JPH07319296A - Transfer belt device - Google Patents

Abstract

PURPOSE:To surely perform the attaching and detaching operation of a transfer belt with respect to a photoreceptor drum with high reliability at a low cost by a simple constitution. CONSTITUTION:The transfer belt device provided with the transfer belt 2 held in contact with the image carrier 1, the bias impressing means 3, a power source 7a of the bias impressing means 3, a contact electrode 6 on the transfer belt 2, and the belt attaching and detaching means 9, is provided with a whole current detecting means 7b for detecting the whole current outputted from the power source 7a, a feedback current detecting means 7c for detecting the feedback current made to flow in the contact electrode 6, a differential current detecting means 7d for detecting the difference current between the whole current detecting means 7b and the feedback current detecting means 7c, and the attaching and detaching detecting control mean 17 for controlling the driving of the belt attaching and detaching means 9 basing on the detecting result of the differential current detecting means 7d.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in a copying machine or the like, and a contacting / separating means for contacting / separating a transfer belt for transferring a toner image on an image carrier onto a transfer paper. The present invention relates to a transfer belt device equipped with.

[0002]

2. Description of the Related Art Conventionally, in order to transfer a toner image on a photoconductor drum, which is an image carrier, onto a transfer paper, a transfer belt device of the type in which the transfer paper is pressed against the photoconductor drum by a transfer belt has been used. There is. Since this transfer belt device forms a nip portion (contact portion) between the transfer belt and the photoconductor drum to perform transfer, when the P sensor pattern is formed on the photoconductor drum, the transfer belt is exposed to light. It is necessary to pull it away from the body drum. For this reason, most transfer belt devices
A contact / separation mechanism for contacting / separating the transfer belt with respect to the photosensitive drum is provided.

[0003]

However, in the above-mentioned conventional transfer belt device, a sensor is often used to detect the contact / separation state of the transfer belt with respect to the photosensitive drum. In this case, the sensor or the sensor is used. Turn on
It is necessary to provide a detection mechanism such as a filler that turns off. Therefore, there are problems that the mechanism becomes complicated and the cost becomes high. Also, in the case of adopting the method of performing the above-mentioned contact / separation operation by a solenoid or the like without using this sensor,
Since it is difficult to detect an incomplete contact / separation state caused by insufficient operation of the solenoid, there is a problem of low reliability. Therefore, the present invention solves the above-mentioned conventional problems, and has a low cost and simple configuration,
An object of the present invention is to provide a transfer belt device that can reliably and reliably perform a contact / separation operation of a transfer belt with respect to a photosensitive drum.

[0004]

According to a first aspect of the present invention, there is provided a transfer belt which is stretched by a driving roller and a driven roller and is in contact with an image carrier, and is arranged in contact with the transfer belt. Bias applying means for applying a bias voltage to the belt, a power source for the bias applying means, a contact electrode arranged in contact with the transfer belt for grounding charges on the belt, and an image carrier for the transfer belt. In a transfer belt device including a belt contacting / separating unit that performs a contacting / separating operation with respect to, a total current detecting unit that detects a total current output from the power source, and a feedback current detecting unit that detects a feedback current flowing into the contact electrode. From the respective detection results of the total current detection means and the feedback current detection means,
A difference current detection unit that detects these difference currents and a contact / separation state of the transfer belt with respect to the image carrier are determined from the detection result of the difference current detection unit, and the belt contact / separation unit is driven based on the determination result. A bias voltage applied by the bias applying unit when detecting the contact / separation state is set to a constant voltage, and an upper limit is set for the contact voltage. According to the present invention, the bias voltage is applied by the bias applying means and the contact / separation detecting means is in contact / separation state before the transfer belt is contacted / separated. Is detected, and the contact / separation operation is performed only when the desired contact / separation state is not reached. In this case, the series of operations are repeated until the desired contact / separation state is detected,
If the number of repetitions exceeds at least two times, the abnormality display means displays an abnormality to the user.

[0005]

Therefore, according to the first aspect, when the contact state of the transfer belt with respect to the image carrier is detected, the total current output from the power source by the total current detecting means also flows into the contact electrode by the feedback current detecting means. The feedback currents are respectively detected, and the difference current detection means detects the difference current from these detection results. The contact / separation detection control unit determines the contact / separation state from the detection result of the difference current detection unit, and the belt drive unit is drive-controlled based on the determination result. Thus, the contact / separation state of the transfer belt is detected only by detecting the current.

In the second and third aspects, when the contact / separation state is detected, the bias voltage applied by the bias applying means is set to a constant voltage, and an upper limit is set to this, so that leakage or the like occurs when the bias voltage is applied. Try not to occur. In claim 4, before performing the contacting / separating operation of the transfer belt,
A bias voltage is applied by the bias applying means,
The contact / separation detection unit performs the process of detecting the contact / separation state, and the contact / separation operation is performed only when the contact / separation state is not the desired contact / separation state. .

According to a fifth aspect of the present invention, first, in response to the contact / separation detection of the transfer belt by the contact / separation detection means, a series of operations for performing the contact / separation operation by the belt contact / separation means is performed once, and then the operation is performed again. Only when the contact / separation state is not detected and the desired contact / separation state is not detected, the series of operations is repeated until the desired contact / separation state is detected. As a result, even if a failure of the contacting / separating operation or the like occurs, the desired contacting / separating state is finally surely achieved. In the sixth aspect, as in the fifth aspect, when repeating a series of operations for performing the contact / separation detection and the contact / separation operation, if the number of repetitions exceeds at least two times, an abnormality is displayed to the user by the abnormality display means. By displaying, the failure of the machine is accurately indicated.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, a transfer belt 2 is arranged in contact with a photosensitive drum 1, and the transfer belt 2 is stretched by a driving roller 3 and a driven roller 4, and is made of a rubber material or the like having a medium electric resistance. Made of Then, at the position on the inner peripheral surface of the transfer belt 2 which is separated from the nip portion 13 between the photosensitive drum 1 and the transfer belt 2 toward the drive roller 3 by a predetermined distance, a bias as a bias applying means for applying a bias voltage. The roller 5 is disposed in contact with the roller 5, and the ground member 6 is disposed in contact with the inner peripheral surface of the transfer belt 2 between the bias roller 5 and the driving roller 3. The bias roller 5 is a metal roller and is rotated by the rotation of the transfer belt 2. The ground member 6 is a metal plate, and both of them are connected to a power pack 7, which is a power source.

The power pack 7 includes a bias roller 5
There are connected, the total current detection circuit 7b for detecting the total current I output from the power source 7a, A - scan member 6 is connected, a feedback current for detecting a current (feedback current) I ₂ flowing into the grounding member 6 The detection circuit 7c and the total current detection circuit 7
b and the feedback current detection circuit 7c, a differential current detection circuit 7d for detecting a differential current I ₁ between the total current I and the feedback current I _2.
It has internal organs. A transfer belt contacting / separating mechanism 9, which is a belt contacting / separating means, is provided in contact with the transfer belt 2.
As shown in FIG. 2, the transfer belt contact / separation mechanism 9 includes an arm member 11 elastically biased in the direction of arrow A, which is the transfer belt 2 direction, by a spring 10 having one end fixed to the apparatus body side. A shaft 12 that rotatably supports the arm member 11, a cam 14 that abuts a cam receiving plate 13 fixed to one end of the shaft 12, and a transmission of a driving force of a drive motor 16 to the cam 14 are turned on.・ Half rotation clutch 1 to turn off
It is composed of 5 and.

Further, the differential current detection circuit 7d and the drive motor 16 are connected to a contact / separation detection control circuit 17 which is contact / separation detection control means. In the above configuration,
Before performing the contact / separation operation of the transfer belt 2 with respect to the photosensitive drum 1, the power source 7 is used to detect the contact / separation state of the transfer belt 2.
A bias voltage is applied to the transfer belt 2 from a through the bias roller 5. When the contact / separation detection control circuit 17 determines that the transfer belt 2 is separated from the photosensitive drum 1 from the detection result of the contact / separation detection, the control circuit 17 drives the transfer belt contact / separation mechanism 9. The contact / separation operation is performed so that the transfer belt 2 comes into contact with the photosensitive drum 1. In this state, after the toner image on the photosensitive drum 1 is transferred to the transfer paper placed on the transfer belt 2, the transfer paper is conveyed on the transfer belt 2 and the toner image is fixed by a fixing device (not shown). It

Next, the contact / separation detection operation and the contact / separation operation of the transfer belt 2 with respect to the photosensitive drum 1 will be described in detail. When a bias voltage is applied, as shown in FIG.
The total current I output from the power supply 7a is the total current detection circuit 7b.
Thus, the feedback current I ₂ flowing into the earth member 6 is detected by the feedback current detection circuit 7c, and the difference current I ₁ between the total current I and the feedback current I ₂ is detected by the difference current detection circuit 7d. That is, I = I ₁ + I ₂ .

Then, as shown in the flow chart of FIG. 3, when the difference current value of the detection result by each of the detection circuits 7b and 7c is substantially 0, part of the total current I does not flow to the photosensitive drum 1 side. Since the feedback current I ₂ remains unchanged, the contact / separation detection control circuit 17 determines that the transfer belt 2 and the photosensitive drum 1 are separated. On the other hand, when the difference current value is not 0, a part of the total current I flows to the side of the photoconductor drum 1 and the feedback current I ₂ is small, so that there is a difference between the total current I and the feedback current I _2. Therefore, the contact / separation detection control circuit 17 determines that the transfer belt 2 and the photosensitive drum 1 are in contact with each other. However, since the difference current value serving as a reference for determination has a detection error of each of the detection circuits 7b and 7c, the determination of 0 is the minimum value that does not include the error.

Therefore, as shown in FIG. 4, when it is determined that the transfer belt 2 and the photosensitive drum 1 are in contact with each other, the contacting / separating operation is not performed, and the current is applied to the photosensitive drum 1 and the ground member 6 side. Flowing. On the other hand, when it is determined that the transfer belt 2 and the photosensitive drum 1 are separated from each other, the transfer belt 2 is brought into contact with or separated from the photosensitive drum 1. That is, as shown in FIG. 2, the half-rotation clutch 15 of the transfer belt contact / separation mechanism 9 is turned on to transmit the power of the drive motor 16 to the cam 14 to rotate the cam 14, thereby rotating the arm 11 in the direction of arrow B. By moving the transfer belt 2, the transfer belt 2 is pressed and brought into contact with the photosensitive drum 1.

The voltage output from the power supply 7a is a constant voltage when a bias voltage is applied when the contact state of the transfer belt 2 is detected. The value of this voltage is set freely within the range where there is no danger of leakage. Also, the power supply 7a is
Limit the output so that there is no risk of leakage. By the way, in the contact / separation operation, the case where the transfer belt 2 is brought into contact with the photosensitive drum 1 at the start of use of the transfer belt device or the like has been described. On the contrary, when the transfer belt 2 is to be separated from the image carrier 1, as shown in FIG. 5, the contact / separation detection control circuit 17 causes the transfer belt 2 and the photosensitive belt 1 When it is determined that the body drum 1 is in contact, a contact / separation operation is performed,
On the other hand, when the contact / separation detection control circuit 17 determines that the transfer belt 2 and the photosensitive drum 1 are separated, the contact / separation operation is not performed.

Further, as shown in FIG. 6, after the contact / separation operation is performed once (step 1) as described above, the bias voltage is applied again (step 2), and the similar contact / separation detection is performed (step 2). If the desired contact / separation state is reached, the process proceeds to the next processing (step 4). If the desired contact / separation state is not reached, the contact / separation operation and contact / separation detection are performed again (step 1,
It is also possible to carry out steps 2 and 3) and repeat this until a desired contact / separation state is reached, so that a more reliable contact / separation operation is performed.

Further, as shown in FIG. 7, once the contact / separation operation is performed (step 1), the bias voltage is applied again (step 2), and the similar contact / separation detection is performed (step 3). If it is in the desired contact / separation state, the process proceeds to the next processing (step 4), and if it is not in the desired contact / separation state,
The contact / separation operation and the contact / separation detection are performed again, and this is repeated until the desired contact / separation state is achieved. At that time, the number of repetitions is counted (step 5), and if it is within 2 times, the contacting / separating operation is repeated (steps 1, 2, 3), and if it exceeds 2 times, it is judged as abnormal operation, For example, such a configuration may be adopted in which the control is stopped by performing processing such as operation stop and abnormal display (step 6). In this case, the number of times of determination as an abnormal operation is not limited to 3 times, but can be freely selected within a range of n times (n> 2), that is, 3 times or more.

[0017]

As described above, according to the invention described in claim 1, the total current detecting means for detecting the total current output from the power source and the feedback current detection for detecting the feedback current flowing into the contact electrode. Means, a differential current detecting means for detecting a difference current from the detection results of the total current detecting means and the feedback current detecting means, and a detection result of the differential current detecting means, and the image carrier of the transfer belt. Since the contact / separation detection control means for determining the contact / separation state with respect to the body and controlling the drive of the belt contact / separation means from the determination result is provided, the contact / separation state of the transfer belt can be detected only by detecting the current. In addition, a reliable and accurate contact / separation operation can be performed with a low cost and a simple configuration without providing a complicated mechanism for detecting the contact / separation state. Further, it is possible to perform highly reliable contact / separation detection with a simple structure as compared with a transfer belt having a mechanism of contacting / separating with a solenoid.

According to the second aspect of the present invention, when the contact / separation state is detected, the bias voltage applied by the bias applying means is set to a constant voltage. Therefore, when the bias voltage is applied, leakage (electric leakage) or the like occurs. It is safe and can operate safely. According to the invention as set forth in claim 3, since the upper limit is set for the bias voltage applied by the bias applying means when the contact / separation state is detected, even if the differential current by the differential current detecting means is constant, When the transfer belt and the image carrier are separated from each other, the differential current becomes 0, and it is possible to prevent the voltage from reaching the output upper limit and causing a problem such as leakage.

According to the fourth aspect of the present invention, before the contact / separation operation of the transfer belt is performed, a bias voltage is applied by the bias applying means and the contact / separation state is detected by the contact / separation detecting means. Since the contacting / separating operation is performed only when the desired contacting / separating operation is not performed, the contacting / separating operation can be performed in the desired contacting / separating state with the minimum necessary contacting / separating operation. Can be contributed to. Claim 5
According to the described invention, in response to the contact / separation detection of the transfer belt by the contact / separation detection unit, a series of operations for performing the contact / separation operation by the belt contact / separation unit is performed once, and the contact / separation detection is performed again. If the contact / separation state is not detected as desired, the series of operations described above is repeated until the desired contact / separation state is detected. Can be brought into contact with or separated from each other, which can prevent a transfer failure or the like from occurring.

According to the sixth aspect of the invention, a series of operations for performing the contacting / separating operation by the belt contacting / separating means is performed once in response to the contact / separation detection of the transfer belt by the contact / separation detecting means. When it is not detected that the desired contact / separation state is reached, when the series of operations is repeated until the desired contact / separation state is detected, if the number of repetitions exceeds at least 2, an error is displayed to the user. Since the abnormality display means is provided, it is possible to avoid a runaway of repeated contact / separation detection operations, and prevent the machine from continuing to operate with a failure.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a transfer belt device showing an embodiment of the present invention.

FIG. 2 is a perspective view showing a transfer belt contact / separation mechanism.

FIG. 3 is a flowchart showing a contact / separation detection process of a transfer belt.

FIG. 4 is a flowchart showing a contact / separation detection process when the transfer belt is to be brought into contact with an image carrier.

FIG. 5 is a flowchart showing a contact / separation detection process when the transfer belt is being separated from the image carrier.

FIG. 6 is a flowchart showing a process of repeating contact / separation detection and contact / separation operation of the transfer belt.

FIG. 7 is a flowchart showing a process of displaying an abnormality according to the number of times contact / separation detection is repeated.

[Explanation of symbols]

 1 image carrier 2 transfer belt 3 bias applying means 6 earthing member 7a power supply 7b total current detecting means 7c feedback current detecting means 7d differential current detecting means 17 contact / separation detecting control means

Claims (6)

[Claims] 1. A drive roller and a driven roller are stretched between the rollers.
A transfer belt that is in contact with the image carrier, a bias applying unit that is arranged in contact with the transfer belt and applies a bias voltage to the belt, and a power supply for the bias applying unit.
A transfer belt device comprising a contact electrode arranged in contact with the transfer belt for grounding an electric charge on the transfer belt, and a belt contacting / separating means for contacting / separating the transfer belt with respect to an image carrier. From the total current detection means for detecting the total current output from the total current output means, the feedback current detection means for detecting the feedback current flowing into the contact electrode, and the total current detection means and the feedback current detection means. Differential current detecting means for detecting the differential current of the transfer belt, and the contact / separation state of the transfer belt with respect to the image carrier from the detection result of the differential current detecting means, and the drive of the belt contact / separation means is controlled based on the determination result. A transfer belt device, comprising: a contact / separation detection control unit that operates. 2. The transfer belt device according to claim 1, wherein the bias voltage applied by the bias applying means when detecting the contact / separation state is a constant voltage. 3. The transfer belt device according to claim 1, wherein an upper limit is set for the bias voltage applied by the bias applying means when the contact / separation state is detected. 4. Before the contacting / separating operation of the transfer belt, a bias voltage is applied by the bias applying means and a contacting / separating state is detected by the contact / separation detecting means,
The transfer belt device according to claim 1, wherein the contacting / separating operation is performed only when the desired contacting / separating state is not achieved. 5. In response to the contact / separation detection of the transfer belt by the contact / separation detection means, a series of operations for performing the contact / separation operation by the belt contact / separation means is performed once, and the contact / separation detection is performed again. 2. The transfer belt device according to claim 1, wherein, when the desired contact / separation state is not detected, the series of operations is repeated until the desired contact / separation state is detected. 6. A series of operations for performing the contacting / separating operation by the belt contacting / separating means is performed once in response to the contact / separation detection of the transfer belt by the contacting / separating detection means, and a desired contact / separation state is obtained. When it is not detected that the contact state is detected, when the series of operations is repeated until the desired contact / separation state is detected, when the number of repetitions exceeds at least 2, an abnormality display means for displaying an abnormality to the user is provided. The transfer belt device according to claim 1, wherein: