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The operating principle of a Samsung laser printer. The world of PC peripherals. Principles of color printing

Today I want to talk about device and operating principle of a laser printer. Everyone is familiar with this device, but few know about the principle of its operation and the reasons for its malfunctions. In this article I will try to clearly explain the principle of operation of “laser printers”, and in subsequent articles about malfunctions of laser printers, the reason for their occurrence, and how to eliminate them.

Laser printer device

The operation of any modern laser printer is based on photoelectricprinciple xerography. Based on this method, all laser printers are structurally composed of three main parts (assemblies):

- Laser sanitation unit.

- Image transfer unit.

- Image fixing unit.

The image transfer unit usually means a laser printer cartridge and a charge transfer roller (Transferroller) in the printer itself. We will talk about the structure of the laser cartridge in more detail later, but in this article we will consider only the operating principle. It should also be noted that instead of laser scanning in some printers (mainly OKІ» ) LED scanning is used. It performs the functionseHowever, only the role of a laser is performed by LEDs.

For example, consider laser printer HP LaserJet 1200 (Fig. 1). The model is quite successful and has proven itself with a long service life, convenience and reliability.

We print on some material (mostly paper), and the paper feed unit is responsible for sending it to the “mouth” of the printer. As a rule, it is divided into two types that are structurally different from each other. Bottom Tray Feed Mechanism, is called - Tray 1, and feed mechanism from the top(bypass) - Tray 2. Despite the design differences in their composition, they have (see Fig. 3):

- Paper Pickup Roller- needed to pull paper into the printer,

- Brake pad and separator block required to separate and pick up only one sheet of paper.

Directly involved in image formation printer cartridge(Fig. 4) and laser scanning unit.

A laser printer cartridge consists of three main elements (see Fig. 4):

Photocylinder,

Precharge shaft,

Magnetic shaft.

Photocylinder

Photocylinder(ORS- organicphotoconductivedrum), or also photoconductor, is an aluminum shaft coated with a thin layer of photosensitive material, which is additionally covered with a protective layer. Previously, photocylinders were made based on selenium, which is why they were also called selenium shafts, they are now made from photosensitive organic compounds, but their old name is still widely used.

Main property photocylinder– change conductivity under the influence of light. What does it mean? If any charge is given to the photocylinder, it will remain charged for quite a long time, but if its surface is illuminated, then in places where it is illuminated, the conductivity of the photo coating increases sharply (resistance decreases), the charge “flows” from the surface of the photocylinder through the conductive inner layer and in this place A neutrally charged area will appear.

Rice. 2 HP 1200 laser printer with cover removed.

The numbers indicate: 1 - Cartridge; 2 - Image transfer unit; 3 - Image fixing unit (stove).

Rice. 3 Paper feed unitTray 2 , view from the back s.

1 - Paper pickup roller; 2 - Braking platform (blue stripe) with a separator (not visible in the photo); 3 - Charge transfer roller (transferroller), transmitting paper has a static charge.

Rice. 4 Laser printer cartridge in disassembled condition.

1- Photocylinder; 2- Pre-charge shaft; 3- Magnetic shaft.

Image overlay process.

Photocylinder using a pre-charge shaft (PCR) receives an initial charge (positive or negative). The amount of charge itself is determined by the printer's print settings. After the photocylinder is charged, the laser beam passes over the surface of the rotating photocylinder, and the illuminated areas of the photocylinder become neutrally charged. These neutral areas correspond to the desired image.

The laser scanning unit consists of:

Semiconductor laser with focusing lens,
- Rotating mirror on the motor,
- Groups of forming lenses,
- Mirrors.

Rice. 5 Laser scanning unit with cover removed.

1,2 - Semiconductor laser with focusing lens; 3- Rotating mirror; 4- Group of forming lenses; 5- Mirror.

The drum has direct contact magnetic shaft m (Magneticroller), which supplies toner from the cartridge hopper to the photo cylinder.

The magnetic shaft is a hollow cylinder with a conductive coating, inside which a permanent magnet rod is inserted. The toner located in the hopper in the hopper is attracted to the magnetic shaft under the influence of the magnetic field of the core and an additionally supplied charge, the value of which is also determined by the printer’s printing settings. This determines the density of future printing. From the magnetic shaft, under the influence of electrostatics, the toner is transferred to the image formed by the laser on the surface of the photocylinder, since it has an initial charge; it is attracted to the neutral areas of the photocylinder and repelled from equally charged ones. This is the image we need.

It is worth noting here two main mechanisms for creating an image. Most printers (HP,Canon, Xerox) a toner with a positive charge is used, remaining only on the neutral surfaces of the photo cylinder, that is, the laser illuminates only those areas where the image should be. In this case, the photo cylinder is charged negatively. The second mechanism (used in printersEpson, Kyocera, Brother) is the use of a negatively charged tuner, and the laser discharges areas of the photo cylinder where there should be no toner. The photocylinder initially receives a positive charge and the negatively charged toner is attracted to the positively charged areas of the photocylinder. Thus, in the first case, a finer rendering of details is obtained, and in the second, a more dense and uniform filling. Knowing these features, you can more accurately choose a printer to solve your problems (printing text or printing sketches).

Before contacting the photocylinder, the paper also receives a static charge (positive or negative) using the charge transfer roller (Transferroller). This static charge causes the toner to transfer from the photo cylinder to the paper during contact. Immediately after this, the static charge neutralizer removes this charge from the paper, which eliminates the attraction of the paper to the photo cylinder.

Toner

Now we need to say a few words about toner. Toner is a finely dispersed powder consisting of polymer balls coated with a layer of magnetic material. The color tuner also contains dyes. Each company in its models of printers, MFPs and copiers uses original toners that differ in dispersion, magnetnspine and physical properties. Therefore, under no circumstances should you refill cartridges with random toners, otherwise you can very quickly ruin your printer or MFP (tested by experience).

If, after passing the paper through the laser scanning unit, we remove the paper from the printer, we will see an already formed image, which can be easily destroyed by touch.

Image fixation unit or “stove”

In order for the image to become durable it needs fix. Freezing the image occurs with the help of additives included in the toner that have a certain melting point. The third main element of the laser printer is responsible for fixing the image (Fig. 6) - image fixation unit or “stove”. From a physical point of view, fixation is carried out by pressing molten toner into the paper structure and then solidifying it, which gives the image durability and good resistance to external influences.

Rice. 6 Image fixation unit or stove. At the top is the assembled view, at the bottom with the paper separator strip removed.

1 - Thermal film; 2 - Pressure shaft; 3 - Paper separator bar.

Rice. 7 Heating element and thermal film.

Structurally, the “stove” can consist of two shafts: the upper one, inside of which there is a heating element, and the lower shaft, which is necessary for pressing the melted toner into the paper. In the HP 1200 printer in question, the “stove” consists of thermal films(Fig. 7) - a special flexible, heat-resistant material, inside of which there is a heating element, and a lower pressure roller, which presses the paper due to the support spring. Monitors the temperature of the thermal film temperature sensor(thermistor). Passing between the thermal film and the pressure roller, at the points of contact with the thermal film, the paper heats up to approximately 200° C˚ . At this temperature, the toner melts and is pressed into liquid form into the texture of the paper. To prevent the paper from sticking to the thermal film, there are paper separators at the oven exit.

This is what we actually looked at - "how does a printer work". This knowledge will help us in the future to find out the causes of breakdowns and eliminate them. But in no case should you get into the printer yourself if you are not sure that you can fix it, this will only make it worse. It’s better not to save money, but to entrust this matter to professionals, because buying a new printer will cost you much more.

Includes seven sequential operations to create a given image on a sheet of paper. This is a very interesting and technological process that can be divided into two main stages: applying the image and fixing it. The first stage is associated with the operation of the cartridge, the second takes place in the fusing unit (oven). As a result, in a matter of seconds we get the image we are interested in on a white sheet of paper.

So, what happens in such a short period of time in the printer? Let's figure this out.

Charge

Let us remember that toner is a finely dispersed substance (5-30 microns), and its particles very easily accept any electrical charge.

In the cartridge, the charge roller ensures uniform transfer of negative charge to the photodrum. This happens when the charge roller is pressed against the photodrum, and rotating in one direction (while uniformly imparting a negative static charge to the photodrum), causes it to rotate in the other.

Thus, the surface of the photodrum has a negative charge evenly distributed over the area.

Exhibition

In the next process, the future image is exposed on a photodrum.

This happens thanks to a laser. When a laser beam hits the surface of the photodrum, it removes the negative charge in this place (the point becomes neutrally charged). Thus, the laser beam forms the future image according to the specified coordinates in the program. Exclusively in those places where it is necessary.

This way we get the exposed part of the image in the form of negatively charged dots on the surface of the photodrum.

Development

Next, toner is applied to the exposed image on the surface of the photodrum in an even thin layer using a developing roller. The toner particles take on a negative charge and form a future image on the surface of the drum.

Transfer

The next step is to transfer the negatively charged toner image from the drum to a blank sheet of paper.

This occurs when the transfer roller comes into contact with a sheet of paper (the sheet passes between the transfer roller and the image drum). The transfer roller has a high positive potential, causing all the negatively charged toner particles (in the form of an image formed) to be transferred to the sheet of paper.

Consolidation

The next step in laser printing is to fix an image from a toner onto a sheet of paper in a fusing unit (in the oven).

At its core, this is the process of “baking” onto paper. A sheet of toner, passing between a thermal roller and a pressure roller, is subjected to thermo-baric (temperature and pressure) treatment, as a result of which the toner is fixed on the sheet and becomes resistant to external mechanical influences.

In our picture you see a thermal shaft and a pressure roller. Thermal roll is used in a number of laser printing devices. A halogen lamp is used inside the thermal shaft, which provides heating (heating element).

There are other models of laser printing devices, where thermal film is used instead of a thermal roller (as a heating element). The difference between them is that the halogen heater takes longer to operate. It is worth noting the fact that devices with thermal film are very susceptible to mechanical influences from foreign objects (paper clips, staples from a stapler) on a sheet of paper. This is fraught with failure of the thermal film itself. She is very sensitive to damage.

Cleaning

Since during this whole process a small amount of toner remains on the surface of the photodrum, a squeegee (cleaning blade) is installed in the cartridge to clean residual microparticles of toner from the photodrum shaft.

As it rotates, the shaft is cleaned. The residual powder ends up in the waste toner bin.

Removing charge

During the last stage, the photodrum shaft comes into contact with the charge roller. This leads to the fact that the “map” of negative charge is again aligned on the surface of the drum (up to this point, both negatively charged places and neutrally charged ones remained on the surface - they were the projection of the image).

Thus, the charge roller again imparts a uniformly distributed negative potential to the surface of the photodrum.

This ends the cycle of printing one sheet.

Conclusion

Thus, laser printing technology includes seven successive stages of transferring and fixing an image on paper. On modern devices, this process of printing one image on A4 paper takes only a matter of seconds.

When worn out internal parts, such as the photodrum, charge roller or magnetic shaft, are replaced. These components are located inside the cartridge, and you can see them in the picture above. Due to wear of these elements, print quality deteriorates significantly.

A little about the history of laser printing

And finally, a little about the development of laser printing technology. Surprisingly, laser printing technology appeared earlier, for example, the same matrix printing technology. Chester Carlson invented a printing method called electrography in 1938. It was used in photocopiers of that time (60-70s of the last century).

The very development and creation of the first laser printer was directed by Gary Starkweather. He was an employee of Xerox. His idea was to use copier technology to create a printer.

First appeared in 1971 first laser printer Xerox company. It was called the Xerox 9700 Electronic Printing System. Serial production was launched later - in 1977.

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IN article is being considered principle actions and device modern laser printers. She opens series articles, dedicated principles and problems laser boards.

The image obtained using modern laser printers (as well as matrix and inkjet printers) consists of dots. The smaller these dots and the more frequently they are located, the higher the image quality. The maximum number of dots that a printer can print separately on a 1-inch (25.4 mm) section is called resolution and is characterized in dots per inch, and the resolution can be 1200 dpi or more. The quality of text printed on a laser printer with a resolution of 300 dpi is approximately the same as typographical. However, if the page contains drawings containing shades of gray, then to obtain a high-quality graphic image you will need a resolution of at least 600 dpi. With a printer resolution of 1200 dpi, the print is almost photographic quality. If you need to print a large number of documents (for example, more than 40 sheets per day), a laser printer seems to be the only reasonable choice, since for modern personal laser printers the standard parameters are a resolution of 600 dpi and a print speed of 8...1 2 pages per minute.

OPERATING PRINCIPLE OF A LASER PRINTER

The laser printer was first introduced by Hewlett Packard. It used the electrographic principle of creating images - the same as in photocopiers. The difference was in the method of exposure: in photocopiers it occurs using a lamp, and in laser printers, lamp light replaced the laser beam.

The heart of a laser printer is an Organic Photo Conductor, often called a print drum or simply a drum. It is used to transfer images onto paper. The photodrum is a metal cylinder coated with a thin film of photosensitive semiconductor. The surface of such a cylinder can be provided with a positive or negative charge, which remains until the drum is illuminated. If any part of the drum is exposed, the coating becomes conductive and charge flows away from the illuminated area, creating an uncharged zone. This is a key point in understanding how a laser printer works.

Another important part of the printer is the laser and the optical-mechanical system of mirrors and lenses that moves the laser beam along the surface of the drum. The small-sized laser generates a very thin beam of light. Reflecting from rotating mirrors (usually tetrahedral or hexagonal), this beam illuminates the surface of the photodrum, removing its charge at the exposure point.

To obtain a spot image, the laser is turned on and off using a control microcontroller. The rotating mirror turns the beam into a line of latent image on the surface of the photodrum.

After a line is formed, a special stepper motor rotates the drum to form the next one. This offset corresponds to the printer's vertical resolution and is typically 1/300 or 1/600 inch. The process of forming a latent image on a drum is reminiscent of the formation of a raster on a television monitor screen.

Two main methods of preliminary (primary) charging of the surface of the photocylinder are used:

Ø using a thin wire or mesh called “corona wire”. High voltage, applied to the wire, leads to the appearance of a luminous ionized area around it, which is called the corona, and gives the drum the necessary static charge;

Ø using pre-charged rubber shaft(PCR).

So, an invisible image in the form of statically discharged dots is formed on the drum. What's next?

DEVICECARTRIDGE

Before we talk about the process of transferring and fixing an image on paper, let’s look at the device of the cartridge for the Laser Jet 5L printer from Hewlett Packard. This typical cartridge has two main compartments: the waste toner compartment and the toner compartment.

Main structural elements of the waste toner compartment:

1 - Image drum(Organic Photo Conductor (OPC) Drum). It is an aluminum cylinder coated with an organic photosensitive and photoconductive material (usually zinc oxide) that is capable of retaining the image created by the laser beam;

2 - Shaft primary charge(Primary Charge Roller (PCR)). Provides a uniform negative charge to the drum. Made from a conductive rubber or foam base applied to a metal shaft;

3 - « Viper» , squeegee, cleaning blade(Wiper Blade, Cleaning Blade). Clears the drum of any remaining toner that has not been transferred to the paper. Structurally, it is made in the form of a metal frame (stamping) with a polyurethane plate (blade) at the end;

4 - Blade cleaning (Recovery Blade). Covers the area between the drum and waste toner box. Recovery Blade passes the toner remaining on the drum into the hopper and prevents it from spilling out in the opposite direction (from the hopper onto the paper).

Main structural elements of the toner compartment:

1 - Magnetic shaft(Magnetic Developer Roller, Mag Roller, Developer Roller). It is a metal tube, inside of which there is a stationary magnetic core. Toner is attracted to the magnetic shaft, which, before being supplied to the drum, acquires a negative charge under the influence of direct or alternating voltage;

2 - « Doctor» (Doctor Blade, Metering Blade). Provides uniform distribution of a thin layer of toner on the magnetic roller. Structurally, it is made in the form of a metal frame (stamping) with a flexible plate (blade) at the end;

3 - Sealing blade magnetic shaft(Mag Roller Sealing Blade). A thin plate similar in function to the Recovery Blade. Covers the area between the magnetic roller and the toner supply compartment. Mag Roller Sealing Blade allows toner remaining on the magnetic roller to flow into the compartment, preventing toner from leaking backwards;

4 - Bunker For toner (Toner Reservoir). Inside it is the “working” toner, which will be transferred to the paper during the printing process. In addition, a toner activator (Toner Agitator Bar) is built into the hopper - a wire frame designed for mixing toner;

5 - Seal, check (Seal). In a new (or regenerated) cartridge, the toner hopper is sealed with a special seal that prevents toner from spilling during transportation of the cartridge. This seal is removed before use.

PRINCIPLE OF LASER PRINTING

The picture shows a cross-section of the cartridge. When the printer turns on, all components of the cartridge begin to move: the cartridge is prepared for printing. This process is similar to the printing process, but the laser beam is not turned on. Then the movement of the cartridge components stops - the printer goes into a ready-to-print state.

After sending a document for printing, the following processes occur in the laser printer cartridge:

Charger drum. The Primary Charge Roller (PCR) uniformly transfers a negative charge to the surface of the rotating drum.

Exhibition. The negatively charged surface of the drum is exposed to the laser beam only in those places where the toner will be applied. When exposed to light, the photosensitive surface of the drum partially loses its negative charge. Thus, the laser exposes a latent image to the drum in the form of dots with a weakened negative charge.

Application toner. At this stage, the latent image on the drum is converted into a visible image with the help of toner, which will be transferred to paper. The toner located near the magnetic roller is attracted to its surface under the influence of the field of the permanent magnet from which the core of the roller is made. When the magnetic shaft rotates, the toner passes through a narrow slot formed by the “doctor” and the shaft. As a result, it acquires a negative charge and sticks to those areas of the drum that were exposed. “Doctor” ensures uniform application of toner onto the magnetic roller.

Transfer toner on paper. Continuing to rotate, the drum with the developed image comes into contact with the paper. WITH reverse side the paper is pressed against the Transfer Roller, which carries a positive charge. As a result, negatively charged toner particles are attracted to the paper, which produces an image “sprinkled” with toner.

Consolidation Images. A sheet of paper with an unfixed image is moved to a fixing mechanism, which consists of two contacting shafts, between which the paper is pulled. The Lower Pressure Roller presses it against the Upper Fuser Roller. The top roller is heated, and when it touches it, the toner particles melt and adhere to the paper.

Cleaning drum. Some toner does not transfer to the paper and remains on the drum, so it needs to be cleaned. This function is performed by the “viper”. All toner remaining on the drum is removed by a wiper into the waste toner bin. At the same time, the Recovery Blade covers the area between the drum and the hopper, preventing toner from spilling onto the paper.

"Erase" Images. At this stage, the latent image created by the laser beam is “erased” from the surface of the drum. Using the primary charge shaft, the surface of the photodrum is evenly “covered” with a negative charge, which is restored in those places where it was partially removed under the influence of light.

The history of laser printers began in 1938 with the development of dry ink printing technology. Chester Carlson, working on the invention of a new way to transfer images to paper, used static electricity. The method was called electrography and was first used by the Xerox corporation, which released the Model A copier in 1949. However, for this mechanism to work, certain operations had to be performed manually. Ten years later, the fully automatic Xerox 914 was created, which is considered the prototype of modern laser printers.

The idea of "drawing" what would later be printed directly onto the copy drum with a laser beam came from Gary Starkweather. Since 1969, the company has been developing and in 1977 released the Xerox 9700 serial laser printer, which printed at a speed of 120 pages per minute.

The device was very large, expensive, and intended exclusively for enterprises and institutions. And the first desktop printer was developed by Canon in 1982, a year later - new model LBP-CX. HP, as a result of cooperation with Canon, began production of the Laser Jet series in 1984 and immediately took a leading position in the market of laser printers for home use.

Currently, monochrome and color printing devices are produced by many corporations. Each of them uses its own technologies, which can vary significantly, but the general principle of operation of a laser printer is typical for all devices, and the printing process can be divided into five main stages.

Drum charge

The print drum (Optical Photoconductor, OPC) is a metal cylinder coated with a photosensitive semiconductor on which an image is formed for subsequent printing. Initially, the OPC is supplied with a charge (positive or negative). This can be done in one of two ways using:

corotron (Corona Wire), or coronator;
charge roller (Primary Charge Roller, PCR), or charging shaft.

A corotron is a block of wire and a metal frame around it.

Corona wire is a tungsten filament coated with carbon, gold or platinum. Under the influence of high voltage, a discharge occurs between the wire and the frame, a luminous ionized area (corona), an electric field is created that transfers a static charge to the photodrum.

Usually a mechanism is built into the unit that cleans the wire, since its contamination greatly impairs the print quality. Using a corotron has certain disadvantages: scratches, accumulation of dust, toner particles on the filament or its bending can lead to an increase in the electric field in this place, a sharp decrease in the quality of printouts, and possibly damage to the surface of the drum.

In the second option, a flexible film made of special heat-resistant plastic wraps the supporting structure with a heating element inside. The technology is considered less reliable and is used in printers for small businesses and home use, where heavy equipment loads are not expected. To prevent the sheet from sticking to the stove and twisting it around the shaft, a strip with paper separators is provided.

Color print

Four primary colors are used to form a color image:

black,
yellow,
purple,
blue.

Printing is carried out on the same principle as black and white, but first the printer splits the image that needs to be obtained into monochrome images for each color. During operation, color cartridges transfer their designs onto paper, and their superimposition on each other gives the final result. There are two color printing technologies.

Multipass

This method uses an intermediate carrier - a roller or toner transfer ribbon. In one revolution, one of the colors is applied to the tape, then another cartridge is fed to the desired location and the second is superimposed on top of the first image. In four passes, a complete image is formed on the intermediate medium and transferred to paper. The printing speed of color images in printers using this technology is four times slower than monochrome.

Single pass

The printer includes a complex of four separate printing mechanisms under general management. The color and black cartridges are lined up, each with a separate laser unit and transfer roller, and the paper runs under the drums, sequentially collecting all four monochrome images. Only after this does the sheet go into the oven, where the toner is fixed on the paper.

Have fun typing.

Laser printers are less demanding on paper than, for example, inkjet printers, and the cost of printing one page text document theirs is several times lower. At the same time, inexpensive models of laser and LED monochrome printers are already able to compete in price with high-quality color printers. inkjet printers.

Most laser printers on the market are designed for black and white printing; Color laser printers are quite expensive and are aimed at corporate users.

Laser printers print on any thick paper (from 60 g/m2) at a speed of 6 to... (this figure is constantly growing) sheets per minute (ppm – page per minutes), while the resolution can be 1200 dpi or more. The quality of text printed on a laser printer with a resolution of 300 dpi is approximately the same as typographical. However, if the page contains drawings containing gradations of gray color, then to obtain high-quality graphic image A resolution of at least 600 dpi will be required. With a printer resolution of 1200 dpi, the print is almost photographic quality. If you need to print a large number of documents (for example, more than 40 sheets per day), a laser printer seems to be the only reasonable choice, since for modern personal laser printers the standard parameters are a resolution of 600 dpi and a print speed of 8...12 pages per minute.

OPERATING PRINCIPLE OF A LASER PRINTER

The laser printer was first introduced by Hewlett Packard. It used the electrographic principle of creating images - the same as in photocopiers. The difference was in the method of exposure: in copiers it occurs using a lamp, and in laser printers, lamp light replaced the laser beam (Fig. 1).

Rice. 1. Laser printer device

The heart of a laser printer is a photoconductive cylinder (Organic Photo Conductor), which is often called a printing drum or simply a drum. It is used to transfer images onto paper. The photodrum is a metal cylinder coated with a thin film of photosensitive semiconductor. The surface of such a cylinder can be provided with a positive or negative charge, which remains until the drum is illuminated. If any part of the drum is exposed, the coating becomes conductive and charge flows away from the illuminated area, creating an uncharged zone. This is a key point in understanding how a laser printer works.

To obtain a spot image, the laser is turned on and off using a control microcontroller. The rotating mirror turns the beam into a line of latent image on the surface of the photodrum.

Two main methods of preliminary (primary) charging of the surface of the photocylinder are used:
using a thin wire or mesh called "corona wire". The high voltage applied to the wire creates a glowing ionized area around it, called a corona, and gives the drum the necessary static charge;
using a pre-charged rubber roller (PCR).

So, an invisible image in the form of statically discharged dots is formed on the drum. What's next?

CARTRIDGE DESIGN

The main structural elements of the waste toner compartment (Fig. 2):

1 – Organic Photo Conductor (OPC) Drum. It is an aluminum cylinder coated with an organic photosensitive and photoconductive material (usually zinc oxide) that is capable of retaining the image created by the laser beam;

2 – Primary Charge Roller (PCR). Provides a uniform negative charge to the drum. Made from a conductive rubber or foam base applied to a metal shaft;

3 – “Wiper”, squeegee, cleaning blade (Wiper Blade, Cleaning Blade). Clears the drum of any remaining toner that has not been transferred to the paper. Structurally, it is made in the form of a metal frame (stamping) with a polyurethane plate (blade) at the end;

4 – Recovery Blade. Covers the area between the drum and waste toner box. Recovery Blade passes the toner remaining on the drum into the hopper and prevents it from spilling out in the opposite direction (from the hopper onto the paper).

The main structural elements of the toner compartment (see Fig. 3):

1 – Magnetic shaft (Magnetic Developer Roller, Mag Roller, Developer Roller). It is a metal tube, inside of which there is a stationary magnetic core. The toner is attracted to the magnetic roller, which, before being supplied to the drum, acquires a negative charge under the influence of direct or alternating voltage;

2 – “Doctor” (Doctor Blade, Metering Blade). Provides uniform distribution of a thin layer of toner on the magnetic roller. Structurally, it is made in the form of a metal frame (stamping) with a flexible plate (blade) at the end;

3 – Mag Roller Sealing Blade. A thin plate similar in function to the Recovery Blade. Covers the area between the magnetic roller and the toner supply compartment. Mag Roller Sealing Blade allows toner remaining on the magnetic roller to flow into the compartment, preventing toner from leaking backwards;

4 – Toner Reservoir. Inside it is the “working” toner, which will be transferred to the paper during the printing process. In addition, a toner activator (Toner Agitator Bar) is built into the hopper - a wire frame designed for mixing toner;

5 – Seal, check (Seal). In a new (or regenerated) cartridge, the toner hopper is sealed with a special seal that prevents toner from spilling during transportation of the cartridge. This seal is removed before use.

PRINCIPLE OF LASER PRINTING

In Fig. Figure 4 shows a sectional view of the cartridge. When the printer turns on, all components of the cartridge begin to move: the cartridge is prepared for printing. This process is similar to the printing process, but the laser beam is not turned on. Then the movement of the cartridge components stops - the printer enters the Ready state.

Rice. 4. Sectional view of the cartridge

After sending a document for printing, the following processes occur in the laser printer cartridge:
Charging the drum (Fig. 5). The Primary Charge Roller (PCR) uniformly transfers a negative charge to the surface of the rotating drum.

Rice. 5. Charging the drum

Exposure (Fig. 6). The negatively charged surface of the drum is exposed to the laser beam only in those places where the toner will be applied. When exposed to light, the photosensitive surface of the drum partially loses its negative charge. Thus, the laser exposes a latent image to the drum in the form of dots with a weakened negative charge.

Rice. 6. Exposure

Applying toner (Fig. 7). At this stage, the latent image on the drum is converted into a visible image with the help of toner, which will be transferred to paper. The toner located near the magnetic roller is attracted to its surface under the influence of the field of the permanent magnet from which the core of the roller is made. When the magnetic shaft rotates, the toner passes through a narrow slot formed by the “doctor” and the shaft. As a result, it acquires a negative charge and sticks to those areas of the drum that were exposed. “Doctor” ensures uniform application of toner onto the magnetic roller.

Rice. 7. Applying toner

Transferring toner to paper (Fig. 8). Continuing to rotate, the drum with the developed image comes into contact with the paper. On the reverse side, the paper is pressed against the Transfer Roller, which carries a positive charge. As a result, negatively charged toner particles are attracted to the paper, which produces an image “sprinkled” with toner.

Rice. 8. Transferring toner to paper

Fixing the image (Fig. 9). A sheet of paper with a loose image is moved to a fixing mechanism, which consists of two contacting shafts, between which the paper is pulled. The Lower Pressure Roller presses it against the Upper Fuser Roller. The top roller is heated, and when it touches it, the toner particles melt and adhere to the paper.

Rice. 9. Pin the image

Cleaning the drum (Fig. 10). Some toner does not transfer to the paper and remains on the drum, so it needs to be cleaned. This function is performed by the “viper”. All toner remaining on the drum is removed by a wiper into the waste toner bin. At the same time, the Recovery Blade covers the area between the drum and the hopper, preventing toner from spilling onto the paper.

Rice. 10. Cleaning the drum

“Erasing” the image (Fig. 11). At this stage, the latent image created by the laser beam is “erased” from the surface of the drum. Using the primary charge shaft, the surface of the photodrum is evenly “covered” with a negative charge, which is restored in those places where it was partially removed under the influence of light.

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