Anomaly detection device

Abstract

To provide an abnormality detection device which can eliminate a pull-up resistor for voltage monitoring.SOLUTION: A pull-down resistor Rdu is composed of two voltage dividing resistors Rdu1 and Rdu2 which divide voltage between an inter-arm connection point Nu being a connection point between an upper arm element 61 and a lower arm element 64 and the ground, and connects the inter-arm connection point Nu and the ground. A determination unit 25 detects abnormality of at least the upper arm element 61 and the lower arm element 64 based on voltage of a voltage dividing point Du being the connection point of the two voltage dividing resistors Rdu1 and Rdu2. A power supply line Lp and the inter-arm connection point are not connected through a pull-up resistor. The determination unit 25 detects ON fastening abnormality and OFF fastening abnormality of the upper arm element 61 and the lower arm element 64 based on voltage of the voltage dividing point Du when leak current IL flows to the ground from an upper arm element drive circuit 31 through the pull-down resistor Rdu during operation of the upper arm element drive circuit 31.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an abnormality detection device.

Background Art

[0002] Conventionally, in the initial check of a circuit that supplies power to a multiphase motor, a device for detecting abnormalities such as a relay composed of semiconductor switching elements is known.

[0003] For example, in the abnormality detection device disclosed in Patent Document 1, pull-up resistors and pull-down resistors are connected to the upper and lower arm connection points of each phase of an inverter. The pull-down resistor of each phase is composed of two series-connected voltage-dividing resistors. The determination unit determines an ON-stuck abnormality (short circuit failure) and an OFF-stuck abnormality (open circuit failure) of the motor relay based on the voltage at the voltage-dividing point, which is the connection point of the two voltage-dividing resistors.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the prior art of Patent Document 1, at least the pull-down resistor among the pull-up resistor and pull-down resistor for voltage monitoring is provided inside the drive circuit IC, thereby suppressing an increase in the substrate mounting area. However, the idea of detecting abnormalities using the voltage obtained by stepping down the voltage of the power supply line with the pull-up resistor is fundamental. Whether the pull-up resistor is provided inside the drive circuit IC or mounted on the substrate, it remains necessary as a component. In particular, in a configuration where the pull-up resistor is mounted on the substrate, there is room to further reduce the substrate mounting area, but Patent Document 1 does not mention at all the possibility of deleting the pull-up resistor.

[0006] This invention was created in view of the above-mentioned points, and its purpose is to provide an anomaly detection device that allows the removal of pull-up resistors for voltage monitoring. [Means for solving the problem]

[0007] The abnormality detection device of the present invention comprises an inverter (60), upper arm element drive circuits (31, 32, 33), lower arm element drive circuits (34, 35, 36), a plurality of pull-down resistors (Rdu, Rdv, Rdw), and a determination unit (25).

[0008] The inverter is configured by bridging multiple phase upper arm elements (61, 62, 63) and lower arm elements (64, 65, 66) between a power line (Lp) connected to a battery (15) and a ground line (Lg), and converts the DC power from the battery to supply to each phase winding (81, 82, 83) of a multiphase motor (80). The upper arm element drive circuit outputs a gate signal to the upper arm elements. The lower arm element drive circuit outputs a gate signal to the lower arm elements.

[0009] Multiple pull-down resistors consist of two voltage divider resistors per phase, which divide the voltage between the inter-arm connection points (Nu, Nv, Nw), which are the connection points between the upper and lower arm elements of each phase, and ground, connecting the inter-arm connection points to ground. The determination unit detects abnormalities in at least the upper arm element and the lower arm element based on the voltage at the voltage divider point, which is the connection point of the two voltage divider resistors.

[0010] The power lines and the connection points between each phase of the tonearms are not connected via pull-up resistors.

[0011] The determination unit detects ON and OFF locking abnormalities of the upper arm element and lower arm element based on the voltage at the voltage division point when leakage current flows from the upper arm element drive circuit to ground via the pull-down resistor during operation of the upper arm element drive circuit.

[0012] In this invention, instead of using a voltage obtained by stepping down the power line voltage with a pull-up resistor, abnormality detection is performed using the voltage generated by the leakage current from the upper arm element drive circuit flowing through a pull-down resistor. By eliminating the pull-up resistor used for voltage monitoring, the number of components can be reduced, and the board mounting area that would otherwise be occupied by the pull-up resistor can be further reduced.

[0013] In Patent Document 1, it is stated that "the leakage current from the (upper arm element) drive circuit to the pull-down resistor increases the voltage float, becoming a source of error," thus recognizing leakage current as a drawback. It also describes stopping the operation of the drive circuit to cut the leakage current when an abnormality is detected in the motor relay as a means of reducing errors. In contrast, the present invention takes a reverse approach by actively utilizing the leakage current as a voltage source for voltage monitoring, thereby enabling the elimination of the pull-up resistor. [Brief explanation of the drawing]

[0014] [Figure 1] Circuit diagram of an abnormality detection device according to one embodiment. [Figure 2] Figure 1 shows the configuration for monitoring the voltage of one phase of the U-phase. [Figure 3] (a) Diagram for determining abnormal ON locking of the upper arm element, (b) Diagram for determining abnormal ON locking of the upper arm element with the operation of the upper arm element drive circuit stopped (with leak cut). [Figure 4] Diagram for determining abnormal OFF locking of the upper arm element. [Figure 5] Diagram for determining abnormal ON locking of the lower arm element. [Figure 6] Diagram for determining abnormality in the lower arm element being stuck in the OFF position. [Figure 7] Diagram of the normal current path during a check for an ON-fixed U-phase motor relay. [Figure 8] Diagram of the current path during abnormal current flow when checking for an ON-fixed U-phase motor relay. [Figure 9] Diagram for determining abnormalities in U-phase motor relay being stuck ON. [Figure 10]Diagram of the normal current path during the U-phase motor relay OFF stuck abnormality check. [Figure 11] Diagram of the abnormal current path during the U-phase motor relay OFF stuck abnormality check. [Figure 12] Judgment diagram of U-phase motor relay OFF stuck abnormality.

Mode for Carrying Out the Invention

[0015] (One Embodiment) An abnormality detection device according to an embodiment of the present invention will be described based on the drawings. The abnormality detection device of this embodiment is applied to a circuit that supplies power to a multiphase motor used, for example, as a steering assist motor of an electric power steering device. This abnormality detection device detects ON stuck abnormalities (short circuit failures) and OFF stuck abnormalities (open circuit failures) of the upper and lower arm elements of the inverter and the motor relay during the initial check of the power supply circuit.

[0016] Specifically, similar to Patent Document 1 (Japanese Patent Application Laid-Open No. 2020-174419, corresponding US publication: US2020 / 0321902A1), the ECU of the electric power steering device functions as an abnormality detection device. The ECU is composed of a microcomputer, a pre-driver, etc., and includes a CPU, ROM, RAM, I / O not shown, and bus lines connecting these components. The ECU executes control by software processing in which a program stored in advance is executed by the CPU and by hardware processing using a dedicated electronic circuit.

[0017] The configuration of one embodiment is shown in FIG. 1. In this embodiment, a three-phase motor 80 is used as the "multiphase motor". Hereinafter, the three-phase motor 80 will be simply referred to as the motor 80. The ECU 10 as an abnormality detection device supplies the three-phase AC power generated by the inverter 60 to the three-phase windings 81, 82, 83 of the motor 80. For example, in the case of the Y-connected motor 80, the three-phase windings 81, 82, 83 are connected at the neutral point 84. Note that the three-phase windings 81, 82, 83 may be Δ-connected.

[0018] After the vehicle switch is turned ON, the ECU10 performs an initial check before the motor starts driving to detect any abnormalities in the power supply circuit to the motor. If the initial check determines that the power supply circuit to the motor 80 is normal, the ECU10 controls the drive of the motor 80 based on the steering torque so that the motor 80 generates the desired assist torque.

[0019] The ECU10 includes a smoothing capacitor 55, an inverter 60, motor relays 71, 72, and 73, a drive circuit IC 30, and a microcontroller 20, etc. The internal configuration of the drive circuit IC 30 will be described later. The microcontroller 20 has a determination unit 25 that detects abnormalities in the target element.

[0020] The inverter 60 is connected to the positive terminal of the battery 15 via the power line Lp and to the negative terminal of the battery 15 via the ground line Lg. The inverter 60 is constructed by bridging three phases, namely U-phase, V-phase, and W-phase upper arm elements 61, 62, 63 and lower arm elements 64, 65, 66, between the power line Lp and the ground line Lg. Hereinafter, the upper arm elements 61, 62, 63 and lower arm elements 64, 65, 66 may be collectively referred to as "upper and lower arm elements 61-66". The inverter 60 converts the DC power from the battery 15 and supplies it to the three-phase windings 81, 82, 83 of the motor 80.

[0021] A smoothing capacitor 55 provided at the input of the inverter 60 smooths the input voltage to the inverter 60. A power relay or a reverse connection protection relay may be provided in the power line Lp from the battery 15 to the inverter 60.

[0022] In the inverter 60, the connection points between the upper arm elements 61, 62, 63 and the lower arm elements 64, 65, 66 of each phase are defined as "arm connection points Nu, Nv, Nw". Motor relays 71, 72, 73 are provided in the motor current path that connects the arm connection points Nu, Nv, Nw of each phase of the inverter 60 to the three-phase windings 81, 82, 83 of the motor 80. Parasitic diodes are connected in parallel to the motor relays 71, 72, 73, which conduct current from the inverter 60 to the motor 80, and when OFF, they interrupt the current from the motor 80 to the inverter 60.

[0023] In this embodiment, the upper and lower arm elements 61-66 and the motor relays 71, 72, and 73 are composed of MOSFETs. In the motor relays 71, 72, and 73, the parasitic diodes of the MOSFETs conduct current from the inverter 60 side to the motor 80 side. In the upper and lower arm elements 61-66, the parasitic diodes of the MOSFETs conduct current from the low potential side to the high potential side.

[0024] In this document, Figure 2 of Patent Document 1 shows pull-up resistors Ruu, Ruv, and Ruw connecting the power line Lp to the motor current paths of each phase. In contrast, in this embodiment, the power line Lp and the inter-arm connection points Nu, Nv, and Nw of each phase are not connected via pull-up resistors. In other words, in the ECU 10 of this embodiment, pull-up resistors have been eliminated compared to the prior art.

[0025] The drive circuit IC30 is a customized integrated IC. Inside the drive circuit IC30 are upper arm element drive circuits 31, 32, 33, lower arm element drive circuits 34, 35, 36, motor relay drive circuits 371, 372, 373, pull-down resistors Rdu, Rdv, Rdw for each phase, a multiplexer 38, and an amplification circuit 39.

[0026] The upper arm element drive circuits 31, 32, and 33 output gate signals to the upper arm elements 61, 62, and 63. The lower arm element drive circuits 34, 35, and 36 output gate signals to the lower arm elements 64, 65, and 66. The motor relay drive circuits 371, 372, and 373 output gate signals to the motor relays 71, 72, and 73.

[0027] In the diagram, the "upper arm element drive circuits 31, 32, 33" block is actually divided into three blocks: U-phase upper arm element drive circuit 31, V-phase upper arm element drive circuit 32, and W-phase upper arm element drive circuit 33. However, for space reasons, they are shown together as one block. The thin arrows pointing from the upper arm element drive circuits 31, 32, 33 blocks towards the dashed-dotted frame surrounding the upper arm elements 61, 62, 63 represent the gate signals to the upper arm elements 61, 62, 63 for each phase.

[0028] The same applies to the lower arm element drive circuits 34, 35, and 36 and the motor relay drive circuits 371, 372, and 373. The block for "lower arm element drive circuits 34, 35, and 36" represents the U-phase lower arm element drive circuit 34, the V-phase lower arm element drive circuit 35, and the W-phase lower arm element drive circuit 36 ​​collectively. The block for "motor relay drive circuits 371, 372, and 373" represents the U-phase motor relay drive circuit 371, the V-phase motor relay drive circuit 372, and the W-phase motor relay drive circuit 373 collectively.

[0029] Furthermore, the dashed lines connecting the blocks of the "upper arm element drive circuits 31, 32, and 33" to the inter-arm connection points Nu, Nv, and Nw of each phase indicate the path of the leakage current IL that flows when the upper arm element drive circuits 31, 32, and 33 are operating. The technical significance of the leakage current IL in this embodiment will be described later.

[0030] The pull-down resistors Rdu, Rdv, and Rdw consist of two voltage divider resistors per phase, dividing the voltage between the arm connection points Nu, Nv, and Nw and ground, and connecting the arm connection points Nu, Nv, and Nw to ground. Of the two voltage divider resistors for each phase, the voltage divider resistors on the arm connection point Nu, Nv, and Nw side are denoted as the first voltage divider resistors Rdu1, Rdv1, and Rdw1, and the voltage divider resistors on the ground side are denoted as the second voltage divider resistors Rdu2, Rdv2, and Rdw2. The connection points of the two voltage divider resistors are denoted as voltage divider points Du, Dv, and Dw.

[0031] The voltages at the voltage divider points Du, Dv, and Dw of each phase are input to the multiplexer (indicated as "MPX" in the figure) 38. The multiplexer 38 selects the voltage at the voltage divider point Du, Dv, and Dw of any of the phases and outputs it to the amplification circuit 39. The amplification circuit 39 outputs monitor voltages Vua, Vva, and Vwa, which are amplified from the voltage at the voltage divider point Du, Dv, and Dw of the selected phase, to the determination unit 25.

[0032] The determination unit 25 directly detects abnormalities in the upper and lower arm elements 61-66 and motor relays 71, 72, and 73 of the inverter 60 based on the monitor voltages Vua, Vva, and Vwa. Fundamentally, the determination unit 25 detects abnormalities in the upper and lower arm elements 61-66 and motor relays 71, 72, and 73 based on the voltages at the voltage divider points Du, Dv, and Dw when leakage current IL flows from the upper arm element drive circuits 31, 32, and 33 to ground via the pull-down resistors Pdu, Pdv, and Pdw during operation of the upper arm element drive circuits 31, 32, and 33. The dashed arrow from the microcontroller 20 to the drive circuit IC 30 indicates a collection of various signals.

[0033] Next, referring to Figure 2, the configuration for monitoring the voltage of one phase of the U-phase will be explained. Figure 2 is roughly equivalent to Figure 4 of Patent Document 1, but without the pull-up resistor Ruu connected in parallel with the U-phase upper arm element 61. As for minor differences, in Figure 2 of this embodiment, the FETs in each drive circuit 31, 34, and 371 are omitted, and the drive circuit including the FETs is described. Also, the specific circuit diagram of the amplification circuit 39 is omitted, and only the block is shown.

[0034] The symbols for voltage divider resistors will be "Rdu1, Rdu2" instead of "RduH, RduL" in Patent Document 1. The symbol for leakage current will be "IL" instead of "Lc" in Patent Document 1. In addition, Figure 2 of this embodiment basically shares the same reference numerals and symbols as Figure 4 of Patent Document 1.

[0035] Figure 2 shows the U-phase as a representative example, and the symbols for the components of the U-phase are used in the explanatory text. The V-phase and W-phase have similar configurations. The microcontroller 20 and the drive circuit IC 30 are mounted as chips on the substrate 50, as well as the MOSFETs that constitute the upper arm element 61, the lower arm element 64, and the motor relay 71.

[0036] The drive circuit IC30 contains an upper arm element drive circuit 31, a lower arm element drive circuit 34, and a motor relay drive circuit 371. The drive circuit IC30 also includes a pull-down resistor Rdu, composed of two series-connected voltage divider resistors Rdu1 and Rdu2, a multiplexer 38, and an amplification circuit 39. The multiplexer 38 is configured to receive the voltage of the U-phase voltage divider point Du. The terminals 41-49 of the drive circuit IC30 are the same as those described in Patent Document 1, so their description is omitted.

[0037] When the upper arm element drive circuit 31 is operating, a leakage current IL flows from the upper arm element drive circuit 31 to ground via the pull-down resistor Rdu, as shown by the thick arrow. Specifically, a larger leakage current IL flows when the upper arm element 61 is ON than when the upper arm element 61 is OFF. When the operation of the upper arm element drive circuit 31 stops, no leakage current IL flows. When the upper arm element drive circuit 31 is operating and both the upper arm element 61 and the lower arm element 64 are OFF, the motor terminal voltage V*mt (*=u,v,w), which is the voltage at the inter-arm connection points Nu, Nv, and Nw of each phase, is expressed by equation (1). Here, R1 is the resistance value of the first voltage divider resistor Rd*1, and R2 is the resistance value of the second voltage divider resistor Rd*2.

[0038] V*mt=(R1+R2)×IL ···(1)

[0039] Furthermore, the relationship between the monitor voltage V*a input to the determination unit 25 and the motor terminal voltage V*mt (*=u,v,w) is expressed by equation (2), where G is the amplification factor of the amplification circuit 39. In circuits where the amplification circuit 39 is not provided, G is assumed to be 1. Thus, in this embodiment, abnormality detection is performed using the voltage generated by the leakage current IL.

[0040] V*a = G × V*mt × R2 / (R1 + R2) =G × R² × IL ···(2)

[0041] The prior art described in Patent Document 1 is based on the idea of ​​detecting anomalies by using the voltage obtained by stepping down the voltage of the power line Lp with a pull-up resistor. Therefore, whether the pull-up resistor is provided inside the drive circuit IC 30 as shown in Figure 3 of Patent Document 1, or mounted on the circuit board 50 as shown in Figure 4, it is still necessary as a component. In particular, in the configuration of Figure 4 in which the pull-up resistor is mounted on the circuit board, there is room to further reduce the mounting area on the circuit board, but Patent Document 1 does not mention at all the possibility of eliminating the pull-up resistor.

[0042] Furthermore, paragraphs

[0045] and

[0046] of Patent Document 1 state that "the leakage current from the upper arm element drive circuit to the pull-down resistor increases the voltage float and becomes a source of error," and that "by stopping the operation of the upper arm element drive circuit when an abnormality is detected, the leakage current flowing to the pull-down resistor can be cut, and the effect of errors can be minimized." Thus, in Patent Document 1, leakage current IL is recognized as a drawback.

[0043] In contrast, this embodiment utilizes the leakage current IL as a voltage source for voltage monitoring, a reverse approach that makes it possible to eliminate the pull-up resistor. By eliminating the pull-up resistor for voltage monitoring in this embodiment, the number of components can be reduced, and the board mounting area that would otherwise be occupied by the pull-up resistor can be further reduced. Furthermore, since the upper arm element drive circuit 31 and the pull-down resistor Rdu are provided inside the same drive circuit IC 30, there are no terminal connections in the path of the leakage current IL, and the voltage becomes stable.

[0044] Next, the specific methods for detecting abnormalities in the upper and lower arm elements 61-66 and motor relays 71, 72, and 73 according to this embodiment will be described in order. First, referring to Figures 3 to 6, the detection of ON-locking abnormalities and OFF-locking abnormalities in the upper arm elements 61, 62, and 63 and the lower arm elements 64, 65, and 66 will be described. In the description, based on Figure 2, the reference numerals for the U-phase upper arm element 61 and lower arm element 64 will be used as representatives.

[0045] In principle, the determination unit 25 detects ON-locking abnormalities and OFF-locking abnormalities of the upper arm element 61 and lower arm element 64 based on the voltage at the voltage divider point Du when leakage current flows from the upper arm element drive circuit 31 to ground via the pull-down resistor Pdu during the operation of the upper arm element drive circuit 31. Here, "stopping the operation of the upper arm element drive circuit 31 and cutting the leakage current IL" is called "leak cut". In this embodiment, the leakage current IL is not cut in principle. Figures 4 to 6 show abnormality determination diagrams without leak cut, as per the principle. However, for the ON-locking abnormality check of the upper arm element 61, the cases of "no leak cut" and "with leak cut" are shown separately in Figures 3(a) and 3(b).

[0046] The vertical axis in each figure shows the value converted to the motor terminal voltage V*mt (*=u,v,w), rather than the monitor voltage V*a itself acquired by the determination unit 25. When both the upper arm element 61 and the lower arm element 64 are OFF, the value of equation (1) is "(R1+R2)×IL".

[0047] For the detection of ON and OFF locking abnormalities of the upper arm element 61, refer to Figures 3(a), 3(b), and 4. It is obvious that the upper arm element 61 is turned OFF when an ON locking abnormality is checked and turned ON when an OFF locking abnormality is checked. The lower arm element 64 is turned OFF during either check.

[0048] As shown in Figure 3(a), during the ON locking abnormality check of the upper arm element 61, when it is normally OFF, the motor terminal voltage Vumt is "(R1+R2)×IL" and falls below the threshold Vth_H. On the other hand, when the lower arm element 64 is ON locking abnormally, the motor terminal voltage Vumt rises in the range above the threshold Vth_H as the battery voltage increases.

[0049] Incidentally, in the ON-fixed abnormality check of the upper arm element 61, the upper arm element 61 is turned OFF, so the operation of the upper arm element drive circuit 31 may be stopped to create a leak-cut state. In this case, the determination unit 25 can detect the ON-fixed abnormality of the upper arm element 61 with the operation of the upper arm element drive circuit 31 stopped. As shown in Figure 3(b), with leak cut enabled, the motor terminal voltage Vumt in the normal OFF state will be near ground. This allows for a larger margin against false detections.

[0050] In checking for an OFF locking abnormality of the upper arm element 61, it is necessary to turn the upper arm element 61 ON, so it is not possible to stop the operation of the upper arm element drive circuit 31 and cut the leakage current IL. As shown in Figure 4, the motor terminal voltage Vumt when the upper arm element 61 is normally ON increases with the increase in battery voltage within a range that exceeds the threshold Vth_H. On the other hand, when the upper arm element 61 is OFF locking abnormally, the motor terminal voltage Vumt becomes "(R1+R2)×IL", which falls below the threshold Vth_H.

[0051] Next, regarding the detection of ON and OFF locking abnormalities of the lower arm element 64, please refer to Figures 5 and 6. It is obvious that the lower arm element 64 is turned OFF when checking for an ON locking abnormality and turned ON when checking for an OFF locking abnormality. The upper arm element 61 is always turned OFF.

[0052] As shown in Figure 5, during the ON-fixed abnormality check of the lower arm element 64, the motor terminal voltage Vumt during normal OFF is "(R1+R2)×IL", which exceeds the threshold Vth_L. On the other hand, the motor terminal voltage Vumt during the ON-fixed abnormality of the lower arm element 64 is close to ground and falls below the threshold Vth_L. If leakage cut is performed, the voltage during normal OFF decreases, making abnormality detection difficult. Therefore, leakage cut cannot be performed during the ON-fixed abnormality check of the lower arm element 64.

[0053] As shown in Figure 6, during the OFF locking abnormality check of the lower arm element 64, the motor terminal voltage Vumt when the lower arm element 64 is normally ON is near ground and falls below the threshold Vth_L. On the other hand, when the lower arm element 64 is OFF locking abnormally, the motor terminal voltage Vumt becomes "(R1+R2)×IL" and exceeds the threshold Vth_L.

[0054] As described above, by utilizing the leakage current flowing from the upper arm element drive circuit of each phase to ground via the pull-down resistor for detecting ON and OFF locking abnormalities of the upper and lower arm elements 61-66 of the inverter 60, the pull-up resistor for voltage monitoring can be eliminated compared to the conventional technology. Preferably, the determination unit 25 detects the ON locking abnormality of the upper arm elements 61, 62, and 63 while the operation of the upper arm element drive circuits 31, 32, and 33 is stopped, thereby ensuring a larger margin against false detections.

[0055] Next, referring to Figures 7 to 12, the detection of ON and OFF sticking abnormalities in motor relays 71, 72, and 73 will be explained. The phase that is the target of abnormality detection is called the target phase. In addition, of the two phases other than the target phase, one or two phases whose voltage at the voltage division point is used for abnormality detection by the determination unit 25 are called the monitor phases. Here, the case in which the U phase is the target phase and the V phase is the monitor phase will be explained as an example. When the U phase is the target phase, the W phase may be selected as the monitor phase instead of or in addition to the V phase. In Figure 7, etc., the multiplexer 38 and the amplification circuit 39 are omitted from the illustration.

[0056] The determination unit 25 detects abnormalities by utilizing the voltage generated when the leakage current from the upper arm element drive circuit of the monitor phase flows through the pull-down resistor. In detecting abnormalities in the motor relay, the operation of the upper arm element drive circuit of the monitor phase is not stopped to cut the leakage current IL. In this respect, this embodiment is clearly different from the conventional method described in Patent Document 1.

[0057] Refer to Figures 7 to 9 for the ON-fixed abnormality check of the U-phase motor relay 71. It is obvious that when the ON-fixed abnormality check is performed, the motor relay 71 of the target phase, the U-phase, is turned OFF. In addition, in the inverter 60, the upper arm elements 61, 62, and 63 of all phases, and the lower arm elements 65 and 66 of the two phases other than the target phase, the V-phase and W-phase, are turned OFF, and the lower arm element 64 of the target phase, the U-phase, is turned ON. Also, the motor relay 73 of the W-phase, which is "a phase other than the target phase and a phase other than the monitor phase," is turned OFF.

[0058] The V-phase motor relay 72, which is the monitoring phase, can be either OFF or ON. When the V-phase motor relay 72 is OFF, the current flowing from the inverter 60 to the motor 80 passes through the parasitic diode of the MOSFET, resulting in a voltage drop Vf across the parasitic diode. When the V-phase motor relay 72 is ON, current flows through the MOSFET element itself, so the voltage drop is close to zero.

[0059] As shown in Figure 7, when the U-phase motor relay 71 is in the normal OFF state, the path from the neutral point 84 of the motor 80 through the U-phase lower arm element 64 to ground is interrupted by the U-phase motor relay 71, and all of the leakage current IL from the V-phase upper arm element drive circuit 32 flows through the pull-down resistor Rdv. As shown in Figure 9, the motor terminal voltage Vvmt in the normal OFF state becomes "(R1+R2)×IL", which exceeds the threshold Vth_M.

[0060] As shown in Figure 8, when the U-phase motor relay 71 is stuck ON, the path from the neutral point 84 of the motor 80 through the U-phase motor relay 71 and the U-phase lower arm element 64 to ground becomes conductive. Therefore, as shown by the dashed line, only a small leakage current IL flows through the pull-down resistor Rdv.

[0061] As shown in Figure 9, regardless of whether the V-phase motor relay 72 is ON or OFF, the motor terminal voltage Vvmt during an ON lockout abnormality is below the threshold Vth_M. When the V-phase motor relay 72 is OFF, the motor terminal voltage Vvmt during an ON lockout abnormality is equivalent to the voltage drop Vf across the parasitic diode. In contrast, when the V-phase motor relay 72 is ON, the motor terminal voltage Vvmt during an ON lockout abnormality is near ground, providing a larger margin against false detections.

[0062] Next, refer to Figures 10 to 12 for checking for OFF sticking abnormalities in the U-phase motor relay 71. It is self-evident that the motor relay 71 of the target phase, the U-phase, will be operated ON when checking for OFF sticking abnormalities. In addition, the ON / OFF status of the upper and lower arm elements 61-66 of the inverter 60, the motor relay 73 of the W-phase (a phase other than the monitor phase), and the motor relay 72 of the V-phase (a monitor phase) is the same as for checking for ON sticking abnormalities.

[0063] The current path during normal ON operation shown in Figure 10 is the same as the current path during ON-lock abnormality shown in Figure 8. The current path during OFF-lock abnormality shown in Figure 11 is the same as the current path during normal OFF operation shown in Figure 7. Therefore, as shown in Figure 12, the motor terminal voltage Vvmt during OFF-lock abnormality becomes "(R1+R2)×IL", which exceeds the threshold Vth_M.

[0064] Furthermore, as shown in Figure 12, regardless of whether the V-phase motor relay 72 is ON or OFF, the motor terminal voltage Vvmt in the normal ON state is below the threshold Vth_M. When the V-phase motor relay 72 is OFF, the motor terminal voltage Vvmt in the normal ON state is equivalent to the voltage drop Vf across the parasitic diode. In contrast, when the V-phase motor relay 72 is ON, the motor terminal voltage Vvmt in the normal ON state is near ground, allowing for a larger margin against false detections.

[0065] As described above, the detection of ON and OFF locking abnormalities of the target phase motor relay can also be achieved by utilizing the leakage current IL that flows from the upper arm element drive circuit of the monitor phase to ground via the pull-down resistor, thereby eliminating the pull-up resistor for voltage monitoring compared to conventional technology. Preferably, the determination unit 25 detects ON and OFF locking abnormalities of the target phase U phase motor relay 71 based on the voltage at the voltage division point Dv of the monitor phase when the leakage current IL flows while the V phase motor relay 72, which is the monitor phase, is ON. This allows for a larger margin against false detections.

[0066] (Other embodiments) (a) The abnormality detection device of the present invention may be applied to a power supply circuit that does not have a motor relay. In that case, the determination unit 25 only needs to detect abnormalities in at least the upper arm elements 61, 62, 63 and the lower arm elements 64, 65, 66.

[0067] (b) The pull-down resistors Pdu, Pdv, Pdw, the multiplexer 38, and the amplification circuit 39 are not limited to being located inside the drive circuit IC 30, but may also be mounted on the board. The determination unit 25 is not limited to being located inside the microcontroller 20, but may also be configured as a logic circuit on the board.

[0068] (c) Instead of providing a multiplexer 38 on the output side of the voltage divider points Du, Dv, and Dw of each phase, an amplification circuit 39 may be provided for each phase. In that case, a multiplexer 38 may be provided on the output side of the amplification circuit 39 of each phase, and the monitor terminal may be made common.

[0069] (d) The upper and lower arm elements 61-66 and the motor relays 71, 72, and 73 are not limited to MOSFETs but may be composed of other semiconductor switching elements. For example, a freewheeling diode connected in parallel to a bipolar transistor is considered equivalent to a parasitic diode in a MOSFET.

[0070] (e) The abnormality detection device of the present invention may have a two-system configuration applied to a multiphase motor having two sets of multiphase windings, as disclosed in Patent Document 1. The multiphase motor is not limited to a three-phase motor, but may be a motor with four or more phases. Furthermore, the multiphase motor is not limited to a steering assist motor for an electric power steering system, but may be a motor for other applications.

[0071] The present invention is not limited to the embodiments described above, and can be implemented in various forms without departing from its spirit.

[0072] The invention of "...an abnormality detection device according to claim 1, further comprising a plurality of motor relays (71, 72, 73) and motor relay drive circuits (371, 372, 373), wherein the determination unit detects ON-fixed abnormalities and OFF-fixed abnormalities of the motor relay of the target phase based on the voltage at the voltage divider point when the leakage current flows," may be referenced by claim 1 or 2 if the description requirements are permissible.

[0073] The anomaly detection device and method described herein may be implemented by a dedicated computer provided by configuring a processor and memory programmed to perform one or more functions embodied by a computer program. Alternatively, the anomaly detection device and method described herein may be implemented by a dedicated computer provided by configuring a processor by one or more dedicated hardware logic circuits. Alternatively, the anomaly detection device and method described herein may be implemented by one or more dedicated computers configured by a combination of a processor and memory programmed to perform one or more functions and a processor configured by one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by the computer on a computer-readable non-transitional tangible recording medium. [Explanation of symbols]

[0074] 10. ECU (Anomaly Detection Unit), 15...Battery, 25...judgment section, 31, 32, 33... Upper arm element drive circuit, 34, 35, 36... Lower arm element drive circuit, 60...inverter, 61, 62, 63... Upper arm elements, 64, 65, 66... ​​Lower arm elements, 71, 72, 73... Motor relays, 80 ···(multiphase) motor, Nu, Nv, Nw... connection points between arms, Rdu, Rdv, Rdw... Pull-down resistors.

Claims

1. The inverter (60) is configured by bridging multiple phase upper arm elements (61, 62, 63) and lower arm elements (64, 65, 66) between the power line (Lp) and ground line (Lg) connected to the battery (15), and converts the DC power of the battery to supply each phase winding (81, 82, 83) of the multiphase motor (80). The upper arm element drive circuit (31, 32, 33) outputs a gate signal to the upper arm element, The lower arm element drive circuit (34, 35, 36) outputs a gate signal to the lower arm element, Each phase consists of two voltage divider resistors that divide the voltage between the arm connection points (Nu, Nv, Nw), which are the connection points between the upper and lower arm elements of each phase, and ground, and a plurality of pull-down resistors (Rdu, Rdv, Rdw) that connect the arm connection points and ground, The system includes a determination unit (25) that detects abnormalities in at least the upper arm element and the lower arm element based on the voltage at the voltage division point, which is the connection point of the two voltage division resistors. The power line and the connection points between the arms of each phase are not connected via pull-up resistors. The determination unit is an abnormality detection device that detects ON-fixation abnormalities and OFF-fixation abnormalities of the upper arm element and the lower arm element based on the voltage at the voltage divider point when leakage current flows from the upper arm element drive circuit to ground via the pull-down resistor during operation of the upper arm element drive circuit.

2. The abnormality detection device according to claim 1, wherein the determination unit detects an ON-fixation abnormality of the upper arm element while the operation of the upper arm element drive circuit is stopped.

3. Multiple motor relays (71, 72, 73) are provided in the motor current path connecting the arm connection points of each phase of the inverter to the windings of each phase of the multiphase motor, and are connected in parallel to parasitic diodes that conduct current from the inverter side to the multiphase motor side, and interrupt the current from the multiphase motor side to the inverter side when OFF, The motor relay drive circuit (371, 372, 373) that outputs a gate signal to the motor relay further comprises The abnormality detection device according to claim 1, wherein the determination unit detects ON-fixed abnormalities and OFF-fixed abnormalities of the motor relay of the target phase based on the voltage at the voltage division point when the leakage current flows.

4. The aforementioned multiphase motor is a three-phase motor, and if one or two of the two phases other than the target phase, whose voltage at the voltage division point is used for abnormality detection by the determination unit, are designated as the monitor phase, The abnormality detection device according to claim 3, wherein the determination unit detects ON-fixed abnormalities and OFF-fixed abnormalities of the motor relay of the target phase based on the voltage at the voltage divider point of the monitor phase when the leakage current flows, while the upper arm elements of all phases and the lower arm elements of two phases other than the target phase are OFF, the lower arm element of the target phase is ON, and the motor relays of at least the phases other than the target phase and the monitor phase are OFF.

5. The abnormality detection device according to claim 4, wherein the determination unit detects an ON-fixed abnormality and an OFF-fixed abnormality of the motor relay of the target phase based on the voltage at the voltage divider point of the monitor phase when the leakage current flows while the motor relay of the monitor phase is ON.

6. The abnormality detection device according to any one of claims 1 to 5, wherein the pull-down resistor is provided inside the drive circuit IC (30) in which the upper arm element drive circuit is built.

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