JPH0383084A - Controller for separating pawl - Google Patents

Abstract

PURPOSE:To shorten the contact time of a separating pawl with an image carrying member to the min. required time by switching the separating pawl to an operating state or releasing state in accordance with the output of a density detecting means which makes the detection associated to the density of the image carried by the image carrying member. CONSTITUTION:The case in which the transfer material in tight contact with the image carrying member 1 is hardly separable from the image carrying member 1 is the case in which the transfer material and the image carrying member 1 are electrostatically strongly bonded to each other. The intensity of the electrostatic bond has a specified relation with the density of the image carried by the image carrying member 1. The value associated to the density of the image carried by the image carrying member 1 is, thereupon, detected by the density detecting means 4. The separating pawl 8 is pressed to the image carrying member 1 or released therefrom in accordance with the detected value. The time to press the separating pawl 8 to the image carrying member 1 is shortened to the min. required time in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a control device for a separating claw for separating a transfer material from an image carrier.

<Prior Art> Image forming apparatuses such as copying machines, facsimile machines, and laser printers are equipped with, for example, a photosensitive drum as an image carrier. A latent image is formed on the photoreceptor drum by electrostatic photography, and the formed latent image is developed with toner and then transferred to a transfer material such as transfer paper. When transferring a toner image to a transfer paper, the transfer paper is brought into close contact with the surface of the photoreceptor drum.

Transfer paper that is in close contact with the photoreceptor drum is difficult to separate from the photoreceptor drum even after the toner image has been transferred, so some types of transfer paper are provided with a separation discharger or a separation claw.

Among these, the separation claw is mainly used to prevent the transfer paper that is not separated by the separation discharger from wrapping around the photoreceptor drum, but the separation claw is always in contact with the surface of the photoreceptor drum. This may wear out the drum surface,
The degree of injury will increase.

Therefore, some conventional devices are configured so that the separation claws can be switched between contacting and not contacting the surface of the photoreceptor drum. It is known that the separating claw is brought into contact with the photosensitive drum only when it is applied to the photosensitive drum.

<Problems to be Solved by the Invention> By the way, as mentioned above, the separation claw is a member that may wear or damage the surface of the photoreceptor drum, etc.
It is better to keep the time in contact with the surface of the photoreceptor drum as short as possible, and it is preferable to keep the contact time in contact with the surface of the photoreceptor drum only for the minimum amount of time necessary.

In the conventional operation control of the separation claw, the separation claw always comes into contact with the photoreceptor drum when the transfer paper is applied to the photoreceptor drum, which has the disadvantage that the contact time is long.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide a separating claw control device that brings the separating claw into contact with the surface of an image carrier only when necessary.

Means for Solving the Problems> The present invention is capable of freely switching between an operating state in which the image carrier is in contact with the surface of the image carrier and a released state in which it is not in contact with the surface of the image carrier. A control device for a separation claw, the device including a density detection means for detecting a value related to the density of an image carried by an image carrier, and a control device for controlling the separation claw into an operating state or a released state based on an output of the density detection means. This is a separation claw control device characterized in that it includes a switching control means for switching to a separation claw.

Further, in the separating claw control device, the switching control means is configured to control whether the density of the image transferred to the transfer material is higher than or equal to a predetermined value within a predetermined length range from the leading edge of the transfer material. , the separating claw is switched to a released state or an activated state depending on whether the concentration is low or less than a predetermined value.

Effects> The case where the transfer material in close contact with the image carrier is difficult to separate from the image carrier is the case where the transfer material and the image carrier are strongly bonded electrostatically. The strength of this electrostatic bond has a certain relationship with the density of the image carried by the image carrier.

Therefore, in the present invention, a value related to the density of the image carried by the image carrier is detected, and the separating claw is brought into contact with or released from the image carrier based on the detected value.

Thereby, the time during which the separating claw is brought into contact with the image carrier can be kept to the minimum necessary.

<Embodiment> Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing the configuration of an image forming mechanism of a copying machine equipped with an embodiment of the present invention.

Referring to FIG. 1, the image forming mechanism includes a photosensitive drum 1 as an image carrier. During image formation, the photosensitive drum 1 is rotated at a constant speed in the direction of arrow A1.

Around the photosensitive drum 1, there are a pre-charging lamp 2, a main charger 3, a potential sensor 4, a developing sleeve 5, a pre-transfer lamp 6, a transfer 7 separation charger 7, a separation claw 8, a fur brush 9, and a cleaning blade 10. They are arranged along the rotational direction of the photosensitive drum 1.

The pre-charging lamp 2 is used to completely remove unnecessary charges remaining on the surface of the photosensitive drum 1. The surface of the photosensitive drum 1 from which unnecessary charges have been removed by the pre-charging lamp 2 is charged to a constant potential, for example 750V, by the main charger 3. After being charged, the surface of the drum is exposed to image-forming light such as light reflected from the original, and an image of the original is formed as an electrostatic latent image.

A potential sensor 4 is connected to a photosensitive drum 1 on which an electrostatic latent image is formed.
The detection output is amplified by an amplifier 11 and given to an arithmetic control circuit 12, where it is used for on/off control of a solenoid 13 for driving the separation claw 8. One of the features of this embodiment is that the driving of the separating claw 8 is controlled based on the surface potential of the photosensitive drum 1 on which the electrostatic latent image is formed.

The electrostatic latent image formed on the photosensitive drum 1 is developed into a toner image by the developing sleeve 4, and the potential bond between the drum surface and the toner image is weakened by the pre-transfer lamp 6.
It is sent to the transfer 1 separation charger 7.

In connection with the rotation of the photoreceptor drum 1 described above, the transfer paper as a transfer material is transferred to the photoreceptor drum 1 by the registration roller 14.
supplied to The supplied transfer paper is brought into close contact with the surface of the photoreceptor drum 1, the toner image is transferred by the action of corona discharge from the transfer 1 separation charger 7, and after the toner image is transferred, it is separated from the surface of the photoreceptor drum 1 and transported. belt 1
Sent to 5.

In this way, the transfer paper on which the toner image has been transferred is usually separated from the surface of the photoreceptor drum 1 by the separation charger 7, but some transfer papers remain wrapped around the photoreceptor drum 1.

The separation claw 8 is used to mechanically separate the transfer paper from the photoreceptor drum 1 when the transfer paper is wrapped around the photoreceptor drum 1 in this manner. This separating claw 8 is not always in contact with the surface of the photoreceptor drum 1, but depending on the on/off of the solenoid 13, the separation claw 8 can be in an operating state in which it is in contact with the surface of the photoreceptor drum 1 or in an operating state in which it is in contact with the surface of the photoreceptor drum 1, or in an operating state in which it is separated from the surface of the photoreceptor drum 1. It is possible to switch between the release state and the release state. The switching control of the operating state/release state of the separation claw 8 will be described later.

The fur brush 9 and cleaning blade 10 are for cleaning residual toner on the surface of the photosensitive drum 1.

FIG. 2 is a flowchart showing the image density detection control content executed by the arithmetic control circuit 12 of FIG.

Next, the process will be explained in accordance with the flow shown in FIG. 2 and with reference to FIG. In the image density detection control, the arithmetic control circuit 12 samples the detected value of the potential sensor 4 at a predetermined timing and stores it in the register A of the arithmetic control circuit 12 that is set to H (step 5.1). The predetermined timing is, for example, when the image forming operation is started and the exposure start position on the photosensitive drum 1 reaches a position facing the potential sensor 4.

The surface potential of the exposed photoreceptor drum 1 becomes low when the exposure amount is large because more charges are removed, and it becomes high when the exposure amount is small because many charges remain unremoved. Since the amount of toner adhesion is determined by the level of this potential, the potential detected by the potential sensor 4 has a value proportional to the image density.

After sampling the detected value of the potential sensor 4 in step S1, wait for a certain period of time to elapse using, for example, a timer provided on the program or a timer formed in a circuit (step S2). 4 detection value is sampled and e4 calculation sub-control path 12
(step S3).

Then, the value stored in register A and register B
Compare the level with the potential stored in step S.
4) Store the higher potential in register A (step S5).

Then, steps 82 to S5 are repeated until sampling is completed a predetermined number of times, for example, six times (step S6).

When the predetermined number of samplings are completed, the highest potential among the sampling potentials stored in register A is compared with a predetermined reference potential, for example 150 V, and if the highest sampling potential of register A is less than 150 V, a white "
If it is 150V or more, it is determined as “black” (step S
7). If the potential is "white", the white flag is set (step S8), and if not, the own flag is reset (step S9).

By the above-mentioned six samplings, a certain length, for example, 5rr+rr+
It is possible to detect the potential of six consecutive regions at the t1 position,
The highest potential of the six areas is stored in register A. Then, density control can be performed based on this. In other words, it can be determined whether or not the image at the leading edge of the paper 30 mm (5 mm x 6) includes a black image.

Instead of this method, store all six detected sampling potentials and calculate the average potential.
The potential may be compared with a reference potential 150■ to determine whether it is the own level or the black level.

Furthermore, to make it simpler, the potential may be detected only once at a predetermined timing, and the detected potential may be compared with a reference potential of 150V to determine whether it is a white level or a black level.

FIG. 3 is a flowchart showing the details of the control of the separating claw 8 executed by the arithmetic control circuit 12.

Next, the operation of the separating claw 8 will be explained in accordance with the flow shown in FIG. 3 and with reference to FIG. 1.

Based on the fact that the secondary sheet feeding is started by the No. 1 nozzle roller 14 (step 511), the arithmetic control circuit 12 determines whether its own flag is set or not (step 51).
2). That is, it is determined whether the image density at the leading edge of the paper is at a white level or a black level.

Then, the image density at the leading edge of the paper is at the white level, that is,
If the white flag is set, a timer measures a predetermined time (step 513). This predetermined period of time is after the secondary feeding of the transfer paper is started by the registration roller 14, and when the leading edge of the transfer paper reaches the separation claw 8.
This is the time required to reach a predetermined position on the near side.

When a predetermined time has elapsed, the arithmetic and control circuit 12 turns on the solenoid 3 to bring the separating claw 8 into contact with the photosensitive drum 1 (step 514). After the separation claw 8 comes into contact with the photoreceptor drum, the separation claw 8 waits for a certain period of time necessary for the separation claw 8 to separate the transfer paper (step 515), and then turns off the solenoid 13 and turns off the separation claw 8. is separated from the surface of the photoreceptor drum 1.

Since the separating claw 8 is controlled in this manner, the separating claw 8 is brought into contact with the photosensitive drum 1 for a certain period of time only when the image density transferred to the leading edge of the transfer paper is close to white.

That is, when the transfer paper does not separate from the photoreceptor drum 1 and tends to wrap around the photoreceptor drum 1, the image density transferred to the leading edge of the transfer paper is often close to white. Therefore,
In this embodiment, the separating claw 8 is brought into contact with the surface of the photosensitive drum 1 only in such a case.

As a result of this f15, the separating claw 8 is brought into contact with the photosensitive drum 1.
.

In the above-described embodiment, the potential sensor 4 is disposed downstream of the exposure position and upstream of the developing sleeve 5 along the rotational direction of the photoconductor drum 1, and the potential sensor 4 measures the photoconductor drum 1 after exposure. Although the surface potential is detected and the image density is thereby detected, the following configuration is also possible.

That is, along the rotational direction of the photosensitive drum 1, a density sensor 20 such as a rectangular-shaped charge conversion element is disposed downstream of the developing sleeve 5 and upstream of the transfer position, and the density sensor 20 The density of the toner attached to the surface of the photosensitive drum 1 may be detected, and the density of the c1 image may be directly detected.

In addition, in image forming apparatuses that read original images using a CCD (for example, digital copying machines), laser printers, etc., the detection signal or laser drive signal read by the CCD and the amount of light during exposure are used. Since there is a correspondence relationship, the image density may be determined based on the signal.

<Effects of the Invention> Since the present invention is configured as described above, the time during which the separation claw contacts the image carrier can be reduced to the minimum necessary, and the image carrier is not worn out by the separation claw. This can reduce the frequency of being injured or injured. As a result, both the life of the image carrier and the life of the separating claw can be extended.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an image forming mechanism of a copying machine equipped with an embodiment of the present invention. FIG. 2 is a flowchart showing image l seismic intensity detection control executed by the arithmetic control circuit. FIG. 3 is a flowchart showing separation claw control carried out by the arithmetic control circuit. In the figure, 1... a photosensitive drum as an image carrier;
8. Separation claw, 4. Potential sensor, 12. Arithmetic control circuit, ] 3. Solenoid.

Claims (1)

[Claims] 1. An operating state in which the image carrier is in contact with the surface; It can be switched freely between the released state and the non-contact state. Separates the transfer material from the image carrier during operation A control device for the separation pawl that serves to And, It is related to the density of the image carried by the image carrier. concentration detection means for detecting the value of the Separation based on the output of the concentration detection means Switch the claw to the activated or released state switching control means; A separation claw control device comprising: Place. 2. Separation claw control device according to claim 1 In, The switching control means is transferred to the transfer material. The image density is predetermined from the tip of the transfer material. Darker than the specified value within the length range. depending on whether the concentration is low or low concentration below a predetermined value. Switch the separation claw to the released state or activated state It is characterized by the ability to grow.