Vehicle control device

Abstract

To provide a vehicle control device capable of suppressing a reduction in a drivable range when a short-circuit failure occurs in an inverter that drives an electric motor.SOLUTION: An electronic control device 90 of a vehicle 10, which comprises: an engine 12; a power split mechanism 22 which divides power of the engine 12 between a first electric motor MG1 and an output shaft 24 connected to a pair of drive wheels 14; and a second electric motor MG2 connected to the output shaft 24 so as to be capable of transmitting power, (a) executes identification control to identify a short circuit phase in a first inverter 50 while the engine 12 is in operation when the first inverter 50 to drive the first electric motor MG1 is in an abnormal state; and (b) executes 3-phase ON control of the first inverter 50 when the short circuit phase is identified through the identification control and controls an engine rotation speed Ne so that a MG1 rotation speed Nmg1 falls within a control range Nmg1_ctrl which is a predetermined rotation speed range.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a control device for a vehicle including an engine, a power split mechanism that splits the power of the engine into a first electric motor and a rotating member connected to a pair of drive wheels, and a second electric motor connected to the rotating member so as to be able to transmit power.

Background Art

[0002] A control device for a vehicle including an engine, a power split mechanism that splits the power of the engine into a first electric motor and a rotating member connected to a pair of drive wheels, and a second electric motor connected to the rotating member so as to be able to transmit power is known. For example, the one described in Patent Document 1 is such a device.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the control device for a vehicle described in Patent Document 1, when a short-circuit failure occurs in the inverter that drives the first electric motor, the inverter is controlled to be in a non-driven state, and the vehicle performs a retreating operation in BEV (Battery Electric Vehicle) mode using the second electric motor. Since the travelable distance during this retreating operation depends on the amount of electric power stored in the battery, if the dragging torque of the first electric motor due to the short-circuit failure of the inverter is large, the travelable distance will be shortened.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a control device for a vehicle that can suppress a decrease in the travelable distance when a short-circuit failure occurs in the inverter that drives the electric motor.

Means for Solving the Problems

[0006] The gist of the present invention is a control device for a vehicle including an engine, a power split mechanism that divides the power of the engine into a first electric motor and a rotating member connected to a pair of drive wheels, and a second electric motor connected to the rotating member so as to be able to transmit power, wherein: (a) when an inverter that drives the first electric motor is in an abnormal state, specific control is executed to identify a short-circuited phase in the inverter in the operating state of the engine; and (b) when the short-circuited phase is identified by the specific control, three-phase on control of the inverter is executed, and the rotational speed of the engine is controlled so that the rotational speed of the first electric motor falls within a predetermined rotational speed range.

Advantages of the Invention

[0007] According to the present invention, (a) when an inverter that drives the first electric motor is in an abnormal state, specific control is executed to identify a short-circuited phase in the inverter in the operating state of the engine; and (b) when the short-circuited phase is identified by the specific control, three-phase on control of the inverter is executed, and the rotational speed of the engine is controlled so that the rotational speed of the first electric motor falls within a predetermined rotational speed range. When three-phase on control is executed and the rotational speed of the first electric motor is within a predetermined rotational speed range, the pulling torque of the first electric motor is reduced as compared with the case where it is not. Thereby, a decrease in the efficiency of the inverter is suppressed, and a decrease in the travelable distance of the vehicle is suppressed.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiment for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the embodiments, the drawings are appropriately simplified or deformed, and the dimensional ratios, shapes, etc. of each part are not necessarily drawn accurately.

Embodiment

[0010] FIG. 1 is a schematic configuration diagram of a vehicle 10 equipped with an electronic control device 90 according to an embodiment of the present invention, and is also a functional block diagram showing the main part of the control functions for various controls in the vehicle 10. FIG. 2 is a collinear diagram that can represent the relative relationship of the rotational speeds of each rotating element in the power split mechanism 22 by a straight line.

[0011] The vehicle 10 is a hybrid vehicle including an engine 12 and a second electric motor MG2 that function as a driving power source for traveling. The vehicle 10 includes, in the power transmission path PT between the engine 12 and a pair of drive wheels 14, in order from the engine 12 side, an engine connecting shaft 20, a power split mechanism 22, an output shaft 24, a differential 26, and a pair of axles 28, which are well-known configurations. The sun gear S, carrier CA, and ring gear R of the planetary gear device constituting the power split mechanism 22 are respectively connected to the first electric motor MG1, the engine 12, and the output shaft 24. The power split mechanism 22 mechanically splits the power of the engine 12 between the first electric motor MG1 and the output shaft 24. In this specification, unless otherwise distinguished, torque, driving force, power, and force (power) are the same. The second electric motor MG2 is connected to the output shaft 24 so as to be able to transmit power. The first electric motor MG1 and the second electric motor MG2 are, for example, so-called motor generators and are three-phase synchronous motors. Further, the vehicle 10 includes a battery 30, an inverter 40, and an electronic control device 90. The output shaft 24 corresponds to the "rotating member" in the present invention.

[0012] The inverter 40 includes a first inverter 50 and a second inverter 60 that respectively convert direct current to alternating current and alternating current to direct current. The first inverter 50 performs power conversion between the first electric motor MG1 and the battery 30 and corresponds to the "inverter" in the present invention. The second inverter 60 performs power conversion between the second electric motor MG2 and the battery 30. The first electric motor MG1 generates electricity by the power input from the engine 12. The generated electric power is either charged to the battery 30 or used for the rotational drive of the second electric motor MG2.

[0013] As shown in FIG. 1, the first inverter 50 has a well-known configuration including switching elements 56a to 56f and diodes 58a to 58f. The upper arm 52 in the first inverter 50 is a circuit that supplies current from the positive electrode of the battery 30 to the first electric motor MG1 as a load, and is composed of the switching elements 56a, 56c, 56e and the diodes 58a, 58c, 58e. The lower arm 54 in the first inverter 50 is a circuit that draws current from the first electric motor MG1 as a load to the negative electrode of the battery 30, and is composed of the switching elements 56b, 56d, 56f and the diodes 58b, 58d, 58f. The second inverter 60 has the same configuration as the first inverter 50. The second inverter 60 has a well-known configuration including switching elements 66a to 66f and diodes 68a to 68f.

[0014] In the vehicle 10, for example, a BEV running mode using only the second electric motor MG2 as a power source and an engine running mode using at least the engine 12 as a power source can be selected.

[0015] The electronic control device 90 is configured to include, for example, a so-called microcomputer, and executes various controls of the vehicle 10. Note that the electronic control device 90 corresponds to the "control device" in the present invention. Various signals (for example, the engine rotation speed Ne [rpm] which is the rotation speed of the engine 12, the MG1 rotation speed Nmg1 [rpm] which is the rotation speed of the first electric motor MG1, the MG2 rotation speed Nmg2 [rpm] which is the rotation speed of the second electric motor MG2, the output shaft rotation speed Nout [rpm] which is the rotation speed of the output shaft 24 corresponding to the vehicle speed V [km / h], the accelerator opening θacc [%], the first inverter current Iinv1 [A] flowing through each phase of the first inverter 50, and the second inverter current Iinv2 [A] flowing through each phase of the second inverter 60, etc.) based on the detection values by various sensors (for example, the engine rotation speed sensor 70, the MG1 rotation speed sensor 72, the MG2 rotation speed sensor 74, the output shaft rotation speed sensor 76, the accelerator opening sensor 78, the current sensor 80, etc.) are respectively input into the electronic control device 90. Various command signals (for example, the engine control signal Se, the first inverter control signal Sinv1 for rotationally controlling the first electric motor MG1 via the first inverter 50, the second inverter control signal Sinv2 for rotationally controlling the second electric motor MG2 via the second inverter 60, etc.) are respectively output from the electronic control device 90 to each device (for example, the engine 12, the first inverter 50, the second inverter 60, etc.).

[0016] By the way, a single-phase short-circuit fault may occur in the first inverter 50 where any one of the switching elements 56a to 56f is constantly in the on state. Hereinafter, the control for suppressing the decrease in the travelable distance of the vehicle 10 when a single-phase short-circuit fault occurs will be described.

[0017] The electronic control device 90 functionally includes a travel control unit 92, an abnormality determination unit 94, a condition determination unit 96, and a short-circuit phase identification determination unit 98, and the travel control unit 92 functionally includes an engine control unit 92a and an MG control unit 92b.

[0018] The engine control unit 92a controls the operating state (= operating state or stopped state) of the engine 12. The MG control unit 92b controls the operating states (= driving state or non-driving state) of the first electric motor MG1 and the second electric motor MG2 via the inverter 40. The travel control unit 92 controls the travel state of the vehicle 10. The travel control unit 92 controls the operating states of the engine 12, the first electric motor MG1, and the second electric motor MG2 so that, for example, the drive torque requested by the driver is transmitted to the pair of drive wheels 14.

[0019] The abnormality detection unit determines whether or not the first inverter 50 is in an abnormal state. For example, when a single-phase short-circuit fault occurs, an overcurrent flows through the first inverter 50. Therefore, when the current flowing from the positive electrode line to the negative electrode line of the power line pair in the first inverter 50 becomes equal to or greater than a current value defined in advance as an overcurrent, it is determined that the state is abnormal.

[0020] When it is determined that the first inverter 50 is in an abnormal state, the travel control unit 92 controls the engine 12 to be in an operating state, controls the second motor MG2 to be in a driving state, and controls the first inverter 50 to be in a non-driving state, that is, controls the first motor MG1 to be in a non-driving state. In the non-driving state of the first inverter 50, all the switching elements 56a to 56f are in an off state. For example, when the engine 12 is in a stopped state, the engine 12 is started. As shown by the white arrow in Fig. 2(a), when the rising control of the MG2 rotational speed Nmg2 is executed and the engine rotational speed Ne exceeds the ignition rotational speed value Ne_ign, the engine 12 is ignited and started. Thereafter, the condition determination unit 96 determines whether or not the necessary conditions for specifying the short-circuited phase of the first inverter 50 are satisfied. Specifically, as shown in Fig. 2(b), when the absolute value of the MG1 rotational speed Nmg1 is equal to or higher than the required rotational speed value Nmg1_nd, it is determined that the necessary conditions are satisfied, and when it is not, it is determined that the necessary conditions are not satisfied. For example, in the case of a relatively low vehicle speed as shown by the solid line, it is likely to be determined that the necessary conditions are satisfied, and in the case of a relatively high vehicle speed as shown by the broken line, it is likely to be determined that the necessary conditions are not satisfied. The required rotational speed value Nmg1_nd is a lower limit rotational speed value in the vicinity of a predetermined zero value that is required for specifying the short-circuited phase and is determined experimentally or by design in advance.

[0021] When the first inverter 50 is in a non-driving state, an induced current (= first inverter current Iinv1) based on a back electromotive force corresponding to the MG1 rotational speed Nmg1 flows in each phase of the first inverter 50. When the MG1 rotational speed Nmg1 is less than the required rotational speed value Nmg1_nd, the back electromotive force is low, so the induced current hardly appears and it becomes difficult to specify the short-circuited phase. In the case of the solid line in Fig. 2(b), when a single-phase short-circuit fault has occurred, if the single-phase short-circuit dragging torque Tt1 [Nm] described later is large, due to the negative torque Tneg [Nm] that appears in the ring gear R based on the engine torque Te, which is the output torque of the engine 12, and the single-phase short-circuit dragging torque Tt1, the effective torque Teff [Nm] transmitted from the output shaft 24 to the pair of drive wheels 14 decreases compared to the MG2 output torque Tmg2 [Nm]. The MG2 output torque Tmg2 is the output torque of the second motor MG2.

[0022] When it is determined that the necessary condition is satisfied, the short-circuit phase identification unit 98 identifies the short-circuit phase in the first inverter 50. The identification of the short-circuit phase is performed based on whether the first inverter current Iinv1 of each phase (= U phase, V phase, and W phase) in the upper arm 52 and the lower arm 54 is equal to or greater than the current determination value Iinv_jdg. The current determination value Iinv_jdg is a predetermined determination value determined in advance experimentally or by design to identify a short-circuit phase.

[0023] When a short - circuited phase is identified, the MG control unit 92b executes three - phase on - control, in which all the switching elements of the upper arm 52 and the lower arm 54 that include the short - circuited phase are turned on and all the switching elements of the other side are turned off. This three - phase on - control is a well - known control technique. During the execution of the three - phase on - control, a drag torque (hereinafter referred to as "three - phase on drag torque Tt3 [Nm]") in the direction in which the rotation of the first motor MG1 is stopped acts on the first motor MG1. Hereinafter, when a single - phase short - circuit fault occurs, the drag torque of the first motor MG1 during the execution of the normal three - phase drive control is referred to as "single - phase short - circuit drag torque Tt1". Also, the engine control unit 92a controls the engine rotation speed Ne so that it is within the control range Ne_ctrl in order to make the MG1 rotation speed Nmg1 within the control range Nmg1_ctrl. The control range Nmg1_ctrl is an experimentally or designed - in advance rotation speed range in which the three - phase on drag torque Tt3 is lower than the single - phase short - circuit drag torque Tt1, and corresponds to the "predetermined rotation speed range" in the present invention. The control range Nmg1_ctrl is a rotation speed range higher than the lower - limit rotation speed value Nmg1_jdg1. Preferably, the control range Nmg1_ctrl is a rotation speed range that is higher than the lower - limit rotation speed value Nmg1_jdg1 and lower than the upper - limit rotation speed value Nmg1_jdg2. Details of the lower - limit rotation speed value Nmg1_jdg1 and the upper - limit rotation speed value Nmg1_jdg2 will be described later. The MG2 rotation speed Nmg2 is determined according to the vehicle speed V requested by the driver. Thereby, based on the MG2 rotation speed Nmg2 and the control range Nmg1_ctrl, the control range Ne_ctrl is determined. As shown in FIG. 2(c), when the three - phase on drag torque Tt3 is small, for example, since the negative torque Tneg appearing on the ring gear R decreases based on the cancellation of the engine torque Te and the three - phase on drag torque Tt3, the effective torque Teff becomes larger compared to the case of the solid line in FIG. 2(b) described above. For example, when the negative torque Tneg appearing on the ring gear R becomes zero, the effective torque Teff becomes equal to the MG2 output torque Tmg2.

[0024] FIG. 3 is a diagram for explaining the relationship between the single-phase short-circuit starting torque Tt1 and the three-phase on starting torque Tt3, and the MG1 rotational speed Nmg1. As shown in FIG. 3, it is well known that as the MG1 rotational speed Nmg1 increases, the three-phase on starting torque Tt3 becomes lower than the single-phase short-circuit starting torque Tt1. The lower limit rotational speed value Nmg1_jdg1 is a predetermined rotational speed value experimentally or design-wise determined such that the three-phase on starting torque Tt3 becomes lower compared to the single-phase short-circuit starting torque Tt1. In this way, with the three-phase on control of the first motor MG1 and the operating state controlled such that the MG1 rotational speed Nmg1 is within the control range Nmg1_ctrl, the starting torque of the first motor MG1 is reduced for evacuation running. The upper limit rotational speed value Nmg1_jdg2 is a predetermined rotational speed value experimentally or design-wise determined such that the amount of heat generated due to the first inverter current Iinv1 corresponding to the MG1 rotational speed Nmg1 is within a predetermined allowable range.

[0025] Return to FIG. 1. When the short-circuited phase is not identified, the travel control unit 92 causes evacuation running to be performed in the BEV travel mode using only the second motor MG2 as the power source. For example, when a control abnormality occurs where the switching elements 56a and 56b are simultaneously in the on state, etc., the short-circuited phase due to the single-phase short-circuit fault is not identified.

[0026] FIG. 4 is an example of a flowchart for explaining the main part of the control operation of the electronic control device 90. The flowchart of FIG. 4 starts when the first inverter 50 is in an abnormal state.

[0027] First, in S10, it is determined whether the engine 12 is in a stopped state. If the determination in S10 is YES, in S20, the first electric motor MG1 is set to a non-driven state and a BEV driving mode is set where only the second electric motor MG2 is the power source. In S30, it is determined whether the engine 12 can be started. If the determination in S30 is NO, an increase control to increase the MG2 rotational speed Nmg2 is executed, and S30 is executed again. If the determination in S30 is YES, the engine 12 is started and a driving state is set with the engine 12 and the second electric motor MG2 as the power sources. If the determination in S10 is NO, in S60, the first electric motor MG1 is set to a non-driven state, and in S70, a driving state is set with the engine 12 and the second electric motor MG2 as the power sources. After the execution of S50 and after the execution of S70, in both cases, in S80, it is determined whether the absolute value of the MG1 rotational speed Nmg1 is equal to or greater than the required rotational speed value Nmg1_nd. If the determination in S80 is YES, in S90, the identification of the short-circuited phase in the first inverter 50 is performed. If the determination in S80 is NO, S80 is executed again. If the determination in S90 is YES, in S100, three-phase on control is executed, and in S110, the engine rotational speed Ne is controlled so that the MG1 rotational speed Nmg1 is within the control range Nmg1_ctrl, and a retreat driving is performed. If the determination in S90 is NO, in S120, a retreat driving is performed with the engine 12 and the second electric motor MG2 as the power sources and the first electric motor MG1 in a non-driven state. After the execution of S110 and after the execution of S120, in both cases, it ends.

[0028] According to this embodiment, (a) when the first inverter 50 is in an abnormal state, specific control for identifying a short-circuited phase in the first inverter 50 is executed in the operating state of the engine 12, and (b) when the short-circuited phase is identified by the specific control, three-phase on control is executed and the engine rotational speed Ne is controlled so that the MG1 rotational speed Nmg1 is within the control range Nmg1_ctrl. When the three-phase on control is executed and the MG1 rotational speed Nmg1 is within the control range Nmg1_ctrl, the drag torque of the first motor MG1 is reduced as compared with the case where it is not. Thereby, a decrease in the efficiency of the first inverter 50 is suppressed and a decrease in the travelable distance of the vehicle 10 is suppressed.

[0029] Note that the above are the embodiments of the present invention, and the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art without departing from the spirit thereof.

[0030] The determination that the first inverter 50 is in an abnormal state may be made, for example, when the actual temperature THinv1 [°C] of the first inverter 50 detected by a temperature sensor provided in the first inverter 50 is equal to or higher than a predetermined temperature determination value THinv1_jdg. The predetermined temperature determination value THinv1_jdg is a predetermined determination value determined in advance experimentally or by design, which has a possibility of heat generation due to a single-phase short-circuit fault.

Explanation of Reference Numerals

[0031] 10: Vehicle, 12: Engine, 14: Pair of drive wheels, 22: Power split mechanism, 24: Output shaft (rotating member), 50: First inverter (inverter), 90: Electronic control unit (control unit), MG1: First motor, MG2: Second motor, Ne: Engine rotational speed (rotational speed of the engine), Nmg1: MG1 rotational speed (rotational speed of the first motor), Nmg1_ctrl: Control range (predetermined rotational speed range)

Claims

【Claim 1】 A control device for a vehicle, comprising: an engine; a power split mechanism that splits the power of the engine and connects it to a first electric motor and a rotating member connected to a pair of drive wheels; and a second electric motor connected to the rotating member so as to be capable of power transmission, when an inverter that drives the first electric motor is in an abnormal state, executing specific control for specifying a short-circuited phase in the inverter in the operating state of the engine, when the short-circuited phase is specified by the specific control, performing three-phase on control of the inverter and controlling the rotational speed of the engine so that the rotational speed of the first electric motor falls within a predetermined rotational speed range A control device for a vehicle, characterized by the above.

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