JPH07100378B2 - Image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and in particular, an image is formed by selectively lighting an arbitrary LED element of an LED head having a large number of LED elements according to print data. The image forming apparatus.

(Prior art) Since the characteristics of the LED head are affected by the temperature, the temperature of the LED head is detected by a temperature sensor, and the intensity of the current of the LED head is changed based on the detected temperature, so that the output is always constant. An image forming apparatus capable of obtaining light is disclosed in, for example, Japanese Patent Application Laid-Open No. 59-202879.

(Problems to be Solved by the Invention) In the above-described conventional device, since the temperature of the LED head is directly detected, the temperature sensor and the circuit associated with the temperature sensor are complicated and the miniaturization of the entire device is prevented, and We could not reduce the cost.

Therefore, a main object of the present invention is to provide an image forming apparatus capable of uniformly compensating the output light of an LED head with a simple and inexpensive structure.

(Means for Solving Problems) The present invention includes a photoconductor and a plurality of LED elements, and selectively illuminates an arbitrary LED element for each print request to irradiate the photoconductor with exposure light. LED head, counting means for counting the number of lighted LED elements of the LED head, calculating means for calculating light output correlation data of the LED element, and energization of the LED head according to the light output correlation data In the image forming apparatus provided with the energization time control means for controlling the time, the calculation means obtains from the total number of energized LED elements and the energization time after the use of the image forming apparatus is started by the counting means. An image forming apparatus comprising means for calculating the light output correlation data based on the accumulated data.

(Operation) When an image forming request is made, the LED head is driven and any LED element is selectively turned on in accordance with an image or print data. By selectively turning on the LED Emerent, exposure light corresponding to the data is generated, and the exposure light is applied to the photoconductor. Then, the number of turned-on LED elements is counted by the counting means. After that, the energization control unit controls the energization time of the LED head based on the count value.

When the count value by the counting means is large, the LED
Since the output light of the element may have decreased, the energization control means at this time lengthens the energization time of the LED element so as to keep the output light of the LED element constant.
On the contrary, when the count value is small, the light output of the LED element does not decrease so much, and therefore the predetermined output light can be obtained in a short energization time. shorten.

(Effect of the Invention) According to the present invention, based on the integrated data obtained from the total number of turned-on LED elements and the energization time after the use of the image forming apparatus by the counting means is started, the light output correlation data is obtained. Is equipped with a means to calculate the LED
It is possible to compensate for the decrease in output light due to the aging of the element.

That is, when the integrated count value in the state where the characteristics of the LED element have changed over time is large, it is possible to compensate for the decrease in the output light of the LED element and keep the output light constant.

The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments with reference to the drawings.

(Embodiment) FIG. 2 is a schematic sectional view showing an embodiment of the present invention.
Although the present invention is described below as being applied to an image forming apparatus, the present invention can also be applied to other image forming apparatuses other than such a printer, such as a copying machine and a facsimile. I will point out in advance.

The printer 10 includes a main body 12. A cover 14 and a cover 16, which are divided into two in the center, are provided on the top of the main body 12 so as to be flush with each other. The cover 14 is fixed to the main body 12 with screws. The cover 16 is provided so that it can be opened upward about the rotation shaft 18 when toner is supplied.

A paper feed unit 22 for detachably mounting the paper feed cassette 20 is formed on one end side of the main body 12, and a paper discharge unit 24 for ejecting the paper on which the fixing process is completed is formed on the other end side. It is formed.

A photoconductor drum 26 that rotates in the direction of the arrow (clockwise) (a drive mechanism thereof is not shown) is arranged at substantially the center of the main body 12. Amorphous selenium is used as the photosensitive material of the photosensitive drum 26.

A light emitting diode (LED) head 28 is provided above the photosensitive drum 26. The LED head 28 includes, for example, a red element having an emission wavelength λ = 660 nm, and includes LED heads provided in parallel along the length direction of the photosensitive drum 26. Further, a short focus lens such as a cellophox lens is inserted between the LED head and the photosensitive drum 26. Therefore, the LED head 28 selectively drives the LED elements according to the given print data,
The light of the LED element is focused by the lens system and is radiated onto the surface of the photosensitive drum 26.

The photosensitive drum 26 is uniformly positively charged to the upstream side of the LED head 28 in the rotation direction of the photosensitive drum 26, for example, about 60.
A charging corotron 30 for charging to 0 V is fixedly provided. After being positively charged by the charging corotron 30, when light is emitted from the LED head 28, an electrostatic latent image corresponding to print data is formed on the surface of the photosensitive drum 26.

A developing device 32 for developing an electrostatic latent image with toner is provided downstream of the LED head 28. This developing device
A developer (developer) composed of a mixture of toner and carrier is stored in 32. This developer is transferred toward the photosensitive drum 26 by the magnet roller 34. At this time, a magnetic brush of developer, that is, a spike is formed on the portion of the magnet roller 34 facing the photosensitive drum 26. When the ears are in contact with the photosensitive drum 26, the negatively charged toner is attracted to the electrostatic latent image formed by the positive charge. In this way, the electrostatic latent image formed on the photosensitive drum 26 is transferred to the developing device.
32 develops as a toner image.

Paper cassette 20 that is detachably attached to one end of the main body 12
Transfer papers 36 are placed in a stack in the inside. Paper cassette
A support plate 38 for mounting the transfer paper 36 thereon is provided at the bottom of the unit 20 so as to be vertically swingable. An opening 40 is formed in the lower portion of the support plate 38. This opening 40
The upper end of the push-up lever 42, whose base end is swingably attached to the inner fixed portion of the main body 12, is inserted into this. This push up lever 42
In connection with this, a spring (not shown) is provided for biasing the support plate 38 in a clockwise direction. Support plate 38
Is pushed upward by the push-up lever 42.
Therefore, the transfer papers 36 stacked in the paper feed cassette 20 are pushed up by the push-up lever 42, and the uppermost transfer paper 36 comes into contact with the paper feed roller 44 and is taken in. A paper size detector 46 for detecting the size of the transfer paper 36 stored in relation to the paper feed cassette 20 is provided at a portion corresponding to the leading end of the attached paper feed cassette 20.

A register roller 48 is provided behind the paper feed roller 44. The transfer paper 36 sent from the paper feed cassette 20 is temporarily stopped by the register roller 48, and is fed toward the photoconductor drum 26 in synchronization with the exposure by the LED head 28.
A register roller near the peripheral side surface of the photosensitive drum 26.
At the position where the transfer paper 36 is supplied from 48, a transfer corotron 50 for transferring the toner image developed by the developing device 32 to the transfer paper 36 is provided. This transfer corotron
A corotron 52 for separation is provided integrally with 50. The separating corotron 52 separates the transfer paper 36 adsorbed by the residual charge from the photosensitive drum 26 by applying an AC discharge to neutralize the charge.

At the downstream side of the separating corotron 52, a vacuum conveyor 54 for conveying the transfer paper 36 on which the toner image has been transferred is provided. With this vacuum conveyor 54, transfer paper
36 is conveyed toward the fixing device 56. Fixing device 56
Is a heating roller 58 with a built-in heater, and a heating roller
It is composed of a pressure roller 60 that is pressed against the 58. The transfer paper 36 on which the toner image is transferred is the heating roller 58 and the pressure roller.
By being inserted between 60 and 60, heat and pressure are applied to fix the toner development. A paper discharge roller 62 for discharging the transfer paper 36 after fixing is provided on the downstream side of the fixing device 56.

A cleaning device 64 is provided above the vacuum conveyor 54 and near the peripheral side surface of the photosensitive drum 26. The cleaning device 64 removes the toner remaining on the photosensitive drum 26 without being transferred to the transfer paper 36. The cleaning device 64 includes a blade 66 for scraping off the residual toner on the photosensitive drum 26, and a screw conveyor 68 for transporting the toner scraped by the blade 66 to a waste toner container.

On the upstream side of the cleaning device 64, an erase lamp 70 for removing the residual charge on the surface of the photosensitive drum 26 from which the residual toner has been removed is provided. As the erase lamp 70, a fluorescent glow lamp is used that generates a blue light beam, for example, a light beam having a wavelength λ = 450 nm, which has less light fatigue on the photosensitive drum 26 but can completely remove residual charges.

The photoconductor drum 26 and the developing device are provided above the fixing device 56.
A main motor 72 for driving 32 magnet rollers 34 and the like is provided. The photoconductor drum 26 and the magnet roller 34 are connected to the main motor 72 through a belt or a chain.
Driven by.

A control box 74 is provided above the main motor 72. A control unit for controlling the operation of the entire printer is provided in the control box 74.

FIG. 3 is a block diagram showing an example of the control system of this embodiment. This printer is controlled by CPU76,
A related memory 80 is connected to the CPU 76 through a bus line 78, and an I / O port 82 and a counter 84 are connected.

A print request signal is given to the input of the I / O port 82 from a host machine using such an image forming apparatus as an output device, such as a word processor or a personal computer. The LED head 28 is connected to the output of the I / O port 82. Print data from a host machine such as a word processor is given to a data input terminal Din of the LED head 28. A print synchronization clock from a clock source (not shown) is applied to the clock terminal CLK of the LED head 28. The print data is captured by the LED head 28 in a bit serial manner by a synchronous clock. That is, for example, the shift register in the LED head 28 is shifted by the synchronous clock, whereby the serial print data is converted into image data for one row, that is, for each column of LED elements. Print data is 1
When the rows are fetched, the LED head 28 selectively lights one row of the LED elements corresponding to the print data. When such one line of printing is being performed, the LED head 28 receives print data for the next line to be printed by the synchronous clock. In this way, the LED elements are sequentially turned on one row at a time, so that the LED head 28 is moved to the photosensitive drum 26 (second
Exposure).

On the other hand, the print data and the synchronous clock are logically ANDed by the AND gate 86 and are also given to the clock terminal CLK of the counter 84. That is, the counter 84 is the LED head 28
It continuously counts the number of LED elements that are lit in. Then, for example, every minute, count data for one minute is stored in the area 80a of the memory 80. Area 80a
Is always stored with count data for the past fixed time, for example, 30 minutes. That is, when the latest one-minute count data is supplied from the counter 84, the one-minute count data 30 minutes ago is cleared, and instead, the newly stored one-minute data is added to the past 29-minute data. Stored.

Area 80b of memory 80, like area 80a, is always past
The data of the energization time accumulated for 30 minutes is stored. However, the data is updated not every minute but every printout.

The temperature of the LED head 28 rises almost in proportion to the amount of power consumed by the LED head. Therefore, the count data for the past 30 minutes stored in area 80a and area 80a
The current temperature state of the LED head 28 can be predicted by the data of the energization time accumulated for the past 30 minutes stored in b. Based on this prediction, the energization time rate of the LED element of the LED head 28 that is turned on at the time of the next printout is controlled by the CPU 76 for each line.

In the area 80c of the memory 80, the data of the allowable temperature of the LED element at the time of use, that is, the data of the limit value, which are obtained by experiments, are stored.

Next, referring to FIG. 3, the operation which is the basis of this embodiment will be described based on the flow chart shown in FIG.

In the first step S11, the CPU 76 first determines whether or not a print request is given to this image forming apparatus. When a print request is made, that is, when a print request signal is input to the input port of the I / O port 82 from a host machine such as a word processor or personal computer to which the image forming apparatus is connected, the process proceeds to the next step S13. .

In step S13, preparation of a print sequence for executing printout is performed. That is, the main motor 72 for driving the photoconductor drum 26, the magnet roller 34 of the developing device 32, and the like are turned on.

Data calculated from the product of the respective data stored in areas 80a and 80b of the memory 80, that is, the LED
The temperature data predicting the temperature rise of the head 28 is loaded into the register included in the CPU 76.

In step S17, the temperature data of the LED head 28 loaded in the register in the previous step S15 is stored in the area 8 of the memory 80.
The temperature data preset to 0c is compared with the limit value. If the temperature data loaded in the register of the CPU76 is larger than the limit value set in the area 80c, that is, if the LED element continues to light up as it is, it reaches a temperature at which the LED element will be destroyed by the temperature rise of the LED head 28. If yes, go to step S19.

In step S19, the preparation for the print sequence started in step S13 is terminated here. That is, the photosensitive drum 26 and the magnet roller 34 of the developing device 32.
The main motor 72 that has been turned on for driving, etc. is turned off in this step S19.

Then, in step S21, a fixed delay time is counted. This delay time is a cooling time for lowering the temperature of the LED head 28 which has risen to the limit value due to continuous printout. After taking a certain delay time in step S21, the routine returns to the first step S11. Therefore, even if there is a print request in the first step S11,
When it is determined in step S17 that the temperature data loaded in the register of the CPU 76 is larger than the limit value stored in the area 80c, the print request at that time is not executed, and the first print is performed via steps S19 and S21. Step S1
Return to 1.

When it is determined in step S17 that the temperature data loaded in the register of the CPU 76 is not larger than the limit value set in the area 80c of the memory 80, the process proceeds to step S23.

In step S23, the energization time rate of the LED element of the LED head 28, that is, the ratio of the energization time of the LED element to the print cycle of one line by the LED head 28 is set according to the temperature data loaded in the register of the CPU 76. It As shown in FIG. 4, in the LED element of the LED head 28, if the light emission output at 20 ° C. is 100%, the light emission output decreases as the temperature rises. Therefore, in this embodiment, the energization time ratio of the LED element is set so that a constant light emission output is obtained from the LED head 28 according to the temperature data loaded in the register of the CPU 76.

When the loaded temperature data, that is, the data obtained by multiplying the number of LED elements turned on within a predetermined time by the energization time is, for example, the position I in FIG. 5,
Since the value is small, the temperature of the LED head 28 can be predicted to be low. Therefore, at this time, the light emission output of the LED element hardly decreases, and it is not necessary to increase the light emission output by lengthening the energization time unlike the case where the temperature rises. Therefore, in this case, the CPU 76 sets 40% as the energization time rate, as is clear from FIG. Then, since the cycle per row, that is, the print cycle per column of the LED element is 0.75 msec., The energization time t ₁ is t ₁ = 0. 0 as shown in FIG. 6 (A).
75 x 0.4 = 0.3 msec.

In FIG. 5, if the temperature data is at position II,
LED when the temperature data described above is in the I position
It can be predicted that the temperature of the head 28 is high. In other words, at this time, the number of lighting LED elements that have been integrated increases and the lighting time increases.
The temperature of D head 28 is rising. Therefore, it is necessary to correct the light emission output of the LED element so that the energization time is lengthened by the light emission output reduced by the temperature rise. Therefore, in this case, the CPU 76 sets the energization time ratio to 60%. Then, the energization time t ₂ per line is t ₂ = 0.75 × 0.6 =, as shown in FIG. 6 (B).
It will be 0.45 msec.

In FIG. 5, when the temperature data is at the position III, the printout is performed more continuously than the state at the position II described above, and the temperature of the LED head 28 reaches near the usable limit value. I can predict that Therefore, at this time, the light emission output of the LED element is considerably reduced, and a predetermined light emission output cannot be obtained unless the energization time is made longer than at the position II. So CPU7
6 sets 80% as the energization time rate. Then,
The energization time t _{3 at} this time is, as shown in FIG. 6 (C),
t ₃ = 0.75 × 0.8 = 0.6 msec.

In this way, the energization time rate is set according to the predicted temperature of the LED head 28, the energization time t ₁ , t ₂ or t ₃ is determined based on the set energization time rate, and the LED is used in the subsequent exposure process. The element is energized. For that purpose, the determined energization time rate is temporarily stored in a predetermined area of the memory 80.

Returning to FIG. 1, in the next step S25, a constant delay time is counted. This delay time is the time to wait for the leading edge of the transfer paper 36 to be conveyed to the register roller 48 by driving the paper feed roller 44.

In the next step S27, the LED head 28 is turned on and exposure is started. That is, when the print data and the synchronous clock as shown in FIG. 7 are given to the LED head 28, the print data is taken into the LED head 28 while shifting in the shift register in the LED head 28. When the shift for one row, that is, one column of LED elements is completed, the LED elements for one row of the LED head 28 are turned on based on the energization time determined in step S23.

On the other hand, the print data and the synchronous clock are also given to the AND gate 86. Then, the print data and the synchronous clock are logically ANDed by the AND gate 86, and the counter
Also given to 84. As explained above, the number of pulses applied to the counter 84 depends on the LEDs that are illuminated for exposure.
The number of LED elements of the head 28. Then, the count value of the counter 84 is supplied to the memory 80 every minute, and the area 80a of the memory 80 is updated every minute. In this way, the count value of the counter 84 becomes data for setting the energization time rate, that is, the energization time data of the LED element to be turned on later.

When exposure is started in step S27, as described above, L
The LED elements of the ED head 28 are selectively turned on line by line according to print data. The generated output light is applied to the photosensitive drum 26 as exposure light. Further, when exposure is started, a series of print sequences such as development, transfer and fixing are also started.

At the next step S29, the exposure started at the previous step S27 ends. That is, the LED head 28 is turned on and
The ED element was selectively lit according to the print data, but in this step S29 the exposure was completed and the LED head 28
Is turned off. After being turned on in step S27, the LED head 28 is turned on until it is turned off in step S29,
During this period, the LED elements are energized intermittently to selectively light. By this energization, the LED head,
Strictly speaking, the temperature of the LED element will be higher than when it started to light in step S27. Based on the temperature that may be rising, the energizing time of the LED element that is initially set in the next printout is set as described above.

In step S31, it is determined whether or not there is a print request. However, unlike the first step S11, the print request determined in step S31 is a determination in the case of continuous printing. Therefore, if it is determined in step S31 that there is a print request, that is, if it is determined that continuous printing must be performed,
Returning to the previous step S15, step S15 to step S31
Repeat the loop. If it is determined in step S31 that there is no print request, the process proceeds to step S33.

In step S33, the print sequence is prepared by driving the main motor 72 in step S13, but the main motor 72 is stopped here and the print sequence ends. Then, the process returns to the first step S11 again and enters a standby state of waiting for a print request through the external interface.

As described above, according to this embodiment, even if the output of the LED element decreases as the temperature of the LED head 28 rises, the light emitting output is increased by gradually increasing the energization time of the LED element every minute. Can be kept constant. Therefore, constant exposure light can be obtained within a range in which the temperature of the LED element does not exceed the limit value, so that a good printed image can be always obtained.

Next, referring also to FIG. 3, the operation of the embodiment of the present invention will be described based on the flowchart shown in FIG. In the following, the same steps S111, S113 and S as in FIG.
The description of 125 to S133 is omitted to avoid duplication.

The difference between this embodiment and the operation shown in FIG.
In S115, the point is to load not the temperature data but the integrated data related to the total energized electric energy of the LED element into the register of the CPU 76. That is, in the operation shown in FIG. 1, temperature data based on the value calculated from the number of LED elements lighted in the last 30 minutes and the lighting time in step S15 is loaded into the register of the CPU 76. On the contrary,
In the embodiment of FIG. 8, in step S115, the CPU 76
The data from the start of use of the printer 10 to the present is loaded into the register of. Such integrated data is integrated data obtained from a value obtained by multiplying the total energization time by the total number of lit LED elements that have been integrated since the start of use of the printer 10.

As shown in FIG. 9, the LED element light emission output also decreases according to the past power supply amount, that is, the usage time.
The amount of power supply is a value obtained by multiplying the lighting time, the applied voltage, and the inflow current, and thus can be calculated by multiplying the number of times of lighting and the lighting time. In this way, the integrated data is derived from a value obtained by multiplying the total number of times of lighting up to the present and the total lighting time.

For this purpose, the area 80a of the memory 80 stores the count value accumulated since the start of use. The area 80b stores data corresponding to the accumulated lighting time. Then, in area 80c, integrated data calculated from the data stored in areas 80a and 80b is temporarily stored. Therefore, in this embodiment, the routine corresponding to steps S17 to S21 in FIG. 1 is omitted, and in step S123, the energization time rate is set based on the integrated data loaded in the previous step S115. .

Referring to FIG. 10, when the integrated data loaded in step S115 is the position I, the LED element is still new. That is, in this case, the period after the image forming apparatus 10 has been used is short, and therefore the light emission output of the LED element of the LED head 28 is not significantly reduced. At this time, LE
A predetermined light emission output can be obtained even if the energization time of the D element is short. Therefore, in this case, the energization time rate is set to 40%. Then, the energization time t ₁ per row, like the FIG. 6 (A), becomes t ₁ = 0.3 msec..

In FIG. 10, when the loaded integrated data is at the position II, it can be expected that the LED element is older than at the position I. That is, in this case, the period of use is longer than the position of I, and therefore, the emission output of the LED element is further reduced. Therefore, a predetermined light emission output cannot be obtained in the same energization time as the position of I. Therefore, in this case, the energization time rate is set to 60%. Then, energization time t
₂ is t ₂ = 0.45mse, as shown in FIG. 6 (B).
c.

In FIG. 10, when the loaded integrated data is at the position III, the LED element is considerably worn out. That is, at this time, since the image forming apparatus 10 has been used for a long period of time, the characteristics of the LED element are significantly deteriorated. Therefore, in this case, the energization time rate is set to 80%. Then, the energization time t ₃
In the same manner as shown in FIG. 6 (C), t ₃ = 0.6 msec.
become.

The example of FIG. 1 and the embodiment of FIG.
There are an example of correcting a decrease in the light emitting output of the LED element due to a temperature change in use and an example of correcting a decrease in the light emitting output of the LED element with respect to a secular change.
However, the present invention takes into consideration the elements of temporary temperature changes and the elements of changes in characteristics over time at the same time.
It is also possible to keep the light emission output of the LED element constant.

[Brief description of drawings]

FIG. 1 is a flow chart for explaining the operation that is the basis of the present invention. FIG. 2 is a structural schematic view showing an embodiment of the present invention. FIG. 3 is a block diagram showing an example of the control system of this embodiment. FIG. 4 is a graph showing the value of the light emission output with respect to the temperature of the LED element. FIG. 5 is a graph showing an energization time rate with respect to temperature data. FIG. 6 is a diagram for explaining the set energization time per row. FIG. 7 corresponds to print data and synchronous clock
FIG. 6 is a timing chart for explaining operations of the LED head and the counter. FIG. 8 is a flow chart for explaining the operation of the embodiment of the present invention. FIG. 9 is a graph showing the value of the light emission output with respect to the total energized electric energy of the LED element. FIG. 10 is a graph showing the energization time rate with respect to the integrated data. In the figure, 26 is a photosensitive drum, 28 is an LED head, and 76 is C.
PU, 80 is a memory, 82 is an I / O port, and 84 is a counter.

Claims (1)

[Claims] 1. A photoconductor, an LED head including a plurality of LED elements, for selectively illuminating an arbitrary LED element to irradiate the photoconductor with exposure light whenever there is a print request, and the LED head is lit. Counting means for counting the number of LED elements, calculation means for calculating the light output correlation data of the LED elements, and energization time control for controlling the energization time of the LED head according to the light output correlation data In the image forming apparatus comprising means, the calculating means, based on integrated data obtained from the total number of energized LED elements and the energization time from the start of use of the image forming apparatus by the counting means, the light An image forming apparatus comprising means for calculating output correlation data.