JP7443901B2 - Charging device and image forming device - Google Patents

Description

The present invention relates to a charging device and an image forming apparatus including the charging device.

2. Description of the Related Art As a device for charging a photoreceptor in an electrophotographic image forming apparatus, a charging device that applies a bias voltage in which a DC component and an AC component are superimposed to a charging member is known. According to this charging device, when the peak-to-peak voltage value Vpp of the AC component reaches twice the charging start voltage due to the DC component, the charging potential on the photoreceptor converges, so that the photoreceptor can be charged uniformly. Become.

The above-mentioned charging device has a problem in that it is difficult to set an appropriate peak-to-peak voltage value due to variations in the characteristics of the charging member, changes in the surrounding environment, the type of image carrier, and the like. Therefore, in Patent Document 1, an appropriate peak-to-peak voltage value is determined using an assumed characteristic curve on two-dimensional coordinates representing the relationship between the peak-to-peak voltage value Vpp and the DC current value Idc between the charging member and the image carrier. A charging device has been proposed that sets .

Japanese Patent Application Publication No. 2007-199094

In the charging device proposed in Patent Document 1, an appropriate peak-to-peak voltage value can be set even when the electrical resistance value and discharge starting voltage increase due to repeated energization by applying high voltage over a long period of time. . However, if the electrical resistance value of the charging member exceeds the limit, the discharge from the charging member to the image carrier becomes unstable, which may result in uneven image quality.

SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to provide a charging device and an image forming apparatus that can determine the lifespan of a charging member without measuring the electrical resistance value of the charging member.

In order to solve the above problems, a charging device according to the present invention includes a charging member that contacts or faces an image carrier and charges the surface of the image carrier, and an oscillating voltage in which a DC voltage and an AC voltage are superimposed. a high voltage generation circuit that applies to the charging member; and a control unit that controls the peak-to-peak voltage value Vpp of the alternating current voltage; the control unit controls the peak-to-peak voltage value Vpp; As a variable representing an assumed characteristic curve on two-dimensional coordinates representing the relationship between DC current value Idc and The two different low-voltage side peak-to-peak voltage values Vpp(A) and Vpp(B) that are different from each other, and the high-voltage side peak-to-peak voltage value Vpp(C) that is assumed to be higher voltage than the voltage value at the inflection point, are table data set in advance in association with fluctuation factors in the charging characteristics of the charging member; and voltage values between the two low voltage side peaks Vpp(A), Vpp(B) and the high voltage side peaks corresponding to the fluctuation factors; The voltage value Vpp(C) is obtained from the table data, and the oscillating voltage on which the AC voltage indicating the two obtained low voltage side peak-to-peak voltage values Vpp(A) and Vpp(B) is superimposed is obtained from the table data. Coordinates A (Vpp (A), Idc (A)), B (Vpp (B), When the high voltage generation circuit applies the oscillating voltage, in which the AC voltage indicating the acquired high voltage side peak-to-peak voltage value Vpp (C) is superimposed on the straight line L1 passing through Idc (B)), to the charging member. Corresponds to the intersection of the straight line L2, which passes through the coordinates C (Vpp(C), Idc(C)) representing the DC current value Idc(C) measured in , and is parallel to the coordinate axis representing the peak-to-peak voltage value Vpp. a voltage control unit that sets the peak-to-peak voltage value Vpp as an appropriate peak-to-peak voltage value Vpp(O); and a vicinity of the appropriate peak-to-peak voltage value Vpp(O) when the electrical resistance value of the charging member reaches an upper limit. The high-voltage side peak-to-peak voltage value Vpp(C) is set to , and the appropriate peak-to-peak voltage value Vpp(O) set by the voltage control unit is equal to or higher than the high-voltage side peak-to-peak voltage value Vpp(C). In this case, the charging member includes a lifespan determination unit that determines that the charging member has reached the end of its lifespan.

In the charging device according to the present invention, a temperature measurement unit that measures the temperature around the charging device as the variation factor; a humidity measurement unit that measures the humidity around the charging device as the variation factor;
The voltage control unit is configured to control the two low-voltage peak-to-peak voltage values Vpp(A), Vpp(B) and the high-voltage peak-to-peak voltage value Vpp(C) corresponding to the measured temperature and humidity. and may be configured to be acquired from the table data.

In the charging device according to the present invention, the image carrier may include an amorphous silicon film.

Further, an image forming apparatus according to the present invention is characterized by comprising any one of the above-mentioned charging devices and a display section that displays information representing a result of determination by the life determination section.

Further, an image forming apparatus according to the present invention is characterized in that it includes any one of the above-mentioned charging devices and a transmitting section that transmits information representing a result of determination by the life determining section.

According to the present invention, the lifespan of a charging member can be determined without measuring the electrical resistance value of the charging member.

FIG. 1 is a block diagram of a charging device according to an embodiment of the present invention. It is an assumed characteristic curve showing the relationship between the peak-to-peak voltage value Vpp and the DC current value Idc according to one embodiment of the present invention. This is a characteristic curve when the DC voltage value Vdc, temperature, and humidity are fixed. This is a characteristic curve when the temperature is changed. This is a characteristic curve when the humidity is changed. 3 is a table showing table data according to an embodiment of the present invention. It is a flowchart which shows the procedure of the lifespan determination process performed by the control part 4 based on one Embodiment of this invention.

Hereinafter, a charging device 11 of an image forming apparatus 10 according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of the charging device 11. As shown in FIG. The image forming apparatus 10 is a printer that forms toner images using an electrophotographic method, and includes an image carrier 1, a charging device 11, an exposure device, a developing device, a transfer roller, a fixing device, and the like.

The image carrier 1 includes a photoconductor drum having a photoconductor in which an amorphous silicon layer, which is a positively charging photoconductor, is deposited on the surface of an aluminum cylinder. Driven to rotate at a constant speed.

The charging device 11 is arranged to be in contact with the image carrier 1, and includes a charging member 2 that charges the surface of the image carrier 1, and a high voltage that applies an oscillating voltage in which a DC voltage and an AC voltage are superimposed to the charging member 2. It includes a generation circuit 3 and a control section 4 that controls a peak-to-peak voltage value Vpp of the AC voltage.

The charging member 2 includes a core metal 2a and an echlorohydrin rubber layer 2b, which is an elastic material having conductivity and covers the core metal 2a.

The high voltage generation circuit 3 includes an AC constant voltage power supply 3c that generates a predetermined sinusoidal AC voltage from a low voltage DC voltage modulated into pulses using a step-up transformer, and a low voltage DC voltage modulated into pulses using a step-up transformer. A DC constant voltage power source 3b that rectifies a sinusoidal AC voltage generated by a rectifier to generate a predetermined DC voltage, and a DC current measurement unit that measures and detects a DC current value Idc between the charging member 2 and the image carrier 1. A portion 3a is provided.

The control section 4 includes a table data storage section 4b, a voltage control section 4a, a lifespan determination section 4c, and an electronic data creation section 4d. The control unit 4 may be realized by hardware such as an integrated circuit, a processor and software, or a combination thereof. A processor performs various processes by reading and executing programs stored in memory. As the processor, for example, a CPU (Central Processing Unit) is used. The memory includes storage media such as ROM (Read Only Memory), RAM (Random Access Memory), and EEPROM (Electrically Erasable Programmable Read Only Memory). A control program used to control each part of the image forming apparatus 10 is stored in the memory.

When an image forming job is input to the image forming apparatus 10 from an external computer or the like, the charging device 11 charges the image carrier 1 to a predetermined potential, the exposure device writes a latent image on the image carrier 1, and the developing device forms a toner image by developing a latent image using toner, a transfer roller transfers the toner image onto a sheet, and a fixing device heats the toner image to fix it on the sheet.

FIG. 2 is an assumed characteristic curve representing the relationship between the peak-to-peak voltage value Vpp and the DC current value Idc. The table data storage section 4b stores table data in which data used to determine an appropriate peak-to-peak voltage value Vpp(O) corresponding to a factor of variation in the charging characteristics of the charging member 2 is set. The factors that change the charging characteristics of the charging member 2 are, for example, temperature and humidity.

Specifically, the table data includes variables representing assumed characteristic curves on two-dimensional coordinates representing the relationship between the peak-to-peak voltage value Vpp and the DC current value Idc between the charging member 2 and the image carrier 1. As shown in FIG. A peak-to-peak voltage value Vpp(C) on the high voltage side, which is assumed to be on the higher voltage side than the voltage value, is set in advance in correspondence with a variation factor in the charging characteristics of the charging member 2. However, the inflection point means a point where the slope of the assumed characteristic curve changes from positive to substantially 0 when the peak-to-peak voltage value Vpp is increased. Note that the detailed contents of the table data will be described later.

The voltage control section 4a acquires the temperature and humidity near the charging member 2 measured by the temperature measurement section 5 and the humidity measurement section 6 outside the period of image formation processing by the image forming apparatus 10. Specifically, the voltage control unit 4a acquires two low voltage side peak-to-peak voltage values Vpp(A), Vpp(B) and a high voltage side peak-to-peak voltage value Vpp(C) corresponding to the fluctuation factors from the table data. Then, the DC voltage measured when the high voltage generation circuit 3 applies an oscillating voltage on which the AC voltage indicating the two acquired low voltage side peak-to-peak voltage values Vpp(A) and Vpp(B) is superimposed to the charging member 2. Straight line L1 passing through coordinates A (Vpp (A), Idc (A)) and B (Vpp (B), Idc (B)) representing current values Idc (A), Idc (B) and the obtained high voltage side Coordinates C(Vpp(C) representing a DC current value Idc(C) measured when the high voltage generation circuit 3 applies an oscillating voltage on which an AC voltage representing a peak-to-peak voltage value Vpp(C) is superimposed to the charging member 2. ), Idc(C)) and a straight line L2 parallel to the coordinate axis representing the peak-to-peak voltage value Vpp, the peak-to-peak voltage value Vpp corresponding to the intersection is set as the appropriate peak-to-peak voltage value Vpp(O).

The life determination unit 4c determines the life of the charging member 2 using the high-voltage side peak-to-peak voltage value Vpp(C) and the appropriate peak-to-peak voltage value Vpp(O), and sends the determination result to the electronic data creation unit 4d. The details of the lifespan determination process will be described later.

The electronic data creation section 4d creates electronic data representing the result determined by the lifespan determination section 4c. The electronic data includes image data representing an image displayed on the display section 7 and e-mail data transmitted by the transmitting section 8 .

The display section 7 is, for example, a liquid crystal display panel, receives the image data created by the electronic data creation section 4d, and displays an image using the received image data.

The transmitter 8 is, for example, a communication interface, receives the e-mail data created by the electronic data creator 4d, and transmits the received e-mail data to a predetermined destination. The predetermined destination is, for example, the e-mail address of a business operator in charge of maintaining the image forming apparatus 10.

Next, the relationship between the electrical resistance value of the charging member 2 and the appropriate peak-to-peak voltage value Vpp(O) will be explained. Since the charging member 2 includes the echlorohydrin rubber layer 2b, the ion conductive agent is unevenly distributed and the electrical resistance value increases by repeating energization by applying a high voltage over a long period of time. As the electrical resistance value increases, the discharge starting voltage also increases, and therefore the appropriate peak-to-peak voltage value Vpp(O) also increases. However, if the discharge starting voltage exceeds the leakage discharge limit, the discharge from the charging member 2 to the image carrier 1 becomes unstable, which may result in uneven image quality. Therefore, the electrical resistance value when the discharge starting voltage reaches the leakage discharge limit is defined as the upper limit electrical resistance value, and when the upper limit electrical resistance value is reached, it can be determined that the charging member 2 has reached the end of its life.

According to experiments, the initial electrical resistance value (initial electrical resistance value) of the charging member 2 at a temperature and humidity of 23° C./50% was approximately 5.0 [logΩ·cm]. Further, the upper limit electrical resistance value at a temperature and humidity of 23° C./50% was 6.5 [logΩ·cm]. Therefore, when the electrical resistance value at a temperature and humidity of 23° C./50% reaches 6.5 [logΩ·cm], it can be determined that the charging member 2 has reached the end of its life.

However, it is difficult to measure the electrical resistance value of the charging member 2 in the image forming apparatus 10 in use. Therefore, in the present embodiment, the lifespan determination section 4c determines the lifespan of the charging member 2 using the inflection point of the characteristic curve representing the relationship between the peak-to-peak voltage value Vpp and the DC current value Idc.

FIG. 3A is a characteristic curve when the DC voltage value Vdc, temperature, and humidity are fixed. The DC voltage value Vdc is 400 [V], and the temperature and humidity are 23° C./50%. The conditions for the electrical resistance value are an initial electrical resistance value and an upper limit electrical resistance value. Since the DC current value Idc is the amount of discharge from the charging member 2 to the image carrier 1, it is considered that there is a correlation with the surface potential of the image carrier 1. There are inflection points in the characteristic curve. In the case of the initial electrical resistance value, Vpp at the inflection point is 1000V, and in the case of the upper limit electrical resistance value, Vpp at the inflection point is 1600V. In both cases, since the DC current value Idc is stable at a peak-to-peak voltage value Vpp that is equal to or higher than the inflection point, the surface potential of the image carrier 1 is stable within the range from the initial electrical resistance value to the upper limit electrical resistance value. It is considered that the properties and uniformity are maintained. On the other hand, when Vpp at the inflection point becomes 1600 V or more, the electrical resistance value of the charging member 2 exceeds the upper limit electrical resistance value, so the stability and uniformity of the surface potential of the image carrier 1 is maintained. It is thought that it will stop dripping.

Therefore, by setting the high voltage side peak-to-peak voltage value Vpp(C) to a value in the vicinity of 1600V, when the appropriate peak-to-peak voltage value Vpp(O) becomes equal to or higher than Vpp(C), the charging member 2 has a lifespan. It can be determined that this has been reached.

FIG. 3B is a characteristic curve when the temperature is changed. The electrical resistance value of the charging member 2 is the upper limit electrical resistance value, the DC voltage value Vdc is fixed at 400 [V], and the humidity is fixed at 50%. When the temperature was changed to 12°C, 23°C, and 33°C under these conditions, the inflection points were 2600V, 1600V, and 1200V, respectively.

FIG. 3C is a characteristic curve when the humidity is changed. The electrical resistance value of the charging member 2 is the upper limit electrical resistance value, the DC voltage value Vdc is fixed at 400 [V], and the temperature is fixed at 23°C. When the humidity was changed to 15%, 50%, and 75% under these conditions, the respective inflection points were 2000V, 1600V, and 1400V.

FIG. 4 is a table showing table data. The table data shows Vpp(A), Vpp(B), and Vpp(C) determined from the above inflection points. As for Vpp(A) and Vpp(B), it is necessary to obtain them from the positive slope part of the characteristic curve, so the Vpp value is set to be smaller than the inflection point of the initial electrical resistance value of the charging member 2 in FIG. 2a. did. Furthermore, since the inflection point changes depending on temperature and humidity, temperature and humidity were each divided into a plurality of ranges, and Vpp(A) and Vpp(B) were set for each combination of the ranges. Regarding the high voltage side peak-to-peak voltage value Vpp(C), considering the detection variation of the appropriate peak-to-peak voltage value Vpp(O), the peak-to-peak voltage value Vpp which is 50V lower than VPP(O) was set as Vpp(C). .

Next, the lifespan determination process of the charging member 2 will be explained. FIG. 5 is a flowchart showing the procedure of the lifespan determination process executed by the control unit 4.

First, the control unit 4 acquires the temperature and humidity measured by the temperature measurement unit 5 and humidity measurement unit 6 (step S01), and sets the low-pressure side peak-to-peak voltage value Vpp(A) corresponding to the acquired temperature and humidity. , Vpp(B) and the high voltage side peak-to-peak voltage value Vpp(C) are acquired from the table data stored in the table data storage section 4b (step S03).

Next, the high voltage generation circuit 3 applies an oscillating voltage (Vdc+Vpp(A)) to the charging member 2, and the DC current measurement unit 3a measures the DC current value Idc( A) is measured (step S05).

Next, the high voltage generation circuit 3 applies an oscillating voltage (Vdc+Vpp(B)) to the charging member 2, and the DC current measurement unit 3a measures the DC current value Idc( B) is measured (step S07).

Next, the control unit 4 derives a straight line L1 passing through the coordinates A (Vpp(A), Idc(A)) and the coordinates B (Vpp(B), Idc(B)) (step S09).

Next, the high voltage generation circuit 3 applies an oscillating voltage (Vdc+Vpp(C)) to the charging member 2, and the DC current measurement unit 3a measures the DC current value Idc( C) is measured (step S11).

Next, the control unit 4 derives a straight line L2 that passes through the coordinates C (Vpp(C), Idc(C)) and is parallel to the coordinate axis representing the peak-to-peak voltage value Vpp (step S13), and The peak-to-peak voltage value Vpp corresponding to the intersection is set as the appropriate peak-to-peak voltage value Vpp(O) (step S15).

Next, the lifespan determination unit 4c determines whether the charging member 2 has reached the end of its lifespan (step S17). Specifically, when the appropriate peak-to-peak voltage value Vpp(O) is greater than or equal to the high-voltage side peak-to-peak voltage value Vpp(C), the life determination unit 4c determines that the charging member 2 has reached the end of its life. When it is determined that the charging member 2 has reached the end of its life, the electronic data creation section 4d creates image data representing the image displayed on the display section 7 and e-mail data transmitted by the transmission section 8. The image data includes, for example, content that prompts replacement of the unit including the charging member 2, content that prompts maintenance of the image forming apparatus 10, and the like. The e-mail data includes information such as the lifespan determination result, Vpp(A), Vpp(B), Vpp(C), machine serial number, unit serial number, counter, energization time, temperature, and humidity. This information may be written in the body of the e-mail in text format, converted into a file in CSV (Comma-Separated Values) format, XML (Extensible Markup Language) format, JSON (JavaScript Object Notation) format, etc. It may also be attached to an email.

According to the charging device 11 according to the present embodiment described above, the high-voltage side peak-to-peak voltage value Vpp(C ), and when the appropriate peak-to-peak voltage value Vpp(O) set by the voltage control unit 4a becomes equal to or higher than the high-voltage side peak-to-peak voltage value Vpp(C), it is determined that the charging member 2 has reached the end of its life. Since the life determination unit 4c is provided, the life of the charging member 2 can be determined without measuring the electrical resistance value of the charging member 2.

Further, since the charging device 11 according to the present embodiment includes the temperature measuring section 5 and the humidity measuring section 6, it is possible to determine the lifespan of the charging member 2 according to the actually measured temperature and humidity.

Furthermore, according to the charging device 11 according to the present embodiment, since the image carrier 1 has the amorphous silicon film, it is easy to measure the DC current value Idc.

Further, since the charging device 11 according to the present embodiment includes the display section 7 that displays information representing the result of the determination by the lifespan determination section 4c, it is possible to inform the user of the image forming apparatus 10 of the result of the lifespan determination. can.

Furthermore, since the charging device 11 according to the present embodiment includes the transmitting section 8 that transmits information representing the determination result by the lifespan determining section 4c, users, administrators, etc. who are located away from the image forming apparatus 10, etc. can be notified of the lifespan determination results.

The above embodiment may be modified as follows.

The lifespan determination process may be performed periodically, or may be performed when a predetermined event occurs as a trigger for the lifespan determination process. For example, it may be executed when the amount of change in at least one of the measured temperature and humidity exceeds a threshold value.

In the embodiment described above, an example is shown in which a photoreceptor drum having a photoreceptor in which an amorphous silicon layer, which is a positively charging photoconductor, is deposited on the surface of an aluminum cylinder is employed as the image carrier 1. The photosensitive drum may be an OPC (Organic Photoconductor) drum having an organic photoconductor or a drum having a photoconductive semiconductor such as selenium. In that case, the positive or negative polarity of the oscillating voltage applied to the charging member 2 may be changed depending on the charging characteristics of the photoreceptor.

In the above embodiment, an example was shown in which the charging member 2 includes the core metal 2a and the echlorohydrin rubber layer 2b, which is an elastic material having conductivity and covers the core metal 2a. , may be covered with fur brush, felt, cloth, etc.

In the above embodiment, the charging member 2 is arranged so as to be in contact with the image carrier 1, but the charging member 2 is arranged so as to face the image carrier 1 at a predetermined distance. Good too.

In the above embodiment, in consideration of detection variations in the appropriate peak-to-peak voltage value Vpp(O), there is an example in which the peak-to-peak voltage value Vpp, which is 50V lower than VPP(O), is set as the high-voltage side peak-to-peak voltage value Vpp(C). Although shown, this is only an example, and Vpp(C) may be set higher than Vpp(O), or Vpp(C) may be set equal to Vpp(O). In short, the high voltage side peak-to-peak voltage value Vpp(C) may be set close to the appropriate peak-to-peak voltage value Vpp(O) when the electrical resistance value of the charging member 2 reaches the upper limit. In other words, the high voltage side peak-to-peak voltage value Vpp(C) must be set within the range of detection variation of the appropriate peak-to-peak voltage value Vpp(O) when the electrical resistance value of the charging member 2 reaches the upper limit. Bye.

1 Image carrier 2 Charging member 3 High pressure generation circuit 4 Control section 4a Voltage control section 4c Lifespan determination section 5 Temperature measurement section 6 Humidity measurement section 7 Display section 8 Transmission section 10 Image forming device 11 Charging device

Claims (5)

a charging member that contacts or faces the image carrier and charges the surface of the image carrier;
a high voltage generation circuit that applies an oscillating voltage in which a DC voltage and an AC voltage are superimposed to the charging member;
A control unit that controls a peak-to-peak voltage value Vpp of the AC voltage,
The control unit includes:
The peak-to-peak voltage value Vpp is used as a variable representing an assumed characteristic curve on two-dimensional coordinates representing the relationship between the peak-to-peak voltage value Vpp and the DC current value Idc between the charging member and the image carrier. Two different low-voltage side peak-to-peak voltage values Vpp(A) and Vpp(B), which are assumed to be on the lower voltage side than the voltage value at the inflection point that appears when the voltage is increased, and one which is assumed to be on the higher voltage side than the voltage value at the inflection point. table data in which a high voltage side peak-to-peak voltage value Vpp(C) is set in advance in association with a variation factor of the charging characteristics of the charging member;
obtaining the two low voltage side peak-to-peak voltage values Vpp(A), Vpp(B) and the high voltage side peak-to-peak voltage value Vpp(C) corresponding to the fluctuation factor from the table data;
Measured when the high voltage generation circuit applies the oscillating voltage on which the AC voltage indicating the two acquired low voltage side peak-to-peak voltage values Vpp(A) and Vpp(B) is superimposed to the charging member. A straight line L1 passing through coordinates A (Vpp (A), Idc (A)) and B (Vpp (B), Idc (B)) representing DC current values Idc (A) and Idc (B),
DC current value Idc(C) measured when the high voltage generation circuit applies the oscillating voltage on which the AC voltage indicating the acquired high voltage side peak-to-peak voltage value Vpp(C) is superimposed to the charging member. A straight line L2 passing through the coordinates C (Vpp(C), Idc(C)) representing the peak-to-peak voltage value Vpp and parallel to the coordinate axis representing the peak-to-peak voltage value Vpp;
a voltage control unit that sets the peak-to-peak voltage value Vpp corresponding to the intersection of the peak-to-peak voltage values Vpp(O);
The high-voltage side peak-to-peak voltage value Vpp(C) is set in the vicinity of the appropriate peak-to-peak voltage value Vpp(O) when the electrical resistance value of the charging member reaches an upper limit, and is set by the voltage control unit. A lifespan determining unit that determines that the charging member has reached the end of its lifespan when the appropriate peak-to-peak voltage value Vpp(O) becomes equal to or higher than the high-voltage side peak-to-peak voltage value Vpp(C). A charging device that a temperature measuring unit that measures the temperature around the charging device as the variation factor;
a humidity measuring unit that measures humidity around the charging device as the variation factor;
The voltage control unit controls the two low-voltage side peak-to-peak voltage values Vpp(A), Vpp(B) and the high-voltage side peak-to-peak voltage value Vpp(C) corresponding to the measured temperature and humidity. The charging device according to claim 1, wherein the charging device is acquired from table data. 3. The charging device according to claim 1, wherein the image carrier has an amorphous silicon film. A charging device according to any one of claims 1 to 3,
An image forming apparatus comprising: a display section that displays information representing a result of determination by the lifespan determination section. A charging device according to any one of claims 1 to 3,
An image forming apparatus comprising: a transmitting section that transmits information representing a determination result by the lifespan determining section.

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