Image forming apparatus

Abstract

In a two-component development method, this invention provides an image forming apparatus that can accurately predict toner charge amount in a simple and low-cost manner. [Solution] The image forming apparatus comprises an image forming unit, a developing voltage power supply, a current detection mechanism, and a control unit. The image forming unit includes an image carrier having a photosensitive layer formed on its surface, and a developer carrier positioned opposite the image carrier and carrying a two-component developer containing a magnetic carrier and toner, and a developing device that forms a toner image by attaching toner to an electrostatic latent image formed on the image carrier. The developing voltage power supply applies a developing voltage including at least a DC voltage to the developer carrier. The current detection mechanism detects the developing current flowing between the developer carrier and the image carrier when a developing voltage is applied to the developer carrier. The control unit estimates the amount of charge on the toner based on the white area current, which is the developing current flowing between the developer carrier and the non-image area of ​​the image carrier.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, and a multifunction machine thereof, and particularly to an image forming apparatus using a two-component development system that uses a two-component developer containing toner and carrier.

Background Art

[0002] In an image forming apparatus using an electrophotographic process, after the photosensitive layer on the surface of the photosensitive drum (image carrier) is charged to a predetermined surface potential (the same polarity as the charging polarity of the toner) by a charging device, an electrostatic latent image is formed on the photosensitive drum by an exposure device. Then, the formed electrostatic latent image is visualized with toner in a developing device, and after the toner image is transferred onto a recording medium that passes through a nip portion (transfer nip portion) between the photosensitive drum and a transfer member that contacts the photosensitive drum, a fixing process is generally performed.

[0003] In a two-component development system using a two-component developer containing toner and carrier, it is important to predict the charge amount of the toner in adjusting the image density. Conventionally, various techniques for predicting the charge amount have been proposed. For example, in Patent Document 1, a plurality of measurement toner images having different toner development amounts are formed on an image carrier, and based on the densities of the plurality of measurement toner images detected by a density detection unit, or in addition to the densities of the plurality of measurement toner images, based on the DC component of the development current measured by a development current measurement unit when the plurality of measurement toner images are formed, an image forming apparatus capable of executing a charge amount acquisition operation for acquiring the charge amount of the toner contained in the measurement toner image formed on the image carrier is disclosed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The method described in Patent Document 1 requires the formation of a measurement toner image in order to measure the developing current, which increases toner consumption for purposes other than printing. This has the problem of increasing the running costs of the image forming apparatus. Furthermore, a special measurement mode must be secured in order to accurately predict the amount of toner charge, which leads to a decrease in image forming efficiency (productivity).

[0006] In view of the above problems, the present invention aims to provide an image forming apparatus that can accurately predict the amount of toner charge in a simple and low-cost manner using a two-component development method. [Means for solving the problem]

[0007] To achieve the above objective, the first configuration of the present invention is an image forming apparatus comprising an image forming unit, a developing voltage power supply, a current detection mechanism, and a control unit. The image forming unit includes an image carrier having a photosensitive layer formed on its surface, and a developer carrier positioned opposite the image carrier and carrying a two-component developer including a magnetic carrier and toner, and a developing apparatus that forms a toner image by attaching toner to an electrostatic latent image formed on the image carrier. The developing voltage power supply applies a developing voltage including at least a DC voltage to the developer carrier. The current detection mechanism detects the developing current that flows between the developer carrier and the image carrier when a developing voltage is applied to the developer carrier. The control unit controls the image forming unit and the developing voltage power supply. The developing current includes an image current that flows between the developer carrier and the image portion of the image carrier, and a white area current that flows between the developer carrier and the non-image portion of the image carrier. The control unit estimates the amount of charge on the toner based on the white area current detected by the current detection mechanism. [Effects of the Invention]

[0008] According to the first configuration of the present invention, by estimating the amount of toner charge using the white area current, the image density can be properly maintained over a long period of time. Furthermore, since it is not necessary to estimate the amount of toner charge using an image density sensor, the amount of toner charge can be accurately estimated even in image forming apparatuses that are not equipped with an image density sensor. In addition, the amount of toner consumed for purposes other than printing can be reduced, and since the white area current can be measured during printing intervals, a decrease in image forming efficiency can also be suppressed. [Brief explanation of the drawing]

[0009] [Figure 1] Side cross-sectional view showing the internal configuration of an image forming apparatus 100 according to one embodiment of the present invention. [Figure 2] Enlarged view of the area around the image forming unit P, including the control path of the image forming apparatus 100. [Figure 3] A schematic diagram showing the current detection mechanism 50 connected to the photoreceptor drum 5 and the developing roller 30. [Figure 4] A graph showing the correlation between the current in the white area and the amount of toner charge. [Figure 5] A flowchart showing an example of toner charge amount estimation control in the image forming apparatus 100 of this embodiment. [Modes for carrying out the invention]

[0010] [1. Overall configuration of the image forming apparatus] Embodiments of the present invention will be described below with reference to the drawings. Figure 1 is a side cross-sectional view showing the internal structure of an image forming apparatus 100 according to one embodiment of the present invention. Inside the image forming apparatus (here, a monochrome printer) 100, there is an image forming unit P that forms a monochrome image by the processes of charging, exposure, development, and transfer. In the image forming unit P, a charging device 4, an exposure device (laser scanning unit, etc.) 7, a development device 8, a transfer roller 14, a cleaning device 19, and a static elimination device 6 are arranged along the rotation direction of the photoreceptor drum 5 (counterclockwise direction in Figure 1).

[0011] During the image formation process, the photoreceptor drum 5, which rotates counterclockwise as shown in Figure 1, is uniformly charged by the charging device 4. Next, an electrostatic latent image is formed on the photoreceptor drum 5 by a laser beam from the exposure device 7 based on the original image data. Then, toner is deposited onto the electrostatic latent image by the developing device 8 to form a toner image. The image data is transmitted from a personal computer (not shown), etc.

[0012] Toner is supplied to the developing unit 8 from the toner container 9. The toner concentration (T / C, the mass ratio of toner to magnetic carriers) in the developing unit 8 is detected by a toner concentration sensor 81 (see Figure 1). In addition, a static elimination device 6, which removes residual charge by irradiating the surface of the photoreceptor drum 5 with static elimination light, is provided downstream of the cleaning device 19 in the rotational direction of the photoreceptor drum 5.

[0013] As described above, paper (recording medium) is transported from the paper feed cassette 10 or manual feed device 11 via the paper transport path 12 and registration roller pair 13 toward the photoreceptor drum 5 on which the toner image has been formed. As the paper passes through the transfer roller 14 and the nip portion (transfer nip portion) of the photoreceptor drum 5, the toner image formed on the surface of the photoreceptor drum 5 is transferred to the paper. The paper on which the toner image has been transferred is separated from the photoreceptor drum 5 and transported to the fuser unit 15 where the toner image is fixed. The paper that has passed through the fuser unit 15 is transported to the top of the device via the paper transport path 16, and if an image is to be formed on only one side of the paper (single-sided printing), it is discharged to the discharge tray 18 by the discharge roller pair 17.

[0014] On the other hand, when forming an image on both sides of the paper (double-sided printing), the transport direction is reversed after the trailing edge of the paper passes through the branching section 20 of the paper transport path 16. As a result, the paper is diverted to the reversal transport path 21 that branches off from the branching section 20, and is re-transported to the registration roller pair 13 with the image surface reversed. The next toner image formed on the photoreceptor drum 5 is then transferred to the side of the paper where no image has been formed by the transfer roller 14. The paper with the transferred toner image is transported to the fuser unit 15, where the toner image is fixed, and then discharged to the discharge tray 18 by the discharge roller pair 17.

[0015] Figure 2 is a partially enlarged view of the area around the image forming unit P, including the control path of the image forming apparatus 100. The charging device 4 is positioned to contact the photoreceptor drum 5 and includes a charging roller 41 for charging the photoreceptor drum 5.

[0016] The charging roller 41 is formed by coating a core metal 41a with a conductive layer 41b and is positioned to contact the photoreceptor drum 5. The conductive layer 41b has ionic conductivity by incorporating an ionic conductive agent into crosslinked rubber. Epichlorohydrin rubber is used as the crosslinked rubber. Quaternary ammonium salts and borates are used as the ionic conductive agent.

[0017] The photoreceptor drum 5 is formed by creating a photosensitive layer, for example, an organic photosensitive layer (OPC) 5b, which is a positively charged photoconductor, on the surface of an aluminum drum tube (conductive substrate) 5a. The photoreceptor drum 5 is rotated at a constant speed around a pivot shaft by a drum drive unit (not shown).

[0018] As shown in Figure 2, when the photoreceptor drum 5 rotates counterclockwise, the charging roller 41, which is in contact with the surface of the photoreceptor drum 5, rotates clockwise in response. At this time, by applying a predetermined charging voltage to the charging roller 41, the surface of the photoreceptor drum 5 is uniformly charged.

[0019] The charging roller 41 is connected to a charging voltage power source 43 that generates a charging voltage with an AC voltage superimposed on a DC voltage. The charging voltage power source 43 includes an AC constant voltage power source and a DC constant voltage power source (both not shown). The AC constant voltage power source outputs a sinusoidal AC voltage generated from a low-voltage DC voltage modulated in a pulse shape using a boost transformer (not shown). The DC constant voltage power source outputs a DC voltage obtained by rectifying a sinusoidal AC voltage generated from a low-voltage DC voltage modulated in a pulse shape using a boost transformer.

[0020] The developing device 8 is disposed opposite to the photosensitive drum 5 and includes a developing roller 30 that carries a two-component developer (hereinafter also simply referred to as a developer) containing a magnetic carrier and toner. The developing roller 30 is connected to a developing voltage power source 44 that generates a developing voltage with an AC voltage superimposed on a DC voltage. The configuration of the developing voltage power source 44 is the same as that of the charging voltage power source 43. By applying a predetermined developing voltage to the developing roller 30, the toner in the developer carried on the developing roller 30 flies onto the surface of the photosensitive drum 5, and the electrostatic latent image is developed into a toner image. The current detection mechanism 50 detects the developing current flowing between the developing roller 41 and the photosensitive drum 5.

[0021] Next, the control system of the image forming apparatus 100 will be described with reference to FIG. 2. The image forming apparatus 100 is provided with a main control unit 80 composed of a CPU or the like. The main control unit 80 is connected to a storage unit 70 composed of a ROM, a RAM, or the like. The main control unit 80 controls each part of the image forming apparatus 100 (charging device 4, discharging device 6, exposure device 7, developing device 8, transfer roller 14, cleaning device 19, fixing device 15, charging voltage power source 43, developing voltage power source 44, voltage control unit 45, current detection mechanism 50, etc.) based on control programs and control data stored in the storage unit 70.

[0022] The voltage control unit 45 controls the charging voltage power source 43 that applies a vibration voltage to the charging roller 41 and the developing voltage power source 44 that applies a developing voltage to the developing roller 30. Note that the voltage control unit 45 may be composed of a control program stored in the storage unit 70.

[0023] The main control unit 80 is connected to a liquid crystal display unit 90 and a transceiver unit 91. The liquid crystal display unit 90 functions as a touch panel for the user to make various settings of the image forming apparatus 100, and also displays the status of the image forming apparatus 100, the image forming status, the number of printed sheets, etc. The transceiver unit 91 communicates with the outside world using a telephone line or an internet line.

[0024] The internal temperature and humidity sensor 92 detects the temperature and humidity inside the image forming apparatus 100, particularly around the developing apparatus 8. The detection results are transmitted to the main control unit 80.

[0025] [2. Configuration of the current detection mechanism] Figure 3 is a schematic diagram showing a current detection mechanism 50 connected to the photoreceptor drum 5 and the developing roller 30. The current detection mechanism 50 has a first connection part A, a second connection part B, and a current detection part C.

[0026] The first connection A and the second connection B are each connected in series to the developing voltage power supply 44. The first connection A and the second connection B are each connected to the ground point G. When the developing voltage power supply 44 applies a developing voltage to the developing roller 30, current flows through each of the first connection A and the second connection B.

[0027] The current detection unit C comprises a first current detection unit 50d and a second current detection unit 50e. The first current detection unit 50d detects the current flowing through the first connection A. The second current detection unit 50e detects the current flowing through the second connection B. The current detection unit C detects the value obtained by subtracting the value detected by the first current detection unit 50d from the value detected by the second current detection unit 50e as the development current flowing through the image area (hereinafter referred to as the image area current). The current detection unit C also detects the value detected by the first current detection unit 50d (or the value detected by the second current detection unit 50e) as the development current flowing through the non-image area (hereinafter referred to as the white area current). The image area current and white area current will be described later.

[0028] The first connection section A includes a first resistor 50g, a second resistor 50h, a capacitor 50i, and a third resistor 50j. The second resistor 50h, the capacitor 50i, the first current detection unit 50d, and the third resistor 50j are connected in series with respect to the developing voltage power supply 44 in the order of second resistor 50h, capacitor 50i, first current detection unit 50d, and third resistor 50j. The third resistor 50j is connected to the ground point G.

[0029] The first resistor 50g is connected in parallel with the capacitor 50i. The first resistor 50g is connected in series with the second resistor 50h, the first current detection unit 50d, and the third resistor 50j. The first resistor 50g is positioned between the second resistor 50h and the first current detection unit 50d.

[0030] The second connection section B has a developing area 50k and a fourth resistor 50m. The developing area 50k is the area located between the developing roller 30 and the photosensitive drum 5.

[0031] The developing region 50k, the second current detection unit 50e, and the fourth resistor 50m are connected in series with respect to the developing voltage power supply 44 in the order of developing region 50k, second current detection unit 50e, and fourth resistor 50m. The fourth resistor 50m is connected to the ground point G.

[0032] The developing voltage power supply 44 applies a developing voltage of the same polarity as the toner (positive in this case) to the developing roller 30, creating a potential difference between the developing roller 30 and the photoreceptor drum 5 (hereinafter also referred to as the DS-to-DS relationship). The charged toner moves between the developing roller 30 and the photoreceptor drum 5 via the developing area 50k, and the toner carried on the developing roller 30 is supplied to the photoreceptor drum 5. As a result, the electrostatic latent image formed on the surface of the photoreceptor drum 5 is developed into a toner image. In addition, the movement of the charged toner between the developing roller 30 and the photoreceptor drum 5 causes a current to flow in the developing area 50k.

[0033] As toner moves between the developing roller 30 and the photoreceptor drum 5, the developing area 50k is filled with developer, so the toner moves through the developer. Therefore, in addition to the capacitor component, there is also a resistive component due to the developer between the developing roller 30 and the photoreceptor drum 5. The capacitor component is the capacitance between the developing roller 30 and the photoreceptor drum 5.

[0034] The image current refers to the current generated by the movement of toner between the developing roller 30 and the photoreceptor drum 5 (hereinafter referred to as the DS-to-DS space). The image current is the current generated solely by the movement of toner between the DS-to-DS space, and is the current value when the current flowing between the DS-to-DS space is not affected by capacitive and resistive components. The image current is correlated with the amount of toner moving between the DS-to-DS space (moving toner), and has a value corresponding to the amount of moving toner. Specifically, the image current increases as the amount of moving toner increases.

[0035] The white area current refers to the current that flows between the Ds when the toner does not move between them. More specifically, when the non-image area (white area) of the photoreceptor drum 5 faces the developing roller 30, the developing area 50k is filled with carriers (magnetic brushes), forming a circuit in which the first connection part A and the second connection part B are connected in a ring. In this state, the current that flows as the toner moves through the magnetic brushes toward the developing roller 30 is the white area current (developing current of the non-image area), and the detected value of the first current detection unit 50d and the detected value of the second current detection unit 50e are equal.

[0036] In the current detection mechanism 50 shown in Figure 3, a capacitor 50i is arranged in parallel in the development region 50k between the developing roller 30 and the photoreceptor drum 5, and a first resistor 50g and a second resistor 50h are connected in parallel and series with the capacitor 50i, thereby enabling accurate detection of the image current and the white background current.

[0037] [3. Estimation of toner charge amount based on white area current] The following describes a feature of the present invention: a method for estimating the amount of toner charge based on the current in the white area.

[0038] Various methods have been proposed to estimate the toner charge amount Q / M. For example, one method estimates the toner charge amount based on the development current that flows when forming a reference image and the image density of the reference image detected by an image density sensor. However, since the image forming apparatus 100 of this embodiment is not equipped with an image density sensor, the method using an image density sensor cannot be adopted. Therefore, in this embodiment, the charge amount is estimated from the correlation between the white area current and the toner charge amount.

[0039] Figure 4 is a graph showing the correlation between the white area current and the toner charge. In Figure 4, the horizontal axis is the product of toner concentration T / C and toner charge Q / M (T / C*Q / M), and the vertical axis is the white area current I, plotting the white area current I as T / C*Q / M is varied. As shown in Figure 4, there is a positive correlation between the white area current and the toner charge.

[0040] The relationship shown in Figure 4 is determined experimentally beforehand and stored in the memory unit 70. Then, the toner charge amount Q / M is estimated based on the white area current detected by the current detection mechanism 50 and the correlation relationship (correlation formula) between the white area current and the toner charge amount stored in the memory unit 70.

[0041] Since developing the image is not required to detect the white area current, toner consumption other than printing can be reduced. Therefore, the running costs of the image forming apparatus 100 can be reduced. In addition, the white area current can be measured using time such as before and after the printing operation or during the printing interval (between sheets of paper). Therefore, there is no need to set up a special mode for measuring the white area current, and a decrease in image forming efficiency (productivity) can be suppressed.

[0042] Furthermore, it becomes possible to predict and adjust image density based on the estimated toner charge amount. Since the toner deposition amount is expressed as (Q / t) / (Q / M)=M / t, the toner deposition amount M / t can be calculated using the developing current I=Q / t that flows when an image is formed and the estimated toner charge amount Q / M, and the image density can be adjusted based on the calculated toner deposition amount M / t.

[0043] Since the amount of toner deposited M / t is proportional to the development voltage Vdc, the amount of toner deposited M / t can be adjusted to the target value by adjusting the development voltage Vdc based on the estimated value of the toner charge amount Q / M. Methods for adjusting the amount of toner deposited M / t include adjusting the development voltage (DC voltage) Vdc, adjusting the development voltage (AC voltage), adjusting the light intensity of the exposure device 7, and adjusting the charging voltage applied to the charging roller 41.

[0044] Alternatively, instead of using the relationship between toner deposition amount M / t and development voltage Vdc, the image density may be adjusted using the relationship between image density ID and development voltage Vdc. Furthermore, to correct the relationship between toner charge amount Q / M and actual development characteristics, durability-related parameters such as the toner density sensor 81, the in-machine temperature and humidity sensor 92, the cumulative print rate, and the operating time may be used.

[0045] Figure 5 is a flowchart showing an example of toner charge amount estimation control in the image forming apparatus 100 of this embodiment. The toner charge amount estimation procedure will be described in detail according to the steps in Figure 5, referring to Figures 1 to 4 as needed.

[0046] First, the main control unit 80 determines whether or not the timing for estimating the toner charge amount has been reached (step S1). Examples of the timing for estimating the toner charge amount include when the cumulative number of printed pages since the last estimation of the toner charge amount has reached a predetermined number, or when the power of the image forming apparatus 100 is turned on, or when it recovers from power-saving (sleep) mode.

[0047] If the timing for estimating the toner charge amount is reached (Yes in step S1), the current in the white area is measured using the current detection mechanism 50 (step S2). The current in the white area is measured by applying a developing voltage (DC voltage Vdc) to the photoreceptor drum 5 while it is charged to a predetermined surface potential V0 when not printing. When printing, it is measured between the sheets of paper. The measured current in the white area is transmitted to the main control unit 80.

[0048] Next, the main control unit 80 estimates the toner charge amount Q / M based on the measured white area current, the relationship between the white area current and T / C*Q / M stored in the storage unit 70 (see Figure 4), and the toner concentration T / C in the developing device 8 detected by the toner concentration sensor 81 (step S3).

[0049] The main control unit 80 determines whether or not adjustment of the image density is necessary based on the estimated value of the toner charge amount Q / M obtained in step S3 (step S4). If the estimated value of the toner charge amount Q / M deviates significantly from the target value and it is determined that adjustment of the image density is necessary (Yes in step S4), the development conditions are adjusted (step S5).

[0050] Specifically, the toner deposition amount M / t is calculated using the development current (image current) I=Q / t that flows when the image is formed and the estimated toner charge amount Q / M, and the image density is adjusted based on the calculated toner deposition amount M / t. On the other hand, if it is determined that no adjustment of the image density is necessary (No in step S4), the process is terminated without adjusting the image density.

[0051] As shown in Figure 5, by estimating the toner charge using the white area current, the image density can be properly maintained over a long period of time. Furthermore, since there is no need to estimate the toner charge using an image density sensor, the toner charge can be accurately estimated even in image forming apparatuses that are not equipped with an image density sensor.

[0052] Furthermore, by using the white area current to estimate the toner charge, the amount of toner consumed for purposes other than printing can be reduced. In addition, since the white area current can be measured at the printing interval (between sheets of paper), a decrease in image formation efficiency can be suppressed. Moreover, by incorporating the detection results of the toner density sensor 81 and the in-machine temperature and humidity sensor 92 into the estimation of the toner charge, in addition to the measurement results of the white area current, the accuracy of the toner charge estimation can be further improved.

[0053] Furthermore, by adjusting the image density based on an estimated toner charge amount, it becomes unnecessary to measure the image density using an image density sensor. Therefore, even image forming apparatuses that are not equipped with an image density sensor can accurately adjust the image density.

[0054] Furthermore, the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention. For example, the current detection mechanism 50 is not limited to the configuration of the embodiment shown in Figure 3, and other configurations can be used as long as they are capable of accurately measuring the developing current.

[0055] Furthermore, although the above embodiment describes the case using positively charged toner, the present invention can also be applied to the case using negatively charged toner. When negatively charged toner is used, the polarity of the developing side and the recovery side is reversed compared to when positively charged toner is used, with the developing side being negative and the recovery side being positive.

[0056] Furthermore, although the above embodiment described an image forming apparatus 100 using a monochrome printer as an example as shown in Figure 1, it is not limited to a monochrome printer and may be other image forming apparatuses such as monochrome and color copiers, digital multifunction printers, color printers, or facsimile machines.

[0057] In the case of color copiers and color printers, an image density sensor is required to detect the density of a reference image in order to perform calibration, which involves correcting image density and color misalignment. Therefore, by using the estimation of toner charge amount using the developing current in this embodiment, and the adjustment of image density based on the toner charge amount, as an aid to calibration, it becomes possible to shorten the time required for image density adjustment and to operate more efficiently. [Industrial applicability]

[0058] The present invention is applicable to an image forming apparatus equipped with a developing device that uses a two-component developing system that employs a two-component developer containing toner and a carrier. By utilizing the present invention, it is possible to provide an image forming apparatus that can accurately predict the amount of toner charge in a simple and low-cost manner in a two-component developing system. [Explanation of Symbols]

[0059] P Image forming section 4. Charging device 5. Photosensitive drum (image carrier) 6 Static eliminator 7. Exposure equipment 8. Developing device 14 Transfer Roller 30. Developing roller (developer carrier) 43. Charged voltage power supply 44 Developer voltage power supply 45 Voltage Control Unit 50 Current detection mechanism 70 Storage section 80 Main Control Unit (Control Unit) 81 Toner density sensor 92 In-flight temperature and humidity sensor 100 Image forming apparatus

Claims

1. An image carrier having a photosensitive layer formed on its surface, A developing apparatus having a developer carrier positioned opposite the image carrier and carrying a two-component developer including a magnetic carrier and toner, wherein the toner is attached to the electrostatic latent image formed on the image carrier to form a toner image, An image forming unit including, A developing voltage power supply that applies a developing voltage including at least a DC voltage to the developer carrier, A current detection mechanism for detecting the developing current that flows between the developer carrier and the image carrier when the developing voltage is applied to the developer carrier, The image forming unit and the control unit that controls the developing voltage power supply, In an image forming apparatus equipped with, The developing current includes an image current that flows between the developer carrier and the image portion of the image carrier, and a white area current that flows between the developer carrier and the non-image portion of the image carrier. The image forming apparatus is characterized in that the control unit estimates the amount of charge of the toner based on the white area current detected by the current detection mechanism.

2. The developing apparatus includes a toner concentration sensor that detects the ratio of the toner to the magnetic carrier, The image forming apparatus according to claim 1, characterized in that the control unit estimates the amount of charge of the toner based on the current of the white area and the output value of the toner density sensor.

3. The image forming apparatus according to claim 1, characterized in that the control unit adjusts the image density of the toner image based on the estimated amount of charge of the toner.

4. The image forming apparatus according to claim 3, characterized in that the control unit adjusts the image density of the toner image based on the estimated amount of charge of the toner and the image unit current detected by the current detection mechanism.

5. The image forming apparatus is equipped with a temperature and humidity sensor that detects the temperature and humidity inside or outside the apparatus. The image forming apparatus according to claim 4, characterized in that the control unit adjusts the image density of the toner image taking into account the detection result of the temperature and humidity sensor.

Images