Motor abnormality detection device, motor drive system and image forming apparatus

Abstract

To reduce the circuit scale of a device that detects connection abnormality of a two-phase bipolar stepping motor to reduce system cost.SOLUTION: A motor abnormality detection device comprises: first and second resistance elements that are connected, via a connection mode, between a ground conductor and one of a first output terminal pair of a motor driver that drives a two-phase bipolar stepping motor; third and fourth resistance elements that are connected, via a connection node, between the ground conductor and one of a second output terminal pair of the motor driver; a capacitive element that is connected with the connection node; and an abnormality detection unit that, after a current for excitation is supplied to a first coil and a second coil, receives, at a voltage input terminal, a regenerative voltage generated in the connection node according to a regenerative voltage flowing in the coils supplied with the current, according to whether the received regenerative voltage is at a predetermined voltage, detects an abnormality in at least any one of the first coil and the second coil.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a motor abnormality detection device, a motor drive system, and an image forming apparatus. [Background technology]

[0002] Image forming devices such as MFPs (Multi-Function Printers) or laser printers have multiple stepping motors to rotate a transport roller that transports paper, a photosensitive drum, etc. For example, in a two-phase bipolar stepping motor, a method is known in which a connection anomaly is detected for each phase based on a voltage generated by a load connected to an output terminal corresponding to each phase of a motor driver when a regenerative current flows through a coil to which current is supplied. Summary of the Invention [Problem to be solved by the invention]

[0003] However, in the above method, the control chip that detects the connection abnormality has two voltage input terminals that respectively receive voltages generated by loads corresponding to the phases connected to the output terminals of the motor driver. The control chip also includes two ADCs (Analog-to-Digital Converters) that convert the voltages received at the voltage input terminals into digital values. This increases the chip size of the control chip, which increases the cost of the device in which the two-phase bipolar stepping motor is installed.

[0004] The disclosed technology has been made in consideration of the above-mentioned problems, and aims to reduce the circuit scale of a device for detecting connection abnormalities in a two-phase bipolar stepping motor, thereby reducing system costs. [Means for solving the problem]

[0005] In order to solve the above technical problem, a motor abnormality detection device according to one aspect of the present invention includes a motor driver that drives a two-phase bipolar stepping motor including a first coil and a second coil, and includes a first resistive element and a second resistive element that are connected in series via a connection node between one of a first output terminal pair connected to both ends of the first coil in the motor driver and a ground line, a third resistive element and a fourth resistive element that are connected in series via the connection node between one of a second output terminal pair connected to both ends of the second coil in the motor driver and a ground line, and a capacitive element having one end connected to the connection node and the other end connected to the ground line, and a regenerative voltage generated at the connection node in response to a regenerative current flowing through the coil that has been supplied with the current after an excitation current is supplied to each of the first coil and the second coil. One The regenerative voltage is received at a voltage input terminal, and an abnormality detection unit detects an abnormality in at least one of the first coil and the second coil depending on whether the received regenerative voltage is at a predetermined voltage. Effect of the Invention

[0006] The circuit scale of a device for detecting connection abnormalities in a two-phase bipolar stepping motor can be reduced, thereby reducing system costs. [Brief description of the drawings]

[0007] [Figure 1] 1 is a block diagram showing an example of a motor drive system including a motor abnormality detection device according to a first embodiment of the present invention. [Diagram 2] 2 is an explanatory diagram showing an example of a current flowing through an H-bridge circuit when a stepping motor is driven by the motor drive system of FIG. 1. [Diagram 3] 3 is a waveform diagram showing an example of a current flowing through an output terminal and a voltage generated at the output terminal when the stepping motor of FIG. 2 is driven. [Figure 4] 2 is a side view showing an example of an image forming apparatus including the motor drive system of FIG. 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, the embodiments will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and duplicated descriptions may be omitted.

[0009] (First embodiment) 1 is a block diagram showing an example of a motor drive system including a motor abnormality detection device according to a first embodiment of the present invention. For example, the motor drive system 110 shown in FIG. 1 includes a microcomputer 120, a driver IC (Integrated Circuit) 130, a two-phase bipolar stepping motor 140, resistive elements R1, R2, R3, R4, R5, R6, and a capacitive element C1. Double square marks around the microcomputer 120 and the driver IC 130 indicate external terminals. Hereinafter, the two-phase bipolar stepping motor 140 is also simply referred to as a stepping motor 140.

[0010] The microcomputer 120 controls the driver IC 130 and controls the rotation of the stepping motor 140 by executing a motor drive program using a CPU (Central Processing Unit) not shown. The microcomputer 120 is an example of a control unit that controls the stepping motor 140 via the driver IC 130. The microcomputer 120 has an ADC 124 and an abnormality detection unit 122. The ADC 124 converts an analog voltage received at a voltage input terminal SC into a digital value, and outputs the converted digital value to the abnormality detection unit 122.

[0011] The abnormality detection unit 122 detects an abnormality in the stepping motor 140 based on the received digital value. Here, the abnormality in the stepping motor 140 is not limited to an abnormality in the stepping motor 140 itself. The abnormality in the stepping motor 140 includes an abnormality in the stepping motor 140 due to a failure in the driver IC 130, or an abnormality in the connector or harness that connects the driver IC 130 and the stepping motor 140. An abnormality in the stepping motor 140 itself is a break in the motor windings, etc. An abnormality in the connector or harness is a disconnected connector or a disconnected harness, etc.

[0012] The resistor R1 is an example of a first resistor, and the resistor R2 is an example of a second resistor. The resistor R3 is an example of a third resistor, and the resistor R4 is an example of a fourth resistor. The resistors R1, R2, R3, and R4, the capacitor C1, and the abnormality detector 122 are an example of a motor abnormality detector.

[0013] The driver IC 130 includes a logic circuit 132 and H-bridge circuits 134 and 136. The driver IC 130 is an example of a motor driver. The driver IC 130 outputs control signals S (S1, S2, S3, S4, S5, S6, S7, S8) based on a clock signal CLK and control signals CW_CCW, ENABLE, and RESET received from the microcomputer 120. The control signal CW_CCW is used to control the rotation direction of the stepping motor 140. The control signal ENABLE is used for enable control. The control signal RESET is used for reset control.

[0014] The H-bridge circuit 134 has a p-channel MOS transistor PM1 and an n-channel MOS transistor NM1 connected in series between the drive power supply line Vm and the ground line GND. The H-bridge circuit 134 also has a p-channel MOS transistor PM2 and an n-channel MOS transistor NM2 connected in series between the drive power supply line Vm and the ground line GND. Hereinafter, the p-channel MOS transistor and the n-channel MOS transistor will be simply referred to as transistors.

[0015] In the H-bridge circuit 134, the gate of the transistor PM1 receives a control signal S1. The gate of the transistor PM2 receives a control signal S2. The gate of the transistor NM1 receives a control signal S3. The gate of the transistor NM2 receives a control signal S4. The drains of the transistor PM1 and the transistor NM1 are connected to an output terminal OUT1A. The drains of the transistor PM2 and the transistor NM2 are connected to an output terminal OUT1B. For example, the output terminals OUT1A and OUT1B are respectively connected to both ends of a coil L1 corresponding to one of the phases of the stepping motor 140. The coil L1 is an example of a first coil.

[0016] The H-bridge circuit 134 controls the current flowing through the transistors PM1, PM2, NM1, and NM2 that operate in response to control signals S1-S4, and outputs a voltage for exciting the coil L1 from the output terminals OUT1A and OUT1B to the coil L1. The output terminals OUT1A and OUT1B are an example of a first output terminal pair.

[0017] In the H-bridge circuit 136, the gate of the transistor PM1 receives a control signal S5. The gate of the transistor PM2 receives a control signal S6. The gate of the transistor NM1 receives a control signal S7. The gate of the transistor NM2 receives a control signal S8. The drains of the transistor PM1 and the transistor NM1 are connected to an output terminal OUT2A. The drains of the transistor PM2 and the transistor NM2 are connected to an output terminal OUT2B. For example, the output terminals OUT2A and OUT2B are respectively connected to both ends of a coil L2 corresponding to another one of the phases of the stepping motor 140. The coil L2 is an example of a second coil.

[0018] The H-bridge circuit 136 controls the current flowing through the transistors PM1, PM2, NM1, and NM2 operated by the control signals S5-S8, and outputs a voltage for exciting the coil L1 from the output terminals OUT2A and OUT2B to the coil L1. The output terminals OUT2A and OUT2B are an example of a second output terminal pair.

[0019] Resistance elements R1 and R2 connected in series via a connection node CN are disposed between the output terminal OUT1B (i.e., one end of the coil L1) and the ground line GND. Resistance elements R3 and R4 connected in series via a connection node CN are disposed between the output terminal OUT2B (i.e., one end of the coil L2) and the ground line GND. The connection node CN is connected to the input of the ADC 124 via a voltage input terminal SC of the microcomputer 120.

[0020] In addition, a capacitance element C1 is disposed between the connection node CN and the ground line. The resistance elements R1, R2, R3, and R4 and the capacitance element C1 function as a voltage detection unit that detects a regenerative voltage generated at the connection node CN by a regenerative current due to a fast decay operation described later.

[0021] In the driver IC 130, a current detection terminal RNF1 connected to the sources of the transistors NM1 and NM2 of the H-bridge circuit 134 and the logic circuit 132 is connected to the ground line GND via a resistor R5. A current detection terminal RNF2 connected to the sources of the transistors NM1 and NM2 of the H-bridge circuit 136 and the logic circuit 132 is connected to the ground line GND via a resistor R6.

[0022] The logic circuit 132 detects the output current Io flowing through the stepping motor 140 during the fast decay period via the current detection terminals RNF1 and RNF2. Then, the logic circuit 132 performs chopping control so that the output current Io becomes equal to or smaller than the maximum output current Iomax. Here, the chopping control is a control that turns on or off the transistors PM1, PM2, NM1, and NM2, respectively, and excites the coils L1 and L2, respectively.

[0023] Fig. 2 is an explanatory diagram showing an example of a current flowing in the H-bridge circuit 134 (or 136) when the stepping motor 140 is driven by the motor drive system 110 in Fig. 1. The solid arrows in the H-bridge circuit 134 (or 136) indicate a current path until the current flowing when exciting the coil L1 (or coil L2) (when the output is ON) in chopping control reaches a target current (Iomax in Fig. 3). At this time, the transistors PM1 and NM2 are turned on, and the transistors PM2 and NM1 are turned off.

[0024] The dashed arrows in the H-bridge circuit 134 (or 136) indicate the current paths when the current is attenuated (fast decay operation) after reaching the target current in chopping control. That is, the dashed arrows indicate the current paths of the regenerative current. At this time, the transistors PM1 and NM2 are turned off, and the transistors PM2 and NM1 are turned on. Note that, during current decay, the transistor PM2 may be maintained in the off state. The fast decay operation is an operation in which, after an excitation current is supplied to the coil L1 or coil L2, a regenerative current is caused to flow through the coil that supplied the current.

[0025] Fig. 3 is a waveform diagram showing an example of the output current Io flowing through the output terminal OUT1B (or OUT2B) and the voltage V generated at the output terminal OUT1B (or OUT2B) when the stepping motor 140 in Fig. 2 is driven. Note that the current waveform in Fig. 3 is also the current flowing through the coil L1 (or coil L2) of the stepping motor 140.

[0026] The period Tchop indicates the chopping control cycle, which is the period from the start of supply of excitation current to coil L1 or coil L2 to the completion of the current decay period during which regenerative current flows, and is indicated by the sum of the periods Ton and Tfd. The period Ton indicates the output-on period (when the output is ON) during which excitation current flows through the current path indicated by the solid line in FIG. 2. The period Tfd (first decay operation period) indicates the current decay period during which regenerative current flows through the current path indicated by the dashed line in FIG. 2. When regenerative current flows through the current path indicated by the dashed line in FIG. 2 (Tfd period), a regenerative voltage is generated at the connection node CN connected to the output terminal OUT1B (OUT2B) via the resistive elements R1 and R3. The regenerative voltage is generated by integrating the regenerative current flowing through the connection node CN using an integrating circuit (resistive elements R1, R2, R3, R4 and capacitive element C1).

[0027] 1 detects the regenerative voltage as a digital value via the ADC 124, and detects abnormalities such as disconnection of one or both of the coils L1 and L2 of the stepping motor 140. As described above, detection of abnormalities in the coils L1 or L2 includes detection of a failure of the driver IC 130 and abnormalities in the signal line connecting the driver IC 130 and the stepping motor 140 (such as a disconnected connector or a disconnected harness).

[0028] For example, the abnormality detection unit 122 detects an abnormality in the coil L1 when the acquired regenerative voltage Vd satisfies formula (1). The abnormality detection unit 122 detects an abnormality in the coil L2 when the acquired regenerative voltage Vd satisfies formula (2). Moreover, the abnormality detection unit 122 detects abnormalities in both the coil L1 and the coil L2 when the acquired regenerative voltage Vd satisfies formula (3). Furthermore, the abnormality detection unit 122 detects that both the coil L1 and the coil L2 are normal when the acquired regenerative voltage Vd satisfies formula (4).

[0029] In formulas (1) to (4), R1 indicates the resistance value of the resistive element R1, and R2 indicates the resistance value of the resistive element R2. R3 indicates the resistance value of the resistive element R3, and R4 indicates the resistance value of the resistive element R4. Vm indicates the voltage of the driving power supply for the stepping motor 140. Ra indicates the resistance value of the coil L1, and Rb indicates the resistance value of the coil L2. Vα indicates a ripple voltage measured in advance. The ripple voltage is generated, for example, by a conversion error of the ADC 124, the motor winding resistance of the stepping motor 140, and an integrating circuit formed by the resistive elements R1, R2, R3, and R4 and the capacitive element C1.

[0030] Vd=Vm×{1 / (1 / R2+1 / R4)} / [{1 / (1 / R2+1 / R4)}+Rb+R3)]×Tfd / Tchop±Vα‥(1) Vd=Vm×{1 / (1 / R2+1 / R4)} / [{1 / (1 / R2+1 / R4)}+Ra+R1)]×Tfd / Tchop±Vα‥(2) Vd = Vα (3) Vd=Vm×{1 / (1 / R2+1 / R4)} / [{1 / (1 / R2+1 / R4)}+{1 / (1 / (Ra+R1)+1 / (Rb+R3))}]×Tfd / Tchop±Vα‥(4)

[0031] As shown in equations (1) and (2), the abnormality detection unit 122 receives at the voltage input terminal SC a regenerative voltage generated at the connection node CN by the regenerative current, and detects an abnormality in at least one of the coils L1 and L2 depending on whether the received regenerative voltage is a predetermined voltage. In other words, the abnormality detection unit 122 differentiates the value of the regenerative voltage Vd used to detect an abnormality in the coil L1 from the value of the regenerative voltage Vd used to detect an abnormality in the coil L2.

[0032] The resistance elements R1, R2, R3, and R4 are set to resistance values ​​that allow the abnormality detection unit 122 to identify an abnormality in one of the coils L1 and L2, an abnormality in both of them, or a normality in both of them based on the regenerative voltage Vd. In this way, the abnormality detection unit 122 can detect the abnormalities in the coils L1 and L2 individually based on the regenerative voltage received at one voltage input terminal SC. Therefore, it is possible to reduce the circuit scale of the device that detects the connection abnormality of the two-phase bipolar stepping motor 140, and to reduce the system cost.

[0033] Fig. 4 is a side view showing an overview of an image forming apparatus 100 including the motor drive system 110 of Fig. 1. The image forming apparatus 100 shown in Fig. 5 is included in a multifunction peripheral such as an MFP (Multi-Function Peripheral) having a copy function, a printer function, a scanner function, a fax function, etc. The multifunction peripheral can also communicate with an external device such as a PC (Personal Computer), and can also perform an operation according to an instruction received from the external device. Fig. 5 shows a part of the multifunction peripheral in a see-through manner.

[0034] The multifunction peripheral includes a paper feed table 200 disposed below the image forming apparatus 100, and an image reading unit 300 and an automatic document feeder (ADF: Auto Document Feeder) 400 disposed above the image forming apparatus 100.

[0035] The image forming apparatus 100 has an intermediate transfer unit disposed at the center, which is provided with an intermediate transfer belt 10, which is an endless belt. The intermediate transfer belt 10 is wound around three support rollers 14, 15, and 16, and rotates clockwise. The image forming apparatus 100 has an intermediate transfer body cleaning unit 17 on the left side of the support roller 16. The intermediate transfer body cleaning unit 17 has a function of removing residual toner remaining on the intermediate transfer belt 10 after a toner image (image) is transferred to the intermediate transfer belt 10.

[0036] The image forming apparatus 100 has an image forming device 20 on the intermediate transfer belt 10 between support rollers 14 and 15. The image forming device 20 has, along the clockwise movement direction of the intermediate transfer belt 10, photoconductor units 40 for each of the colors of black (K), yellow (Y), magenta (M) and cyan (C), a charger unit 18, a developing unit and a cleaning unit.

[0037] The imaging device 20 includes, for example, an IC tag, and is detachably attached to the main body of the image forming apparatus 100. The image forming apparatus 100 has a writing unit 21 above the imaging device 20. The writing unit 21 irradiates the photosensitive drums of the photosensitive units 40 of each color with laser light for forming an image. For example, the above-mentioned motor drive system 110 is applied to a drum drive motor system that rotates and drives the photosensitive drums of each color.

[0038] The image forming apparatus 100 has a secondary transfer unit 22, which is an endless belt stretched between two rollers 23, below the intermediate transfer belt 10. The secondary transfer unit 22 is disposed at a position where it pushes up the lower side of the intermediate transfer belt 10 and presses it against a support roller 16. The secondary transfer belt 24 transfers the toner image formed on the intermediate transfer belt 10 onto paper. The paper is an example of a recording medium.

[0039] The image forming apparatus 100 has a fixing unit 25 to which the paper onto which the toner image has been transferred is fed, on the side of the secondary transfer unit 22. The fixing unit 25 has a fixing belt 26, which is an endless belt, and a heating and pressure roller 27 that is pressed against the fixing belt 26. The image transferred onto the paper is fixed onto the paper by the heating and pressure roller 27.

[0040] The image forming apparatus 100 has a sheet inverting unit 28 below the secondary transfer unit 22 and the fixing unit 25. The sheet inverting unit 28 has a function of inverting and sending out the paper so that an image can be formed on the back side of the paper immediately after an image has been formed on the front side.

[0041] When a user or the like presses a start switch on an operation unit (not shown) with a document on the document feed tray 30 of the automatic document feeder 400, the automatic document feeder 400 transports the document onto the contact glass 32. The scanner of the image reading unit 300 is driven when the start switch is pressed with no document on the document feed tray 30. The driven scanner reads and scans the first carriage 33 and the second carriage 34 to scan the document placed on the contact glass 32.

[0042] Thereafter, light is irradiated onto the contact glass 32 from a light source on the first carriage 33, and the light reflected from the surface of the document is reflected by a first mirror on the first carriage 33 toward the second carriage 34. The light reflected from the document is then reflected by a mirror on the second carriage 34 toward an imaging lens 35, and an image is formed on the reading sensor 36 through the imaging lens 35. For example, the reading sensor 36 is a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor. The scanner generates recording data for each color based on the image signal acquired by the reading sensor 36.

[0043] When the start switch is pressed, the image forming apparatus 100 starts rotating the intermediate transfer belt 10 and starts preparation for image formation for each unit of the image forming device 20. Then, the image forming apparatus 100 starts the image forming process for each color, projecting an exposure laser modulated based on the recording data for each color onto the photosensitive drum for each color. Through the image forming process for each color, the toner images of each color are transferred sequentially onto the intermediate transfer belt 10 as a single image and are superimposed.

[0044] The leading edge of the paper is sent into the secondary transfer unit 22 in time with the leading edge of the superimposed toner images entering the secondary transfer unit 22. This causes the toner image on the intermediate transfer belt 10 to be transferred onto the paper. The paper onto which the toner image has been transferred is transported to the fixing unit 25, where the toner image is fixed onto the paper.

[0045] When the image forming apparatus 100 transfers an image onto paper, the image forming apparatus 100 selectively rotates one of the paper feed rollers 42 of the paper feed table 200. As a result, paper is fed from one of the multiple paper feed trays 44 provided in the paper feed unit 43, and only one sheet is separated by the separation roller 45 and sent to the paper feed path 46.

[0046] The paper fed into the paper feed path 46 is transported by transport rollers 47 and guided to a transport roller unit 48 in the image forming apparatus 100. When the paper hits registration rollers 49 of the transport roller unit 48, the transport is temporarily stopped, and the paper is then sent to the secondary transfer unit 22.

[0047] Paper can also be fed from manual feed tray 51 of image forming apparatus 100. When paper is set in manual feed tray 51 by a user, image forming apparatus 100 rotates and drives paper feed roller 50 when a start switch is pressed. As a result, one sheet of paper set in manual feed tray 51 is separated by separation roller 52 and pulled into manual feed path 53, where it hits registration roller 49 and stops. For example, the above-mentioned motor drive system 110 is applied to a DC motor system that drives transport roller 47.

[0048] The paper feed table 200 has various sensors including, for example, a photo sensor. For example, the various sensors are a paper end sensor, a size detection sensor, a tray set detection sensor, a paper transport sensor, etc. The paper end sensor detects the remaining amount and presence of paper stored in the paper feed tray 44. The size detection sensor detects the size and orientation of the paper. The tray set detection sensor detects whether each paper feed tray 44 is attached to the paper feed table 200. The paper transport sensor is provided in each paper feed tray 44 and detects whether paper is being transported properly and whether a transport jam (paper jam) has occurred.

[0049] The paper that has been subjected to the fixing process in the fixing unit 25 is guided by the switching claw 55 to the discharge rollers 56 and stacked on the paper output tray 57. Alternatively, the paper that has been subjected to the fixing process is guided by the switching claw 55 to the sheet reversing unit 28, after which the transport direction is reversed and the paper is transported again to the transfer position. After the paper that has been transported to the transfer position has an image recorded on the back side, it is discharged by the discharge rollers 56 onto the paper output tray 57.

[0050] Residual toner remaining on the intermediate transfer belt 10 after the image is transferred is removed by an intermediate transfer body cleaning unit 17. The registration rollers 49 may be grounded, or a bias voltage may be applied to them to remove paper dust from the paper.

[0051] The surface of the paper after passing through the registration roller 49 to which a bias voltage is applied is slightly negatively charged. Therefore, the conditions for transferring the toner image on the intermediate transfer belt 10 to the sheet may change compared to when no voltage is applied to the registration roller 49, and it may be necessary to change the transfer conditions. Therefore, a voltage of about -800V is applied to the side (front side) of the intermediate transfer belt 10 to which the toner image is transferred, and a voltage of about +200V is applied by the transfer roller 62 to the back side of the paper.

[0052] For example, by applying the stepping motor 140 of the motor drive system 110 of Fig. 1 to a drum drive motor that rotates a photosensitive drum or a DC motor that drives the transport roller 47, it is possible to detect abnormalities in the stepping motor 140 in detail. Specifically, it is possible to detect abnormalities in each phase of the stepping motor 140 using a minimum number of voltage input terminals.

[0053] The motor connection detection device and motor drive system of this embodiment may be applied to devices other than the above-mentioned image forming device 100. For example, the motor connection detection device and motor drive system of this embodiment may be applied to various devices having a rotation drive system, such as automobiles, robots, and amusement machines. In addition, the motor connection detection device and motor drive system of this embodiment may be used to drive a conveying roller of a conveying device that conveys prepregs, plastic sheets, banknotes, and the like.

[0054] As described above, in this embodiment, the motor drive system 110 and the image forming apparatus 100 can individually detect abnormalities in the coils L1 and L2 based on the voltage (regenerative voltage) generated at the connection node CN during the fast decay operation. At this time, the abnormality detection unit 122 can individually detect abnormalities in the coils L1 and L2 based on the regenerative voltage received at one voltage input terminal SC. Therefore, it is possible to reduce the circuit scale of the device that detects the connection abnormality of the two-phase bipolar stepping motor 140, and to reduce the system cost.

[0055] Although the present invention has been described above based on the embodiments, the present invention is not limited to the requirements shown in the above embodiments. These points can be changed without departing from the spirit of the present invention, and can be appropriately determined according to the application form. [Explanation of symbols]

[0056] 100 Image forming device 110 Motor Drive System 120 Microcomputer 122 Anomaly detection unit 124 ADC 130 Driver IC 132 Logic Circuits 134, 136 H-bridge circuit 140 2-phase bipolar stepping motor 200 Paper feed table 300 Image reading unit 400 Automatic document feeder C1 Capacitive element CLK Clock signal CN Connection Node CW_CCW control signal L1, L2 coils NM1, NM2 n-channel MOS transistor OUT1A, OUT1B output terminals OUT2A, OUT2B output terminals PM1, PM2 p-channel MOS transistors R1, R2, R3, R4, R5, R6 resistance elements RESET control signal RNF1, RNF2 Current detection terminals S1, S2, S3, S4 control signals S5, S6, S7, S8 control signals Tchop Chopping control period Tfd Current decay period Ton Output on period Vd Regenerative voltage Vm Drive power line [Prior art documents] [Patent documents]

[0057] [Patent Document 1] JP 2017-156246 A

Claims

1. a motor driver for driving a two-phase bipolar stepping motor including a first coil and a second coil, the motor driver including: a first resistor element and a second resistor element connected in series between one of a first output terminal pair connected to both ends of the first coil and a ground line via a connection node; a third resistor element and a fourth resistor element connected in series between one of a second output terminal pair connected to both ends of the second coil in the motor driver and a ground line via the connection node; a capacitance element having one end connected to the connection node and the other end connected to a ground line; an abnormality detection unit that receives, at one voltage input terminal, a regenerative voltage generated at the connection node in response to a regenerative current flowing through the coil to which the current has been supplied after an excitation current has been supplied to each of the first coil and the second coil, and detects an abnormality in at least one of the first coil and the second coil in response to whether the received regenerative voltage is at a predetermined voltage value; A motor abnormality detection device comprising:

2. The abnormality detection unit makes a predetermined voltage value used for detecting an abnormality in the first coil different from a predetermined voltage value used for detecting an abnormality in the second coil.

2. The motor abnormality detection device according to claim 1 .

3. The first resistance element, the second resistance element, the third resistance element, and the fourth resistance element are set to resistance values ​​that enable an abnormality in the first coil, an abnormality in the second coil, and an abnormality in both the first coil and the second coil to be identified based on the regenerative voltage.

3. The motor abnormality detection device according to claim 1 or 2,

4. When the resistance value of the first resistor element is R1, the resistance value of the second resistor element is R2, the resistance value of the third resistor element is R3, the resistance value of the fourth resistor element is R4, the voltage of the drive power supply of the two-phase bipolar stepping motor is Vm, the resistance value of the first coil is Ra, the resistance value of the second coil is Rb, the period from the start of the supply of excitation current to the first coil and the second coil to the end of the current decay period during which a regenerative current flows is Tchop, the current decay period is Tfd, the regenerative voltage detected by the abnormality detection unit is Vd, and the ripple voltage measured in advance is Vα, then The abnormality detection unit is An abnormality in the first coil is detected when the regenerative voltage Vd satisfies the formula (1), 4. The motor abnormality detection device according to claim 3, wherein an abnormality in the second coil is detected when the regenerative voltage Vd satisfies the formula (2). Vd=Vm×{1 / (1 / R2+1 / R4)} / [{1 / (1 / R2+1 / R4)}+Rb+R3)]×Tfd / Tchop±Vα‥(1) Vd=Vm×{1 / (1 / R2+1 / R4)} / [{1 / (1 / R2+1 / R4)}+Ra+R1)]×Tfd / Tchop±Vα‥(2)

5. 5. The motor abnormality detection device according to claim 4, wherein the abnormality detection unit detects abnormalities in both the first coil and the second coil when the regenerative voltage Vd satisfies equation (3). Vd = Vα (3)

6. 6. The motor abnormality detection device according to claim 4, wherein the abnormality detection unit determines that the first coil and the second coil are normal when the regenerative voltage Vd satisfies equation (4). Vd=Vm×{1 / (1 / R2+1 / R4)} / [{1 / (1 / R2+1 / R4)}+{1 / (1 / (Ra+R1)+1 / (Rb+R3))}]×Tfd / Tchop±Vα‥(4)

7. The two-phase bipolar stepping motor; The motor driver; a control unit including the motor abnormality detection device according to any one of claims 1 to 6 and controlling the two-phase bipolar stepping motor via the motor driver; A motor drive system comprising:

8. A motor drive system according to claim 7; A recording medium is conveyed by a conveying roller. a photosensitive drum on which a toner image to be transferred to the recording medium is formed; Equipped with At least one of the transport roller and the photosensitive drum is driven by the two-phase bipolar stepping motor. An image forming apparatus comprising:

Images