JP2018025755A - Contact/separation system, image formation apparatus and contact/separation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a contact/separation system which can detect the load fluctuation at the contact/separation between a roller and a belt at a low cost without installing a sensor detecting the load fluctuation, execute feedback control and sufficiently suppress shock jitter by optimizing the contact/separation speed of rollers.SOLUTION: In a secondary transfer contact/separation system using a DC motor 3 applied in an image formation apparatus, a motor control circuit (not illustrated) detects the load fluctuation indicating the impact at the moment when an intermediate transfer belt 7 separates or contacts via a sheet 8 between an intermediate transfer repulsive roller 5 and a secondary transfer roller 6 facing each other in a contact/separation mechanism with feedback control, the rotational speed and rotation angle of a motor 3 are adjusted in accordance with the detected load fluctuation, the rotation position of an eccentric cam 9 fixed to a rotational shaft 11 on the end of the roller 5 and the contact/separation speed between the roller 6 and the belt 7 are properly changed, and shock jitter is suppressed by alleviating the impact with reduction in the rotational speed of the motor 3 at the time when the roller 6 and the belt 7 separate or contact from/with each other.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a contact / separation system, an image forming apparatus, and a contact / separation method.

  2. Description of the Related Art Conventionally, in an image forming apparatus, a contact / separation mechanism that separates or abuts a roller and a belt is provided in a transfer device in order to reduce a shock jitter in which the speed of a roller or a belt greatly decreases for a moment. A stepping motor is used as a driving motor for driving the contact / separation mechanism. The contact / separation mechanism provided in the transfer device may be called a secondary transfer contact / separation mechanism. Incidentally, the roller that generates shock jitter in this case is a secondary transfer roller (the side opposite to the contact side), and the belt is an intermediate transfer belt.

  As a well-known technique equipped with such a secondary transfer contact / separation mechanism, a “transfer device capable of reducing shock when the secondary transfer roller comes into contact with the intermediate transfer belt and suppressing shock jitter” is provided. Image forming apparatus "(see Patent Document 1).

  The technique according to Patent Document 1 described above aims to reduce shock when the secondary transfer roller comes into contact with the intermediate transfer belt and suppress shock jitter. Therefore, the transfer device is provided with a secondary transfer contact / separation mechanism that uses a stepping motor to contact or separate the secondary transfer roller and the intermediate transfer belt (also generally referred to as contact / separation). is there.

  However, when a stepping motor is used for the secondary transfer contact / separation mechanism, feedback control cannot be performed, and load fluctuations during contact / separation between the secondary transfer roller and the intermediate transfer roller cannot be detected. For this reason, it is difficult to optimize the contact / separation speed between the rollers. As a result, the rotation speed cannot be changed at the moment when the rollers come in contact with each other, and the impact (load fluctuation) at the moment of contact and separation increases, resulting in still shock jitter. There is a problem that it cannot be sufficiently suppressed.

  Incidentally, the drive device applicable to the image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 2012-118200 aims to perform drive control of a drive source easily and accurately. Specifically, the load variation point is determined based on the load characteristic indicating the magnitude of the load, and the position is set as the home position. However, in the case of this configuration, there is a problem that an increase in cost due to the provision of a dedicated sensor for detecting a load change cannot be avoided.

  The present invention has been made to solve such problems, and technical problems thereof are summarized below. In the contact / separation system, it is possible to detect the load change at the time of contact / separation between the roller and the belt at low cost without providing a sensor for detecting the load change, and the feedback control can be executed to optimize the contact / separation speed between the rollers. It is to suppress sufficiently.

  In order to solve the above technical problem, according to one aspect of the present invention, a first roller that contacts the belt, a second roller that faces the first roller, and a second sheet that is conveyed through the conveyed sheet are provided. A contact / separation system comprising: a contact / separation system that contacts or separates the roller of the first roller, wherein the contact / separation mechanism is attached to an end of a rotation shaft of the first roller and rotates eccentrically using a motor as power. A cam and a control means for controlling the motor, wherein the belt is brought into contact with or separated from the second roller via a sheet conveyed by the rotation of the eccentric cam; The rotation speed of the motor is reduced at the timing when the belt is separated or abutted between the first roller and the second roller.

  According to the present invention, according to the above configuration or processing process, it is possible to detect the load fluctuation at the time of contact and separation between the roller and the belt at a low cost without providing a sensor for detecting the load fluctuation, and it is possible to perform feedback control and to connect the rollers. It will be possible to optimize the separation speed and sufficiently suppress shock jitter. Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

FIG. 2 is a schematic diagram illustrating an extracted main configuration of an image forming apparatus to which a secondary transfer contact / separation mechanism according to Embodiment 1 of the present invention is applied. FIG. 2 is a perspective view illustrating a schematic configuration of a secondary transfer contact / separation mechanism provided in the transfer device of the image forming apparatus illustrated in FIG. 1. (A) is a diagram regarding the contracted state of the opposing bearing when the intermediate transfer belt and the secondary transfer roller are separated from each other, and (b) is a diagram regarding the rotational position of the eccentric cam when the intermediate transfer belt and the secondary transfer roller are separated from each other. is there. (C) is a diagram relating to the extension state of the opposing bearing when the intermediate transfer belt and the secondary transfer roller are in contact, and (d) is related to the rotational position of the eccentric cam when the intermediate transfer belt and the secondary transfer roller are in contact. FIG. FIG. 3 is a schematic diagram illustrating a rotational position detection mechanism attached to a shaft of a secondary transfer roller of the secondary transfer contact / separation mechanism described in FIG. 2. (A) is a figure regarding the state at the time of contact | abutting to the intermediate transfer belt of a secondary transfer contact / separation mechanism, (b) is a figure regarding the state at the time of separation | spacing to the intermediate transfer belt of a secondary transfer contact / separation mechanism. FIG. 2 is a diagram illustrating an example of operation processing in a secondary transfer contact / separation mechanism when a DC motor is driven by a control unit provided in the image forming apparatus illustrated in FIG. 1. (A) is the flowchart which showed an example of the control processing to a secondary transfer contact-and-separation mechanism. (B) is a diagram showing the timing for determining the stop position of the eccentric cam during separation of the secondary transfer contact / separation mechanism in relation to the voltage with respect to time. FIG. 7 is a diagram illustrating another example of operation processing in the secondary transfer contact / separation mechanism in which a DC motor is driven by a control unit provided in the image forming apparatus illustrated in FIG. 1. (A) is the flowchart which showed the other example of the control processing to a secondary transfer contact-and-separation mechanism. (B) is a flowchart showing details of test drive of the secondary transfer contact / separation mechanism at an initial stage in the control process of (a). It is the figure which illustrated the DC motor control circuit for performing the feedback control of the DC motor included in the control processing of FIG. 4 (a) and FIG. 5 (a). It is the figure shown in order to demonstrate the criteria at the time of detecting the load fluctuation concerning the DC motor included in the control processing of Drawing 4 (a) and Drawing 5 (a) by applying feedback control. (A) is a characteristic diagram of a fluctuation waveform with respect to time of the DC motor, and (b) is a diagram showing threshold determination and area determination in the local part of (a). A case where a conventional stepping motor is used as an example of control for determining the rotational position of the eccentric cam and the separation speed between the secondary transfer roller and the intermediate transfer belt based on the load fluctuation included in the control process of FIG. It is a figure demonstrated in contrast. Specifically, the characteristic diagram is shown in relation to the distance between the rollers related to the intermediate transfer repulsive roller and the secondary transfer roller with respect to time. When a conventional stepping motor is used as another example of the control of determining the rotational position of the eccentric cam based on the load variation included in the control process of FIG. 5A and the separation speed between the secondary transfer roller and the intermediate transfer belt It is a figure explaining by contrasting. Specifically, a characteristic diagram is shown in relation to voltage with respect to time. FIG. 3 is a perspective view showing an external configuration of a DC motor provided in the secondary transfer contact / separation mechanism shown in FIG. 2. It is the functional block diagram which showed the detailed structure of the drive device with respect to DC motor shown in FIG. 10, and a load fluctuation estimation apparatus. FIG. 11 is a diagram showing a relationship of a distance obtained by subtracting a sum of roller radii from a distance between roller centers with respect to a rotation angle of an eccentric cam during control of the secondary transfer contact / separation mechanism by the DC motor shown in FIG. 10. FIG. 6 is a schematic view showing a main part of a secondary transfer contact / separation mechanism according to Embodiment 2 of the present invention in comparison with the case of Embodiment 1. (A) is a figure which shows the home position at the time of separation | spacing of the eccentric cam and secondary transfer roller in the case of Example 1. FIG. FIG. 6B is a diagram illustrating a home position when the eccentric cam and the secondary transfer roller according to an example of the second embodiment are separated from each other, and a load fluctuation detection position when determining the home position. FIG. 6C is a diagram illustrating a home position when the eccentric cam and the secondary transfer roller according to another example of Embodiment 2 are separated from each other, and a load fluctuation detection position when determining the home position. FIG. 6D is a diagram illustrating a home position when an eccentric cam and a secondary transfer roller according to another example of Embodiment 2 are separated from each other, and a load fluctuation detection position when determining the home position. 6 is a flowchart illustrating a control process for a secondary transfer contact / separation mechanism according to a second embodiment in which a DC motor is driven by a control unit provided in the image forming apparatus illustrated in FIG. 1. It is the figure shown in order to demonstrate the criteria when applying the feedback control and detecting the load fluctuation | variation concerning a DC motor at the time of applying the eccentric cam shown in FIG.13 (b), and the fluctuation | variation at the time of a cam collision. (A) is a characteristic diagram of a fluctuation waveform with respect to time of the DC motor, and (b) is a diagram showing threshold determination and area determination in the local part of (a). The figure shown in order to demonstrate the criteria (threshold judgment and area judgment) at the time of detecting the fluctuation | variation at the time of the cam collision which concerns on the DC motor at the time of applying the eccentric cam shown in FIG.13 (c) using feedback control It is. In order to explain the position error calculation through the cam collision variation by applying the feedback control related to the DC motor when the eccentric cam shown in FIG. 13 (d) is applied, the characteristics of the rotation angle with respect to the time of the eccentric cam are shown. It is a figure. A comparison between the driving time of the DC motor and the separation distance at the time of separation between the secondary transfer contact / separation mechanism according to the first embodiment and the secondary transfer contact / separation mechanism according to the second embodiment It is the figure shown by the relationship of the distance which reduced the sum. (A) is the figure which showed the case where the home position of the secondary transfer contact-and-separation mechanism based on Example 1 slips. FIG. 7B is a diagram illustrating a case where the home position of the secondary transfer contact / separation mechanism according to the second embodiment is determined at one point in comparison with the secondary transfer contact / separation mechanism according to the first embodiment.

  Hereinafter, the contact / separation mechanism, the contact / separation system, the image forming apparatus having the contact / separation system, and the contact / separation method of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic diagram showing an extracted main configuration of an image forming apparatus to which a secondary transfer contact / separation mechanism according to Embodiment 1 of the present invention is applied.

  Referring to FIG. 1, the image forming apparatus is of a digital multifunction peripheral (MFP) specification in which a plurality of functions such as a printer, a copier, a scanner, and a facsimile are combined in one casing. Specifically, an intermediate transfer unit including the transfer device 1 around the secondary transfer roller 6 is shown.

  The intermediate transfer unit is a photosensitive member that is four developing rotators corresponding to toners of black (K), cyan (C), magenta (M), and yellow (Y) in order to obtain a color image. A four-tandem color transfer device 1 in which drums are arranged side by side on the same plane is provided. Further, a primary transfer roller 2 is provided that offsets the toner image formed by the developing unit on these photosensitive drums onto the outer surface of the intermediate transfer belt 7. Further, in the intermediate transfer portion, the belt 4 is laid over the respective rotation shafts, and the rotation drive of the DC motor 3 is transmitted to the intermediate transfer belt 7 on the intermediate transfer belt 7 by the driven intermediate transfer repulsive roller 5 and the secondary transfer roller 6. The transferred toner image is secondarily transferred to a recording medium. Here, the recording medium is a general term for sheets including paper, coated paper, label paper, an OHP sheet (overhead projector sheet), a film, and the like. In the following, the recording medium is regarded as a sheet. Here, the DC motor 3 and the intermediate transfer repulsive roller 5 are included in a secondary transfer contact / separation mechanism that contacts or separates the secondary transfer roller 6 and the intermediate transfer belt 7 as described later.

  In the secondary transfer portion described above, it is required to keep the speed of the intermediate transfer belt 7 constant. However, a torque load is generated on the intermediate transfer belt 7 due to impact when the sheet enters or leaves the contact portion (nip portion) between the intermediate transfer repulsive roller 5 and the secondary transfer roller 6 for secondary transfer. . As a result, a speed difference may occur between each photosensitive drum and the intermediate transfer belt 7. The speed difference at this time may cause horizontal stripe-like density unevenness in the printed image on the sheet, which may cause printing failure. A phenomenon in which the speed of the secondary transfer roller 6 and the intermediate transfer belt 7 that cause such an abnormal image is greatly reduced for a moment is called shock jitter. Therefore, a secondary transfer contact / separation mechanism is provided to reduce shock jitter.

  FIG. 2 is a perspective view showing a schematic configuration of the secondary transfer contact / separation mechanism provided in the transfer device 1 of the image forming apparatus described above. 2A is a diagram relating to the contracted state of the opposing bearing 10 when the intermediate transfer belt 7 and the secondary transfer roller 6 are separated from each other, and FIG. 2B is a diagram when the intermediate transfer belt 7 and the secondary transfer roller 6 are separated from each other. It is a figure regarding the rotational position of the eccentric cam 9. FIG. 2C is a diagram relating to the extension state of the opposing bearing 10 when the intermediate transfer belt 7 and the secondary transfer roller 6 are in contact with each other, and FIG. 2D is a diagram illustrating the contact between the intermediate transfer belt 7 and the secondary transfer roller 6. It is a figure regarding the rotational position of the eccentric cam 9 at the time of contact.

  Referring to FIG. 2A, in the secondary transfer contact / separation mechanism, when the sheet 8 is first removed, control means (generally a printer unit controller having a CPU function) bears shortly before the sheet 8 is removed. ) To drive the DC motor 3. Following this, the belt 4 and the rotating shaft 11 of the intermediate transfer repulsive roller 5 rotate, and the eccentric cam 9 fixed to the rotating shaft 11 also rotates. At this time, the eccentric cam 9 pushes down the opposing bearing 10 by the spring member, and the secondary transfer roller 6 and the intermediate transfer belt 7 (the same may be considered to include the intermediate transfer repulsive roller 5). Separate. At this time, the rotational position of the eccentric cam 9 is in a state where the major axis rises and contacts the end of the secondary transfer roller 6 as shown in FIG. Thereby, the impact at the time of the sheet | seat 8 pulling out can be reduced.

  Referring to FIG. 2C, in the secondary transfer contact / separation mechanism, when the sheet 8 enters, the eccentric cam 9 rotates a little after the sheet enters in the same manner as described above, this time the eccentric cam. 9 separates from the opposed bearing 10 and the secondary transfer roller 6 and the intermediate transfer belt 7 come into contact with each other. At this time, the rotational position of the eccentric cam 9 is in a state where the major axis rises and is separated from the end of the secondary transfer roller 6 as shown in FIG. Thereby, the impact which arises when the sheet | seat 8 rushes can be reduced. That is, in this secondary transfer contact / separation mechanism, the intermediate transfer belt 7 is brought into contact with or separated from the secondary transfer roller 6 facing the intermediate transfer repulsive roller 5 with which the intermediate transfer belt 7 comes into contact via the conveyed sheet 8. Has basic functions. Here, the intermediate transfer repulsive roller 5 may be regarded as a first roller, and the secondary transfer roller 6 may be regarded as a second roller. An eccentric cam 9 attached to the end of the rotary shaft 11 of the intermediate transfer repulsive roller 5 rotates with the DC motor 3 controlled by the control means as power. The eccentric cam 9 is normally attached to both end portions of the rotating shaft 11, but can be configured to be attached to one end portion of the rotating shaft 11. By rotating the eccentric cam 9, the intermediate transfer belt 7 is brought into contact with or separated from the secondary transfer roller 6 via the sheet 8 being conveyed.

  According to the secondary transfer contact / separation mechanism, it is possible to reduce shock jitter due to an impact when the sheet enters or exits the contact portion (nip portion) between the intermediate transfer repulsive roller 5 and the secondary transfer roller 6. it can. However, when the separated secondary transfer roller 6 and the intermediate transfer belt 7 come into contact with or separate from each other, an impact is generated as a new shock jitter source, which may adversely deteriorate the shock jitter. As a countermeasure, the secondary transfer contact / separation mechanism according to the first embodiment uses a DC motor 3 that can feedback-control the rotation speed and the rotation angle by a control unit for driving. Therefore, in the secondary transfer contact / separation mechanism, the rotational speed and rotational angle of the DC motor 3 are adjusted by feedback control by the control means, and the rotational position of the eccentric cam 9, and the opposing secondary transfer roller 6 and intermediate transfer repulsive roller are adjusted. The contact / separation speed with respect to the intermediate transfer belt 7 between the five is changed. The control means decelerates the rotational speed of the DC motor 3 at the timing when the intermediate transfer belt 7 is separated or abutted between the opposing intermediate transfer repulsive roller 5 and secondary transfer roller 6. As a result, an impact when the intermediate transfer belt 7 is separated or abutted between the opposing secondary transfer roller 6 and the intermediate transfer repulsive roller 5 can be buffered, thereby suppressing shock jitter. Incidentally, the combined structure of the secondary transfer contact / separation mechanism and the control means here can be regarded as a secondary transfer contact / separation system.

  FIG. 3 is a schematic view showing a rotational position detection mechanism attached to the shaft of the secondary transfer roller 6 of the secondary transfer contact / separation mechanism described above. FIG. 3A is a diagram relating to a state when the secondary transfer contact / separation mechanism is in contact with the intermediate transfer belt 7, and FIG. 3B is a state when the secondary transfer contact / separation mechanism is separated from the intermediate transfer belt 7. FIG.

  Referring to FIGS. 3A and 3B, the rotational position detection mechanism has a filler 17 attached to one end of the shaft of the secondary transfer roller 6 and a position where the filler 17 advances and retreats during rotation. The light-emitting element 18a and the light-receiving element 18b of the optical element provided to face each other. 3A corresponds to a state in which the intermediate transfer belt 7 is in contact between the secondary transfer roller 6 and the intermediate transfer repulsive roller 5. FIG. In this case, since the irradiation light from the light emitting element 18a is blocked by the semi-cylindrical filler 17 body and is not detected by the light receiving element 18b, the control means can determine that the filler 17 is present. 3B corresponds to a state where the intermediate transfer belt 7 is separated between the secondary transfer roller 6 and the intermediate transfer repulsive roller 5. FIG. In this case, since the light emitted from the light emitting element 18a is detected by the light receiving element 18b without being blocked by the semi-cylindrical filler 17, the control means can determine that the filler 17 is absent. Therefore, the control means determines the stop position (rotation position) of the eccentric cam 9 at a predetermined timing after detecting the presence or absence of the filler 17.

  FIG. 4 is a diagram illustrating an example of operation processing in the secondary transfer contact / separation mechanism when the DC motor 3 is driven by the control unit provided in the above-described image forming apparatus. FIG. 4A is a flowchart showing an example of control processing for the secondary transfer contact / separation mechanism. FIG. 4B is a diagram showing the timing of determining the stop position (rotation position) of the eccentric cam 9 when the secondary transfer contact / separation mechanism is separated in relation to the voltage [V] with respect to time [ms].

  Referring to FIG. 4 (a), an example of the control process for the secondary transfer contact / separation mechanism is intended to alleviate the impact at the time of contact and separation between the intermediate transfer belt 7 and the secondary transfer roller 6. To do. For this reason, first, the secondary transfer contact / separation mechanism is test-driven while the sheet is passing, and the intermediate transfer belt 7 and the secondary transfer roller 6 are separated and contacted (step S1). Thereafter, a load change related to the DC motor 3 at the moment when the secondary transfer roller 6 and the intermediate transfer belt 7 are separated or contacted is detected using feedback control (step S2). Incidentally, the load fluctuation of the feedback value obtained from the feedback control here corresponds to, for example, a current value, speed error, position error, pulse width modulation (PWM), torque, and the like. Further, the stop position (rotation position) of the eccentric cam 9 is determined based on the load fluctuation detected by the DC motor 3 at this time (step S3). Incidentally, the rotation direction of the eccentric cam 9 at this time may be either forward rotation operation or reverse rotation operation. The physical quantity related to the eccentric cam 9 contributes to the separated home position.

  Referring to FIG. 4 (b), in the control to change from the contact state at time t0 to the separated state at time t1, load fluctuation at the time of separation at time t1 is detected, and N pulses [pulsu] are detected from the detection timing. The eccentric cam 9 is stopped at the home position in the separated state at time t2. Incidentally, at time t1, the distance between the secondary transfer roller 6 and the intermediate transfer repulsive roller 5 is 0 [mm], but becomes a load fluctuation detection position. The eccentric cam 9 is stopped after a predetermined number of pulses N are driven from this load fluctuation detection position.

  FIG. 5 is a diagram illustrating another example of the operation process in the secondary transfer contact / separation mechanism in which the DC motor 3 is driven by the control unit provided in the above-described image forming apparatus. FIG. 5A is a flowchart showing another example of the control process for the secondary transfer contact / separation mechanism. FIG. 5B is a flowchart showing details of the test drive of the secondary transfer contact / separation mechanism at the initial stage in the control processing of FIG.

  Referring to FIG. 5A, in another example of the control process for the secondary transfer contact / separation mechanism, the purpose is to alleviate the impact at the time of contact and separation between the intermediate transfer belt 7 and the secondary transfer roller 6. And For this reason, first, the secondary transfer contact / separation mechanism is test-driven while the sheet is passing, and the intermediate transfer belt 7 and the secondary transfer roller 6 are separated and contacted (step S1). Thereafter, a load change related to the DC motor 3 at the moment when the secondary transfer roller 6 and the intermediate transfer belt 7 are separated or contacted is detected using feedback control (step S2). Incidentally, the load fluctuation of the feedback value obtained from the feedback control also corresponds to, for example, a current value, a speed error, a position error, pulse width modulation (PWM), torque, and the like. Further, the rotational position (stop position), separation, and contact speed (speed) of the eccentric cam 9 are determined based on the load fluctuation detected by the DC motor 3 at this time (step S3). The physical quantity related to the eccentric cam 9 contributes to the reduction of shock jitter.

  Referring to FIG. 5B, in the test drive of the secondary transfer contact / separation mechanism, when the start signal is acquired, the DC motor 3 is driven to separate the secondary transfer roller 6 from the abutting intermediate transfer belt 7. (Home position operation) (step S1-1) is performed. Next, after the process of driving the intermediate transfer belt 7 (step S1-2), the process of driving the secondary transfer roller 6 (step S1-3) is performed. Further, the DC motor 3 is driven and the eccentric cam 9 is rotated so that the intermediate transfer belt 7 and the secondary transfer roller 6 are separated and brought into contact with each other (a separation and contact detection position is acquired) (step S1-4). ) Process. In this way, the secondary transfer contact / separation mechanism is test-driven at the time of startup, at the time of return from sleep, before and after transfer, and the like.

  FIG. 6 is a diagram illustrating a DC motor control circuit for performing feedback control of the DC motor 3 included in the control processes of FIGS. 4A and 5A described above.

  Referring to FIG. 6, the DC motor control circuit includes a CPU 101 as a central processing unit including a voltage control (CTL) unit 102 that performs motor control processing and a torque estimation processing unit 108 that performs torque estimation processing. . In addition, a motor driver 103 that receives a control voltage Vctl from the voltage control (CTL) unit 102 and performs a switching process for driving the DC motor 3, and a DC motor 3 that is driven by the motor driver 103 and outputs a motor torque T. And comprising. Further, an adder 104 for adding the motor torque T from the DC motor 3 and the external load torque τ, and a mechanical circuit for detecting and outputting the motor rotational speed ωdet from the added value of the motor torque T and the load torque τ. 105. Further, an integration (1 / s) circuit 106 that integrates (1 / s) the motor rotational speed ωdet and outputs the motor position xdet is provided. In addition, a current detection circuit 107 that outputs a current detection signal, which is a current detected based on a voltage signal between shunt resistors in the motor driver 103, to the torque estimation processing unit 108 is provided.

  Among these, the voltage control (CTL) unit 102 receives the target speed (ωtgt) and the target position (xtgt) from the outside, and from the mechanical circuit 105 to the motor rotational speed ωdet and from the integration (1 / s) circuit 106. The motor position xdet is input. Therefore, the voltage control (CTL) unit 102 performs a motor control calculation process based on these pieces of information, and outputs a control voltage Vctl in a pulse width modulation (PWM) format to the motor driver 103 to perform voltage control. Specifically, in the voltage control (CTL) unit 102, speed feedback control, position feedback control, speed feedforward control, position feedforward control, and the like are performed. In addition to performing the switching process described above, the motor driver 103 can detect the combined current with the voltage across the shunt resistor. The mechanical circuit 105 can be exemplified by a case where a two-phase encoder or the like is applied as a measurement sensor. The torque estimation processing unit 108 receives a current detection signal from the current detection circuit 107 by an analog A / D converter (ADC) and performs torque estimation processing. At this time, the estimation formula is changed according to the motor rotation speed ωdet, and the target speed ωt or the motor rotation speed ωdet is used as the rotation speed information. The CPU 101 can be regarded as a control device that functions as the control means described above. The CPU 101 has a function of detecting separation or contact based on a load fluctuation of a feedback value obtained from feedback control of an instantaneous timing at the time of separation or contact by the secondary transfer contact / separation mechanism. A configuration in which the secondary transfer contact / separation mechanism and the CPU 101 as a control device are combined may be referred to as a contact / separation mechanism system as described above. That is, the image forming apparatus shown in FIG. 1 includes such a contact / separation mechanism system.

  FIG. 7 is a diagram shown for explaining a determination criterion when detecting a load variation related to the DC motor 3 included in the control processing of FIGS. 4A and 5A described above using feedback control. It is. FIG. 7A is a characteristic diagram of a fluctuation waveform with respect to time Time [s] of the DC motor 3, and FIG. 7B is a diagram showing threshold determination and area determination in the local part of FIG. 7A.

  Referring to FIG. 7A, here, the fluctuation waveform obtained by the feedback control by the DC motor control circuit shown in FIG. 6 is shown. The local area surrounded by a circle in the fluctuation waveform is the timing of the position where the intermediate transfer belt 7 and the secondary transfer roller 6 are separated or in contact with each other, and it can be seen that a large fluctuation occurs at that time. As the feedback value obtained from the feedback control by the CPU 101 of the DC motor control circuit shown in FIG. 6, such fluctuations are represented by physical values (current value, speed error, position error, pulse width modulation (PWM), torque, etc. ( Hereinafter, each value is detected).

  As a criterion for detecting load fluctuation, A. of FIG. In the threshold value determination, a case where it is determined that the separation or contact is detected when the load fluctuation of each value detected by the feedback control exceeds a predetermined threshold value regardless of positive or negative can be exemplified. In addition, B. of FIG. In the area determination (certain specific range), it is determined that separation or contact is detected when the load fluctuation area of the specific range of each value detected by the CPU 101 exceeds a predetermined threshold. Specifically, when the average value of all data of each value detected by feedback control is set to 0, it is separated when the specific range where the load fluctuation is large and the area surrounded by 0 exceeds the set threshold value. Or it determines as detection of contact.

  FIG. 8 shows an example of conventional control for determining the rotational position of the eccentric cam 9 and the separation speed between the secondary transfer roller 6 and the intermediate transfer belt 7 based on the load variation included in the control process of FIG. It is a figure explaining by contrast the case where a stepping motor is used. Specifically, the characteristic diagram is shown in relation to the distance [mm] between the rollers related to the intermediate transfer repulsive roller 5 and the secondary transfer roller 6 with respect to time [ms].

  Referring to FIG. 8, here, the control after detecting the load fluctuation by the feedback control in the DC motor control circuit described with reference to FIGS. 6 and 7 will be described focusing on the case of separation. In the case of the control using the conventional stepping motor indicated by the dotted line, the intermediate transfer repulsive roller 5 and the second transfer roller 5 and the second transfer roller 5 are only at a constant speed from the separation start timing f in the contact state to the contact end timing g in the separation state. The next transfer roller 6 cannot be separated. The constant speed corresponds to the slope of the interval from timing f to g.

  On the other hand, when the DC motor 3 indicated by the solid line is used, the timing c at the moment when the secondary transfer roller 6 and the intermediate transfer belt 7 are separated by the secondary transfer contact / separation mechanism is fed back by the feedback control described above. It can be detected based on the load fluctuation of the value. Therefore, in the control related to the CPU 101 of the DC motor control circuit, the timing c at the moment when it is determined that the separation is detected is stored in a storage unit such as a memory. Further, attention is paid to the speed in a period within a predetermined time before and after the timing c at the time of separation by the secondary transfer contact / separation mechanism. Incidentally, the period within the predetermined time here corresponds to the section of timing b to d, and the speed corresponds to the slope in the section of timing b to d. Further, this speed is slower than the speed at which the contact pressure (nip pressure) between the intermediate transfer belt 7 and the secondary transfer roller 6 is decreased from the state where the intermediate transfer belt 7 is in contact with the secondary transfer roller 6. Then, the secondary transfer contact / separation mechanism is driven. At the same time, after the intermediate transfer belt 7 and the secondary transfer roller 6 are separated from each other, the secondary transfer contact / separation mechanism is driven so as to be slower than the speed at which the distance is increased. Incidentally, the speed at which the contact pressure is reduced here corresponds to the slope of the section of timing a to b, and the speed at the time of increasing the distance corresponds to the slope of the section of timing de. That is, here, in the separation operation by the secondary transfer contact / separation mechanism by adjusting the rotation speed and rotation angle of the DC motor 3 by the DC motor control circuit according to the result of detecting the load fluctuation based on the feedback value subjected to feedback control. Buffer. Thereby, a shock jitter can be suppressed effectively.

  Also, the timing at the moment when the secondary transfer roller 6 and the intermediate transfer belt 7 are brought into contact with each other by the secondary transfer contact / separation mechanism can be detected by feedback control based on the load fluctuation of the feedback value. Therefore, in the control related to the CPU 101 of the DC motor control circuit, the timing of the moment when it is determined that the contact is detected is similarly stored in the storage unit. Further, attention is paid to the speed in a period within a predetermined time before and after the moment of contact by the secondary transfer contact / separation mechanism. Further, the secondary transfer is performed so that the speed is lower than the speed when the intermediate transfer belt 7 is moved toward the secondary transfer roller 6 from the state where the intermediate transfer belt 7 is separated from the secondary transfer roller 6. Drive the contact / separation mechanism. At the same time, the secondary transfer contact / separation mechanism is driven so as to be slower than the speed at which the intermediate transfer belt 7 contacts the secondary transfer roller 6 and then reaches a predetermined contact pressure (nip pressure). That is, here, the contact operation by the secondary transfer contact / separation mechanism by adjusting the rotation speed and rotation angle of the DC motor 3 by the DC motor control circuit in accordance with the result of detecting the load fluctuation based on the feedback value subjected to feedback control. At the time, shock is buffered. Thereby, a shock jitter can be suppressed effectively.

  FIG. 9 shows another example of conventional control for determining the rotational position of the eccentric cam 9 and the separation speed between the secondary transfer roller 6 and the intermediate transfer belt 7 based on the load variation included in the control process of FIG. It is a figure explaining by contrasting the case where this stepping motor is used. Specifically, a characteristic diagram is shown in relation to voltage [V] with respect to time [ms].

  Referring to FIG. 9, here, the control after detecting the load variation by the feedback control in the DC motor control circuit described with reference to FIG. 6 and FIG. To do. In the case of control using the conventional stepping motor indicated by the dotted line, a pulse can be given only at a constant interval from the separation start timing h in the contact state to the contact end timing l in the separation state. Here, the constant interval corresponds to a pulse waveform in a section of timings h to l.

  On the other hand, when the DC motor 3 indicated by the solid line is used, the timing j at the moment when the secondary transfer roller 6 and the intermediate transfer belt 7 are separated by the secondary transfer contact / separation mechanism is fed back by the feedback control described above. It can be detected based on the load fluctuation of the value. Here, the timing j indicates that the distance between the rollers related to the intermediate transfer repulsive roller 5 and the secondary transfer roller 6 is 0 mm. Therefore, in the control related to the CPU 101 of the DC motor control circuit, the timing j at the moment when it is determined that the separation is detected is stored in a storage means such as a memory. Further, attention is focused on the pulse interval in the pulse section P [pulse] within a predetermined number of pulses before and after the timing j at the moment of separation by the secondary transfer contact / separation mechanism (here, three pulses correspond). The pulse interval here corresponds to the pulse waveform in the section of timings i to k. Further, with respect to this pulse interval, the pulse interval when the contact pressure (nip pressure) between the intermediate transfer belt 7 and the secondary transfer roller 6 is decreased from the state where the intermediate transfer belt 7 is in contact with the secondary transfer roller 6 is compared with the pulse interval. The secondary transfer contact / separation mechanism is driven so as to widen. At the same time, the secondary transfer contact / separation mechanism is driven so as to be wider than the pulse interval when the distance is increased after the intermediate transfer belt 7 and the secondary transfer roller 6 are separated. Here, the pulse interval when reducing the contact pressure corresponds to the pulse waveform in the interval of timings h to i, and the pulse interval when increasing the distance corresponds to the pulse waveform in the interval of timings k to l. That is, also in the separation operation by the secondary transfer contact / separation mechanism by adjusting the rotation speed and rotation angle of the DC motor 3 by the DC motor control circuit according to the result of detecting the load fluctuation based on the feedback value subjected to feedback control. Shock is shock-absorbed. Thereby, a shock jitter can be suppressed effectively.

  Also, the timing at the moment when the secondary transfer roller 6 and the intermediate transfer belt 7 are brought into contact with each other by the secondary transfer contact / separation mechanism can be detected by feedback control based on the load fluctuation of the feedback value. Therefore, in the control related to the CPU 101 of the DC motor control circuit, the timing of the moment when it is determined that the contact is detected is similarly stored in the storage unit. Further, attention is paid to the pulse interval in a pulse section within a predetermined number of pulses before and after the moment of contact by the secondary transfer contact / separation mechanism. Further, the pulse interval is increased so that the intermediate transfer belt 7 becomes wider than the pulse interval when the intermediate transfer belt 7 and the secondary transfer roller 6 are brought close to each other from the state where the intermediate transfer belt 7 is separated from the secondary transfer roller 6. Drives the transfer contact / separation mechanism. At the same time, the secondary transfer contact / separation mechanism is driven so as to be wider than the pulse interval when the intermediate transfer belt 7 comes into contact with the secondary transfer roller 6 and reaches a predetermined contact pressure. That is, the contact operation by the secondary transfer contact / separation mechanism is also performed here by adjusting the rotation speed and rotation angle of the DC motor 3 by the DC motor control circuit in accordance with the result of detecting the load fluctuation based on the feedback value subjected to feedback control. At the time, shock is buffered. Thereby, a shock jitter can be suppressed effectively.

  By the two controls described with reference to FIGS. 8 and 9, the speed at the moment of separation or contact between the secondary transfer roller 6 and the intermediate transfer belt 7 is made slower than the control using the conventional stepping motor. can do. For this reason, an impact is suppressed and a shock jitter can be reduced. In addition, the separation operation time and the contact operation time can be shortened.

  FIG. 10 is a perspective view showing an external configuration of the DC motor 3 provided in the above-described secondary transfer contact / separation mechanism.

  Referring to FIG. 10, the DC motor 3 is of a brushless type, and an encoder disk 13 is coaxially attached around the motor rotation shaft 16 of the motor body 12, and the motor body 12 in the vicinity of the encoder disk 13. A photo sensor 14 is attached to the. In addition, a driver circuit and a connector 15 are attached to a substrate (not shown) on the motor main body 12 so that input / output of a motor signal and an encoder signal is performed.

  FIG. 11 is a functional block diagram showing the detailed configuration of the drive device and load fluctuation estimation device for the DC motor 3 described above.

  Referring to FIG. 11, the drive device and the load fluctuation estimation device specifically show the functional configuration of the CPU 101 described above, and the functions of the host CPU 120 and the control circuit 121 cooperate with the functions of the motor driver 103. Is built.

  More specifically, a signal relating to the rotation direction and the number of moving pulses is passed from the target signal generation means 130 in the host CPU 120 to the target position / speed calculation circuit 131 in the control circuit 121. The target position / speed calculation circuit 131 derives the target position and target speed from the information obtained from the signal and the time information of an oscillator (not shown), and sends them to the position error speed error calculation circuit 136. The motor position / speed calculation circuit 132 in the control circuit 121 receives the encoder pulse A and encoder pulse B output from the two-channel photosensor 14 installed for the encoder disk 13 attached to the DC motor 3. measure. The two-channel photosensor 14 here has two sets of light-emitting elements and light-receiving elements, and is arranged so that the phase difference between the pulse signals is a predetermined amount. Therefore, the motor position / speed calculation circuit 132 can detect the rotation direction using the phase difference, and derives the motor position and the motor speed from the obtained information and the time information of an oscillator (not shown).

  The position error speed error calculation circuit 136 is based on a signal indicating the target position and target speed from the target position / speed calculation circuit 131 and a signal indicating the motor position and motor speed from the motor position / speed calculation circuit 132. Find the speed deviation. Then, the obtained position deviation and speed deviation are sent to the position / speed tracking controller 133. The position / speed tracking controller 133 performs control to track the position / speed so that the target position matches the motor position and the target speed matches the motor speed. Further, the position / speed tracking controller 133 sends various signals such as pulse width modulation (PWM), rotation direction, start / stop, and brake to the motor driver 103 as necessary. In the motor driver 103, the motor current and pulse width modulation (PWM) supplied to the DC motor 3 based on various signals obtained from the position / speed tracking controller 133 and the Hall signal from the Hall IC 134 provided in the DC motor 3. ) Control the voltage. Detection of load fluctuations when the secondary transfer roller 6 and the intermediate transfer belt 7 are in contact with or separated from each other is performed by detecting various errors calculated by the position error speed error calculation circuit 136 and pulse width modulation input to the motor driver 103 ( PWM) or the like. In the host CPU 120, the trigger detection unit 139 detects a trigger from the signal of the timer 137 and the sensor 138 that is an external input, and sends a stop command to the target signal generation unit 130. In addition, the characteristic value estimation unit 140 estimates the characteristic value and sends it to the trigger detection unit 139 for determination of trigger detection by the trigger detection unit 139.

  In the control to the secondary transfer contact / separation mechanism using the conventional stepping motor, the rotation speed cannot be changed at the moment when the rollers relating to the intermediate transfer repulsive roller 5 and the secondary transfer roller 6 contact each other. . For this reason, the load fluctuation indicating the impact at the moment of contact / separation becomes large and the shock jitter cannot be sufficiently suppressed. However, the secondary transfer contact / separation mechanism according to Example 1 can eliminate such disadvantages. That is, the impact at the moment when the secondary transfer roller 6 and the intermediate transfer belt 7 are separated or abutted by the feedback value of the feedback control in the DC motor control circuit with respect to the secondary transfer contact / separation mechanism using the DC motor 3 is shown. Detect load fluctuations. Then, the rotational speed and rotational angle of the DC motor 3 are adjusted according to the detected load fluctuation, and the rotational position of the eccentric cam 9 in the secondary transfer contact / separation mechanism, and the contact between the secondary transfer roller 6 and the intermediate transfer belt 7. Change the separation speed as appropriate. Thereby, when the secondary transfer roller 6 and the intermediate transfer belt 7 are separated or abutted, shock is buffered to suppress shock jitter. As a result, it is possible to detect the load fluctuation at the time of contact / separation between the secondary transfer roller 6 and the intermediate transfer belt 7 at low cost without providing a sensor for detecting the load fluctuation. Further, feedback control can be executed, and the contact / separation speed between the rollers associated with the intermediate transfer repulsive roller 5 and the secondary transfer roller 6 can be optimized to sufficiently suppress shock jitter.

  The technical point of the secondary transfer contact / separation mechanism of the first embodiment is that the intermediate transfer belt 7 is attached to the secondary transfer roller 6 facing the intermediate transfer repulsive roller 5 that contacts the intermediate transfer belt 7 via the conveyed sheet 8. In other words, the contacting / separating method according to the contacting / separating system including the contacting / separating mechanism for contacting or separating. The approach / separation method in this case has an approach / separation step and a deceleration step. In the contact / separation step, the intermediate transfer belt 7 is conveyed by the rotation of the eccentric cam 9 that is attached to the end of the rotary shaft 11 of the intermediate transfer repulsive roller 5 and rotates with the DC motor 3 controlled by the control means. The sheet is brought into contact with or separated from the secondary transfer roller 6 through the sheet 8. In the deceleration step, the CPU 101 decelerates the rotational speed of the DC motor 3 at the timing when the intermediate transfer belt 7 is separated or abutted between the opposing intermediate transfer repulsive roller 5 and secondary transfer roller 6. Thereby, shock jitter can be suppressed.

  By the way, the secondary transfer contact / separation mechanism according to the first embodiment does not provide a sensor for detecting the load fluctuation, and changes the load at the timing when the intermediate transfer repulsive roller 5 and the secondary transfer roller 6 or the intermediate transfer belt 7 come into contact with each other. It has a function of detecting and determining the stop position of the eccentric cam 9. This stop position of the eccentric cam 9 is called a home position (HP). According to such a function, there is a possibility that the home position cannot be determined at one place every time because the load fluctuation timing due to the contact / separation of the intermediate transfer repulsive roller 5 and the secondary transfer roller 6 or the intermediate transfer belt 7 varies. is there.

  FIG. 12 shows the relationship of the distance [mm] obtained by subtracting the sum of the roller radii from the distance between the centers of the rollers with respect to the rotation angle θ [deg] of the eccentric cam 9 when the secondary transfer contact / separation mechanism is controlled by the DC motor 3 described above. FIG. Here, the rollers indicate an intermediate transfer repulsive roller 5 and a secondary transfer roller 6.

  Referring to FIG. 12, when the secondary transfer contact / separation mechanism according to the first embodiment is driven by the DC motor 3, the rotational angle θ0 = 0 of the eccentric cam 9 when the DC motor 3 is activated at the time of initial separation. Assume that the eccentric cam 9 is rotated once from the home position (HP). In such a case, load fluctuations are detected at the rotation angles θ1 and θ3 of the eccentric cam 9 at the moment when the intermediate transfer repulsive roller 5 and the secondary transfer roller 6 or the intermediate transfer belt 7 come in contact with each other and stored in the storage means to be stored in the home position. To decide. Incidentally, the rotation angle θ1 of the eccentric cam 9 is an angle of timing at which the eccentric cam 9 shifts from contact to contact, and the rotation angle θ3 of the eccentric cam 9 is an angle of the timing to shift from contact to separation. The rotation angle θ2 of the eccentric cam 9 corresponds to the contact (nip) position angle, and the rotation angle θ4 of the eccentric cam 9 corresponds to the angle (= 360 degrees) of the home position (HP) rotated once. However, according to such a method, the intermediate transfer repulsive roller 5 and the secondary transfer roller 6 or the intermediate transfer belt 7 are contacted and separated from each other at the rotation angles θ0, θ1, θ3, and θ4 of the eccentric cam 9 in the direction of the arrow. Variation as shown in the range occurs, and the home position (HP) is not fixed at one point. Similarly, the contact (nip) position may be shifted every time. Therefore, the secondary transfer contact / separation mechanism described below is devised so that the home position (HP) is fixed at one point and the contact position is also fixed.

  FIG. 13 is a schematic view showing the main part of the secondary transfer contact / separation mechanism according to the second embodiment of the present invention in comparison with the case of the first embodiment. FIG. 13A is a diagram illustrating a home position when the eccentric cam 9 and the secondary transfer roller 6 are separated in the case of the first embodiment. FIG. 13B is a diagram illustrating a home position when the eccentric cam 9a and the secondary transfer roller 6 according to an example of the second embodiment are separated from each other, and a load fluctuation detection position when determining the home position. FIG. 13C is a diagram illustrating a home position when the eccentric cam 9b and the secondary transfer roller according to another example of the second embodiment are separated from each other, and a load fluctuation detection position when determining the home position. FIG. 13D is a diagram showing a home position when the eccentric cam 9c and the secondary transfer roller 6 according to another example of the second embodiment are separated from each other, and a load fluctuation detection position when determining the home position.

  13 (b), 13 (c), and 13 (d), the eccentric cams 9a, 9b, and 9c are convex in part compared to the eccentric cam 9 shown in FIG. 13 (a). Alternatively, it can be seen that a concave deformed portion is formed. The shape of the eccentric cams 9a, 9b, 9c according to the second embodiment is deformed more than the load fluctuation at the time of contact / separation in which the intermediate transfer belt 7 is separated or abutted between the intermediate transfer repulsive roller 5 and the secondary transfer roller 6 facing each other It is formed so that the load fluctuation at the time of the cam collision at the portion becomes large. Therefore, the drive device and the load fluctuation estimation device shown in FIG. 11 determine the stop positions of the eccentric cams 9a, 9b, and 9c based on the large load fluctuation. As a result, the home position can be determined at a single point without being affected by variations in load fluctuations. Incidentally, in the case of the eccentric cam 9 shown in FIG. 13 (a), it rotates in the direction of the arrow and has a smooth shape so as not to cause a large speed fluctuation when it rotates once. In this case, as described in the first embodiment, the home position is determined by detecting the load fluctuation when the intermediate transfer repulsive roller 5 and the secondary transfer roller 6 or the intermediate transfer belt 7 are in contact with each other.

  More specifically, the eccentric cam 9a shown in FIG. 13 (b) is provided with a convex deformation portion in part. The eccentric cam 9a detects a load fluctuation for determining the home position when it reaches a portion surrounded by a circle during one rotation. The speed fluctuation and position error at this time become larger on the minus side than the rotational speed target value. Further, the eccentric cam 9b shown in FIG. 13C is partially provided with a concave deformed portion. The eccentric cam 9b detects a change in load for determining the home position when it reaches a portion surrounded by a circle during one rotation. The speed fluctuation and position error at this time increase to the plus side with respect to the rotational speed target value. Further, the eccentric cam 9c shown in FIG. 13 (d) has a locally deformed portion and is provided with a flange-like deformed portion at a part thereof. The eccentric cam 9c is used by rotating it slightly less than one rotation when transitioning from separation to contact. The load fluctuation for determining the home position is detected when the circled point is reached during rotation. If the rotation continues, the deformed portion of the collar portion comes into contact with the secondary transfer roller 6 and stops at zero speed and no position error. Details will be described in detail later. Incidentally, the CPU 101 decelerates the rotational speed of the DC motor 3 at a timing based on such load fluctuation.

  FIG. 14 is a flowchart illustrating a control process for the secondary transfer contact / separation mechanism according to the second embodiment in which the DC motor 3 is driven. Incidentally, this control process is a DC motor that is common to any of the eccentric cam 9a shown in FIG. 13B, the eccentric cam 9b shown in FIG. 13C, and the eccentric cam 9c shown in FIG. 13D. 3 is used to determine the home position in the drive using 3.

  Referring to FIG. 14, in this control process, first, after the image forming apparatus is activated, the DC motor 3 is driven to rotate the eccentric cams 9a, 9b, 9c (step S1). The direction of rotation of the eccentric cams 9a, 9b, 9c may be either forward rotation operation or reverse rotation operation. Next, the cam collision fluctuation (speed fluctuation / position error) larger than the load fluctuation generated when the roller (intermediate transfer repulsive roller 5 and secondary transfer roller 6) and the belt (intermediate transfer belt 7) come in contact with each other is illustrated. 11 is detected (step S2). Here, the rollers (intermediate transfer repulsive roller 5 and secondary transfer roller 6) perform contact and separation operations by rotation of the eccentric cams 9a, 9b, and 9c. Although load fluctuation occurs at the moment of contact / separation, the magnitude of load fluctuation at the time of contact / separation is set so as not to be related to the determination of the home position. Then, the fluctuation exceeding the threshold range is shown in FIG. 11 for the first time when it reaches the position where the load fluctuation occurs at the time of contact or separation between the rollers (the intermediate transfer repulsive roller 5 and the secondary transfer roller 6) during rotation. It is detected by the driving device and the load fluctuation estimating device. This threshold range is set to a range higher than the maximum peak value of load fluctuations when the rollers (the intermediate transfer repulsive roller 5 and the secondary transfer roller 6) are brought into contact with each other. That is, the detection of the cam collision fluctuation here includes detection of a position error performed thereafter, in addition to the collision determination based on the speed fluctuation detection larger than the load fluctuation generated at the time of contact and separation. Further, when a position error is detected, the position where the position error is generated is set as a home position, or a position moved by several pulses therefrom is set as a home position (step S3). In this way, the home position can be determined by driving the secondary transfer contact / separation mechanism by test drive during startup, return from sleep, automatic restart, before and after transfer, front cover OFF / ON, etc. in the image forming apparatus. .

  FIG. 15 is a diagram for explaining a criterion for detecting a load fluctuation and a fluctuation at the time of a cam collision when the eccentric cam 9a shown in FIG. 13 (b) is applied by applying feedback control. It is a figure. FIG. 15A is a characteristic diagram of a fluctuation waveform with respect to time of the DC motor 3, and FIG. 15B is a diagram showing threshold determination and area determination in the local part of FIG. 15A.

  Referring to FIG. 15A, here, there are shown fluctuation waveforms when the secondary transfer contact / separation mechanism is driven by the DC motor 3 in accordance with the control process described in FIG. A portion surrounded by an oval shape corresponds to a cam collision position at a timing when the eccentric cam 9 a rotates and the convex step of the deformed portion collides with the secondary transfer roller 6. It can be seen that large fluctuations occur at this timing. This large fluctuation is detected by each value such as a current value, a speed error, a position error, a pulse width modulation (PWM), and a torque by the driving apparatus and the load fluctuation estimating apparatus shown in FIG. While the load fluctuation at the time of contact / separation between the rollers (intermediate transfer repulsive roller 5 and secondary transfer roller 6) varies in the generation timing, this large fluctuation determines the timing at one point. For this reason, the home position can be determined with high accuracy. Further, since the step of the convex portion of the deformed portion of the eccentric cam 9a is in contact with the secondary transfer roller 6, the fluctuation is on the minus side with respect to the target speed and the target position.

  As a judgment criterion for fluctuation detection at the time of cam collision, A. of FIG. In the threshold determination, it is confirmed that each value detected by feedback control of the DC motor 3 falls within a threshold range set on the negative side with respect to the target speed and target position. Specifically, it is determined that the step of the deformed portion of the eccentric cam 9a has collided with the secondary transfer roller 6 when the drive device and the load fluctuation estimation device shown in FIG. This threshold range is set to a value range that is larger on the minus side than the waveform peak P1 value of the load fluctuation at the time of contact / separation between the rollers (intermediate transfer repulsive roller 5 and secondary transfer roller 6). Since the waveform peak value P2 of the fluctuation at the time of the cam collision is larger on the minus side and falls within the threshold range, the home position can be determined accurately.

  In addition, B. of FIG. In the area determination (certain specific range), the step of the deformed portion of the eccentric cam 9a is detected by the secondary transfer roller 6 when the load fluctuation area of the specific range of each value detected by feedback control exceeds a predetermined threshold. It is determined that it collided with. This determination is also performed by the drive device and the load fluctuation estimation device shown in FIG. However, also here, the predetermined threshold value is set to a value larger than the fluctuation component when the rollers (the intermediate transfer repulsive roller 5 and the secondary transfer roller 6) come in contact with each other. Specifically, assuming that the average value of all data of each value detected by feedback control is 0, the eccentric cam 9a when the specific range where the load fluctuation is large and the area surrounded by 0 exceed a predetermined threshold value. It is considered that the step of the convex portion of the deformed portion collides with the secondary transfer roller 6. After the collision determination by the speed fluctuation detection, the position error is detected. Therefore, the position where the position error is generated when the position error is detected can be determined as the home position, or the position driven by several pulses therefrom can be determined as the home position. In this way, since the load fluctuation occurrence position at the time of the cam collision can always be made one point, the fluctuation detection at the time of the cam collision is detected when the rollers (the intermediate transfer repulsive roller 5 and the secondary transfer roller 6) are in contact with each other. It is possible to carry out with higher accuracy than in the case where the fluctuation detection is performed.

  FIG. 16 illustrates determination criteria (threshold determination and area determination) when detecting a cam collision change related to the DC motor 3 when the eccentric cam 9b shown in FIG. 13 (c) is applied by applying feedback control. It is the figure shown in order to do.

  Referring to FIG. 16, although the characteristic diagram of the fluctuation waveform with respect to time of the DC motor 3 is omitted here, the fluctuation is on the plus side with respect to the target speed and target position, contrary to the case of FIG. Applicable when fluctuating. As in the case of FIG. 15A, the eccentric cam 9 b rotates to cause the deformed portion to collide with the secondary transfer roller 6, and greatly fluctuate to the plus side at the timing when the concave portion of the deformed portion enters the secondary transfer roller 6. Produce. This large fluctuation is detected by each value such as a current value, a speed error, a position error, a pulse width modulation (PWM), and a torque by the driving apparatus and the load fluctuation estimating apparatus shown in FIG. While the load fluctuation at the time of contact / separation between the rollers (intermediate transfer repulsive roller 5 and secondary transfer roller 6) varies in the generation timing, this large fluctuation determines the timing at one point. For this reason, the home position can be determined with high accuracy.

  As a criterion for detection of fluctuation at the time of cam collision, A. of FIG. In the threshold determination, it is confirmed that each value detected by the feedback control of the DC motor 3 falls within the threshold range set on the plus side with respect to the target speed and target position. Specifically, when the drive device and load fluctuation estimation device shown in FIG. 11 enter the threshold range, the deformed portion of the eccentric cam 9b collides with the secondary transfer roller 6, and the concave portion of the deformed portion is subjected to the secondary transfer. It is determined that the roller 6 has been entered. This threshold range is set to a value range larger on the plus side than the waveform peak P1 value of the load fluctuation at the time of contact between the rollers (the intermediate transfer repulsive roller 5 and the secondary transfer roller 6). Again, the waveform peak value P2 of the fluctuation at the time of the cam collision is larger on the plus side and falls within the threshold range, so that the home position can be determined accurately.

  In addition, B. of FIG. In the area determination (certain specific range), the concave portion of the deformed portion of the eccentric cam 9b is the secondary transfer roller when the load fluctuation area of the specific range of each value detected by feedback control exceeds a predetermined threshold. 6 is determined to have collided. This determination is also performed by the drive device and the load fluctuation estimation device shown in FIG. However, also here, the predetermined threshold value is set to a value larger than the fluctuation component when the rollers (the intermediate transfer repulsive roller 5 and the secondary transfer roller 6) come in contact with each other. Specifically, when the average value of all data of each value detected by feedback control is set to 0, the eccentric cam 9b when the specific range where the load fluctuation is large and the area surrounded by 0 exceed a predetermined threshold value. It is determined as the detection of the collision of the concave portion of the deformed portion. After the collision determination by the speed fluctuation detection, the position error is detected. Therefore, the position where the position error is detected when the position error is detected can be determined as the home position, or the position driven by several pulses therefrom can be determined as the home position. In this way, since the load fluctuation occurrence position can always be one point, fluctuation detection at the time of cam collision is detected at the time of contact / separation between the rollers (intermediate transfer repulsive roller 5 and secondary transfer roller 6). It can be performed with higher accuracy than when it is performed.

  FIG. 17 shows the time of the eccentric cam 9c in order to explain the position error calculation via the cam collision variation by applying the feedback control related to the DC motor 3 when the eccentric cam 9c shown in FIG. 13 (d) is applied. It is the figure which showed the characteristic of the rotation angle [deg] with respect to [ms].

  Referring to FIG. 17, as described with reference to FIG. 13D, when the eccentric cam 9c rotates, the hook-shaped portion of the deformed portion hits the secondary transfer roller 6, and the speed becomes zero and the position error becomes zero. Stop. Here, a state of detecting a position error at the time of a collision is shown. Specifically, time t0 indicates the position of the eccentric cam 9c at the moment of activation. In this state, the rollers (intermediate transfer repulsive roller 5 and secondary transfer roller 6) are separated from each other. From this state, as the control process described with reference to FIG. 14, the image forming apparatus is turned on to drive the eccentric cam 9c in the direction of the arrow. In the time range from time t0 to time t1 in FIG. 17, a constant rotation amount (rotation angle) with respect to time is obtained by driving the DC motor 3.

  Then, when rotating to the position of time t1, the hook-shaped portion of the deformed portion of the eccentric cam 9c hits the secondary transfer roller 6 as shown by a circled portion. At this time, since it cannot rotate any more, the amount of rotation decreases rapidly or becomes zero as shown in FIG. The position error at this time is determined from each value such as a current value, speed error, position error, pulse width modulation (PWM), torque, etc. detected by the feedback control of the DC motor 3 by the driving device and load fluctuation estimation device shown in FIG. calculate. Then, a position error from the target rotational position is calculated, and a collision determination based on speed fluctuation detection is performed depending on whether or not the value exceeds a set threshold value. After the collision determination by this speed fluctuation detection, a position error is separately detected. Therefore, the position where the position error is detected when the position error is detected can be determined as the home position, or the position driven by several pulses therefrom can be determined as the home position. In this way, since the load fluctuation occurrence position can always be one point, fluctuation detection at the time of cam collision is detected at the time of contact / separation between the rollers (intermediate transfer repulsive roller 5 and secondary transfer roller 6). It can be performed with higher accuracy than when it is performed.

  FIG. 18 shows a comparison of the driving time of the DC motor 3 and the separation distance with respect to time [ms] when the secondary transfer contact / separation mechanism according to the first embodiment is separated from the secondary transfer contact / separation mechanism according to the second embodiment. It is the figure shown by the relationship of distance [mm] which subtracted the sum of the roller radius from the distance between roller centers. FIG. 18A is a diagram illustrating a case where the home position of the secondary transfer contact / separation mechanism according to the first embodiment is shifted. FIG. 18B is a diagram illustrating a case where the home position of the secondary transfer contact / separation mechanism according to the second embodiment is determined at one point in comparison with the secondary transfer contact / separation mechanism according to the first embodiment. Here, however, the rollers indicate the intermediate transfer repulsive roller 5 and the secondary transfer roller 6.

  Referring to FIG. 18A, in the secondary transfer contact / separation mechanism according to the first embodiment, as described with reference to FIG. 12, rollers (intermediate transfer repulsive roller 5 and secondary transfer roller 6), belts ( Variations occur in the timing at which the intermediate transfer belt 7) contacts and separates. For this reason, the home position is not fixed at one point, and the contact position may be similarly shifted every time. As a countermeasure, the time range Δt from the shift timing o that shifts to separation through the end timing n at which the contact is stable to the shift timing q immediately after separation through the switching point timing p is increased. However, it is necessary to reduce the speed at the moment of contact and separation. Incidentally, the separation becomes stable when the start point timing r at which the separation becomes stable is reached after the timing q of the shift immediately after the separation. If the time range Δt here is large, the sheet conveyance speed cannot be increased when applied to the image forming apparatus, and the productivity is lowered because there is no time.

  On the other hand, referring to FIG. 18B, in the secondary transfer contact / separation mechanism according to the second embodiment, as described above, the roller (the intermediate transfer repulsive roller 5 and the secondary transfer roller 6), the belt (the intermediate transfer). There is no variation in the timing at which the belts 7) contact and separate. For this reason, the home position is fixed at one point, and the contact position does not shift each time as well. Further, the time range Δt ′ from the timing t of the shift that shifts to the separation via the end point timing s where the contact is stable, to the timing w of the shift immediately after the separation through the timing p of the switching point is the previous time. It is smaller than the range Δt. The time range Δt ′ indicates that the range in which the speed is decreased before and after contact / separation can be narrowed. It can also be seen that there is a time margin between timing n and timing s and between timing r and timing x. Incidentally, the separation becomes stable after reaching the timing x of the starting point at which the separation becomes stable after the timing w of the shift immediately after the separation. If the time range Δt ′ here is small, it is possible to afford time when applied to the image forming apparatus. Therefore, it is possible to narrow the space between sheets or increase the sheet conveyance speed to improve productivity.

  It should be noted that the present invention is not limited to the gist described in each of the embodiments in the above-described embodiment, and various modifications are possible without departing from the technical spirit thereof, and the technical idea described in the claims. All the technical matters included in the subject matter are the subject of the present invention. Each of the above embodiments is a preferable example, but those skilled in the art can implement various modifications from the disclosed contents, and these are within the scope of the appended claims. Included in the described technical scope.

DESCRIPTION OF SYMBOLS 1 Transfer apparatus 2 Primary transfer roller 3 DC motor 4 Belt 5 Intermediate transfer repulsive roller 6 Secondary transfer roller 7 Intermediate transfer belt 8 Sheet 9, 9a, 9b, 9c Eccentric cam 10 Opposing bearing 11 Rotating shaft 12 Motor body 13 Encoder disk 14 Photosensor 15 Connector 16 Motor rotating shaft 17 Filler 18a Light emitting element 18b Light receiving element 101 CPU
DESCRIPTION OF SYMBOLS 102 Voltage control (CTL) part 103 Motor driver 104 Adder 105 Mechanical circuit 106 Integration (1 / s) circuit 107 Current detection circuit 108 Torque estimation process part 120 Host CPU
121 control circuit 130 target signal generating means 131 target position / speed calculation circuit 132 motor position / speed calculation circuit 133 position / speed tracking controller 134 Hall IC
137 timer 138 sensor 139 trigger detection unit 140 characteristic value estimation unit

Japanese Patent Laying-Open No. 2015-135394

Claims (11)

A first roller that contacts the belt, a second roller that faces the first roller, and a contact / separation mechanism that contacts or separates the belt from the second roller via a conveyed sheet; A contact / separation system with
The contact / separation mechanism includes an eccentric cam that is attached to an end portion of a rotation shaft of the first roller and rotates using a motor as power, and a control unit that controls the motor. A belt is brought into contact with or separated from the second roller via the conveyed sheet;
The control means is a contact / separation system that decelerates the rotational speed of the motor at a timing when the belt is separated or abutted between the first roller and the second roller facing each other. The contact / separation system according to claim 1,
The control means is a contact / separation system that feedback-controls the rotation speed and rotation angle of the motor. The contact / separation system according to claim 1 or 2,
The eccentric cam is a contacting / separating system in which a convex or concave deformed part is formed in part. The contact / separation system according to claim 3,
The shape of the eccentric cam is such that the load at the time of a cam collision at the deforming portion is larger than the load fluctuation at the time of contact / separation in which the belt is separated or abutted between the first roller and the second roller facing each other. Formed so that the fluctuation is large,
The control means is a contact / separation system that reduces the rotational speed of the motor at a timing based on the load fluctuation. The contact / separation system according to any one of claims 1 to 4,
The control means stores the timing of the moment when it is determined that the contact is detected in the storage means, and the belt faces the speed in a period within a predetermined time before and after the timing of the moment of contact by the contact / separation mechanism. The speed at which the belt is moved toward the first roller and the second roller facing each other from the state of being separated from the first roller and the second roller, and the belt facing the belt A contact / separation system that drives the contact / separation mechanism so as to be slower than the speed at which pressurization is performed until a predetermined contact pressure is reached after contacting the first roller and the second roller. The contact / separation system according to any one of claims 1 to 4,
The control means stores in the storage means the timing of the moment when it is determined that the separation is detected, and the belt is opposed to the belt for a speed within a predetermined time before and after the timing of the separation by the contact / separation mechanism. The speed at which the contact pressure between the first roller and the second roller facing the belt is decreased from the state in contact with the first roller and the second roller, and the belt is opposed to the belt. A contact / separation system that drives the contact / separation mechanism so as to be slower than a speed when the distance is increased after the first roller and the second roller are separated from each other. The contact / separation system according to any one of claims 1 to 4,
The control means stores in the storage means the timing of the moment when it is determined that contact is detected, and regarding the pulse interval in a pulse interval within a predetermined number of pulses before and after the timing of the moment of contact by the contact / separation mechanism, the belt Between the first roller and the second roller facing each other, the pulse interval when the first roller and the second roller facing the belt are brought close to each other, and the belt A contact / separation system that drives the contact / separation mechanism so as to be wider than a pulse interval at the time of pressurization until a predetermined contact pressure is reached after contacting the first roller and the second roller facing each other. The contact / separation system according to any one of claims 1 to 4,
The control means stores in the storage means the timing of the moment when it is determined that the separation is detected, and the belt is configured to perform pulse intervals in a pulse interval within a predetermined number of pulses before and after the timing of the separation by the contact / separation mechanism. A pulse interval when the contact pressure between the first roller and the second roller facing the belt is reduced from a state in contact with the first roller and the second roller facing each other; and A contact / separation system that drives the contact / separation mechanism to be wider than a pulse interval when the distance is increased after the first roller and the second roller facing the belt are separated from each other. The contact / separation system according to any one of claims 1 to 8,
The control means is an approach / separation system provided in a host central processing unit that transports a recording medium.   An image forming apparatus comprising the contact / separation system according to claim 9 and the central processing unit. A contact / separation method according to a contact / separation system including a contact / separation mechanism for contacting or separating a belt from or to a second roller facing a first roller contacting the belt via a conveyed sheet,
The belt is moved to the second roller via the conveyed sheet by the rotation of an eccentric cam attached to the end of the rotating shaft of the first roller and rotated by a motor controlled by a control means. A contacting / separating step for contacting or separating; and
A contacting / separating method, comprising: a decelerating step in which the control means decelerates the rotation speed of the motor at a timing when the belt is separated or abutted between the first roller and the second roller facing each other.