Image forming apparatus

Abstract

To provide an image forming apparatus that can ensure the accuracy of paper resistance characteristics.SOLUTION: An image forming apparatus 1A comprises: a pair of rollers 40a, 40b that apply voltage to a sheet; a current detection unit 32 that detects current flowing between the pair of rollers 40a, 40b and the sheet; a leakage detection unit 33 that detects the presence or absence of leakage; and a control unit 2 that applies a plurality of different voltages to the sheet, when the leakage detection unit 33 does not detect the occurrence of leakage, measures a value corresponding to sheet resistance, and when the leakage detection unit 33 detects the occurrence of leakage, changes a voltage application portion with respect to the sheet, applies voltage equal to or less than the voltage to be applied at the occurrence of leakage, and measures the value corresponding to the sheet resistance.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus that transfers (secondary transfers) a toner image transferred onto an intermediate transfer member onto a sheet of paper and thermally fixes the image to form the image. [Background technology]

[0002] There is a known image forming apparatus that transfers a toner image transferred onto an intermediate transfer member onto a sheet of paper (secondary transfer) and thermally fixes the image. In such an electrophotographic image forming apparatus, it is necessary to obtain the resistance value of the sheet of paper in order to determine the optimal secondary transfer conditions.

[0003] 2. Description of the Related Art Conventionally, a technique is known in which a sheet of paper is sandwiched between a pair of rollers that constitute electrodes, and a voltage is applied between the pair of rollers to calculate the resistance value of the sheet of paper (see, for example, Patent Document 1).

[0004] However, it is known that the resistance value of paper changes logarithmically with respect to the value of the applied high voltage, that is, the resistance value of paper is known to range over a wide range (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 5-323715 [Patent Document 2] JP 2006-215383 A Summary of the Invention [Problem to be solved by the invention]

[0006] To derive a highly accurate estimation formula for paper resistance characteristics from the paper resistance value, it is necessary to measure current at multiple voltages with the required resolution. Because the resistance value of paper varies by about 10^3 depending on the environment, it is necessary to measure it over a wide voltage range. For this reason, to accurately measure paper resistance characteristics, it is necessary to set the applied voltage in small increments.

[0007] However, increasing the applied voltage may cause a discharge (leak) due to dielectric breakdown in a part of the paper. The voltage at which leakage occurs varies depending on the environment such as humidity, the type of paper, etc. As the voltage at which leakage occurs is unknown, the change in the applied voltage is made small, and the applied voltage is gradually increased from a small voltage. However, this means that it takes a long time to measure the paper resistance characteristics once.

[0008] On the other hand, if the change amount of the applied voltage is set to be large, leakage may occur before the applied voltage is increased to the voltage assumed for obtaining the paper resistance characteristics. In this case, it may not be possible to measure the current at multiple voltages with the resolution required to derive an estimation formula for the paper resistance characteristics with high accuracy. In addition, if leakage occurs continuously in the same place on the paper, there is a possibility that the paper may be burned.

[0009] The present invention has been made to solve the above problems, and has an object to provide an image forming apparatus that can ensure the accuracy of the paper resistance characteristics used to determine the secondary transfer conditions. [Means for solving the problem]

[0010] In order to solve the above-mentioned problems, the present invention provides an image forming apparatus that includes a voltage application member that applies a voltage to paper, a current detection unit that detects the current flowing between the voltage application member and the paper, a discharge detection unit that detects the presence or absence of a discharge occurring between the voltage application member and the paper, and a control unit that applies a plurality of different voltages to the paper, and if the discharge detection unit does not detect the occurrence of a discharge, measures a value corresponding to the paper resistance, and if the discharge detection unit detects the occurrence of a discharge, changes the voltage application location on the paper, applies a voltage lower than the applied voltage when the discharge occurred, and measures the value corresponding to the paper resistance. Effect of the Invention

[0011] In the present invention, even if the change amount of the applied voltage is set to a large amount, current measurement can be performed using multiple voltages with the resolution required to derive an accurate estimation equation for the paper resistance characteristics. This ensures the accuracy of the paper resistance characteristics. In addition, the time required for one paper resistance characteristic measurement is prevented from increasing, improving productivity. Furthermore, it is possible to prevent continuous leaks from occurring at the same location on the paper. [Brief description of the drawings]

[0012] [Figure 1] 1 is a functional block diagram illustrating an example of an image forming apparatus according to an embodiment of the present invention. [Figure 2A] 1 is a diagram showing a main configuration of an example of an image forming apparatus according to an embodiment of the present invention; [Figure 2B] 1 is a diagram showing a main configuration of an example of an image forming apparatus according to an embodiment of the present invention; [Diagram 3] 10 is a flowchart showing an example of an operation for acquiring the voltage-resistance characteristics of a sheet. [Figure 4] 11 is a graph showing an example of voltage-current characteristics when no paper is present between a pair of rollers. [Diagram 5] 5 is an explanatory diagram showing the transition of a voltage applied between a pair of rollers. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image forming apparatus according to the present invention will now be described with reference to the accompanying drawings.

[0014] <Configuration Example of Image Forming Apparatus of the Present Embodiment> FIG. 1 is a functional block diagram showing an example of an image forming apparatus according to the present embodiment, and FIGS. 2A and 2B are diagrams showing the main configuration of an example of an image forming apparatus according to the present embodiment.

[0015] The image forming apparatus 1 A includes a control unit 2 , a voltage application / detection unit 3 , and a measurement unit 4 .

[0016] The measurement unit 4 includes a pair of rollers 40a and 40b, a motor 41, and an encoder .

[0017] The rollers 40a and 40b are an example of a voltage application member and a transport member, and are made of conductive resin. The rollers 40a and 40b are rotatably supported by a support portion (not shown). The rollers 40a and 40b face each other across the transport path of the paper P. FIG. 2A shows a state in which the paper P is sandwiched between the rollers 40a and 40b. In this state, the outer circumferential surfaces of the rollers 40a and 40b are in contact with the paper P. This allows electricity to flow between the rollers 40a and 40b via the paper P. In addition, the paper P can be transported by rotating the rollers 40a and 40b.

[0018] 2B shows a state where no paper P is sandwiched between rollers 40a and 40b. In this state, the outer circumferential surfaces of rollers 40a and 40b are in contact with each other. This allows electricity to flow between rollers 40a and 40b.

[0019] The motor 41 rotates the rollers 40a and 40b. The roller 40a may be rotated by the driving force of the motor 41, and the roller 40b may be rotated by being driven by the conveyance of the paper P.

[0020] The encoder 42 detects the amount of rotation of the rollers 40 a and 40 b or the amount of rotation of the motor 41 .

[0021] The voltage application / detection unit 3 includes a high voltage application unit 30 and a detection unit 31. The high voltage application unit 30 applies a predetermined voltage between the rollers 40a and 40b, and passes a high voltage current between the rollers 40a and 40b.

[0022] The detection unit 31 includes a current detection unit 32, a leak detection unit 33, and a voltage detection unit 34. The current detection unit 32 detects the value of the current flowing between rollers 40a and 40. The leak detection unit 33 is an example of a discharge detection unit, and detects discharge (leak) that occurs between rollers 40a and 40b that sandwich paper P. The voltage detection unit 34 detects the value of the voltage applied between rollers 40a and 40.

[0023] The control unit 2 includes a CPU 20, an A / D conversion unit 21, and a motor driver 22. The A / D conversion unit 21 converts the value of the current detected by the current detection unit 32 from an analog signal to a digital signal, and inputs the signal to the CPU 20. The A / D conversion unit 21 also converts the value of the voltage detected by the voltage detection unit 34 from an analog signal to a digital signal, and inputs the signal to the CPU 20.

[0024] The CPU 20 calculates the resistance of the paper P from the value of the current flowing between the roller 40a and the roller 40b.

[0025] Furthermore, the CPU 20 sets the value of the voltage to be applied to the paper P by the high voltage application unit 30 based on the presence or absence of detection of leakage occurring between the rollers 40a and 40b sandwiching the paper P therebetween.

[0026] Furthermore, based on the presence or absence of detection of a leak, the CPU 20 controls the conveyance of the paper P. When a leak is detected, the CPU 20 drives the motor 41 via the motor driver 22 to convey the paper P by a predetermined amount.

[0027] <Example of Operation of Image Forming Apparatus of the Present Embodiment> 3 is a flow chart showing an example of an operation for acquiring the voltage-resistance characteristic of a sheet of paper. First, the overall flow of the operation for acquiring the voltage-resistance characteristic of a sheet of paper P will be described.

[0028] 2A shows a measurement system in a state where a sheet of paper P is sandwiched between rollers 40a and 40b. CPU 20 sets a voltage Vn to be applied between the pair of rollers 40a and 40b sandwiching sheet of paper P (step SA1).

[0029] The CPU 20 applies a voltage Vn between the pair of rollers 40a, 40b sandwiching the paper P by the high voltage application unit 30 (step SA2). After applying the voltage Vn between the pair of rollers 40a, 40b sandwiching the paper P, the CPU 20 determines whether or not a leak has been detected by the leak detection unit 33 (step SA3). If no leak has been detected, the CPU 20 obtains the current An flowing between the pair of rollers 40a, 40b sandwiching the paper P from the current detection unit 32 (step SA4).

[0030] Furthermore, if no leak is detected, the CPU 20 acquires the resistance Rn of the paper P (step SA5). A method for determining the resistance Rn of the paper P from the voltage Vn applied between the pair of rollers 40a, 40b and the current An flowing between the rollers will be described in detail later.

[0031] The CPU 20 determines whether the resistance Rn of the paper P has been measured a predetermined number of times with different voltages applied (step SA6). If the resistance of the paper P has been measured a predetermined number of times, the CPU 20 acquires the voltage-resistance characteristics of the paper P (step SA7). If the resistance of the paper P has not been measured a predetermined number of times, the CPU 20 stops applying the voltage (step SA8). Then, the CPU 20 sets the voltage to be applied next in step SA1.

[0032] When the CPU 20 starts acquiring the voltage-resistance characteristics of the paper P, the voltage Vn applied between the pair of rollers 40a and 40b that hold the paper P is set to a predetermined minimum voltage V min If no leak is detected, the CPU 20 sets the minimum voltage V min to maximum voltage V max Therefore, when a leak is not detected, the CPU 20 increases the voltage in a stepwise manner until a voltage Vn that exceeds the voltage Vn at which a leak is not detected is reached. + As the next voltage to be applied, if the CPU 20 detects no leak, it does not transport the paper P and sets the voltage Vn + Then, in step SA3, the CPU 20 applies the same voltage Vn + Determine whether or not a leak is detected by applying the voltage.

[0033] When the CPU 20 detects a leak in step SA3, it stops applying the voltage (step SA9). When the CPU 20 determines that a leak has been detected, it transports the paper P a predetermined distance (step SA10). This changes the portion to which the voltage is next applied in the transport direction of the paper P.

[0034] Furthermore, in step SA1, the CPU 20 sets a voltage to be next applied between the pair of rollers 40a, 40b holding the paper P therebetween.

[0035] When the CPU 20 determines that a leak has been detected, it detects a voltage Vn that is equal to or lower than the voltage Vn at which the leak was detected. - The CPU 20 sets the voltage Vn - Then, in step SA3, the CPU 20 applies the same voltage Vn - Determine whether or not a leak is detected by applying the voltage.

[0036] In this manner, the CPU 20 obtains the voltage-resistance characteristics of the paper P by applying a high voltage to the paper P while the paper P is sandwiched between the rollers 40a and 40b. min to maximum voltage V max The voltage is increased in a stepwise manner until the voltage reaches a voltage lower than the voltage applied when no leak occurs. Therefore, when the CPU 20 does not detect a leak, it next applies a voltage that exceeds the applied voltage when no leak occurs. In contrast, when the CPU 20 detects a leak, it transports the paper P to change the voltage application portion. Then, the CPU 20 applies a voltage that is equal to or lower than the applied voltage when the leak occurs, and acquires the voltage-resistance characteristics of the paper P.

[0037] Next, a process for determining the resistance Rn of the paper P from the voltage Vn applied between the pair of rollers 40a, 40b holding the paper P and the current An flowing between the rollers will be described.

[0038] The voltage applied between the pair of rollers 40a, 40b holding the paper P is divided by the resistance of the pair of rollers 40a, 40b and the resistance of the paper P. Meanwhile, the relationship between the voltage V0 applied between the pair of rollers 40a, 40b when the paper P is not being held and the current A0 flowing between the rollers is determined by the resistance of the rollers 40a, 40b. In order to find the resistance of the paper P, it is necessary to exclude the resistance of the pair of rollers 40a, 40b. Therefore, the voltage V0-current A0 characteristics when there is no paper P between the pair of rollers 40a, 40b are obtained in advance.

[0039] FIG. 4 is a graph showing an example of the voltage-current characteristic when there is no paper between the pair of rollers. FIG. 2B shows a measurement system in a state where no paper P is sandwiched between the pair of rollers 40a, 40b. The CPU 20 applies a predetermined voltage V0 between the pair of rollers 40a, 40b in a state where there is no paper P between the rollers, and obtains a current A0 flowing between the rollers. The CPU 20 changes the voltage V0 applied between the pair of rollers 40a, 40b, for example, from 0 KV to -7 KV in increments of -0.1 KV. As a result, the voltage V0-current A0 characteristic is obtained from the voltage V0 applied between the pair of rollers 40a, 40b and the current A0 flowing between the rollers in a state where there is no paper P between the pair of rollers 40a, 40b. The voltage V0-current A0 characteristic is a graph of the relationship between the voltage and the current, or an approximation equation that determines the relationship between the voltage and the current, as shown in FIG. 4. By referring to the voltage V0-current A0 characteristic, a voltage Vn0 determined by the resistance of the pair of rollers 40a, 40b can be obtained from an arbitrary current An.

[0040] As described above, the CPU 20 acquires the current An flowing between the pair of rollers 40a, 40b that sandwich the paper P when a voltage Vn is applied between the rollers. When a current An flows between the pair of rollers 40a, 40b, the CPU 20 acquires a voltage Vn0 determined by the resistance of the rollers from the voltage V0-current A0 characteristics.

[0041] The CPU 20 obtains the voltage Vn' applied to the paper P excluding the resistance of the rollers 40a, 40b by subtracting the voltage Vn0 from the voltage Vn. The CPU 20 obtains the resistance Rn of the paper P from the voltage Vn' and the current An. This makes it possible to obtain the resistance Rn of the paper P when the voltage Vn is applied between the pair of rollers 40a, 40b, excluding the resistance of the pair of rollers 40a, 40b.

[0042] FIG. 5 is an explanatory diagram showing the transition of the voltage applied between the pair of rollers, and next, the details of the operation for acquiring the voltage-resistance characteristics of the paper P will be described.

[0043] The CPU 20 controls the motor 41 to rotate the rollers 40a and 40b to transport the paper P. When a predetermined position in the transport direction of the paper P moves to a position facing the pair of rollers 40a and 40b, the CPU 20 stops driving the motor 41 to stop transport of the paper P.

[0044] The CPU 20 sets a voltage Vn to be applied between the pair of rollers 40a, 40b that sandwich the paper P therebetween.

[0045] The CPU 20 applies a voltage Vn between the pair of rollers 40a, 40b that sandwich the paper P using the high voltage application unit 30. The voltage application time for applying a voltage between the pair of rollers 40a, 40b and detecting the current is set in advance according to the type of paper P and the like. In this embodiment, the voltage application time is set to, for example, 300 ms. The voltage application time may be switched according to paper physical property information such as the type of paper P.

[0046] When the CPU 20 applies a voltage Vn between the pair of rollers 40a, 40b holding the paper P, the CPU 20 determines whether the leak detection unit 33 detects a leak during the voltage application time. If the CPU 20 determines that a leak is not detected, the CPU 20 obtains from the current detection unit 32 the current An flowing between the pair of rollers 40a, 40b holding the paper P.

[0047] First, the process when no leak is detected will be described. As described above, the CPU 20 sets the voltage Vn applied between the pair of rollers 40a and 40b to the minimum voltage V min to maximum voltage V max The voltage is increased in steps until

[0048] When no leak is detected, the CPU 20 sets the voltage applied between the pair of rollers 40a and 40b to a minimum voltage V min In this way, when no leakage is detected, the CPU 20 changes the voltage Vn which exceeds the voltage Vn at which no leakage is detected by a predetermined first change amount Vc1. + Set the next applied voltage to the minimum voltage V min In this embodiment, the maximum voltage V max is set to, for example, -7 KV in this embodiment. Furthermore, the first change amount Vc1 is set to, for example, -3 KV in this embodiment. Therefore, when no leak is detected, the voltage Vn applied between the pair of rollers 40a, 40b increases in steps from -1 KV to -7 KV in increments of -3 KV.

[0049] The CPU 20 may switch the voltage applied to the paper P and the change amount of the applied voltage in response to environmental information. The environmental information includes information related to humidity. Therefore, the CPU 20 may switch the voltage applied to the paper P and the change amount of the applied voltage in response to humidity detected by a humidity detection unit (not shown).

[0050] When the CPU 20 starts acquiring the voltage-resistance characteristics of the paper P, the voltage Vn applied between the pair of rollers 40a and 40b that hold the paper P is set to a predetermined minimum voltage V min The CPU 20 sets a minimum voltage V min (-1 KV) is applied. If the CPU 20 determines that no leak is detected, it acquires the current An1 flowing between the pair of rollers 40a, 40b that sandwich the paper P. Then, the CPU 20 obtains the resistance Rn1 of the paper P from the voltage V0-current A0 characteristics described above.

[0051] CPU20 has a minimum voltage of V min If no leakage is detected during the application of the voltage and it is determined that the voltage application time has elapsed, the application of the voltage is temporarily stopped.

[0052] When the CPU 20 determines that no leak is detected, it sets the voltage applied between the pair of rollers 40a, 40b that sandwich the paper P to voltage Vn2. In this embodiment, voltage Vn2 is set to, for example, −4 KV.

[0053] The CPU 20 applies a voltage Vn2 (-4 KV) between the pair of rollers 40a, 40b that sandwich the paper P. If the CPU 20 determines that no leak is detected, it acquires a current An2 that flows between the pair of rollers 40a, 40b that sandwich the paper P. Then, the CPU 20 obtains a resistance Rn2 of the paper P from the above-mentioned voltage V0-current A0 characteristics.

[0054] When the CPU 20 detects no leakage during application of the voltage Vn2 and determines that the voltage application time has elapsed, it temporarily stops the application of the voltage.

[0055] When the CPU 20 determines that no leak is detected, it sets the voltage applied between the pair of rollers 40a, 40b that sandwich the paper P to a voltage Vn3. In this embodiment, the voltage Vn3 is set to, for example, -7 KV. Therefore, the voltage Vn3 is set to the maximum voltage V max It is.

[0056] The CPU 20 applies a maximum voltage V between the pair of rollers 40a and 40b that hold the paper P. max (-7 KV) is applied. If the CPU 20 determines that no leak is detected, it acquires the current An3 flowing between the pair of rollers 40a, 40b that sandwich the paper P. Then, the CPU 20 obtains the resistance Rn3 of the paper P from the voltage V0-current A0 characteristics described above.

[0057] CPU20 has a maximum voltage of V max If no leakage is detected during application of the voltage and it is determined that the voltage application time has elapsed, the application of the voltage is stopped.

[0058] When the resistance of the paper P has been measured a predetermined number of times by applying a plurality of different voltages, the CPU 20 acquires the voltage-resistance characteristic of the paper P as a value corresponding to the paper resistance. In this embodiment, when the resistance of the paper P has been measured a predetermined number of times by applying voltages at three different points, the CPU 20 acquires the voltage-resistance characteristic of the paper P. The CPU 20 obtains the voltage-resistance characteristic of the paper P from the three voltages Vn1, Vn2, and Vn3, the corresponding currents An1, An2, and An3, and the resistances Rn1, Rn2, and Rn3. In this embodiment, the voltage Vn applied between the pair of rollers 40a and 40b increases in a stepwise manner from -1 KV to -7 KV in increments of -3 KV. Therefore, there are three possible values ​​of the voltage. However, this is not limited to this.

[0059] The CPU 20 calculates the resistance value when a constant voltage, for example, 1 KV, is applied to the paper regardless of the paper type, based on an approximation equation for the voltage-resistance characteristics of the paper P. Then, using the resistance value of the paper as a parameter, the CPU 20 determines the optimal secondary transfer conditions for the paper.

[0060] When no leak is detected and acquisition of the voltage-resistance characteristics of the paper P is completed, the CPU 20 may notify the user that the paper P is suitable for use.

[0061] Next, the process when a leak is detected will be described. When the CPU 20 determines that a leak is detected, it determines whether or not continued measurement is possible. When the CPU 20 determines that continued measurement is possible, it transports the paper P and changes the voltage application portion. In addition, the CPU 20 applies a voltage equal to or lower than the applied voltage when the leak occurred, and acquires the voltage-resistance characteristics of the paper P.

[0062] CPU20 has a minimum voltage of V min If it is determined that a leak is detected during the application of voltage, the application of voltage is stopped. In this case, it is deemed impossible to measure the paper characteristics, and no further measurements are performed.

[0063] The CPU20 operates at voltage Vn2 or maximum voltage V maxIf it is determined that a leak has been detected by the application of voltage, it is determined that continued measurement is possible and the application of voltage is temporarily stopped.

[0064] The CPU20 operates at voltage Vn2 or maximum voltage V max When it is determined that a leak has been detected by application of the signal, the paper P is conveyed. The CPU 20 detects the amount of rotation of the rollers 40a and 40b from the output of the encoder 42, and controls the motor 41 to rotate the rollers 40a and 40b one revolution. The reason why the rollers 40a and 40b are rotated one revolution to convey the paper P is to suppress variations due to eccentricity of the rollers 40a and 40b. When the next predetermined position in the conveying direction of the paper P moves to a position facing the pair of rollers 40a and 40b, the CPU 20 stops driving the motor 41 and stops conveying the paper P.

[0065] In the following, a process will be described in the case where a leak is detected when the voltage Vn2 is applied. When the CPU 20 determines that a leak is detected when the voltage Vn2 is applied, the CPU 20 sets the voltage to be applied between the pair of rollers 40a, 40b to the voltage Vn4.

[0066] After a leak is detected, the CPU 20 changes the voltage applied between the pair of rollers 40a, 40b from the voltage Vn2 by a second change amount Vc2. In this embodiment, the second change amount Vc2 is set to, for example, -1 KV. As a result, the voltage Vn4 is set to, for example, -3 KV in this embodiment. The voltage Vn4 is set to a voltage lower than the voltage Vn2, taking into consideration that a leak was detected when the voltage Vn2 was applied. However, since the part to which the voltage is applied to the paper P is changed, the voltage Vn4 may be the same voltage as Vn2.

[0067] The CPU 20 may change the amount of change in the applied voltage after a leak is detected in accordance with environmental information. The environmental information includes information related to humidity. Therefore, the CPU 20 may change the amount of change in the applied voltage after a leak is detected in accordance with humidity detected by a humidity detector (not shown).

[0068] The CPU 20 applies a voltage Vn4 (-3 kV) between the pair of rollers 40a, 40b that sandwich the paper P. If the CPU 20 determines that no leak is detected with the application of the voltage Vn4, it acquires a current An4 that flows between the pair of rollers 40a, 40b that sandwich the paper P. Then, the CPU 20 obtains a resistance Rn4 of the paper P from the above-mentioned voltage V0-current A0 characteristics.

[0069] When the CPU 20 detects no leakage during application of the voltage Vn4 and determines that the voltage application time has elapsed, it temporarily stops the application of the voltage.

[0070] When the CPU 20 determines that no leak is detected by applying the voltage Vn4, it sets the voltage applied between the pair of rollers 40a, 40b to the voltage Vn5. After the leak is detected, the CPU 20 changes the voltage applied between the pair of rollers 40a, 40b by -1 KV each time, as described above. As a result, the voltage Vn5 is set to -2 KV, for example, in this embodiment. Although no leak occurs when the voltage Vn4 is applied, there is a possibility that a leak may occur if a voltage equal to or higher than the voltage Vn2 is applied. Therefore, after the leak occurs, a voltage equal to or lower than the applied voltage when the leak occurs is applied, and the resistance is measured at as many points as possible, thereby ensuring the accuracy of the paper resistance characteristics.

[0071] The CPU 20 applies a voltage Vn5 (-2 KV) between the pair of rollers 40a, 40b that sandwich the paper P. If the CPU 20 determines that no leak is detected with the application of the voltage Vn5, it acquires a current An5 that flows between the pair of rollers 40a, 40b that sandwich the paper P. Then, the CPU 20 obtains a resistance Rn5 of the paper P from the above-mentioned voltage V0-current A0 characteristics.

[0072] When the CPU 20 determines that no leakage is detected during application of the voltage Vn5 and that the voltage application time has elapsed, it stops applying the voltage.

[0073] When the resistance of the paper P has been measured a predetermined number of times by applying different voltages, the CPU 20 acquires the voltage-resistance characteristics of the paper P. The CPU 20 obtains the voltage-resistance characteristics of the paper P from the voltages Vn1, Vn4, and Vn5 at three points, the corresponding currents An1, An4, and An5, and the resistances Rn1, Rn4, and Rn5.

[0074] When the CPU 20 determines that a leak has been detected by applying the voltage Vn4, it conveys the paper P by a predetermined amount. The CPU 20 also sets the voltage applied between the pair of rollers 40a, 40b to voltage Vn6. After a leak has been detected, the CPU 20 changes the voltage applied between the pair of rollers 40a, 40b by -1 KV each time, as described above. As a result, in this embodiment, the voltage Vn6 is set to, for example, -2 KV. Taking into consideration the fact that leaks have occurred consecutively, the voltage Vn6 is set to a voltage lower than the voltage Vn4.

[0075] The CPU 20 applies a voltage Vn6 (-2 KV) between the pair of rollers 40a, 40b that sandwich the paper P. If the CPU 20 determines that no leak is detected with the application of the voltage Vn6, it acquires a current An6 that flows between the pair of rollers 40a, 40b that sandwich the paper P. Then, the CPU 20 obtains a resistance Rn6 of the paper P from the above-mentioned voltage V0-current A0 characteristics.

[0076] When the CPU 20 detects no leakage during application of the voltage Vn6 and determines that the voltage application time has elapsed, it temporarily stops the application of the voltage.

[0077] If the CPU 20 determines that no leak is detected with the application of the voltage Vn6, it sets the voltage applied between the pair of rollers 40a, 40b to the voltage Vn7. After the leak is detected, the CPU 20 changes the voltage applied between the pair of rollers 40a, 40b in increments of -1 KV, as described above. In this case, however, the voltage V17 is set to -1 KV, which is the minimum voltage V min Overlaps with.

[0078] Therefore, the CPU 20 switches the amount of change in the voltage applied between the pair of rollers 40a, 40b to a third amount of change Vc3. In this embodiment, the third amount of change Vc3 is set to, for example, -0.5 KV. As a result, the voltage Vn7 is set to, for example, -1.5 KV in this embodiment.

[0079] The CPU 20 applies a voltage Vn7 (-1.5 KV) between the pair of rollers 40a, 40b that sandwich the paper P. If the CPU 20 determines that no leak is detected with the application of the voltage Vn7, it acquires a current An7 that flows between the pair of rollers 40a, 40b that sandwich the paper P. Then, the CPU 20 obtains a resistance Rn7 of the paper P from the above-mentioned voltage V0-current A0 characteristics.

[0080] When the CPU 20 detects no leakage during application of the voltage Vn7 and determines that the voltage application time has elapsed, it stops applying the voltage.

[0081] When the resistance of the paper P has been measured a predetermined number of times by applying different voltages, the CPU 20 acquires the voltage-resistance characteristics of the paper P. The CPU 20 obtains the voltage-resistance characteristics of the paper P from the voltages Vn1, Vn6, and Vn7 at three points, the corresponding currents An1, An6, and An7, and the resistances Rn1, Rn6, and Rn7.

[0082] When the CPU 20 determines that a leak has been detected by applying the voltage Vn6, it conveys the paper P by a predetermined distance. The CPU 20 also sets the voltage applied between the pair of rollers 40a, 40b to voltage Vn8. After a leak has been detected, the CPU 20 changes the voltage applied between the pair of rollers 40a, 40b by -1 KV increments, as described above. In this case, however, the voltage V18 is set to -1 KV, which is the minimum voltage V min Overlaps with.

[0083] Therefore, the CPU 20 switches the amount of change in the voltage applied between the pair of rollers 40a, 40b to the third amount of change Vc3, whereby the voltage Vn8 is set to, for example, −1.5 KV in this embodiment.

[0084] The CPU 20 applies a voltage Vn8 (-1.5 KV) between the pair of rollers 40a, 40b that sandwich the paper P. If the CPU 20 determines that no leak is detected with the application of the voltage Vn8, it acquires a current An8 that flows between the pair of rollers 40a, 40b that sandwich the paper P. Then, the CPU 20 obtains a resistance Rn8 of the paper P from the above-mentioned voltage V0-current A0 characteristics.

[0085] When the CPU 20 detects no leakage during application of the voltage Vn8 and determines that the voltage application time has elapsed, it stops applying the voltage.

[0086] When the resistance of the paper P has been measured a predetermined number of times by applying different voltages, the CPU 20 acquires the voltage-resistance characteristics of the paper P. In this case, the CPU 20 obtains the voltage-resistance characteristics of the paper P from the voltages Vn1 and Vn8 at two points, the currents An1 and An8 corresponding to these, and the resistances Rn1 and Rn8.

[0087] If the CPU 20 determines that a leak has been detected by applying the voltage Vn8, it stops applying the voltage. In this case, it is determined that the paper characteristics cannot be measured, and no further measurements are performed.

[0088] When a leak is detected, the CPU 20 may issue a notification to prompt a change in the type of paper P depending on the number of times the leak has occurred, or to adjust the installation environment of the image forming apparatus 1A. This is because if leakage occurs two or more times in one measurement, the paper may not be suitable for use. Also, the installation environment of the image forming apparatus 1A may be humid and unsuitable for image formation.

[0089] Maximum voltage V max If a leak is detected when the voltage Vn1 is applied, the same applies as if a leak was detected when the voltage Vn2 is applied. max When a leak is detected by applying the voltage V maxThe voltage is changed by -1 KV from the voltage applied portion. The CPU 20 then transports the paper P to change the voltage application portion. The CPU 20 then applies a voltage equal to or lower than the voltage applied when the leak occurred, and acquires the resistance of the paper P if no leak is detected. If a leak is detected, the CPU 20 transports the paper P to change the voltage application portion, and then applies a voltage equal to or lower than the voltage applied when the leak occurred. The CPU 20 acquires the voltage-resistance characteristics of the paper P when the resistance of the paper P has been measured a predetermined number of times with different voltage applications.

[0090] The voltage applied between the pair of rollers 40a and 40b is a maximum voltage V max If the voltage is changed by -1 KV from the start of the test, it may overlap with the voltage applied before the leak occurred. In this case, the change in the voltage applied between the pair of rollers 40a, 40b may be, for example, -2.5 KV. [Explanation of symbols]

[0091] 1A image forming apparatus, 2 control section, 20 CPU, 3 voltage application / detection section, 30 high voltage application section, 31 detection section, 32 current detection section, 33 leak detection section, 34 voltage detection section, 4 measurement section, 40a, 40b roller, 41 motor, 42 encoder

Claims

1. a voltage application member that applies a voltage to the paper; a current detection unit that detects a current flowing between the voltage application member and the paper; a discharge detection unit that detects whether or not a discharge occurs between the voltage application member and the paper; a control unit that applies a plurality of different voltages to the paper, and when the discharge detection unit does not detect the occurrence of a discharge, measures a value corresponding to the paper resistance, and when the discharge detection unit detects the occurrence of a discharge, changes a voltage application portion to the paper, applies a voltage equal to or lower than the applied voltage when the discharge occurred, and measures a value corresponding to the paper resistance; An image forming apparatus comprising:

2. A conveying member for conveying paper is provided, The control unit applies a voltage to the paper whose transport has been stopped by the voltage application member. The image forming apparatus according to claim 1 .

3. When the discharge detection unit detects the occurrence of a discharge, the control unit conveys the paper with the conveying member to change a portion to which a voltage is applied to the paper. The image forming apparatus according to claim 2 .

4. The conveying member includes a pair of rollers that grips the paper and conveys the paper by rotating. The pair of rollers are conductive, and the voltage application member is constituted by the pair of rollers. The image forming apparatus according to claim 3 .

5. When the discharge detection unit detects the occurrence of a discharge, the control unit rotates the pair of rollers once to transport the paper and changes a portion to which a voltage is applied to the paper. The image forming apparatus according to claim 4 .

6. The control unit switches the amount of change for changing the voltage to a value equal to or lower than the applied voltage at the time of discharge occurrence in accordance with the applied voltage. The image forming apparatus according to claim 1 .

7. The control unit switches a voltage application time to the paper in accordance with paper physical property information. The image forming apparatus according to claim 1 .

8. The control unit switches the voltage applied to the paper in response to environmental information. The image forming apparatus according to claim 1 .

9. The control unit switches the amount of change for changing the voltage to a value equal to or lower than the applied voltage at the time of discharge occurrence in accordance with environmental information. The image forming apparatus according to claim 8.

10. Environmental information includes humidity 10. The image forming apparatus according to claim 8 or 9.

11. When the discharge detection unit detects the occurrence of discharge, the control unit issues a notification to prompt a user to change the type of paper and / or adjust the environment according to the number of times discharge has occurred. The image forming apparatus according to claim 1 .

12. The control unit notifies the user that the paper is suitable for use when the discharge detection unit does not detect the occurrence of discharge and measurement of the value corresponding to the paper resistance is completed. The image forming apparatus according to claim 1 .

Images