a drum or belt on which a toner image is formed and the paper 2 onto which the toner image is transferred. Since the sheet is temporarily stopped and the trailing edge of the sheet 2 remains in the sheet cassette 1 at that time, the conventional sheet detection apparatus as described above detects the presence or absence of the sheet at the time of the temporary stop at the registration roller 6. The timing is too early. By the way, even if the paper presence sensor is arranged at a position where the trailing edge of the paper 2 comes off in consideration of the paper temporarily stopping at the registration roller 6, it is not possible to detect the presence or absence of a plurality of sizes of paper. Therefore, unless a plurality of paper presence / absence sensors are mounted at positions corresponding to all of a plurality of paper sizes, it is impossible to detect the presence / absence of paper when the registration roller 6 is temporarily stopped. In other words, the sheet is again conveyed from the registration roller 6 that has stopped, the trailing edge of the sheet 2 completely comes out of the sheet cassette 1, and the next image formation can be started only at the timing when the presence / absence of the sheet can be reliably detected. Therefore, this waiting time becomes an obstacle to high-speed continuous printing. There is also a method of starting the image formation by ignoring the presence / absence of the paper, but this causes a situation in which the inside of the main body is contaminated by the toner having already started the image formation, and the toner is wasted.

When the paper is a transparent OHP sheet, the light detected by the light reflection sensor passes through the OHP sheet and becomes O.
However, there is a problem that the result of detection of the absence of paper is obtained even though the HP sheet remains.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a paper sheet of any size in a paper cassette at the moment when the last one is fed. An object of the present invention is to provide a paper detection device capable of detecting the absence of paper.

Another object of the present invention is to provide a paper detecting device which can detect a paper jam when the last one paper is fed from a paper cassette and which has a high paper jam occurrence frequency. Especially.

[0010]

According to a first aspect of the present invention, there is provided a sheet detection device in which a sheet feeding roller for taking out the uppermost sheet stacked in a sheet cassette by rotational friction and a sheet stacking roller in the sheet cassette are stored. The rotating body that comes into contact with the back surface of the lowermost sheet that has been rotated, and the rotation of this rotating body are detected, and the last 1
A sheet detection unit that detects that the sheet is fed is provided.

In the paper detecting device according to claim 2 of the present invention, the paper detecting means detects a plurality of slits provided in the rotating body and light transmission and light shielding by the slits according to the rotation of the rotating body. When the number of continuous pulses from the rotation detection sensor reaches a predetermined number or more, it is determined that the last one sheet is fed.

According to a third aspect of the present invention, there is provided a sheet detecting device, which includes an urging means for urging the rotating body into urging contact from the rear surface to the front surface side of the lowermost sheet stacked in the sheet cassette.
The apparatus further comprises a sheet presence / absence detection unit that detects displacement of the position of the rotation shaft of the rotating body when there is no sheet in the sheet cassette.

According to a fourth aspect of the present invention, in the sheet detecting device, the sheet detecting means detects a plurality of slits provided in the rotating body and light transmission and light shielding by the slits according to the rotation of the rotating body. When the continuous pulse interval from the rotation detection sensor is equal to or longer than a predetermined time, the last one sheet is detected to be abnormal.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1. 1 is a side view of a main part of a sheet detection device according to a first embodiment of the present invention, and FIG. 2 is a detailed view of a rotating body portion. In these figures, reference numerals 1 to 4 and 6 are the same as those in the above description of the conventional example. 7 is a paper cassette 1
Is a rotating body that comes into lighter contact with the lowermost sheet 2 from the lower side, and the rotating body 7 is provided with fan-shaped or tear-shaped slits 7a at an equal pitch from the center of rotation. Reference numeral 8 denotes a rotator supporting arm, one end of which is rotatably supported by the paper cassette 1 and the other end of which is rotatably attached to the rotator 7, and the rotator 7 is urged upward by a spring 12. . A bottom plate 9 of the paper cassette 1 is provided with an opening so that the lowermost paper 2 and the rotating body 7 can come into contact with each other. A rotation detection sensor 10 detects the rotation of the rotating body 7, and is attached to the rotating body supporting arm 8. In this embodiment, the rotation detection sensor 10 includes a photodiode 10a and a phototransistor 10 which are arranged to face each other.
b, and the slit 7a of the rotating body 7 is detected between the photodiode 10a and the phototransistor 10b. 1
Reference numeral 1 denotes a conveyance path for guiding the sheet 2 fed from the sheet cassette 1 to the image forming section.

The plurality of slits 7a provided on the rotating body 7 and the rotation detecting sensor 10 for detecting the light transmission and the light blocking by the slits 7a according to the rotation of the rotating body 7 constitute the sheet detecting means of the present invention. To do.

The rotating body 7 is a removable paper cassette 1
It is provided inside and operates normally when the paper cassette 1 is mounted at a predetermined position in the main body of the apparatus. When the paper cassette 1 is attached to the apparatus body, the signal from the rotation detection sensor 10 is taken into the control circuit section of the apparatus body by a connection device (not shown). The rotation detection sensor 10 has a gate-type structure in which a photodiode 10a and a phototransistor 10b are attached to the left and right, and light emitted from the photodiode 10a passes through the slit 7a while the rotating body 7 is rotating and passes through the phototransistor. The phototransistor 10b detects and receives light from the photodiode 10a, and thus, the passage and blocking of light from the photodiode 10a is detected by the phototransistor 10b.

When the phototransistor 10b detects the light from the photodiode 10a passing through the slit 7a of the rotating body 7, the output of the phototransistor 10b becomes "high (H)" level, and when the light is shielded. The output becomes the “low (L)” level, and continuous pulses are output at a frequency proportional to the rotation speed as the rotating body 7 rotates.

Reference numeral 8a denotes a light-shielding plate provided at the movable end of the rotating body supporting arm 8, and 13 denotes a rotating body position detecting sensor for detecting the position of the rotating body 7. This rotating body position detecting sensor 13 is provided in the paper cassette 1. The photodiode 10a and the phototransistor 1 are provided on the left and right sides of the gate-shaped frame attached to the bottom plate 9.
0b, and the light shielding plate 8a is the photodiode 10a.
And the phototransistor 10b can be moved vertically. Then, the photodiode 10a and the phototransistor 1 have a positional relationship such that the output levels are different when the rotating body 7 is in contact with the paper 2 and when the rotating body 7 has disappeared and the rotating body 7 projects from the bottom plate 9.
0b is attached to the paper cassette 1. That is, the photodiode 10a and the phototransistor 10
b means that when the rotating body 7 is in contact with the sheet 2, the light from the photodiode 10a is blocked by the light shielding plate 8a. On the other hand, when the rotating body 7 disappears and the rotating body 7 projects from the bottom plate 9, The light from the diode 10a is arranged so as to reach the phototransistor 10b without being blocked by the light shielding plate 8a.

Further, the rotating body 7 is coaxially arranged in the vicinity of an intermediate portion of the plurality of paper feed rollers 3, and when the paper 2 is present in the paper cassette 1, a spring for biasing the rotating body 7 is provided. The sheet feeding roller 3 prevents the sheet 2 and the rotating body 7 from being lifted by 12.

The operation of the sheet detecting apparatus constructed as above will be described. When a plurality of sheets 2 are stacked in the sheet cassette 1, only the uppermost sheet 2 is fed by the rotation of the sheet feeding roller 3, the lowermost sheet 2 remains, and the rotating body 7 does not rotate. . When the last sheet of paper 2 in the paper cassette 1 is fed, the paper feed roller 3
When the sheet 2 is fed by the rotating body 7, the rotating body 7 that is in contact with one sheet 2 is rotated, and the rotation detection sensor 10 is rotated by the rotating body 7.
The pulsed output corresponding to the rotation speed of is obtained.

When the last sheet of paper 2 is fed and there is no more paper in the paper cassette 1, the rotating body 7
Is moved upward from the opening of the bottom plate 9 by the biasing force of the spring 12. Due to this movement, the light shielding plate 8a moves from a position where the light emitted from the photodiode 10a of the rotating body position detection sensor 13 toward the phototransistor 10b is blocked to a position where it is not blocked, and the phototransistor 10b transmits the light from the photodiode 10a. Receive light,
The output signal is changed from "L" to "H". By detecting the changed output signal, it is detected that the paper 2 is completely absent in the paper cassette 1.

FIG. 3 is a block diagram of the control circuit of the sheet detecting apparatus of the present invention. In the figure, 21 is a microcomputer (CPU) for controlling the apparatus main body, 22 is a memory unit, 2
3 is an image forming unit for forming an image, 24 is a clutch control unit for controlling the conveyance of paper, 25 is a paper feed clutch for controlling the rotation of the paper feed roller 3, 26 is rotation of the registration roller 6,
A resist clutch 27 for stopping is a gate to the interrupt port of the microcomputer 21.

Next, the operation of this circuit will be described. The pulse signal from the rotation detection sensor 10 is input to the interrupt port of the microcomputer 21 via the gate 27,
This pulse signal is calculated by the counter in the microcomputer 21. The gate 27 to the interrupt port is opened only during the paper feeding operation in which the paper feeding clutch 25 is turned on, and the microcomputer 21 performs the interrupt counting.

This sequence flow is shown in FIG. First, the memory section 22 and the interrupt counter of the microcomputer 21 are initialized (steps 31, 32). The paper feed roller 3 is driven to start feeding the paper 2 (step 3
3). At the time of feeding the paper, the number of pulses from the rotation detection sensor 10 is counted (step 34), and if the rotation of the rotating body 7 is not detected (in consideration of erroneous pulse generation due to vibration, less than 10 pulses). If it is not detected, it is determined that it is not the last sheet feeding of the sheet cassette 1, and the image forming unit 23 is turned on to execute image forming printing (step 37) (step 36).

When the interrupt counter detects 10 pulses or more (step 35), it is determined that the last sheet has been fed, and the memory section 22 is made to hold the information indicating the end of printing (step 38). Memory unit 22 after printing one sheet
According to the print end information, the image forming unit 23 is turned off and the end operation is started (step 39). Then, a BUSY signal indicating that the activation command for the next print cannot be accepted is output to the host computer that transfers the print data (step 40). In this way, at the time when the printing currently in progress using the last sheet of paper 2 is completed, it can be detected that there is no next printing paper, so the printing end processing such as cleaning of the apparatus main body is executed. Thus, the printing operation can be stopped, waste of toner due to unnecessary image formation is eliminated, and the inside of the apparatus main body can be prevented from being contaminated by this toner.

Embodiment 2 FIG. The above-described paper presence / absence detection can detect that the paper 2 has been consumed and the paper has run out in the paper cassette 1 by the printing operation, but when the power of the electrophotographic printer is turned on, the paper in the paper cassette 1 is detected. It is impossible to determine the presence or absence of 2. Therefore, when the last user has used up the last sheet of paper 2 in the paper cassette 1, when the next user turns on the power,
The printing operation is executed even though there is no paper.

The invention of the second embodiment improves such a situation. Immediately after the power is turned on, the state of the rotating body position detecting sensor 13 is recognized by the microcomputer 21, and if the output of the rotating body position detecting sensor 13 is, for example, “H” level, the rotating body 7 contacts the paper 2. If there is no sheet 2 in the sheet cassette 1 above the position and the level is “L”, the rotating body 7 is set to the sheet 2
It is determined to be in the contact position with. Therefore, it is possible to detect the presence / absence of the paper inside the paper cassette 1 during the initialization of the apparatus main body before the paper feeding operation or in the standby state.

Embodiment 3. As shown in the first embodiment, the paper feed roller 3 feeds paper from the paper cassette 1 by friction between the paper feed roller 3 and the paper 2. Therefore, when the last one sheet is fed from the sheet cassette 1, the frictional force acting on the sheet 2 is smaller than that in the normal case, and thus the probability of jam occurrence is high. Therefore, by detecting the rotation status of the rotating body 7, it is determined whether or not the feeding of the last one sheet from the sheet cassette 1 has been normally executed.

When a paper jam occurs, the paper 2 is caught by something and cannot be fed at a normal speed. Therefore, the rotation speed of the rotating body 7 slows or stops. Optical sensor for rotation detection 10
The pulse signal from is input to the interrupt port of the microcomputer unit 21, and the pulse time interval is calculated by the timer of the microcomputer unit 21. The gate 20 to the interrupt port is opened only during the paper feeding operation in which the paper feeding clutch 25 is turned on, and the pulse time interval is measured in the microcomputer unit 21. This pulse time interval measurement is a predetermined number of pulses (eg 10 pulses)
If the average value of is used, the measurement error is reduced, and it is possible to accurately determine whether or not a paper jam has occurred. In addition, the rotation detection sensor 1
Even when a predetermined number of pulses (for example, 10 pulses) are not counted within a predetermined time from the first detection level change of 0, it is processed as a paper feed abnormality.

This sequence flow is shown in FIG. In this figure, steps 32, 33, 39 and 40 are the same as those described in the second embodiment. The slit 7a of the rotating body 7 is located at either position where the rotation detection sensor 10 detects light transmission or light blocking. Measuring the elapsed time from the time when the detection level of the rotation detection sensor 10 changes,
The counting of the number of pulses from the rotation detection sensor 10 is started (steps 41 and 42). When there are a plurality of sheets 2 in the sheet cassette 1, the rotation detecting sensor 10 does not output a pulse, or the rotating body 7 detects that the entire stacked sheets have slightly moved, and at most 1-2 pulses are generated. It is only output. Therefore, it takes a predetermined time (for example, 0.1 to 0.3) from the change in the detection level of the rotation detection sensor 10.
Second) is not detected, it means that if the uppermost paper of multiple sheets is fed normally,
Or, it occurs when the last sheet of paper jams after moving by a distance for outputting several pulses and then becomes stuck. This check is performed in steps 43 and 44. In step 44, if the number of pulses detected within the predetermined time is 2 or less, normal paper feeding is performed, and if 3 or more, it is considered as a paper feeding abnormality and paper jam abnormality processing (step 45) is performed.

The average pulse interval of a predetermined number of pulses (for example, 10 pulses) is calculated from the elapsed time when the predetermined number of detected pulses (10 in this case) is counted within the predetermined time (step 46). ). The average pulse interval is inversely proportional to the sheet feeding speed. When the average pulse interval is equal to or longer than the predetermined interval, the sheet feeding speed is slower than normal and it is determined that the sheet is abnormal, and the sheet jam abnormality process (step 45) is executed. If the paper feeding speed is normal, the printing is performed on the last sheet of paper and the process proceeds to the stop process. In this way, when the last sheet of paper stops halfway, it is detected and the image forming operation is immediately stopped, so that the waste of toner due to unnecessary image formation is eliminated, and It is possible to prevent the inside of the main body of the device from being soiled.

[0032]

According to the first aspect of the present invention, there is provided a sheet detecting device which takes out the uppermost sheet stacked in the sheet cassette by rotational friction, and the lowermost sheet which is stacked and accommodated in the sheet cassette. In the case of a transparent OHP sheet, a rotating body that comes into contact with the back surface of the sheet and a sheet detecting unit that detects the rotation of the rotating body to detect the feeding of the last sheet of paper are provided. However, even if the size of the paper in which the trailing edge of the paper remains in the paper cassette due to the paper being temporarily stopped by the registration rollers during paper feeding, regardless of the type and size of the paper, It can be detected that the sheet is the last sheet by the presence or absence of rotation of the rotating body that is brought into contact with the back surface of the lower sheet, and the waste of toner due to unnecessary image formation can be eliminated and the inside of the apparatus main body can be prevented from being contaminated by toner.

According to a second aspect of the present invention, in the sheet detecting device, the sheet detecting means makes a plurality of slits provided in the rotating body, and transmits and shields light by the slits according to the rotation of the rotating body. With a rotation detection sensor to detect,
When the number of continuous pulses due to the light transmission and the light shielding exceeds a predetermined number, it is determined that the last one sheet is fed, so that the last sheet can be detected more reliably. .

According to a third aspect of the present invention, there is provided a sheet detecting device, which comprises an urging means for urging the rotating body into urging contact from the rear surface to the front surface side of the lowermost sheet stacked in the sheet cassette.
Since the sheet cassette is provided with the sheet presence / absence detecting unit that detects the displacement of the position of the rotation shaft of the rotating body when there is no sheet in the sheet cassette, it is possible to detect the last sheet with a simple configuration.

According to a fourth aspect of the present invention, in the sheet detecting device, the sheet detecting means makes a plurality of slits provided in the rotating body, and transmits and shields light by the slits according to the rotation of the rotating body. With a rotation detection sensor to detect,
When the pulse interval due to the light transmission and the light shielding exceeds a predetermined time, it is determined that the last one sheet is abnormally fed, so when the last one sheet is fed. By recognizing the sheet feeding speed of, it is possible to reliably detect the occurrence of a sheet jam of this sheet.

[Brief description of drawings]

FIG. 1 is a side view of essential parts of a sheet detection device according to a first embodiment of the present invention.

FIG. 2 is a layout view of a rotating body showing the first embodiment of the present invention.

FIG. 3 is a diagram showing a control circuit configuration of the sheet detection device of the invention.

FIG. 4 is a diagram showing a sequence flow according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a sequence flow according to the third embodiment of the present invention.

FIG. 6 is a structural diagram showing a sheet detection device of a conventional sheet cassette.

[Explanation of symbols]

1 paper cassette, 2 paper, 3 paper feed roller, 6 registration roller, 7 rotating body, 7a slit, 8 rotating body supporting arm, 8a light shielding plate, 9 paper cassette bottom plate, 10
Rotation detection sensor, 12 springs, 13 rotating body position detection sensor, 21 microcomputer, 22 memory unit,
23 image forming unit, 24 clutch control unit, 25 paper feeding clutch, 26 registration clutch, 27 gates.

Claims (4)

[Claims] 1. A paper feed roller for taking out the uppermost paper stacked in a paper cassette by rotational friction, a rotating body that comes into contact with the back surface of the lowermost paper stacked and accommodated in the paper cassette, and this rotation. A sheet detection device comprising: a sheet detection unit that detects the rotation of the body and detects that the sheet is the last one. 2. The sheet detecting means includes a plurality of slits provided in the rotating body, and a rotation detecting sensor for detecting light transmission and light shielding by the slits according to the rotation of the rotating body. 2. The sheet detecting apparatus according to claim 1, wherein when the number of continuous pulses of light and light blocking exceeds a predetermined number, it is determined that the last one sheet is fed. 3. An urging means for urging and contacting the rotating body from the back surface to the front surface side of the lowermost sheet stacked in the paper cassette; and a rotation shaft of the rotating body when there is no paper in the paper cassette. 3. The sheet detecting apparatus according to claim 1, further comprising a sheet presence / absence detecting unit that detects the displacement of the position of the sheet. 4. The sheet detecting means includes a plurality of slits provided in the rotating body, and a rotation detecting sensor for detecting light transmission and light blocking by the slits according to the rotation of the rotating body. 2. The sheet detecting apparatus according to claim 1, wherein when the pulse interval due to the light and the light blocking exceeds a predetermined time, it is determined that the last one sheet is an abnormal sheet.