Electric motor control device, and fault detection method

Abstract

To accurately detect a fault in a current path of an electric motor even in either case of forward rotation and backward rotation of the electric motor in a simple circuit configuration in which the number of components is reduced.SOLUTION: An electric motor control device 100 which controls a plurality of electric motors 3 and 4 comprises a single control section 1, a single motor drive circuit 2, a plurality of shunt resistors 5 and 6, and a plurality of voltage detection circuits 7 and 8. In forward rotation of the electric motors 3 and 4, the control section 1 detects the presence / absence of failures in current paths of the electric motors 3 and 4 based on a result of comparing voltages V1 and V2 at both ends of the shunt resistors 5 and 6 detected by the voltage control circuits 7 and 8 with a preset first threshold. In backward rotation of the electric motors 3 and 4, the control section 1 detects the presence / absence of failures in the current paths of the electric motors 3 and 4 based on a result of comparing the voltages V1 and V2 at both the ends of the shunt resistors 5 and 6 detected by the voltage detection circuits 7 and 8 with a present second threshold.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a control device for an electric motor used for opening and closing a tailgate provided at the rear of a vehicle, and more particularly to a technique for detecting a disconnection fault that occurs in a current path of an electric motor. [Background technology]

[0002] Fig. 13 is a diagram showing an outline of an electric tailgate. As shown in Fig. 13, a tailgate 51 is provided at the rear of a vehicle Z such as a four-wheeled motor vehicle. The upper end of the tailgate 51 is supported by a shaft 52 provided on a vehicle body 50. The tailgate 51 swings about the shaft 52 in an opening direction X and a closing direction Y. Reference characters 51a, 51b, and 51c indicate the tailgate in a fully closed position, a half-open position, and a fully open position, respectively. The tailgate 51 is driven by an electric motor that rotates by operating an operating switch (not shown).

[0003] FIG. 14 shows a simplified view of a drive mechanism 60 for driving the tailgate 51. The drive mechanism 60 is provided between the vehicle body 50 and the tailgate 51. The drive mechanism 60 includes a cylindrical main body 61, an electric motor 62 housed inside the main body 61, an arm 63 that moves in a direction a or b depending on the rotation direction of the electric motor 62, and a conversion mechanism 64 that converts the rotational motion of the electric motor 62 into linear motion of the arm 63. One end of the main body 61 is fixed to the vehicle body 50. One end of the arm 63 is connected to the tailgate 51, and the other end of the arm 63 is connected to the conversion mechanism 64.

[0004] When the electric motor 62 rotates in the forward direction, the arm 63 moves in the direction a via the conversion mechanism 64 which operates in conjunction with this rotation. As a result, the tailgate 51 is pushed up by the arm 63 and swings in the opening direction X, and the tailgate 51 opens. When the electric motor 62 rotates in the reverse direction, the arm 63 moves in the direction b via the conversion mechanism 64 which operates in conjunction with this rotation. As a result, the tailgate 51 is pulled down by the arm 63 and swings in the closing direction Y, and the tailgate 51 closes.

[0005] 15, a pair of drive mechanisms 60 are provided on both the left and right sides of the tailgate 51 when viewed from the rear of the vehicle Z. That is, two electric motors 62 serving as drive sources for the tailgate 51 are provided on the left and right sides. The reason for this is to increase the drive force applied to the tailgate 51 and to reduce deflection of the tailgate 51 by balancing the drive force between the left and right sides.

[0006] Patent documents 1 to 4 describe devices in which a plurality of electric motors for operating one or a plurality of objects are driven by a single drive circuit or controlled by a single control circuit, while patent documents 5 to 8 describe devices in which two electric motors for opening and closing a tailgate are controlled by a single control circuit. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 5-344788 [Patent Document 2] JP 2020-78199 A [Patent Document 3] International Publication No. 2020 / 179041 [Patent Document 4] JP 2000-166294 A [Patent Document 5] JP 2017-172301 A [Patent Document 6] JP 2017-141577 A [Patent Document 7] Patent Publication No. 2021-38532 [Patent Document 8] Patent Publication No. 2021-139138 Summary of the Invention [Problem to be solved by the invention]

[0008] In a device equipped with a plurality of electric motors, a method of detecting a wire breakage occurring in the current path of the electric motor is known in which the voltage across a shunt resistor connected in series with each electric motor is measured. For example, Patent Document 3 discloses such a wire breakage detection method. In this case, if each electric motor rotates in only one direction, only one-way current flows through each shunt resistor. Therefore, a wire breakage can be detected by a simple method of comparing the voltage across each shunt resistor with a preset threshold value. However, if each electric motor rotates in the forward and reverse directions, the direction of the current flowing through each shunt resistor is opposite during forward and reverse rotation. Therefore, the voltage across each shunt resistor also differs during forward and reverse rotation, so that a wire breakage cannot be accurately detected by the same method as that for an electric motor rotating in one direction.

[0009] The object of the present invention is to accurately detect faults in the current paths of electric motors in both forward and reverse rotation of the electric motors using a simple circuit configuration with a small number of components in a device for controlling the forward and reverse rotation of multiple electric motors. [Means for solving the problem]

[0010] The electric motor control device according to the present invention includes a single motor drive circuit for driving a plurality of electric motors connected in parallel in forward or reverse rotation, a single control unit for outputting a control signal for controlling the rotation of each electric motor to the motor drive circuit, a plurality of shunt resistors provided between each electric motor and the motor drive circuit, and a plurality of voltage detection circuits for detecting the voltages across each shunt resistor. When the control signal is a forward rotation command for commanding the forward rotation of each electric motor, the control unit detects the presence or absence of a fault in the current path of each electric motor based on a comparison result between the voltages across each shunt resistor detected by the voltage detection circuit and a first threshold value set in advance. When the control signal is a reverse rotation command for commanding the reverse rotation of each electric motor, the control unit detects the presence or absence of a fault in the current path of each electric motor based on a comparison result between the voltages across each shunt resistor detected by the voltage detection circuit and a second threshold value set in advance. Effect of the Invention

[0011] According to the electric motor control device of the present invention, even when detecting the presence or absence of a fault in the current path of each electric motor individually during forward and reverse rotation of the electric motor, only one control unit and one motor drive circuit are required. Also, the shunt resistors and voltage detection circuits need to be provided in the same number as the number of electric motors.

[0012] Therefore, according to the present invention, a fault in the current path of the electric motor can be accurately detected both when the electric motor is rotating in the forward direction and when the electric motor is rotating in the reverse direction, using a simple circuit configuration with a small number of parts. [Brief description of the drawings]

[0013] [Figure 1] 1 is a block diagram of an electric motor control device according to the present invention; [Diagram 2] FIG. 2 is a circuit diagram showing a specific configuration of a motor drive circuit. [Diagram 3] 4 is a circuit diagram showing a specific configuration of a first voltage detection circuit. FIG. [Figure 4]4 is a diagram showing a motor current path in a normal state when the motor rotates forward. FIG. [Diagram 5] FIG. 4 is a diagram showing a motor current path in a normal state when the motor rotates in the reverse direction. [Figure 6] 11 is a diagram showing a motor current path when a break occurs in a first motor system during forward rotation of the motor. FIG. [Figure 7] 11 is a diagram showing a motor current path when a break occurs in the first motor system during reverse rotation of the motor. FIG. [Figure 8] 13 is a diagram showing a motor current path when a break occurs in the second motor system during forward rotation of the motor. FIG. [Figure 9] 13 is a diagram showing a motor current path when a break occurs in the second motor system during reverse rotation of the motor. FIG. [Figure 10] 11 is a diagram showing the relationship between two threshold values ​​and a detection voltage. [Figure 11] 11 is a table showing a method for detecting an open circuit fault. [Figure 12] 4 is a flowchart illustrating a fault detection method according to the present invention. [Figure 13] FIG. 2 is a diagram showing an outline of a tailgate. [Figure 14] FIG. 2 is a simplified diagram showing a tailgate drive mechanism. [Figure 15] FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. The same reference numerals are used throughout the drawings to designate the same or corresponding parts.

[0015] Fig. 1 is a block diagram of an electric motor control device according to the present invention. The electric motor control device 100 is a device that controls the rotation of a first motor 3 and a second motor 4. Each of the motors 3, 4 is a DC electric motor that can rotate forward and backward, and opens and closes the tailgate 51 described in Figs. 13 to 15. For example, the first motor 3 corresponds to the electric motor 62 on the left side in Fig. 15. The second motor 4 corresponds to the electric motor 62 on the right side in Fig. 15.

[0016] The electric 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.

[0017] When the first motor 3 rotates forward, the motor drive circuit 2 passes the motor current in direction A. When the first motor 3 rotates reversely, the motor drive circuit 2 passes the motor current in direction B. Similarly, when the second motor 4 rotates forward, the motor drive circuit 2 passes the motor current in direction A. And when the second motor 4 rotates reversely, the motor drive circuit 2 passes the motor current in direction B.

[0018] The control unit 1 is composed of a CPU and the like. An operation signal for opening and closing the tailgate 51 is input to the control unit 1. This operation signal is generated by operating an operation unit provided in the vehicle or an electronic key. This operation unit is not shown in the figure. Based on the input operation signal, the control unit 1 outputs a control signal for controlling the rotation of the first motor 3 and the second motor 4 to the motor drive circuit 2. The control signal for rotating each of the motors 3 and 4 in the forward direction is a forward rotation command. The control signal for rotating each of the motors 3 and 4 in the reverse direction is a reverse rotation command.

[0019] As described later, the motor drive circuit 2 is composed of an H-bridge circuit having four switching elements. Based on a control signal from the control unit 1, the motor drive circuit 2 energizes the first motor 3 and the second motor 4 to rotate each of the motors 3 and 4 forward or reverse.

[0020] 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 passes a motor current in direction A through the first shunt resistor 5. When the first motor 3 rotates reversely, the motor drive circuit 2 passes a motor current in direction B through the first shunt resistor 5.

[0021] 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 passes a motor current in direction A through the second shunt resistor 6. When the second motor 4 rotates reversely, the motor drive circuit 2 passes a motor current in direction B through the second shunt resistor 6.

[0022] The first voltage detection circuit 7 detects the voltage across the first shunt resistor 5. The detected value of this voltage 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 detected value V1 of the voltage across the first shunt resistor 5 to the control unit 1.

[0023] The second voltage detection circuit 8 detects the voltage across the second shunt resistor 6. The detected value of this voltage also 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.

[0024] The control unit 1 detects the presence or absence of a disconnection fault in each of the current paths of the first motor 3 and the second motor 4 based on the voltages across the shunt resistors 5, 6 input from the voltage detection circuits 7, 8. The detection method will be described in detail later.

[0025] Figure 2 is a circuit diagram showing the specific configuration of the motor drive circuit 2. The motor drive circuit 2 is composed of a known H-bridge circuit having four switching elements Q1 to Q4. Each of the switching elements Q1 to Q4 is, for example, composed of a FET. The switching element Q1 and the switching element Q2 are connected in series between the DC power supply Vcc and the ground G. The switching element Q3 and the switching element Q4 are also connected in series between the DC power supply Vcc and the ground G. And between the connection point m of the switching elements Q1 and Q2 and the connection point n of the switching elements Q3 and Q4, a series circuit of the first motor 3 and the first shunt resistor 5 and a series circuit of the second motor 4 and the second shunt resistor 6 are connected in parallel.

[0026] A control signal is individually given from the control unit 1 to each of the switching elements Q1 to Q4. This control signal is a binary signal of H (High) level or L (Low) level. Among the switching elements Q1 to Q4, the switching element to which an H-level signal (hereinafter referred to as "H signal") is given turns ON, and the switching element to which an L-level signal (hereinafter referred to as "L signal") is given turns OFF. According to the ON and OFF of these switching elements Q1 to Q4, a motor current flows in the A direction or the B direction through the first motor 3 and the second motor 4, and the first shunt resistor 5 and the second shunt resistor 6. Details of this will be described later.

[0027] Figure 3 is a circuit diagram showing the specific configuration of the first voltage detection circuit 7. Since 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.

[0028] The first voltage detection circuit 7 includes differential amplifiers 71 and 72, and resistors R1 to R6. The negative input terminal (hereinafter referred to as the "negative terminal") e of the differential amplifier 71 is connected to one end 5a of the first shunt resistor 5 via the resistor R1. The positive input terminal (hereinafter referred to as the "positive terminal") f of the differential amplifier 71 is connected to the other end 5b of the first shunt resistor 5 via the resistor R2. A 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 output of the differential amplifier 71 is output to the control unit 1 in FIG. 1 as the detected value V1 of the voltage across both ends of the first shunt resistor 5.

[0029] The negative terminal h of the differential amplifier 72 is connected to the output terminal j. This 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. These differential amplifier 72 and resistors R4 to R6 constitute an offset voltage generation circuit 73. The offset voltage generation 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 by the differential amplifier 72 and the resistor R4, and applies this offset voltage to the positive terminal f of the differential amplifier 71. The reason for providing such an offset voltage generation circuit 73 is as follows.

[0030] In FIG. 3, when the direction of the motor current flowing through the first shunt resistor 5 is the direction A, the potential of one end 5a of the first shunt resistor 5 is lower than the potential of the other end 5b. 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 that the differential amplifier 71 can correctly calculate the voltage across the first shunt resistor 5. However, when the direction of the motor current is the direction B, the potential of one end 5a of the first shunt resistor 5 is higher than the potential of the other end 5b. Therefore, the potential of the negative terminal e of the differential amplifier 71 is higher than the potential of the positive terminal f, so that the differential amplifier 71 cannot correctly calculate the voltage across the first shunt resistor 5. Therefore, the offset voltage generating circuit 73 applies an offset voltage to the positive terminal f of the differential amplifier 71 to always make the potential of the positive terminal f higher than the potential of the negative terminal e. This allows the differential amplifier 71 to correctly calculate the voltage across the first shunt resistor 5 regardless of the direction of the motor current.

[0031] Next, the paths of the motor currents flowing through the first motor 3 and the second motor 4 will be described with reference to FIGS.

[0032] FIG. 4 shows the motor current paths in the normal state when the motors 3 and 4 rotate in the forward direction. When the motors rotate in the forward direction, the control signal output from the control unit 1 to the motor drive circuit 2 is a forward rotation command. This forward rotation command is composed of an H signal that turns on the switching elements Q2 and Q3, and an L signal that turns off the switching elements Q1 and Q4. This is the same in FIG. 6 and FIG. 8. When the switching elements Q2 and Q3 are turned on, a motor current flows in the A direction through each of the motors 3 and 4 through the path indicated by the thick arrow. This motor current also flows through each of the shunt resistors 5 and 6, and a voltage drop occurs across each of the shunt resistors 5 and 6. This voltage drop is detected by the first voltage detection circuit 7 and the second voltage detection circuit 8 in FIG. 1 as the voltage across each of the shunt resistors 5 and 6, respectively. This is the same in FIG. 5 to FIG. 9.

[0033] FIG. 5 shows the motor current paths in the normal state when the motors 3 and 4 rotate in the reverse direction. When the motors rotate in the reverse direction, the control signal output from the control unit 1 to the motor drive circuit 2 is a reverse rotation command. This reverse rotation command consists of an H signal that turns on the switching elements Q1 and Q4, and an L signal that turns off the switching elements Q2 and Q3. This is the same in FIG. 7 and FIG. 9. When the switching elements Q1 and Q4 are turned on, a motor current flows in the B direction through the motors 3 and 4 through the path indicated by the thick arrow. This motor current also flows through the shunt resistors 5 and 6, and a voltage drop occurs across the shunt resistors 5 and 6. In this case, since the direction of the motor current is opposite to that in FIG. 4, the voltage across each of the shunt resistors 5 and 6 is smaller than that in FIG. 4.

[0034] FIG. 6 shows the motor current path when a disconnection fault occurs in the current path of the first motor 3 (hereinafter referred to as the "first motor system") when each of the motors 3, 4 is rotating in the forward direction. Possible causes of such a disconnection include a disconnection between the motor terminals and the power supply cable. The same applies to FIGS. 7 to 9. In FIG. 6, when the switching elements Q2 and Q3 are turned ON, a motor current flows in the A direction through the second motor 4 through the path indicated by the thick arrow. On the other hand, no motor current flows through the first motor 3 on the side where the disconnection occurred. Therefore, only the voltage across the second shunt resistor 6 is detected by the second voltage detection circuit 8.

[0035] FIG. 7 shows the motor current paths when a wire breakage fault occurs in the first motor system while the motors 3, 4 are rotating in the reverse direction. In this case, when the switching elements Q1, Q4 are turned ON, a motor current flows in the direction B through the second motor 4 via the path indicated by the thick arrow. On the other hand, no motor current flows through the first motor 3 on the side where the wire breakage occurred. Therefore, only the voltage across the second shunt resistor 6 is detected by the second voltage detection circuit 8. In this case, since the direction of the motor current is opposite to that in FIG. 6, the voltage across the second shunt resistor 6 is smaller than in the case of FIG. 6.

[0036] FIG. 8 shows the motor current paths when a wire breakage fault occurs in the current path of the second motor 4 (hereinafter referred to as the "second motor system") while the motors 3, 4 are rotating in the forward direction. In this case, when switching elements Q2, Q3 are turned ON, a motor current flows in the A direction through the first motor 3 through the path indicated by the thick arrow. On the other hand, no motor current flows through the second motor 4 on the side where the wire breakage occurred. Therefore, only the voltage across the first shunt resistor 5 is detected by the first voltage detection circuit 7.

[0037] FIG. 9 shows the motor current paths when a wire breakage fault occurs in the second motor system while the motors 3, 4 are rotating in the reverse direction. In this case, when switching elements Q1, Q4 are turned ON, a motor current flows in the direction B through the first motor 3 via the path indicated by the thick arrow. On the other hand, no motor current flows through the second motor 4 on the side where the wire breakage occurred. Therefore, only the voltage across the first shunt resistor 5 is detected by the first voltage detection circuit 7. In this case, since the direction of the motor current is opposite to that in FIG. 8, the voltage across the first shunt resistor 5 is smaller than in the case of FIG. 8.

[0038] 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 each input to the control unit 1. The control unit 1 detects the presence or absence of a disconnection fault in the first motor system and the second motor system based on the type of control signal (forward rotation command or reverse rotation command), the voltages across each of the shunt resistors 5, 6, and a threshold value described below. The details of this detection method will be described below.

[0039] 10(a) is a diagram showing the relationship between two thresholds α and β used for detecting a disconnection fault and the voltages V1 and V2 detected by the voltage detection circuits 7 and 8. As shown in FIG. 10(b), 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.

[0040] In Fig. 10(a), the detection voltages V1 and V2 vary between zero volts and 5 volts. When the first motor 3 and the second motor 4 are stopped, the detection voltages V1 and V2 are both approximately 2.5 volts. The first threshold value α is set to a value slightly larger than 2.5 volts. The second threshold value β is set to a value slightly smaller than 2.5 volts.

[0041] When the motors 3, 4 are rotating forward and no break occurs in any of the motor systems, a motor current flows through each of the shunt resistors 5, 6 in the direction A shown in FIG. 10(b). In this case, the detected voltages V1, V2 are both greater than the first threshold value α. However, if a break occurs in the first motor system, no motor current flows through the first shunt resistor 5, and the detected voltage V1 becomes equal to or less than the first threshold value α. On the other hand, if a break occurs in the second motor system, no motor current flows through the second shunt resistor 6, and the detected voltage V2 becomes equal to or less than the first threshold value α.

[0042] On the other hand, when the motors 3 and 4 are rotating in the reverse direction, if no break occurs in any of the motor systems, a motor current in the direction B shown in FIG. 10(b) flows through each of the shunt resistors 5 and 6. In this case, the detection voltages V1 and V2 are both smaller than the second threshold value β. However, if a break occurs in the first motor system, no motor current flows through the first shunt resistor 5, so the detection voltage V1 becomes equal to or greater than the second threshold value β. On the other hand, if a break occurs in the second motor system, no motor current flows through the second shunt resistor 6, so the detection voltage V2 becomes equal to or greater than the second threshold value β.

[0043] In this way, when the motors 3, 4 are rotating in the forward direction, a wire breakage fault in each motor system can be detected based on the comparison result between the detected voltages V1, V2 and the preset first threshold value α. Also, when the motors 3, 4 are rotating in the reverse direction, a wire breakage fault in each motor system can be detected based on the comparison result between the detected voltages V1, V2 and the preset second threshold value β.

[0044] FIG. 11 is a table showing the above-described open fault detection method for the six cases of FIGS.

[0045] Reference numbers #1 to #3 indicate failure determination criteria when the motor rotates forward. In the state of #1, since both of the detected voltages V1 and V2 are greater than the first threshold value α, the control unit 1 determines that no break has occurred in any of the motor systems. The current path at this time is as shown in FIG. 4. In the state of #2, since the detected voltage V1 is equal to or less than the first threshold value α, the control unit 1 determines that a break has occurred in the first motor system. The current path at this time is as shown in FIG. 6. In the state of #3, since the detected voltage V2 is equal to or less than the first threshold value α, the control unit 1 determines that a break has occurred in the second motor system. The current path at this time is as shown in FIG. 8.

[0046] Reference numbers #4 to #6 indicate failure judgment criteria when the motor rotates in the reverse direction. In the state of #4, since both of the detected voltages V1 and V2 are smaller than the second threshold value β, the control unit 1 judges that no break has occurred in any of the motor systems. The current path at this time is as shown in FIG. 5. In the state of #5, since the detected voltage V1 is equal to or greater than the second threshold value β, the control unit 1 judges that a break has occurred in the first motor system. The current path at this time is as shown in FIG. 7. In the state of #6, since the detected voltage V2 is equal to or greater than the second threshold value β, the control unit 1 judges that a break has occurred in the second motor system. The current path at this time is as shown in FIG. 9.

[0047] 12 is a flowchart showing a fault detection method according to the present invention. The process of each step in this flowchart is executed by the control unit 1. Note that #1 to #6 added to the flowchart represent the reference numbers shown in FIG.

[0048] In step S1, the control unit 1 waits for an operation signal to be input, and when the operation signal is input, 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 instructing an opening operation of the tailgate 51 (see FIG. 13), the control unit 1 outputs the above-mentioned forward rotation command as a control signal. On the other hand, if the operation signal is a signal instructing a closing operation of the tailgate 51, the control unit 1 outputs the above-mentioned reverse rotation command as a control signal.

[0049] If the control signal is a forward rotation command, the processes of steps S3 to S9 are executed. In step S3, the control unit 1 acquires the voltages V1 and V2 across the shunt resistors 5 and 6 detected by the voltage detection circuits 7 and 8. Next, in step S4, the control unit 1 compares the voltages V1 and V2 across the shunt resistors 5 and 6 with a first threshold value α to determine whether V1>α and V2>α. If the determination result is V1>α and V2>α, the control unit 1 determines in step S5 that both motor systems are normal, i.e., there is no disconnection.

[0050] If the determination result in step S4 is not V1>α and V2>α, the control unit 1 determines in step S6 whether V1≦α and V2>α. If the determination result is V1≦α and V2>α, the control unit 1 determines in step S7 that a disconnection has occurred in the first motor system. If the determination result is not V1≦α and V2>α in step S6, the control unit 1 determines in step S8 whether V1>α and V2≦α. If the determination result is V1>α and V2≦α, the control unit 1 determines in step S9 that a disconnection has occurred in the second motor system. If the determination result is not V1>α and V2≦α in step S8, the control unit 1 ends the process.

[0051] On the other hand, when the control signal is a reverse command, the processes of steps S10 to S16 are executed. In step S10, the control unit 1 acquires the voltages V1 and V2 at both ends of the shunt resistors 5 and 6 detected by the voltage detection circuits 7 and 8. Next, in step S11, the control unit 1 compares the voltages V1 and V2 at both ends with the second threshold value β to determine whether V1 < β and V2 < β. As a result of the determination, if V1 < β and V2 < β, the control unit 1 determines in step S12 that both motor systems are normal, that is, there is no disconnection.

[0052] If the determination result in step S11 is not V1 < β and V2 < β, the control unit 1 determines in step S13 whether V1 ≥ β and V2 < β. As a result of the determination, if V1 ≥ β and V2 < β, the control unit 1 determines in step S14 that a disconnection has occurred in the first motor system. Also, if the result in step S13 is not V1 ≥ β and V2 < β, the control unit 1 determines in step S15 whether V1 < β and V2 ≥ β. As a result of the determination, if V1 < β and V2 ≥ β, the control unit 1 determines in step S16 that a disconnection has occurred in the second motor system. If the result in step S15 is not V1 < β and V2 ≥ β, the control unit 1 ends the process.

[0053] In the above-described embodiment, the electric motor control device 100 that controls the two motors 3 and 4 includes 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. And the control unit 1 individually detects the presence or absence of disconnection in the two motor systems based on the comparison result between the voltages V1 and V2 at both ends of the shunt resistors 5 and 6 detected by the voltage detection circuits 7 and 8 and the first threshold value α when the motor rotates forward. Also, the control unit 1 individually detects the presence or absence of disconnection in the two motor systems based on the comparison result between the voltages V1 and V2 at both ends of the shunt resistors 5 and 6 and the second threshold value β when the motor rotates in reverse.

[0054] For this reason, even when detecting the presence or absence of a wire break in the two motor systems individually when the motors 3, 4 are rotating in the forward direction and when they are rotating in the reverse direction, it is sufficient to provide only one control unit 1 and one motor drive circuit 2, and also only two shunt resistors 5, 6 and two voltage detection circuits 7, 8, that is, the same number as the number of motors 3, 4. Therefore, according to this embodiment, with a simple circuit configuration with a small number of parts, it is possible to accurately detect a wire break fault in the two motor systems when the motors 3, 4 are rotating in the forward direction and when they are rotating in the reverse direction.

[0055] In addition to the above-described embodiment, the present invention can employ various other embodiments as described below.

[0056] In Fig. 11, it is assumed that a break occurs in one of the first motor system and the second motor system, but the present invention is also effective when a break occurs in both motor systems. In this case, if V1 ≤ α and V2 ≤ α when the motor rotates forward, the control unit 1 determines that a break occurs in both motor systems. Also, if V1 ≥ β and V2 ≥ β when the motor rotates reverse, the control unit 1 determines that a break occurs in both motor systems.

[0057] 1, two electric motors, a first motor 3 and a second motor 4, are provided, but three or more electric motors may be provided. In this case, the shunt resistors and voltage detection circuits are provided in the same number as the electric motors.

[0058] 3 is merely an example, and the first voltage detection circuit 7 may have a different circuit configuration. The same applies to the second voltage detection circuit 8.

[0059] FIG. 10 shows an example in which the detection voltages V1 and V2 vary between zero volts and 5 volts, but this is also just one example, and the upper and lower limits of the range in which the detection voltages V1 and V2 vary may be other values.

[0060] In the above-described embodiment, the vehicle tailgate 51 is given as an example of an object to be driven by the first motor 3 and the second motor 4, but the present invention can also be applied to a control device for an electric motor that drives an object other than a tailgate. [Explanation of symbols]

[0061] 1. Control section 2 Motor drive circuit 3 First motor 4 Second motor 5 First shunt resistor 6 Second shunt resistor 7 First voltage detection circuit 8 Second voltage detection circuit 51 Tailgate V1 Voltage across the first shunt resistor V2 Voltage across the second shunt resistor α First threshold β Second Threshold 100 Electric motor control device

Claims

1. A single motor drive circuit that drives a plurality of electric motors connected in parallel in forward or reverse rotation; a single control unit that outputs a control signal for controlling the rotation of each of the electric motors to the motor drive circuit; a plurality of shunt resistors provided between each of the electric motors and the motor drive circuit; a plurality of voltage detection circuits each detecting a voltage across each of the shunt resistors; The control unit is When the control signal is a forward rotation command for commanding forward rotation of each of the electric motors, the presence or absence of a fault in a current path of each of the electric motors is detected based on a comparison result between the voltage across each shunt resistor detected by the voltage detection circuit and a first threshold value set in advance; an electric motor control device which, when the control signal is a reverse rotation command that commands the reverse rotation of each of the electric motors, detects the presence or absence of a fault in the current path of each of the electric motors based on a comparison result between the voltage across each shunt resistor detected by the voltage detection circuit and a preset second threshold value.

2. 2. The electric motor control device according to claim 1, The control unit is an electric motor control device that, when the control signal is the forward rotation command, determines that an open circuit fault has occurred in the current path of the electric motor connected to the shunt resistor if any of the voltages across the shunt resistors is below the first threshold value.

3. 2. The electric motor control device according to claim 1, The control unit is an electric motor control device that, when the control signal is the reverse rotation command, determines that an open circuit fault has occurred in the current path of the electric motor connected to the shunt resistor if any of the voltages across each of the shunt resistors is equal to or higher than the second threshold value.

4. 4. The electric motor control device according to claim 1, the first threshold value is greater than a voltage across each of the shunt resistors when each of the electric motors is in a stopped state, The electric motor control device according to claim 1, wherein the second threshold value is smaller than a voltage across each of the shunt resistors when each of the electric motors is in a stopped state.

5. A single motor drive circuit that drives a plurality of electric motors connected in parallel in forward or reverse rotation; a single control unit that outputs a control signal for controlling the rotation of each of the electric motors to the motor drive circuit; a plurality of shunt resistors provided between each of the electric motors and the motor drive circuit; A method for detecting a fault in an electric motor control device comprising: the control unit outputs the control signal to the motor drive circuit; When the control signal is a forward rotation command for commanding forward rotation of each of the electric motors, the control unit compares the voltage across each of the shunt resistors detected by the voltage detection circuit with a first threshold value set in advance; When the control signal is a reverse rotation command for commanding the reverse rotation of each of the electric motors, the control unit compares the voltage across each of the shunt resistors detected by the voltage detection circuit with a second threshold value set in advance; and a step in which the control unit detects the presence or absence of a fault in the current path of each of the electric motors based on a comparison result between the voltages at both ends and each of the threshold values.

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