JP5799832B2 - Hybrid vehicle - Google Patents

Description

  The present invention relates to a hybrid vehicle, and more specifically, a hybrid including a mechanical oil pump configured to supply hydraulic oil to a traveling motor by being driven to rotate as the internal combustion engine rotates. The present invention relates to vehicle travel control.

  In recent years, hybrid vehicles equipped with an electric motor for driving and an internal combustion engine (engine) have attracted attention as environmentally friendly automobiles. As one aspect of a drive system of a hybrid vehicle, an engine, an electric motor, and a generator are known that are mechanically connected via a power split mechanism configured with a planetary gear.

  Japanese Patent Laid-Open No. 2010-195313 (Patent Document 1) discloses that in a hybrid vehicle having such a drive system, hydraulic oil is supplied to the motor using a mechanical oil pump driven by an engine. An arrangement for cooling and lubrication is described. Specifically, the control device for the hybrid vehicle calculates the flow rate of hydraulic oil supplied from the mechanical oil pump based on the engine speed, and calculates the predicted heat generation amount of the motor based on the operating state of the motor. To do. Then, the engine speed is controlled so that the flow rate of the hydraulic oil supplied from the mechanical oil pump approaches the flow rate of the hydraulic oil necessary for cooling the predicted heat generation amount of the electric motor.

JP 2010-195313 A JP 9-56009 A JP 2006-81240 A JP 2011-208711 A

  In the hybrid vehicle described in Patent Document 1, when the flow rate of the hydraulic oil from the mechanical oil pump is smaller than the flow rate of the hydraulic oil necessary for cooling the electric motor, the hydraulic oil is increased by increasing the engine speed. Increase the flow rate.

  However, as described above, in a hybrid vehicle having a drive system in which an engine, an electric motor, and a generator are mechanically coupled via a power split mechanism, when the engine output power is constant, the engine speed is increased. As the engine torque decreases, the drive torque (direct torque) that is mechanically transmitted to the drive shaft decreases. Therefore, in order to generate the required driving force to be output to the drive shaft, it is necessary to increase the output torque of the motor so as to compensate for the decrease in the direct torque. As a result, the loss (heat) generated in the electric motor increases, and there is a possibility that the cooling capacity of the electric motor will be reduced in spite of increasing the flow rate of the hydraulic oil.

  Therefore, the present invention has been made to solve such a problem, and an object of the present invention is to ensure the cooling capacity of an electric motor supplied with hydraulic oil from a mechanical oil pump driven by an engine in a hybrid vehicle. Is to increase.

  According to one aspect of the present invention, a hybrid vehicle includes an internal combustion engine, an electric motor configured to output torque to a drive shaft that is mechanically connected to drive wheels, and an internal combustion engine for the drive shaft. A power transmission device for mechanically transmitting torque originating from the output of the motor, a cooling device for cooling the electric motor, and an internal combustion engine and an electric motor so that the required driving force of the entire vehicle acts on the drive shaft And a control device for controlling the output. The cooling device includes a mechanical pump configured to be supplied to the electric motor with a refrigerant having a flow rate corresponding to the rotational speed of the internal combustion engine by being rotationally driven along with the rotation of the internal combustion engine. The control device maintains the output of the internal combustion engine more than the amount of increase in the temperature of the motor when the internal combustion engine operates at the first rotational speed for securing the output required for the internal combustion engine of the required driving force. On the other hand, when the amount of increase in the temperature of the electric motor when the internal combustion engine operates at the second rotational speed is small, the target rotational speed of the internal combustion engine is changed from the first rotational speed to the second rotational speed.

  Preferably, the control device is configured to execute an operating point change control for changing an operating point of the internal combustion engine on an equal power line for securing an output required for the internal combustion engine. The control device calculates the temperature rise of the motor based on the loss of the motor at each operating point and the thermal resistance of the cooling device, and based on the result of comparing the temperature rise of the motor calculated at each operating point. The target rotational speed of the internal combustion engine is determined.

  Preferably, the control device executes the operating point change control so as to move the operating point of the internal combustion engine from the intersection of the operating line capable of operating the internal combustion engine with high efficiency and the equal power line to the high rotation side. .

  Preferably, the control device moves the operating point of the internal combustion engine from the intersection of the operating line capable of operating the internal combustion engine with high efficiency and the equal power line to the low rotation side and the high rotation side, respectively. Perform change control.

  Preferably, the control device executes the operating point change control according to any of the temperature of the electric motor, the temperature of the refrigerant, the vehicle speed of the hybrid vehicle, and the wind speed of the traveling wind of the hybrid vehicle.

  Preferably, the hybrid vehicle further includes a generator for generating electric power by power from the internal combustion engine. The power transmission device includes a three-shaft power split device. The power split device is mechanically connected to the output shaft of the internal combustion engine, the output shaft of the generator, and the drive shaft, and the remainder is based on the power input to and output from any two of the three shafts. It is comprised so that motive power may be input and output to one axis.

  According to the present invention, in a hybrid vehicle including a mechanical oil pump configured to supply hydraulic oil to an electric motor by being driven by an internal combustion engine, the cooling capacity of the electric motor can be reliably increased.

1 is a schematic configuration diagram of a hybrid vehicle according to a first embodiment of the present invention. FIG. 2 is a circuit diagram of an electric system for driving and controlling the motor generator shown in FIG. 1. It is a figure explaining the whole structure of the cooling system mounted in the hybrid vehicle which concerns on Embodiment 1 of this invention. FIG. 4 is a diagram for explaining a motor generator cooling system in the transaxle of FIG. 3. It is a figure which shows a relationship between the rotation speed of an engine, and the flow volume of the hydraulic fluid supplied from an oil pump. It is a figure which shows the relationship between the flow volume of the hydraulic fluid supplied to a motor generator, and thermal resistance. It is a conceptual diagram for demonstrating the setting of the operating point of an engine. FIG. 2 is a collinear diagram when the hybrid vehicle shown in FIG. 1 is running. It is a flowchart explaining the engine operating point change control in the hybrid vehicle by Embodiment 1 of this invention. It is a conceptual diagram for demonstrating the engine operating point change control by this Embodiment 2. FIG. It is a flowchart explaining the engine operating point change control in the hybrid vehicle by Embodiment 2 of this invention. It is a figure which shows the relationship between the flow volume of the hydraulic fluid supplied from an oil pump, and thermal resistance. It is a figure which shows the relationship between the wind speed of the driving | running | working wind in a hybrid vehicle, and a vehicle speed. It is a flowchart explaining the modification of the engine operating point change control in the hybrid vehicle by embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same reference numerals indicate the same or corresponding parts.

[Embodiment 1]
FIG. 1 is a schematic configuration diagram of a hybrid vehicle according to Embodiment 1 of the present invention.

  Referring to FIG. 1, a hybrid vehicle 20 according to the first embodiment includes an engine 22, a crankshaft 26 as an output shaft of the engine 22, a torsional damper 28, a three-shaft power split mechanism 30, A battery 50. The crankshaft 26 is connected to the power split mechanism 30 via a torsional damper 28.

  Hybrid vehicle 20 further includes motor generators MG 1 and MG 2, a transmission 60, and a hybrid electronic control unit (hereinafter also referred to as “HVECU”) 70 that controls the entire drive system of hybrid vehicle 20.

  Motor generator MG <b> 2 is connected to power split mechanism 30 via transmission 60. Each of motor generators MG1 and MG2 can output both a positive torque and a negative torque, and can be driven as an electric motor as well as a generator.

  The engine 22 is an “internal combustion engine” that outputs power using a hydrocarbon fuel such as gasoline or light oil. The engine electronic control unit (hereinafter also referred to as “engine ECU”) 24 receives signals from various sensors that detect the operating state of the engine 22 such as the crank angle of the crankshaft 26 from the crank angle sensor 23. The engine ECU 24 communicates with the HVECU 70 and receives a control command for the engine 22 from the HVECU 70. The engine ECU 24 performs fuel injection control, ignition control, intake air amount control, etc. of the engine 22 so that the engine 22 operates in accordance with a control command from the HVECU 70 based on the operation state of the engine 22 based on signals from various sensors. Execute engine control. Furthermore, the engine ECU 24 outputs data relating to the operating state of the engine 22 to the HVECU 70 as necessary.

  The power split mechanism 30 includes an external gear sun gear 31, an internal gear ring gear 32 disposed concentrically with the sun gear 31, a plurality of pinion gears 33 that mesh with the sun gear 31 and mesh with the ring gear 32, and a carrier 34. The carrier 34 is configured to hold the plurality of pinion gears 33 so as to rotate and revolve freely. The power split mechanism 30 is configured as a planetary gear mechanism that performs a differential action with the sun gear 31, the ring gear 32, and the carrier 34 as rotational elements.

  The crankshaft 26 of the engine 22 is connected to the carrier 34, and the output shaft of the MG1 is connected to the sun gear 31 via the sun gear shaft 31a. The ring gear shaft 32 a as a “drive shaft” rotates as the ring gear 32 rotates. The output shaft of motor generator MG2 is connected to ring gear shaft 32a via transmission 60. Hereinafter, the ring gear shaft 32a is also referred to as a drive shaft 32a.

  The drive shaft 32a is mechanically coupled to the drive wheels 39a and 39b via a gear mechanism 37 and a differential gear 38. Therefore, the power output to the ring gear 32, that is, the drive shaft 32 a by the power split mechanism 30 is output to the drive wheels 39 a and 39 b via the gear mechanism 37 and the differential gear 38.

  Thus, the power split mechanism 30 corresponds to a “differential device”. The carrier 34 corresponds to a “first rotating element”, the sun gear 31 corresponds to a “second rotating element”, and the ring gear 32 corresponds to a “third rotating element”.

  Transmission 60 is configured to give a predetermined reduction ratio Gr between output shaft 48 of motor generator MG2 and drive shaft 32a. The transmission 60 is typically constituted by a planetary gear mechanism. The transmission 60 includes an external gear sun gear 65, an internal gear ring gear 66 arranged concentrically with the sun gear 65, and a plurality of pinion gears 67 that mesh with the sun gear 65 and mesh with the ring gear 66. Since the planetary carrier is fixed to the case 61, the plurality of pinion gears 67 only rotate without revolving. That is, the ratio (reduction ratio) of the rotational speeds of the sun gear 65 and the ring gear 66 is fixed.

  The configuration of the transmission 60 is not limited to the example of FIG. Alternatively, the output shaft of motor generator MG2 and ring gear shaft (drive shaft) 32a may be connected without using transmission 60.

  When motor generator MG1 functions as a generator, power from engine 22 input from carrier 34 is distributed to sun gear 31 side and ring gear 32 side according to the gear ratio. On the other hand, when motor generator MG1 functions as an electric motor, the power from engine 22 input from carrier 34 and the power from motor generator MG1 input from sun gear 31 are integrated and output to ring gear 32.

  Motor generators MG1 and MG2 are typically configured by a three-phase permanent magnet type synchronous motor. Motor generators MG1 and MG2 exchange power with battery 50 through converter 40 and inverters 41 and 42. Each of inverters 41 and 42 is configured by a general three-phase inverter having a plurality of switching elements.

  The battery 50 is shown as a representative example of the “power storage device”. As the battery 50, a lithium ion secondary battery or a nickel hydride secondary battery is typically applied. However, instead of the battery 50, another power storage device such as an electric double layer capacitor, or a combination of a secondary battery and another power storage device may be used.

  The battery 50 is managed by a battery electronic control unit (hereinafter also referred to as “battery ECU”) 52. A signal necessary for managing the battery 50 is input to the battery ECU 52. For example, a voltage between terminals from a voltage sensor (not shown) installed between terminals of the battery 50, a charge / discharge current of the battery 50 from a current sensor (not shown), a battery temperature from a temperature sensor (not shown) attached to the battery 50, and the like. Is input to the battery ECU 52. The battery ECU 52 outputs data related to the state of the battery 50 to the HVECU 70 by communication as necessary. In addition, in order to manage the battery 50, the battery ECU 52 also calculates a remaining capacity (SOC: State of Charge) based on the integrated value of the charge / discharge current detected by the current sensor.

  The battery 50, the SMR (System Main Relay) 55, the converter 40, and the inverters 41 and 42 constitute an electric system of the hybrid vehicle 20. SMR 55 is arranged between battery 50 and converter 40.

  FIG. 2 is a circuit diagram of an electric system for driving and controlling motor generators MG1 and MG2 shown in FIG.

  Referring to FIG. 2, when SMR 55 is off, battery 50 is disconnected from the electrical system. When SMR 55 is on, battery 50 is connected to the electrical system. The SMR 55 is turned on / off in response to a control signal from the HVECU 70. For example, in a state where the ignition switch 80 is turned on, the user performs an operation for starting operation, thereby instructing activation of the electric system. When the activation of the electric system is instructed, the HVECU 70 turns on the SMR 55.

  Converter 40 has a general boost chopper circuit configuration including a reactor and two power semiconductor switching elements (hereinafter also simply referred to as switching elements). As the power semiconductor switching element, a bipolar transistor, a power MOSFET (Metal Oxide Semiconductor Field-Effect Transistor), an IGBT (Insulated Gate Bipolar Transistor), or the like can be used. An antiparallel diode is connected to each switching element.

  Inverter 41 connected to motor generator MG1 includes a U-phase arm, a V-phase arm, and a W-phase arm. The U-phase arm, V-phase arm and W-phase arm are connected in parallel. Each of the U-phase arm, the V-phase arm, and the W-phase arm has two switching elements connected in series. Each switching element is provided with an antiparallel diode.

  Each phase coil (U, V, W) wound around a stator (not shown) of motor generator MG1 is alternately connected at neutral point 112. The connection point of the switching element in each phase arm of inverter 41 is connected to the end of each phase coil of motor generator MG1.

  Similarly to the inverter 41, the inverter 42 has a general three-phase inverter configuration. Each phase coil (U, V, W) wound around a stator (not shown) of motor generator MG 2 is connected alternately at neutral point 122. The connection point of the switching element in each phase arm of inverter 42 is connected to the end of each phase coil of motor generator MG2.

  When the electric power discharged from the battery 50 is supplied to the motor generator MG1 or MG2, the voltage is boosted by the converter 40. Conversely, when the battery 50 is charged with the electric power generated by the motor generator MG1 or MG2, the voltage is stepped down by the converter 40.

  System voltage VH, which is a DC voltage on power line 54 between converter 40 and inverters 41 and 42, is detected by voltage sensor 180. The detection result of voltage sensor 180 is transmitted to motor ECU 45.

  Converter 40 performs bidirectional DC voltage conversion between system voltage VH and voltage Vb of battery 50. The duty of the switching element of converter 40 is controlled such that system voltage VH of power line 54 matches voltage command value VHr.

  The inverter 41 converts the DC voltage on the power line 54 into an AC voltage by turning on and off the switching element. The converted AC voltage is supplied to motor generator MG1. Inverter 41 converts AC power generated by regenerative power generation by motor generator MG1 into DC power.

  Similarly, inverter 42 converts the DC voltage on power line 54 into an AC voltage and supplies it to motor generator MG2. Inverter 42 converts AC power generated by regenerative power generation by motor generator MG2 into DC power.

  Motor generators MG1, MG2 are both driven and controlled by a motor electronic control unit (hereinafter also referred to as “motor ECU”) 45. The motor ECU 45 receives signals necessary for driving and controlling the motor generators MG1 and MG2. For example, signals from rotational position detection sensors 43 and 44 that detect the rotational positions of the rotors of the motor generators MG1 and MG2, phase currents applied to the motor generators MG1 and MG2 detected by a current sensor (not shown), Input to the motor ECU 45. Based on the signals from the rotational position detection sensors 43 and 44, the rotational speeds of the motor generators MG1 and MG2 can be detected.

  Motor ECU 45 is in communication with HVECU 70 and controls motor generators MG1, MG2 in accordance with an operation command from HVECU 70. Specifically, motor ECU 45 outputs a switching control signal to inverters 41 and 42 such that output torques of motor generators MG1 and MG2 match torque command values Tr1 and Tr2. For example, motor ECU 45 outputs an output voltage command (AC voltage) of inverters 41 and 42 based on a deviation between a current command value set according to torque command values Tr1 and Tr2 and a current detection value of motor generators MG1 and MG2. Calculate. Then, the switching control signals of the inverters 41 and 42 are generated so that the pseudo AC voltage output from the inverters 41 and 42 approaches each output voltage command, for example, according to pulse width modulation control.

  Referring again to FIG. 1, hybrid vehicle 20 further includes a mechanical oil pump (hereinafter simply referred to as an oil pump) 90. The oil pump 90 is driven by the engine 22 to discharge hydraulic oil. The hydraulic oil is used to lubricate motor generators MG1 and MG2, power split mechanism 30 and transmission 60 constituting the trans-askule, to cool heat generating members such as motor generators MG1 and MG2 and gears, and to other hydraulic drive devices such as clutches and brakes. Used for driving (not shown). For example, the oil pump 90 is disposed coaxially with the crankshaft 26 of the engine 22 and is driven to rotate as the crankshaft 26 rotates. Therefore, the flow rate of the hydraulic oil supplied from the oil pump 90 increases as the rotational speed of the engine 22 increases.

  Even when the hybrid vehicle 20 is stopped, the oil pump 90 is rotationally driven by the rotation of the crankshaft 26 of the engine 22 via the power split mechanism 30 when the motor generator MG1 is driven. When the number of revolutions of the engine 22 increases and the motoring state is set, the operating oil can be discharged from the oil pump 90 without consuming fuel such as gasoline. As a result, by suppressing fuel consumption, the transaxle can be lubricated without deteriorating fuel consumption.

  The HVECU 70 is configured as a microprocessor centering on a CPU (Central Processing Unit) 72. The HVECU 70 includes a CPU 72, a ROM (Read Only Memory) 74 that stores processing programs, maps, and the like, a RAM (Random Access Memory) 76 that temporarily stores data, and an input / output port and a communication port (not shown). . The HVECU 70 includes an ignition signal from the ignition switch 80, a shift position SP from the shift position sensor 82 that detects the operation position of the shift lever 81, and an accelerator opening from the accelerator pedal position sensor 84 that detects the depression amount of the accelerator pedal 83. Acc, the brake pedal position BP from the brake pedal position sensor 86 that detects the depression amount of the brake pedal 85, the vehicle speed V from the vehicle speed sensor 88, and the like are input via the input port.

  Further, as described above, the HVECU 70 is connected to the engine ECU 24, the motor ECU 45, and the battery ECU 52 via the communication port. Accordingly, the HVECU 70 exchanges various control signals and data with other ECUs. Note that the engine ECU 24, the motor ECU 45, and the battery ECU 52 can also be configured by a microprocessor, similar to the HVECU 70. In FIG. 1, the HVECU 70, the engine ECU 24, the motor ECU 45, and the battery ECU 52 are described as separate ECUs, but an ECU in which some or all of these functions are integrated may be arranged. Or you may arrange | position ECU so that the function of each ECU shown in figure may be divided | segmented further.

  The HVECU 70 executes travel control for performing travel suitable for the vehicle state. For example, when starting the vehicle and traveling at a low speed, the hybrid vehicle 20 travels by the output of the motor generator MG2 with the engine 22 stopped. During steady running, the engine 22 is started, and the hybrid vehicle 20 runs by the outputs of the engine 22 and the motor generator MG2. In particular, the fuel efficiency of the hybrid vehicle 20 is improved by operating the engine 22 at a highly efficient operating point.

(Cooling system configuration)
FIG. 3 is a diagram illustrating an overall configuration of a cooling system mounted on the hybrid vehicle according to Embodiment 1 of the present invention.

  Referring to FIG. 3, the cooling system circulates cooling water, which is a liquid refrigerant, between transaxle 200 and PCU (Power Control Unit) 280 and radiator 290 by water pump 260, so that the interior of transaxle 200 is circulated. The heat generating members such as the motor generators MG1 and MG2 and the PCU 280 are cooled. Transaxle 200 includes motor generators MG1, MG2, power split mechanism 30, and transmission 60. PCU 280 includes a converter 40 and inverters 41 and 42 constituting the electrical system of FIG.

  The cooling system includes a reservoir tank 270, a refrigerant passage 220 provided between the reservoir tank 270 and the water pump 260, a refrigerant passage 210 provided between the water pump 260 and the transaxle 200, and the transaxle 200. And a refrigerant path 250 provided between the radiator 290 and the PCU 280, and a refrigerant path 230 provided between the PCU 280 and the reservoir tank 270. . That is, transaxle 200 and PCU 280 and water pump 260, reservoir tank 270 and radiator 290 are connected in series by refrigerant paths 210, 220, 230, 240 and 250.

  The water pump 260 is a pump for circulating cooling water such as antifreeze, and circulates cooling water in the direction of the arrow shown in the figure. Radiator 290 receives cooling water circulating through PCU 280 and transaxle 200 from refrigerant passage 250, and cools the received cooling water using a radiator fan (not shown). The reservoir tank 270 functions as an auxiliary tank for cooling water, and is provided to cope with changes in the temperature of the cooling water in the refrigerant path and the volume of the refrigerant path.

  In the cooling system shown in FIG. 3, the cooling water is circulated in the order of the radiator 290, the PCU 280, the reservoir tank 270, the water pump 260, and the transaxle 200. Note that the positions of the transaxle 200 and the PCU 280 are not limited to such positions. Further, the cooling system will be described as a cooling system different from the cooling system of the engine 22, but the cooling system according to the present invention is not limited to such a system. That is, even if a refrigerant path shared with the cooling system of the engine 22 is used, a refrigerant path is provided separately and a radiator is shared, or other shared forms (only a cooling fan for the radiator is shared, etc.) ).

  Temperature sensor 202 is provided in transaxle 200, detects the temperature (hereinafter also referred to as motor temperature) TMG of motor generators MG 1, MG 2, and outputs the detected motor temperature TMG to HVECU 70. The motor temperature TMG includes a motor temperature TMG1 that is the temperature of the motor generator MG1 and a motor temperature TMG2 that is the temperature of the motor generator MG2.

  Temperature sensor 204 is provided in refrigerant passage 250, detects the temperature of cooling water (hereinafter also referred to as cooling water temperature) THW, and outputs the detected cooling water temperature THW to HVECU 70. The HVECU 70 generates a signal for driving the water pump 260 based on the cooling water temperature THW from the temperature sensor 204 and outputs the signal to the water pump 260.

  In the cooling system shown in FIG. 3, in the transaxle 200, heat is generated between the hydraulic oil that has recovered the heat generated by the heat generating members such as the motor generators MG <b> 1 and MG <b> 2 and the cooling water supplied through the refrigerant path 210. Exchange is performed. Thereby, the heat accumulated in the hydraulic oil is radiated to the cooling water. That is, the heat generated in motor generators MG1 and MG2 is dissipated using hydraulic oil and cooling water as a heat transfer agent.

  FIG. 4 is a diagram for explaining a cooling system of the motor generator in the transaxle of FIG.

  Referring to FIG. 4, motor generator MG <b> 1 is housed in case 206. An oil pump 90 is provided outside the case 206. The oil pump 90 is connected to the crankshaft 26 of the engine 22 so as to be driven by the engine 22.

  Case 206 is provided with an oil passage 320 for sucking hydraulic oil from oil reservoir 310 inside the case and oil passages 330 and 340 for supplying hydraulic oil discharged from oil pump 90 to motor generator MG1. . A hydraulic oil discharge port 350 is provided at the end of the oil passage 340, and the hydraulic oil is supplied to the motor generator MG1.

  The hydraulic oil is first sucked up by the oil pump 90 from the oil reservoir 310 at the bottom of the case, and supplied from the oil passage 330 through the oil pump 90 to the motor generator MG1 through the oil passage 340. The supplied hydraulic oil cools the motor generator MG1 and then returns to the oil reservoir 310 by gravity drop.

  An oil cooler 300 is provided between the oil passage 330 and the oil passage 340. Oil cooler 300 receives hydraulic oil from oil passage 330 and cools the received hydraulic oil using cooling water. Specifically, the oil cooler 300 is provided with a water passage 302 through which cooling water flows. A refrigerant passage 210 is connected to the cooling water inlet to the water passage 302, and a refrigerant passage 250 is connected to the cooling water outlet from the water passage. The water passage 302 is formed so as to be able to exchange heat with the hydraulic oil passage. When the hydraulic oil radiated from the heat generated in motor generator MG1 circulates in the passage in oil cooler 300, the hydraulic oil and cooling water exchange heat, so that the heat accumulated in the hydraulic oil radiates to the cooling water. Is done. The heat generated in motor generator MG1 is radiated from oil cooler 300 through the working oil and cooling water as described above, and is radiated from case 206 through the working oil.

  Although illustration is omitted, a cooling system for cooling the gears constituting motor generator MG2, power split mechanism 30, and transmission 60 is also provided with the same configuration as in FIG.

  In the cooling system shown in FIG. 4, the oil pump 90 is rotationally driven as the crankshaft 26 of the engine 22 rotates as described above. Therefore, the relationship between the rotational speed of the engine 22 and the flow rate of hydraulic oil supplied from the oil pump 90 is that the flow rate of hydraulic oil increases as the rotational speed of the engine 22 increases, as shown in FIG. Is true. In FIG. 5, the horizontal axis indicates the rotational speed of the engine 22, and the vertical axis indicates the flow rate of the hydraulic oil supplied from the oil pump 90. Referring to FIG. 5, the flow of hydraulic oil discharged from oil pump 90 (corresponding to the total flow rate in the figure) increases as the rotational speed of engine 22 increases, whereby the operation supplied to motor generator MG1. The flow rate of oil (corresponding to the flow rate for MG1 in the figure) and the flow rate of hydraulic oil supplied to the motor generator MG2 (corresponding to the flow rate for MG2 in the figure) are increased.

  And if the flow volume of the hydraulic fluid supplied to a motor generator increases, the thermal resistance between a motor generator and a cooling system will fall. FIG. 6 shows the relationship between the flow rate of hydraulic oil supplied to motor generator MG1 and thermal resistance. In FIG. 6, the horizontal axis indicates the flow rate of the hydraulic oil supplied to the motor generator MG1, and the vertical axis indicates the thermal resistance between the motor generator MG1 and the cooling system. This thermal resistance includes the thermal resistance of the heat transfer path from motor generator MG1 to oil cooler 300 and the thermal resistance of the heat transfer path from motor generator MG1 to case 206.

  Referring to FIG. 6, as the flow rate of hydraulic oil supplied from oil pump 90 increases, the thermal resistance of the cooling system decreases. That is, the thermal resistance of the cooling system can be lowered by increasing the rotational speed of the engine 22.

  As described above, in the hybrid vehicle 20 according to the first embodiment, the cooling capacity of the cooling system can be controlled by controlling the rotational speed of the engine 22. FIG. 7 is a conceptual diagram for explaining setting of the operating point of the engine 22. Referring to FIG. 7, the engine operating point is defined by a combination of engine speed Ne and engine torque Te. The product of the engine speed Ne and the engine torque Te corresponds to the engine output power Pe.

  The operation line 500 is determined in advance as a set of engine operating points that can operate the engine 22 with high efficiency. The operation line 500 corresponds to an optimum fuel consumption line for suppressing fuel consumption at the same power output. The HVECU 70 determines the intersection of the predetermined operation line 500 and the equal power line 510 corresponding to the required power Pe * to the engine 22 as an engine operating point (target rotational speed Ne * and target torque Te *). That is, the engine operating point is determined as P1 in the figure. The target engine speed Ne * of the engine 22 is the engine speed NE1 at the engine operating point P1.

  Here, the engine operating point is changed from the operating point P1 corresponding to the engine speed NE1 to the operating point P2 in a state where the engine 22 outputs the engine required power Pe *. At the operating point P2, the operating point P1 and the engine output power Pe are equal. On the other hand, the engine speed NE2 is higher than the engine speed NE1. In this case, the engine torque Te is smaller at the operating point P2 than at the operating point P1.

  Since the engine operating point is changed so that the engine speed increases in this way, the flow rate of the hydraulic oil supplied from the oil pump 90 increases. As a result, the thermal resistance of the cooling system is lowered, so that the cooling capacity of the cooling system is expected to be improved.

  On the other hand, in hybrid vehicle 20 according to the first embodiment, engine 22, motor generator MG 1 and motor generator MG 2 are connected via power split mechanism 30. Therefore, the rotational speeds of engine 22, motor generator MG1 and motor generator MG2 are connected in a collinear diagram as shown in FIG.

  Referring to FIG. 8, during traveling, motor generator MG2 mainly operates as an “electric motor”, and motor generator MG1 mainly operates as a “generator”. Hereinafter, the torque and rotation speed of motor generator MG2 are also expressed as Tm and Nm, and the torque and rotation speed of motor generator MG1 are also expressed as Tg and Ng.

  The engine 22 is controlled by the engine ECU 24 (FIG. 1) so as to operate at an operating point (target rotational speed Ne * and target torque Te *) determined based on the engine required power Pe *.

  Torque Tg and rotation speed Ng of motor generator MG1 are controlled such that engine rotation speed Ne is set to target rotation speed Ne * according to the operating point. The torque Tg is expressed by the following equation (1) using the engine torque Te.

Tg = −ρ / (1 + ρ) × Te (1)
Note that ρ is a gear ratio in the power split mechanism 30. During normal running, motor generator MG1 outputs negative torque (Tg <0) and enters a state of generating electricity.

  At this time, the direct torque Tep transmitted to the drive shaft 32a by the torque Tg output so as to handle the reaction force of the engine torque Te is expressed by the following equation (2).

Tep = −Tg × (1 / ρ) (2)
On the other hand, torque generated on drive shaft 32a by torque Tm of motor generator MG2 using gear ratio (reduction ratio) Gr of transmission 60 is represented by Tm × Gr. Therefore, the following equation (3) is established for the drive torque Tp acting on the drive shaft 32a (ring gear 32).

Tp = Tm × Gr−Tg × (1 / ρ) (3)
When the HVECU 70 calculates the required drive torque Tp * from the vehicle state, the required drive torque Tm to the motor generator MG2 is compensated so as to compensate for the excess or deficiency (Tp * -Tep) of the direct torque Tep with respect to the required drive torque Tp *. * Is determined. Note that the vehicle state reflected in the calculation of the required drive torque Tp * typically includes the accelerator opening Acc indicating the amount of accelerator pedal operation by the user, the vehicle speed of the hybrid vehicle 20, and the like.

  It should be noted that the power charged / discharged to / from battery 50 when motor generators MG1 and MG2 are driven based on request drive torque Tp * calculated in this way is within the limit value of the charge / discharge power of battery 50. For example, the command is output as it is, but if the power charged / discharged to the battery 50 exceeds the limit value, the command value is limited based on the limit value.

  With such travel control, the total required power between the engine 22 and the motor generators MG1, MG2 is such that the required drive torque Tp * acts on the drive shaft 32a while operating the engine 22 on a highly efficient operation line. The power distribution for can be determined.

  Here, consider the case where the engine operating point is changed from the operating point P1 to the operating point P2, as described with reference to FIG.

  The engine torque Te decreases as the engine speed Ne increases from the engine speed NE1 to the engine speed NE2. Since the engine output power at the operating point P2 is equal to the engine output power, the engine torque TE2 at the operating point P2 is calculated according to the following equation (4) using the engine torque TE1 at the operating point P1.

TE2 = TE1 × NE1 / NE2 (4)
And since the engine torque Te decreased from TE1 to TE2, the direct torque Tep transmitted to the drive shaft 32a decreases. The decrease ΔTep of the direct torque is calculated by the following equation (5) based on the decrease ΔTe (= TE1−TE2) of the engine torque.

ΔTep = 1 / (1 + ρ) × ΔTe (5)
When direct torque Tep transmitted to drive shaft 32a decreases in this way, HVECU 70 determines required drive torque Tm * for motor generator MG2 so as to compensate for the decrease ΔTep in the direct torque. Thereby, an appropriate vehicle driving force according to the vehicle state is generated. The increment ΔTm of the torque Tm of the motor generator MG2 at this time is expressed by the following formula (6).

ΔTm = ΔTep / Gr = 1 / (1 + ρ) × ΔTe / Gr (6)
As described above, in hybrid vehicle 20 according to the first embodiment, torque Tm of motor generator MG2 is increased by changing the engine operating point so that the engine speed is increased. When the output torque Tm of motor generator MG2 increases, the current flowing through motor generator MG2 increases, so the loss (heat) generated in motor generator MG2 increases. That is, as the engine speed increases, the heat resistance of the cooling system decreases, while the amount of heat generated in motor generator MG2 increases. For example, when the relationship between the current I flowing through the motor generator MG2 and the loss W generated in the motor generator MG2 is approximated as in the following equation (7), the motor operating point is changed from the operating point P1 to the operating point P2. Assume that the current flowing through generator MG2 increases from current I1 to current I2. In this case, loss W of motor generator MG2 increases from W1 = A × I1 ² + B × I1 + C to W2 = A × I2 ² + B × I2 + C.

W = A × I ² + B × I + C (7)
Note that the amount of temperature increase TMG2 (hereinafter also referred to as motor temperature increase amount) ΔTMG2 of motor generator MG2 when motor generator MG2 is driven according to required drive torque Tm * is the loss W of motor generator MG2 and motor generator MG2 And the product of the thermal resistance R between the cooling systems. Therefore, motor temperature increase amount ΔTMG2 (P1) at operating point P1 corresponding to engine speed NE1 is calculated by the following equation (8) using loss W1 and thermal resistance R1 of motor generator MG2 at operating point P1. be able to.

ΔTMG2 (P1) = W1 × R1 (8)
Similarly, motor temperature increase ΔTMG2 (P2) at operating point P2 corresponding to engine speed NE2 is calculated by the following equation (9) using loss W2 and thermal resistance R2 of motor generator MG2 at operating point P2. can do.

ΔTMG2 (P2) = W2 × R2 (9)
Comparing the motor temperature increase ΔTMG2 (P1) at the operating point P1 with the motor temperature increase ΔTMG2 (P2) at the operating point P2, the thermal resistance R2 becomes smaller than the thermal resistance R1, but the loss W2 becomes larger than the loss W1. Therefore, the motor temperature increase amount ΔTMG2 (P2) is not necessarily smaller than the motor temperature increase amount ΔTMG2 (P1). Therefore, increasing the engine speed from the viewpoint of reducing the thermal resistance R increases the loss W of the motor generator MG2, which may lead to a temperature rise of the motor generator MG2.

  Therefore, in the first embodiment, when the motor temperature increase ΔTMG2 (P2) at the operating point P2 is smaller than the motor temperature increase ΔTMG2 (P1) at the operating point P1, the engine operating point is set to the operating point P1. To operating point P2. The HVECU 70 executes engine operating point change control in order to find an operating point P2 at which the motor temperature increase amount ΔTMG2 is smaller than the operating point P1. The engine operating point change control according to the first embodiment will be described with reference to the flowchart of FIG.

  FIG. 9 is a flowchart illustrating engine operating point change control in the hybrid vehicle according to the first embodiment of the present invention. The flowchart shown in FIG. 9 is executed every predetermined control cycle. It is assumed that the control processing in each step shown in FIG. 9 is executed by software processing and / or hardware processing by HVECU 70.

  Referring to FIG. 9, HVECU 70 obtains temperature (motor temperature) TMG2 of motor generator MG2 from temperature sensor 202 (FIG. 3) in step S01. In step S02, HVECU 70 determines whether motor temperature TMG2 is higher than a predetermined threshold value. This threshold value is a determination value for determining whether or not the motor generator MG2 is in a region where the performance is degraded. The threshold is determined in advance by determining the temperature dependence of the performance of motor generator MG2.

  When motor temperature TMG2 is equal to or lower than the threshold value (NO determination in step S02), HVECU 70 determines the engine operating point as operating point P1 that is the intersection of operating line 500 and equal power line 510 in step S10. (See FIG. 7). Accordingly, the target engine speed Ne * of the engine 22 is set to the engine speed NE1 corresponding to the operating point P1. Further, the engine torque TE1 at the operating point P1 is set to the target torque Te *. That is, HVECU 70 does not perform engine operating point change control for improving the cooling capacity of the cooling system when motor temperature TMG2 is equal to or lower than the threshold value.

  On the other hand, when motor temperature TMG2 is higher than the threshold value (when YES is determined in step S02), HVECU 70 proceeds to step S03, and engine speed NE1 corresponding to operating point P1 in FIG. 7 is a predetermined allowable upper limit speed. It is further determined whether it is lower than Nmax. When engine speed NE1 is equal to or higher than allowable upper limit speed Nmax (NO in step S03), HVECU 70 determines in step S10 that engine 22 corresponds to operating point P1 as target engine speed Ne *. The rotational speed NE1 is set.

  On the other hand, when engine speed NE1 is lower than allowable upper limit speed Nmax (when YES is determined in step S03), HVECU 70 determines that engine speed Ne is greater than engine speed NE1 by step S04. Change the engine operating point so that it is only higher. This engine operating point change control corresponds to moving the engine operating point to the high rotation side on the equal power line 510 as described with reference to FIG. The HVECU 70 increases the engine speed Ne from the engine speed NE1 to the engine speed NE2 by moving the engine operating point from the operating point P1 to the operating point P2.

  In step S05, the HVECU 70 determines whether or not the engine speed NE2 corresponding to the operating point P2 is equal to or lower than the allowable upper limit speed Nmax. When engine speed NE2 exceeds allowable upper limit speed Nmax (when NO is determined in step S05), HVECU 70 sets engine speed NE1 corresponding to operating point P1 to target speed Ne * of engine 22 in step S10. Set to.

  On the other hand, when engine speed NE2 is equal to or lower than allowable upper limit speed Nmax (when YES is determined in step S05), HVECU 70 performs motor temperature at operating point P1 corresponding to engine speed NE1 in steps S06 and S07. A rise amount ΔTMG2 (P1) and a motor temperature rise amount ΔTMG2 (P2) at the operating point P2 corresponding to the engine speed NE2 are calculated.

  First, in step S06, HVECU 70 calculates loss W1 generated in motor generator MG2 and cooling system thermal resistance R1 when engine 22 is operated at operating point P1. As described above, loss W1 can be calculated based on torque Tm of motor generator MG2. Further, the thermal resistance R1 of the cooling system can be calculated based on the relationship between the engine speed (flow rate of hydraulic oil) and the thermal resistance described with reference to FIGS. Then, HVECU 70 calculates motor temperature increase ΔTMG2 (P1) according to the above equation (8) based on calculated loss W1 of motor generator MG2 and thermal resistance R1.

  Next, in step S07, HVECU 70 calculates loss W2 generated in motor generator MG2 and cooling system thermal resistance R2 when engine 22 is operated at operating point P2. Then, HVECU 70 calculates motor temperature increase amount ΔTMG2 (P2) according to the above equation (9) based on calculated loss W2 of motor generator MG2 and thermal resistance R2.

  As for the processing of steps S06 and S07, if the correspondence between the loss W of the motor generator MG2 and the thermal resistance R with respect to the engine operating point is measured in advance through experiments or the like, a map based on the experimental results is created in advance. be able to. Thus, the motor temperature increase amount ΔTMG2 can be calculated by referring to the map based on the engine operating point.

  When the motor temperature increase amount ΔTMG2 (P1) at the operating point P1 and the motor temperature increase amount ΔTMG2 (P2) at the operating point P2 are calculated in this way, the HVECU 70 determines in step S08 these two motor temperatures. The increase amounts ΔTMG2 (P1) and ΔTMG2 (P2) are compared. When motor temperature increase amount ΔTMG2 (P2) is smaller than motor temperature increase amount ΔTMG2 (P1) (when YES is determined in step S08), HVECU 70 operates target rotational speed Ne * of engine 22 in step S09. The engine speed NE1 corresponding to the point P1 is changed to the engine speed NE2 corresponding to the operating point P2.

  On the other hand, when the motor temperature increase amount ΔTMG2 (P2) is equal to or greater than the motor temperature increase amount ΔTMG2 (P1) (NO determination in step S08), the process returns to step S04. The HVECU 70 moves the engine operating point P2 to the high speed side on the equal power line 510 so that the engine rotational speed Ne is higher by a predetermined amount than the engine rotational speed NE2 at the current operating point P2. Then, by performing the processes of steps S05 to S10, based on the comparison result between the motor temperature increase ΔTMG2 (P2) at the operating point P2 after the change and the motor temperature increase ΔTMG2 (P1) at the operating point P1. Then, the operating point (target rotational speed Ne * and target torque Te *) of the engine 22 is determined.

  Thus, according to the hybrid vehicle according to the first embodiment, the engine speed can be controlled so as to suppress the temperature increase of the motor generator while securing the required engine power. Thereby, the cooling capacity of the cooling system for cooling the motor generator can be reliably increased.

[Embodiment 2]
In the first embodiment, engine operating point change control for moving the engine operating point to the high rotation side is performed in order to find the engine speed that can suppress the motor temperature rise.

  In the second embodiment, the engine operating point change control for finding the engine speed will be further described. In the second embodiment, in addition to the engine operating point change control according to the first embodiment, some control processes are further executed. Therefore, in the second embodiment, the control process added or changed with respect to the first embodiment will be mainly described, and the description of the common parts with the first embodiment will not be repeated in principle.

  FIG. 10 is a conceptual diagram for explaining engine operating point change control according to the second embodiment.

  Referring to FIG. 10, in the engine operating point change control according to the second embodiment, HVECU 70 performs a lower rotation side than operating point P1 in addition to the process of changing the engine operating point to a higher rotational side than operating point P1. The processing for changing the engine operating point is further executed.

  In FIG. 10, an operation line 520 corresponds to an operation line (hereinafter also referred to as a WOT line) when the accelerator opening Acc is operated to a fully open position WOT (Wide Open Throttle) by the driver. P0 in the figure is the intersection of this operation line 520 and the equal power line 510 corresponding to the required power Pe * to the engine 22. The HVECU 70 changes the engine operating point from the operating point P1 to the operating point P0 while the engine 22 is outputting the engine required power Pe *. At the operating point P0, the operating point P1 is equal to the engine output power. On the other hand, the engine speed NE0 is lower than the engine speed NE1. In this case, the engine point Te is larger at the operating point P0 than at the operating point P1.

  By changing the engine operating point so that the engine speed decreases in this way, in the alignment chart of FIG. 8, the direct torque Tep transmitted to the drive shaft 32a increases as the engine torque Te increases. To do. As the direct torque Tep increases, the required drive torque Tm * for the motor generator MG2 decreases. When torque Tm of motor generator MG2 decreases, the current flowing through motor generator MG2 decreases, so that the loss generated in motor generator MG2 decreases.

  On the other hand, as described with reference to FIGS. 5 and 6, the flow rate of the hydraulic oil supplied from the oil pump 90 is reduced by changing the engine operating point so that the engine speed is reduced. As a result, the thermal resistance of the cooling system increases. That is, as the engine speed decreases, the amount of heat generated in motor generator MG2 decreases while the thermal resistance of the cooling system increases.

  Therefore, in the second embodiment, the engine speed that can suppress the motor temperature rise is determined by further executing the process of moving the engine operating point to the low speed side. The engine operating point change control according to the second embodiment will be described with reference to the flowchart of FIG.

  FIG. 11 is a flowchart illustrating engine operating point change control in the hybrid vehicle according to the second embodiment of the present invention. The flowchart shown in FIG. 11 is executed every predetermined control cycle. It is assumed that the control processing in each step shown in FIG. 9 is executed by software processing and / or hardware processing by HVECU 70.

  Referring to FIG. 11, HVECU 70 obtains temperature (motor temperature) TMG2 of motor generator MG2 from temperature sensor 202 (FIG. 3) in step S01. In step S02, HVECU 70 determines whether motor temperature TMG2 is higher than a predetermined threshold value.

  When motor temperature TMG2 is equal to or lower than the threshold value (NO determination in step S02), HVECU 70 determines the engine operating point as operating point P1 that is the intersection of operating line 500 and equal power line 510 in step S10. (See FIG. 10). Accordingly, the target engine speed Ne * of the engine 22 is set to the engine speed NE1 corresponding to the operating point P1. Further, the engine torque TE1 at the operating point P1 is set to the target torque Te *. That is, HVECU 70 does not perform engine operating point change control for improving the cooling capacity of the cooling system when motor temperature TMG2 is equal to or lower than the threshold value.

  On the other hand, when motor temperature TMG2 is higher than the threshold value (when YES is determined in step S02), HVECU 70 proceeds to step S11, and engine speed NE1 corresponding to operating point P1 in FIG. 10 is a predetermined allowable upper limit speed. It is determined whether or not equal to Nmax. Further, the HVECU 70 determines whether or not the engine torque Te corresponding to the operating point P1 exists on the WOT line 520. When engine speed NE1 is equal to allowable upper limit speed Nmax and engine torque Te is present on WOT line 520 (when YES is determined in step S11), HVECU 70 performs target rotation of engine 22 in step S10. The number Ne * is set to the engine speed NE1 corresponding to the operating point P1.

  On the other hand, when engine speed NE1 is different from allowable upper limit speed Nmax, or when engine torque Te is not present on WOT line 520 (NO in step S11), HVECU 70 performs step S12. The engine operating point is changed so that the engine speed Ne is lower than the engine speed NE1. This engine operating point change control corresponds to moving the engine operating point to the low rotation side on the equal power line 510 as described in FIG. For example, the HVECU 70 increases the engine speed Ne from the engine speed NE1 to the engine speed NE0 by moving the engine operating point from the operating point P1 to the operating point P0.

  Next, in step S13, the HVECU 70 calculates the motor temperature increase amount ΔTMG2 (P0) at the operating point P0 corresponding to the engine speed NE0. Specifically, HVECU 70 calculates loss W0 generated in motor generator MG2 and cooling system thermal resistance R0 when engine 22 is operated at operating point P0. Then, HVECU 70 calculates motor temperature increase amount ΔTMG2 (P0) based on calculated loss W0 of motor generator MG2 and thermal resistance R0. Note that the processing in step S13 is calculated by referring to a map based on the experimental results of the correspondence relationship between the loss W of the motor generator MG2 and the thermal resistance R with respect to the engine operating point, as in steps S06 and S07. Can do.

  When the motor temperature increase amount ΔTMG2 (P0) at the operating point P0 is calculated in this way, the HVECU 70 changes the engine operating point so that the engine speed Ne becomes higher than the engine speed NE1. In this engine operating point change control, the engine operating point Ne is increased from the engine rotating speed NE1 to the engine rotating speed NE2 by moving the engine operating point from the operating point P1 to the operating point P2. The HVECU 70 calculates the motor temperature increase ΔTMG2 (P1) at the operating point P1 and the motor temperature increase ΔTMG2 (P2) at the operating point P2 through steps S05 to S08 similar to FIG. The increase amounts ΔTMG2 (P1) and ΔTMG2 (P2) are compared.

  When motor temperature increase amount ΔTMG2 (P2) is smaller than motor temperature increase amount ΔTMG2 (P1) (when YES is determined in step S08), HVECU 70 further performs motor temperature increase amount ΔTMG2 calculated in step S13 in step S14. (P0) is compared with the motor temperature rise amount ΔTMG2 (P2). When motor temperature increase amount ΔTMG2 (P2) is smaller than motor temperature increase amount ΔTMG2 (P0) (when YES is determined in step S14), that is, motor temperature increase amount ΔTMG2 (P2) is motor temperature increase amount ΔTMG2 (P1). ), ΔTMG2 (P0), in step S09, the HVECU 70 changes the target engine speed Ne * of the engine 22 from the engine speed NE1 corresponding to the operating point P1 to the engine speed corresponding to the operating point P2. Change to NE2.

  On the other hand, when motor temperature increase amount ΔTMG2 (P2) is equal to or greater than motor temperature increase amount ΔTMG2 (P0) (NO determination in step S14), HVECU 70 further performs motor temperature increase amount ΔTMG2 in step S15. (P1) is compared with the motor temperature rise amount ΔTMG2 (P0). If motor temperature increase amount ΔTMG2 (P0) is smaller than motor temperature increase amount ΔTMG2 (P1) (when YES is determined in step S15), that is, motor temperature increase amount ΔTMG2 (P0) is motor temperature increase amount ΔTMG2 (P1). ), ΔTMG2 (P2), the HVECU 70 changes the target engine speed Ne * of the engine 22 from the engine speed NE1 corresponding to the operating point P1 to the engine speed corresponding to the operating point P0 in step S16. Change to NE0.

  On the other hand, when the motor temperature increase amount ΔTMG2 (P0) is equal to or greater than the motor temperature increase amount ΔTMG2 (P1) (NO in step S15), that is, the motor temperature increase amount ΔTMG2 (P1) is the motor temperature increase amount ΔTMG2 (P0). ), ΔTMG2 (P2), the HVECU 70 sets the target engine speed Ne * of the engine 22 to the engine speed NE1 corresponding to the operating point P1 in step S10.

  As described above, according to the hybrid vehicle of the second embodiment, the engine speed can be controlled so as to suppress the temperature increase of the motor generator while ensuring the required engine power. Thereby, the cooling capacity of the cooling system for cooling the motor generator can be reliably increased.

  In Embodiments 1 and 2 described above, the target engine speed is determined by performing engine operating point change control when temperature TMG2 of motor generator MG2 from temperature sensor 202 exceeds a predetermined threshold. Although the configuration is exemplified, the engine operating point change control may be performed according to the temperature TMG1 of the motor generator MG1 from the temperature sensor 202 or the detected value of the temperature of the hydraulic oil by the temperature sensor.

  Alternatively, in the first and second embodiments, heat exchange between the hydraulic oil and the cooling water is performed in the oil cooler 300, so that the engine operating point change control is performed according to the cooling water temperature THW from the temperature sensor 204 (FIG. 3). It is good also as a structure to perform.

  Alternatively, in the cooling system of FIG. 3, the vehicle speed or the traveling wind of the hybrid vehicle 20 is based on the radiator 290 cooling the cooling water using the air cooling by the traveling wind generated as the hybrid vehicle 20 travels. It is also possible to adopt a configuration in which engine operating point change control is performed in accordance with the wind speed.

  FIG. 12 shows the relationship between the flow rate of hydraulic oil supplied from the oil pump 90 and the thermal resistance. In FIG. 12, when the wind speed of the traveling wind is zero, when the wind speed is V1 (> 0) [m / min], and when the wind speed is V2 (> V1) [m / min], the flow rate of the hydraulic oil and the heat of the cooling system The relationship with resistance is shown.

  As apparent from FIG. 12, the thermal resistance of the cooling system decreases as the flow rate of hydraulic oil increases, and the thermal resistance for the same hydraulic fluid flow rate increases as the traveling wind speed of the hybrid vehicle 20 increases. The amount of decrease is increasing. That is, the higher the wind speed of the traveling wind, the greater the effect of reducing the thermal resistance due to the increase in the hydraulic oil flow rate. Therefore, if the engine operating point change control according to the present invention is executed when the wind speed of the traveling wind is high, the cooling capacity of the cooling system can be effectively increased.

  Since the relationship shown in FIG. 13 is established between the wind speed of the traveling wind and the vehicle speed of the hybrid vehicle 20, the engine operation is actually performed according to the vehicle speed detected by the vehicle speed sensor 88 (FIG. 1). It is possible to perform point change control. For example, the engine operating point change control may be executed when the vehicle speed from the vehicle speed sensor 88 exceeds a threshold value Vth corresponding to the wind speed V2 [m / min] of the traveling wind in FIG.

  FIG. 14 is a flowchart illustrating a modification of the engine operating point change control in the hybrid vehicle according to the embodiment of the present invention. Referring to FIG. 14, in the present modification, HVECU 70 executes the processes of steps S21 and S22 instead of steps S01 and S02 of FIG.

  The HVECU 70 acquires the vehicle speed of the hybrid vehicle 20 from the vehicle speed sensor 88 in step S21. Then, the HVECU 70 determines whether or not the vehicle speed is higher than a predetermined threshold value Vth in step S22.

  When the vehicle speed is equal to or lower than the threshold value Vth (when NO is determined in step S22), the HVECU 70 determines an engine operating point as an operating point P1 that is an intersection of the operating line 500 and the equal power line 510 in step S10. (See FIG. 7). Accordingly, the target engine speed Ne * of the engine 22 is set to the engine speed NE1 corresponding to the operating point P1. That is, the HVECU 70 does not perform engine operating point change control for improving the cooling capacity of the cooling system when the vehicle speed is equal to or lower than the threshold value.

  On the other hand, when the vehicle speed is higher than the threshold value (when YES is determined in step S22), the HVECU 70 performs engine operating point change control for moving the engine operating point to the high rotation side through steps S03 to S10 similar to FIG. By carrying out, the engine speed which can suppress a motor temperature rise is set to the target engine speed Ne *.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  20 hybrid vehicle, 22 engine, 23 crank angle sensor, 24 engine ECU, 26 crankshaft, 28 torsional damper, 30 power split mechanism, 31 sun gear, 31a sun gear shaft, 32 ring gear, 32a ring gear shaft (drive shaft), 33 pinion gear , 34 carrier, 37 gear mechanism, 38 differential gear, 39a, 39b drive wheel, 40 converter, 41, 42 inverter, 43, 44 rotational position detection sensor, 45 motor ECU, 48 output shaft, 50 battery, 52 battery ECU, 54 Power line, 60 transmission, 61 case, 65 sun gear, 66 ring gear, 67 pinion gear, 70 HVECU, 80 ignition switch, 81 shift lever, 82 shift position sensor, 8 Accelerator pedal, 84 Accelerator pedal position sensor, 85 Brake pedal, 86 Brake pedal position sensor, 88 Vehicle speed sensor, 90 Oil pump, 180 Voltage sensor, 200 Transaxle, 202, 204 Temperature sensor, 206 Case, 210, 220, 230, 240, 250 Refrigerant passage, 260 Water pump, 270 Reservoir tank, 290 Radiator, 300 Oil cooler, 302 Water passage, 320-340 Oil passage, 350 Discharge port, MG1, MG2 Motor generator.

Claims (6)

An internal combustion engine;
An electric motor configured to output torque to a drive shaft mechanically coupled to the drive wheels;
A power transmission device for mechanically transmitting torque originating from the output of the internal combustion engine to the drive shaft;
A cooling device for cooling the electric motor;
A control device for controlling the output of the internal combustion engine and the electric motor so that the required driving force in the entire vehicle acts on the drive shaft;
The cooling device includes a mechanical pump configured to supply the electric motor with a refrigerant having a flow rate corresponding to the rotational speed of the internal combustion engine by being driven to rotate in accordance with the rotation of the internal combustion engine.
The control device includes a loss of the electric motor and a thermal resistance of the cooling device when the internal combustion engine operates at a first rotational speed for securing the output required for the internal combustion engine of the required driving force. Than the amount of temperature increase of the electric motor based on the above , based on the loss of the electric motor and the thermal resistance of the cooling device when the internal combustion engine operates at the second rotational speed while maintaining the output of the internal combustion engine A hybrid vehicle that changes a target rotational speed of the internal combustion engine from the first rotational speed to the second rotational speed when a temperature increase amount of the electric motor becomes small.   The control device is configured to execute an operating point change control for changing an operating point of the internal combustion engine on an equal power line for securing an output required for the internal combustion engine, and the electric motor for each operating point The temperature increase amount of the electric motor based on the loss of the motor and the thermal resistance of the cooling device, and the target rotation of the internal combustion engine based on the result of comparing the temperature increase amount of the electric motor calculated for each operating point The hybrid vehicle according to claim 1, wherein the number is determined.   The control device performs the operating point change control so as to move the operating point of the internal combustion engine from the intersection of the operating line capable of operating the internal combustion engine with high efficiency and the equal power line to the high rotation side. The hybrid vehicle according to claim 2, which is executed.   The control device moves the operating point of the internal combustion engine to a low rotation side and a high rotation side from an intersection of an operation line capable of operating the internal combustion engine with high efficiency and the equal power line, respectively. The hybrid vehicle according to claim 2, wherein operating point change control is executed.   The said control apparatus performs the said operating point change control according to either the temperature of the said electric motor, the temperature of the said refrigerant | coolant, the vehicle speed of the said hybrid vehicle, and the wind speed of the driving | running | working wind of the said hybrid vehicle. 5. The hybrid vehicle according to any one of 4. A generator for generating electric power by power from the internal combustion engine;
The power transmission device includes a three-shaft power split device,
The power split device is mechanically connected to three shafts of the output shaft of the internal combustion engine, the output shaft of the generator, and the drive shaft, and power is input / output to / from any two of the three shafts. The hybrid vehicle according to any one of claims 1 to 5, wherein the hybrid vehicle is configured to input and output power to the remaining one shaft on the basis of the above.

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