ELECTRIC VEHICLE

Abstract

Electric vehicle (10), with: an electric motor (MG1, MG2); a multi-speed transmission (30) which has a plurality of gear positions and is arranged in a power transmission path between a rotating shaft of the electric motor (MG1, MG2) and drive wheels (44) of the electric vehicle (10); a drive unit (52) designed to drive the electric motor (MG1, MG2); a converter (54) designed to regulate a voltage supplied to the drive unit (52); and an electronic control unit (60) designed to (i) controls the converter (54) and (ii) determines the voltage controlled by the converter (54) based on a first state variable which is linked to the torque of an output shaft of the multi-speed transmission (30) and a second state variable which is linked to a rotational speed of the output shaft.

Description

BACKGROUND OF THE INVENTION 1. Field of the invention

[0001] The invention relates to an electric vehicle and in particular to an electric vehicle having a transmission and a converter that regulates the voltage supplied to a drive unit that drives an electric motor. 2. Description of the state of the art

[0002] WO 2003 / 015 254 A1, WO 2012 / 055 635 A2, and US 2004 / 0165 868 A1 each disclose a motor drive control system comprising an electric motor, an inverter, and a converter that regulates the inverter's input voltage. Based on the motor's speed and target output torque (torque command), the motor drive control system calculates the optimal voltage to be applied to the motor at any given time, and a target value for the inverter input voltage is set based on this optimal voltage. With this motor drive control system, the inverter input voltage can be optimized according to the motor's operating conditions, and the motor can be driven efficiently.

[0003] If a gearbox is used in the power transmission path between the electric motor's rotating shaft and the drive wheels, the operating point (speed and torque) of the electric motor can change rapidly due to gearbox shifting (a change in the gear ratio). In the motor drive control system described in WO 2003 / 015 254 A1, WO 2012 / 055 635 A2, and US 2004 / 0165 868 A1, the inverter input voltage setpoint is determined based on the electric motor's operating point. Therefore, the inverter input voltage is unable to follow rapid changes in the electric motor's operating point. Consequently, the electric motor may be temporarily unable to produce the desired torque, and the vehicle's handling may deteriorate. BRIEF SUMMARY OF THE INVENTION

[0004] In view of the problem described above, the invention provides an electric vehicle comprising a transmission, a converter that regulates the voltage to be supplied to a drive unit that drives an electric motor, and a control unit, and in which it is less likely or improbable that it will suffer from a deterioration in driving performance due to rapid changes in the operating point of the electric motor.

[0005] According to one embodiment of the invention, an electric vehicle comprises an electric motor, a multi-speed transmission, a drive unit, a converter, and an electronic control unit. The multi-speed transmission has a plurality of gear positions and is arranged in a power transmission path between a rotating shaft of the electric motor and the drive wheels of the electric vehicle. The drive unit is designed to drive the electric motor. The converter is designed to regulate a voltage supplied to the drive unit. The electronic control unit is designed to control the converter and determine the voltage regulated by the converter based on a first state variable, which is related to the torque of an output shaft of the multi-speed transmission, and a second state variable, which is related to the rotational speed of the output shaft.

[0006] According to the electric vehicle described above, a target voltage of the converter is set based on the first state variable, which is linked to the torque of the output shaft of the multi-speed transmission, and the second state variable, which is linked to the rotational speed of the output shaft of the multi-speed transmission. Therefore, rapid fluctuations in the voltage to be regulated (target voltage) due to rapid changes in the operating point of the electric motor are suppressed or reduced. With the electric vehicle designed as described above, the target voltage is thus stabilized, and consequently, a deterioration in driving performance can be controlled or reduced.

[0007] In the electric vehicle described above, the electronic control unit can be designed to adjust the voltage regulated by the converter to a higher level when a value of the first state variable is larger.

[0008] Furthermore, the electronic control unit in the electric vehicle described above can be designed to adjust the voltage regulated by the converter to a higher level when a value of the second state variable is larger.

[0009] The electric vehicle designed as described above can keep a lack of torque in the electric motor and / or the output shaft (drive shaft) of the multi-speed transmission in check, and can keep a deterioration in driving behavior in check or reduce it.

[0010] Furthermore, the electronic control unit in the electric vehicle described above can be designed to (i) determine a first voltage based on the first state variable and the second state variable, which specifies a target voltage value, (ii) determine a second voltage based on an operating point of the electric motor, which specifies the target value, (iii) determine a target voltage based on the first voltage and the second voltage, and (iv) control the converter in such a way that the voltage becomes equal to the target voltage.

[0011] If the target voltage is determined based solely on the first and second state variables associated with the output shaft of the multi-speed transmission, the target voltage may deviate from the voltage level at which an electrical system consisting of the electric motor, drive unit, and converter operates efficiently, and the efficiency may be significantly lower. However, in the electric vehicle described above, the second voltage is also taken into account when determining the target voltage, allowing it to be set with the efficiency of the electrical system in mind. Consequently, it is possible to mitigate deterioration in driving performance and also to control a reduction in the efficiency of the electrical system.

[0012] In the electric vehicle described above, the electronic control unit can be designed to set the target voltage so that the target voltage moves closer to the first voltage when the electric vehicle's driving load is greater.

[0013] When the driving load is high, the target voltage is set using the electric vehicle designed as described above, while the focus is placed on the first and second state variables linked to the output shaft of the multi-speed transmission, thus fulfilling the user requirement of allowing the vehicle to operate under a high load. Conversely, when the driving load is low, the target voltage is set, while the focus is placed on the operating point of the electric motor, enabling the electrical system to operate efficiently.

[0014] In the electric vehicle described above, the electronic control unit can be designed as follows. Specifically, the electronic control unit can be designed to (i) determine a first voltage based on the first and second state variables, specifying a target voltage value; (ii) determine a second voltage based on an operating point of the electric motor, specifying the target value; (iii) determine a third voltage, specifying the target value, by assigning predetermined weights to the first and second voltages; (iv) determine a target voltage based on the third voltage; and (v) control the converter such that the voltage becomes equal to the target voltage.

[0015] According to the electric vehicle described above, the converter is controlled to achieve the target voltage, which appropriately accounts for the first and second voltages with suitable weights assigned to them. This makes it possible to limit a reduction in the efficiency of the electrical system and also to limit or reduce any deterioration in driving performance.

[0016] In the electric vehicle described above, the electronic control unit can also be designed to adjust the weights such that the third voltage becomes equal to a value closer to the first voltage when a driving load is greater than or equal to a predetermined value, and the third voltage becomes equal to a value closer to the second voltage when the driving load is less than the predetermined value.

[0017] When the driving load is high, the third voltage (target voltage) of the electric vehicle, as described above, is set close to the first setpoint voltage, thus fulfilling the user requirement to operate the vehicle under a heavy load. Conversely, when the driving load is low, the third voltage (target voltage) is set close to the second setpoint voltage, according to the operating conditions of the electric motor, making it less likely or even impossible for the efficiency of the electrical system to decrease.

[0018] In the electric vehicle described above, hysteresis can be provided between a first shift line and a second shift line. The first shift line indicates an upshift of the multi-speed transmission from a first gear position to a second gear position, and the second shift line indicates a downshift of the multi-speed transmission from a second gear position to a first gear position. The electronic control unit can be designed to establish a target voltage, regulated by the converter, based on a predefined setpoint voltage, when the first and second state variables are within a range of hysteresis.

[0019] If it is predicted that the multi-speed transmission will soon shift up or down, the electric vehicle, as described above, sets the target voltage based on the pre-defined setpoint voltage. This suppresses or reduces rapid fluctuations in the target voltage caused by rapid changes in the electric motor's operating point during shifting. Consequently, the target voltage is stabilized at the time of shifting, thus preventing any deterioration in driving performance during the shift.

[0020] Furthermore, in the electric vehicle described above, the first state variable can be either the torque of the output shaft of the multi-speed transmission, the vehicle's driving force, or the accelerator pedal travel. The second state variable can be either the rotational speed of the output shaft or the vehicle speed.

[0021] According to the electric vehicle described above, the converter's target voltage is stabilized, and consequently, a deterioration in driving performance can be kept in check.

[0022] In the electric vehicle, which has the converter that regulates the voltage supplied to the drive unit that drives the electric motor, a deterioration of the driving behavior due to rapid changes in the operating point of the electric motor can be kept in check according to the invention, and a reduction in the efficiency of the electrical system can be kept in check. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] With reference to the accompanying drawings, in which identical numbers denote identical elements, the features, advantages, and technical and industrial significance of exemplary embodiments of the invention are described. The drawings show: Fig. 1 a view showing the overall design of a hybrid vehicle, which is represented as an example of an electric vehicle according to a first embodiment of the invention; Fig. 2. A view showing the main signals and commands issued by a device in Fig. 1 control unit shown are received or generated; Fig. 3 A view showing the design of a differential unit and a gearbox, which are in Fig. 1 are shown; Fig. 4 a nomogram of a power split device showing changes in the rotational speeds of its components at the time of switching the in Fig. The gearbox shown in 1 shows; Fig. 5 a view showing an example that sets a target voltage according to the first embodiment; Fig. 6 is a flowchart that is useful for explaining a procedure that sets the target voltage according to the first embodiment; Fig. Figure 7 is a view showing an example which, in a second embodiment of the invention, sets a second setting voltage based on the operating conditions of a motor-generator; Fig. Figure 8 is a view which, in the second embodiment, shows the relationship between vehicle load and a weighting factor; Fig. Figure 9 is a flowchart that is useful for explaining a procedure that sets a target voltage according to the second embodiment; Fig. Figure 10 is a view showing an example which, in a third embodiment of the invention, sets a first setting voltage based on a torque and a speed of the output shaft of the gearbox; and Fig. Figure 11 is a flowchart that is useful for explaining a procedure that sets a target voltage according to the third embodiment. DETAILED DESCRIPTION OF EXAMPLES OF EXECUTION

[0024] With reference to the drawings, several embodiments of the invention are described in detail. Although three embodiments are described, the configurations or arrangements described in each embodiment should be able to be combined as needed from the date of filing of this application. In the drawings, the same or corresponding sections or elements are assigned the same reference numbers, and their explanations are not repeated.

[0025] The overall design of a vehicle according to a first embodiment of the invention will now be described. Fig. Figure 1 shows the overall design of a hybrid vehicle 10, which is presented as an example of an electric vehicle according to the first embodiment of this invention. As shown in Figure 1, the overall design of the vehicle is as follows: Fig. As can be seen from Figure 1, the hybrid vehicle 10 comprises a machine 12, a differential unit 20, a transmission 30, a differential gear device 42, and drive wheels 44. The hybrid vehicle 10 also comprises an inverter 52, a converter 54, an energy storage device 56, and a control unit 60.

[0026] The machine 12 is an internal combustion engine that generates power by converting thermal energy produced by the combustion of fuel into kinetic energy to move an object, such as a piston or a rotor. The differential unit 20 is coupled to the machine 12. The differential unit 20 comprises motor-generators driven by the inverter 52 and a power-splitting device that distributes the power output of the machine 12 to a transmission component connected to the gearbox 30 and to one of the motor-generators. The design of the differential unit 20 will be described later.

[0027] The transmission 30 is coupled to the differential unit 20 and designed such that the ratio (gear ratio) of the rotational speed of the transmission component connected to the differential unit 20 (an input shaft of the transmission 30) and the rotational speed of a drive shaft connected to the differential gear assembly 42 (an output shaft of the transmission 30) can be changed. The transmission 30 is a multi-speed transmission with two or more gear positions, and the gear ratio of the transmission 30 can be changed in steps. The differential gear assembly 42 is coupled to the output shaft of the transmission 30 and transmits the power supplied by the transmission 30 to the drive wheels 44. The design of the transmission 30, together with the differential unit 20, will also be described later.

[0028] The inverter 52 is controlled by the control unit 60 and drives the motor-generators contained in the differential unit 20. The inverter 52 consists of bridge circuits, each containing, for example, power semiconductor switching devices for three phases.

[0029] The converter 54 is electrically connected between the inverter 52 and the energy storage device 56. The converter 54 is controlled by the control unit 60 and regulates the voltage supplied to the inverter 52. More precisely, the converter 54 raises or amplifies the voltage supplied to the inverter 52 to a higher level than the voltage of the energy storage device 56. The converter 54 consists, for example, of a gain-chopper circuit with current reversal.

[0030] The energy storage device 56 is a rechargeable DC power supply and typically consists of a secondary battery, such as a lithium-ion battery or a nickel-hydride battery. The energy storage device 56 can also consist of an energy storage element, such as an electrical double-layer capacitor, instead of the secondary battery.

[0031] The control unit 60 is an electronic control unit comprising a machine ECU (ECU: electronic control unit) 62, an MG ECU 64, a battery ECU 66, an ECT ECU 68, and an HV ECU 70. Each ECU has a CPU (central processing unit), a memory device, an input / output buffer, etc. (all of which are not shown) and performs a specific control function. The control function performed by each ECU is not limited to software processing but can also be performed by separate hardware (electronic circuitry).

[0032] Based on a machine torque command etc. received from the HV-ECU 70, the machine ECU 62 generates a throttle signal, ignition signal etc. to drive the machine 12 and outputs the signals thus generated to the machine 12.

[0033] Based on a voltage command value, which specifies a target voltage for the converter 54 (a target value for the input voltage of the inverter 52) and is received by the HV-ECU 70, the MG-ECU 64 generates a control signal to operate the converter 54. The MG-ECU 64 then outputs this control signal to the converter 54. Furthermore, based on a torque command, etc., for each motor-generator contained in the differential unit 20, which is received by the HV-ECU 70, the MG-ECU 64 generates a control signal to operate the inverter 52. The MG-ECU 64 then outputs this control signal to the inverter 52.

[0034] Based on the current and / or voltage of the energy storage device 56, the battery ECU 66 estimates the state of charge of the energy storage device 56 (which is indicated by a SOC value representing the amount of electricity or electrical current currently stored in it as a percentage of the fully charged state) and outputs the estimated value to the HV ECU 70. Based on a torque capacity command, etc., received from the HV ECU 70, the ECT ECU 68 generates a hydraulic command value for controlling the transmission 30 and outputs this hydraulic command value to the transmission 30.

[0035] The HV-ECU 70 receives signals from various sensors and generates various commands to control each device of the hybrid vehicle 10. Based on the amount of accelerator pedal input, vehicle speed, etc., the HV-ECU 70 generates various commands to propel the vehicle while controlling the motor 12 and differential unit 20 into desired states. It also generates various commands to control the transmission 30 into a desired gear change state. Furthermore, the HV-ECU 70 generates a voltage command value (a target voltage) that specifies the target voltage to be regulated by the converter 54 and supplied to the inverter 52.

[0036] Fig. 2 is a view that shows main signals and commands issued by the in Fig. The control unit 60 shown in section 1 is received and generated. As shown in the diagram, the following information is displayed: Fig. As shown in Figure 2, the HV-ECU 70 receives a signal from a vehicle speed sensor that detects the speed of the hybrid vehicle 10, a signal from an accelerator pedal position sensor that detects the amount of accelerator pedal actuation, and a signal from an engine speed sensor that detects the speed of the engine 12. Furthermore, the HV-ECU 70 also detects a signal from an MG1 speed sensor to detect the speed of a motor-generator MG1 (which will be described later) contained in the differential unit 20, a signal from an MG2 speed sensor to detect the speed of a motor-generator MG2 (which will be described later) contained in the differential unit 20, and a signal from an output shaft speed sensor to detect the speed of the output shaft of the transmission 30.

[0037] Furthermore, the HV-ECU 70 also includes a signal from a lubricating oil temperature sensor, which detects the temperature of the lubricating oil of the differential unit 20 and the transmission 30; a signal from a shift position sensor, which detects a shift position selected by (specified by) a shift lever; and a signal from a VH sensor, which detects the voltage VH regulated by the converter 54 (input voltage of the inverter 52). Additionally, the HV-ECU 70 receives a signal from the battery ECU 66, which indicates the state of charge (SOC) of the energy storage device 56.

[0038] Based on the signals described above, the HV-ECU 70 then generates a machine torque command value Ter, which indicates a target value for the output torque of machine 12, and outputs the command value Ter to the machine ECU 62. The HV-ECU 70 also generates torque command values ​​Tgr and Tmr for the motor-generators MG1 and MG2 of the differential unit 20 and outputs these command values ​​to the MG-ECU 64. Furthermore, according to a predetermined shift map, the HV-ECU 70 sets a gear position for the transmission 30 and generates a torque capacity command value Tcr to set the gear position, outputting this command value to the ECT-ECU 68.

[0039] Furthermore, the HV-ECU 70 sets a target voltage VHr, which indicates a target value of the voltage VH regulated by the converter 54, and outputs the target voltage VHr to the MG-ECU 64. More precisely, the HV-ECU 70 calculates an output shaft torque of the differential unit 20 (corresponding to an input shaft torque of the transmission 30), which can be calculated using the machine torque command value Ter and the torque command values ​​Tgr, Tmr of the motor generators MG1, MG2, and the gear ratio of the transmission 30. Then, using a pre-generated map or comparison expression (or expressions) based on the output shaft torque of the transmission 30 and the speed of the transmission 30's output shaft detected by the output shaft speed sensor, the HV-ECU 70 sets the target voltage VHr specified above.The method used to determine the target voltage VHr will be described later.

[0040] The machine ECU 62, which receives the machine torque command value Ter from the HV ECU 70, generates the throttle signal, ignition signal, etc., to drive machine 12 and outputs the signals to machine 12. Based on the torque command values ​​Tgr, Tmr received from the HV ECU 70, the MG ECU 64 generates signals PWI1, PWI2 to drive the motor-generators MG1, MG2 via the inverter 52 and outputs the signals to the inverter 52. Furthermore, based on the target voltage VHr received from the HV ECU 70, the MG ECU 64 generates a signal PWC to control the converter 54 so that the voltage VH equals the target value VHr and outputs the signal PWC to the converter 54. The ECT-ECU 68 generates a hydraulic command value that causes the gearbox 30 to have a torque capacity corresponding to the torque capacity command value Tcr, and outputs the command value to the gearbox 30. Design of the differential unit and the transmission

[0041] Fig. Figure 3 shows the design of the differential unit 20 and the transmission 30, which are in Fig. Figure 1 shows the following. In the first embodiment, the differential unit 20 and the transmission 30 are designed or arranged symmetrically with respect to their axes, which is why the lower halves of the differential unit 20 and the transmission 30 are not in Fig. 3 are shown.

[0042] As from Fig. As shown in Figure 3, the differential unit 20 comprises the motor-generators MG1 and MG2 and the power-splitting device 24. Each of the motor-generators MG1 and MG2 is an AC electric motor and is in the form of, for example, a permanent magnet synchronous motor, which has a rotor in which permanent magnets are embedded. The motor-generators MG1 and MG2 are driven by the inverter 52.

[0043] The power splitting device 24 consists of a single-pinion planetary gear unit and comprises a sun gear S0, pinion gears P0, a carrier CA0, and a ring gear R0. The carrier CA0 is coupled to the input shaft 22 or the output shaft of the machine 12 and supports the pinion gears P0 such that the gears P0 can rotate about themselves and the axis of the planetary gear unit. The sun gear S0 is coupled to a rotating shaft of the motor-generator MG1. The ring gear R0 is coupled to the gear unit 26 and is designed to mesh with the sun gear S0 via the pinion gears P0. A rotating shaft of the motor-generator MG2 is coupled to the gear unit 26. The ring gear R0 is therefore also coupled to the rotating shaft of the motor-generator MG2.

[0044] The power split device 24 acts as a differential device when the sun gear S0, the carrier CA0, and the ring gear R0 rotate relative to each other. The respective rotational speeds of the sun gear S0, the carrier CA0, and the ring gear R0 are, as shown in a nomogram (see Fig. 4) connected by a straight line. Due to the differential function of the power splitting device 24, power generated by the machine 12 is distributed to the sun gear S0 and the ring gear R0. The motor-generator MG1 operates as a generator using the power distributed to the sun gear S0, and electrical current generated by the motor-generator MG1 is supplied to the motor-generator MG2 or stored in the energy storage device 56 ( Fig. 1) stored. The motor-generator MG1 generates electric current using the power branched by the power-splitting device 24, and the motor-generator MG2 is driven using the electric current generated by the motor-generator MG1. In this way, the differential unit 20 functions as a continuously variable transmission.

[0045] The gearbox 30 comprises single-pinion planetary gear sets 32 and 34, clutches C1-C3, brakes B1 and B2, and a freewheel F1. The planetary gear set 32 ​​has a sun gear S1, pinion gears P1, a carrier CA1, and a ring gear R1. The planetary gear set 34 has a sun gear S2, pinion gears P2, a carrier CA2, and a ring gear R2.

[0046] Each of the clutches C1-C3 and brakes B1, B2 is a hydraulically actuated friction device and consists of a wet multi-plate clutch or brake in which a plurality of stacked layers of friction plates are hydraulically pressed, or a band brake which has a band wound around the outer circumferential surface of a rotating drum and can be actuated by hydraulically tightening one end of the band, or the like. The freewheel F1 carries the carrier CA1 and the ring gear R2, which are coupled to each other to allow them to rotate in one direction and prevent them from rotating in the other. With this arrangement, each of the clutches C1-C3 and brakes B1, B2 is selectively engaged or disengaged, so that a gear position is selectively chosen in the transmission 30 from gear position 1st gear to gear position 4th gear and gear position reverse gear.When all engagement devices of the clutches C1 - C3 and brakes B1, B2 are in the released state, a neutral state (a state in which the power transmission is cut off) can be formed.

[0047] The differential unit 20 and the transmission 30 are coupled by the transmission component 26. The output shaft 36, coupled to the carrier CA2 of the planetary gear 34, is connected to the differential gear device 42 ( Fig. 1) coupled.

[0048] Fig. Figure 4 is a nomogram of the power split device 24, showing changes in rotational speed at the time of gear shifting 30. As shown from Fig. As can be seen from Figure 4, the rotational speed V of the drive shaft (the output shaft of the transmission 30) is limited by the rotation of the drive wheels, which is why the rotational speed V of the drive shaft hardly changes before and after shifting (downwards or upwards). Accordingly, the rotational speed of the input shaft of the transmission 30, namely the rotational speed ωm of the motor-generator MG2, increases at the time of downshifting (when the gear ratio increases), as shown by the single-point dashed line in Figure 4. Fig. 4 is indicated. On the other hand, the rotational speed ωm of the motor-generator MG2 decreases at the time of upshifting (when the gear ratio decreases), as shown by the two-dot dashed line in Fig. 4 is indicated.

[0049] The transmission 30 is provided in the power transmission path between the rotating shaft of the motor-generator MG2 and the drive shaft (the drive wheels). In the hybrid vehicle 10 according to this embodiment, the operating point (the speed and the torque) of the motor-generator MG2 changes rapidly before and after the shifting of the transmission 30, as described above (as in Fig. As shown in Figure 4, the operating point of motor-generator MG1 also changes rapidly. If the target voltage VHr is determined based on the operating points of motor-generators MG1 and MG2, the target voltage VHr may not be able to keep pace with the rapid changes in the operating points of motor-generators MG1 and MG2, or the voltage VH may not be able to keep pace with the target voltage VHr. Consequently, motor-generators MG1 and MG2 may be temporarily unable to generate the desired torque because the voltage VH supplied to inverter 52 is insufficient, and the vehicle's performance may deteriorate.

[0050] In the hybrid vehicle 10 according to this embodiment, the target voltage VHr is therefore not determined based on the operating points of the motor-generators MG1, MG2, but based on the torque and speed of the output shaft (drive shaft) of the transmission 30. Thus, rapid fluctuations of the target voltage VHr due to rapid changes in the operating points of the motor-generators MG1, MG2 can be controlled or reduced, and the target voltage VHr can be set to a value that reflects a driving load.

[0051] The target voltage VHr is set to a value that is higher when the torque and speed of the gearbox output shaft are greater than 30. Fig. Figure 5 shows an example that, in the first embodiment, sets the target voltage VHr. Fig. Figure 5 indicates the horizontal axis representing the rotational speed of the output shaft of the gearbox 30, and the vertical axis representing the torque of the output shaft of the gearbox 30. The torque of the output shaft of the gearbox 30 is a command value representing the target torque, and it can be calculated based on the output shaft torque of the differential unit 20, which corresponds to the input shaft torque of the gearbox 30, calculated using the machine torque command value Ter and the torque command values ​​Tgr, Tmr of the motor-generators MG1, MG2, and the gear ratio of the gearbox 30.

[0052] In Fig. Curve k1 is a level curve on which the target voltage VHr is set to, for example, V1. Curve k2 is a level curve on which the target voltage VHr is set to, for example, V2, where V2 is greater than V1. Curve k3 is a level curve on which the target voltage VHr is set to, for example, V3, where V3 is greater than V2. Thus, the target voltage VHr is set so that it is higher when the torque and speed of the output shaft of gearbox 30 are greater, making it less likely or improbable that the torques of the motor-generators MG1, MG2, and the output shaft of gearbox 30 will be insufficient.

[0053] Fig. Figure 6 is a flowchart useful for explaining a procedure that sets the target voltage according to this embodiment. As shown in Figure 6, the process is as follows: Fig. As can be seen from 6, the HV-ECU calculates 70 ( Fig. 1, Fig. 2) the torque of the output shaft of the gearbox 30 (step S2). As described above, the torque of the output shaft of the gearbox 30 can be calculated based on the output shaft torque of the differential unit 20, which is calculated using the machine torque command value Ter and the torque command values ​​Tgr, Tmr of the motor-generators MG1, MG2, and the gear ratio of the gearbox 30.

[0054] The HV-ECU 70 then receives the speed of the output shaft of gearbox 30 from the output shaft speed sensor (step S4). The HV-ECU 70 then uses the information in Fig. 5 shown relationship (characteristic map or comparison expression) based on the torque of the output shaft of the gearbox 30 calculated in step S2 and the speed of the output shaft of the gearbox 30 obtained in step S4, a target voltage VHr is entered.

[0055] As described above, in the first embodiment, the target voltage VHr of the converter 54 is determined based on the torque and speed of the output shaft of the transmission 30. This prevents or reduces rapid fluctuations in the target voltage VHr caused by rapid changes in the operating points of the motor-generators MG1 and MG2. Thus, the target voltage VHr is stabilized according to the first embodiment, and consequently, a deterioration in driving performance can be reduced.

[0056] Next, a second embodiment of the invention is described. In the first embodiment described above, the target voltage VHr is determined based on the torque and speed of the output shaft of the transmission 30, which can reduce the efficiency of an electrical system consisting of the converter 54, the inverter 52, and the motor-generators MG1 and MG2. From the perspective of efficient operation of the electrical system, it is preferable to determine the target voltage VHr based on the operating points of the motor-generators MG1 and MG2, which are driven by the inverter 52 that receives the voltage VH. However, if the target voltage is set based solely on the operating points of the motor-generators MG1 and MG2, the driving characteristics can deteriorate, as described above, due to rapid changes in the operating points of the motor-generators MG1 and MG2.

[0057] Thus, in the second embodiment, a first settling voltage VH1 is determined based on the torque and speed of the output shaft of the gearbox 30, and a second settling voltage VH2 is determined based on the operating points of the motor-generators MG1 and MG2. The target voltage VHr is then determined based on the first settling voltage VH1 and the second settling voltage VH2. It is therefore possible to adjust the target voltage VHr with regard to the efficiency of the electrical system while minimizing any deterioration in driving performance.

[0058] Fig. Figure 7 shows an example that sets the second setting voltage VH2 based on the operating conditions of the motor-generator MG2. Fig. Figure 7 indicates the vertical axis of motor-generator MG2, and the horizontal axis indicates the rotational speed of motor-generator MG2. Curve k5 indicates the maximum torque of motor-generator MG2.

[0059] In Fig. Curve k6 is a level curve on which the second adjustment voltage VH2 is set to V1. Curve k7 is a level curve on which the second adjustment voltage VH2 is set to V2, where V2 is greater than V1. Curve k8 is a level curve on which the second adjustment voltage VH2 is set to V3, where V3 is greater than V2. The second adjustment voltage VH2 is set to a higher value when the torque and speed of the motor-generator MG2 are greater.

[0060] In fact, the second setting voltage VH2 with respect to the motor-generator MG1 is determined in a similar way, and the larger of the second setting voltage VH2 determined on the basis of the operating point of the motor-generator MG2 and the second setting voltage VH2 determined on the basis of the operating point of the motor-generator MG1 is used as the final second setting voltage VH2.

[0061] The first setting voltage VH1, which is based on the torque and speed of the output shaft of the gearbox 30, is determined based on the in Fig. The relationship shown in the first embodiment is set. Then the target voltage VHr is calculated based on the first setting voltage VH1 and the second setting voltage VH2 according to the following equation. Target voltage VHr=W×VH1+(1−W)×VH2

[0062] In this equation, W is a weighting factor that can take a value from 0 to 1, where the weighting factor W is as in Fig. As shown in Figure 8, the target voltage VHr is set to a higher value when the vehicle's operating load is greater. Specifically, when the operating load is high, the target voltage VHr is set close to the first setting voltage VH1, which is linked to the operating load, in order to meet the user requirement of operating the vehicle under a heavy load. Conversely, when the operating load is low, the target voltage VHr is set close to the second setting voltage VH2, according to the operating conditions of the motor-generators MG1 and MG2, with a focus on the efficiency of the electrical system.

[0063] Regarding the driving load, the level of the driving load can be determined based on, for example, an integrated acceleration value of the acceleration / deceleration, the acceleration in the lateral direction or the like, or, if the vehicle has a sequential shifting system, a shifting operation.

[0064] Fig. Figure 9 is a flowchart useful for explaining a procedure that sets the target voltage VHr according to the second embodiment. As shown in Figure 9, the diagram illustrates the process of adjusting the target voltage VHr according to the second embodiment. Fig. As can be seen from 9, the HV-ECU 70 ( Fig. 1, Fig. 2) using the in Fig. The first setting voltage VH1 is set according to the relationship specified in section 5 (characteristic map or comparison expression) based on the torque and speed of the output shaft of the gearbox 30 (step S10). The torque of the output shaft of the gearbox 30 can be calculated as described above based on the output shaft torque of the differential unit 20, which is calculated using the machine torque command value Ter and the torque command values ​​Tgr, Tmr of the motor-generators MG1, MG2, and the gear ratio of the gearbox 30. The speed of the output shaft of the gearbox 30 is also obtained from the output shaft speed sensor.

[0065] The HV-ECU 70 then, based on the in Fig. 7 specified relationship (characteristic map or comparison expression) the second setting voltage VH2 based on the operating points (torques and speeds) of the motor-generators MG1, MG2 (step S20).

[0066] The HV-ECU 70 then calculates using the data in Fig. The HV-ECU 70 calculates the target voltage VHr based on the first set voltage VH1 set in step S10 and the second set voltage VH2 set in step S20 (step S30) using the specified relationship (characteristic map or comparison expression).

[0067] As described above, the target voltage VHr is set according to the second embodiment to reflect the second setpoint voltage VH2, which is based on the operating points (torques and speeds) of the motor-generators MG1 and MG2. Therefore, the target voltage VHr can be adjusted with regard to the efficiency of the electrical system.

[0068] When the driving load is high, the target voltage VHr is set close to the first setting voltage VH1, which is linked to the driving mode, according to the second embodiment, so that the user requirement to operate the vehicle under a high load can be met. Conversely, when the driving load is low, the target voltage VHr is set close to the second setting voltage VH2, according to the operating conditions of the motor-generators MG1 and MG2, so that it is less likely or even impossible for the efficiency of the electrical system to decrease.

[0069] Next, a third embodiment of the invention is described. In the second embodiment described above, when the driving load is high, the target voltage VHr is set close to the first setting voltage VH1, which is based on the torque and speed of the output shaft of the gearbox 30. Since the driving load is high in this case, both the first setting voltage VH1 and the target voltage VHr can be high. Therefore, even if the operating points of the motor-generators MG1 and MG2 change rapidly at the time of shifting the gearbox 30, a torque shortage at the motor-generators MG1 and MG2 is less likely or even improbable.

[0070] If the driving load is not high, the target voltage VHr is set close to the second setpoint voltage VH2, which is based on the operating points of the motor-generators MG1 and MG2. If the operating points of the motor-generators MG1 and MG2 change rapidly at the time of shifting, a corresponding torque deficiency may occur at the motor-generators MG1 and MG2. Therefore, if the driving load is not high and the transmission 30 is expected to shift up or down soon, the target voltage VHr is set in the third embodiment to a voltage that has been estimated in advance through testing or similar methods. This eliminates or prevents the possibility of a torque deficiency at the motor-generators MG1 and MG2 at the time of shifting.

[0071] Fig. Figure 10 shows an example in which, in the third embodiment, the first setting voltage VH1 is set based on the torque and speed of the output shaft of the gearbox 30. Fig. 10 are in addition to those in Fig. The 5 curves shown are k1 - k3, switching lines k11 - k13, k21 - k23.

[0072] Shift line k11 is an upshift line indicating the point at which the transmission 30 shifts from first to second gear. Shift line k12 is an upshift line indicating the point at which the transmission 30 shifts from second to third gear. Shift line k13 is an upshift line indicating the point at which the transmission 30 shifts from third to fourth gear. Furthermore, shift line k21 is a downshift line indicating the point at which the transmission 30 shifts from second to first gear. Shift line k22 is a downshift line indicating the point at which the transmission 30 shifts from third to second gear. Shift line k23 is a downshift line indicating the point at which the transmission 30 shifts from fourth to third gear. Thus, hysteresis is provided between the upshift and downshift operations.

[0073] In the region (A) between the switching lines k11, k21, the region (B) between the switching lines k12, k22, and the region (C) between the switching lines k13, k23, the initial setting voltage VH1 is adjusted differently than when the voltage is adjusted based on curves k1-k3, etc. The voltage is set to a value that was estimated in advance by trial or similar means. If the torque and speed of the output shaft of the transmission 30 are within one of the regions (A), (B), and (C), it is predicted that the transmission 30 will soon shift up or down. Therefore, as described above, the preliminary estimated voltage is set as the initial setting voltage VH1.

[0074] The target voltage VHr, set in each of the ranges (A), (B), and (C), can be increased when the output shaft torque is higher, and it can be adjusted according to the distances from the corresponding downshift and upshift lines. Furthermore, the target voltage VHr setting can be changed depending on whether the point defined by the torque and speed of the output shaft of the gearbox 30 approaches the downshift or upshift line. Additionally, if the rates of change of the torque and speed of the output shaft of the gearbox 30 are high, the target voltage VHr can be changed while the torque and speed of the output shaft of the gearbox 30 are outside of ranges (A), (B), and (C).

[0075] Fig. Figure 11 is a flowchart useful for explaining a procedure that, in the third embodiment, sets the target voltage VHr. As shown in Figure 11, the procedure is as follows: Fig. As can be seen in section 11, the flowchart contains, in addition to the steps described in the Fig. The flowchart of the second embodiment shown in 9 also includes steps S22 - S28.

[0076] Specifically, after the second setting voltage VH2 has been adjusted in step S20 based on the operating points (torques and speeds) of the motor-generators MG1 and MG2, the HV-ECU 70 determines whether the hybrid vehicle 10 is operating under a high load (step S22). The driving load is calculated based on an integrated acceleration value from the acceleration / deceleration or the lateral acceleration, or, if the vehicle has a sequential shift system, for example, from a shift operation, etc. If the driving load exceeds a predetermined threshold, it is determined that the vehicle is operating under a high load.

[0077] If step S22 detects that the vehicle is operating under a high load (YES in step S22), the control unit proceeds to step S30, in which the weighting factor W is calculated based on the vehicle load. Conversely, if step S22 detects that the vehicle is not operating under a high load (NO in step S22), the HV-ECU 70 determines whether the operating point (torque and speed) of the output shaft of the transmission 30 is within one of the switching hysteresis ranges (in Fig. 10 shown area (A), (B) or (C)) is contained (step S24).

[0078] If, in step S24, it is determined that the operating point of the output shaft of the gearbox 30 is within one of the switching hysteresis ranges (YES step S24), the HV-ECU 70, as described above, sets the first setting voltage VH1 based on the voltage estimated in advance by a test or similar procedure (step S26). Then, the HV-ECU 70 sets the target voltage VHr to the greater of the first setting voltage VH1 and the second setting voltage VH2, which was determined in step S20 based on the operating points (torques and speeds) of the motor-generators MG1 and MG2 (step S27).

[0079] If, on the other hand, it is determined in step S24 that the operating point of the output shaft of the gearbox 30 is outside the switching hysteresis ranges (NO in step S24), the HV-ECU 70 sets the target voltage VHr to the second setting voltage VH2, which is based on the operating points (torques and speeds) of the motor generators MG1, MG2 (step S28).

[0080] In the third embodiment, if it is predicted that the transmission 30 will soon shift up or down, the target voltage VHr is set, as described above, based on the pre-established setting voltage. Consequently, rapid fluctuations in the target voltage VHr due to rapid changes in the operating points of the motor-generators MG1 and MG2 caused by the shifting are suppressed or reduced. Thus, according to the third embodiment, the target voltage VHr is stabilized at the time of shifting, and a deterioration in driving performance at the time of shifting can therefore be controlled or reduced.

[0081] In each of the embodiments described above, the setpoint voltage VHr or the first setting voltage VH1 is determined based on the torque and speed of the output shaft of the transmission 30. However, instead of the torque of the output shaft of the transmission 30, the state variable associated with it can be the vehicle's driving force (which can be a command value or an actual value), an accelerator pedal stroke or angle, or the like. Furthermore, instead of the speed of the output shaft of the transmission 30, the vehicle speed or the like can be used as the state variable associated with it.

[0082] In each of the embodiments described above, the hybrid vehicle 10, which includes the machine 12 and the differential unit 20 containing the two motor-generators MG1 and MG2, has been described as an example of the electric vehicle. However, the electric vehicle to which this invention applies is not limited to the hybrid vehicle constructed as described above. For example, the motor-generator MG2 can be connected to the output shaft of the transmission 30. Furthermore, the electric vehicle to which the invention applies includes an electric car in which no machine is installed. In general, the electric vehicles according to the invention include vehicles that each comprise an electrical system with a converter, a power converter, and an electric motor (or electric motors), and a multi-speed transmission having a plurality of gear positions and arranged in a power transmission path.

[0083] In the above description, at least one of the motor-generators MG1, MG2 corresponds to an example of the "electric motor" according to the invention, and the inverter 52 corresponds to an example of the "drive unit" according to the invention.

Claims

[1] Electric vehicle (10), with: an electric motor (MG1, MG2); a multi-speed transmission (30) which has a plurality of gear positions and is arranged in a power transmission path between a rotating shaft of the electric motor (MG1, MG2) and drive wheels (44) of the electric vehicle (10); a drive unit (52) designed to drive the electric motor (MG1, MG2); a converter (54) designed to regulate a voltage supplied to the drive unit (52); and an electronic control unit (60) designed to (i) controls the converter (54) and (ii) determines the voltage controlled by the converter (54) based on a first state variable which is linked to the torque of an output shaft of the multi-gear transmission (30) and a second state variable which is linked to a rotational speed of the output shaft. [2] Electric vehicle (10) according to claim 1, wherein the electronic control unit (60) is designed to adjust the voltage regulated by the converter (54) to a higher level when a value of the first state variable is greater. [3] Electric vehicle (10) according to claim 1 or 2, wherein the electronic control unit (60) is designed to adjust the voltage regulated by the converter (54) to a higher level when a value of the second state variable is greater. [4] Electric vehicle (10) according to one of claims 1 to 3, wherein the electronic control unit (60) is designed such that it (i) based on the first state variable and the second state variable, establishes a first voltage which specifies a target value of the voltage, (ii) based on an operating point of the electric motor (MG1, MG2) specifies a second voltage which indicates the setpoint, (iii) determines a target voltage based on the first voltage and the second voltage and (iv) controls the converter (54) such that the voltage becomes equal to the setpoint. [5] Electric vehicle (10) according to claim 4, wherein the electronic control unit (60) is designed to set the target voltage such that the target voltage moves closer to the first voltage when the driving load of the electric vehicle (10) is greater. [6] Electric vehicle (10) according to one of claims 1 to 3, wherein the electronic control unit (60) is designed such that it (i) based on the first state variable and the second state variable, establishes a first voltage which specifies a target value of the voltage, (ii) based on an operating point of the electric motor (MG1, MG2) specifies a second voltage which indicates the setpoint, (iii) establishes a third voltage that specifies the target value by assigning predetermined weights to the first and second voltages, (iv) determines a target voltage based on the third voltage and (v) controls the converter (54) such that the voltage becomes equal to the target voltage. [7] Electric vehicle (10) according to claim 6, wherein the electronic control unit (60) is designed to adjust the weights such that the third voltage becomes equal to a value closer to the first voltage when the driving load of the electric vehicle (10) is greater than or equal to a predetermined value, and the third voltage becomes equal to a value closer to the second voltage when the driving load is less than the predetermined value. [8] Electric vehicle (10) according to one of claims 1 to 3, wherein A hysteresis is provided between a first shift line and a second shift line, wherein the first shift line indicates an upshift of the multi-speed transmission (30) from a first gear position to a second gear position and the second shift line indicates a downshift of the multi-speed transmission (30) from the second gear position to the first gear position; and the electronic control unit (60) is designed to determine a setpoint voltage regulated by the converter (54) based on a pre-established setting voltage when the first state variable and the second state variable are within a hysteresis range. [9] Electric vehicle (10) according to any one of claims 1 to 8, wherein the first state variable includes either the torque of the output shaft of the multi-speed transmission (30), the vehicle driving force, or an accelerator pedal stroke; and The second state variable includes either the rotational speed of the output shaft or the vehicle speed.

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