JP2021148924A - Image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus that can appropriately convey a sheet by using two conveying rollers.SOLUTION: An image forming apparatus comprises: first conveying members 83, 85 and second conveying members 41, 71 that are arranged on the upstream side and the downstream side in a conveyance direction of a sheet; a first motor 87 that drives the first conveying members; a second motor 73 that drives the second conveying members; first current measuring means 89 that measures a load current of the first motor 87; a first sheet detection sensor 91 that is arranged between the first conveying members and the second conveying members; and a control unit, and comprises the control unit that detects a variation in current in the first motor 87 from a result of measurement performed by the first current measuring means 89, and based on a sheet conveyance time and a current variation value of the first motor 87 from the time of detection of the current variation until a time at which a sheet is detected by the first sheet detection sensor 91, adjusts the number of rotations of the second motor 73 and the voltage applied to the second motor 73.SELECTED DRAWING: Figure 2

Description

The present invention relates to an image forming apparatus including a plurality of transport roller pairs for transporting paper.

In the image forming apparatus, the paper is often sandwiched and conveyed by two transfer roller pairs arranged on the upstream side and the downstream side in the transfer direction.

For example, when the toner image is transferred from the intermediate transfer belt to the paper, the upstream part of the paper is sandwiched between the resist nips between the two resist rollers, and the downstream part of the paper is the intermediate transfer belt and the secondary transfer. It is sandwiched between the transfer nips with the rollers. In such a case, if there is a difference between the paper transfer speed at the resist nip and the paper transfer speed at the transfer nip, the paper may bend or be pulled, and the toner image cannot be transferred accurately. There is. Further, when the toner image is fixed on the paper, the upstream portion of the paper is sandwiched by the transfer nip, and the downstream portion is sandwiched by the fixing nip between the fixing roller and the fixing belt. In such a case, if there is a difference between the paper transport speed at the transfer nip and the paper transport speed at the fixing nip, it causes wrinkles.

In Patent Document 1, the transport load related to the second transport means arranged on the downstream side is detected, and based on the detected transport load, the first transport means and the second transport arranged on the upstream side are detected. A recording device is disclosed that adjusts the transport speed of at least one of the means to reduce the tension applied to the second transport means to zero.

Japanese Unexamined Patent Publication No. 2011-11299

In the recording device of Patent Document 1, the encoder sensor detects the recording medium transfer speed of each transfer means. In this case, the transport speed detected by the encoder sensor may differ from the actual transport speed depending on the thickness and weight of the paper and the configuration of the device. Therefore, there is a possibility that the transport speed of each transport means cannot be adjusted accurately.

In consideration of the above circumstances, it is an object of the present invention to provide an image forming apparatus capable of appropriately transporting paper without causing bending or wrinkles by using two transport roller pairs.

In order to achieve the above object, the image forming apparatus of the present invention is arranged on the upstream side and the downstream side in the paper transport direction, respectively, and the first transport member and the second transport member that sandwich and transport the paper on both sides. A first motor for driving the first transport member, a second motor for driving the second transport member, a first current measuring means for measuring the load current of the first motor, and the first transport member. The current fluctuation of the first motor is detected from the measurement results of the first paper detection sensor arranged between the second transfer member and the first current measuring means, and the first paper is detected from the current fluctuation detection time. Control to adjust the rotation speed of the second motor and the voltage applied to the second motor based on the paper transport time up to the time when the paper is detected by the detection sensor and the current fluctuation value of the first motor. It is characterized by having a part and.

In the image forming apparatus of the present invention, when the transfer time is shorter than the estimated time, the control unit increases the rotation speed of the second motor to be larger than the reference rotation speed, and the transfer time is longer than the estimated time. If it is long, the rotation speed of the second motor is made smaller than the reference rotation speed, and if the current fluctuation value is larger than the assumed value, the voltage applied to the second motor is applied as the reference. When the voltage is higher than the voltage and the current fluctuation value is smaller than the assumed value, the voltage applied to the second motor may be lower than the reference applied voltage.

In the image forming apparatus of the present invention, a third transport member arranged downstream of the second transport member in the transport direction and sandwiching and transporting the paper together with the second transport member, and the third transport member. A third motor for driving the motor, a second current measuring means for measuring the load current of the second motor, a second paper detection sensor arranged between the second transport member and the third transport member, and the like. The control unit detects the current fluctuation of the second motor from the load current measured by the second current measuring means, and the paper is detected by the second paper detection sensor from the current fluctuation detection time. It may be characterized in that the rotation speed of the third motor and the voltage applied to the third motor are adjusted based on the paper transport time up to the time and the current fluctuation value of the second motor.

In the image forming apparatus of the present invention, a third transport member arranged downstream of the second transport member in the transport direction and sandwiching and transporting the paper together with the second transport member, and the third transport member. The control unit further includes a third motor for driving the motor, and the control unit detects the current fluctuation of the first motor from the measurement result of the first current measuring means, and uses the first paper detection sensor from the current fluctuation detection time. Based on the paper transport time up to the time when the paper is detected and the current fluctuation value of the first motor, the rotation speed of the second motor, the voltage applied to the second motor, and the third motor It may be characterized by adjusting the number of revolutions and the voltage applied to the third motor.

In the image forming apparatus of the present invention, the first transport member is a pair of resist rollers for adjusting the paper transport timing, and the second transport member is an intermediate transfer belt on which a toner image is carried and the toner image. It is a transfer roller that transfers from an intermediate transfer belt to paper, and the third transport member may be characterized as a fixing device that fixes a toner image on paper.

According to the present invention, the paper transport time by the downstream transport member is adjusted to be equal to the actual paper transport time by the upstream transport member, so that the paper is transported without causing bending or wrinkles. can do.

It is sectional drawing which shows typically the internal structure of the image forming apparatus which concerns on one Embodiment of this invention. FIG. 5 is a diagram schematically showing a main transport path from a resist nip to a fixing nip in an image forming apparatus according to an embodiment of the present invention. It is a block diagram of the control part of the image forming apparatus which concerns on one Embodiment of this invention. It is a flowchart which shows the paper transport operation of the image forming apparatus which concerns on one Embodiment of this invention. It is a flowchart which shows the paper transport operation (applied voltage adjustment processing) of the image forming apparatus which concerns on one Embodiment of this invention.

Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings.

First, the overall configuration of the image forming apparatus will be described with reference to FIGS. 1 and 2. FIG. 1 is a front view schematically showing an image forming apparatus, and FIG. 2 is a view schematically showing a main transport path from a resist nip to a fixing nip. In the following description, the front side of the paper surface of FIG. 1 is referred to as the front side (front side) of the image forming apparatus. L and R shown in each figure indicate the left side and the right side of the image forming apparatus.

The device main body 2 of the image forming apparatus 1 is provided with a paper feed cassette 3, a paper feeding device 5, an image forming unit 7, a fixing device 9, an ejection device 11, an ejection tray 13, and a transport path for paper S. A cover unit 15 and a transport unit 17 to be formed are provided.

The paper cassette 3 accommodates the paper S. The paper cassette 3 is detachably housed in the lower part of the apparatus main body 2 along the front-rear direction. The paper feed device 5 is arranged above the paper feed cassette 3 and feeds the paper S from the paper feed cassette 3.

The image forming unit 7 is arranged above the paper feed cassette 3, and is arranged above the exposure device 21 and the exposure device 21, and is provided for each of the four color (yellow, magenta, cyan, black) toners. It includes a forming unit 23, an intermediate transfer unit 25 arranged above the image forming unit 23, and a toner container 27 arranged above the intermediate transfer unit 25 and containing toner of each color.

Each image forming unit 23 includes a photoconductor drum 31, a charging device 33, a developing device 35, and a cleaning device 37 arranged along the periphery of the photoconductor drum 31. The charging device 33 charges the photoconductor drum 31. The photoconductor drum 31 is charged by the charging device 33 and then exposed by the exposure device 21. As a result, an electrostatic latent image is formed on the photoconductor drum 31. The developing device 35 develops the electrostatic latent image formed on the photoconductor drum 31 with the toner supplied from the corresponding toner container 27. The cleaning device 37 removes the toner remaining on the surface of the photoconductor drum 31.

The intermediate transfer unit 25 includes an endless intermediate transfer belt 41 and four primary transfer rollers 43 arranged in a hollow portion of the intermediate transfer belt 41. The intermediate transfer belt 41 is wound between the driving roller 45 and the driven roller 47. The primary transfer roller 43 faces the photoconductor drum 31 with the intermediate transfer belt 41 interposed therebetween, and forms a primary transfer nip between the intermediate transfer belt 41 and the photoconductor drum 31.

The fixing device 9 is arranged above the image forming portion 7, and includes a fixing roller 51 and a fixing belt 53. The fixing roller 51 and the fixing belt 53 are examples of the third conveying member. As shown in FIG. 2, a fixing nip Nf is formed between the fixing roller 51 and the fixing belt 53. The fixing roller 51 is connected to the fixing motor 55 and is driven by the fixing motor 55 to rotate. The fixing motor 55 is an example of the third motor. The fixing belt 53 is driven by the fixing roller 51 and circulates.

With reference to FIG. 1 again, the discharge device 11 is arranged above the fixing device 9. The discharge tray 13 is formed on the upper surface of the device main body 2 below the discharge device 11.

The cover unit 15 is rotatably supported around the lower end portion by an opening formed on the right side surface of the apparatus main body 2. The transport unit 17 is rotatably supported inside the cover unit 15 around the lower end portion. A main transport path 61 for transporting the paper S from the paper feed cassette 3 toward the discharge device 11 is formed between the transport unit 17 and the apparatus main body 2. A reversing path 63 for double-sided printing is formed between the cover unit 15 and the transport unit 17. In the following description, the upstream side and the downstream side indicate the upstream side and the downstream side in the transport direction of the paper S along the main transport path 61.

The secondary transfer roller 71 is supported on the inner surface of the transfer unit 17 (the surface facing the main transfer path 61). When the transfer unit 17 rotates so as to form the main transfer path 61, the secondary transfer roller 71 contacts the intermediate transfer belt 41 and forms a secondary transfer nip Nt between them as shown in FIG. do. The secondary transfer roller 71 and the intermediate transfer belt 41 are examples of the second transfer member. The secondary transfer roller 71 is connected to the transfer motor 73 and is driven by the transfer motor 73 to rotate. The transfer motor 73 is an example of the second motor. A second current measuring circuit 75 (current sense amplifier or the like) is connected to the transfer motor 73. The second current measuring circuit 75 is an example of the second current measuring means.

Further, the main transport path 61 is provided with a resist roller pair 81 on the upstream side of the secondary transfer nip Nt. The resist roller pair 81 is an example of the second conveying member, and includes a driving roller 83 and a driven roller 85. The drive roller 83 is supported by the apparatus main body 2, and the driven roller 85 is supported by the inner surface of the transport unit 17. When the transport unit 17 rotates so as to form the main transport path 61, the driven roller 85 comes into contact with the drive roller 83 to form a resist nip Nr between the two rollers as shown in FIG. The drive roller 83 is connected to the resist motor 87 and is driven by the resist motor 87 to rotate. The resist motor 87 is an example of the first motor. A first current measuring circuit 89 (current sense amplifier or the like) is connected to the resist motor 87. The first current measuring circuit 89 is an example of the first current measuring means.

Further, as shown in FIG. 2, the main transport path 61 is provided with a first paper detection sensor 91 between the resist nip Nr and the secondary transfer nip Nt, and the secondary transfer nip Nt and the fixing nip Nt are provided. A second paper detection sensor 93 is provided between the Nf and the Nf. Each paper detection sensor includes, for example, an actuator that rotates in contact with the paper S transported along the main transport path 61, and an optical sensor in which an optical path is formed or blocked by the actuator. When the actuator rotates so as to cross the main transport path 61 to block (or form) the optical path, each paper detection sensor outputs an OFF signal. When the actuator contacts the paper S transported along the main transport path 61 and rotates to form (or cut off) an optical path, each paper detection sensor outputs an ON signal.

The image forming operation will be briefly described. In each image forming unit 23, after the photoconductor drum 31 is charged by the charging device 33, the exposure device 21 performs exposure corresponding to the image data, and an electrostatic latent image is formed on the photoconductor drum 31. The electrostatic latent image is developed into a toner image by the developing device 35. The toner image is transferred from the photoconductor drum 31 to the intermediate transfer belt 41 at the primary transfer nip. By superimposing and transferring the toner images developed by the four image forming units 23 on the intermediate transfer belt 41, a full-color toner image is formed on the intermediate transfer belt 41. The toner remaining on each photoconductor drum 31 is removed by the cleaning device 37.

On the other hand, the paper S sent out from the paper feed cassette 4 is conveyed along the main conveying path 61, and the conveying timing is adjusted by the resist roller pair 81. Then, at the secondary transfer nip Nt, the full-color toner image formed on the intermediate transfer belt 41 is transferred to the paper S. The paper S on which the full-color toner image is transferred is conveyed to the fixing device 9, and the toner image is transferred to the paper S by the fixing device 9. The paper S on which the toner image is fixed is discharged from the discharge device 11 to the discharge tray 13.

Next, the control unit 101 of the image forming apparatus 1 will be described with reference to the block diagram of FIG.

The control unit 101 is electrically connected to the first and second paper detection sensors 91 and 93, and an OFF signal and an ON signal are input from the first and second paper detection sensors 91 and 93. When the ON signal is input, the control unit 101 determines that the paper S has passed the detection position (the position where the actuator crosses the main transport path 61), and the time when the paper S passes the detection position (the paper detection time). To remember).

The control unit 101 is electrically connected to the first and second current measurement circuits 89 and 75, and the current values measured by the first and second current measurement circuits 89 and 75 are input. The control unit 101 monitors the absolute value of the input current value at regular intervals, and if it is monitored that the value exceeds a predetermined value (maximum, minimum), it determines that the current value fluctuates.

The control unit 101 is electrically connected to the fixing motor 55, the transfer motor 73, and the resist motor 87. The control unit 101 controls the rotation speed of each motor and the voltage applied to each motor. For example, the applied voltage can be finely adjusted by performing pulse width modulation (PWM, Pulse Width Modulation) of the switching circuit connected to each motor.

Further, when the reference paper (plain paper) is conveyed to the storage unit (EEPROM or the like) of the control unit 101 at the reference speed, the paper S is conveyed from the resist nip Nr to the detection position of the first paper detection sensor 91. The time (assumed time Ts) and the transport time of the paper S from the secondary transfer nip Nt to the detection position of the second paper detection sensor 93 (assumed time Ts) are stored. Further, the load current values (assumed value Is) of the resist motor 87 and the transfer motor 73 when the reference paper (plain paper) is conveyed to the storage unit at the reference speed of the resist nip Nr and the secondary transfer nip Nt. ) Is remembered.

In the image forming apparatus 1 having the above configuration, the transport operation of the paper S along the main transport path 61 will be described with reference to the flowcharts of FIGS. 2, 4 and 5. The arrow X in FIG. 2 indicates the paper transport direction.

As shown in FIG. 2, the paper S fed from the paper feed cassette 3 by the paper feed device 5 has a resist roller pair 81 (driving roller 83 and driven roller 83) in the resist nip Nr-secondary transfer nip Nt section R1. It is sandwiched between (between 85) and between the intermediate transfer belt 41 and the secondary transfer roller 71 and conveyed. After that, in the secondary transfer nip Nt-fixing nip Nf section R2, the intermediate transfer belt 41 and the secondary transfer roller 71 and the fixing device 9 (between the fixing roller 51 and the fixing belt 53) are sandwiched and conveyed. NS. The transport speed of the paper S in the resist nip Nr, the secondary transfer nip Nt, and the fixing nip Nf is set to the reference speed. Here, the transfer operation of the paper S in the resist nip Nr-secondary transfer nip Nt section R1 will be described.

First, it will be described with reference to the flowchart of FIG. When the transfer of the paper S is started in step S1, the load current value is transmitted to the control unit 101 from the first current measuring circuit 89 connected to the resist motor 87 in step S2.

In step S3, the control unit 101 calculates the current fluctuation value (Ia) from the transmitted load current value, and the absolute value of the current fluctuation value (Ia) is equal to or more than a predetermined minimum value (Imin) and is predetermined. It is determined whether or not it is equal to or less than the maximum value (Imax). When it is determined that the current fluctuation value (Ia) is equal to or greater than the predetermined minimum value (Imin) and equal to or less than the predetermined maximum value (Imax), the process proceeds to step S4. In step S4, the control unit 101 stores the time (Ta) at which the load current starts to fluctuate and the current fluctuation value (Ia), and proceeds to step S5. When the paper S passes through the resist nip Nr, a load is applied to the drive roller 83 from the paper S, and the load current of the resist motor 87 fluctuates (increases). That is, the time when the load current of the resist motor 87 starts to fluctuate (Ta, the time when the current fluctuation starts) indicates the time when the paper S passes through the resist nip Nr.

In step S5, the control unit 101 determines whether or not the ON signal is input from the first paper detection sensor 91, that is, whether or not the paper S has passed the detection position of the first paper detection sensor 91. When the control unit 101 determines that the paper S has passed the detection position of the first paper detection sensor 91, the control unit 101 stores the paper detection time (Tb) and proceeds to step S6. In step S6, the control unit 101 calculates the transport time (Tv) from the resist nip Nr to the detection position of the first paper detection sensor 91 from the current fluctuation start time (Ta) and the paper detection time (Tb), and steps. Proceed to S7.

In step S7, the control unit 101 determines whether or not the transport time (Tv) is equal to the assumed time (Ts). If the transport time (Tv) and the estimated time (Ts) are equal, the process proceeds to step S8. The case where the transport time (Tv) and the estimated time (Ts) are equal includes the case where the difference (absolute value) between the transport time (Tv) and the estimated time (Ts) is smaller than a predetermined value. In step S8, the control unit 101 executes the applied voltage adjustment process. The applied voltage adjustment process will be described later.

On the other hand, if the transport time (Tv) and the estimated time (Ts) are different in step S7, the process proceeds to step S9. In step S9, the control unit 101 determines whether the transport time (Tv) is shorter than the assumed time (Ts). If it is determined that the transport time (Tv) is shorter than the assumed time (Ts), the process proceeds to step S10.

In step S10, the control unit 101 increases the rotation speed of the transfer motor 73 to increase the transfer speed in the secondary transfer nip Nt. When the transport time (Tv) is shorter than the assumed time (Ts), the transport speed at the resist nip Nr is faster than the reference transport speed, that is, faster than the transport speed at the secondary transfer nip Nt. In this case, transfer failure of the toner image may occur due to the speed difference. Therefore, the rotation speed of the transfer motor 73 is increased to make the transfer speed at the secondary transfer nip Nt equal to the transfer speed at the resist nip Nr. In this case, for example, the control unit 101 stores the relationship between the difference between the transport time (Tv) and the estimated time (Ts) and the rate of change of the rotation speed. For example, when the difference (absolute value) is 0.1 mm / s, the rate of change is 1.1, and when the difference is 0.3 mm / s, the rate of change is 1.3. Then, the rotation speed of the transfer motor 73 is adjusted to the rotation speed obtained by multiplying the reference rotation speed by the rate of change according to the obtained difference.

After that, the process proceeds to step S8, and the control unit 101 executes an applied voltage adjustment process described later.

On the other hand, if it is determined in step S9 that the transport time (Tv) is longer than the assumed time (Ts), the process proceeds to step S12. In step S12, the control unit 101 lowers the rotation speed of the transfer motor 73 to slow down the transfer speed at the secondary transfer nip Nt. If the transport time (Tv) is longer than the assumed time (Ts), the transport speed at the resist nip Nr will be slower than the transport speed at the secondary transfer nip Nt, and there is a risk that toner image transfer defects will occur due to the speed difference. be. Therefore, the rotation speed of the transfer motor 73 is reduced so that the transfer speed at the secondary transfer nip Nt is equal to the transfer speed at the resist nip Nr. In this case as well, when the difference (absolute value) is 0.1 mm / s, the rate of change is 0.9, and when the difference is 0.3 mm / s, the rate of change is 0.7, as in step S10. .. Then, the rotation speed of the transfer motor 73 is adjusted to the rotation speed obtained by multiplying the reference rotation speed by the rate of change according to the obtained difference.

After that, the process proceeds to step S8, and the control unit 101 executes an applied voltage adjustment process described later.

Next, the applied voltage adjustment process (step S8) will be described with reference to the flowchart of FIG.

First, in step S101, the control unit 101 determines whether or not the current fluctuation value (Ia) is equal to the assumed value (Is). The case where the current fluctuation value (Ia) and the assumed value (Is) are equal means that the difference (absolute value) between the current fluctuation value (Ia) and the assumed value (Is) is smaller than a predetermined value. include. When the current fluctuation value (Ia) and the assumed value (Is) are equal, the control is terminated. On the other hand, if the current fluctuation value (Ia) and the assumed value (Is) are different, the process proceeds to step S102. In step S102, the control unit 101 determines whether the current fluctuation value (Ia) is smaller than the assumed value (Is). If the current fluctuation value (Ia) is smaller than the assumed value (Is), the process proceeds to step S103.

In step S103, the control unit 101 lowers the voltage applied to the transfer motor 73. When the current fluctuation value (Ia) is smaller than the assumed value (Is), for example, the thickness of the paper S may be thinner than the thickness of the reference paper (plain paper), and the transport load of the drive roller 83 may be small. Then, since the nip force at the secondary transfer nip Nt is adjusted according to the reference paper, it is assumed that the current nip force is too high for the paper S. In such a case, problems such as wrinkling of the paper S may occur. Therefore, the voltage applied to the transfer motor 73 is lowered to reduce the nip force at the secondary transfer nip Nt. In this case, for example, the control unit 101 stores the relationship between the difference between the current fluctuation value (Ia) and the assumed value (Is) and the rate of change of the applied voltage. For example, when the difference (absolute value) is 0.1 mA, the rate of change is 0.9, and when the difference is 0.3 mA, the rate of change is 0.7. Then, the applied voltage is adjusted to the applied voltage obtained by multiplying the reference applied voltage by the rate of change according to the obtained difference.

On the other hand, in step S102, if the current value (Ia) is not smaller than the assumed value (Is) (if it is larger), the process proceeds to step S104. In step S11, the control unit 101 raises the voltage applied to the transfer motor 73. When the current value (Ia) is larger than the assumed value (Is), the thickness of the paper S may be thicker than the thickness of the reference paper (plain paper), and the transport load of the drive roller 83 may be large. In this case, since it is assumed that the current nip force is insufficient for the paper S, the voltage applied to the transfer motor 73 is increased to increase the nip force in the secondary transfer nip Nt. In this case as well, when the difference (absolute value) between the current fluctuation value (Ia) and the device value (Is) is 0.1 mA, the rate of change is 1.1 and the difference is 0.3 mA, as in step S103. In this case, the rate of change is 1.3. Then, the applied voltage is adjusted to the applied voltage obtained by multiplying the reference applied voltage by the rate of change according to the obtained difference.

The secondary transfer nip Nt-fixing nip Nf section R2 also controls the fixing motor 55 in the same manner as the resist nip Nr-secondary transfer nip Nt section R1. That is, the transfer time is calculated from the current fluctuation start time of the transfer motor 73 and the paper detection time of the second paper detection sensor 93. Then, the rotation speed of the fixing motor 55 and the applied voltage are adjusted according to the transfer time and the current fluctuation value of the transfer motor 73. Specifically, when the transfer time is shorter than the estimated time (Ts), the control unit 101 increases the rotation speed of the fixing motor 55 to be higher than the reference rotation speed, and the transfer time is longer than the estimated time (Ts). If it is long, the rotation speed of the fixing motor 55 is made smaller than the reference rotation speed. Further, when the current fluctuation value is larger than the assumed value (Is), the voltage applied to the fixing motor 55 is made higher than the reference applied voltage, and when the current fluctuation value is smaller than the assumed value (Is), the fixing is performed. The applied voltage to the motor 55 is made lower than the reference applied voltage.

As described above, according to the present invention, the paper S is sandwiched between the transport member on the upstream side (for example, resist roller pair 81) and the transport member on the downstream side (for example, the secondary transfer roller 71 and the intermediate transfer belt 41). The transport time of the paper S by the transport member on the downstream side can be adjusted to be equal to the transport time of the paper S by the transport member on the upstream side. Further, the conveying force of the paper S by the conveying member on the downstream side can be adjusted according to the conveying force of the paper S by the conveying member on the upstream side. The transport speed of the paper S and the load current of the motor vary depending on the thickness of the paper S, the wear of the rollers, and the like. Therefore, the rotation speed and the applied voltage of the motor of the transport member (roller) on the downstream side are adjusted based on the fluctuation of the transport speed of the paper S of the transport member on the upstream side and the load current of the motor.

For example, when the number of printed sheets increases and the drive roller 83 of the resist roller pair 81 wears, the frictional force between the paper S and the drive roller 83 in the resist nip Nr decreases. Then, the transport speed of the paper S in the resist nip Nr becomes slower than the standard transport speed, and the transport time of the paper S from the resist nip Nr to the detection position of the first paper detection sensor 91 becomes longer. In this case, the rotation speed of the transfer motor 73 on the downstream side of the resist nip Nr is reduced to slow down the transfer speed of the paper S in the secondary transfer nip Nt. As a result, the paper S can be conveyed at the same transfer speed at both nips, so that transfer defects can be prevented.

Further, when the thickness of the paper S is thicker than the thickness of the plain paper, the load applied to the drive roller 83 at the resist nip Nr increases, and the load current of the resist motor 87 increases. In this case, the voltage applied to the transfer motor 73 on the downstream side of the resist nip Nr is increased to increase the nip force in the secondary transfer nip Nt. As a result, the paper S can be conveyed with an appropriate conveying force in the secondary transfer nip Nt.

Therefore, when the paper S passes through the resist nip Nr-secondary transfer nip Nt section R1, the toner image can be transferred from the intermediate transfer belt 41 to the paper S without shifting. Further, when the paper S passes through the secondary transfer nip Nt-fixing nip Nf section R2, it is possible to prevent the occurrence of wrinkles.

Further, since the actual transfer time of the paper S is detected, the transfer speed can be adjusted more accurately than when the rotation speed of the transfer means is measured by an encoder or the like to calculate the transfer time of the paper S. can.

In the present embodiment, the rotation speed and applied voltage of the transfer motor 73 are adjusted based on the current fluctuation of the resist motor 87 in the resist nip Nr, and the fixing motor 55 is adjusted based on the current fluctuation of the transfer motor 73 in the secondary transfer nip Nt. The rotation speed and applied voltage were adjusted. However, the rotation speed and the applied voltage of the fixing motor 55 may be adjusted in addition to the rotation speed and the applied voltage of the transfer motor 73 based on the current fluctuation of the resist motor 87 in the resist nip Nr. Specifically, when the transfer time is shorter than the estimated time (Ts), the control unit 101 increases the rotation speed of the fixing motor 55 to be higher than the reference rotation speed, and the transfer time is longer than the estimated time (Ts). If it is long, the rotation speed of the fixing motor 55 is made smaller than the reference rotation speed. Further, when the current fluctuation value is larger than the assumed value (Is), the voltage applied to the fixing motor 55 is made higher than the reference applied voltage, and when the current fluctuation value is smaller than the assumed value (Is), the fixing is performed. The applied voltage to the motor 55 is made lower than the reference applied voltage.

Further, only one of the transfer motor 73 and the fixing motor 55 may be adjusted. Further, the user may be able to select whether to adjust the transfer motor 73 or the fixing motor 55.

In the present embodiment, the resist roller pair 81 is described as the first transfer member, the secondary transfer roller 71 and the intermediate transfer belt 41 are described as the second transfer member, and the fixing device 9 is described as the third transfer member. Not exclusively.

Further, the above description of the embodiment of the present invention describes a preferred embodiment of the present invention, and thus may be subject to various technically preferable limitations, but the technical scope of the present invention. Is not limited to these aspects unless otherwise specified to limit the present invention.

1 Image forming device 9 Fixing device (3rd transport member)
41 Intermediate transfer belt (second transport member)
55 Fixing motor (3rd motor)
71 Secondary transfer roller (second transport member)
73 Transfer motor (second motor)
75 Second current measurement circuit (second current measurement means)
81 Resist roller pair (first transport member)
87 Resist motor (1st motor)
89 1st current measuring circuit (1st current measuring means)
91 1st paper detection sensor 93 2nd paper detection sensor 101 Control unit

Claims (5)

A first transport member and a second transport member that are arranged on the upstream side and the downstream side in the paper transport direction and that sandwich and transport the paper on both sides.
The first motor that drives the first transport member and
The second motor that drives the second transport member and
The first current measuring means for measuring the load current of the first motor, and
A first paper detection sensor arranged between the first transport member and the second transport member,
The current fluctuation of the first motor is detected from the measurement result of the first current measuring means, and the paper transport time from the current fluctuation detection time to the time when the paper is detected by the first paper detection sensor and the first motor. An image forming apparatus including a control unit that adjusts the rotation speed of the second motor and the voltage applied to the second motor based on the current fluctuation value of the above. The control unit
When the transport time is shorter than the estimated time, the rotation speed of the second motor is made larger than the reference rotation speed, and when the transport time is longer than the estimated time, the rotation speed of the second motor is set. It is less than the reference rotation speed and
When the current fluctuation value is larger than the assumed value, the voltage applied to the second motor is made higher than the reference applied voltage, and when the current fluctuation value is smaller than the assumed value, the second motor is reached. The image forming apparatus according to claim 1, wherein the applied voltage of the above is made lower than the applied voltage of the reference. A third transport member that is arranged on the downstream side of the second transport member in the transport direction and that sandwiches and transports the paper together with the second transport member.
A third motor that drives the third transport member and
A second current measuring means for measuring the load current of the second motor,
A second paper detection sensor arranged between the second transport member and the third transport member is further provided.
The control unit detects the current fluctuation of the second motor from the load current measured by the second current measuring means, and the paper from the current fluctuation detection time to the time when the paper is detected by the second paper detection sensor. The invention according to claim 1 or 2, wherein the rotation speed of the third motor and the voltage applied to the third motor are adjusted based on the transport time of the second motor and the current fluctuation value of the second motor. Image forming device. A third transport member that is arranged downstream of the second transport member in the transport direction and that sandwiches and transports the paper together with the second transport member.
A third motor for driving the third transport member is further provided.
The control unit detects the current fluctuation of the first motor from the measurement result of the first current measuring means, and the paper transport time from the current fluctuation detection time to the time when the paper is detected by the first paper detection sensor. And the current fluctuation value of the first motor, the rotation speed of the second motor and the applied voltage to the second motor, and the rotation speed of the third motor and the applied voltage to the third motor. The image forming apparatus according to claim 1 or 2, wherein the image forming apparatus is adjusted. The first transfer member is a pair of resist rollers for adjusting the transfer timing of paper.
The second transport member is an intermediate transfer belt on which a toner image is supported and a transfer roller that transfers the toner image from the intermediate transfer belt to paper.
The image forming apparatus according to claim 3 or 4, wherein the third conveying member is a fixing device for fixing a toner image on paper.

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