Conveying device

Abstract

To prevent a direction of an electric field applied to a rubber layer of a charging roller for applying volts alternating current to a conveying belt from being fixed.SOLUTION: The transport device includes an endless transport belt 4, a drive source 5 that drives the transport belt, and a charging roller 6 that applies an volts alternating current to the transport belt 4, in which a circumferential length of the charging roller 6 is (2N + 1) times (N is an integer of 1 or more) a half cycle length that is a length of a charged region of the transport belt 4 corresponding to a half cycle of the volts alternating current. A drive source 5 for intermittently driving the transport belt 4 is provided, and the charging roller 6 rotates once every time the drive source 5 drives the transport belt 4 once.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a conveying device. [Background technology]

[0002] There is known a conveying device that attracts a sheet to a charged conveying belt. For example, the conveying device disclosed in Patent Documents 1 and 2 includes a charging roller that contacts the conveying belt and applies an AC voltage, and by charging the conveying belt alternately positively and negatively in the conveying direction, a higher attracting force is obtained than when the conveying belt is charged to a single polarity. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-127351 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to obtain a high adsorptive force in the configurations disclosed in Patent Documents 1 and 2, the width of the positively and negatively charged regions of the conveyor belt, i.e., the width of the charged region of the conveyor belt corresponding to a half cycle of the AC voltage (hereinafter referred to as the half-cycle length), needs to be shortened to a certain extent, and therefore the polarity of the voltage needs to be changed multiple times during one rotation of the charging roller. Here, when focusing on the relationship between the circumferential length of the charging roller and the half-cycle length, if the circumferential length of the charging roller is an even multiple of the half-cycle length, the direction of the electric field applied to the rubber layer of the charging roller is fixed, resulting in an uneven distribution of the conductive material in the rubber layer and a decrease in the ability to impart charge to the conveyor belt.

[0005] In consideration of the above circumstances, an object of the present invention is to prevent the direction of the electric field applied to the rubber layer of the charging roller that applies an AC voltage to the conveyor belt from being fixed. [Means for solving the problem]

[0006] In order to solve the above problem, the conveying device of the present invention comprises an endless conveying belt, a drive source that drives the conveying belt, and a charging roller that applies an AC voltage to the conveying belt, wherein the circumferential length of the charging roller is (2N+1) times (N is an integer greater than or equal to 1) the half-cycle length, which is the width of the charged area of ​​the conveying belt corresponding to half the cycle of the AC voltage.

[0007] The driving source may intermittently drive the transport belt, and the charging roller may rotate once every time the driving source drives the transport belt once.

[0008] The conveying device may include a power source that applies the AC voltage to the charging roller, and a control unit that controls the drive source and the power source, and when the rotation speed of the conveying belt caused by the drive source is changed, the control unit may change the period of the AC voltage applied by the power source in accordance with the rotation speed. [Effects of the Invention]

[0009] According to the present invention, it is possible to prevent the direction of the electric field applied to the rubber layer of the charging roller that applies an AC voltage to the transport belt from being fixed. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a front view schematically showing a conveying device according to an embodiment of the present invention; [Figure 2] FIG. 4 is a sequence diagram showing control signals for controlling a drive roller and a charging roller according to an embodiment of the present invention. [Figure 3] 10A to 10C are diagrams illustrating the movement of a reference point on the outer peripheral surface of a charging roller at various times according to an embodiment of the present invention. [Figure 4] FIG. 4 is a diagram showing the polarity distribution of a charging roller according to an embodiment of the present invention. [Figure 5] FIG. 4 is a diagram showing the polarity distribution of a charging roller according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, a conveying device 1 according to one embodiment of the present invention will be described with reference to the drawings.

[0012] 1 is a front view schematically showing a conveying device 1. The conveying device 1 is disposed, for example, below an inkjet head (not shown) and conveys a sheet S in a predetermined conveying direction Y. The conveying device 1 includes an endless conveying belt 4 and a charging roller 6 that applies an AC voltage to the conveying belt 4.

[0013] The conveyor belt 4 is wound around a drive roller 2 and a driven roller 3. The drive roller 2 is driven in direction A by a drive source 5 such as a motor. The charging roller 6 is pressed against the drive roller 2 via the conveyor belt 4. The charging roller 6 rotates in direction B together with the conveyor belt 4 due to frictional resistance with the conveyor belt 4. The charging roller 6 has a rubber layer in which conductive particles are dispersed (not shown). An AC voltage is applied to the charging roller 6 from a power source 7. A control unit 10 controls the drive source 5 and the power source 7. A pressure roller 8 is provided above the drive roller 2. The pressure roller 8 is urged downward to press the sheet S against the conveyor belt 4. A discharging brush 9 comes into contact with the sheet S being conveyed and dissipates electricity from the sheet S.

[0014] In this embodiment, a configuration is assumed in which the conveyor belt 4 is driven intermittently. For example, in the case of a serial type inkjet recording device (not shown) in which the inkjet head moves back and forth in a width direction intersecting with the conveyance direction Y, the inkjet head ejects ink while moving in either one of the width directions with the conveyance of the sheet S stopped. When it reaches the end point in the width direction, the inkjet head returns to the start point. Next, the sheet S is conveyed a predetermined distance and stops, and the inkjet head ejects ink while moving in one direction. By repeating this operation, an image is formed on the sheet S.

[0015] FIG. 2 is a sequence diagram showing the control signals that control the drive roller 2 and the charging roller 6. The control signal to the drive roller 2 intermittently repeats ON (T=T0) and OFF (T=T3). This causes the conveyor belt 4 to be driven intermittently. The start of application of voltage to the charging roller 6 (T=T1) is slightly delayed from the ON of the drive roller 2. The end of application of voltage to the charging roller 6 (T=T2) is slightly earlier than the OFF of the drive roller 2.

[0016] 3 is a diagram showing the movement of the reference point 6R on the outer peripheral surface of the charging roller 6 at each timing (the conveyor belt 4 is not shown). The charging roller 6 makes one rotation between the ON (T=T0) and OFF (T=T3) of the driving roller 2.

[0017] Here, the relationship between the width of the positively and negatively charged areas of the conveyor belt 4, that is, the width of the charged area of ​​the conveyor belt 4 corresponding to half a cycle of the AC voltage (hereinafter referred to as half cycle length), and the circumferential length of the charging roller 6 will be described.

[0018] Figure 2(A) shows the control signal when the circumference is equal to the half-cycle length. In this case, a voltage of either positive or negative polarity is applied between the ON and OFF states of the drive roller 2 (i.e., during one rotation of the charging roller 6). Because the direction of the electric field applied to the charging roller 6 reverses with each rotation, it is difficult for the distribution of the conductive material in the rubber layer to become uneven. However, because the half-cycle length is longer, the improvement in the adhesive force is small. To further improve the adhesive force, it is necessary to shorten the half-cycle length.

[0019] 2B shows the control signal when the circumference is twice the half-period length. In this case, the polarity of the voltage is reversed between the first half-rotation of the charging roller 6 and the subsequent half-rotation, but the direction of the electric field applied to the charging roller 6 is fixed, resulting in an uneven distribution of the conductive material in the rubber layer.

[0020] FIG. 4 is a diagram showing the polarity distribution of the charging roller 6. This diagram shows the distribution of the electric field applied to the charging roller 6 during one rotation of the charging roller 6, with T=T1 as the reference point. The area that comes into contact with the conveyor belt 4 during the half rotation of the charging roller 6 from T=T1 is positively charged, and the area that comes into contact with the conveyor belt 4 during the subsequent half rotation of the charging roller 6 is negatively charged. When the circumference is 2N times the half-period length (N is an integer greater than or equal to 1), a phenomenon similar to that in the case of twice the circumference occurs at a period corresponding to N.

[0021] 2C shows a control signal when the circumference is three times the half-period length. In this case, the polarity of the voltage changes every one-third of the rotation of the charging roller 6.

[0022] 5 is a diagram showing the polarity distribution of the charging roller 6. During the first rotation (see FIG. 5(D)), the area that comes into contact with the conveyor belt 4 during the one-third rotation of the charging roller 6 from T=T1 is positively charged, and thereafter, the area that comes into contact with the conveyor belt 4 during the one-third rotation of the charging roller 6 is negatively charged, and thereafter, the area that comes into contact with the conveyor belt 4 during the one-third rotation of the charging roller 6 is positively charged.

[0023] In contrast, during the next rotation (see FIG. 5(E)), the area that contacts the conveyor belt 4 during the one-third rotation of the charging roller 6 from T=T1 is negatively charged, and then the area that contacts the conveyor belt 4 during the one-third rotation of the charging roller 6 is positively charged, and then the area that contacts the conveyor belt 4 during the one-third rotation of the charging roller 6 is negatively charged. In this way, the direction of the electric field applied to the rubber layer of the charging roller 6 reverses with each rotation, making it difficult for the conductive material in the rubber layer to become unevenly distributed. When the circumference is (2N+1) times the half-period length (N is an integer greater than or equal to 1), a phenomenon similar to that in the case of three times occurs at a period corresponding to N.

[0024] The conveying device 1 according to the present embodiment described above includes an endless conveying belt 4, a driving source 5 that drives the conveying belt 4, and a charging roller 6 that applies an AC voltage to the conveying belt 4, and the circumferential length of the charging roller 6 is (2N+1) times (N is an integer equal to or greater than 1) the half-cycle length, which is the width of the charged region of the conveying belt 4 corresponding to a half cycle of the AC voltage. According to this embodiment, it is possible to prevent the direction of the electric field applied to the rubber layer of the charging roller 6 that applies an AC voltage to the conveying belt 4 from being fixed.

[0025] Furthermore, in the conveying device 1 according to this embodiment, the driving source 5 intermittently drives the conveying belt 4, and the charging roller 6 rotates once each time the driving source 5 drives the conveying belt 4 once. According to this embodiment, even when the conveying belt 4 is driven intermittently, the direction of the electric field applied to the rubber layer of the charging roller 6 can be prevented from being fixed.

[0026] The above embodiment may be modified as follows.

[0027] In addition to the configuration of the above embodiment, the control unit 10 may perform the following control. The conveying device 1 includes a power source 7 that applies an AC voltage to the charging roller 6 and a control unit 10 that controls the drive source 5 and the power source 7. When the rotation speed of the conveyor belt 4 driven by the drive source 5 is changed, the control unit 10 changes the cycle of the AC power applied by the power source 7 in accordance with the rotation speed. For example, the control unit 10 slows the rotation speed of the conveyor belt 4 when the image density is equal to or higher than a threshold value or when a thicker sheet S is used. In this case, the control unit 10 lengthens the cycle of the AC power in accordance with the rate of decrease in the rotation speed. According to this embodiment, even when the rotation speed of the conveyor belt 4 is changed, the direction of the electric field applied to the rubber layer can be prevented from being fixed.

[0028] In the above embodiment, an example has been shown in which the conveyor belt 4 is driven intermittently, but the present invention is also applicable to a configuration in which the conveyor belt 4 is driven continuously during the execution of one image forming job. [Explanation of symbols]

[0029] 4 conveyor belt 5. Drive source 6 Charging roller 7 Power supply 10 Control Unit

Claims

1. an endless conveyor belt; a drive source that drives the conveyor belt; a charging roller that applies an AC voltage to the conveying belt, A conveying device characterized in that the peripheral length of the charging roller is (2N+1) times (N is an integer greater than or equal to 1) the half-cycle length, which is the width of the charged area of ​​the conveying belt corresponding to half the cycle of the AC voltage.

2. the drive source intermittently drives the conveyor belt; 2. The transport device according to claim 1, wherein the charging roller rotates once each time the drive source drives the transport belt once.

3. a power source that applies the AC voltage to the charging roller; a control unit that controls the drive source and the power source, The conveying device according to claim 1 or 2, characterized in that, when the rotation speed of the conveying belt driven by the driving source is changed, the control unit changes the period of the AC voltage applied by the power source in accordance with the rotation speed.

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