Image forming apparatus and failure detection method

Abstract

To provide an image formation device and a failure detection method that can detect the failure of a connection means switching connection / shut off with a pair of carrier rollers conveying a sheet and a driving means driving the pair of carrier roller.SOLUTION: A device comprises a pair of carrier rollers 31 that conveys a sheet P and is rotatable, a driving means 41 rotationally driving the pair of the carrier rollers 31, a driving instruction means 102 instructing the driving means 41 of driving, a connection means 51 switching connection / shut off of the driving means 41 with the pair of carrier rollers 31, a rotation detection means 41b detecting the rotation of the driving means 41, a determination means 103 that determines the fact that the connection means 51 is failed if the driving instruction means 102 is at a state where it does not instruct the driving means 41 of driving and when the rotation detection means 41b detects the rotation of the driving means 41.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus such as a copying machine, a printer, or a multi-function digital multifunction peripheral (MFP) that conveys paper and performs printing, and to a failure detection method. [Background technology]

[0002] In an image forming apparatus, a sheet is conveyed by clamping the sheet between a pair of conveying rollers and rotating the pair of conveying rollers with a drive motor, which is a driving means. At this time, the conveying roller pairs are driven in order from the upstream in the sheet conveying direction (FD direction), but there are cases where the conveying of the sheet is temporarily stopped to adjust the gap between the sheets, and only the downstream roller pair is driven again to convey the sheet. In this case, the upstream conveying roller pair rotates in conjunction with the conveying of the sheet while being disconnected from the drive motor.

[0003] The transport roller pair and the drive motor that drives them can be switched between connected and disconnected via a clutch, which is a connecting means. Therefore, when only the downstream transport roller pair is driven again to transport paper, the upstream transport roller pair and the drive motor are disconnected by the clutch.

[0004] However, when a clutch disconnection failure occurs, the upstream transport roller pair remains connected to the drive motor, increasing the load on the downstream transport roller pair, deteriorating transport performance and causing paper jams and oblique transport (paper skew). On the other hand, deterioration of the upstream transport roller pair can cause slippage, which can lead to increased load on the downstream transport roller pair, paper jams, paper skew, etc., so when these problems occur, it is difficult to determine whether the problem is due to a clutch connection failure or deterioration of the transport roller pair. For this reason, it has been necessary to replace both the clutch and the transport roller pair, which takes time to repair.

[0005] Patent Document 1 discloses an image forming apparatus that controls the rotational operation of a motor by referring to an encoded output signal indicating the rotational operation state output from the motor, extracts features of the actual operating state such as the transition time and period of the encoded output signal, the number of pulses within a certain period, and the frequency obtained by FFT analysis, and performs fault diagnosis by comparing the extracted features of the actual operating state with reference features stored in a reference feature storage unit.

[0006] Patent document 2 discloses an image forming device having a first mode in which a transmission member transmits a driving force to rotate a rotating member at a first rotational speed, and a second mode in which the transmission member transmits a driving force to rotate the rotating member at a second rotational speed (<first rotational speed), switching modes as necessary, measuring the stop time of the drive motor after a command to switch to the second mode is issued, and determining whether or not an abnormality has occurred in the transmission member based on the stop time.

[0007] Patent document 3 discloses an image forming apparatus having a main motor, a main motor FG circuit that determines the rotational speed based on an FG signal output from the main motor, a developing clutch for transmitting the driving force of the main motor to the developing screw, and a CPU, in which the CPU controls the developing clutch to a connected state and rotates the developing screw using the main motor, determines the rotational speed of the main motor using the main motor FG circuit, and detects an abnormality in the developing clutch if the time it takes for the rotational speed to reach the target speed is shorter than a predetermined time. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2007-212719 A [Patent Document 2] JP 2013-148696 A [Patent Document 3] JP 2019-211678 A Summary of the Invention [Problem to be solved by the invention]

[0009] However, in the image forming device described in Patent Document 1, the encoded output signal indicating the rotational operating state output from the motor is output as long as the motor is rotating, so it is not possible to determine a disconnection failure due to a clutch malfunction based on the encoded output signal.

[0010] In addition, the image forming devices described in Patent Documents 2 and 3 can detect connection failure of the clutch in the development system, but cannot determine failure of the clutch that connects and disconnects the drive motor of the paper transport roller pair.

[0011] This invention has been made in consideration of the above technical background, and aims to provide an image forming apparatus and a fault detection method that are capable of detecting a fault in a connection means that switches between connection and disconnection between a pair of transport rollers that transport paper and a drive means that drives the pair of transport rollers. [Means for solving the problem]

[0012] The above object can be achieved by the following means: (1) a pair of rotatable first transport rollers for transporting paper; a second conveying roller pair located downstream in a paper conveying direction as viewed from the first conveying roller pair; a first driving means for driving the first pair of conveying rollers to rotate; a second driving means for driving the second pair of conveying rollers to rotate; a drive instruction means for instructing the first drive means and the second drive means to drive; a first connection means for connecting the first drive means and the first transport roller pair when the drive instruction means is instructing the first drive means to drive, and for disconnecting the first drive means and the first transport roller pair when the drive instruction means is not instructing the first drive means to drive; a second connection means for switching between connection and disconnection between the second drive means and the second pair of transport rollers; a rotation detection means for detecting the rotation of the first driving means; a determination means for determining whether the first connection means is faulty; Equipped with An image forming apparatus characterized in that, when a sheet of paper is straddled between the first transport roller pair and the second transport roller pair, the second connection means connects the second drive means to the second transport roller pair, and the drive instruction means instructs the second drive means to be driven so that the second transport roller pair transports the sheet, if the drive instruction means is not instructing the first drive means to drive and the rotation detection means detects the rotation of the first drive means, the judgment means judges that the first connection means is faulty. (2) An image forming apparatus as described in the preceding paragraph 1, wherein the first driving means is a brushless motor driven in a sensorless manner, and voltage pulses are applied at regular time intervals at a predetermined electrical angle, and when there is a difference of a predetermined value or more in the current value for each applied pulse, the rotation detection means detects the rotation of the first driving means. (3) The image forming apparatus according to item 2, wherein the voltage pulses of the predetermined electrical angle are pulses of two different electrical angles, the relative electrical angle difference being 180 degrees. (4) The image forming apparatus according to claim 1, wherein the first driving means is a brushless motor or a stepping motor having an encoder, and the rotation detection means detects the rotation of the first driving means by detecting the rotation of the encoder. (5) The image forming apparatus according to claim 1, wherein the first driving means is a brushless motor having an FG pattern, and the rotation detection means detects the rotation of the first driving means based on a signal from the FG pattern. (6) The image forming apparatus according to claim 1, wherein the first driving means is a brushless motor having a Hall element, and the rotation detection means detects the rotation of the first driving means based on a signal from the Hall element. (7) The image forming apparatus according to claim 1, wherein the first driving means is a brushless motor or a stepping motor, and the rotation detection means detects the rotation of the first driving means by generation of a back electromotive force in the brushless motor or the stepping motor. (8) An image forming apparatus according to any one of paragraphs 1 to 7, wherein the first connecting means and the second connecting means are either a one-way clutch that switches between connection and disconnection by mechanical action, or an electromagnetic clutch that switches between connection and disconnection by electromagnetic action. (9) a pair of rotatable first transport rollers for transporting paper; a second conveying roller pair located downstream in a paper conveying direction as viewed from the first conveying roller pair; a first driving means for driving the first pair of conveying rollers to rotate; a second driving means for driving the second pair of conveying rollers to rotate; a drive instruction means for instructing the first drive means and the second drive means to drive; a first connection means for connecting the first drive means and the first transport roller pair when the drive instruction means is instructing the first drive means to drive, and for disconnecting the first drive means and the first transport roller pair when the drive instruction means is not instructing the first drive means to drive; a second connection means for switching between connection and disconnection between the second drive means and the second pair of transport rollers; An image forming apparatus comprising: a drive instruction step of instructing the first drive means and the second drive means to drive; a rotation detection step of detecting rotation of the first driving means; a determination step of determining whether the first connection means is faulty; Run A fault detection method characterized in that, when a sheet of paper is straddled between the first transport roller pair and the second transport roller pair, the second drive means and the second transport roller pair are connected by the second connection means, and the second drive means is driven by an instruction to drive the second drive means in the drive instruction step, and the second transport roller pair transports the sheet, if the first drive means is not instructed to drive and rotation of the first drive means is detected in the rotation detection step, the judgment step judges that the first connection means is faulty. Effect of the Invention

[0013] The preceding paragraph (1) and 9 According to the invention described in When a sheet is placed between the first transport roller pair and the second transport roller pair, the second drive means and the second transport roller pair are connected by the second connection means, and a drive command is issued to drive the second drive means so that the second transport roller pair transports the sheet, when the first drive means is not instructed to drive and rotation of the first drive means is detected, Because the connection is deemed to be broken, 1. It is possible to reliably detect when the connection means has broken down and is thus in a disconnection state. 1. Is there a connection failure? 1. It is possible to identify whether the transport roller pair is defective, 1. Connection means and 1. Since it is necessary to replace only one of the pair of conveying rollers, the time required for part replacement during repairs can be reduced.

[0017] The previous paragraph ( 2 According to the invention described in ), the drive means is a brushless motor driven without a sensor, and voltage pulses are applied at regular time intervals at a predetermined electrical angle, and when there is a difference of a predetermined value or more in the current value for each applied pulse, the rotation of the drive means is reliably detected.

[0018] The previous paragraph ( 3 According to the invention described in (1), voltage pulses of a predetermined electrical angle are applied at regular time intervals, with two different electrical angles having a relative electrical angle difference of 180 degrees, and when there is a difference of a predetermined value or more in the current value for each applied pulse, the rotation of the drive means is detected.

[0019] The previous paragraph ( 4According to the invention described in , the driving means is a brushless motor or a stepping motor having an encoder, and the rotation of the driving means is reliably detected by detecting the rotation of the encoder.

[0020] The previous paragraph ( 5 According to the invention described in ), the driving means is a brushless motor having an FG pattern, and the rotation of the driving means is reliably detected based on a signal from the FG pattern.

[0021] The previous paragraph ( 6 According to the invention described in , the driving means is a brushless motor having a Hall element, and the rotation of the driving means is reliably detected based on a signal from the Hall element.

[0022] The previous paragraph ( 7 According to the invention described in , the driving means is a brushless motor or a stepping motor, and the rotation of the driving means is reliably detected by the generation of back electromotive force in the brushless motor or the stepping motor.

[0026] The previous paragraph ( 8 According to the invention described in the above, it is possible to detect a failure in either a one-way clutch that switches between connection and disconnection by mechanical action, or an electromagnetic clutch that switches between connection and disconnection by electromagnetic action. [Brief description of the drawings]

[0027] [Figure 1] 1 is a configuration diagram of a main part of an image forming apparatus according to an embodiment of the present invention; [Diagram 2] 3 is a block diagram showing the configuration of a control system for a first motor and a second motor. FIG. [Diagram 3] FIG. 2 is a diagram showing a schematic configuration of a plurality of transport roller pairs, each driving means, and each connecting means. [Figure 4] FIG. 4 is an operation sequence diagram of each driving means. [Diagram 5]10 is a flowchart showing a failure determination process of a connection means executed by a drive instruction means. [Figure 6] FIG. 11 is a block diagram illustrating the configuration of a control system for a first motor and a second motor according to another embodiment of the present invention. [Figure 7] 7 is a diagram showing a schematic configuration of a plurality of transport roller pairs, each driving means, and each connecting means in the embodiment of FIG. 6. FIG. [Figure 8] 7 is a block diagram showing a specific configuration of a sensorless vector control unit in the embodiment of FIG. 6. [Figure 9] 7A is an operation sequence diagram of each driving means in the embodiment of FIG. 6, and (B) and (C) are waveform diagrams showing typical peak current values. [Figure 10] 7 is a flowchart showing a failure determination process of a connection means executed by a drive instruction means in the embodiment of FIG. 6. [Figure 11] FIG. 11 is a diagram illustrating a schematic configuration of transport roller pairs, a drive means, and a connection means in a case where one drive means is shared by multiple transport roller pairs according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0029] FIG. 1 is a configuration diagram of a main part of an image forming apparatus according to an embodiment of the present invention.

[0030] 1, the image forming apparatus 1 includes a main body 1 and a paper feed section 2. Paper P fed from the paper feed section 2 is sandwiched between a three-stage vertical transport roller pair (hereinafter also referred to as a first transport roller pair) 31, and is transported downstream in the paper transport direction (upward in FIG. 1) by the rotation of the first transport roller pair 31.

[0031] The first conveying roller pair 31 is connected to the first motor 41, which is a driving means, via the first clutch 51, which is a connecting means. The first clutch 51 switches between connection and disconnection between the first motor 41 and the first conveying roller pair 31, and switches between the first motor 41 and the first conveying roller pair 31 to connection when the first motor 41 is instructed to drive, and switches between disconnection when the first motor 41 is not instructed to drive. When the first motor 41 and the first conveying roller pair 31 are in a connected state, the rotational driving force of the first motor 41 is transmitted to the first conveying roller pair 31, and the first conveying roller pair 31 is driven to rotate. On the other hand, when the first clutch 51 is in a disconnected state, the transmission of the rotational driving force from the first motor 41 to the first conveying roller pair 31 is interrupted.

[0032] A first transport sensor 61 that detects the leading edge of the paper P transported from the first transport roller pair 31 is provided near the downstream side of the first transport roller pair 31 in the paper transport direction.

[0033] Further downstream in the paper transport direction of the first transport sensor 61, a two-stage vertical transport roller pair (hereinafter also referred to as a second transport roller pair) 32 is disposed. The paper P transported by the first transport roller pair 31 is sandwiched between the second transport roller pair 32 and transported downstream in the paper transport direction by the rotation of the second transport roller pair 32.

[0034] The second conveying roller pair 32 is connected to the second motor 42 via a second clutch 52 serving as a connection means. The second clutch 52 switches between connection and disconnection between the second motor 42 and the second conveying roller pair 32, and in the connected state, the rotational driving force of the second motor 42 is transmitted to the second conveying roller pair 32, so that the second conveying roller pair 32 is rotated. On the other hand, in the disconnected state of the second clutch 52, the transmission of the rotational driving force from the second motor 42 to the second conveying roller pair 32 is interrupted.

[0035] A second transport sensor 62 that detects the leading edge of the paper P transported from the second transport roller pair 32 is provided near the downstream side of the second transport roller pair 32 in the paper transport direction.

[0036] Further downstream in the paper transport direction of the second transport sensor 62, a timing roller pair 33 is disposed. The paper P transported by the second transport roller pair 32 is sandwiched between the timing roller pair 33 and transported by the rotation of the timing roller pair 33 to a printing unit (not shown) located downstream in the paper transport direction, and by adjusting the timing of the rotation drive of the timing roller pair 33, the timing of the paper P entering the printing unit can be adjusted, or the inclination of the paper can be corrected by aligning the leading edge of the paper P. The timing roller pair 33 is connected to a third motor 43, and the timing roller pair 33 is rotationally driven by the rotation drive force of the third motor 43.

[0037] A timing sensor 63 that detects the leading edge of the paper entering the timing roller pair 33 is provided near the upstream side of the timing roller pair 33 in the paper transport direction.

[0038] In the image forming device shown in Figure 1, the paper P is transported across both the second transport roller pair 32 and the first transport roller pair 31, and when the leading edge of the paper P reaches the second transport sensor 62, the paper P stops temporarily to align the leading edge of the paper with the timing roller pair 33, and then the paper P is transported only by the second transport roller pair 32.

[0039] For this reason, normally, the first motor 41 that drives the first upstream conveying roller pair 31 is stopped, and the first clutch 51 is switched to a disconnected state, so that the first conveying roller pair 31 rotates freely and does not become a load on the second conveying roller pair 32.

[0040] However, when the first clutch 51 breaks down and a disconnection failure occurs, if the first clutch 51 is an electromagnetic clutch that switches between connection and disconnection by electromagnetic action, the connected state of the first clutch 51 and the first transport roller pair 31 is maintained, and even if the first clutch 51 is a mechanical clutch such as a one-way clutch that switches between connection and disconnection by mechanical action, the first clutch 51 is locked, and the connected state of the first clutch 51 and the first transport roller pair 31 is also maintained. Therefore, the first transport roller pair 31 is connected to the first motor 41 via the first clutch 51, which becomes a load on the second transport roller pair 32, and paper jams occur due to paper slippage or loss of synchronism of the second motor 42, and image inclination occurs due to paper skew.

[0041] On the other hand, as described above, when the first transport roller pair 31 deteriorates and does not rotate smoothly, causing slippage between the first transport roller pair 31 and the paper P, this also places a load on the second transport roller pair 32, but conventionally it was not possible to identify whether the first clutch 51 or the first transport roller pair 31 was at fault. For this reason, when frequent malfunctions occurred and a serviceman or the like needed to replace the faulty parts, both the first transport roller pair 31 and the first clutch 51 were replaced, which took a lot of time for the repair.

[0042] Therefore, in this embodiment, the following configuration is provided to detect whether the first clutch 51 is faulty, making it possible to determine whether the first conveying roller pair 31 or the first clutch 51 needs to be replaced.

[0043] FIG. 2 is a block diagram showing the configuration of the control system for the first motor 41 and the second motor 42, and FIG. 3 is a schematic diagram showing the configurations of the first conveying roller pair 31, the second conveying roller pair 32, the first motor 41, the second motor 42, the first clutch 51 and the second clutch 52.

[0044] In this embodiment, failure detection of the first clutch 51 is performed when the first motor 41 is a brushless motor equipped with an encoder 41b and the second motor 42 is a stepping motor.

[0045] As shown in FIG. 2, the image forming apparatus is equipped with a transport control IC 100 that controls the transport during the overall operation. The transport control IC 100 functionally includes a transport control unit 101 that controls the overall transport of paper P, a drive instruction unit 102 that instructs the first and second motors 41, 42 to drive, and a speed control unit 105 that controls the speed of the first and second motors 41, 42.

[0046] The transport control unit 101 receives signals from the first transport sensor 61 and the second transport sensor 62, and transmits instructions to the drive instruction unit 102 regarding drive start timing and drive conditions (parameters such as the speeds of the first and second motors 41, 42). The transport control unit 101 also changes instructions to the drive instruction unit 102 based on ON / OFF signals from the first and second transport sensors 61, 62. Based on the received instruction information, the drive instruction unit 102 outputs a clock (speed) signal to the second motor 42 via a driver IC 104, and also transmits a target speed ω * to the speed control unit 105. The second motor 42 is driven to rotate at a speed according to the clock (speed) signal. When the first clutch 51 and the second clutch 52 are electromagnetic clutches or the like, the drive instruction unit 102 further instructs these clutches to switch between connection and disconnection.

[0047] The speed control unit 105 includes a PWM conversion unit 106 and an FV conversion unit 107. The PWM conversion unit 106 converts the target speed ω * is converted into a PWM signal and output to the drive IC 41a of the second motor 42, and the second motor 42 is controlled to a target speed by the drive IC 42a. Such speed control of the second motor 42 is performed by normal PI control.

[0048] At this time, the signal from the encoder 41b of the first motor 41 is converted to an actual speed ω by the FV conversion unit 107 of the speed control unit 105. This actual speed ω is used for feedback control in the PWM conversion unit 106, and is also input to the drive instruction unit 102 and used by the failure determination unit 103 to determine whether or not the first clutch 51 has a failure.

[0049] The determination information of the malfunction determination unit 103 is output to the transport control unit 101, and the transport control unit 101 performs necessary processing such as displaying a malfunction depending on the malfunction determination result.

[0050] 4 is an operation sequence diagram of the first motor 41 and the second motor 42. In period T1, the first motor 41 is driven, the first clutch 51 is switched to a connected state, the first conveying roller pair 31 is rotated via the first clutch 51, and the paper P is conveyed downstream to reach the second conveying roller pair 32. During this time, when the first conveying sensor 61 turns on, the rotation speed of the first motor 41 is reduced for a certain period of time for paper gap control. After the paper gap control is completed, when the second conveying sensor 62 turns on, the first motor 41 is stopped.

[0051] When the first motor 41 stops, the first clutch 51 is switched to a disconnected state, and the rotation of the first transport roller pair 31 also stops. When the paper gap control time T2 has elapsed after the first transport roller pair 31 stops, the second motor 42 is started and the second clutch 52 is switched to an engaged state, the second transport roller pair 32 is driven to rotate via the second clutch 52, and the paper P is transported further downstream. In this state, the first transport roller pair 31 rotates in conjunction with the transport of the paper, but because the first clutch 51 is in a disconnected state, the rotational force of the first transport roller pair 31 is not transmitted to the first motor 41.

[0052] However, if the first clutch 51 breaks down and a disconnection failure occurs, resulting in a constantly connected state, the first motor 41 rotates together with the first transport roller pair 31 via the first clutch 51 in association with paper transport by the rotational drive of the second transport roller pair 32, even though no instruction has been given to drive the first motor 41. This causes slippage between the second transport roller pair 32 and the paper P, increasing the load on the second motor 42, and the second motor 42 does not increase in rotation speed to the intended speed during the operation period T3 of the second motor 42.

[0053] Regardless of whether or not the drive of the first motor 41 has been instructed, when the first motor 41 rotates, the encoder 41b provided in the first motor 41 rotates, and a signal from the encoder 41b is transmitted to the speed control unit 105. Further, information on the actual speed ω is transmitted from the speed control unit 105 to the failure detection unit 103 of the drive instruction unit 102.

[0054] Therefore, when the rotation of the first motor 41 is detected even though the drive instruction unit 102 has not instructed the first motor 41 to drive, it can be determined that the first clutch 51 is broken, and it can be reliably identified whether the first conveying roller pair 31 is defective or the first clutch 51 is broken. As a result, during repair, it is only necessary to replace either the first conveying roller pair 31 or the first clutch 51, and there is no need to replace them together, so the time required for part replacement can be shortened.

[0055] FIG. 5 is a flowchart showing a failure determination process for the first clutch 51 executed by the drive command unit 102.

[0056] In step S1, the first motor 41 is driven, and in step S2, it is determined whether the first transport sensor 61 is turned on. If it is not on (NO in step S2), it waits until it is turned on. If it is on (YES in step S2), the first motor 41 is stopped in step S3. In step S4, it is determined whether the time required for paper gap control (T2 in FIG. 4) has elapsed, and if it has not elapsed (NO in step S4), it waits until it has elapsed. If it has elapsed (YES in step S4), the second motor 42 is driven in step S5.

[0057] Next, in step S6, it is checked whether the speed of the first motor 41 is greater than zero, and if it is zero (NO in step S6), normal drive control is executed in step S7. If the speed of the first motor 41 is greater than zero (YES in step S6), in other words, if the drive of the first motor 41 has not been instructed and the rotation of the first motor 41 has been detected, it is determined in step S8 that the first clutch 51 has failed.

[0058] 2 and 3, a brushless motor equipped with an encoder 41b is exemplified as the first motor 41, but a brushless motor equipped with a Hall element for detecting the position of the rotor may be used instead of the encoder 41b. In this case as well, a signal from the Hall element is transmitted to the speed control unit 105, and the speed control unit 105 transmits speed information to the failure determination unit 103 of the drive instruction unit 102, and the failure determination unit 103 can determine that the first motor 41 is rotating based on this information.

[0059] Furthermore, the first motor 41 does not have to be a brushless motor, and may be a stepping motor equipped with an encoder 41b or a Hall element, and the point is that it is sufficient if it is a motor that can determine whether it is rotating or not.

[0060] FIG. 6 is a block diagram showing the configuration of a control system for a first motor 41 and a second motor 42 in an image forming apparatus according to another embodiment of the present invention, and FIG. 7 is a schematic diagram showing the configurations of a first pair of transport rollers 31, a second pair of transport rollers 32, a first motor 41, a second motor 42, a first clutch 51 and a second clutch 52.

[0061] In this embodiment, the control system is the same as that shown in FIG. 2 except that a three-phase sensorless brushless motor (BLDCM) is used as the first motor 41 and that the first motor 41 is controlled by a sensorless vector control unit 110. The same components are given the same reference numerals and detailed descriptions are omitted.

[0062] A specific configuration of the sensorless vector control unit 110 is shown in the block diagram of FIG.

[0063] The sensorless vector control unit 110 includes a speed control unit 111, a current control unit 112, a coordinate conversion unit 113, a PWM conversion unit 114, a magnetic pole position estimation unit 116, an initial position estimation unit 117, and a coordinate conversion unit 118.

[0064] The speed control unit 111 receives the target speed ω * and the estimated speed ω of the magnetic pole (rotor) received from the magnetic pole position estimation unit 116. M From the difference between these, the current value (Iv*, Iδ*), i.e., the torque, is determined, and the current control unit 112 converts the determined current value (Iv*, Iδ*) into a voltage value (Vv*, Vδ*). The coordinate conversion unit 113 performs an inverse coordinate conversion from the rotating coordinate to the fixed coordinate, and obtains a three-phase input signal (Vu*, Vv*, Vw*) from the two-phase voltage obtained by the inverse coordinate conversion, and outputs it to the PWM conversion unit 114. The PWM conversion unit 114 converts the three-phase input signal (Vu*, Vv*, Vw*) into a three-phase pulse signal, determines a duty ratio, and outputs it to the three-phase inverter 115, which is a drive circuit for the motor 112. The three-phase inverter 115 drives the first motor 41 based on the pulse signal output from the PWM conversion unit 114. Note that the value marked with "*" indicates a target value (command value).

[0065] The coordinate conversion unit 118 converts the current (Iu, Iv) of the three-phase inverter detected by the shunt resistor into a two-phase current, and also converts it from fixed coordinates to rotating coordinates, and outputs it as a current value (Iv, Iδ).

[0066] A magnetic pole position estimation unit 116 estimates the magnetic pole position based on the current values ​​(Iv, Iδ) output from the coordinate conversion unit 118 and the voltage values ​​(Vv*, Vδ*) from the current control unit 112, and an initial position estimation unit 117 estimates the initial position of the magnetic pole.

[0067] In this way, the sensorless vector control unit 110 estimates the angle and speed of the magnetic pole rotor from the current and voltage, and therefore does not include a Hall element or an encoder.

[0068] Fig. 9(A) is an operation sequence diagram of the first and second motors 41, 42 in the embodiment shown in Figs. 6 to 8. In period T1, the first motor 41 is driven, the first clutch 51 is switched to a connected state, the first conveying roller pair 31 is rotationally driven via the first clutch 51, and the paper P is conveyed downstream to reach the second conveying roller pair 32. During this period, when the first conveying sensor 61 turns on, the rotation speed of the first motor 41 is reduced for a certain period of time for paper gap control. After the paper gap control is completed, when the second conveying sensor 62 turns on, the first motor 41 is stopped.

[0069] When the first motor 41 stops, the first clutch 51 is switched to a disconnected state, and the rotation of the first transport roller pair 31 also stops. When the paper gap control time T2 has elapsed after the first transport roller pair 31 stops, the second motor 42 is started and the second clutch 52 is switched to an engaged state, the second transport roller pair 32 is driven to rotate via the second clutch 52, and the paper P is transported further downstream. In this state, the first transport roller pair 31 rotates in conjunction with the transport of the paper, but because the first clutch 51 is in a disconnected state, the rotational force of the first transport roller pair 31 is not transmitted to the first motor 41.

[0070] However, if the first clutch 51 breaks down and a disconnection failure occurs, resulting in a constantly connected state, the first motor 41 rotates together with the first transport roller pair 31 via the first clutch 51 in association with paper transport by the rotational drive of the second transport roller pair 32, even though no instruction has been given to drive the first motor 41. This causes slippage between the second transport roller pair 32 and the paper P, increasing the load on the second motor 42, and the second motor 42 does not increase in rotation speed to the intended speed during the operation period T3 of the second motor 42.

[0071] Therefore, in this embodiment, even after the first motor 41 is stopped, voltage pulses with two different electrical angles and a relative electrical angle difference of 180 degrees are applied at regular time intervals. In this embodiment, voltage pulses with electrical angles of 0 degrees and 180 degrees are applied alternately as voltage pulses with a relative electrical angle difference of 180 degrees, and the peak current value is constantly monitored and measured. Period T4 in Fig. 9(A) shows a state in which voltage pulses with electrical angles of 0 degrees and 180 degrees are applied alternately.

[0072] When first clutch 51 is not at fault, first motor 41 is stopped, so the peak current value is approximately constant, as shown in Fig. 9(B). On the other hand, when first clutch 51 is at fault and an interruption failure occurs, the peak current value changes as shown in Fig. 9(C) due to the difference in electrical angle accompanying the rotation of the rotor.

[0073] Therefore, when there is a difference of a predetermined value or more in the current value for each applied pulse, the failure determination section 103 of the drive instruction section 102 can determine that the first motor 41 is rotating.

[0074] FIG. 10 is a flowchart showing a failure determination process for the first clutch 51 executed by the drive command unit 102 in the embodiment shown in FIGS.

[0075] In step S11, the first motor 41 is driven, and in step S12, it is determined whether the first transport sensor 61 is turned on. If it is not on (NO in step S12), it waits until it is turned on. If it is on (YES in step S12), the first motor 41 is stopped in step S13, and voltage pulses of electrical angles of 0 degrees and 180 degrees are applied alternately. In step S14, it is determined whether the time required for paper gap control (T2 in FIG. 10) has elapsed, and if it has not elapsed (NO in step S14), it waits until it has elapsed. If it has elapsed (YES in step S14), the second motor 42 is driven in step S15.

[0076] Next, in step S16, it is checked whether a predetermined difference has occurred in the peak current value of the first motor 41, and if a difference has occurred (YES in step S16), the speed of the first motor 41 is determined to be greater than zero in step S17, and since no instruction has been given to drive the first motor 41, it is determined in step S18 that the first clutch 51 has failed. If no predetermined difference has occurred in the peak current value of the first motor 41 in step S16 (NO in step S16), the speed of the first motor 41 is determined to be zero in step S19, and normal drive control is executed in step S20.

[0077] In the above embodiment, the first conveying roller pair 31 and the second conveying roller pair 32 are driven by different motors, the first motor 41 and the second motor 42. However, as shown in FIG. 11, the first conveying roller pair 31 and the second conveying roller pair 32 may be driven by a common first motor 41 via a first clutch 51 and a second clutch 52, respectively. In this case, even if the first clutch 51 is disconnected and the drive of the first conveying roller pair 31 is stopped, the first motor 41 is not necessarily stopped to drive the second conveying roller pair 32. Therefore, it is not possible to determine a failure of the first clutch 51 by detecting the rotation of the first motor 41.

[0078] For this reason, when two or more pairs of conveying rollers 31, 32 are driven by one first motor 1 in common, a rotation detector 120 is provided to detect the rotation of the first clutch 51, and when the rotation detector 120 detects the rotation of the first clutch 51 despite the first clutch 51 being instructed to switch to disconnect the first motor 41 and the first pair of conveying rollers 31, it is determined that the first clutch 51 is faulty. In the case of an electromagnetic clutch, for example, whether or not an instruction to switch to disconnect the first motor 41 and the first pair of conveying rollers 31 has been given to the first clutch 51 may be determined by whether or not a disconnection signal has been output to the electromagnetic clutch.

[0079] The failure determination based on the rotation detection of the clutch according to the embodiment of FIG. 11 may be applied to the case where the pairs of transport rollers 31, 32 are driven by separate motors 41, 42, respectively.

[0080] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. For example, the rotation of the motor when no command to drive the motor is given is detected by the encoder 41b, the Hall element, or the change in the peak current value in the case of a brushless sensorless motor, but other methods may be used.

[0081] As another method, in the case of a brushless motor in which a circuit pattern for generating induced voltage, called an FG pattern, is provided close to the rotor magnet, it is possible to detect that the motor is rotating by detecting the induced voltage generated in the FG pattern by the rotor's magnetic poles when the rotor rotates. Therefore, if induced voltage is generated in the FG pattern even though no command to drive the motor has been issued, it may be configured to determine that the clutch has failed.

[0082] As another method, in the case of a brushless motor or a stepping motor, it is possible to detect the occurrence of back electromotive force and thereby detect that the motor is rotating. Therefore, even if no command to drive the motor is given, a configuration may be adopted in which it is determined that the clutch has failed when back electromotive force is generated. [Explanation of symbols]

[0083] 1 Image forming device main body 2 Paper feed section 31 3rd stage vertical transport roller pair (first transport roller pair) 32 2nd stage vertical transport roller pair (second transport roller pair) 33 Timing Roller Pair 41 First Motor 41b Encoder 42 Second Motor 43 Third Motor 51 First Clutch 52 Second Clutch 61 First transport sensor 62 Second transport sensor 63 Timing Sensor 100 Transport control IC 101 Transport control section 102 Driving instruction unit 103 Failure determination section 105 Speed ​​control section 110 Sensor vector control unit 120 First motor (shared motor) P Paper

Claims

1. a pair of rotatable first transport rollers for transporting paper; a second transport roller pair located downstream in a paper transport direction as viewed from the first transport roller pair; a first driving means for driving the first pair of transport rollers to rotate; a second driving means for driving the second pair of transport rollers to rotate; a drive instruction means for instructing the first drive means and the second drive means to drive; a first connection means for connecting the first drive means and the first transport roller pair when the drive instruction means is instructing the first drive means to drive, and for disconnecting the first drive means and the first transport roller pair when the drive instruction means is not instructing the first drive means to drive; a second connection means for switching between connection and disconnection between the second driving means and the second transport roller pair; a rotation detection means for detecting the rotation of the first driving means; a determination means for determining whether the first connection means is faulty; Equipped with An image forming apparatus characterized in that, when a sheet of paper is straddled between the first transport roller pair and the second transport roller pair, the second connection means connects the second drive means to the second transport roller pair, and the drive instruction means instructs the second drive means to be driven so that the second transport roller pair transports the sheet, if the drive instruction means is not instructing the first drive means to drive and the rotation detection means detects the rotation of the first drive means, the judgment means judges that the first connection means is faulty.

2. 2. The image forming apparatus according to claim 1, wherein the first driving means is a brushless motor driven in a sensorless manner, and voltage pulses are applied at constant time intervals at a predetermined electrical angle, and when there is a difference of a predetermined value or more in a current value for each applied pulse, the rotation detection means detects the rotation of the first driving means.

3. 3. The image forming apparatus according to claim 2, wherein the voltage pulses of the predetermined electrical angle are pulses of two different electrical angles, the relative electrical angle difference being 180 degrees.

4. 2. The image forming apparatus according to claim 1, wherein the first driving means is a brushless motor or a stepping motor having an encoder, and the rotation detection means detects the rotation of the first driving means by detecting the rotation of the encoder.

5. 2. The image forming apparatus according to claim 1, wherein said first driving means is a brushless motor having an FG pattern, and said rotation detecting means detects the rotation of said first driving means based on a signal from said FG pattern.

6. 2. The image forming apparatus according to claim 1, wherein said first driving means is a brushless motor having a Hall element, and said rotation detecting means detects the rotation of said first driving means based on a signal from said Hall element.

7. 2. The image forming apparatus according to claim 1, wherein the first driving means is a brushless motor or a stepping motor, and the rotation detection means detects the rotation of the first driving means by generation of a back electromotive force in the brushless motor or the stepping motor.

8. The image forming apparatus according to any one of claims 1 to 7, wherein the first connecting means and the second connecting means are either a one-way clutch that switches between connection and disconnection by mechanical action, or an electromagnetic clutch that switches between connection and disconnection by electromagnetic action.

9. a pair of rotatable first transport rollers for transporting paper; a second transport roller pair located downstream in a paper transport direction as viewed from the first transport roller pair; a first driving means for driving the first pair of transport rollers to rotate; a second driving means for driving the second pair of transport rollers to rotate; a drive instruction means for instructing the first drive means and the second drive means to drive; a first connection means for connecting the first drive means and the first transport roller pair when the drive instruction means is instructing the first drive means to drive, and for disconnecting the first drive means and the first transport roller pair when the drive instruction means is not instructing the first drive means to drive; a second connection means for switching between connection and disconnection between the second driving means and the second transport roller pair; An image forming apparatus comprising: a drive instruction step of instructing the first drive means and the second drive means to drive; a rotation detection step of detecting rotation of the first driving means; a determining step of determining whether the first connecting means is faulty; Run A fault detection method characterized in that, when a sheet of paper is straddled between the first transport roller pair and the second transport roller pair, the second drive means and the second transport roller pair are connected by the second connection means, and the second drive means is driven by an instruction to drive the second drive means in the drive instruction step, and the second transport roller pair transports the sheet, if the first drive means is not instructed to drive and rotation of the first drive means is detected in the rotation detection step, the judgment step judges that the first connection means is faulty.

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