Motor control device and fault detection method

Abstract

The invention relates to a motor control device and a fault detection method. A motor controller for a plurality of motors connected in parallel has a single control unit, a single motor drive circuit, a plurality of shunt resistors connected to current paths of the respective motors, and a plurality of voltage detection circuits for detecting voltages of the shunt resistors. When the motor is in a forward direction, the control unit detects a fault in each motor current path based on a comparison of a voltage across each shunt resistor detected by the voltage detection circuit with a preset first threshold value. When the motor is reversed, the control unit detects a fault in each motor current path on the basis of a result of comparison of the voltage across the two ends of each shunt resistor detected by the voltage detection circuit with a preset second threshold value.

Description

Technical Field

[0001] One or more embodiments of the present invention relate to a control device of a motor for opening or closing a tailgate at the rear of a vehicle, and more particularly, to detecting an open circuit fault in a current path of the motor. Background Art

[0002] Fig.13 is a schematic diagram of an electric tailgate. Fig.13 As shown, a tailgate 51 is provided at the rear of a vehicle Z such as a four-wheel vehicle. The upper end of the tailgate 51 is supported on a shaft 52 provided on the vehicle body 50. The tailgate 51 swings around the shaft 52 in the opening direction X or the closing direction Y. The fully closed position of the tailgate is indicated by the reference numeral 51a. The half-open position of the tailgate is indicated by the reference numeral 51b. The fully open position of the tailgate is indicated by the reference numeral 51c. The tailgate 51 is driven by a motor, which is rotated by the operation of an operating switch, which is not shown in the figure.

[0003] Fig.14 : is a simplified view of a driving mechanism 60 for driving the tailgate 51. The driving mechanism 60 is located between the vehicle body 50 and the tailgate 51. The driving mechanism 60 has a cylindrical body 61, a motor 62 accommodated in the body 61, an arm 63 that moves in a direction "a" or "b" according to the rotation direction of the motor 62, and a conversion mechanism 64 that converts the rotational motion of the motor 62 into a linear motion of the arm 63. One end of the body 61 is connected to the vehicle body 50. One end of the arm 63 is connected to the tailgate 51. The other end of the arm 63 is connected to the conversion mechanism 64.

[0004] When the motor 62 rotates forward, the arm 63 moves in the direction "a" by the conversion mechanism 64 associated with the rotation. Therefore, the tailgate 51 is pushed upward by the arm 63 and swings in the opening direction X, so that the tailgate 51 is opened. When the motor 62 rotates reversely, the arm 63 moves in the direction "a" by the conversion mechanism 64 associated with the rotation. As a result, the tailgate 51 is pulled downward by the arm 63 and swings in the closing direction Y, causing the tailgate 51 to be closed.

[0005] Fig.15 is a rear view of the vehicle Z. A pair of drive mechanisms 60 are provided on both sides of the tailgate 51. In other words, a pair of motors 62 as a drive source for the tailgate 51 are provided on the left and right sides of the vehicle Z. This increases the drive force to the tailgate 51 and reduces the deflection of the tailgate 51 by balancing the drive force on both sides.

[0006] JP-A-H05-344788, JP-A-2020-78199, WO-A1-2020 / 179041 and JP-A-2000-166294 disclose a device in which a plurality of motors for operating one or more objects are driven by a single drive circuit or controlled by a single control circuit. JP-A-2017-172301, JP-A-2017-141577, JP-A-2021-38532, JP-A-2021-139138 disclose a device in which two motors for opening or closing a tailgate are controlled by a single control circuit. In a device equipped with a plurality of motors, it is known to measure the voltage at both ends of a shunt resistor connected in series with each motor as a method for detecting an open circuit fault occurring in the current path of the motor. For example, WO-A1-2020 / 179041 discloses such a method for detecting an open circuit fault. In this case, if each motor rotates in only one direction, a unidirectional current flows through each shunt resistor. Therefore, an open circuit fault can be detected by a simple method of comparing the voltage across each shunt resistor with a preset threshold. Summary of the invention

[0007] If each motor rotates forward or reverse, the direction of the current flowing through each shunt resistor during rotation is opposite. Therefore, the voltage across each shunt resistor is also different between forward rotation and reverse rotation, so the same method for a motor rotating in one direction cannot accurately detect an open circuit fault.

[0008] An object according to one or more embodiments of the present invention is to accurately detect a fault in a current path of a motor in the case of forward rotation or reverse rotation of the motor in an apparatus for controlling forward or reverse rotation of the motor.

[0009] According to one aspect of the present invention, there is provided a motor control device for parallel-connected motors, the motor control device comprising: a single motor drive circuit that drives a plurality of motors to rotate forward or reversely; a single control unit that outputs a control signal for controlling the rotation of each motor to the motor drive circuit; a plurality of shunt resistors that are provided between each of the motors and the motor drive circuit; and a plurality of voltage detection circuits that detect the voltage across each of the shunt resistors. When the control signal is a forward command for each motor, the control unit compares the detected voltage across each shunt resistor with a preset first threshold value to detect a fault in a current path of each motor, and when the control signal is a reverse command for each motor, the control unit compares the detected voltage across each shunt resistor with a preset second threshold value to detect a fault in a current path of each motor.

[0010] According to one or more embodiments of the present invention, a motor control apparatus is provided with a single control unit and a single motor drive circuit, thereby individually detecting a fault in a current path of each motor during forward or reverse rotation of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is the block diagram of the motor controller.

[0012] Figure 2 is a circuit diagram showing a motor drive circuit.

[0013] Figure 3 is a circuit diagram showing a first voltage detection circuit.

[0014] Figure 4 is a diagram of the motor current path under normal conditions when the motor is rotating in the forward direction.

[0015] Figure 5 is a diagram of the motor current path under normal circumstances when the motor rotates in the reverse direction.

[0016] Figure 6 is a motor current path diagram under an open circuit fault in the first motor system when the motor rotates forward.

[0017] Figure 7 is a diagram of the motor current path under an open circuit fault in the first motor system when the motor rotates in the reverse direction.

[0018] Figure 8 is a motor current path diagram under an open circuit fault in the second motor system when the motor rotates forward.

[0019] Fig. 9 is a diagram of the motor current path under an open circuit fault in the second motor system when the motor rotates in the reverse direction.

[0020] Fig. 10A is a graph showing the relationship between the two thresholds and the detection voltage.

[0021] Fig. 10B is a diagram showing the detection voltage on the H-bridge circuit.

[0022] Fig.11 is a table showing criteria for detecting an open circuit failure.

[0023] Fig.12 is a flow chart showing fault detection.

[0024] Fig.13 is a schematic diagram of the tailgate.

[0025] Fig.14is a simplified view of the tailgate drive mechanism.

[0026] Fig.15 is the rear view of the vehicle. DETAILED DESCRIPTION

[0027] In embodiments of the present invention, many specific details are described to provide a thorough understanding of the present invention. However, it is apparent to one of ordinary skill in the art that the present invention can be practiced without these specific details. In other cases, well-known features are not described in detail to avoid obscuring the present invention.

[0028] Embodiments of the present invention will be described with reference to the accompanying drawings. In each of the drawings, the same or corresponding components are marked with the same symbols.

[0029] Figure 1 1 is a block diagram of a motor control device. The motor control device 100 controls the rotation of the first motor 3 and the second motor 4. Both the motor 3 and the motor 4 are direct current (DC) motors capable of forward or reverse rotation. Both the motor 3 and the motor 4 are turned on or off. Figures 13 to 15 The rear baffle 51 shown. For example, the first motor 3 corresponds to Fig.15 The left motor 62 in the second motor 4 corresponds to Fig.15 The right motor 62 in.

[0030] The motor control device 100 includes a single control unit 1 , a single motor drive circuit 2 , a first shunt resistor 5 , a second shunt resistor 6 , a first voltage detection circuit 7 , and a second voltage detection circuit 8 .

[0031] When the first motor 3 rotates forward, the motor drive circuit 2 causes the motor current to flow in direction A. When the first motor 3 rotates reversely, the motor drive circuit 2 causes the motor current to flow in direction B. Similarly, when the second motor 4 rotates forward, the motor drive circuit 2 causes the motor current to flow in direction A. When the second motor 4 rotates reversely, the motor drive circuit 2 causes the motor current to flow in direction B.

[0032] The control unit 1 is configured with a central processing unit and other components. An operation signal is input to the control unit 1 to open or close the tailgate 51. The operation signal is generated by the operation of the operation unit in the vehicle or the electronic key. The schematic diagram of the operation unit is omitted. The control unit 1 outputs a control signal to the motor drive circuit 2 based on the input operation signal to control the rotation of the first motor 3 and the second motor 4. The control signal for the forward rotation of both the motor 3 and the motor 4 is a forward rotation command. The control signal for the reverse rotation of both the motor 3 and the motor 4 is a reverse command.

[0033] As described below, the motor drive circuit 2 is configured with an H-bridge circuit having four switching elements. The motor drive circuit 2 energizes the first motor 3 and the second motor 4 based on a control signal from the control unit 1 to rotate both the motors 3 and 4 forward or reversely.

[0034] The first shunt resistor 5 is provided between the first motor 3 and the motor drive circuit 2. When the first motor 3 rotates forward, the motor drive circuit 2 applies a motor current in direction A to the first shunt resistor 5. When the first motor 3 rotates reversely, the motor drive circuit 2 applies a motor current in direction B to the first shunt resistor 5.

[0035] The second shunt resistor 6 is provided between the second motor 4 and the motor drive circuit 2. When the second motor 4 rotates forward, the motor drive circuit 2 applies a motor current in direction A to the second shunt resistor 6. When the second motor 4 rotates reversely, the motor drive circuit 2 applies a motor current in direction B to the second shunt resistor 6.

[0036] The first voltage detection circuit 7 detects the voltage across the first shunt resistor 5. The detection value of the voltage across the first shunt resistor 5 differs depending on whether the direction of the motor current flowing through the first shunt resistor 5 is direction A or direction B. The first voltage detection circuit 7 outputs the detection value V1 of the voltage across the first shunt resistor 5 to the control unit 1.

[0037] The second voltage detection circuit 8 detects the voltage across the second shunt resistor 6. The detected value of the voltage differs depending on whether the direction of the motor current flowing through the second shunt resistor 6 is direction A or direction B. The second voltage detection circuit 8 outputs the detected value V2 of the voltage across the second shunt resistor 6 to the control unit 1.

[0038] The control unit 1 detects an open fault in the current path of the first motor 3 and the second motor 4 based on the voltage across the first shunt resistor 5 input from the first voltage detection circuit 7 and the voltage across the second shunt resistor 6 input from the second voltage detection circuit 8. The detection method will be explained in detail later.

[0039] Figure 2 is a circuit diagram of a motor drive circuit 2. The motor drive circuit 2 is configured with an H-bridge circuit having four switching elements Q1 to Q4. For example, each switching element Q1 to Q4 is configured using a field effect transistor (FET). The switching elements Q1 and Q2 are connected in series between a DC power supply Vcc and a ground G. The switching elements Q3 and Q4 are also connected in series between a DC power supply Vcc and a ground G. A series circuit of a first motor 3 and a first shunt resistor 5 and a series circuit of a second motor 4 and a second shunt resistor 6 are connected in parallel between a connection point "m" of the switching elements Q1 and Q2 and a connection point "n" of the switching elements Q3 and Q4.

[0040] Each of the switching elements Q1 to Q4 is individually given a control signal from the control unit 1. The control signal is a binary signal of a high level or a low level. In the switching elements Q1 to Q4, when a high level signal (hereinafter referred to as an "H signal") is given, the switching element is turned ON. When a low level signal (hereinafter referred to as an "L signal") is given, the switching element is turned OFF. Depending on the on state or off state of these switching elements Q1 to Q4, the motor current flows in direction A or direction B to the first motor 3 and the second motor 4 and the first shunt resistor 5 and the second shunt resistor 6. The details are described below.

[0041] Figure 3 2 shows a circuit diagram of the first voltage detection circuit 7. The second voltage detection circuit 8 has the same configuration as the first voltage detection circuit 7. Only the first voltage detection circuit 7 will be described below.

[0042] The first voltage detection circuit 7 is configured with differential amplifiers 71 and 72 and resistors R1 to R6. The negative side input terminal "e" (hereinafter referred to as the "negative terminal") of the differential amplifier 71 is connected to one end 5a of the first shunt resistor 5 via the resistor R1. The positive side input terminal "f" (hereinafter referred to as the "positive terminal") of the differential amplifier 71 is connected to the other end 5b of the first shunt resistor 5 via the resistor R2. The resistor R3 is connected between the negative terminal "e" and the output terminal "g" of the differential amplifier 71. The differential amplifier 71 calculates and amplifies the difference between the potential of the positive terminal "f" and the potential of the negative terminal "e". The differential amplifier 71 outputs the value of the detection voltage V1 across the first shunt resistor 5 to Figure 1 Control unit 1.

[0043] The negative terminal "h" of the differential amplifier 72 is connected to the output terminal "j". The output terminal "j" is connected to the positive terminal "f" of the differential amplifier 71 via the resistor R4. The positive terminal "i" of the differential amplifier 72 is connected to the connection point "k" of the resistors R5 and R6. The resistors R5 and R6 are connected in series between the DC power supply Vd and the ground G. The differential amplifier 72 and the resistors R4 to R6 configure the offset voltage generating circuit 73. The offset voltage generating circuit 73 converts the voltage of the DC power supply Vd divided by the resistors R5 and R6 into an offset voltage of a predetermined value through the differential amplifier 72 and the resistor R4, and provides the offset voltage to the positive terminal "f" of the differential amplifier 71. The reason for the offset voltage generating circuit 73 is as follows.

[0044] exist Figure 3, when the direction of the motor current flowing into the first shunt resistor 5 is direction A, the potential of one end 5a of the first shunt resistor 5 is lower than the potential of the other end 5b of the first shunt resistor 5. Therefore, the potential of the negative terminal "e" of the differential amplifier 71 is also lower than the potential of the positive terminal "f", so the differential amplifier 71 can correctly calculate the voltage across the first shunt resistor 5. However, if the motor current is in direction B, the potential of one end 5a of the first shunt resistor 5 is higher than the potential of the other end 5b of the first shunt resistor 5. Therefore, the potential of the negative terminal "e" of the differential amplifier 71 becomes higher than the potential of the positive terminal "f", and the differential amplifier 71 cannot correctly calculate the voltage at both ends of the first shunt resistor 5. Therefore, an offset voltage is given to the positive terminal "f" of the differential amplifier 71 by the offset voltage generating circuit 73 so that the potential of the positive terminal "f" is always higher than the potential of the negative terminal "e". This allows the differential amplifier 71 to correctly calculate the voltage at both ends of the first shunt resistor 5 regardless of the direction of the motor current.

[0045] Next, refer to the attached Figures 4 to 9 The paths of the motor currents flowing through the first motor 3 and the second motor 4 are described.

[0046] Figure 4 is a diagram showing the motor current paths of both motors 3 and 4 under normal conditions during forward rotation. The control signal output from the control unit 1 to the motor drive circuit 2 is a forward rotation command when the motor is rotating forward. The forward rotation command is configured with an H signal to turn on the switching elements Q2 and Q3, and is configured with an L signal to turn off the switching elements Q1 and Q4. Figure 6 and Figure 8 The same is true. When the switching elements Q2 and Q3 are turned on, the motor current in the direction A flows to each of the motors 3 and 4 along the path indicated by the thick arrows. The motor current also flows through each of the shunt resistors 5 and 6, resulting in a voltage drop across each of the shunt resistors 5 and 6. The voltage drops are respectively Figure 1 The first voltage detection circuit 7 and the second voltage detection circuit 8 in the circuit detect the voltage across each of the shunt resistors 5 and 6. Figures 5 to 9 The same is true in .

[0047] Figure 5 is a diagram showing the motor current paths of both motors 3 and 4 under normal conditions during reverse rotation. The control signal output from the control unit 1 to the motor drive circuit 2 is a reverse rotation command when the motor rotates in reverse. The reverse rotation command is configured with an H signal to turn on the switching elements Q1 and Q4 and is configured with an L signal to turn off the switching elements Q2 and Q3. Figure 7 and Fig. 9The same is true. When the switching elements Q1 and Q4 are turned on, the motor current in direction A flows to each of the motors 3 and 4 along the path indicated by the thick arrows. The motor current also flows through each of the shunt resistors 5 and 6, causing a voltage drop across each of the shunt resistors 5 and 6. In this case, since the direction of the motor current is Figure 4 The direction of the current is opposite, so the voltage across each shunt resistor 5 and 6 is less than Figure 4 The voltage in.

[0048] Figure 6 is a diagram showing a motor current path when an open circuit fault occurs in the current path of the first motor 3 (hereinafter referred to as "first motor system") during forward rotation. The cause of the open circuit fault may be a disconnection between the motor terminal and the power feeding cable. Figures 7 to 9 The same is true. Figure 6 In the embodiment of the present invention, due to the turning on of the switching elements Q2 and Q3, the motor current in the direction A flows to the second motor 4 in the current path indicated by the thick arrow. On the other hand, on the side where the disconnection occurs, no motor current flows to the first motor 3. Therefore, the second voltage detection circuit 8 detects only the voltage across the second shunt resistor 6.

[0049] Figure 7 is a diagram showing the motor current path in the case of an open circuit fault in the first motor system during reverse rotation. In this case, due to the turning on of the switching elements Q1 and Q4, the motor current in the direction B flows to the second motor 4 in the path indicated by the thick arrow. On the other hand, no motor current flows to the first motor 3 on the side where the open circuit fault occurs. Therefore, the second voltage detection circuit 8 detects only the voltage across the second shunt resistor 6. At this time, since the direction of the motor current is Figure 6 The direction is opposite, so the voltage across the second shunt resistor 6 is less than Figure 6 voltage.

[0050] Figure 8 is a diagram showing the motor current path in the case of an open circuit fault in the current path of the second motor 4 (hereinafter referred to as the "second motor system") during forward rotation. In this case, due to the turning on of the switching elements Q2 and Q3, the motor current in the direction A flows to the first motor 3 in the path indicated by the thick arrow. On the other hand, on the side where the open circuit occurs, no motor current flows to the second motor 4. Therefore, the first voltage detection circuit 7 detects only the voltage across the first shunt resistor 5.

[0051] Fig. 9is a diagram showing the motor current path in the case of an open circuit fault in the second motor system during reverse rotation. In this case, due to the turning on of the switching elements Q1 and Q4, the motor current in the direction B flows to the first motor 3 in the path indicated by the thick arrow. On the other hand, on the side where the open circuit fault occurs, no motor current flows to the second motor 4. Therefore, the first voltage detection circuit 7 detects only the voltage across the first shunt resistor 5. In this case, since the direction of the motor current is Figure 8 The direction is opposite to that of the first shunt resistor 5, so the voltage across the first shunt resistor 5 is less than Figure 8 The voltage in.

[0052] The voltage across the first shunt resistor 5 detected by the first voltage detection circuit 7 and the voltage across the second shunt resistor 6 detected by the second voltage detection circuit 8 are respectively input to the control unit 1. The control unit 1 detects an open circuit fault in the first motor system and the second motor system based on the kind of control signal (forward or reverse rotation command), the two-terminal voltage of each shunt resistor 5 and 6, and the threshold value described below. The details of the detection method are described below.

[0053] Fig. 10A 2 is a graph showing the relationship between two threshold values ​​α and β for detecting an open circuit fault and the voltages V1 and V2 detected by the corresponding voltage detection circuits 7 and 8 . Fig. 10B is a diagram showing that the detection voltage V1 is the voltage across the first shunt resistor 5 and the detection voltage V2 is the voltage across the second shunt resistor 6 .

[0054] exist Fig. 10A , the detection voltages V1 and V2 vary between 0 volts and 5 volts. When the first motor 3 and the second motor 4 stop, the detection voltages V1 and V2 are both about 2.5 volts. The first threshold α is preset to be slightly greater than the 2.5 volts. The second threshold β is preset to be slightly less than 2.5 volts. For example, the first threshold α should be preset according to the upper limit of the detection voltage variation when the first motor 3 and the second motor 4 stop. The second threshold β should be preset according to the lower limit of the detection voltage variation when the first motor 3 and the second motor 4 stop.

[0055] When each of motors 3 and 4 rotates in the forward direction, if there is no open circuit fault in any motor system, Fig. 10B The motor current in the direction A shown flows through each of the shunt resistors 5 and 6. In this case, both the detection voltages V1 and V2 are greater than the first threshold α. However, when an open-circuit fault occurs in the first motor system, no motor current flows through the first shunt resistor 5, so the detection voltage V1 is less than the first threshold α. In addition, when an open-circuit fault occurs in the second motor system, no motor current flows through the second shunt resistor 6, so the detection voltage V2 is less than the first threshold α.

[0056] On the other hand, when each of motors 3 and 4 is in reverse direction, if there is no open circuit fault in any motor system, Fig. 10B The motor current in the direction B shown in FIG. 2 flows through each shunt resistor 5 and 6. In this case, the detection voltages V1 and V2 are both less than the second threshold value β. However, when an open circuit fault occurs in the first motor system, no motor current flows through the first shunt resistor 5, so the detection voltage V1 is greater than the second threshold value β. When an open circuit fault occurs in the second motor system, no motor current flows through the second shunt resistor 6, so the detection voltage V2 is greater than the second threshold value β.

[0057] In this way, during the forward rotation of each of the motors 3 and 4, an open circuit fault in each motor system can be detected based on the comparison result of the detection voltages V1 and V2 with the preset first threshold value α. During the reverse rotation of each of the motors 3 and 4, an open circuit fault in each motor system can be detected based on the comparison result of the detection voltages V1 and V2 with the preset second threshold value β.

[0058] Fig.11 It is shown that for the above Figures 4 to 9 A table showing the criteria for detecting an open circuit fault for six conditions is shown.

[0059] Reference numerals #1 to #3 indicate fault criteria during forward rotation of the motor. In the case of criterion #1, since both detection voltages V1 and V2 are greater than the first threshold α, the control unit 1 determines that an open circuit fault has not occurred in either motor system. Figure 4 The current path in this case is shown in FIG. In the case of standard #2, the detection voltage V1 is less than the first threshold value α, so the control unit 1 determines that an open circuit fault occurs in the first motor system. The current path at this time is as follows Figure 6 In the case of standard #3, the detection voltage V2 is less than the first threshold value α, so the control unit 1 determines that an open circuit fault occurs in the second motor system. Figure 8 The current path in this case is shown in FIG.

[0060] Reference numerals #4 to #6 indicate fault criteria during motor reverse rotation. In the case of criterion #4, since both detection voltages V1 and V2 are less than the second threshold β, the control unit 1 determines that an open circuit fault has not occurred in either motor system. Figure 5 The current path in this case is shown in FIG. In the case of standard #5, the detection voltage V1 is greater than the second threshold value β, so the control unit 1 determines that an open circuit fault occurs in the first motor system. The current path at this time is as follows Figure 7 In the case of standard #6, the detection voltage V2 is higher than the second threshold value β, so the control unit 1 determines that an open circuit fault occurs in the second motor system. Fig. 9The current path in this case is shown in FIG.

[0061] Fig.12 1 is a flowchart showing a fault detection method. Each processing step in the flowchart is executed by the control unit 1. Reference numerals #1 to #6 attached to the flowchart represent Fig.11 The reference numerals shown in FIG.

[0062] In step S1, the control unit 1 waits for an input operation signal. When the control unit 1 is input with the operation signal, in step S2, the control unit 1 outputs a control signal corresponding to the operation signal to the motor drive circuit 2. For example, if the operation signal is a signal indicating that the tailgate 51 is opened (see Fig.13 ), the control unit 1 outputs the aforementioned forward rotation command as the control signal. If the operation signal is a signal indicating that the rear baffle 51 is closed, the control unit 1 outputs the aforementioned reverse rotation command as the control signal.

[0063] If the control signal is a forward command, steps S3 to S9 are performed. In step S3, the control unit 1 acquires the two-terminal voltages V1 and V2 of each shunt resistor 5 and 6 detected by each voltage detection circuit 7 and 8. Next, in step S4, the control unit 1 compares the two-terminal voltages V1 and V2 with the first threshold α to determine that V1>α and V2>α. If, as a result of the judgment, V1>α and V2>α, the control unit 1 judges in step S5 that both motor systems are normal, that is, there is no open circuit fault.

[0064] If the judgment result in step S4 is not V1>α and V2>α, the control unit 1 judges V1≤α and V2>α in step S6. If the determination result is V1≤α and V2>α, the control unit 1 determines in step S7 that an open circuit fault has occurred in the first motor system. If V1≤α and V2>α do not exist in step S6, the control unit 1 determines in step S8 that V1>α and V2≤α. If, as a result of the determination, V1>α and V2≤α, the control unit 1 determines in step S9 that an open circuit fault has occurred in the second motor system. If V1>α and V2≤α do not exist in step S8, the control unit 1 terminates the process.

[0065] On the other hand, if the control signal is a reverse command, the control unit 1 performs processing steps S10 to S16. In step S10, the control unit 1 acquires the two-terminal voltages V1 and V2 of each of the shunt resistors 5 and 6 detected by each of the voltage detection circuits 7 and 8. Next, in step S11, the control unit 1 compares the two-terminal voltages V1 and V2 with the second threshold value β to determine that V1<β and V2<β. If, as a result of the determination, V1<β and V2<β, the control unit 1 determines in step S12 that both motor systems are normal, that is, there is no open circuit fault.

[0066] If the judgment result in step S11 is not V1<β and V2<β, the control unit 1 judges V1≥β and V2<β in step S13. If the determination result is V1≥β and V2<β, the control unit 1 judges that an open circuit fault has occurred in the first motor system in step S14. If V1≥β and V2<β in step S13, the control unit 1 determines V1<β and V2≥β in step S15. If, as a result of the determination, V1<β and V2≥β, the control unit 1 determines that an open circuit fault has occurred in the second motor system in step S16. If the determination result in step S15 is not V1<β and V2≥β, the control unit 1 terminates the process.

[0067] In the above-described embodiment, the motor control device 100 that controls the two motors 3 and 4 has a single control unit 1, a single motor drive circuit 2, two shunt resistors 5 and 6, and two voltage detection circuits 7 and 8. During forward rotation of the motor, the control unit 1 detects an open circuit fault in the two motor systems, respectively, based on a comparison result of the two-terminal voltage V1 and V2 of each shunt resistor 5 and 6 detected by each voltage detection circuit 7 and 8 with a first threshold value α. In addition, when the motor rotates in the reverse direction, the control unit 1 detects an open circuit fault in the two motor systems, respectively, based on a comparison result of the two-terminal voltage V1 and V2 of each shunt resistor 5 and 6 with a second threshold value β.

[0068] Therefore, even if an open-circuit fault in the two motor systems is detected in each of the forward rotation and the reverse rotation of the motors 3 and 4, only one control unit 1 and the motor drive circuit 2 need to be installed, respectively. In addition, only two shunt resistors 5 and 6 and voltage detection circuits 7 and 8 are required each, that is, as many as the number of motors 3 and 4. Therefore, according to this embodiment, a simple circuit configuration with a small number of components can accurately detect an open-circuit fault in the two motor systems in the forward rotation and the reverse rotation of the motors 3 and 4.

[0069] In addition to the above-described embodiments, various other embodiments may be adopted in the present invention, including the following.

[0070] exist Fig.11In the embodiment, it is assumed that an open circuit fault has occurred in one of the first motor system and the second motor system, but the present invention is also effective when an open circuit fault has occurred in both motor systems. In this case, if V1≤α and V2≤α during forward rotation of the motor, the control unit 1 determines that an open circuit fault has occurred in both motor systems. If V1≥β and V2≥β during reverse rotation of the motor, the control unit 1 determines that an open circuit fault has occurred in both motor systems.

[0071] exist Figure 1 In the embodiment, two motors are provided, that is, the first motor 3 and the second motor 4, but three or more motors may be provided. In this case, shunt resistors and voltage detection circuits are provided for the plurality of motors, respectively.

[0072] For the first voltage detection circuit 7, Figure 3 The circuit configuration shown in FIG. 8 is an example, and other circuit configurations may be provided. The same applies to the second voltage detection circuit 8 .

[0073] exist Fig. 10A and Fig. 10B In FIG. 1 , an example of the detection voltages V1 and V2 varying between 0 volt and 5 volt is given, but this is only an example, and the upper and lower limits of the variation range of the detection voltages V1 and V2 may be other values.

[0074] In the above-described embodiment, the tailgate 51 of the vehicle is used as an example of an object driven by the first motor 3 and the second motor 4 , but the present invention can also be applied to a control device of a motor for driving an object other than the tailgate.

[0075] Cross-references to related applications

[0076] This application is based upon and claims the benefit of priority from Japanese patent application No. 2023-192717, filed on November 13, 2023, the entire contents of which are incorporated herein by reference.

Claims

1. A motor control device for parallel-connected motors, the motor control device comprising: A single motor drive circuit, the single motor drive circuit drives multiple motors to rotate forward or reverse; a single control unit that outputs a control signal for controlling the rotation of each motor to the motor drive circuit; a plurality of shunt resistors disposed between each of the electric motors and the motor drive circuit; as well as a plurality of voltage detection circuits, the plurality of voltage detection circuits detecting the voltage across both ends of each of the shunt resistors, When the control signal is a forward command for each motor, the control unit compares the detected voltage across each shunt resistor with a preset first threshold value to detect a fault in a current path of each motor, When the control signal is a reverse command for each motor, the control unit compares the detected voltage across each shunt resistor with a preset second threshold value to detect a fault in a current path of each motor.

2. The motor control device according to claim 1, in, When the control signal is a forward command, if the voltage at either end of each shunt resistor is lower than the preset first threshold, the control unit detects that there is an open circuit fault in a current path of the motor connected to the shunt resistor.

3. The motor control device according to claim 1, in, When the control signal is a reverse direction command, if the voltage at either end of each shunt resistor is higher than the second threshold value, the control unit determines that there is an open circuit fault in a current path of the motor connected to the shunt resistor.

4. The motor control device according to any one of claims 1 to 3, in, The preset first threshold is greater than the voltage across each shunt resistor when each motor is stopped, and The preset second threshold value is less than the voltage across each shunt resistor when each motor is stopped.

5. A method for detecting a fault in a motor control device for electric motors connected in parallel, the motor control device comprising: a single motor drive circuit that drives a single control unit that outputs a control signal to the motor drive circuit for controlling the rotation of each motor; a plurality of shunt resistors disposed between each motor and the motor drive circuit; as well as a plurality of voltage detection circuits, the plurality of voltage detection circuits detecting the voltage across both ends of each shunt resistor, The method comprises the following steps of the control unit: outputting the control signal to the motor drive circuit; When the control signal is a forward command for each motor, comparing the detected voltage across each shunt resistor with a preset first threshold value; When the control signal is a reverse command for each motor, comparing the detected voltage across each shunt resistor with a preset second threshold value; and Based on the comparison result between each voltage and each threshold value, a fault in the current path of each motor is detected.

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