JPH02164561A - Led printer head - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention ■ Chestnut-like insect seal and light stand The present invention is an LE that exposes light emitted from an LED array to a charged object such as a photoreceptor drum through a convergent light transmitter.
Regarding the D printer head.

YotsujiIn this type of LED printer head, the copy quality (
In order to improve image quality), it is necessary to detect changes in LED light intensity (changes in output) due to changes in temperature inside the printer,
It is necessary to constantly correct (control) the amount of light emitted from the LED array to a desired value based on the detection results.

Conventionally, the amount of light has been detected by detecting the reflected light emitted from the LED array and reflected from the surface of the photoreceptor drum.

However, when detecting the light reflected from the photoreceptor drum as described above, the following drawbacks prevent accurate light amount detection, resulting in poor copy quality. There were limits to how much improvement could be made.

That is, (1) since the toner stains the surface of the photoreceptor drum, the reflection efficiency of the photoreceptor drum fluctuates, resulting in a drawback that accurate detection cannot be performed.

■The photoreceptor drum has a structure in which a photoconductive layer made of, for example, a selenium-based semiconductor is formed on the aluminum drum surface, so when used for a long period of time, scratches due to optical fatigue etc. This method has the disadvantage that it causes changes in the thickness of the layer, making it impossible to perform accurate detection.

The present invention has been made in view of the current situation, and enables highly accurate light amount detection over a long period of time, and as a result,
An object of the present invention is to provide an LED printer head that can improve copy quality.

Another object of the present invention is to save power consumption and toner.

The present invention is an LED printer head that exposes an object to be charged with light emitted from an LED array through a convergent light transmitter, the LED printer head including the LED array and at least a base end of the convergent light transmitter. The unit is sealed in a casing, and a light receiving element is disposed in a position that does not obstruct the optical path of the light in the casing, and the LED emits light during a predetermined pattern corresponding to a time when an image of the original is not formed. Direct light from the array and reflected light from the end face of the convergent light transmitter are detected by a light receiving element, and based on the detection results, the LE
The feature is that the amount of light emitted from the D array is controlled.

The above-mentioned predetermined pattern corresponds to, for example, a case where an AIDC pattern, which is a pattern for toner density control, is executed.

In such a case, the object to be charged will be exposed to a desired amount of light during image development based on the light amount detection result detected at the time when the original image is not formed.

LUL-KAWA An embodiment of the present invention will be specifically described below based on the drawings. FIG. 1 is a partially cutaway side view showing an LED printer head according to the present invention together with a photoreceptor drum, and FIG.
FIG. 3 is a block diagram showing the IR+7 control system, and FIG. 4 is a timing chart showing the control operation.

A photoreceptor drum 1 is rotatably mounted 7 at a predetermined position inside the printer main body (not shown), and an LE is mounted above it.
D printer head 2 is installed.

The LED printer head 2 has a basic structure in which a hollow casing 21 that is wide at one end is attached to the lower surface of an aluminum heat sink 20 that is long in the axial direction of the photosensitive drum 1. The lengths of the aluminum heat sink 20 and the casing 21 are selected to be approximately equal to the axial length of the photoreceptor drum 1. Then, the following members are attached to the internal space that is maintained in a sealed state by both.

That is, a ceramic substrate 22 is attached to the lower surface of the aluminum heat dissipating +ff 120 over almost its entire length, and is electrically connected to the lower surface corresponding to the widthwise center portion of the ceramic substrate 22 with gold wires 23 and 23. Drive IC2
4 and an LED chip 25 are mounted. Drive IC
Reference numeral 24 controls the driving of the L'ED chips 25, and both of them are provided in large numbers in the longitudinal direction of the ceramic substrate 22, and the L'ED array 26 is configured as a whole. Note that the ceramic substrate 22 is connected to a power source and a controller (not shown) via a flexible substrate 29 and a connector 40.

The upper part of the convergent light transmitter 27, which condenses the light emitted from the 5ED array 26 and exposes the surface of the photoreceptor drum 1, is sandwiched on the narrow lower end side of the second casing. be. The convergent light transmitting body 27 is formed by disposing a large number of rod lenses distributed over a predetermined width dimension over substantially the entire length of the LED array 26 in the longitudinal direction.

In addition, the inside of the casing 21 receives the direct light emitted from the LED array 26 and the reflected light reflected from the upper end surface of the convergent light transmitter 27, and calculates the amount of received light, that is, the amount of detected light, as shown in FIG. dynamic amplifier 30 and A/D converter 31
The light receiving element 2 inputs to the micropro sensor 32 via
8 is the installation. The mounting position of the light receiving element 28 is not limited to the position shown in FIG.
6. More specifically, the position may be any position other than the position that obstructs the optical path of the light emitted from the LED chip 25 and incident on the upper end surface of the convergent light transmission body 27. Note that the differential amplifier 30
cancels changes in the amount of detected light due to temperature fluctuations,
In other words, it has a temperature compensation function.

The microprocessor 32 receives the detection result of the light receiving element 28 (
(detected light amount) and have been set and input into the memory 33 in advance,
A correction bone for the light amount at the time of detection is calculated based on the reference light amount data (data regarding the amount of light emitted necessary for performing a preferable exposure operation) of the ED chip 25, and the calculation result is input to the controller 34.

The controller 34 controls the drive of the LED chips 25 in the LED array 26, more specifically, the drive IC 2.
4, and the amount of light emitted by the LED chip 25 is increased by the amount corresponding to the correction bone (
or down). Specifically, the drive current value (or drive voltage value) P of the LED chip 25 or the drive time t (more specifically, the duty ratio of the drive pulse) of the LED chip 25 is controlled to emit light, as shown in (2) below. The amount of light (energy value) E is controlled.

E=P・t...■ The above control operation is performed according to the timing chart shown in FIG. 4, but the light amount detection by the light receiving element 28 is
IDC (Auto Image Density C)
This is performed at a time when image formation is not performed, such as when writing an ontroj mark, when performing an inter-image erase, and when performing a site erase.

What is the writing of the AIDC mark here? This is done to control the R degree and improve copy quality.

Specifically, in the development process, the concentration (supply amount) of the toner that adheres to the electrostatic latent image formed on the surface of the photoreceptor drum 1 and makes it visible is always controlled to a constant value. be done. That is, in this AIDC method, spot-shaped spots corresponding to a black reference pattern formed, for example, in front or behind a document platen glass (not shown) are placed on a portion of the surface of the photoreceptor drum 1 corresponding to an area other than the document image. forming a reference latent image,
This is developed to obtain a reference image, and then the amount of toner adhering to the reference image is detected. Based on this detection result, the amount of toner in the developer in the developer tank is always set constant. It controls Tonane 1 (1 star).

The writing of this AIDC mark is performed by normal rotation (regular) development in which positively charged toner is adhered to the surface of the photoreceptor drum, which is negatively charged and not irradiated with light from the LED array 26, to perform development. Not only in this case, but also conversely, a reversal development type is performed in which development is performed by attaching negatively charged toner from a developing device to the surface of the photoreceptor drum 1 that is not irradiated with light from the array 26. It is also done in cases.

Incidentally, FIG. 1 shows the VJ process in which three AIDC marks are written during reversal development, and a spot-shaped AIDC mark 29 shown by diagonal lines in the figure is written on the surface of the photoreceptor drum 1. Therefore, in this case, only this area will be irradiated with light from the LED array 26, so the AIDC mark 2 of the LED array 26 will be irradiated with light from the LED array 26.
1M tjl LED chip 2 corresponding to the upper position of 9
5 will be emitted (lit). Therefore, each time the controller 34 controls the amount of light emitted from these LED chips 25.

In order to detect the light emitted from the LED chip 25 at this time, a light receiving element 28 is placed at a marking position 28a indicated by diagonal lines in the figure, which corresponds to the upper part of the AIDC mark 29.
will be placed.

In this way, the position in the longitudinal direction of the light receiving element 28 is selected to correspond to the position in the longitudinal direction of the LED chi knob 25 that will emit light when no image forming operation is performed. Therefore, at the time of detection,
Since it is not necessary to cause the entire LED array 26 to emit light, power consumption can be saved accordingly. Also, the toner? '49 ffi can also be saved.

Note that when normal rotation development is performed, a plurality of LED chips 25 corresponding to positions other than the AIDC mask 29 portion will emit light.

In addition, the inter-image erase refers to an area that does not contribute to image formation in the circumferential direction of the photoreceptor drum 1 during regular development, that is, a region between the end position of the original image for - sheets and the start end position of the next original image. This refers to removing the residual charge on the photoreceptor drum 1 by irradiating light from the LED array onto the area formed between the photosensitive drums 1 and 1. - On the other hand, site erase refers to LE on both ends of the photoreceptor drum 1 in the axial direction that do not contribute to image formation.
This refers to irradiating light from the D array to remove residual charges on the photoreceptor drum.

Therefore, when detecting the light amount when performing the AIDC mark writing operation, inter-image erase, and site erase in normal rotation development, the L
Since the light from the ED chips 25 will be detected, the light receiving element 28 will be provided at a position corresponding to the arrangement position of these LED chips 25.

The light amount control during the above-mentioned AIDC mark writing operation is specifically performed according to the timing chart shown in FIG. That is, when a printer start switch (not shown) is turned on, the printing operation for one page of the original is performed for a predetermined time T shown in FIG. 4(a). During this process, the time T at the end, The time period corresponds to a time when no image formation is performed. Then the fourth
As shown in Figure (b), at the time when this image formation is not performed, the writing operation of the AIDC mark is performed for a time T2.

Then, as shown in FIG. 4(c), the corresponding LE is
The light amount of the D chip 25 is detected, and in accordance with this detection result, the controller 34 controls the light amount of the LED chip 25 when executing the next printing operation.

In order to show that such control is performed by the controller 34, FIG. 3 shows how the printer start command signal and the AIDC mark writing execution command signal are input to the controller 34.

u In the case of the present invention described above, the light amount of the LED array is controlled by detecting the direct light from the LED array and the reflected light from the end face of the convergent light transmission body using a light receiving element incorporated in the LED printer head. Therefore, accurate light amount detection can be performed without being affected by external factors (disturbances). Therefore, since the light amount can be controlled stably over a long period of time, there is an advantage that copy quality can be significantly improved.

Moreover, since the light intensity detection is performed at a time when no image forming operation is performed on the original image, such as during the AIDC mark writing operation, there is no problem with image formation, and there is no need to turn on the LED array unnecessarily. Since toner is not wasted, there is an advantage that power consumption and toner can be saved.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway side view showing an LED printer head according to the present invention together with a photoreceptor drum, and FIG.
3 is a block diagram showing the control system, and FIG. 4 is a timing chart showing the control operation. DESCRIPTION OF SYMBOLS 1... Photosensitive drum, 2... LED printer head, 21... Casing, 25... L. ED chip, 26... LED array, 27... Convergence light transmitter, 28... Light receiving element, 29... AIDC
? -ri, 32...microprocessor, 34...controller. Patent applicant Minolta Camera Co., Ltd.

Claims (2)

[Claims] (1) An LED printer head that exposes a charged object to light emitted from an LED array via a convergent light transmitter, the LED array and at least the proximal end of the convergent light transmitter being sealed in a casing. At the same time, a light-receiving element is arranged in a position that does not obstruct the optical path of the light in the casing, and the direct light from the LED array is emitted during a predetermined pattern corresponding to the time when image formation of the original image is not performed. An LED characterized in that the light reflected from the end face of the convergent light transmitter is detected by a light receiving element, and the amount of light emitted from the LED array is controlled based on the detection result.
printer head. (2) The LED printer head according to claim 1, wherein the predetermined pattern is a pattern for toner density control.