JPH0271285A - Electrophotographic device - Google Patents

Abstract

PURPOSE:To surely suppress scattering of carrier which is apt to occur at the time of starting a magnet roll by providing a means which controls the speed at the time of starting the magnet roll to gradually increase the rotative speed from the roll start time till arrival at a steady rotative speed. CONSTITUTION:A CPU 15 of a magnet roll controller 14 generates a magnet roll control signal when receiving a developing device start signal, and this control signal is converted to an analog signal by a D/A converter 16 and is inputted to a driver 17. The driver 17 drives a developing motor 18 based on the magnet roll control signal, and a magnet roll 4 is rotated and driven. In this case, the rotative speed of the magnet roll 4 is gradually increased at a certain acceleration until it reaches the steady rotative speed at a time T2 after the developing device is started at a time T1. The rotative speed of the magnet roll 4 is increased in this manner to suppress scattering of carrier.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electrophotographic apparatus such as an electrostatic transfer copying machine and a laser printer equipped with a developing device that uses a two-component developer. be.

[Conventional technology]

2. Description of the Related Art Conventional electrophotographic apparatuses are often equipped with a developing device containing a two-component developer consisting of toner and a carrier for transporting the toner. When developing an electrostatic latent image formed on a photoconductor, this type of developing device rotates a magnet roller (hereinafter referred to as a mag roller) to convey a carrier with toner attached, and forms a magnetic brush to remove the toner. It is designed to supply the photoreceptor. A ferrite carrier is usually used as the above carrier. This type of electrophotographic apparatus has a problem in that carrier scatters during a developing operation, although the amount varies depending on the apparatus.

That is, as shown in FIG. 8, the mag roller 4 of the developing device consists of a plurality of magnets 6... and a cylindrical non-magnetic sleeve 8 disposed around the outer periphery of the magnets 6... Either the magnets 6 are fixed and only the sleeve 8 rotates, or the magnets 6 and the sleeve 8 rotate together. At this time, the sleeve 8 rotates at high speed in either case. The developer is attracted to the surface of the sleeve 8 by the magnets 6, and is transported by the rotation of the sleeve 8 or the sleeve 8 and the magnet 6, and is supplied to the surface of the photoreceptor. At this time, the adsorption force of the developer to the sleeve 8 is determined by the magnetic force of the magnets 6 . . . , the saturation magnetization of the carrier, and the amount of developer attached to the surface of the sleeve 8 . On the other hand, as the mag roller 4 rotates, a centrifugal force acts on the developer, and a force in the direction of separating the carrier from the mag roller 4 acts on the developer. This force becomes larger as the rotational speed of the mag roller 4 increases, and the carrier becomes more likely to scatter. Further, such carrier scattering is most likely to occur when the mag roller 4 starts rotating. This is because the flow of the developer becomes non-uniform when the mag roller 4 is activated.

Furthermore, carrier scattering also occurs due to fluctuations in the mixing ratio of carrier to toner in the developer, and becomes more likely to occur when the mixing ratio of toner to carrier decreases, that is, when the toner concentration decreases. Unlike the above case, the carrier scattering in this case is mainly caused by the carrier adhering to the photoreceptor due to electrostatic force.

The above-mentioned carrier scattering and carrier adhesion to the photoreceptor not only reduce the quality of the image, but also cause dirt inside the electrophotographic device, scratches on the photoreceptor surface, and the like.
This may cause damage to the charger and even damage to the main body of the device.

Therefore, in conventional electrophotographic apparatuses, in order to prevent the carrier from scattering during development, the magnetic force of the magnet 6 of the mag roller 4 is increased, the saturation magnetization of the carrier is increased, or a magnet is installed to collect the scattered carrier. Measures are being taken, such as deploying.

[Problem to be solved by the invention]

However, the above-mentioned conventional configuration for preventing carrier scattering hinders the miniaturization and increase in speed of electrophotographic devices. The problem is that it is difficult to respond adequately.

[Means to solve the problem]

In order to solve the above-mentioned problem, an electrophotographic apparatus according to the invention as claimed in claim 1 contains a two-component developer consisting of a toner and a carrier, and is capable of forming an electrostatic latent image formed on a photoreceptor. In an electrophotographic apparatus equipped with a developing device that supplies developer to a photoconductor by a magnet roller rotated by a magnet roller drive means during development, from the time when the magnet roller is started until it reaches a steady rotation speed, The present invention is characterized by comprising a magnet roller start-up speed control means for controlling the magnet roller drive means so that the rotational speed of the magnet roller gradually increases.

In order to solve the above-mentioned problem, an electrophotographic apparatus according to the invention of claim 2 contains a two-component developer consisting of toner and carrier, and is capable of forming an electrostatic latent image formed on a photoreceptor. During development, the developing device is equipped with a developing device that supplies developer to the photoreceptor by a magnetic roller rotated by a magnetic roller driving device, and this developing device is provided with a toner concentration detecting device. When a decrease is detected, in an electrophotographic apparatus in which toner is supplied from a toner supply means to a developing device, the magnet roller drive means is gradually increased in rotation speed from when the magnet roller is started until it reaches a steady rotation speed. The present invention is characterized in that it includes a magnet roller start-up speed control means that controls the speed of the magnet roller to rise, and a toner supply control means that controls the toner supply means so that it operates only when the magnet roller is at a steady rotational speed.

[For production]

According to the structure of the electrophotographic apparatus according to the invention of claim 1, the magnet roller drive means is controlled by the magnet roller startup speed control means, so that the rotational speed of the magnet roller is maintained at a steady rotation from the time of startup. The rate of change in acceleration is gradually increased until the speed is reached.

Therefore, scattering of the carrier, which is most likely to occur when the magnet roller is activated, can be reliably suppressed.

According to the structure of the electrophotographic apparatus according to the invention of claim 2, the magnet roller drive means is controlled by the magnet roller startup speed control means, so that the rotational speed of the magnet roller is maintained at a steady rotation from the time of startup. The rate of change in acceleration is gradually increased until the speed is reached.

Furthermore, since the toner supply control means is controlled so that the toner supply means operates only when the magnet roller is at a steady rotation speed, the rotation of the magnet roller is stabilized and the flow of developer in the developing device becomes a steady flow. only when
Control of toner density is performed.

Therefore, scattering of the carrier, which is most likely to occur when the magnetor 1 roller is started, can be reliably suppressed. In addition, toner density control under unstable conditions can reliably prevent situations in which the toner density drops beyond the allowable range, causing carrier to adhere to the photoreceptor and further causing carrier scattering. be able to.

[Embodiment 1] An embodiment of the present invention will be described below based on FIGS. 1 to 5 and FIG. 8. For convenience of explanation, FIG. 8, which was used to explain the prior art, is used again.

The electrophotographic apparatus according to the present invention has a developing device 1, as shown in FIG. A two-component developer made of a mixture of toner and carrier is housed within a machine frame 2 of the developing device 1 . Further, in the machine frame 2, a first stirring roller 3 is disposed on the -blade side, and a developing magnet roller (hereinafter referred to as a mag roller) 4 is disposed on the other side, and the first stirring roller 3 and the mag roller 4 are arranged on the other side. A second stirring roller 5 is arranged between them.

The first stirring roller 3 described above is configured to stir and mix the carrier and toner supplied from a toner hopper 12, which will be described later, and the second stirring roller 5 is configured to stir and mix the carrier and toner supplied from a toner hopper 12, which will be described later.
The developer stirred in is conveyed to the mag roller 4 while being further stirred.

As shown in FIG. 8, the macro roller 4 has a plurality of N-pole and S-pole magnets 6 arranged at predetermined intervals, and has a cylindrical non-magnetic sleeve 8 around its outer periphery. ing. Then, either the sleeve 8 only rotates while the magnet 6... is fixed, or the magnet 6...
By rotating both the sleeve 8 and the magnet 6, the developer conveyed by the second stirring roller 5 is transferred to the magnet 6.
• The magnetic brush is attracted to the surface of the sleeve 8, forms a magnetic brush, and is supplied to the photosensitive drum 13, which will be described later. As shown in FIG. 1, the above-mentioned mag roller 4 is connected to a developing motor 18, which is a DC servo motor and serves as a magnet roller driving means for rotationally driving the mag roller 4 based on a drive signal from a driver 17, which will be described later. There is.

Above the mag roller 4 and the second stirring roller 5,
In order to maintain a constant mixing ratio of carrier and toner in the developing device 1, a toner concentration sensor 9 is provided to detect the concentration of toner.

This Tonacon sensor 9 has a support member 1 fixed to the machine frame 2.
attached to 0. At the tip of the support member 10,
A doctor 11 is formed to regulate the amount of developer conveyed by the sleeve 8 of the magnetic roller 4.

A toner hopper 12 for replenishing toner to the developing device 1 is provided above the first stirring roller 3 in the developing device 1 . The toner hopper 12 is configured to replenish toner through an opening 2a formed in the machine frame 2 when the toner concentration sensor 9 detects a decrease in toner concentration within the developing device 1.

Further, on the side of the mag roller 4 described above, a photosensitive drum 13 is disposed so as to face the mag roller 4 in close proximity through the opening 2b of the machine frame 2. This photosensitive drum 13 is exposed to light by an optical system section (not shown), so that
An electrostatic latent image corresponding to the image of the original is formed.

As shown in FIG. 1, the electrophotographic apparatus also includes a mag roller control device 1 as a magnet roller startup speed control means for controlling the rotational speed of the mag roller 4 at startup.
It is equipped with 4. This mag roller control device 14 is configured to:
A CPU that outputs a digital mag roller control signal when a developing device activation signal is input from a control means (not shown).
15, a D/A converter 16 that converts the mag roller control signal into an analog signal, and a developing motor 1 based on the analog mag roller control signal output from the D/A converter 16.
and a driver 17 that drives the 8.

As shown in FIG. 3, data for controlling the rotational speed of the mag roller 4 is input to the CPU 15, and the CPU 15 outputs a mag roller control signal based on this data. That is, the initial speed is V from the time T when the developing device is activated, which is the time when the developing device activation signal is manually inputted from the control means, until the time T2 when the steady rotation speed is reached after a predetermined period of time has elapsed. The rotation speed of the mag roller 4 is gradually increased from (-〇) at a constant acceleration, and after reaching the steady rotation speed T2, the mag roller 4 is controlled to rotate at a constant steady rotation speed VT. It has become.

In the above configuration, when the electrophotographic apparatus performs a copying operation, first, as shown in FIG. 4(a), the photoreceptor drum 13 starts rotating at T0 when the photoreceptor is activated. Then, a developing device activation signal is issued from the control means, and when this signal is input to the CPU 15 of the mag roller control device 14,
As shown in (c) of the figure, the developing motor 18 is activated at T1 when the developing device is activated, and the mag roller 4 starts rotating. Note that T, may be equal to T.

At this time, the CPU 15 of the mag roller control device 14 that has received the developing device activation signal issues a mag roller control signal, and this signal is converted into an analog signal by the D/A converter 16 and input to the driver 17. The driver 17 drives the developing motor 18 based on the above mag roller control signal,
The mag roller 4 is rotationally driven. Then, the rotational speed of the mag roller 4 gradually increases at a constant force u speed from the time T1 when the developing device is activated until it reaches the time T2 when the steady rotational speed is reached.

By increasing the rotational speed of the mag roller 4 in this manner, scattering of carriers is suppressed. On the other hand, developing bag W
1, a first stirring roller 3 and a second stirring roller 5 are also rotating, the first stirring roller 3 stirring the developer, and the second stirring roller 5 stirring the developer stirred by the first stirring roller 3. The agent is further stirred and conveyed to the mag roller 4.

After that, when the mag roller 4 reaches the steady rotation speed T2, as shown in FIG. The photoreceptor drum 13 is
is exposed to light, and an electrostatic latent image corresponding to the image of the original is formed on the photoreceptor drum 13. This electrostatic latent image is then developed with toner supplied from the magnetic roller 4, forming a toner image. This toner image is then transferred to transfer paper and fixed by a fixing device. The transfer paper on which the image has been transferred is discharged from the electrophotographic apparatus.

Next, when the amount of carrier scattering between the electrophotographic apparatus of the present invention and the conventional electrophotographic apparatus was compared, the results shown in FIG. 5 were obtained. The amount of carrier scattering was determined by making 50,000 copies with the inspection magnet 19 attached to the machine frame 2 below the mag roller 4 and the photoreceptor drum 13, as shown in Fig. 2. The investigation was carried out by collecting carriers adsorbed to the magnet 19. Note that the conventional electrophotographic apparatus used for comparison controls the speed of the mag roller 4 as shown in FIG. The mag roller 4 is operated at a constant rotation speed.

From the results shown in the figure, it was found that in the electrophotographic apparatus according to the present invention, the amount of carrier scattering was significantly reduced compared to the conventional electrophotographic apparatus.

[Embodiment 2] Another embodiment of the present invention will be described below based on FIGS. 6 and 7. For convenience of explanation, means having the same functions as the means shown in the drawings of the above-mentioned embodiment are denoted by the same reference numerals, and the explanation thereof will be omitted.

As shown in FIG. 6, the electrophotographic apparatus according to the present invention has C
The aforementioned mag roller control device 14 consisting of the PU 20, the D/A converter 16, and the driver 17, and the toner hopper as a toner supply control means that controls the toner hopper 12 as a toner supply means to operate only when the mag roller 4 is at a steady rotation speed. A control device 21 is provided. The toner hopper control device 21 includes a rotation speed detector 25 that detects the rotation speed of the developing motor 18, a CPU 20, and a CPU 20.
A D/A converter 22 that converts the toner hopper control signal output from the D/A converter 20 into an analog signal, and a driver 23 that drives the toner hopper motor 24 based on the analog toner hopper control signal output from the D/A converter 22. Become. In addition to the function of the CPU 15 described above, the CPU 20 outputs a mag roller control signal when a developing device activation signal is input from a control means (not shown) during development of an electrostatic latent image formed on the photoreceptor drum 13. Then, the toner container sensor 9 detects a lack of toner in the developing device 1, and the rotational speed detector 25 detects that the developing motor 18 is running low.
That is, it has a function of outputting a toner hopper control signal for operating the toner hopper motor 24 when the steady rotation speed of the mag roller 4 is detected.

In the above configuration, as shown in FIG. 7(a), the photoreceptor drum 13 starts rotating at T0 when the photoreceptor is activated,
As shown in FIG. 2C, when the developing motor 18 is activated at T when the developing device is activated, the mag roller 4 starts rotating. At this time, under the control of the mag roller control device 14, the rotation speed of the mag roller 4 gradually increases at a constant acceleration from the time T1 when the developing device is activated until it reaches the steady rotation speed T2. In this way, Magrolla 4
By increasing the rotational speed of the carrier, scattering of carriers is suppressed.

After that, when the mag roller 4 reaches the steady rotation speed at T2 when the steady rotation speed is reached, as shown in (b) of the figure,
The copy lamp of the optical system section is turned on, and copying is then performed through predetermined steps.

Further, when the rotation speed detector 25 detects the steady rotation speed state (T2 when the steady rotation speed is reached) of the mag roller 4, the toner hopper control device 2
1 processes the detection signal of the toner condenser sensor 9 as valid, and controls the toner hopper 12 in accordance with the detection signal of the toner condenser sensor 9. Here, when the toner concentration sensor 9 detects a decrease in the toner concentration in the developing device 1, the CP
A toner hopper control signal for operating the toner hopper 12 is output from U20, and this control signal is input to the driver 23 via the D/A converter 22. driver 2
3 drives the toner hopper motor 24 based on the input toner hopper control signal, and the toner hopper 12 is operated. As a result, toner is supplied to the developing device 1 from the toner hopper 12 . Treating the detection signal of the tonercon sensor 9 as valid is canceled at the same time as the development motor 18 is stopped.
After that, it is treated as invalid, and control based on the detection signal of the toner sensor 9 is no longer performed.

As described above, in the configuration in which the operation of the toner hopper 12 is controlled only when the mag roller 4 is rotating at a steady speed, the toner concentration detected in the stable state where the developer is in a steady flow in the developing device 1 is Since the operation of the toner hopper 12 is controlled based on this, the toner concentration can be stabilized. Therefore, adhesion of carrier to the surface of photoreceptor drum 13 due to a decrease in toner concentration and scattering of carrier due to this are suppressed.

Further, when the amount of carrier scattering in the electrophotographic apparatus of the present invention was measured, good results similar to those of the electrophotographic apparatus of Example 1 shown in FIG. 5 were obtained.

〔Effect of the invention〕

As described above, the electrophotographic apparatus of the invention of claim 1 has the following features:
Contains a two-component developer consisting of toner and carrier, and supplies the developer to the photoreceptor by a magnetic roller rotated by a magnetic roller driving means when developing an electrostatic latent image formed on the photoreceptor. In an electrophotographic apparatus equipped with a developing device, when the magnet roller is started, the magnet roller driving means is controlled so that the rotational speed of the magnet roller gradually increases from the time when the magnet roller is started until it reaches a steady rotational speed. This configuration includes speed control means.

Therefore, when developing the electrostatic latent image formed on the photoreceptor,
Since the rotational speed of the magnet roller gradually increases from the time of startup until it reaches a steady rotational speed, it is possible to reliably suppress scattering of the carrier, which is most likely to occur when the magnet roller is started. Therefore, problems such as deterioration of image quality, dirt inside the electrophotographic device, damage to the photoreceptor, damage to the charger, and damage to the device main body can be solved without hindering the miniaturization and speeding up of the electrophotographic device. This effect is achieved.

As described above, the electrophotographic apparatus of the invention of claim 2 has the following features:
Contains a two-component developer consisting of toner and carrier, and supplies the developer to the photoreceptor by a magnetic roller rotated by a magnetic roller driving means when developing an electrostatic latent image formed on the photoreceptor. In an electrophotographic apparatus including a developing device, the developing device is provided with a toner concentration detecting means, and when a decrease in toner concentration is detected by the toner concentration detecting means, toner is supplied from a toner supplying means to the developing device. , the above magnetic roller driving means,
A magnet roller startup speed control means for controlling the rotation speed of the magnet roller to gradually increase from the start of the magnet roller until it reaches a steady rotation speed, and a toner supply means that are operated only when the magnet roller is at a steady rotation speed. This configuration includes a toner supply control means for controlling the toner supply.

Therefore, like the electrophotographic apparatus of the invention of claim 1,
It is possible to reliably suppress carrier scattering, which is most likely to occur when the magnet roller is started. In addition, it is possible to stabilize the toner concentration control within the developing device, and it is possible to suppress the adhesion of carrier to the photoreceptor due to a decrease in toner concentration and the scattering of toner caused by this. .

Therefore, problems such as deterioration of image quality, dirt inside the electrophotographic device, damage to the photoreceptor, damage to the charger, and damage to the device main body can be solved without hindering the miniaturization and speeding up of the electrophotographic device. This effect is achieved.

[Brief explanation of the drawing]

1 to 5 show an embodiment of the present invention, in which FIG. 1 is a block diagram showing the configuration of the main parts of an electrophotographic device, and FIG. 2 is a schematic vertical cross-section showing a developing device. Figure, 3rd
FIG. 4 is a graph showing changes in the rotational speed of the magnet roller after activation; FIG. 4 is a timing chart showing the operation timings of the photosensitive drum, copy lamp, and developing motor; and FIG. 5 is a graph showing the electrophotographic apparatus according to the present invention. Graphs showing changes in carrier scattering amount with respect to the number of copies in a conventional electrophotographic apparatus, FIGS. 6 and 7 show other embodiments of the present invention, and FIG. 6 shows a main part of the electrophotographic apparatus. 7 is a timing chart showing the timing of the operation of the photosensitive drum, copy lamp and developing motor, and activation of the toner sensor. FIG. 8 is a diagram showing the electrophotographic apparatus of the present invention and the conventional electrophotographic apparatus. FIG. 3 is an explanatory diagram showing a magnet roller common to the device. (2) is a developing device, 4 is a magnet roller, 6 is a magnet, 8 is a sleeve, 12 is a toner hopper (toner supply means), 13 is a photosensitive drum (photosensitive member), 14 is a mag roller control device (magnet roller speed control means when starting) ), 1
5.20 is the CPU, 16.22 is the D/A converter, 17.
23 is a driver, 18 is a developing motor (magnetic roller driving means), 21 is a toner hopper control device (toner supply control means), 24 is a toner hopper motor, and 25 is a rotation speed detector.

Claims (1)

[Claims] 1. A magnetic roller containing a two-component developer consisting of toner and carrier and rotated by a magnetic roller driving means when developing an electrostatic latent image formed on a photoreceptor. In an electrophotographic apparatus equipped with a developing device that supplies developer to a photoreceptor, the magnetic roller is driven so that the rotational speed of the magnetic roller gradually increases from the time when the magnetic roller is started until it reaches a steady rotational speed. 1. An electrophotographic apparatus comprising: a magnet roller start-up speed control means for controlling the speed of the magnet roller. 2. Contains a two-component developer consisting of toner and carrier, and when developing an electrostatic latent image formed on the photoreceptor, the developer is transferred to the photoreceptor by a magnetic roller rotated by a magnetic roller drive means. The electrophotographic apparatus includes a developing device for supplying toner, the developing device is provided with a toner concentration detecting means, and when a decrease in toner concentration is detected by the toner concentration detecting means, toner is supplied from the toner supplying means to the developing device. In the apparatus, the magnet roller drive means is controlled by a magnet roller start-up speed control means for controlling the magnet roller drive means such that the rotation speed gradually increases from the start of the magnet roller until it reaches a steady rotation speed, and the toner supply means is a magnetic roller. 1. An electrophotographic apparatus comprising: a toner supply control means that is controlled to operate only when the roller is at a steady rotational speed.