JP2001121750A - Print head of printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify read control of strobe time information and correction data from a memory circuit. SOLUTION: When determined strobe time information or correction data is stored in the memory circuit 10c at a control section 10, the correction data is stored at an address succeeding to that for storing the strobe time information. The correction data can be read out from the memory circuit 10c by simply incrementing a counter from '000' without requiring address management.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a print head of an electrophotographic printer, and more particularly, to a method for adjusting a light emission amount of an LED mounted on such a print head.

[0002]

2. Description of the Related Art Conventionally, an electrophotographic printer has been widely used as a printer for printing text and images created by a computer or the like. FIG. 8 is a diagram showing a configuration of a printing unit in the electrophotographic printer. When printing a text or an image, first, the charging roller 1 applies a negative charge to the rotating photosensitive drum 2 to charge the photosensitive drum 2 negatively. Next, the print head 3 including a plurality of LEDs and the like
However, by irradiating the photosensitive drum 2 with light, an electrostatic latent image of a sentence or an image to be printed is formed. Then, the developing device 5 causes the negatively charged toner 6 to adhere to the electrostatic latent image and develops the image. Further, the transfer roller 4 to which a positive voltage is applied from the transfer power supply 8 applies the toner adhering to the photosensitive drum 2 to the paper 7 by electrostatic force.
Has been transferred to Thereafter, the toner is fixed on the sheet 7 by a fixing device (not shown).

[0003] The print head 3 for forming an electrostatic latent image in this manner is composed of an LED array, an LED driver and the like. The LED array is composed of thousands of LEDs arranged in a direction perpendicular to the traveling direction of the paper of FIG. 8, and the LED driver is composed of the same number of transistors as the number of LEDs. The transistors in the LED driver receive a common strobe signal for controlling the on / off of the transistors from a control unit that controls the entire printer apparatus, and preliminarily receives the strobe signal only while the strobe signal is on. A current flows through the LED selected by the image data.

[0004] In this print head, the LEDs in the LED array are caused by variations in manufacturing conditions at a factory or the like.
The relationship between the current supplied per unit element and the amount of light emission at that time (hereinafter referred to as "luminous efficiency") slightly varies. For example, some LEDs can emit a large amount of light with a small current, while others can emit a small amount of light with a large amount of current. Such variation is LED
This is more noticeable between LED arrays than between elements. Further, as for the transistors in the LED driver, some transistors allow a large amount of current to flow at the same voltage due to the difference in resistance between the semiconductor elements, but some transistors allow a small amount of current to flow. Such variations are more likely to occur between the LED elements than between the transistor elements.
It is more prominent between Cs. Thus, LE
Since the characteristics of D and the characteristics of transistors vary, in the process of manufacturing these LED arrays and LED driver ICs, the LED arrays and LED driver ICs are sorted according to their characteristics, divided into several ranks, and The head is configured by assembling LED arrays and driver ICs belonging to By such a work, a certain LED
In the head, LED arrays with high luminous efficiency are integrated, and in another LED head, LED arrays with low luminous efficiency are integrated.
As a result, it is possible to suppress variations in characteristics among the respective LED arrays in the LED head. Similarly, for an LED driver, a certain LE
In the D head, driver ICs having high-resistance transistors are assembled together, and in another LED head, driver ICs having low-resistance transistors are assembled.

In the above-mentioned conventional print head, each LE
In order to make the light emission amount of each element of D as uniform as possible, LED
A non-volatile storage element is provided in the head, and correction data for individually correcting the current supplied to each LED is set. When determining this correction data in the manufacturing process of the head, temporary correction data is set, and the temporary correction data is written to a nonvolatile storage circuit in the LED head, and the temporary correction data written to the storage circuit is written. Transfer the data to the LED driver, measure how much the LED emits light under the correction data, and based on the result of the measurement,
The work of correcting the temporary correction data again and setting it again is repeated. As a result, finally, the optimum correction data is determined.

[0006] On the other hand, the most suitable one for exposing the photosensitive drum.
The amount of light emission energy per dot (hereinafter, referred to as “total light emission amount”) is determined in advance. This total light emission amount can be represented by the product of the light emission power and the energization time (ie, strobe time). Therefore, it is necessary to determine an appropriate value for the strobe time based on the characteristics of the LED and the characteristics of the transistor. For example, it is necessary to set a short strobe time for an LED head in which LEDs having excellent luminous efficiency are integrated, while for an LED head in which LEDs having poor luminous efficiency are integrated, , It is necessary to set a longer strobe time.

In order to set such a strobe time, in the process of manufacturing an LED head,
The average emission power of each dot of the head is measured, the result of the measurement is written on a barcode label, and the barcode label is attached to the print head. Thereafter, in a step of assembling the entire printer apparatus, that is, in a step of combining the printing unit and the control unit to complete the printer apparatus, the measurement result written on the barcode label is read, and the read measurement value is read. Based on the result, strobe time information is calculated, and the calculated strobe time is written to a nonvolatile memory in the control unit. Then, at the time of actual printing, the control unit transmits a strobe signal of a predetermined time width based on the strobe time information read from the nonvolatile memory together with the image data to be printed received from the computer, and the LED head. Sent to In this way, the LED emits light only during the strobe time, creating an electrostatic latent image on the photosensitive drum.

[0008]

In such a conventional print head, the determined strobe time information and correction data are stored in a storage circuit. However, the correction data and the like are stored in the storage circuit for comparison, verification, confirmation, and the like. It has been desired to simplify read control when reading data.

[0009]

According to the present invention, there is provided a printing element array comprising a plurality of printing elements which operate to form an image to be printed, and correction data for individually adjusting the operation amount of each printing element. And a storage circuit for storing correction data and eigenvalues based on the characteristics of the print head. The print element driver includes a plurality of drive elements provided for each print element. Wherein the printing element driver has a shift register for setting correction data, and the storage circuit stores the correction data at an address subsequent to the address for storing information on the strobe time. And

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS <Structure of Specific Example> FIG. 1 is a diagram showing a structure of a print head according to a specific example. This print head includes a control unit 10, an LED driver 20, and an LED array 30. Then, a manufacturing / inspection apparatus or a control unit 100 (hereinafter, simply referred to as a “control unit”) for manufacturing, inspecting, or controlling the print head or a printer in which the print head is built.
It is connected to the. The control unit 10 includes the switch control circuit 1
0a, a switch circuit 10b, and a storage circuit 10c. Then, from the control unit 100, the clock signal CLK, the strobe signal STB, the data signal DAT
A or the like is input. The switch circuit 10b switches the transmission / reception direction of the data signal DATA among the three of the control unit 100, the storage circuit 10c, and the LED driver 20. The switch control circuit 10a controls switching of the switch circuit 10b based on a command signal sent from the control unit 100 onto the data line DATA. The storage circuit 10c stores correction data and strobe time information sent from the control unit 100 as described later.

FIG. 2 is a diagram showing details of the configuration of the switch circuit. This switch circuit 10b includes two tri-state elements 10b-1 and 2 and one switch element 10b
As will be described in detail later, the control signal from the switch control circuit 10a is configured to secure a route necessary for executing the inspection mode, the write mode, the read mode, and the transfer mode. ing.

As shown in FIG. 1, the LED array 30
It is composed of a plurality of array units 30A to 30M,
To cope with such a configuration, the LED driver 20
Also includes the same number of driver units 20A to 20M. The array units 30A to 30M each include a plurality of LEs.
D31a to D31n, and similarly, the driver units 20A to M are also configured from the same number of drivers 21a to 21n.

Each of the drivers 21a to 21n is connected to each of the LEs.
D31a-n, the main driving transistor T
a transistor unit TR composed of r0 and four auxiliary driving transistors Tr1 to Tr4, and a shift register S1.
And a storage unit M1. The reason why the transistor unit TR is configured in this manner is to correct the light amount so as to be uniform, and more specifically, to reduce the difference in the light emission amount of the LEDs in the same array unit as much as possible. That's why. For example, a certain LED 31a
If the luminous efficiency of the LED is low, turning on all the transistors Tr1 to Tr4 causes a large amount of current
When the light emission efficiency is extremely high, the LED 31a is driven with a small current by turning off all the transistors Tr1 to Tr4. If the luminous efficiency is between them, the transistors Tr1 to Tr1
By turning on 4 selectively, the light emission amount is made substantially uniform. Furthermore, other LEDs 31b-3
Also for 1n, the light emission amount is adjusted in the same manner as the LED 31a.

The shift register S1 is for transferring image data.
The storage unit M1 is for transferring correction data. The storage unit M1 for transferring correction data includes a register or an SRAM cell capable of high-speed writing and high-speed reading.
Each LED in the LED array 30 is
Accordingly, the strobe signal ST based on the image data from the shift register S1 and the correction data from the storage unit M1
Current is supplied only during the time indicated by B to emit light.

<Outline of Operation> The outline of the operation of the print head and the control unit thus configured is as follows. When the power of the printer device is turned on, the control unit reads out information on the strobe time from the storage circuit 10c and stores the strobe time information in a volatile storage element (RAM) in the control unit, while the strobe signal generation circuit Data is stored in the register. Also,
The control unit outputs the clock signal to L through the control unit 10.
The correction data in the storage circuit 10c is transmitted to the ED driver 20 to drive the shift register S1.
This is set in the storage unit M1 of the D driver.

On the other hand, at the time of printing, the control unit
After transmitting image data received from a computer (not shown) to the D driver 20 on the data line DATA, the strobe signal line STB is driven for a predetermined strobe time.
Thus, each LED 31a in the LED array 30
The currents are supplied to the photosensitive drums 2 to 31n only during a period in which the strobe signal line STB is active, and the photosensitive drum 2 is irradiated with light to create an electrostatic latent image of an image to be printed on the photosensitive drum. .

<Details of Operation> The operation of such a print head is performed as follows. Manufacturing and inspection equipment
1. “Test mode (TEST)” for determining the correction data of each LED and the strobe time; 2. "Write mode (WR)" in which the manufacturing / inspection apparatus writes the correction data and the strobe time in the storage circuit 10c. A “read mode (RD)” in which the manufacturing / inspection apparatus or the control unit reads out the strobe time information written in the storage circuit 10c;
4. The correction data of the storage circuit 10c is stored in the LED driver 20
The transfer mode is divided into four modes of “transfer mode (TR)”. Hereinafter, the operation in each mode will be described with reference to FIGS.

<Description of Test Mode (TEST)> In the process of manufacturing and testing the print head, the LED array 30
The operation of the inspection mode for determining the correction data and the strobe time of each of the LEDs 31a to 31n will be described with reference to FIG. Step S10: Manufacturing connected to print head
The inspection device sends a command signal indicating that the mode is the inspection mode on the data DATA line, and sends a clock signal CLK to the control unit 10. Step S11: Switch control circuit 1 in control unit 10
0a is obtained by analyzing the received command signal,
It is determined that the mode is the inspection mode (TEST).

Step S12: Switch control circuit 10
A switches the switch circuit 10b so that the temporary correction data is transmitted and received from the manufacturing / inspection device to the LED driver 20. Step S13: The manufacturing / inspection device checks the data DATA
The temporary correction data is transmitted on the line, and the clock signal CLK is separately transmitted to set the temporary correction data in the storage unit M1 via the shift register S1. Step S14: The manufacturing / inspection device sends out the test image data on the data DATA line, and sends out the strobe time as the strobe signal STB. Step S15: The LED driver 20 drives each LED 31a to 31n in the LED array 30.

Step S16: Driven LED 31
The light emitted from a to 31n is measured for each dot by a light amount measuring device light (power meter) (not shown), and the manufacturing / inspection device displays the measured result. Step S17: It is determined whether the variation in the light emission amount is within a predetermined range or not, and whether the temporary correction data is appropriate. Step S18: If the temporary correction data is inappropriate, the temporary correction data is corrected, and the corrected correction data is directly set again in the LED driver without passing through the storage circuit 10c. This makes it possible to transfer the correction data to the LED driver at a high speed. Step S19: Since the variation in the light emission amount is within the predetermined range, it is necessary to set the light emission amount based on the average value of the light emission power measurement values of the respective LED elements and the predetermined total light emission amount required by the photosensitive drum. The calculated strobe time is calculated.

As described above, the temporary correction data for each LED in the LED array is transmitted from the outside of the print head to L.
It can be transferred directly to the ED driver. Therefore, when determining the predetermined correction data for adjusting the magnitude of the current supplied to each LED, the temporary correction data can be easily changed and transmitted to the LED driver. Accordingly, predetermined correction data suitable for each LED can be quickly determined. Further, in the operation of determining the correction data, the strobe time can also be calculated based on the measured light emission amount.

<Description of Write Mode (WR)> Write mode for writing the correction data and information on the strobe time to the storage circuit 10c, which is performed after appropriate correction data is obtained in the test mode (TEST). The behavior of
Description will be made with reference to FIG. Step S20: An instruction signal indicating the write mode (WR) is sent from the manufacturing / inspection apparatus to the print head by the data DATA.
The clock signal CLK and the clock signal CLK are separately transmitted to the control unit 10 on the line. Step S21: Switch control circuit 1 in control unit 10
0a is obtained by analyzing the received command signal,
It is determined that the mode is the write mode.

Step S22: Switch control circuit 10
a, the correction data obtained in the test mode (TEST) and the information on the strobe time are stored in the storage circuit 1
The switch circuit 10b is switched so as to be transmitted / received to 0c. Step S23: The manufacturing / inspection apparatus sends strobe time, head type information, head version information, correction data, and the like on the data DATA line. Thereby, the information data is written into the storage circuit 10c.

Here, the order of the information data written in the storage circuit 10c is as shown in FIG. By writing in such an order, the address management by the control circuit (not shown) of the storage circuit 10c when transferring the correction data to the shift register S1 becomes easy. This is because, when the correction data is transferred to the storage unit M1 via the shift register S1, the transfer of the correction data can be managed only by incrementing the counter sequentially from "000". Therefore, it is possible to eliminate a complicated procedure for managing an address where a portion where the correction data is stored is located.

As described above, unlike the conventional case, the LED
It is possible to omit the operation of writing the strobe time information on the barcode label in the head manufacturing process, reading out the strobe time information in the process of assembling the entire printer device, and writing it in the nonvolatile memory circuit in the control unit. . As a result, the manufacturing period can be shortened, and the manufacturing cost can be reduced.

<Explanation of read mode (RD)> In the write mode (WR), information on strobe time, head type information, head version information, correction data, and the like written in the storage circuit 10c are manufactured and inspected by the manufacturing / inspection apparatus or control unit. The operation in the read mode for reading the data will be described with reference to FIG. Step S30: The manufacturing / inspection apparatus or the control unit sends a command signal indicating the read mode to the data DAT.
The clock signal CLK is transmitted to the control unit 10 while being transmitted on the line A. Step S31: Switch control circuit 1 in control unit 10
0a is obtained by analyzing the received command signal,
It is determined that the mode is the read mode.

Step S32: Switch control circuit 10
“a” indicates that strobe time, head type information, head version information, correction data, etc. are manufactured and stored in the storage circuit 10c.
The switch circuit 10b is switched so as to be sent to the inspection device or the control unit. Step S33: The manufacturing / inspection apparatus or control unit reads out the information data from the storage circuit 10c. The read information data is displayed on a display unit (not shown), and is compared / verified with master data used for writing in the write mode.

As described above, after writing the correction data in the storage circuit 10c on the print head, the written correction data can be read out to the outside. Further, it is possible to write and read out various information on the printer device, for example, the type of the print head. This makes it possible to read out again and check whether or not the determined correction data is correctly written in the storage circuit in the print head. At the same time, when the printer device is maintained and inspected, the control unit 100
Can read out information about the print head stored in the storage circuit 10c, and execute various controls based on the read out information. As a result, the maintenance staff can easily replace the print head.

<Description of Transfer Mode (TR)> Storage Circuit 10
The transfer mode for transferring the correction data stored in c to the LED driver 20 is as follows. Step S40: The manufacturing / inspection apparatus or control unit sends a command signal indicating that the mode is the transfer mode to the data DAT.
The clock signal CLK is transmitted to the control unit 10 while being transmitted on the line A. Step S41: Switch control circuit 1 in control unit 10
0a is obtained by analyzing the received command signal,
It is determined that the mode is the transfer mode.

Step S42: Switch control circuit 10
a indicates that the correction data stored in the storage circuit 10c is
The switch circuit 10b is switched so as to be transferred to the LED driver 20. Step S43: The correction data stored in the storage circuit 10c is such that the clock signal CLK is the shift register S1.
Are set in the LED driver 20.

In the above specific example, correction data is mainly processed, but information on strobe time, head type information, head version information, and the like can also be processed. Therefore, with respect to such information data, writing, reading, and the like can be arbitrarily executed between the control unit, the storage circuit, and the LED driver 20.

[Brief description of the drawings]

FIG. 1 is a block diagram of a print head according to the present invention.

FIG. 2 is a diagram showing a configuration of a switch circuit of the present invention.

FIG. 3 is an operation flowchart of an inspection mode.

FIG. 4 is an operation flowchart of a write mode.

FIG. 5 is a map diagram of the storage circuit of the present invention.

FIG. 6 is an operation flowchart of a read mode.

FIG. 7 is an operation flowchart of a transfer mode.

FIG. 8 is a configuration diagram of a conventional electrophotographic printer.

[Explanation of symbols]

 Reference Signs List 10 control unit 10a switch control circuit 10b switch circuit 10c storage circuit 20 LED driver 30 LED array

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H01L 33/00

Claims (2)

[Claims] 1. A printing element array comprising a plurality of printing elements that operate to form an image to be printed, and each printing based on correction data and strobe time for individually adjusting the operation amount of each printing element. A print element driver composed of a plurality of drive elements provided for each print element for driving the elements, and a storage circuit for storing correction data and a unique value based on the characteristics of the print head. And a shift register for setting correction data, wherein the storage circuit stores the correction data at an address subsequent to an address at which information on the strobe time is stored. 2. An LED array comprising a plurality of LEDs for emitting an electrostatic latent image of an image to be printed, based on correction data for individually adjusting the amount of light emitted from each LED and a strobe time. Each LE that drives each LED
An LED driver comprising a plurality of driving elements provided for each of the Ds; and a storage circuit for storing correction data and a unique value based on the characteristics of the print head, wherein the LED driver performs a shift for setting the correction data. A print head for a printer device, comprising a register, wherein a storage circuit stores correction data at an address subsequent to an address at which information on strobe time is stored.