JPH0616192B2 - Copier abnormal condition determination method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for determining an abnormal state of a copying machine.

<Prior Art> Conventionally, a surface potential sensor or a toner concentration sensor is attached to detect the operating state of a copying function executing unit of a copying machine, for example, a high voltage unit for applying a high voltage to a charging charger or a peripheral portion of the charging charger. Copiers are provided.

In such a copying machine, if the sensor section including the sensor and its control circuit is operating normally, it is possible to accurately detect whether or not the above operating state is proper, and it is promptly inappropriate. A proper copy can be obtained by dealing with various operating states. Further, when the detection signal of the sensor is out of the allowable range, it is possible to determine that the copy function performing unit is in an abnormal state and take measures against the abnormal state.

<Problems to be Solved by the Invention> However, conventionally, even if it is possible to detect that an abnormality has occurred in any part of the copy function execution unit, which part of the copy function execution unit has a failure? It was not possible to identify and determine until. So, for example,
At the time of maintenance, it is complicated to specify which part should be repaired, and the maintenance work cannot always be performed well.

Further, in the copying machine as described above, it is necessary to detect whether or not the sensor unit is normal, because an abnormality may occur not only in the copy function performing unit but also in the sensor unit.

Among the abnormalities that actually occur, the frequency of occurrence of abnormalities in the developing device for forming the toner image and the toner concentration sensor portion is high. That is, abnormalities due to toner depletion, contamination of the sensor surface with toner, and the like occur more frequently than abnormalities in other copying function executing units and surface potential sensor units. Therefore, it is preferable that at least the occurrence of the abnormality in the developing device or the toner concentration sensor section is detected separately from the abnormality in the other sections. If it becomes possible to determine such an abnormal place, the maintenance work will be significantly reduced.

Therefore, an object of the present invention is to solve the above-mentioned technical problems and to appropriately specify the location of the abnormality while considering the possibility of the abnormality in the sensor section. An object of the present invention is to provide a method for determining an abnormal state of a copying machine, which is capable of detecting an abnormality of a copy separately from other abnormalities.

<Means and Actions for Solving the Problems> In order to achieve the above object, an abnormal state determining method for a copying machine according to the present invention includes a photoconductor and a charging unit that uniformly charges the surface of the photoconductor. Means for exposing the charged surface of the photoconductor to form an electrostatic latent image on the surface of the photoconductor, developing means for developing the formed electrostatic latent image into a toner image, and the charging means. A surface potential sensor unit including a surface potential sensor for detecting the surface potential of the photoconductor after charging and a control circuit for controlling the surface potential sensor unit, a toner density sensor for detecting the density of the toner image, and the control unit A toner density sensor unit including a control circuit, and is applied to a copying machine in which the density of a toner image monotonously increases or decreases with an increase in the surface potential of a photoconductor to be detected by the surface potential sensor. A method for determining an abnormal state based on each output of the surface potential sensor and the toner concentration sensor, the abnormality state determining method comprising: a predetermined first potential and a predetermined second potential higher than the first potential. Is defined as a range of appropriate values of the surface potential of the photoconductor to be detected by the surface potential sensor, and a predetermined first concentration corresponding to the first potential and a predetermined concentration corresponding to the second potential. Is defined as a range of an appropriate value of the density of the toner image to be detected by the toner density sensor, and the surface potential of the photoconductor detected by the surface potential sensor is the first potential. When the density of the toner image detected by the toner density sensor deviates from the proper value range between the first density and the second density to the first density side, and Surface potential The surface potential of the photoconductor detected by the sensor is equal to or lower than the second potential, and the density of the toner image detected by the toner density sensor is within a range of an appropriate value between the first density and the second density. When it deviates to the second density side, it is determined that an abnormality has occurred in the toner density sensor unit or the developing unit, and the surface potential of the photoconductor detected by the surface potential sensor is the first potential. Lower than that, and when the density of the toner image detected by the toner density sensor is a value within a range of an appropriate value between the first density and the second density, and detected by the surface potential sensor. The surface potential of the photoconductor is higher than the second potential, and the density of the toner image detected by the toner density sensor is a value within an appropriate value range between the first density and the second density. Sometimes the above surface potential Wherein the determining that an abnormality in the capacitors section has occurred.

In this method, the correlation between the surface potential of the photoconductor to be detected by the surface potential sensor and the density of the toner image is used. That is, as the surface potential of the photoconductor increases, the density of the toner image monotonically increases or decreases. Therefore, the range between the predetermined first potential and the second potential is set as the range of the appropriate value of the surface potential of the photoconductor. Then, a range between the first density corresponding to the first potential and the second density corresponding to the second potential is determined as a range of the appropriate value of the density of the toner image.

If the surface potential detected by the surface potential sensor is equal to or higher than the first potential, but the density of the toner image detected by the toner density sensor deviates from the proper value range to the first density side, 2 The detection results of the two sensors are inconsistent and inconsistent. Therefore, it can be determined that an abnormality has occurred in the toner concentration sensor unit including the toner concentration sensor that has detected the abnormal value, or that the developing unit that forms the toner image has an abnormality.

The reason why this determination is valid will be described below.

According to the present invention, for example, in a copying machine in which the higher the surface potential of the photoreceptor is, the higher the density of the toner image is, the surface potential detected by the surface potential sensor is not below the lower limit of the appropriate value, but the toner concentration sensor is not. When the density of the toner image detected by is abnormally low, it is determined that the developing unit or the toner density sensor unit has an abnormality.

The reason why such discrimination is appropriate is clear in view of the empirical fact that a situation in which two or more constituent parts are abnormal at the same time hardly occurs.

That is, when the surface potential detected by the surface potential sensor is equal to or higher than the lower limit of the appropriate value and the density of the toner image detected by the toner density sensor is abnormally low, both the developing unit and the toner density sensor unit are detected. If it is normal, there is no choice but to consider that the charging means and the surface potential sensor section are out of order at the same time. This is because if the charging means is normal and the surface potential sensor is abnormal,
The actual surface potential of the photoconductor should be normal value, the toner image density should be proper value, and if the charging means is abnormal and the surface potential sensor is normal, the surface potential sensor is This is because the surface potential of the photoconductor to be detected should be lower than the proper value range. Therefore, the surface potential of the photoconductor is lowered due to the failure of the charging means, and the surface potential of the photoconductor is erroneously detected as a value within the proper range due to the failure of the surface potential sensor unit, and the toner concentration sensor is There is no choice but to consider that the density of the low toner image is detected.

However, this is contrary to the empirical fact that it is rare that two components fail at the same time,
In practice, there is no need to consider. Therefore, it can be said that it is most appropriate to determine that there is an abnormality in the developing unit or the toner concentration sensor unit.

Similarly, although the surface potential sensor detects that the surface potential of the photoconductor is equal to or lower than the second potential, the toner image density detected by the toner density sensor deviates from the proper value range to the second density side. For example, it can be determined that an abnormality has occurred in the toner concentration sensor unit or the developing unit.

In this way, the abnormality of the toner concentration sensor unit or the developing unit is detected separately from other abnormalities.

On the other hand, in the present invention, the surface potential of the photoconductor detected by the surface potential sensor is lower than the first potential, and the density of the toner image detected by the toner density sensor is the first density and the second density. , And the toner image detected by the toner concentration sensor when the surface potential of the photoconductor detected by the surface potential sensor is higher than the second potential. When the density is within the range of the appropriate value between the first density and the second density, it is determined that the surface potential sensor unit is abnormal.

According to empirical facts, the abnormality of the surface potential sensor rarely occurs, but it is not none. Therefore, it is necessary to consider the occurrence of abnormality of the surface potential sensor.

Therefore, when the detection result of the toner concentration sensor is proper but the detection result of the surface potential sensor is abnormal, it is determined that the surface potential sensor including the surface potential sensor and its control circuit is abnormal. To be done. Ie 2
Since the outputs of the two sensors are not matched, it is considered that one of the sensor units is abnormal, but the output of the toner concentration sensor is correct, so the surface potential sensor unit is abnormal. It is determined to be a thing.

As described above, according to the present invention, the location of the abnormality is determined in consideration of the possibility of the abnormality in the surface potential sensor unit and the toner concentration sensor unit.

Note that, for example, the surface potential detected by the surface potential sensor becomes higher than the second potential due to the abnormality in the charging unit, and at the same time, the toner image density becomes higher than the second potential due to the abnormality in the developing unit. It may be possible that the value becomes lower than the value corresponding to the electric potential, resulting in an appropriate value. However, in the light of the empirical fact that it is almost impossible for the two components to fail at the same time, it is rational to determine that the surface potential sensor has an abnormality in the above case. It will be understood.

The surface potential of the photoconductor detected by the surface potential sensor is lower than the first potential, and the density of the toner image detected by the toner density sensor is the first density and the second density.
When deviating from the proper value range between the density and the first density side, and when the surface potential of the photoconductor detected by the surface potential sensor is higher than the second potential, and
If the density of the toner image detected by the toner density sensor is within the range of the appropriate value between the first density and the second density,
When it deviates to the density side, it is preferable to determine that an abnormality has occurred in the charging means.

By doing so, it is possible to detect the abnormality of the charging unit by distinguishing it from other abnormalities. That is, if the surface potential of the photoconductor detected by the surface potential sensor is lower than the first potential, the toner image density detected by this toner density sensor is from the proper value to the first density unless the toner density sensor is abnormal. The value deviates to the side. That is, in this case, although the respective detection results of the two sensors are abnormal values, there is no contradiction between the detection results of the two sensors. Therefore, each of the sensor units including the two sensors that have detected an abnormal value is normal,
It is considered that, as a result of the abnormality in the charging means, both the surface potential and the toner image density have abnormal values.

Even when the surface potential of the photoconductor detected by the surface potential sensor is higher than the second potential and the density of the toner image detected by the toner density sensor deviates from the proper value range to the second density side. It is the same.

The state where the outputs of the two sensors take abnormal values is
It can occur even when both the surface potential sensor unit and the toner concentration sensor unit are out of order. However, according to empirical facts, it is almost impossible for the two sensor units to fail at the same time. Furthermore, it is almost never that the two constituent parts are in an abnormal state at the same time, and it is practically sufficient to be able to cope with the occurrence of any one of the abnormalities in order to identify the failure point.

Therefore, when the outputs of the two sensors are abnormal, there is almost no room to determine that the surface potential sensor unit and the toner concentration sensor unit have failed at the same time. Therefore, it can be determined that the charging unit is abnormal.

<Example> Hereinafter, detailed description will be given with reference to the accompanying drawings illustrating an example.

FIG. 1 is a schematic diagram showing a configuration of a main part of a copying machine. The pre-exposure lamp (11), the charger (12), the surface potential sensor ( 13), blank lamp (14), developing device (15), pre-transfer charge elimination lamp (1
6), a transfer charger (17), a separation charger (18), a toner concentration sensor (19), and a cleaner (20) are attached in this order. Incidentally, (21) is a high voltage unit for applying a high DC voltage to the charger (12).
The charging means is constituted by (21) and the charger (12).

Further, (3) is an optical system for exposing the document on the document table (31) to form a document image on the photoconductor drum (1), including a light source (32) and a reflecting mirror (33). ) (34) and (35), the lens (36), and the reflecting mirror (37), the document image can be formed in the exposure area (E) of the photosensitive drum (1). Reference numeral (38) is a black simulated original and is attached to the original placing table (31) at a predetermined distance from the original setting area on the home position side of the light source (32).

Further, (4) is a copy paper transporting section, and a paper feed roller (42) for taking out the copy paper (P) in the paper feed cassette (41) one by one, a paper feed path
(43), the registration roller (44) that conveys the copy paper (P) in synchronization with the photosensitive drum (1), and the copy paper (P) separated from the photosensitive drum (1) by the separation charger (18). It has a conveyor belt (45) for conveying, a fixing roller (46), and a tray (47).

With the above configuration, the photoconductor drum (1) uniformly charged by the charging charger (12) every time the copying operation is performed.
In the exposure area (E), first, an electrostatic latent image corresponding to the simulated original (38) is formed, and after the surface potential is detected by the surface potential sensor (13), a toner image is formed by the developing device (15). After being visualized, the toner density sensor (19) detects the density of the toner image, and the cleaner (20) collects the toner. At this time, the transfer charger (17) and the separation charger (18) are made inoperative.

Next, an electrostatic latent image corresponding to the original image exposed by the light source (32) is formed, visualized as a toner image by the developing device (15), and the toner image is transferred by the transfer charger (17) to the copy paper (P ), The copy paper (P) is peeled off by the separation charger (18), and then the residual toner is collected on the photoconductor drum (1) by the cleaner (20). In this case, the voltage applied to the charger (12) is
(38) The toner amount that is set to an appropriate value based on the detection signal of the surface potential sensor (13) during exposure and that is adsorbed on the surface of the photoconductor drum (1) is the toner density during exposure of the simulated original (38). Sensor (1
Since a proper value is set based on the detection signal of 9), a high quality copy can be obtained.

FIG. 3 is a diagram showing the output characteristics of the surface potential sensor (13). The output SV of the surface potential sensor monotonically increases as the surface potential VB of the photosensitive drum (1) increases. And
When the charging means including the charging charger (12) and the high voltage unit (21) is normal, when an electrostatic latent image corresponding to the simulated original (38) is formed on the surface of the photoconductor drum (1), Photoreceptor drum to be detected by surface potential sensor (13)
The surface potential VB of (1) takes an appropriate value between VL as the first potential and VH as the second potential. That is, if the surface potential sensor unit including the surface potential sensor (13) and its control circuit (not shown) is normal and the charging means is normal, the surface potential when the simulated original (38) is copied. The output signal SV of the sensor (13) takes a value within the region R1.

FIG. 4 is a diagram showing the output characteristics of the toner density sensor (19). The output DB of the toner concentration sensor (19) monotonously decreases as the surface potential VB increases. This toner concentration sensor (1
In 9), the lower the density of the toner image, the lower the output signal is output. Therefore, in the end, in this embodiment, the photosensitive drum
As the surface potential of (1) increases, the density of the toner image increases monotonically (Note that when the toner is positively charged,
As the surface potential VB of the photosensitive drum (1) increases, the density of the toner image monotonously decreases. ).

For the output signal DB of the toner concentration sensor (19), the value DH corresponding to the above-mentioned potential VL and the value DL corresponding to the potential VH are determined. The value DH is the output of the toner density sensor (19) corresponding to the first density, and the value DL is the output of the toner density sensor (19) corresponding to the second density. Then, the region R2 between the values DL and DH is a region of an appropriate value corresponding to the region R1. That is, the charging charger (1
2), the high-pressure unit (21), the developing device (15), and the toner concentration sensor (19) and its control circuit (not shown).
The output DB of the toner density sensor (19) when the toner image corresponding to (38) is formed takes a value within the region R2.

FIG. 2 is a flow chart for explaining a process for identifying and detecting an abnormal place. Mock manuscript (38)
When the abnormality determination processing is performed by forming the toner image corresponding to the above, the transfer charger (17) and the separation charger (18) are in the non-operating state as described above, and therefore these are not the targets of the abnormality determination processing described below. Is. In addition, the pre-exposure lamp (11), blank lamp (14) and pre-transfer charge erasing lamp
The detection of the abnormality relating to (16) is performed by a process different from the process of FIG. That is, these abnormalities are outside the scope of the abnormality determination processing described below.

In the step, the detection signal SV of the surface potential sensor (13) when the simulated original (38) is exposed is obtained, and in the step, the detection is performed based on the graph of FIG. 3 previously stored in the memory of the microcomputer (not shown). Signal SV
The surface potential VB corresponding to is calculated, and it is determined in step whether or not the surface potential VB is within the range of the region R1. If it is above the region R1, the abnormality flag 2 is set in the step, and the region R1 is set.
If it is below, the abnormality flag 1 is set in the step, and if it is within the range of the region R1, none of the flags is set, and then the determination and processing in the steps and below are performed.

In the step, the detection signal DB of the toner density sensor (19) when the simulated original document (38) is exposed is obtained, and in the step, the detection signal DB is within the detection signal region R2 corresponding to the surface potential region R1 ( (See FIG. 4).

If the detection signal DB is smaller than the lower limit value DL of the region R2, it is determined whether or not the abnormality flag 2 is set in the step. If the abnormality flag 2 is set, the surface potential is abnormal in the step. It is determined that the charging means including the high-voltage unit (21) and the charger (12) is abnormal, and the abnormality flag 2
If is not set, the toner amount is abnormally large in the step, and the toner replenishing section (not shown) or the toner concentration sensor (1) which constitutes the developing means together with the developing device (15).
It is determined that the toner concentration sensor unit including 9) and its control circuit is abnormal.

When the positive judgment is made in the step and the abnormality detection processing of the step is performed, the surface potential sensor
This is a case where the surface potential detected by (13) is abnormally high and the toner concentration detected by the toner concentration sensor (19) is abnormally high. Therefore, in this case, two sensors (13) (1
It can be said that there is no contradiction between the outputs of 9) and there is consistency.
In this case, the charger (12) and high voltage unit (21)
There is a possibility that an abnormality has occurred in the charging means including the above, or the respective sensor units including the two sensors (13) and (19) are simultaneously broken. However, empirical facts indicate that there is almost no simultaneous failure of the two sensors. Therefore, in the step, it may be determined that the failure of the charging means has occurred as described above.

On the other hand, when the negative judgment is made in the step and the abnormality detection processing of the step is performed, the surface potential VB detected by the surface potential sensor (13) is the upper limit value V of the appropriate value.
This is the case where the toner density detected by the toner density sensor (13) is abnormally high even though it is H or less. That is,
In this case, there is a contradiction between the outputs of the two sensors (13) and (19). Since the output of the surface potential sensor (13) is an appropriate value, it can be determined that the developing unit or the toner concentration sensor unit is out of order.

The reason why such discrimination is appropriate is clear in view of the empirical fact that a situation in which two or more constituent parts are abnormal at the same time hardly occurs.

That is, the surface potential VB detected by the surface potential sensor (13)
Is less than or equal to the upper limit value VH of the appropriate range, and the density of the toner image detected by the toner density sensor (13) is abnormally high, it is assumed that both the developing unit and the toner density sensor unit are normal. In this case, it is inevitable that the charging means and the surface potential sensor section are out of order at the same time. That is,
If the charging unit is normal and the surface potential sensor section is abnormal, the actual surface potential should be normal and the toner image density should be proper. If the charging means is abnormal and the surface potential sensor section is normal, the surface potential VB detected by the surface potential sensor (13) should be higher than the proper value range. Therefore, the actual surface potential becomes high due to the failure of the charging means, and the surface potential of the photosensitive drum (1) is erroneously detected as a value within the proper range due to the failure of the surface potential sensor unit, and Concentration sensor (19)
Can only be considered to have correctly detected the high toner image density.

However, this is contrary to the empirical fact that it is rare that two components fail at the same time,
In practice, there is no need to consider. Therefore, as described above, it is concluded that it is most appropriate to determine that the developing unit or the toner concentration sensor unit is abnormal.

As a result of the judgment in the step, if the detection signal DB is larger than the upper limit value DH of the region R2, it is judged whether or not the abnormality flag 1 is set in the step, and if the abnormality flag 1 is set, in the step, It is determined that the surface potential is abnormally low and the charging means including the high-voltage unit (21) and the charger (12) is abnormal. On the other hand, if the abnormality flag 1 is not set, the toner amount is abnormal in step. Very few, developing device
Toner replenishment section (not shown) that forms developing means with (15)
Alternatively, it is determined that the toner density sensor section including the toner density sensor (19) and its control circuit is abnormal.

When the positive judgment is made in the step and the abnormality detection processing of the step is performed, the surface potential sensor
This is a case where the potential detected by (13) is abnormally low and the toner concentration detected by the toner concentration sensor (19) is abnormally low. Therefore, in this case, two sensors (13) (19)
The output of is consistent and consistent. In this case, the charging means including the charger (12) and the high voltage unit (21) may be abnormal, or the respective sensor units including the two sensors (13) and (19) may be broken at the same time. There is. However, as described above, there is almost no possibility that the two sensors will fail at the same time. Therefore, in the step, it can be determined that the failure of the charging means has occurred.

On the other hand, when the negative judgment is made in the step and the abnormality detection process of the step is performed, the surface potential VB detected by the surface potential sensor (13) is the lower limit value V of the appropriate value.
This is the case where the toner density detected by the toner density sensor (13) is abnormally low even though it is L or more. That is,
In this case, there is a contradiction between the outputs of the two sensors (13) and (19). Since the output of the surface potential sensor (13) is an appropriate value, it can be determined that the developing unit or the toner concentration sensor unit is out of order.

The reason why the above determination in step is appropriate is the same as the reason why the determination in step is appropriate.

Result of judgment in step and, detection signal DB
Is within the range of the area R2, it is determined in step whether the abnormality flag 1 or the abnormality flag 2 is set.

If the abnormality flag 1 is set, the output value of the surface potential sensor (13) is abnormal and the surface potential sensor section including the surface potential sensor (13) and its control circuit is abnormal in step. If the abnormality flag 2 is set, it is determined in step that the surface potential sensor unit including the surface potential sensor (13) and its control circuit is abnormal. On the other hand, if neither flag is set, the toner replenishment amount (represented by not shown) is controlled in step to calculate the toner replenishment amount to be replenished, and thereafter, the copying operation is performed in proper density in step. To do.

If the step or step makes a positive determination, it means that the toner concentration is within the proper range.
This is the case where the surface potential VB detected by the surface potential sensor (13) is abnormally low or abnormally high. That is, two sensors (1
3) The output of (19) is inconsistent. However, since the output DB of the toner concentration sensor (19) is within the proper value range, it may be judged that the surface potential sensor is abnormal.

Abnormalities in the output of the surface potential sensor (13) can occur not only when the surface potential sensor unit fails, but also when the charging means including the charger (12) fails. However, if the charging means is out of order, the density of the toner image formed on the surface of the photosensitive drum (9) cannot take an appropriate value, so a positive judgment is made in step or.
The abnormality detection process in step or is performed.

For example, the surface potential VB detected by the surface potential sensor (19) has an abnormally high value due to the failure of the charging means, and at the same time, the failure of the developing means including the developing device (15) causes the toner. A situation may occur in which the concentration becomes an appropriate value. However, according to empirical facts, it can be said that the two constituent parts do not fail at the same time. Therefore, in practice, it is not necessary to consider the possibility that the charging means and the developing means fail at the same time. .

Therefore, as described above, although the density of the toner image is an appropriate value, the surface potential VB detected by the surface potential sensor (13) is
If takes an abnormal value, it can be determined that the surface potential sensor (13) is abnormal.

As described above, according to the present embodiment, the above-described determination processing is performed for each copy operation, and the toner concentration is set only when the detection signals of the two sensors (13) and (19) are within the proper range. By controlling, the copying operation at the proper density is performed. If an abnormality occurs in any of the charging unit, the developing unit, the surface potential sensor unit, and the toner concentration sensor unit, the abnormality detection process is performed and the copying operation is not performed. As a result, the toner image density control may be performed based on the abnormal detection signal when the sensor unit has a failure, and an undesired copying operation is wasted when a failure occurs in the charging unit or the developing unit. Can be prevented. Therefore, it is possible to reliably prevent waste of toner, copying machines and the like.

Further, according to the present embodiment, the abnormality is caused in the developing unit or the toner concentration sensor unit, the abnormality is generated in the charging unit, and the abnormality is generated in the surface potential sensor unit. The state is detected separately. Therefore, it is possible to satisfactorily specify the location of the abnormality.
As a result, for example, at the time of maintenance, the work of searching for a failure location is reduced. Therefore, the maintenance work is remarkably reduced as a whole.

The present invention is not limited to the above-described embodiment, and for example, when a sensor for detecting the remaining amount of toner in the developing device (15) is attached and the detection signal of the toner concentration sensor is out of the proper range. , Whether the toner amount in the developing device (15) is abnormal or not, and surely confirm the toner concentration sensor.
It is possible to determine the abnormality of (19), and instead of detecting the surface potential of the photoconductor drum (1) when the simulated original document (38) is exposed, the dark potential of the photoconductor drum (1) is detected. In addition, various design changes can be made without departing from the scope of the present invention.

<Effect> As described above, according to the present invention, the toner concentration detected by the toner concentration sensor is an inappropriate value even though the surface potential detected by the surface potential sensor is an appropriate value. It is possible to detect an abnormality of the developing unit or the toner concentration sensor section, which has a higher frequency of occurrence than the above abnormality, separately from other abnormalities. Therefore, it is possible to satisfactorily identify the location where the abnormality has occurred, and, for example, maintenance work can be significantly reduced.

Further, according to the present invention, when the surface potential detected by the surface potential sensor is an abnormal value even though the density of the toner image detected by the toner density sensor is an appropriate value, the abnormality of the surface potential sensor unit causes another abnormality. Are distinguished from each other.

As described above, according to the present invention, it is possible to satisfactorily determine the location of the abnormality while considering the possibility of the abnormality of the toner concentration sensor unit or the surface potential sensor unit.

Further, based on the fact that both the surface potential detected by the surface potential sensor and the toner image density detected by the toner concentration sensor are abnormal, the abnormality of the charging means can be distinguished from other abnormalities, and thus, It is possible to better identify the location of the abnormality. As a result, for example, the maintenance work can be further reduced.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a main part of a copying machine, FIG. 2 is a flow chart for explaining abnormality determination processing, FIG. 3 is a diagram showing characteristics of a surface potential sensor, and FIG. 4 is a toner concentration sensor. It is a figure which shows the characteristic of. (1) ... Photosensitive drum as photoconductor, (3) ... Optical system, (12) ... Charging charger, (13) ... Surface potential sensor, (15) ... Developing device, (19) ... Toner density sensor, ( 21) ... High-voltage unit, (38) ... Simulated manuscript

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Claims (2)

[Claims] 1. A photoreceptor, charging means for uniformly charging the surface of the photoreceptor, and means for exposing the charged surface of the photoreceptor to form an electrostatic latent image on the surface of the photoreceptor. A developing means for developing the formed electrostatic latent image into a toner image, a surface potential sensor for detecting the surface potential of the photoconductor after the charging by the charging means, and a control circuit for controlling the surface potential sensor. A surface potential sensor section including the surface potential sensor section and a toner density sensor section including a toner density sensor for detecting the density of the toner image and a control circuit for controlling the toner density sensor, and the surface potential of the photoconductor to be detected by the surface potential sensor. It is applied to a copying machine in which the density of a toner image monotonically increases or decreases with an increase, and an abnormal condition for determining an abnormal portion based on each output of the surface potential sensor and the toner density sensor. A determination method, wherein a range between a predetermined first potential and a predetermined second potential higher than the first potential is set to an appropriate value of the surface potential of the photoconductor to be detected by the surface potential sensor. The range between the predetermined first density corresponding to the first potential and the predetermined second density corresponding to the second potential is defined as the range of the density of the toner image to be detected by the toner density sensor. The surface potential of the photoconductor detected by the surface potential sensor is equal to or higher than the first potential, and the toner image density detected by the toner density sensor is the first density and the second density. When deviating from the proper value range between the density and the first density side, and when the surface potential of the photoconductor detected by the surface potential sensor is equal to or lower than the second potential, and the toner The concentration sensor detects When the density of the formed toner image deviates from the range of the appropriate value between the first density and the second density to the second density side, an abnormality occurs in the toner density sensor unit or the developing unit. The surface potential of the photoconductor detected by the surface potential sensor is lower than the first potential, and the density of the toner image detected by the toner density sensor is the first density and the second density. , The surface potential of the photoconductor detected by the surface potential sensor is higher than the second potential, and the toner image detected by the toner concentration sensor is When the density is within the range of the appropriate value between the first density and the second density, it is determined that an abnormality has occurred in the surface potential sensor section. How to determine. 2. The surface potential of the photoconductor detected by the surface potential sensor is lower than the first potential, and the density of the toner image detected by the toner density sensor is the first density and the second density. When deviating from the range of the appropriate value to the first density side, and the surface potential of the photoconductor detected by the surface potential sensor is higher than the second potential,
Further, when the density of the toner image detected by the toner density sensor deviates from the proper value range between the first density and the second density to the second density side, an abnormality occurs in the charging means. The abnormal state determination method for a copying machine according to claim 1, wherein the abnormal state determination is performed as follows.