JP2524652B2 - Paper size detector for laser printer - Google Patents

Description

The present invention relates to a paper size detection device for a laser printer.

[Prior Art] A laser printer, for example, charges a photoconductor of a photoconductor drum by a charging unit and then records information on the photoconductor by a laser beam from a laser scanner unit as an electrostatic latent image. Toner is attached to the developing section to make it visible. On the other hand, a sheet is fed from a sheet feeding section provided with a sheet feeding cassette to a conveyance path, is conveyed to a transfer section through the conveyance path, and the toner image visualized in the transfer section is transferred from the photoconductor to the sheet. It is like this. Then, the sheet after the transfer is fixed by a fixing device and then discharged.

In such a laser printer, the size of the conveyed paper is detected to inform the operator.
Therefore, conventionally, a feed sensor was provided in the middle of the transport path,
A microprocessor that configures the main body of the control unit that controls the photosensitive drum, the laser scanner unit, the charging unit, the developing unit, the transfer unit, the transport unit, and the like while the paper sent from the paper feed unit to the transport path passes through the feed sensor. A timer was installed in the system to manage it with software, and the paper size was determined from the relationship between the transit time and the transport speed.

[Problems to be Solved by the Invention] However, if the microprocessor manages the determination of the sheet size by counting the time with a timer, there is a problem that the software load on the microprocessor becomes large.

Therefore, the present invention can reduce the software load of the microprocessor in the case of determining the size of the conveyed paper by the microprocessor controlling each mechanism such as the laser scanner unit and the conveying unit, and thus the performance of the microprocessor is low. An object of the present invention is to provide a paper size detection device for a laser printer that can be used.

[Means for Solving the Problems] According to the present invention, a photoconductor is charged, and the charged photoconductor is irradiated with a laser beam from a laser scanner unit to form an electrostatic latent image. In a laser printer that develops and visualizes and then transfers and prints on the conveyed paper, the ON signal of the laser scanner is input and the vertical synchronization signal for scanning the laser beam from the laser scanner unit is input. The laser scanner control circuit that generates, the feed sensor that detects the paper passing through the predetermined position of the conveyance path, the clear state is released by the ON signal of the laser scanner, and the vertical synchronization is performed in response to the paper detection signal from the feed sensor. A vertical sync counter that starts signal counting and stops the vertical sync signal counting in response to the paper non-detection signal from the feed sensor. Unta,
A microprocessor is provided to judge the size of the conveyed sheet based on the count value of the vertical synchronization counter after the sheet has passed through the feed sensor.

[Operation] In the present invention, the vertical synchronization counter starts counting the vertical synchronization signal when the paper conveyed on the conveyance path is detected by the feed sensor, and when the paper passes the feed sensor, the vertical synchronization counter outputs the vertical synchronization signal. Stop counting. After the paper has passed through the feed sensor, the microprocessor reads the count value of the vertical synchronization counter and determines the paper size.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, a photosensitive drum 12 whose surface is made of a photoconductive substance is arranged at a substantially central portion in the housing 11.
The photosensitive drum 12 is driven to rotate in one direction, that is, in the clockwise direction in the figure by a feed motor 13 including a stepping motor.
12 around the photoconductor drum 12 according to the electrophotographic process
Charging unit 14 for charging the photoconductor, and a laser scanner unit 1 for irradiating the photoconductor charged by the charging unit 14 with a laser beam to record and record information to form an electrostatic latent image.
5, developing unit 16 for adhering toner, which is a developer, to the electrostatic latent image formed on the photoconductor, photoconductor drum for the fed paper
Transfer unit 17 for transferring the toner image from 12, cleaning device 1 for removing the residual toner from the transferred photoconductor drum 12
8. A static eliminator 19 for static erasing the transferred photoconductor drum 12 is arranged in order.

A paper feed unit 20 is provided on one side of the housing 11, and the paper feed unit 20 includes a paper feed roller 22 and a paper feed roller 22 that can freely contact and separate from the upper surface of the paper 21 stored therein. A sheet feeding solenoid 23 for performing a contact / separation operation is provided.

The paper feed solenoid 22 causes the paper feed roller 22 in a rotating state to contact the paper 21 for a predetermined time, so that the paper 21 is fed from the paper feed unit 20 one by one at a predetermined timing, and the fed paper 21 is conveyed. It is adapted to be conveyed to the position of the transfer portion 17 through a conveying path 24 provided with rollers (not shown). A feed sensor 25 is provided in the middle of the transport path 24.

The sheet 21 on which the toner image has been transferred from the photosensitive drum 12 in the transfer unit 17 is supplied to a heat fixing unit 26, and after being heat-fixed in the heat fixing unit 26, is discharged by the discharge roller 27 to the other side of the housing 11 The paper is discharged from the housing through a paper discharge port 28 provided in the printer.

FIG. 2 is a block diagram showing a circuit configuration. Reference numeral 31 denotes a microprocessor constituting a control unit main body, and 32 denotes an input / output port, which are connected by a bus line 33.

The input / output port 32 includes a feed solenoid driving circuit 34 for driving the feed solenoid 23, the feed motor
Motor drive circuit 35 for driving 13, charging unit 14, transfer unit
A high-voltage power supply 36 for supplying a high voltage to 17, a fixing heater 37 of the thermal fixing unit 26, an operation unit 38 provided with a start key and a print number setting key, a mode counter circuit 39, a vertical synchronization counter 40, the feed sensor. A sensor circuit 42 for controlling various sensors 41 including 25, and a laser scanner control circuit 44 for controlling an image data generation circuit 43 for supplying image data to the laser scanner unit 15 are connected respectively.

FIG. 3 shows a main part configuration. The mode counter circuit 39 comprises a mode counter 45, a one-shot timer 46 and a rising / falling detection circuit 47, and the sensor circuit 42.
From the feed sensor 25 is supplied to the rising / falling detection circuit 47 and a signal FSO indicating whether or not the feed sensor 25 is detecting the passage of the paper 21, and is also supplied to the enable terminal EN of the vertical synchronization counter 40. . The signal FSO is at a high level when the feed sensor 25 does not detect the sheet 21, and is inverted to a low level when the feed sensor 25 detects the sheet 21.

From the I / O port 32 to the laser scanner control circuit 44
ON / OFF signal ST1 / STOP for laser scanner is supplied to enable terminal EN1 of
STOP is also supplied to the clear terminals (low active) CL of the mode counter 45 and the vertical synchronization counter 40.

The laser scanner control circuit 44 supplies a vertical synchronizing signal VSYO for scanning operation of the laser scanner unit 15 to the image data generating circuit 43 when an ON signal for the laser scanner is input from the I / O port 32. At the same time, it is supplied to the input terminal CK of the vertical synchronization counter 40.

The vertical sync counter 40 receives the input vertical sync signal VS.
It counts the number of YO and supplies the count value CD to the I / O port 32.

The mode counter circuit 45 detects the rising and falling of the signal FSO from the sensor circuit 42 by the rising / falling detection circuit 4
7 and supplies the detection signal to the one-shot timer 46. The one-shot timer circuit 46 converts the detection signal into a pulse signal MCK1 having a sufficient width and supplies it to the mode counter 45. This mode counter 45 has a pulse signal MC
The number of K1 inputs is counted, and the count value is used as the mode value MD.
To the I / O port 32.

In the present embodiment having such a configuration, since the laser scanner on / off signal ST1 / STOP from the I / O port 32 is an off signal at a low level in the state before printing is started, the mode counter 45 And the vertical sync counter 40 is in the clear state. Therefore, the count value of the mode counter 45 is “0”, that is, the mode value MD supplied to the I / O port 32.
Is "0".

When the start key is operated to start printing in this state, the microprocessor 31 drives the motor drive circuit 35 via the I / O port 32.

In this way, the feed motor 13 is rotationally driven, whereby the photoconductor drum 12, the transport roller, the paper feed roller 22 and the like are rotated.

Further, the microprocessor 31 turns the laser scanner ON / OFF signal ST1 / STOP into a high level ON signal through the I / O port 32 as shown in FIG. As a result, the clear states of the mode counter 45 and the vertical synchronization counter 40 are released, and the laser scanner control circuit 44 operates to supply the vertical synchronization signal VSYO as shown in FIG. 4 (e) to the image data generation circuit 43. To do. In this way, image data is supplied from the image data generation circuit 43 to the laser skinner unit 15, and the laser scanner unit 15 drives a polygon motor or the like to scan the laser beam on the photoconductor of the photoconductor drum 12 charged by the charging unit 14. Then, the image data is recorded as an electrostatic latent image.

Further, the microprocessor 31 controls the paper feed solenoid drive circuit 34 via the I / O port 32 to operate the paper feed solenoid 23 for a predetermined time. As a result, the paper feed roller 22 is sucked for a certain period of time and comes into contact with the upper surface of the paper 21. In this way, the paper 21 is fed from the paper feed unit 20 to the primary transport path 24.

When the feed sensor 25 detects the paper 21 passing through the transport path 24, the signal FSO from the sensor circuit 42 falls from the high level to the low level as shown in FIG. 4 (b). The fall of this signal FSO is the rise / fall detection circuit 47.
Detected in. Then, the detection signal from the rising / falling detection circuit 7 is supplied to the one-shot timer 46, which converts it into a pulse signal MCK1 having a sufficient width as shown in FIG. Supplied. As a result, the mode counter 45 counts up by 1 and outputs the mode value MD "1" as shown in FIG. 4 (d).

When the signal FSO falls from the high level to the low level, the vertical sync counter 40 is enabled and the vertical sync signal VSYO output from the laser scanner control circuit 44 is counted as shown in FIG. 4 (f). . Then, the vertical synchronization counter 40 changes the count value to the count value.
It is supplied to the I / O port 32 as a CD.

Thereafter, when the sheet 21 passes through the feed sensor 25, the signal FSO from the sensor circuit 42 rises from a low level to a high level. The rise of this signal FSO is detected by the rise / fall detection circuit 4.
Detected at 7. Then, the detection signal from the rising / falling detection circuit 47 is supplied to the one-shot timer 46, converted into the pulse signal MCK1 having a sufficient width by the one-shot timer 46, and supplied to the mode counter 45. As a result, the mode counter 45 counts up by 1 and outputs the mode value MD "2".

When the signal FSO rises from the low level to the high level, the enable state of the vertical sync counter 40 is released and the vertical sync counter 40 stops the counting operation of the vertical sync signal.

In this way, the count value CD output from the vertical synchronization counter 40 to the I / O port 32 is fixed.

Then, the microprocessor 31 may read the count value CD from the vertical synchronization counter 40 when the mode value MD from the mode counter 45 is "2". Then, by comparing the count value CD with a numerical range corresponding to a preset paper size, it is possible to determine what size the transport paper is.

The paper 21 that has passed through the feed sensor 25 is then transferred to the transfer unit 17.
After being transferred and thermally fixed by the heat fixing unit 26, the sheet is discharged from the paper discharge port 28 to the outside of the housing by the discharge roller 27.

Then, when the laser scanner ON / OFF signal ST1 / STOP from the I / O port 32 becomes an OFF signal, that is, a low level, the control of the laser scanner unit 15 by the laser scanner control circuit 44 is stopped and the mode counter 45 and vertical synchronization are performed. Counter 40 is cleared, mode counter 45
The mode value of is 0.

Therefore, by reading the mode value MD from the mode counter 45 via the I / O port 32, the microprocessor 31 can easily know what kind of conveyance state the paper 21 is currently in. When the mode value MD from the mode counter 45 is "2", the count value CD from the vertical synchronization counter 40
By reading, the paper size can be determined.

That is, as shown in FIG. 5, if the mode value MD is "0", the microprocessor 31 determines whether or not it is a state in which sheet feeding is subsequently started. That is, it is determined that the paper feed roller 22, the transport roller, and the polygon motor in the laser scanner unit 15 have started to start feeding. If the sheet feeding is not started, the operation state (D), that is, the state in which the sheet is not conveyed at all, is determined.

If the mode value MD is "1", the operation state (B), that is, the state where the feed sensor 25 detects that the paper 21 is passing and the paper conveyance control is continued is determined.

When the mode value MD is "2", it is determined that the operation state (C), that is, the sheet 21 has passed the feed sensor 25 and the count value CD of the vertical synchronization counter 40 has been read.

Then, when the count value CD is read, it is checked whether the step value is the range of the sheet 1, the range of the sheet 2, ... If there is a corresponding range, the paper size corresponding to the range is determined.

If it does not fall within any of the ranges, an error is detected as a paper size detection failure.

In this way, the microprocessor 31 simply reads the mode value MD of the mode counter 45 via the I / O port 32, and when the mode value MD is "2", the vertical synchronization counter 40
The size of the paper 21 can be determined by reading the count value CD from the feed sensor 25.
It is not necessary for the software to operate the internal timer to manage the time while detecting the conveyance of the paper 21. Therefore, the software load on the microprocessor 31 can be reduced.

Therefore, the microprocessor 31 can sufficiently deal with the fact that the conveyance speed of the paper is increased for high-speed printing.

Even if the microprocessor is switched from the 8-bit type to the 4-bit type, it can be controlled sufficiently. That is, it is possible to use a microprocessor with low performance.

[Effects of the Invention] As described in detail above, according to the present invention, in the case where the size of the conveyed paper is judged by the microprocessor controlling each mechanism such as the laser scanner unit and the conveyor, the software of the microprocessor is used. Therefore, it is possible to provide a paper size detection device for a laser printer which can reduce the load and can therefore use a low performance microprocessor.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention. FIG. 1 is a schematic configuration diagram, FIG. 2 is an overall block diagram, FIG. 3 is a block diagram of main parts, and FIG. 4 is an operation of each part in FIG. FIG. 5 is a timing chart showing the timing, and FIG. 5 is a flow chart showing the state judgment processing at the time of sheet conveyance by the microprocessor. 15 …… Laser scanner unit, 21 …… Paper, 25 …… Feed sensor, 31 …… Microprocessor, 39 …… Mode counter circuit, 40 …… Vertical synchronization counter. 44 …… Laser scanner control circuit.

Claims (1)

(57) [Claims] 1. A photosensitive member is charged, and the charged photosensitive member is irradiated with a laser beam from a laser scanner unit to form an electrostatic latent image, and the electrostatic latent image is developed and visualized. In a laser printer that transfers and prints on a conveyed sheet, a laser scanner control circuit that receives a turn-on signal of a laser scanner and generates a vertical synchronization signal for performing a scanning operation of a laser beam from the laser scanner unit. , A clear state is released by an ON signal of the feed sensor and the laser scanner that detects the sheet passing a predetermined position of the conveyance path, and the vertical synchronization signal is counted in response to the sheet detection signal from the feed sensor. A vertical synchronization cow that starts and stops counting of the vertical synchronization signal in response to a paper non-detection signal from the feed sensor. Data and the paper size detecting device of the laser printer, characterized in that a microprocessor for determining the size of the sheet conveyed by the count value of the vertical synchronization counter at the feed sensor after passing the paper.