JP2018066981A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that, even when the temperature of a charging roller and a result of detection performed by a temperature sensor do not match each other, can apply an appropriate peak-to-peak voltage to the charging roller.SOLUTION: An image forming apparatus comprises a test execution part that sequentially applies, to a charging roller, alternating voltages for a test with a plurality of different frequencies having a peak-to-peak voltage for a test in a period prior to an image forming period to detect respective alternating currents, and sets a predetermined peak-to-peak voltage during the image forming period on the basis of a specific frequency that is the maximum frequency at which the relationship between the frequencies and alternating currents maintains a linear shape.SELECTED DRAWING: Figure 2

Description

  The present invention is applied to an image forming apparatus having a function of forming an image on a recording medium such as a sheet, such as a copying machine, a printer, or a facsimile machine.

  The charging bias voltage applied to the charging roller is a DC voltage (Vdc) superimposed with an AC voltage having a peak-to-peak voltage (Vpp) that is twice or more the discharge start voltage when the DC voltage is applied.

  The surface scratches and scrapes caused by rubbing the surface of the photosensitive drum with the cleaning blade correlate with the amount of discharge current. Therefore, control (discharge current control) performed during non-image formation has been proposed in order to determine an alternating voltage (peak-to-peak voltage) at which a discharge current necessary for image formation can be obtained (Patent Document 1). On the other hand, as a resistance adjusting agent for the charging roller, an ionic conductive agent whose resistance value is relatively easy to adjust is often used, but the resistance value tends to be highly dependent on the environment (temperature, humidity).

In addition, when an ionic conductive agent is used as a resistance adjusting agent for the charging roller, charge transfer at room temperature is active, but charge transfer capability at a low temperature is extremely reduced.
Under such a low temperature environment, it has been found that conventional discharge current control may not be suitable as described below.

  7 and 8 show the relationship between the AC voltage and the discharge current in a normal temperature environment (22 ° C.) and a low temperature environment (15 ° C.). Here, the frequency of the AC voltage is 1.8 kHz.

  As shown in FIG. 8, in a low temperature environment, the discharge current does not necessarily increase monotonously with an increase in AC voltage, but may exhibit unstable characteristics such as once decreasing and increasing. The reason why the characteristics of the discharge current with respect to the AC voltage are not stable is not clear. However, the ion chain is affected by the mobility of the molecular chain in the material of the charging roller in a low temperature environment against the change in the electric field velocity in the charging roller. This is thought to be because the time required to develop conductivity becomes longer.

  Thus, when conventional discharge current control is used in a low temperature environment, the peak-to-peak voltage may not be determined as one. Therefore, the target discharge current is set in advance (for example, the target discharge current at normal temperature is 25 μA, but is 35 μA in a low temperature environment) to suppress the occurrence of image defects. However, since the discharge current is set high, the photosensitive drum and the charging roller may be deteriorated more than necessary.

  Conventionally, in order to prevent image unevenness at the charging frequency pitch from becoming conspicuous, an apparatus having a high process speed has been set to a high frequency.

  9 and 10 show AC voltage and discharge when the frequency of the AC voltage applied to the charging roller is low (1.8 kHz) and high (2.5 kHz) in a normal temperature and low humidity (22 ° C., 5%) environment. The relationship with current is shown. As shown in FIG. 10, when the frequency of the AC voltage is high, the discharge current may not stably increase with respect to the increase of the AC voltage even in a low temperature environment. This is presumably because, at a high frequency, the rate of change of the electric field in the charging roller is fast, so that the ion conductivity expression time does not sufficiently catch up even in a room temperature environment.

  Therefore, as shown in Table 1 or FIG. 4 below, a correspondence relationship between the temperature and the peak-to-peak voltage at which no image defect occurs is obtained in advance, and the correspondence relationship is stored in the memory of the apparatus body, and the detected temperature of the temperature sensor of the body The peak-to-peak voltage may be set accordingly.

  The reason why image defects can be suppressed by setting a higher peak-to-peak voltage even in a low-temperature environment is thought to be that the higher the maximum electric field, the higher the ion movement speed and the higher the conductivity.

JP-A-10-232534

However, the temperature sensor of the main body is usually installed at a location away from the charging roller.
In addition, when the drum cartridge containing the charging roller that was placed in the low temperature environment is installed in the main body of the device that has been placed in the normal temperature environment, or vice versa, the detected temperature of the temperature sensor and the actual charging roller temperature Is different.

  For this reason, the peak-to-peak voltage set based on the high voltage table A (Table 1) may be too low or too high, and there is a possibility that the charging failure or the life of the photosensitive member or the like may be reduced.

  An object of the present invention is to provide an image forming apparatus capable of setting an appropriate AC voltage even when the temperature detected by the temperature sensor of the main body does not match the temperature of the charging roller.

  In order to achieve the above object, the image forming apparatus of the present invention comprises an image carrier, a charging roller that contacts the image carrier and charges the image carrier, and after exposing the charged image carrier, A toner image forming unit that forms a toner image on the image carrier by attaching toner; a power source that outputs a voltage in which a DC voltage is superimposed on an AC voltage; and an AC current that flows between the power source and the charging roller A detection member for detecting the voltage, and applying a voltage having a predetermined frequency and a predetermined peak-to-peak voltage from the power source to the charging roller during the image formation period to charge the image carrier, and the toner image forming unit A controller configured to form a toner image on an image carrier, and a plurality of test alternating voltages having different test peak voltages applied sequentially to the charging roller in a period preceding the image forming period to detect the detection; With parts A test execution unit that executes a test mode for detecting each of the alternating currents, and the test execution unit maintains a linear relationship between the frequency and the alternating current obtained in the test mode. The predetermined peak-to-peak voltage is set based on a specific frequency that is the maximum frequency to be transmitted.

  According to the present invention, it is possible to provide an image forming apparatus capable of setting an appropriate AC voltage even when the temperature detected by the temperature sensor of the main body does not match the temperature of the charging roller.

1 is a longitudinal sectional view showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention. Flowchart of an embodiment of the present invention The figure which shows the relationship between the frequency and alternating current in embodiment of this invention Diagram showing the relationship between temperature and peak-to-peak voltage in conventional control The figure which shows the relationship between the specific frequency and peak-to-peak voltage in the test mode which concerns on embodiment of this invention. High-pressure block diagram according to an embodiment of the present invention Diagram showing the relationship between peak-to-peak voltage and discharge current in a room temperature environment Diagram showing the relationship between peak-to-peak voltage and discharge current in a low-temperature environment The figure which shows the relationship between the peak-to-peak voltage and discharge current amount on condition of frequency 1.8kHz The figure which shows the relationship between the peak-to-peak voltage and discharge current amount on condition of frequency 2.5kHz.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

<< First Embodiment >>
(Image forming device)
FIG. 1 is a longitudinal sectional view showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus shown in FIG. 1 is a four-color full color in which four image forming units are arranged in tandem along the moving direction of an endless belt type intermediate transfer material (hereinafter referred to as an intermediate transfer belt) that is a toner support material. This is an image forming apparatus.

  The image output unit 1P is roughly divided into an image forming unit 10 (four stations a, b, c, and d are arranged in parallel, and the configuration is the same), a paper feeding unit 20, an intermediate transfer unit 30, a fixing unit. It consists of a unit 40 and a control unit (not shown). Further, each unit will be described in detail.

  Photosensitive drums 11a, 11b, 11c, and 11d as image carriers are pivotally supported at their centers and are driven to rotate in the direction of the arrow. The primary charging rollers (charging rollers) 12a, 12b, 12c, 12d, the laser scanner units 13a, 13b, 13c, 13d, the developing devices 14a, 14b, 14c in the rotational direction facing the outer peripheral surfaces of the photosensitive drums 11a to 11d, 14d is arranged.

  In the image forming process, the control unit applies a charging voltage from the power source to the charging rollers 12a to 12d to give a uniform charge amount of charge to the surfaces of the photosensitive drums 11a to 11d. Next, the control unit performs formation of an electrostatic latent image and toner image by toner adhesion in the toner image forming unit. The laser scanner units 13a to 13d expose the photosensitive drums 11a to 11d with light beams such as a laser beam modulated according to the recording image signal, thereby forming electrostatic latent images thereon. Details of the operation of the laser scanner unit will be described later.

  Further, each of the developing devices 14a to 14d containing developer of four colors such as yellow, cyan, magenta and black (hereinafter referred to as toner) is attached to the electrostatic latent image to be visualized as a toner image. . On the downstream side of the image transfer areas Ta, Tb, Tc, and Td where the visualized toner image is transferred to the intermediate transfer member, the toner images are not transferred onto the photosensitive drums 11a to 11d by the cleaning devices 15a, 15b, 15c, and 15d. The drum surface is scraped off to clean the drum surface.

  By the process described above, image formation with each toner is sequentially performed. As the photosensitive drums 11a to 11d, negative OPC photosensitive drums were used. Specifically, a negative organic layer in which a azo pigment is used as a photoreceptor layer as a CGL layer (carrier generation layer), and a mixture of hydrazone and resin is laminated thereon as a CTL layer (carrier transport layer) to a thickness of 29 μm. A semiconductor layer (OPC layer) was used.

  Next, the cleaning devices 15a, 15b, 15c, and 15d will be described. As a cleaning device, a counter blade method is used, and the free length of the cleaning blade is 8 mm. The cleaning blade is an elastic blade mainly composed of urethane, and is brought into contact with the photosensitive drum with a pressure of about 35 g / cm.

  The paper supply unit 20 includes cassettes 21 a and 21 b for storing the recording material P and a manual feed tray 27. Further, pickup rollers 22a, 22b and 26 for feeding the recording material P one by one from the cassette or the manual feed tray, a pair of paper feed rollers 23 for transporting the recording material P sent from each pickup roller to the registration rollers, and A paper feed guide 24 is provided. In addition, registration rollers 25a and 25b for feeding the recording material P to the secondary transfer region Te in accordance with the image formation timing of the image forming unit are provided.

  Next, the intermediate transfer unit 30 will be described in detail. As the material of the intermediate transfer belt 31, for example, PET [polyethylene terephthalate] or PVdF [polyvinylidene fluoride] is used. The intermediate transfer belt 31 includes a driving roller 32 that transmits driving force to the intermediate transfer belt 31, a tension roller 33 that applies appropriate tension to the intermediate transfer belt 31 by urging of a spring (not shown), and a secondary transfer region across the belt. It is wound around a driven roller 34 facing Te.

  Among these, a primary transfer plane A is formed between the drive roller 32 and the tension roller 33. The drive roller 32 is coated with rubber (urethane or chloroprene) having a thickness of several millimeters on the surface of the metal roller to prevent slippage with the belt. The drive roller 32 is rotationally driven by a pulse motor (not shown).

  Primary transfer rollers 35 a to 35 d are arranged behind the intermediate transfer belt 31 in primary transfer regions Ta to Td where the photosensitive drums 11 a to 11 d and the intermediate transfer belt 31 face each other. A secondary transfer roller 36 is disposed opposite to the driven roller 34, and a secondary transfer region Te is formed by a nip (nip portion) with the intermediate transfer belt 31.

  The secondary transfer roller 36 is pressed against the intermediate transfer member with an appropriate pressure. A brush roller (not shown) for cleaning the image forming surface of the intermediate transfer belt 31 and a waste toner box (not shown) for storing waste toner are disposed on the intermediate transfer belt and downstream of the secondary transfer region Te. Is provided. Further, a cleaning device 100 for cleaning the secondary transfer residual toner is provided on the intermediate transfer belt.

  The fixing unit 40 includes a fixing roller 41a having a heat source such as a halogen heater therein, and 41b that forms a fixing nip portion together with the fixing roller 41a and is pressed against the fixing roller 41a (this roller may also include a heat source. ). Further, a guide 43 for guiding the transfer material P to the fixing nip portion is provided. Further, an internal paper discharge roller 44 and an external paper discharge roller 45 for guiding the transfer material P to the outside of the apparatus are further provided.

  The control unit includes a control board and a motor drive board (not shown) for controlling the operation of the mechanism in each unit. An environmental sensor (for example, a temperature sensor (temperature detection member), temperature / humidity sensor) 50 can accurately measure the environmental temperature and humidity around the apparatus without being affected by the fixing unit 40 serving as a heat source in the apparatus. It is arranged at the position shown.

  The environmental sensor 50 is difficult to install near the charging roller, and is usually installed at a location far away from the charging roller. In other words, placing them around consumable parts that are frequently replaced, such as drum cartridges (photosensitive drums and process means), increases the risk of contamination and disconnection, and increases the risk of damage and false detection. It is often installed aiming at a place where there is little in / out.

  Various controls are performed based on the output of the environmental sensor 50. As a characteristic of the color toner, a weight average particle size of 5 to 8 μm is preferable for forming a good image.

(Charging device)
Next, the configuration of the charging device including the contact-type charging roller 12 according to the embodiment of the present invention will be described. The roller surface layer of the charging roller 12 is made of a conductive rubber having a thickness of 1 to 2 mm in which a conductive agent such as carbon black is dispersed and mixed, and its resistance value is 10 ⁵ to prevent charging unevenness during image formation. Prepare to 10 ⁷ Ω · cm.

Alternatively, an ABS resin containing an ion conductive polymer compound such as polyether ester amide and having a resistance value of 10 ⁵ to 10 ⁷ Ω · cm is formed on the surface of the conductive support by injection molding. A resistance adjustment layer is formed by covering 1 mm. Then, a protective layer made of a thermoplastic resin composition in which conductive fine particles such as tin oxide are dispersed is sequentially formed on the surface of the resistance adjustment layer.

A metal shaft member is used as a conductive support for applying a charging voltage. This shaft member is integrally composed of a bearing portion, a voltage application bearing portion, and a covering portion having an outer diameter of φ14 mm. On the peripheral surface of the covering portion, a resistance adjustment layer having a volume resistance value of 10 ⁵ to 10 ⁷ Ω · cm of ABS resin, which is a thermoplastic resin containing an ion conductive polymer compound such as polyether ester amide. Is injection-molded with a thickness of 0.5 to 1 mm by injection molding.

(cartridge)
The charging roller 12a, the photosensitive drum 1a, and the photosensitive member cleaning unit 15a exist as an integral cartridge. By replacing the cartridge, the charging roller 12a, the photosensitive drum 1a, and the photosensitive member cleaning unit 15a can be replaced at once as consumables. There are various types of cartridges, ranging from those exchanged by service personnel to those that can be exchanged by the user, but the cartridges used in this embodiment have a mechanism that the user can exchange. The exchange procedure is a mechanism displayed on a display installed in the main body.

  The photoconductive drum 1a is an organic photoconductor that is laminated on a support in the order of an undercoat layer, a charge generation layer, and a charge transport layer. The support can be used without particular limitation as long as it has conductivity and does not affect the measurement of hardness. For example, a material obtained by molding a metal or alloy such as aluminum, copper, chromium, nickel, zinc and stainless steel into a drum shape can be used.

  Undercoat layer improves adhesion of photosensitive layer, improves coatability, protects support, covers defective areas on support, improves charge injection from support, protects against electrical breakdown of photosensitive layer, etc. Formed for. As the material for the undercoat layer, polyvinyl alcohol, poly-N-vinylimidazole, polyethylene oxide, ethyl cellulose, ethylene-acrylic acid copolymer, casein, polyamide, N-methoxymethylated 6 nylon can be used. Alternatively, copolymer nylon, glue and gelatin can be used.

  These are dissolved in a suitable solvent and coated on a support. At that time, the thickness of the undercoat layer is preferably 0.1 to 2 μm. Next, a photosensitive layer is formed on the undercoat layer. In the case of forming a laminated type photosensitive layer in which the charge generation layer and the charge transport layer are functionally separated, the charge generation layer and the charge transport layer are laminated in this order on the undercoat layer.

  Here, examples of the charge generation material used for the charge generation layer include selenium-tellurium, pyrylium, thiapyrylium dyes, and various central metals and crystal systems. More specifically, for example, phthalocyanine compounds having crystal types such as α, β, γ, ε, and X type, anthanthrone pigments, dibenzpyrenequinone pigments, pyranthrone pigments, trisazo pigments, disazo pigments, monoazo pigments can be mentioned. . Alternatively, indigo pigments, quinacridone pigments, asymmetric quinocyanine pigments, quinocyanines, and amorphous silicones described in JP-A No. 54-143645 can be used.

  In the present embodiment, a charge generation layer using a phthalocyanine compound capable of increasing sensitivity in order to realize high image quality is used.

(Block circuit)
Next, a block circuit of a charging bias application system for the charging roller 12 (12a) of the present embodiment will be described with reference to FIG. An oscillating voltage (bias voltage Vdc + Vac) obtained by superimposing an AC voltage of frequency f on a DC voltage from the power source S1 is applied to the charging roller 12a through a cored bar, so that the peripheral surface of the rotating photosensitive drum 1 has a predetermined potential. Charged. The power source S <b> 1 includes a direct current (DC) power source 101 and an alternating current (AC) power source 102.

  Reference numeral 103 denotes a control circuit (control unit, CPU), which controls on / off of the DC power supply 101 and the AC power supply 102 of the power supply S1, and applies either a DC voltage or an AC voltage or a superimposed voltage of both to the charging roller 2. It has a function to control to apply. Further, it has a function of controlling the DC voltage value applied from the DC power source 101 to the charging roller 12a and the peak-to-peak voltage value of the AC voltage applied from the AC power source 102 to the charging roller 12a. Reference numeral 104 denotes an alternating current measuring circuit as a member (detecting member) for detecting the effective value of the alternating current flowing through the charging roller 12 a via the photosensitive member 1. The AC current value measured from the circuit 104 is input to the control circuit 103.

(Test mode)
Hereinafter, the test mode in this embodiment will be described. In the present embodiment, the test mode is executed in a period preceding the image forming period. In the test mode, the test execution unit sequentially applies a plurality of test AC voltages having different test peak voltages to the charging roller, and detects each AC current with the detection member. The test execution unit sets a predetermined peak-to-peak voltage based on the specific frequency that is the maximum frequency at which the relationship between the frequency obtained in the test mode and the alternating current maintains linearity. First, the flowchart of FIG. 2 will be described.

  The charging frequency at the time of image formation in this embodiment is 1.8 kHz. The frequency range of the alternating current applied in the test mode is determined in advance from the range of the resistance value of the charging roller including the environment and durability. The test mode is performed at a timing other than the time of image formation. At (101) shown in FIG. 2, the main body is turned on or the door is opened / closed (drum opening / closing), and the photosensitive drum is driven at (102). Next, at (103), the test peak-to-peak voltage is fixed at 600 V, and the frequency is gradually changed from a low frequency to a high frequency. At (104), an alternating current is detected. In order to change the frequency, the frequency may be once changed from a low frequency to a high frequency and then set to a low frequency again.

  Next, (105) the test execution unit determines a specific frequency that is the maximum frequency at which the relationship between the frequency obtained in the test mode and the alternating current maintains linearity. The linear relationship between the frequency and the alternating current is maintained in the frequency range up to the specific frequency, and when the frequency exceeds the specific frequency, the difference between the linear relationship and the alternating current increases as the frequency increases. The test execution unit sets the maximum frequency at which the difference between the linear relationship and the alternating current is less than a predetermined value as the specific frequency. As the predetermined value, for example, the difference between the intersection of the virtual straight line at an arbitrary frequency and the alternating current with respect to the virtual straight line obtained by extending the linear relationship obtained in the low frequency range is 1 from the virtual straight line. The value can be about 3%. A fixed value may be used as the predetermined value.

  An example of the relationship between the frequency and the alternating current in the 15 ° C. environment and the 23 ° C. environment obtained in the test mode is shown in FIG. When the frequency exceeds a specific frequency that is the maximum frequency in the frequency range in which the linear relationship is maintained, the responsiveness of the charge in the charging roller with respect to the frequency decreases. According to FIG. 3, it can be seen that there is a specific frequency near a frequency of 0.8 kHz in a 23 ° C. environment and a frequency of about 1.7 kHz in a 15 ° C. environment. In general, when the charging roller has high conductivity, the specific frequency tends to be low, and when the conductivity is low, the specific frequency tends to be high.

  Next, in FIG. 2 (106), the control circuit which is the test execution unit in accordance with the relationship between the peak-to-peak voltage correspondence table B (Table 2) or the relationship shown in FIG. 5 stored in advance in the storage unit of the main body. 103 sets a predetermined peak-to-peak voltage applied during image formation. In the AC voltage table B (Table 2), a peak-to-peak voltage is set so that charging failure does not occur under the condition of a charging frequency of 1.8 kHz during image formation. Next, image formation is started at (107).

  The predetermined peak-to-peak voltage at the time of image formation is set to 1755 V in the 23 ° C. environment and 1853 V in the 15 ° C. environment from the high voltage table B (Table 2) or FIG. A good image is obtained.

  In the present embodiment, an appropriate peak-to-peak voltage can be set even when the temperature indicated by the temperature sensor is different from the temperature of the charging roller. Thereby, the lifetime reduction of the photosensitive drum or the charging roller can be suppressed, and an image free from charging failure can be provided.

  Further, when using a charging roller containing an ionic conductive agent, the control unit can determine that the temperature of the charging roller is different from the temperature detected by the main body. When the control unit determines that the temperature of the charging roller is different from the temperature detected by the main body, the charging condition described above can be set to suppress the occurrence of low-temperature fogging and sandy soil that occurs in a low-temperature environment. is there.

(Modification)
In the above-described embodiment, the preferred embodiment of the present invention has been described. However, the present invention is not limited to this, and various modifications can be made within the scope of the present invention.

(Modification 1)
In the above-described embodiment, the predetermined peak-to-peak voltage applied to the charging unit at the time of image formation is set based on the specific frequency obtained from the relationship between the frequency and the alternating current and a table created in advance. Such modifications are included.

  For example, the peak-to-peak voltage set in the above-described embodiment and the peak-to-peak voltage referring to the table in Table 1 based on the detected temperature of the main body are respectively weighted and set using the charging conditions of both. You can also. Specifically, the peak-to-peak voltage set in the above-described embodiment is multiplied by 0.9 as a weighting coefficient, the peak-to-peak voltage based on the detected temperature of the main body is multiplied by 0.1 as a weighting coefficient, It can also be a peak-to-peak voltage during image formation.

(Modification 2)
In the embodiment described above, a DC voltage may be superimposed on the AC voltage applied in the test mode.

  In the test mode, an AC voltage is applied to the charging roller for a time during which the charging roller rotates at least once for one frequency.

  In the test mode, an AC voltage may be applied to the charging roller for a time during which the photosensitive drum as a rotating body rotates at least once for one frequency.

(Modification 3)
In the above-described embodiment, the case where the charging roller includes an ionic conductive agent has been described. However, the present invention is not limited to this and can be applied to various charging rollers.

(Modification 4)
In the embodiment described above, the test peak-to-peak voltage is fixed at 600 V, and the alternating current is detected while sequentially changing the frequency. The test peak-to-peak voltage may be a voltage lower than the start of discharge or a voltage higher than the start of discharge, but a voltage lower than the start of discharge is preferable for the purpose of suppressing deterioration of the photoreceptor and the charging roller.

11 .... Photosensitive drum, 12 .... Charging roller, 103 ... Control circuit (CPU), 104 ... AC current measuring circuit, S1 ... Power supply

Claims (10)

An image carrier;
A charging roller that contacts the image carrier and charges the image carrier;
A toner image forming unit for exposing the charged image carrier and then attaching a toner to form a toner image on the image carrier;
A power supply that outputs a voltage in which a DC voltage is superimposed on an AC voltage;
A detection member for detecting an alternating current flowing between the power source and the charging roller;
During the image formation period, a voltage having a predetermined frequency and a predetermined peak-to-peak voltage is applied from the power source to the charging roller to charge the image carrier, and a toner image is formed on the image carrier by the toner image forming unit. A control unit to be formed;
In a period preceding the image forming period, a test mode in which a plurality of test AC voltages having different test peak voltages are sequentially applied to the charging roller and the AC current is detected by the detection member. A test execution unit to be executed,
The test execution unit sets the predetermined peak-to-peak voltage based on a specific frequency that is a maximum frequency at which the relationship between the frequency obtained in the test mode and the alternating current maintains linearity. Image forming apparatus.   When the relationship between the frequency and the alternating current increases as the frequency increases, the maximum frequency at which the difference becomes less than a predetermined value is set as the specific frequency when the difference between the linear relationship and the alternating current increases. The image forming apparatus according to claim 1, wherein:   A storage unit in which a correspondence relationship between the value of the specific frequency and the value of the predetermined peak-to-peak voltage is stored in advance; and the test execution unit is configured to perform the predetermined peak-to-peak relationship based on the correspondence relationship of the storage unit. The image forming apparatus according to claim 1, wherein a voltage is set.   3. The image forming apparatus according to claim 1, wherein when the plurality of different frequencies are sequentially applied, the test execution unit applies the frequencies in ascending order. 4.   3. The image forming apparatus according to claim 1, wherein when the plurality of different frequencies are sequentially applied, the test execution unit temporarily applies a high frequency from a low frequency and then applies a low frequency again.   The image forming apparatus according to claim 1, wherein the charging roller includes an ionic conductive agent.   The image forming apparatus according to claim 1, wherein the test peak-to-peak voltage is a value at which no discharge occurs between the image carrier and the charging roller.   8. The image according to claim 1, wherein the test execution unit applies each of the test AC voltages to the charging roller for a time during which the charging roller rotates at least once. Forming equipment.   The image bearing member is a rotating member, and the test execution unit applies each of the test AC voltages to the charging roller for a time during which the rotating member rotates at least once. The image forming apparatus according to any one of the above.   The image forming apparatus according to claim 1, further comprising a temperature detection member that detects a temperature of the apparatus main body.