JPH047516B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a copying machine, and more specifically, the present invention relates to a copying machine, and more specifically, each mechanism for charging, exposing, developing, transferring, separating, neutralizing, and cleaning provided around a photosensitive member is constructed by using a combination of devices, and The present invention relates to a proposal for a copying machine that is devised so that high image quality can be obtained without reducing cleaning performance.

As is well known, a single copying process is completed by a copying machine through the steps of charging, exposure, development, transfer, separation, neutralization, and cleaning. For this reason, conventional copying machines are provided with separate mechanisms for carrying out each of the above steps around the photosensitive member. However, charging
If each mechanism, such as exposure, is installed separately, there are problems such as the large number of mechanisms, which makes it difficult to downsize the device due to the need to secure installation space for each mechanism, and also makes it difficult to reduce the cost of the device. . Therefore,
In order to solve these problems, efforts are currently being made to use devices in combination, such as using the magnetic brush used in the developing mechanism in combination with the cleaning mechanism.

However, when such a developing/cleaning mechanism is used in combination, problems with copying performance such as deterioration of image quality may occur. That is, the rotating direction of the photosensitive member and the sliding direction of the magnetic brush are opposite directions (for example, when the photosensitive member is in the direction a in FIG. 1, the magnetic brush roller is in the c direction. Hereinafter, this directional relationship will be referred to as the forward direction.) If it is,
It is well known that high image quality can be obtained, but
If a magnetic brush is used in combination as described above, the cleaning effect cannot be expected to be very effective, and as a result, the quality of the copied image will deteriorate.

In view of these points, the present invention not only uses a magnetic brush developing mechanism and a cleaning mechanism in combination, but also uses devices that can be used in combination with each mechanism as much as possible to reduce costs. This technology aims to improve image quality by skillfully controlling the cleaning effect and improving the cleaning effect.

Hereinafter, one embodiment of the present invention will be described based on the drawings. FIG. 1 shows the overall structure of a copying machine as an embodiment of the present invention. Reference numeral 1 denotes the body of the copying machine, on which is provided a document mounting table 4 consisting of a contact glass 2 and a document holder 3. There is. This document mounting table 4
can be moved left and right, and when you press the print button (not shown), it first moves a certain amount to the left from the position shown in the figure to the exposure scanning start position (hereinafter referred to as "reversal"), and then starts exposure scanning and moves to the right ( (hereinafter referred to as normal rotation)
do. The forward rotation amount is an amount relative to the length of the copy paper, and when the copy paper rotates forward by that amount, it returns to the home position, which is the illustrated position. That is, the original table 4
performs a so-called random return.

Inside the copying machine body 1, an endless photosensitive belt 5 is wound between a driving roller 6 and a driven roller 7 as a photosensitive member provided with a photoconductive layer.
As shown in FIG. 2, a motor 8 capable of forward and reverse rotation is directly connected to the drive roller 6 (or may be connected via a gear). When the motor 8 rotates in the normal direction, the photoreceptor belt 5 rotates in the direction of arrow a in FIG. 1 (normal rotation).
When the motor reverses, it rotates in direction b (reverse rotation). On the other hand, a disc 10 having a large number of slits 9 cut out in the circumference is provided at the shaft end of the driven roller 7.
The amount of rotation of the photoreceptor belt 5 is detected by a detection element 11 incorporating a light emitter and a light receiver.

An optical system 12 is provided around the photoreceptor belt 5 to irradiate (expose) the photoreceptor belt 5 with an optical image of a document placed on the document table 4 to form an electrostatic latent image. There is. From the exposure position A of this optical system, in the normal rotation direction a of the photoreceptor belt, there is a magnetic brush roller 13 rotatable around a fixed magnet roller, a full-surface exposure lamp 14, a charging device 15, and an AC discharge device 16. is installed.

The magnetic brush roller 13 is driven in the aforementioned forward direction (direction of arrow c), and when the photoreceptor belt 5 rotates forward, it attracts toner to the electrostatic latent image on the photoreceptor belt 5 to perform development. On the other hand, the photoreceptor belt 5
When the photoreceptor belt is reversed, it performs a cleaning action by collecting toner adhering to the photoreceptor belt. The direction of rotation of the magnetic brush roller 13 remains in the c direction without changing even when the photoreceptor belt 5 is reversed.
When the photoreceptor belt 5 is reversed, the magnetic brush roller 1
3 and the photoreceptor belt 5 rub against each other in a counter manner. Therefore, the cleaning effect is extremely good.

The full-surface exposure lamp 14 functions to expose the surface of the photoreceptor belt having a visible image during the developing process during normal rotation of the photoreceptor belt, thereby improving transfer efficiency and separation performance. On the other hand, when the photoreceptor belt is reversed, it cooperates with an AC discharge device 16, which will be described later, to perform a so-called charge-eliminating action that erases the residual charge on the surface of the photoreceptor belt after the transfer is completed. This full-surface exposure lamp 14 can be provided between the optical system 12 and the magnetic brush roller 13 in addition to the position shown in the figure. In that case, the effect of this lamp 14 is the same. However, since only an electrostatic latent image is formed on the photoreceptor belt during forward rotation of the photoreceptor belt, the direct effect is to improve the contrast of the electrostatic latent image.

The charging device 15 performs a corona discharge on the surface of the photoreceptor belt to uniformly charge the photoreceptor belt surface during about one rotation after the photoreceptor belt 5 starts normal rotation (charging process).
On the other hand, when the photoreceptor belt 5 rotates one or more revolutions and the leading edge of the image on the photoreceptor belt that has been charged, exposed, and developed reaches the charging device 15,
Next, a transfer process is performed in which corona discharge is performed from the back side of the copy paper to transfer the toner image on the photoreceptor belt onto the copy paper. Note that the charging device 15 is not operated when the photoreceptor belt is reversed.

The AC discharge device 16 acts to separate the transferred copy paper from the surface of the photoreceptor belt when the photoreceptor belt rotates in the normal direction, and on the other hand, when the photoreceptor belt rotates in the normal direction, it works together with the full-surface exposure lamp 15 to remove static electricity. Let's do it.

In the figure, 17 is a cassette containing copy paper, 18
19 is a paper feed roller; 19 is a register roller; 20 is a copier detector that detects whether copy paper is present at the position of the registration roller 19; 21 is a conveyor belt that transports the copy paper separated from the surface of the photoreceptor belt; 22 is a fixing roller, and 23 is a copy paper receiver.

In this configuration, when the operator turns on the power switch, first the photoreceptor belt 5 is reversed to perform the static elimination and cleaning process. After the copying machine is ready for printing, when the operator presses the print button, the photoreceptor belt 5 rotates approximately one rotation in the normal direction, during which time it is charged, and then rotates in the normal direction for exposure, development, full-surface exposure, and so on. Printing is done by performing the steps of transfer and separation. When printing is completed, the photoreceptor belt 5 is reversely rotated to perform a static elimination and cleaning process in preparation for the next printing. The above operation will be further explained in detail based on the time chart shown in FIG. First, when the power switch is turned on at time _T1 , the photoreceptor belt 5 rotates approximately one rotation in the opposite direction. In order to reverse the photoreceptor belt 5 by a predetermined amount, the pulses P generated by the detection element 11 are counted by a counter (not shown) built into the machine.
The configuration is such that the motor 8 is controlled depending on the count contents. Simultaneously with the reverse rotation of the photoreceptor belt 5, the magnetic brush roller 13 rotates in the forward direction, the entire surface exposure lamp 14 is turned on, and the AC discharge device 16 is energized, so that the photoreceptor belt 5
is neutralized and cleaned.

When the static elimination and cleaning are completed, the printer becomes ready for printing, and when the print button is pressed at subsequent time T ₂ , the photoreceptor belt 5 starts normal rotation and the charging device 15 is energized with power. Charging is performed by the charging device 15 while the photoreceptor belt 5 rotates normally (approximately one rotation) from the charging device 15 to the exposure position A. This charging is approximately equal to the distance over which the original is scanned for exposure. Further, at the same time as the photoreceptor belt 5 starts to rotate normally, the conveyor belt 21 and the fixing roller 22 are driven, and the magnetic brush roller 13 and the entire surface exposure lamp 14 are activated and lit. However, at this time the AC discharge device 16 is not energized. This is to prevent the uniform charging performed by the charging device 15 from being disturbed. During the charging process by the charging device 15, the paper feed roller 18
is driven, and when the charging process is completed, the document mounting table 4
It performs a predetermined operation in which it reverses, then rotates forward, and then reverses again to return to its home position. The timing of operation of the paper feed roller 18 and the document table 4 is controlled by counting pulses P generated by the detection element 11 using a counter, and based on the contents of the count. Incidentally, an up-down counter is used as the counter, and a distinction is made between the forward and reverse times so that when the photoreceptor belt rotates in reverse, it counts down and when it rotates in the normal direction, it counts up.

Next, when the document table 4 changes from reverse rotation to normal rotation, the main exposure lamp 12a in the optical system 12,
The AC discharge device 16 is turned on and energized, and together with the already operating magnetic brush roller 13, full surface exposure lamp 14, and charging device 15, exposure, development, and full surface exposure are performed as the photoreceptor belt 5 rotates forward. , performs transfer and separation processes, and prints. In this case, registration rollers 19 are driven before AC discharge device 15 is energized. This is because if the registration roller 19 and the AC discharge device 15 are operated at the same time, the portion of the photoreceptor belt exposed by the optical system 12 will be neutralized.
This is because it is inconvenient. Therefore, registration roller 1
9 is activated before the AC discharge device 15, and the AC discharge device 15 is energized after the leading edge of the copy paper reaches the AC discharge device 15. The operation timing of this registration roller 19 and AC discharge device 15 is also controlled by a counter.

When printing is completed as described above, the photoreceptor belt 5 is reversed, and static electricity is removed and cleaned by the magnetic brush roller 13, full-surface exposure lamp 14, and AC discharge device 16, in preparation for the next printing. On the other hand, the copy paper that has been transferred up to this point and separated by the AC discharge device is discharged through the conveyance belt 21 and the fixing roller 22.

In this embodiment, a full surface exposure lamp is used for the full surface exposure and static elimination functions, but the main exposure lamp 12a of the optical system may be used instead of the full surface exposure lamp. In that case, the main exposure lamp 12a is installed at the position shown in FIG. 4, and a slit S is provided at the bottom of the reflection plate 12b, so that a part of the light from the main exposure lamp 12a passes through the slit S and irradiates the photosensitive member. Just do it. The operating timing of the main exposure lamp 12a at this time may be as shown by the two-dot chain line in FIG.

Furthermore, although a photosensitive belt is used as the photosensitive member in the above embodiment, a photosensitive drum may also be used. Even when a photoreceptor belt is used, two or more driven rollers may be provided and the photoreceptor belt may be wound between the drive roller and the two or more driven rollers. Further, in the embodiment, the original table is moved during printing, but the optical system may be moved.

As explained above, the present invention is a copying machine that performs charging, exposure, development, full-surface exposure, transfer, and separation processes when the photosensitive member rotates forward, and performs static elimination and cleaning processes when the photosensitive member rotates in the reverse direction. A charging device is used for the transfer process, a magnetic brush is used for the development and cleaning process, and an exposure lamp is used for the entire surface exposure and static elimination process.
Since the separation and static elimination steps are performed by an AC discharge device, the following effects are achieved.

Magnetic brushes are installed around the photosensitive member in the development process and cleaning process, exposure lamps are used in the entire surface exposure and static elimination process, charging devices are used in the charging process and transfer process, and AC discharge devices are installed in the separation process and static elimination process. Since all of the equipment used is used in both processes, the number of equipment can be reduced to the maximum, making it possible to make the machine more compact and to significantly reduce costs. In particular, if a photoreceptor belt is used, the size can be significantly reduced.

In the developing step, the direction of rotation of the photosensitive member and the direction of rubbing with the magnetic brush are in the forward direction (direction c), and in the cleaning step, the direction of rotation of the photosensitive member and the direction of rubbing with the magnetic brush are in opposite directions at the contact portion. It not only provides high image quality but also exhibits good cleaning performance.

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram of a copying machine showing an embodiment of the present invention, Fig. 2 is a perspective view showing an example of a photosensitive member, and Fig. 3 is a time chart for explaining the operation of the copying machine shown in Fig. 1. , FIG. 4 is an overall configuration diagram of a copying machine showing another embodiment of the present invention. 5...Photosensitive member, 12a...Main exposure lamp, 1
3...Magnetic brush roller, 14...Full surface exposure lamp, 15...Charging device, 16...AC discharge device,
a...Forward direction, b...Reverse direction.

Claims (1)

[Scope of Claims] 1. A copying machine that performs charging, exposure, development, full-surface exposure, transfer, and separation processes when the photosensitive member rotates in the normal direction, and performs a static elimination and cleaning process when the photosensitive member rotates in the reverse direction, the copying machine including the charging and transfer process. A copying machine characterized in that a charging device performs the development and cleaning steps, a magnetic brush performs the development and cleaning steps, an exposure lamp performs the entire surface exposure and static elimination steps, and an AC discharge device performs the separation and static elimination steps. 2. The copying machine according to claim 1, wherein the exposure lamp is a full-surface exposure lamp. 3. The copying machine according to claim 1, wherein the exposure lamp is a main exposure lamp. 4. Claims 1 to 3, characterized in that the photosensitive member is an endless photosensitive belt.
Copying machine described in any of the above. 5. The copying machine according to any one of claims 1 to 3, wherein the photosensitive member is a photosensitive drum.