Vehicle drive device

Abstract

To suppress an electrolytic corrosion of a bearing.SOLUTION: A vehicle drive device includes: a first case that holds a stator and a first bearing, and a second case that is attached to the first case and holds a second bearing. The vehicle drive device includes: an insulating gasket that electrically insulates the first case and the second case from each other; and a conductive material that electrically connects the first case and the second case to each other. A control system including a processor and a memory executes electrolytic corrosion suppression control for suppressing electrolytic corrosion of at least one of the first bearing and the second bearing when a current value or a voltage value of the conducting material exceeds respective threshold values.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a vehicle drive device. [Background technology]

[0002] Vehicles such as automobiles are equipped with power units equipped with electric motors (see Patent Documents 1 to 5). A stator of the electric motor is assembled inside the case of the power unit, as well as bearings that support various rotating shafts. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-57183 [Patent Document 2] Japanese Patent Publication No. 2020-14359 [Patent Document 3] Japanese Patent Application Laid-Open No. 2016-158437 [Patent Document 4] Japanese Patent Application Laid-Open No. 2017-112725 [Patent Document 5] Patent No. 6271452 Summary of the Invention [Problem to be solved by the invention]

[0004] However, electric motors generate axial voltage, which can cause electrolytic corrosion in the bearings inside the case. Because electrolytic corrosion can damage the raceway surfaces of the bearings, there is a need to suppress this electrolytic corrosion in the bearings. [Means for solving the problem]

[0005] According to the present disclosure, a vehicle drive device includes an electric motor with a stator, a first case that holds the stator and a first bearing, and a second case that is attached to the first case and holds a second bearing. The vehicle drive device includes an insulating gasket that is provided between the first case and the second case and electrically insulates the first case from the second case. The vehicle drive device includes an electrically conductive member that is attached to the first case and the second case and electrically connects the first case to the second case. The vehicle drive device includes a control system that includes a processor and a memory that are communicatively connected to each other. The control system executes electrolytic corrosion suppression control that suppresses electrolytic corrosion of at least one of the first bearing and the second bearing when a current value or a voltage value of the electrically conductive member exceeds a threshold value. [Effects of the Invention]

[0006] According to the present disclosure, electrolytic corrosion of bearings can be suppressed. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing an example of a vehicle equipped with a power unit. [Figure 2] FIG. 2 is a diagram showing a part of the internal structure of the power unit. [Figure 3] FIG. 3 is a diagram illustrating an example of a control system provided in a vehicle drive device. [Figure 4] FIG. 4 is a diagram showing an example of the basic structure of an electronic control unit. [Figure 5] FIG. 5 is a flowchart showing an example of the procedure for executing electrolytic corrosion suppression control 1. [Figure 6] FIG. 6 is a diagram showing an example of the occurrence of electrolytic corrosion. [Figure 7A] FIG. 7A is a diagram showing an example of the transition of the value of the current flowing through the connecting wire when electrolytic corrosion occurs. [Figure 7B] FIG. 7B is a diagram showing an example of the transition of the value of the current flowing through the connecting wire when electrolytic corrosion occurs. [Figure 7C]FIG. 7C is a diagram showing an example of the transition of the value of the current flowing through the connecting wire when electrolytic corrosion occurs. [Figure 7D] FIG. 7D is a diagram showing an example of the transition of the value of the current flowing through the connecting wire when electrolytic corrosion occurs. [Figure 8] FIG. 8 is a diagram illustrating an example of a control system provided in a vehicle drive device according to another embodiment of the present disclosure. [Figure 9] FIG. 9 is a flowchart showing an example of the procedure for executing electrolytic corrosion suppression control 2. [Figure 10] FIG. 10 is a diagram showing an example of the transition of the voltage value of the current-carrying wire. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the following description, identical or substantially identical configurations and elements will be designated by the same reference numerals and repeated description will be omitted.

[0009] First Embodiment <Power unit> FIG. 1 is a diagram showing an example of a vehicle 11 equipped with a power unit 10. The illustrated power unit 10 includes a vehicle drive device 12 according to one embodiment of the present disclosure. As shown in FIG. 1, the vehicle 11 has a power unit 10 including an engine 13 and motor generators MG1 and MG2. A rear wheel output shaft 14 of the power unit 10 is connected to rear wheels 17 via a propeller shaft 15 and a rear differential mechanism 16. The power unit 10 also includes a front differential mechanism 18, which is connected to front wheels 19.

[0010] FIG. 2 is a diagram showing a portion of the internal structure of the power unit 10. As shown in FIG. 2, the power unit 10 has a main output shaft 20 that passes through the center of the motor generator MG2 to output engine power and motor power to front and rear wheels 17, 19. The main output shaft 20 is connected to a front wheel output shaft 22 via a gear train 21 and to a rear wheel output shaft 14 via a transfer clutch 23. The main output shaft 20 is also connected to a power split mechanism 25 via a gear train 24. The power split mechanism 25 is connected to the motor generator MG1 and to the engine 13 via a gear train 26 and a damper mechanism 27. The main output shaft 20 is also connected to the motor generator MG2 via a planetary gear train 28. The front wheel output shaft 22 is connected to the front differential mechanism 18 described above.

[0011] The power unit 10 has a composite case 35 made up of four case parts 31, 32, 33, and 34. An insulating gasket 36 is provided between case part 31 and case part 32, thereby electrically insulating case part 31 from case part 32. An insulating gasket 37 is provided between case part 32 and case part 33, thereby electrically insulating case part 32 from case part 33. An insulating gasket 38 is provided between case part 33 and case part 34, thereby electrically insulating case part 33 from case part 34. In this way, the four case parts 31, 32, 33, and 34 made of a metal material such as an aluminum alloy are electrically insulated from one another by sandwiching the insulating gaskets 36, 37, and 38 between them.

[0012] Note that knock pins (not shown) used to position the case parts 31 to 34 and fastening bolts (not shown) used to connect the case parts 31 to 34 also have electrically insulated structures. In addition, the fastening portions of the composite case 35 to the vehicle body are also electrically insulated by using rubber bushings or the like.

[0013] Case part 31 houses damper mechanism 27, gear train 26, motor generator MG1, front differential mechanism 18, etc., and holds a plurality of bearings 41, 42, 43, 44, and 45 that support the rotating shafts, etc. Case part 32 houses power split mechanism 25, etc., and holds a plurality of bearings 46 and 47 that support the rotating shafts, etc. Case part 33 houses gear trains 21 and 24, etc., and holds a plurality of bearings 48, 49, and 50 that support the rotating shafts, etc. Case part 34 houses planetary gear train 28, motor generator MG2, transfer clutch 23, etc., and holds a plurality of bearings 51, 52, 53, 54, 55, 56, and 57 that support the rotating shafts, etc.

[0014] Motor generator MG1 has a stator 62 consisting of a stator core 60 and a stator coil 61, and a rotor 65 consisting of a rotor core 63 and a permanent magnet 64. Stator 62 of motor generator MG1 is attached to case component 32 using fastening bolts (not shown). Motor generator MG2 has a stator 72 consisting of a stator core 70 and a stator coil 71, and a rotor 75 consisting of a rotor core 73 and a permanent magnet 74. Stator 72 of motor generator MG2 is attached to case component 34 using fastening bolts (not shown).

[0015] An electric wire (electrically conductive material) 80 having four connecting wires 81 to 84 is attached to the composite case 35 of the power unit 10. The connecting wire 81 is attached to the case part 31, and the connecting wire 82 is attached to the case part 32. The connecting wire 83 is attached to the case part 33, and the connecting wire 84 is attached to the case part 34. In this manner, the case parts 31 to 34 are electrically connected to each other via the electric wire 80. A current sensor 85 is attached to the connecting wire 81, and a current sensor 86 is attached to the connecting wire 82. A current sensor 87 is attached to the connecting wire 83, and a current sensor 88 is attached to the connecting wire 84.

[0016] In this specification, the stator 62 of the motor generator (electric motor) MG1 is attached to the case component 32, and therefore the case component 32 corresponds to the first case. Furthermore, the case component 31 is attached to the case component 32, and this case component 31 corresponds to the second case. Furthermore, the bearings 46 and 47 held in the case component (first case) 32 correspond to the first bearing, and the bearings 41 to 45 held in the case component (second case) 31 correspond to the second bearing. In the illustrated example, the stator 62 is attached to the case component 32, but the stator 62 may be attached to both the case components 31 and 32. Furthermore, the case component 33 is attached to the case component (first case) 32, and this case component 33 can also be considered to correspond to the second case. In this case, the bearings 48 to 50 held in the case component (second case) 33 correspond to the second bearing.

[0017] <Control System> Fig. 3 is a diagram showing an example of a control system 90 provided in the vehicle drive device 12. As shown in Fig. 3, the vehicle drive device 12 has a control system 90 made up of a plurality of electronic control units. The vehicle drive device 12 has, as electronic control units that make up the control system 90, an electrolytic corrosion monitoring unit 91, a motor control unit 92, and a hydraulic control unit 93. These control units 91 to 93 are connected to each other via an in-vehicle network 94 so that they can communicate with each other.

[0018] The electrolytic corrosion monitoring unit 91 has the function of determining the occurrence of electrolytic corrosion in the bearings 41 to 57 incorporated within the composite case 35. This electrolytic corrosion monitoring unit 91 is connected to four current sensors 85 to 88 attached to the current-carrying wire 80. As will be described later, the electrolytic corrosion monitoring unit 91 determines the occurrence of electrolytic corrosion in the bearings 41 to 57 housed within the composite case 35 based on the current values ​​i1 to i4 of the connecting wires 81 to 84. If the electrolytic corrosion monitoring unit 91 determines that electrolytic corrosion has occurred in any of the bearings 41 to 57, it outputs a control signal to the motor control unit 92 and the hydraulic control unit 93, and controls the motor generator MG1 and the hydraulic system 100 to suppress the occurrence of electrolytic corrosion.

[0019] An inverter 95, which is a power conversion device, is connected to the stator 62 of motor generator MG1, and an inverter 96, which is a power conversion device, is connected to the stator 72 of motor generator MG2. A motor control unit 92 is connected to the inverters 95, 96 in order to control these inverters 95, 96. The motor control unit 92 controls the state of conduction of the stator coil 61 via the inverter 95, thereby controlling the torque and rotation speed of the motor generator MG1. The motor control unit 92 also controls the state of conduction of the stator coil 71 via the inverter 96, thereby controlling the torque and rotation speed of the motor generator MG2.

[0020] The power unit 10 includes a hydraulic system 100 including oil pumps 102, 103, a hydraulic circuit unit 105, and the like, for lubricating bearings 41-57 and the like within the composite case 35 and controlling hydraulic devices 101 such as the transfer clutch 23. The hydraulic system 100 includes an engine-driven mechanical oil pump 102 and a motor-driven electric oil pump 103. The hydraulic system 100 also includes a hydraulic circuit unit 105 connected to a discharge oil passage 104 of the oil pumps 102, 103, a line pressure control valve 107 connected to a branch oil passage 106 branching from the discharge oil passage 104, and a lubrication circuit unit 108 connected to a discharge port of the line pressure control valve 107. The hydraulic circuit unit 105, which includes an electromagnetic valve and oil passages, controls the flow rate and pressure of hydraulic oil supplied to the hydraulic devices 101. The lubrication circuit unit 108, which includes an oil passage, also functions to supply lubricating hydraulic oil to the bearings 41-57 and the like. To control the hydraulic system 100, a hydraulic control unit 93 is connected to the electric oil pump 103, the line pressure control valve 107, the hydraulic circuit section 105, and the like.

[0021] Fig. 4 is a diagram showing an example of the basic structure of the electronic control units 91, 92, and 93. As shown in Fig. 4, the electronic control units 91 to 93 each have a microcontroller 112 incorporating a processor 110 and a main memory (memory) 111. A predetermined program is stored in the main memory 111, and the program is executed by the processor 110. The processor 110 and the main memory 111 are connected to each other so that they can communicate with each other. Note that a plurality of processors 110 may be incorporated into the microcontroller 112, and a plurality of main memories 111 may be incorporated into the microcontroller 112.

[0022] The electronic control units 91 to 93 each include an input circuit 113, a drive circuit 114, a communication circuit 115, an external memory 116, and a power supply circuit 117. The input circuit 113 converts signals input from various sensors into signals that can be input to the microcontroller 112. The drive circuit 114 generates drive signals for devices such as the line pressure control valve 107 and inverters 95 and 96 based on signals output from the microcontroller 112. The communication circuit 115 converts signals output from the microcontroller 112 into communication signals directed to other electronic control units. The communication circuit 115 also converts communication signals received from other electronic control units into signals that can be input to the microcontroller 112. The power supply circuit 117 supplies a stable power supply voltage to the microcontroller 112, the input circuit 113, the drive circuit 114, the communication circuit 115, the external memory 116, and the like. The external memory 116, which may be a nonvolatile memory or the like, stores programs and various data.

[0023] <Electric corrosion suppression control 1> Next, an explanation will be given of electrolytic corrosion suppression control 1 for suppressing electrolytic corrosion of bearings 41 to 57. Fig. 5 is a flowchart showing an example of the execution procedure of electrolytic corrosion suppression control 1. Note that each step of electrolytic corrosion suppression control 1 shown in Fig. 5 is a step executed by a processor 110 constituting a control system 90. Furthermore, electrolytic corrosion suppression control 1 is executed by the control system 90 at predetermined intervals.

[0024] 5, the control system 90 proceeds to step S10, extracts a maximum current value imax from each of the current values ​​i1, i2, i3, and i4, and determines whether the absolute value of this maximum current value imax exceeds a current threshold (threshold value) Xi. If the control system 90 determines in step S10 that the absolute value of the maximum current value imax exceeds the current threshold value Xi, the control system 90 proceeds to step S11, where it executes a counting process for the timer count value. Next, the control system 90 proceeds to step S12, where it determines whether the timer count value exceeds a predetermined determination time Tx.

[0025] If the control system 90 determines in step S12 that the timer count value is equal to or less than the determination time Tx, it proceeds to step S10 again and determines whether or not the absolute value of the maximum current value imax exceeds the current threshold value Xi. On the other hand, if the control system 90 determines in step S12 that the timer count value exceeds the determination time Tx, it proceeds to step S13 and executes oil amount increase control to increase the amount of lubricating oil supplied to the bearings 41 to 57. Note that when executing the oil amount increase control, the control system 90 increases the amount of oil discharged from the electric oil pump 103 and increases the amount of hydraulic oil flowing from the line pressure control valve 107 to the lubrication circuit unit 108, thereby increasing the amount of lubricating oil supplied to the bearings 41 to 57 from the most recent amount of lubricating oil.

[0026] In this way, when the maximum current value imax exceeds the current threshold value Xi over the determination time Tx, the control system 90 executes oil amount increase control to increase the amount of lubricating oil supplied to the bearings 41 to 57. This makes it possible to thicken the lubricating oil film formed on the bearings 41 to 57, making it less likely for electrolytic corrosion to occur in the bearings 41 to 57, that is, to increase the electrolytic corrosion withstand voltage of the bearings 41 to 57, thereby suppressing electrolytic corrosion occurring in the bearings 41 to 57.

[0027] Here, Fig. 6 is a diagram showing an example of the occurrence of electrolytic corrosion. Also, Figs. 7A, 7B, 7C, and 7D are diagrams showing an example of the transition of the current values ​​flowing through connecting wires 81 to 84 when electrolytic corrosion occurs. Fig. 7A shows the current value i1 of connecting wire 81, Fig. 7B shows the current value i2 of connecting wire 82, Fig. 7C shows the current value i3 of connecting wire 83, and Fig. 7D shows the current value i4 of connecting wire 84.

[0028] 6, bearing 45 held in case part 31 has an outer ring 45o connected to case part 31, an inner ring 45i connected to rotor 65, and rolling elements 45r provided between the outer ring 45o and the inner ring 45i. Similarly, bearing 48 held in case part 33 has an outer ring 48o connected to case part 33, an inner ring 48i connected to rotor 65 via power split mechanism 25, and rolling elements 48r provided between the outer ring 48o and the inner ring 48i. Furthermore, outer ring 45o of bearing 45 is connected to stator 62 via case part 31, conductive wire 80, and case part 32, and outer ring 48o of bearing 48 is connected to stator 62 via case part 33, conductive wire 80, and case part 32.

[0029] That is, the outer rings 45o, 48o of the bearings 45, 48 are connected to the stator 62 of the motor generator MG1, and the inner rings 45i, 48i of the bearings 45, 48 are connected to the rotor 65 of the motor generator MG1. Therefore, as shown in the enlarged portion of FIG. 6, a shaft voltage Va is applied to the outer rings 45o, 48o and the inner rings 45i, 48i of the bearings 45, 48. If the shaft voltage Va exceeds the electrolytic corrosion withstand voltage of the bearings 45, 48, a current flows along the current path C1 indicated by the dashed dotted line. This current spark may cause electrolytic corrosion in the outer rings 45o, 48o and the inner rings 45i, 48i, etc. The electrolytic corrosion withstand voltage corresponds to the dielectric breakdown voltage of the lubricating oil film F formed in the bearings 45, 48.

[0030] Thus, when electrolytic corrosion occurs in the bearings 45, 48, a current flows between the case part 31 and the case part 33. In this case, as indicated by symbols α1, α2, and β1 in FIGS. 7A to 7D , a situation is detected in which the maximum current value imax exceeds the current threshold Xi for the determination time Tx, with respect to the current value i1 flowing through the case part 31 and the current value i3 flowing through the case part 33. As described above, when the maximum current value imax exceeds the current threshold Xi for the determination time Tx, the control system 90 executes oil amount increase control to increase the amount of lubricating oil supplied to the bearings 41 to 57, thereby thickening the lubricating oil film F formed in the bearings 45, 48. This increases the electrolytic corrosion withstand voltage of the bearings 45, 48 and suppresses electrolytic corrosion occurring in the bearings 45, 48.

[0031] 5, after the control system 90 executes the oil amount increase control in step S13, the control system 90 proceeds to step S14 and executes the process of resetting the timer count value. Next, the control system 90 proceeds to step S15 and extracts the maximum current value imax from each of the current values ​​i1, i2, i3, and i4, and determines whether the absolute value of this maximum current value imax exceeds the current threshold value Xi. If the control system 90 determines in step S15 that the absolute value of the maximum current value imax exceeds the current threshold value Xi, the control system 90 proceeds to step S16 and executes the process of counting the timer count value. Next, the control system 90 proceeds to step S17 and determines whether the timer count value exceeds a predetermined determination time Tx.

[0032] If control system 90 determines in step S17 that the timer count value is equal to or less than the determination time Tx, it proceeds to step S15 again to determine whether the absolute value of maximum current value imax exceeds current threshold value Xi. On the other hand, if control system 90 determines in step S17 that the timer count value exceeds the determination time Tx, it proceeds to step S18 to execute output reduction control to reduce the motor output, i.e., motor power, of motor generator MG1. Note that when executing the output reduction control, control system 90 reduces the motor output of motor generator MG1 below the most recent motor output by reducing either or both of the motor torque and motor rotation speed of motor generator MG1.

[0033] In this way, when the maximum current value imax exceeds the current threshold Xi over the determination time Tx, the control system 90 executes output reduction control to reduce the motor output of the motor generator MG1. This actively reduces the shaft voltage of the motor generator MG1, thereby suppressing electrolytic corrosion occurring in the bearings 41-57. When the motor generator MG1 is controlled in a power generation state, the motor power is reduced by reducing the power generation torque and motor rotation speed of the motor generator MG1. When the motor generator MG1 is controlled in a power generation state, the motor power is reduced by reducing the power generation torque and motor rotation speed of the motor generator MG1.

[0034] As explained above, system 90 executes oil amount increase control when maximum current value imax exceeds current threshold Xi, and then executes output reduction control when maximum current value imax exceeds current threshold Xi. This increases the amount of lubricating oil to increase the electrolytic corrosion withstand voltage of bearings 41-57, and then reduces the shaft voltage of motor generator MG1, thereby suppressing electrolytic corrosion occurring in bearings 41-57. Furthermore, if there is a risk of electrolytic corrosion in bearings 41-57, oil amount increase control is executed before output reduction control, so electrolytic corrosion suppression control can be started without causing discomfort to the driver.

[0035] In the above description, the control system 90 executes oil amount increase control when the maximum current value imax exceeds the current threshold Xi, and then executes output reduction control when the maximum current value imax exceeds the current threshold Xi, but this is not limited to this. In other words, both oil amount increase control and output reduction control are executed as electrolytic corrosion suppression control, but this is not limited to this. Only oil amount increase control may be executed as electrolytic corrosion suppression control, or only output reduction control may be executed as electrolytic corrosion suppression control. Note that if the absolute value of the maximum current value imax falls below the current threshold Xi due to execution of oil amount increase control or output reduction control, the oil amount increase control or output reduction control is stopped.

[0036] Furthermore, in the illustrated power unit 10, the shaft voltage of motor generator MG1 appears higher than the shaft voltage of motor generator MG2, and therefore the motor output of motor generator MG1 is reduced in the output reduction control, but this is not limited to this. For example, if electrolytic corrosion is occurring due to the shaft voltage of motor generator MG2, the control system 90 executes output reduction control to reduce the motor output of motor generator MG2. Note that in the illustrated example, current sensors 85-88 are attached to all of the connecting wires 81-84, but this is not limited to this, and a current sensor may be attached to at least one of the connecting wires 81-84. Furthermore, a configuration may be such that the current value of the current-carrying wire 80 is detected by the electrolytic corrosion monitoring unit 91, without using current sensors 85-88 separate from the electrolytic corrosion monitoring unit 91.

[0037] Second Embodiment <Control System> In the above description, oil amount increase control and output reduction control are performed based on the current value of the current-carrying wire 80, but this is not limited thereto, and oil amount increase control and output reduction control may also be performed based on the voltage value of the current-carrying wire 80. Fig. 8 is a diagram showing an example of a control system 121 provided in a vehicle drive device 120 according to another embodiment of the present disclosure. Note that in Fig. 8, components similar to those shown in Fig. 3 are designated by the same reference numerals, and descriptions thereof will be omitted.

[0038] As shown in FIG. 8, the vehicle drive system 120 includes a control system 121 including an electrolytic corrosion monitoring unit 122, a motor control unit 92, and a hydraulic control unit 93. The electrolytic corrosion monitoring unit 122 has a function of determining the occurrence of electrolytic corrosion in the bearings 41 to 57 installed in the composite case 35. The electrolytic corrosion monitoring unit 122 is connected to the current-carrying wire 80 via a signal wire 123. The electrolytic corrosion monitoring unit 122 determines the occurrence of electrolytic corrosion in the bearings 41 to 57 housed in the composite case 35 based on a voltage value V1 of the current-carrying wire 80. If the electrolytic corrosion monitoring unit 122 determines that electrolytic corrosion has occurred in any of the bearings 41 to 57, it outputs a control signal to the motor control unit 92 and the hydraulic control unit 93, and controls the motor generator MG1 and the hydraulic system 100 to suppress the occurrence of electrolytic corrosion. The voltage value V1 of the current-carrying wire 80 is the potential difference between the signal wire 123 and the vehicle body 124.

[0039] <Electric corrosion suppression control 2> The electrolytic corrosion suppression control 2 for suppressing electrolytic corrosion of the bearings 41 to 57 will now be described. Fig. 9 is a flowchart showing an example of the execution procedure of the electrolytic corrosion suppression control 2. Note that each step of the electrolytic corrosion suppression control 2 shown in Fig. 9 is executed by the processor 110 constituting the control system 121. In other words, the electrolytic corrosion monitoring unit 122 also has a structure similar to that of the electronic control unit shown in Fig. 4. Furthermore, the electrolytic corrosion suppression control 2 is executed by the control system 121 at predetermined intervals.

[0040] 9, the control system 121 proceeds to step S20, extracts a maximum voltage value Vmax from the voltage value V1 of the current-carrying wire 80, and determines whether the absolute value of this maximum voltage value Vmax exceeds a voltage threshold (threshold, first threshold) Xv1. If the control system 121 determines in step S20 that the absolute value of the maximum voltage value Vmax exceeds the voltage threshold Xv1, the control system 121 proceeds to step S21, and executes a count process of the timer count value. Next, the control system 121 proceeds to step S22, and determines whether the timer count value exceeds a predetermined determination time Tx.

[0041] If the control system 121 determines in step S22 that the timer count value is equal to or less than the determination time Tx, the process proceeds to step S20 again, where it determines whether or not the absolute value of the maximum voltage value Vmax exceeds the voltage threshold value Xv1. On the other hand, if the control system 121 determines in step S22 that the timer count value exceeds the determination time Tx, the process proceeds to step S23, where it executes oil amount increase control to increase the amount of lubricating oil supplied to the bearings 41 to 57. Note that when executing the oil amount increase control, the control system 121 increases the amount of oil discharged from the electric oil pump 103 and increases the amount of hydraulic oil flowing from the line pressure control valve 107 to the lubrication circuit unit 108, thereby increasing the amount of lubricating oil supplied to the bearings 41 to 57 from the most recent amount of lubricating oil.

[0042] In this way, when the maximum voltage value Vmax exceeds the voltage threshold Xv1 over the determination time Tx, the control system 121 executes oil amount increase control to increase the amount of lubricant supplied to the bearings 41 to 57. In other words, a situation in which the maximum voltage value Vmax exceeds the voltage threshold Xv1 means that the shaft voltage of the motor generator MG1 is increasing, and electrolytic corrosion may occur in the bearings 41 to 57. For this reason, the control system 121 executes oil amount increase control to thicken the lubricant film formed on the bearings 41 to 57. This makes it less likely that electrolytic corrosion will occur in the bearings 41 to 57, that is, it increases the electrolytic corrosion withstand voltage of the bearings 41 to 57, thereby suppressing electrolytic corrosion occurring in the bearings 41 to 57.

[0043] Furthermore, after executing oil amount increase control in step S23, the control system 121 proceeds to step S24 and executes a process of resetting the timer count value. Next, the control system 121 proceeds to step S25 and extracts a maximum voltage value Vmax from the voltage value V1 of the current-carrying wire 80, and determines whether the absolute value of this maximum voltage value Vmax exceeds a voltage threshold value (second threshold value) Xv2 that is greater than the voltage threshold value Xv1. If the control system 121 determines in step S25 that the absolute value of the maximum voltage value Vmax exceeds the voltage threshold value Xv2, the control system 121 proceeds to step S26 and executes a process of counting the timer count value. Next, the control system 121 proceeds to step S27 and determines whether the timer count value exceeds a predetermined determination time Tx.

[0044] If control system 121 determines in step S27 that the timer count value is equal to or less than the determination time Tx, it proceeds to step S25 again to determine whether the absolute value of maximum voltage value Vmax exceeds voltage threshold value Xv2. On the other hand, if control system 121 determines in step S27 that the timer count value exceeds the determination time Tx, it proceeds to step S28 to execute output reduction control to reduce the motor output, i.e., motor power, of motor generator MG1. Note that when executing the output reduction control, control system 121 reduces the motor torque and / or motor rotation speed of motor generator MG1 to reduce the motor output of motor generator MG1 below the most recent motor output.

[0045] In this way, when the maximum voltage value Vmax exceeds the voltage threshold value Xv2 over the determination time Tx, the control system 121 executes output reduction control to reduce the motor output of the motor generator MG1. This actively reduces the shaft voltage of the motor generator MG1, thereby suppressing electrolytic corrosion that occurs in the bearings 41 to 57. When the motor generator MG1 is controlled in a power generation state, the motor power is reduced by reducing the power generation torque and motor rotation speed of the motor generator MG1. When the motor generator MG1 is controlled in a power generation state, the motor power is reduced by reducing the power generation torque and motor rotation speed of the motor generator MG1.

[0046] FIG. 10 is a diagram showing an example of the transition of the voltage value V1 of the current-carrying wire 80. As indicated by the symbol γ1 in FIG. 10, when a situation is detected in which the maximum voltage value Vmax of the current-carrying wire 80 exceeds a voltage threshold value Xv1 over a determination time Tx, the control system 121 executes oil amount increase control to increase the amount of lubricating oil supplied to the bearings 41-57. Furthermore, as indicated by the symbol γ2 in FIG. 10, when a situation is detected in which the maximum voltage value Vmax of the current-carrying wire 80 exceeds a voltage threshold value Xv2 over a determination time Tx, the control system 121 executes output reduction control to reduce the motor output of the motor-generator MG1. As a result, when the shaft voltage of the motor-generator MG1 increases, the amount of lubricating oil is increased to increase the electrolytic corrosion withstand voltage of the bearings 41-57 and the shaft voltage of the motor-generator MG1 is reduced, thereby suppressing electrolytic corrosion of the bearings 41-57.

[0047] As explained above, the control system 121 executes oil amount increase control when the maximum voltage value Vmax exceeds the voltage threshold Xv1, and then executes output reduction control when the maximum voltage value Vmax exceeds the voltage threshold Xv2. This increases the amount of lubricating oil to increase the electrolytic corrosion withstand voltage of the bearings 41-57, and then reduces the shaft voltage of the motor generator MG1, thereby suppressing electrolytic corrosion occurring in the bearings 41-57. Furthermore, if there is a risk of electrolytic corrosion in the bearings 41-57, the oil amount increase control is executed before the output reduction control, so that electrolytic corrosion suppression control can be started without causing any discomfort to the driver.

[0048] In the above description, the control system 121 executes oil amount increase control when the maximum voltage value Vmax exceeds the voltage threshold Xv1, and then executes output reduction control when the maximum voltage value Vmax exceeds the voltage threshold Xv2, but this is not limited to this. In other words, both oil amount increase control and output reduction control are executed as electrolytic corrosion suppression control, but this is not limited to this. Only oil amount increase control may be executed as electrolytic corrosion suppression control, or only output reduction control may be executed as electrolytic corrosion suppression control. Note that when the absolute value of the maximum voltage value Vmax falls below the voltage threshold Xv1, the oil amount increase control and output reduction control are stopped.

[0049] In the illustrated power unit 10, the shaft voltage of motor generator MG1 appears higher than the shaft voltage of motor generator MG2, and therefore the motor output of motor generator MG1 is reduced in the output reduction control. However, this is not a limitation. For example, if electrolytic corrosion is occurring due to the shaft voltage of motor generator MG2, the control system 121 executes output reduction control to reduce the motor output of motor generator MG2. In the illustrated example, the voltage value V1 of the current-carrying wire 80 is detected by the electrolytic corrosion monitoring unit 122. However, this is not a limitation. The voltage value V1 of the current-carrying wire 80 may be detected using a voltage sensor separate from the electrolytic corrosion monitoring unit 122. In the illustrated example, one signal wire 123 is connected to the current-carrying wire 80. However, this is not a limitation. A signal wire 123 may be connected to each of the connecting wires 81 to 84 of the current-carrying wire 80. In other words, the shaft voltage of motor generator MG1 may be determined based on the voltage value of each of the connecting wires 81 to 84.

[0050] <Modification> The present disclosure is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit and scope of the present disclosure. In the illustrated example, the technology of the present disclosure is applied to a power unit 10 having an engine 13 and motor generators MG1 and MG2 as power sources, but is not limited to this. For example, the technology of the present disclosure can also be applied to an electric axle consisting of a motor generator and a differential mechanism, that is, a power unit having only one motor generator as a power source.

[0051] In the above description, the composite case 35 is configured using three or more case parts 31-34, but this is not limited thereto and the composite case may be configured using two case parts. Also, in the above description, the control system 90 is configured using multiple electronic control units 91-93, but this is not limited thereto and the control system may be configured using a single electronic control unit. Also, the current-carrying wire 80 is attached to the case parts 31-34, but this is not limited thereto and bus bars serving as current-carrying members may be attached to the case parts 31-34.

[0052] In the above description, the amount of lubricating oil supplied to all bearings 41-57 is increased by the oil amount increase control. However, this is not limited to this. The amount of lubricating oil supplied to specific bearings may also be increased by the oil amount increase control. For example, the lubrication circuit unit 108 may be configured to adjust the amount of lubricating oil for each case component 31-34, and the amount of lubricating oil supplied to a case component having a bearing at risk of electrolytic corrosion may be increased. That is, if there is a risk of electrolytic corrosion for bearings 41-45 held in case component 31, the amount of lubricating oil supplied to bearings 41-45 alone may be increased, rather than the amount of lubricating oil supplied to all bearings 41-57. Furthermore, if there is a risk of electrolytic corrosion for bearings 46 and 47 held in case component 32, the amount of lubricating oil supplied to bearings 46 and 47 alone may be increased, rather than the amount of lubricating oil supplied to all bearings 41-57. [Explanation of symbols]

[0053] 12...vehicle drive device, 31...case part (second case), 32...case part (first case), 36-38...insulating gasket, 41-45...bearing (second bearing), 46, 47...bearing (first bearing), 62...stator, 80...current-carrying wire (current-carrying material), 90...control system, 110...processor, 111...main memory (memory), 120...vehicle drive device, 121...control system, MG1...motor generator (electric motor), i1-i4...current value, V1...voltage value, Xi...current threshold (threshold), Xv1...voltage threshold (threshold, first threshold), Xv2...voltage threshold (second threshold)

Claims

1. an electric motor having a stator; a first case that holds the stator and a first bearing; a second case attached to the first case and holding a second bearing; an insulating gasket provided between the first case and the second case to electrically insulate the first case from the second case; an electrically conductive member attached to the first case and the second case, electrically connecting the first case and the second case; a control system including a processor and a memory communicatively coupled to each other; and The control system includes: When the current value or the voltage value of the current-carrying material exceeds a threshold value, electrolytic corrosion suppression control is executed to suppress electrolytic corrosion of at least one of the first bearing and the second bearing. Vehicle drive unit.

2. 2. The vehicle drive system according to claim 1, The electrolytic corrosion suppression control is an output reduction control that reduces the output of the electric motor. Vehicle drive unit.

3. 2. The vehicle drive system according to claim 1, the electrolytic corrosion suppression control is oil amount increase control that increases an amount of lubricating oil supplied to at least one of the first bearing and the second bearing; Vehicle drive unit.

4. 2. The vehicle drive system according to claim 1, The control system includes: When the current value of the current-carrying material exceeds the threshold value, an oil amount increase control is executed to increase the amount of lubricating oil supplied to at least one of the first bearing and the second bearing; When the current value of the current-carrying material exceeds the threshold value under the condition that the oil amount increase control is being executed, an output reduction control is executed to reduce the output of the electric motor. Vehicle drive unit.

5. 2. The vehicle drive system according to claim 1, The control system includes: When the voltage value of the electrically conductive material exceeds a first threshold value, which is the threshold value, an oil amount increase control is executed to increase an amount of lubricating oil supplied to at least one of the first bearing and the second bearing; When the voltage value of the electrically conductive material exceeds a second threshold value that is greater than the first threshold value under the condition that the oil amount increase control is being executed, an output reduction control is executed to reduce the output of the electric motor. Vehicle drive unit.

Images