JPH05281874A - Recording paper discriminating device - Google Patents

Abstract

PURPOSE:To provide a recording paper discriminating means preventing the degradation of an image by automatically sorting a plain paper and a carton or an envelope, and processing. CONSTITUTION:A motor driving current detecting circuit 53 detects the driving current of a motor, the detected motor driving current is read every recording paper, and compared with a value set by a CPU 32 in advance, and when it is decided that the recording paper is the envelope or the carton, the CPU 32 controls a transfer current control circuit 47 to increase a transfer current, or a fixing temperature control circuit 49 to rise a fixing temperature, or a fixing roller driving circuit 50 to reduce fixing speed, or executes a plural of fixing times, or so, to prevent the degradation of the image.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording paper discriminating apparatus in an image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, a means for heating and fixing an unfixed toner image formed on a recording sheet, a means for recording a plurality of times on the same recording sheet, and a recording sheet housed in a sheet feeding device. When a specific size is detected by the size detecting unit, the fixing unit heats the same recording paper a plurality of times by causing the fixing unit to perform a plurality of recording operations. Then, there is an image forming apparatus for fixing. However, in this apparatus, the size detection plate of the recording paper is changed for each paper type in the paper feed tray, and the sensor reads this.

[0003]

However, in the above-described conventional image forming apparatus, it is difficult to distinguish between plain paper and thick paper, or envelope-sized plain paper and envelope, because only the size of the recording paper is detected. There was a problem that. The present invention solves the above-mentioned conventional problems by automatically distinguishing between plain paper and thick paper and envelopes, and by improving the transfer rate and fixing rate of the determined thick paper and envelope. It is an object of the present invention to provide a recording paper discriminating apparatus that prevents deterioration of the recording paper.

[0004]

In order to achieve the above object, a recording paper discriminating apparatus of the present invention comprises a drive current detecting means for detecting a drive current of a motor, and a detected drive current for each recording paper. It has a means for judging that the recording paper is an envelope or a thick paper by comparing with a preset value.
Further, the difference between the torque before the paper feeding and the torque during the paper feeding is taken, and thereby the paper type is accurately determined. Further, a transfer current control means and a fixing temperature control means are provided, and the transfer current and the fixing temperature are controlled depending on the type of paper (envelope, thick paper, etc.).

[0005]

Therefore, according to the present invention, plain paper, cardboard, and envelope can be automatically and accurately distinguished from each other even if they are of the same size, and image deterioration of cardboard, envelope, etc. can be prevented.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an image forming apparatus or printer to which an embodiment of the present invention is applied. The outline of the operation of the printer is as shown in FIG.
Then, it is conveyed to the latent image carrier composed of the photoconductor 4 on the drum at a timing. The photoconductor 4 is driven to rotate counterclockwise, the surface of the photoconductor 4 is charged by the charging charger 5, and a laser beam from the laser optical system 6 is irradiated to form an electrostatic latent image on the photoconductor. This latent image is visualized by toner as it passes through the developing device 7. This visible image is transferred to the recording paper 2 conveyed to the photoconductor 4 by the transfer charger 8 and the transferred visible image on the recording paper. Is fixed by the fixing device 9, and is discharged and stored in the paper discharge unit 11. On the other hand, the residual toner is removed from the photoconductor 4 after the transfer of the visible image by a cleaning device having a cleaning blade 12. The toner removed from the photoconductor is collected and stored in the toner collecting tank 13. FIG. 2 is a block diagram showing a configuration example of a laser printer to which an embodiment of the present invention is applied. In FIG. 2, 30 is connected to an external device,
A controller that sends image information to the recording device, 31
Is an external device such as a host computer, 32 is a CPU in the form of a microcomputer for controlling the recording device, and has a random access memory (RAM) for work. 33 is C
Read-only memory (R
OM), 34 is a main motor 3 for carrying a recording medium such as paper.
Main motor drive circuit for driving 5, 36 for paper feed clutch 3
A feeding clutch drive circuit for driving 7, a registration clutch drive circuit for driving the registration clutch 39, and a polygon motor drive circuit for driving a polygon motor 41, which are detections for detecting the number of revolutions of the polygon motor 41. It has a circuit. Reference numeral 42 denotes a laser device, which has a semiconductor laser unit that outputs a laser beam according to the driving of a laser drive circuit, and a light receiving element that is provided for adjusting the light amount. 43 is an image signal (WDATA) from the controller 30
A laser drive circuit for driving the laser device 42 by an image signal (VIDEO) generated from
45 is a main scanning synchronization signal from the synchronization detection signal (DETP) obtained by the synchronization detector 44 according to the rotation of the polygon motor 41.
(LSYNC), main scanning write effective area signal (LGATE), sub-scanning writing effective area signal (FGATE)
An optical writing control unit for sending to 30. The CPU 32 and the controller 30 are connected by a bidirectional serial interface composed of a reception data signal (PERXD), a transmission data signal (PETXD), a reception ready signal (PEDTR), and a transmission ready signal (PECTS), and the state of the recording device judged by the CPU 32 To the controller 30, or the controller 30 sends a command to control the recording device.

In such a configuration, the CPU 32 informs the controller 30 that the recording apparatus is in a recording operation ready state. The controller 30 confirms that the recording operation is possible and sends a recording operation start command to the CPU 32. CP
When U32 receives the recording operation start signal, it immediately starts the recording operation and turns on the polygon motor drive signal (PMST) to rotate the polygon motor 41. Polygon motor 41
Outputs an FG pulse with a frequency corresponding to the rotation speed, this pulse is detected by the FG signal detection circuit and sent to the polygon motor drive circuit, and the polygon motor reference clock (PM
The rotation speed of the polygon motor is controlled so that it has the same frequency as CK). At the same time, the main motor drive signal (MM
(ST) is turned on and the main motor 35 is rotated. The controller 30 receives the recording density information input according to the switch operation of the external device or the operator depending on the image content, regardless of the recording operation, and transmits the recording density designation command to the CPU 32. In response to this, the CPU 32 sends a rotation speed control signal (PMCON) to the polygon motor drive circuit 40. The rotation speed control signal (PMCON) is a signal that determines the polygon motor reference clock (PMCK) and is either the reference clock itself or one of the plurality of clocks provided in the polygon motor drive circuit 40 as the reference clock. This is the signal to select. The polygon motor drive circuit 40 can stabilize the rotation of the polygon motor 41 by controlling the current to the polygon motor 41 so that the cycle of the FG pulse becomes a constant level. Therefore, the CPU 32 can switch the rotation speed of the polygon motor 41 according to the specified print density by switching the rotation speed control signal (PMCON) after receiving the print density specifying command. Also, the polygon motor drive circuit 40
When the polygon motor 41 reaches a steady rotational speed according to the recording density, turns on the polygon motor lock signal (PMLK) and sends it to the CPU 32. When the recording operation is started, the CPU 32 turns on the paper feed clutch drive signal (FDCL), drives the paper feed clutch 37, and conveys the recording medium stored in the cassette or the like to the registration roller position. After confirming that the polygon motor lock signal (PMLK) is turned on, the sub-scanning writing effective area signal (FGATE) is sent to the controller 30. The controller 30 sends the image signal (WDATA) after a predetermined time in synchronization with turning on of the sub-scanning writing effective area signal (FGATE). CPU
32, FGATE is sent out, and after a predetermined time, the registration clutch drive signal (RGCL) is turned on, the recording medium is conveyed toward the recording position by the photosensitive drum or the like, and an image is formed at the predetermined position of the recording medium. The CPU 32 adjusts the laser light amount when the FGATE signal is off. The light amount signal fed back from the receiving element of the laser device 42 is compared with a predetermined level by a comparator in the laser driving circuit, and is input to the CPU 32 as a binarized LDCT signal. CP
U32 changes the laser drive signal by using digital-analog conversion, holds the laser light amount at the point where the laser light amount reaches a predetermined value and the LDCT signal changes, and adjusts the laser light amount. Further, by irradiating the mirror on the rotating polygon motor 41 with the laser, the synchronization detector 44
Detects a synchronization signal of a constant cycle according to the rotation of the polygon motor. The optical writing control unit 45 inputs the synchronization detection signal (DETP), and the image writing clock synchronized with the DETP signal.
(WCLK) is generated. At the same time, the WCLK signal is counted, and when the predetermined count is reached, the main scanning synchronization signal (LS
YNC) and main scanning write effective area signal (LGATE). In addition, the sub scan writing effective area internal signal from the CPU 32
(FSYNC) is input and the sub-scanning write effective area signal (FGATE) is generated in synchronization with the FSYNC signal. LGAT
When writing an image with the E and FGATE signals turned on, the image signal (WDA
TA) is fetched in synchronization with the WCLK signal, converted into an image signal (VIDEO) for driving the laser device 42, and transmitted to the laser drive circuit 43. The size detection switch notifies the CPU of the type of recording paper to be printed. The details are shown in FIG. In FIG. 3, the paper feed cassette 54 is used by attaching a size detection plate 56 that matches the paper size, but a size detection switch 55 is provided on the paper feed main body side corresponding to the position of the size detection plate to detect the size. The CPU 32 is notified of a signal corresponding to the cutout of the plate. The motor drive current detection circuit 53 converts the drive current of the main motor into a voltage and further A / D converts it to notify the CPU 32 of the current value. A circuit diagram of the motor drive current detection circuit 53 is shown in FIG. The CPU reads the current value of the current value when the paper feed clutch 37 is not turned on and the current value when the paper feed clutch 37 is turned on, and uses this difference as the motor torque required for paper feeding, and the normal paper and thick paper ( Or the torque threshold value with (envelope) (If it is larger than this value, it is regarded as thick paper, if it is smaller, it is regarded as plain paper), and the recording paper currently being fed is thick paper (or envelope)
Is determined. The transfer current control circuit 47 turns on / off the current of the transfer charger 48 according to a signal from the CPU 32.
Or UP, DOWN. The fixing temperature control circuit 49 controls the temperature of the fixing device 9 (FIG. 1) to be UP or DO by a signal from the CPU 32.
WN Further, the fixing roller drive circuit 50 changes the speed of the fixing roller 51 in the fixing device 9 to UP, D by the signal of the CPU.
OWN or rotate the roller forward or backward. The CPU 32, which detects the thick paper (or envelope), transfers the transfer current control circuit 47.
The signal of the transfer current UP is sent to and the current of the transfer charger is increased. Further, a fixing temperature UP signal is sent to the fixing temperature control circuit 49 to increase the temperature of the fixing device. Further, a signal of the fixing roller drive speed DOWN is sent to the fixing roller drive control circuit 50 to make the drive speed of the fixing roller DOWN. Further, when the thick paper (or the envelope) passes through the fixing device, the fixing roller reverse rotation signal is sent to the fixing device fixing roller drive circuit 50 to reversely rotate the fixing roller, and the thick paper (or
The envelope) is returned to the front of the fixing device, the fixing roller is again rotated in the forward direction, and the envelope is passed through the fixing device a plurality of times. 5 to 8 show a flow chart of an embodiment of the present invention.
5 to 8, if there is a print request
(S ₁ ) The main motor 35 is driven (S ₂ ) and the motor drive current at this time is sent to the CPU 32 (S ₃ ). When paper feeding starts (S
₄ ) The motor drive current at this time is sent to the CPU 32 (S ₅ ). Two
The difference between the two current values is compared with a threshold value for judging thick paper (or envelope) (S ₆ ), and if the difference is small, it is regarded as plain paper and a series of printing operations are performed (S ₇ ). If the difference is large, it is considered as thick paper or envelope, and the transfer current is increased in FIG. 5 (S ₈ ).
Then, a series of printing operations are performed (S ₉ ). In the case of FIG. 6, a series of printing operations with up the fixing temperature _{(S 10) (S 11)} . In the case of FIG. 7, the fixing speed is reduced (S ₁₂ ).
Performing a series of print operations and (S _13). Further, in the case of FIG. 8, the cardboard or the envelope is switched back after passing through the fixing device and passed through the fixing device a plurality of times (S ₁₄ , S ₁₅ ,
S ₁₆ , S ₁₇ ).

[0008]

As is apparent from the above embodiment, the present invention automatically distinguishes plain paper from cardboard and envelopes even if the paper size is the same. Further, even if the torque of the motor changes due to deterioration of the motor or increase of other load, the type of paper can be accurately determined. Furthermore, by increasing the transfer rate or the fixing rate for thick paper or envelopes, it is possible to prevent image deterioration.

[Brief description of drawings]

FIG. 1 is an image forming apparatus to which an embodiment of the present invention is applied.
It is a block diagram of (printer).

FIG. 2 is a block diagram of a laser printer to which an embodiment of the present invention is applied.

FIG. 3 is a diagram illustrating a paper size detection relationship according to an embodiment of the present invention.

FIG. 4 is a circuit diagram of a motor drive current detection circuit according to an embodiment of the present invention.

FIG. 5 is a processing flowchart of a motor drive current detection result in one embodiment of the present invention (transfer current increase processing).

FIG. 6 is a processing flowchart of a motor drive current detection result in one embodiment of the present invention (fixing current increase processing).

FIG. 7 is a processing flowchart of a motor drive current detection result in one embodiment of the present invention (fixing speed reduction processing).

FIG. 8 is a processing flowchart of a motor drive current detection result according to an embodiment of the present invention (processing for performing fixing a plurality of times).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Paper feeding device, 2 ... Recording paper, 3 ... Registration roller pair, 4 ... Photoconductor, 5 ... Charging charger, 6 ... Registration sensor, 7 ... Developing device, 8, 48 ... Transfer charger, 9 ... Fixing device, 10 … Printer body, 11
… Paper ejection unit, 12… Cleaning blade, 13… Toner recovery tank, 14,30… Controller, 15… Printer control unit, 16… Registration sensor, 17… Double-sided entrance guide, 18… Double-sided conveyance roller pair, 19… Reverse roller versus,
20 ... Reversing sensor, 21 ... Reversing guide, 31 ... External device, 32 ... CPU, 33 ... ROM, 34 ... Main motor drive circuit, 35 ... Main motor, 36 ... Paper feed clutch drive circuit, 37 ... Paper feed clutch, 38 ... Registration clutch drive circuit, 39 ... Registration clutch, 40 ... Polygon motor drive circuit, 41 ... Polygon motor, 42 ... Laser device, 43 ... Laser drive circuit, 44 ... Synchronous detector, 45
... optical writing control section, 46 ... paper size detection switch, 47 ... transfer current control circuit, 49 ... fixing temperature control circuit, 50 ... fixing roller drive circuit, 51 ... fixing roller, 52 ... fixing device,
53 ... Motor drive current detection circuit, 54 ... Paper feed cassette,
55… size detection switch, 56… size detection plate.

Claims (6)

[Claims] 1. A drive current detection means for detecting a drive current of a motor, and a drive current detected by the drive current detection means are read for each recording paper and compared with a preset value, and the recording paper is detected. A recording paper discriminating apparatus provided with a means for discriminating an envelope or a thick paper. 2. A determination is made as to whether the recording paper is an envelope or a thick paper by reading the difference between the drive currents at the time of idling rotation before printing and when the recording paper passes through the rollers and comparing it with a preset value. 2. The recording paper discriminating apparatus according to claim 1, further comprising: 3. The recording paper discriminating apparatus according to claim 1, further comprising a transfer current control means for increasing a transfer current when the recording paper discriminating means detects that the envelope is an envelope. 4. A fixing temperature control means for increasing the fixing temperature when the recording paper discriminating means detects that the recording paper is a thick paper or an envelope.
The recording paper discrimination device described. 5. A fixing speed control means for reducing the fixing speed when the recording paper discriminating means detects that the recording paper is a thick paper or an envelope.
The recording paper discrimination device described. 6. The recording paper discriminating apparatus according to claim 1, further comprising fixing control means for performing a plurality of fixing times when the recording paper discriminating means detects a thick paper or an envelope.