JPS61101356A - Sheet transport equipment - Google Patents

Abstract

PURPOSE:To attempt enhancement of accuracy in position detection of a sheet, by applying clock pulses of an assigned frequency to the count input terminal of a counter, applying signals from a position detector to a clear terminal and counting the clock pulses after the resultant chattering is over. CONSTITUTION:When a copy sheet arrives, the output terminal of an optical sensor PSE is set to high level H, and a counter CNT starts counting of clock pulses transmitted from an oscillator OSC. During chattering, both H and L levels are repeatedly assigned to the output terminal of the optical sensor PSE, but when the period of chattering comes to the end, the counter CNT continues counting of clock pulses without being cleared. When said count valve A exceeds the value B which has been previously set in a latch LT, the output level of a digital comparator DCP is reversed to H and counting of the counter CNT is inhibited as well as an interruption demand is applied to a control unit CPU. Accordingly, the control unit CPU comes to know the control timing to stop a copy sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a device that conveys a sheet at high speed, such as a laser printer, and particularly relates to sheet position detection and sheet positioning. - [Prior Art] For example, in a copying machine with a 17th floor, copy sheets are mechanically positioned using registration rollers. Therefore, positioning accuracy is not very high. Positioning accuracy can be increased by using a sensor that detects the position of the sheet and, for example, controlling the driving of the sheet to be stopped after a predetermined period of time after detecting the leading edge of the sheet.

However, in this type of positioning, chattering that appears in the output signal of the sensor becomes a problem.

When detecting the position of a sheet, chattering is often unavoidable. In order to prevent the occurrence of malfunctions due to this chattering, a conventional method has been used in which a noise filter composed of a capacitor and a resistor is connected to the output terminal of the sensor.

By the way, in this type of noise filter, the timing difference between the sensor pressure signal and the signal obtained as the noise filter output is determined according to its integral time constant. However, since capacitors generally have large variations in characteristics,
If this poor noise filter is used, the detection timing will vary from device to device.

Although this variation in detection timing is relatively small, it leads to a large positioning error when detecting the position of a sheet that is driven at high speed, such as a recording sheet of a laser printer.

Furthermore, a method has been conventionally used in which the influence of chattering is eliminated by sampling a signal multiple times using a microcomputer used in a control circuit. However, in this case, the sampling interval must be made very small in order to obtain sufficient detection accuracy when detecting sheets that are transported at high speed. If the sampling interval is made smaller, the processing load on the microcomputer becomes extremely large, and there is a possibility that the microcomputer will not be able to process other processing.

[Object of the Invention] An object of the present invention is to detect the position of a sheet with high precision.

[Structure of the Invention] In order to achieve the above object, the present invention uses a counter, applies a clock pulse of a predetermined period to its counting input terminal, and applies a signal from a position detector to, for example, a clear terminal of the counter. During the chattering period, the count value of the counter is cleared, and after the chattering ends, the clock pulse is counted, and when it reaches a predetermined value, it is determined that the sheet has reached the predetermined position.

According to this, it is not necessary to remove chattering by rough 1-wear processing, and by making the period of the clock pulse applied to the counter sufficiently small, the sheet position can be detected with high precision. When positioning the sheet at a predetermined position, driving of the sheet may be stopped when the value of the counter reaches a predetermined value.

Example Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 depicts one type of laser printer embodying the invention. This laser printer has a writing optical system (1). It consists of an electrophotographic recording system 2 and a paper feeding system 3.

The writing optical system 1 includes a laser transmitter and a lens optical system.

The AO (ACOUST-OPTIC) modulator is equipped with a two-rotation polygon mirror, etc., and irradiates the photosensitive drum 4 of the electrophotographic recording system 2 with laser light according to image information applied to the AO modulator.

The electrophotographic recording system 2 has a similar configuration to the image reproduction system of a general copying machine, and includes a photosensitive drum 4. Electric charger 5. Developing device6. Transfer charger 7, separation charger 8. Jowaki 9
etc. In the electrophotographic recording system 2, the writing optical system l
The electrostatic latent image formed on the photoreceptor drum 4 is visualized with toner, transferred to a copy sheet fed from the paper feed system 3, and fixed.

The paper feed system 3 includes paper feed trays 10, 11 . Paper feed roller 12.
13. It is equipped with a registration roller 14 and the like. The PSE is an optical sensor for detecting a copy sheet fed from a predetermined paper feed tray by the paper feed system 3.

FIG. 2 shows an outline of the configuration of the apparatus shown in FIG. 1. Second
Referring to the figure, various devices are connected to the control unit CPU. The control unit CPU is a microcomputer system and includes a number of input and output ports. Note that the port INT is an interrupt request input port.

The image data to be recorded is sent from an image editing device (not shown).
It is input to port P7 of the control unit CPU via the interface unit IFU.

The control unit CPU stores input image data in a buffer memory provided in the writing optical system 1. The writing optical system 1 sequentially applies the de=res in the buffer memory to the A○ modulator at predetermined timing.

Writing optical system 1. The electrophotographic recording system 2 and paper feeding system 3 are connected to ports P4, P5 and P5 of the control unit CPU, respectively.
6. ML is a motor that drives the registration roller 14, and is connected to an output port P3 of the control unit CPU via a motor driver MD.

A circuit including an oscillator SC, an optical sensor PSE, a counter CNT, a latch LT, and a digital comparator DCP determines the timing at which the copy sheet reaches the registration roller 14. The output terminal of oscillator O8C is counter CN
The output terminal of the optical sensor PSE is connected to the clear control input terminal CLR of the counter CNT. The count output terminal of the counter CNT is connected to the input terminal A of the digital comparator DCP, and the output terminal UT of the latch LT is connected to the input terminal B of the digital comparator DCP. The output terminal A>B of the digital comparator DCP is connected to the control unit CPU.
It is connected to the interrupt request input port INT of the counter CNT and the counting permission control input terminal EN of the counter CNT. Latch LT
The data input terminal IN and latch control input terminal CP of are connected to the output ports P2 and Pl of the control unit CPU.

FIG. 3 shows an example of the timing of the output signals of the oscillator O8C, the optical sensor PSE, and the digital comparator DCP.The six oscillator OSC always outputs a clock pulse signal with a very short period. The output terminal of the optical sensor PSE is at a low level when no copy sheet is opposed to its detection surface, but becomes a high level H when a copy sheet is present.

However, due to the vibration of the copy sheet, the optical sensor PS
Chattering occurs until the output terminal of E completely changes from low level L to high level H.

The period during which this chattering occurs is generally 5 to 10
It is about m5ec.

When the optical sensor PSE does not detect a copy sheet, its output terminal is at a low level L, the counter CNT is always cleared, and the count value remains zero.

When a copy sheet arrives and the output terminal of the optical sensor PSE changes to a high level H, the counter CNT is cleared and starts counting the clock pulses output from the oscillator O8C. However, when the output terminal of the optical sensor PSE returns to the low level L due to chattering, the counter CNT is cleared again and its count value becomes 0. Repeat this operation and when the chattering period ends,
Counter CNT counts clock pulses without being cleared. When the counted value (A) becomes larger than a certain value (B) set in advance in the latch LT.

The output level of the digital comparator DCP is inverted to high level H, an interrupt request is made to the control unit CPU, and counting of the counter CNT is prohibited.

That is, when the chattering of the signal from the optical sensor PSH ends, that is, after the starting edge of the copy sheet is completely detected, an interrupt is generated in the control unit CPU. Therefore, the control unit CPU
The control timing at which the copy sheet should be stopped can be determined by software processing without referring to the signal from the optical sensor PSE.

FIG. 4 shows a schematic operation of the control unit CPU shown in FIG. 2. Please refer to FIG. When the power is turned on, the initial system settings are performed. That is, the output port is set to the initial state, the memory is cleared, a predetermined initial value is set to a predetermined address of the memory, and the operation modes of various control units are set to the initial state.

Next, predetermined data is set in the latch LT.

This is done by setting the value corresponding to the time T shown in FIG. 3 to the output port P2 and outputting a pulse to the output port P1. It is held at OUT. In addition, since the output of the counter CNT is O at first, the digital comparator DC
The output terminal of P is low level L, and the control unit CPU
No interrupt request is generated.

It waits for a recording instruction from the image editing device, and upon receiving it, sets the writing optical system 1 and the electrophotographic recording system 2 to a recordable state. Also, the motor M1 is set to the on state and one interrupt is permitted. When the preparation is complete, interface "Ready to receive data".

Output to unit IFU. Then, when predetermined image data is sent from the image editing device, receive it and
The data is stored in the buffer memory of the writing optical system 1. Incidentally, when the buffer memory of the writing optical system 1 becomes full, "data cannot be received" is outputted to the interface unit IFU to notify the image editing apparatus.

The control unit CPU controls each part of the electrophotographic recording system 2 and paper feeding system 3 at predetermined timings while executing loop-like processing until the end of recording is detected.
At a predetermined timing, the paper feed rollers of the paper feed system 3 are driven,
One copy sheet is fed. Furthermore, since the motor M1 is in the on state, the copy sheet being fed is further fed even if its leading edge reaches the registration rollers 14.

When the leading edge of the copy sheet reaches the position of the optical sensor PSE and a predetermined time T has elapsed, the control unit CPU
An interrupt request is generated. When this request occurs, the control unit CPU interrupts the processing of the main routine and
Execute "interrupt processing".

When entering the "r'1llJ processing", the control unit CPU immediately sets the motor M1 to the OFF state, prohibits interrupts, and immediately returns to the main routine processing.

Through the processing up to this point, the copy sheet is controlled to stop accurately at a predetermined position.

When the predetermined sheet feeding timing arrives, motor M1
is reset to the on state, and the copy sheet is sent to the photosensitive drum 4 of the electrophotographic recording system 2. When recording is finished, write optical system 1. The electrophotographic recording system 2, paper feeding system 3, and motor M1 are set to OFF, interrupts are prohibited, and the next recording instruction is awaited.

In the above embodiment, the motor M1 is directly controlled to position the seat, but the motor may be set to be in a constant driving state and positioning may be performed using a clutch or the like. Furthermore, in the embodiment, the output pulses of the specially provided oscillator O8C are counted by the counter CNT; however, for example, a structure may be adopted in which the timing pulses generated in synchronization with the rotation of the photoreceptor drum 4 are counted by the counter CNT. . Furthermore, the sheet detection means is not limited to an optical sensor, but may also be a mechanical detection means such as a microswitch, an ultrasonic sensor, or the like.

[Effects] As described above, according to the present invention, the seat can be positioned accurately, and the load placed on the main body of the control device such as a microcomputer is small, so the structure of the control device is simple.

In this way, the seat can be positioned accurately.

Since no deviation occurs in the recording position, additional recording can be performed on a recording sheet on which standard information has been recorded in advance.

[Brief explanation of the drawing]

FIG. 1 is a front view of one type of laser printer embodying the invention. FIG. 2 is a block diagram showing the configuration of the apparatus shown in FIG. 1. FIG. 3 is a timing chart showing the timing of some signals in the circuit of FIG. FIG. 4 is a flowchart showing the general operation of the control unit CPU shown in FIG. 2. ■: Writing optical system 2: Electrophotographic recording system 3: Paper feeding system 4: Photosensitive drum 5: Charger
6: Developing device 7: Transfer charger 8: Separation charger 9: Fixing device 10.11: Paper feed tray 12.13: Paper feed roller 14 Ni registration roller CPU: Control unit (electronic control means) PSE: Optical sensor (sheet detection Means) 0302 oscillator CNT
: Counter LT: Launch (setting value holding means) DCP: Digital comparator Ml: Motor (driving means) Fig. 1

Claims (4)

[Claims] (1) Driving means for driving the conveyance of the sheet; An oscillator for outputting a pulse signal of a predetermined period; Sheet detecting means for detecting the sheet: A pulse signal from the oscillator in accordance with a signal output from the sheet detecting means. A sheet comprising: a counter for counting; a set value holding means; a digital comparator for comparing the output of the counter with the output of the set value holding means; and an electronic control means for energizing the driving means in accordance with a predetermined instruction. Conveyance device. (2) the electronic control means stops energizing the drive means when the digital comparator outputs a predetermined comparison result;
A sheet conveying device according to claim (1). (3) The sheet according to claim (1), wherein the output terminal of the oscillator is connected to the count input terminal of the counter, and the output terminal of the sheet detection means is connected to the clear terminal of the counter. Conveyance device. (4) The sheet conveyance device according to claim (1), wherein the set value holding means is a latch circuit connected to the output of the electronic control means.