Hybrid vehicle

Abstract

To improve running performance in battery-less running, while suppressing engine stall.SOLUTION: A hybrid vehicle is equipped with: an engine; a first motor generator; a second motor generator connected to a driving shaft; a power division mechanism that can transmit power among the engine, the first motor generator and the driving shaft; batteries connected to the first motor generator and the second motor generator; a position sensor that detects a current position; a storing part that stores map data including information on altitudes; and a control part that obtains an altitude while referring to the map data on the basis of the current position detected by the position sensor, determines minimum torque of the first motor generator on the basis of the obtained altitude, and performs control so that torque of the first motor generator does not fall below the minimum torque, in battery-less running in which the batteries are disconnected from the first motor generator and the second motor generator.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to the technical field of hybrid vehicles. [Background technology]

[0002] 2. Description of the Related Art Conventionally, in a hybrid vehicle having an engine and two motor generators connected by a power split mechanism, it is possible to perform so-called batteryless running in which the vehicle runs with the battery disconnected.

[0003] In such hybrid vehicles, when running without a battery, the torque output from the engine is used to generate electricity in one motor generator, and the generated electricity is used to drive the other motor generator to run the vehicle. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-111855 A Summary of the Invention [Problem to be solved by the invention]

[0005] In a hybrid vehicle as described above, if one of the motor generators generates a torque for generating electricity that is greater than the torque output from the engine, the engine will stall. Therefore, it is desirable to improve the running performance during battery-less running while suppressing engine stall.

[0006] The present invention has been made in consideration of the above circumstances, and has an object to improve driving performance during battery-less driving while suppressing engine stall. [Means for solving the problem]

[0007] A hybrid vehicle according to one embodiment of the present invention comprises an engine, a first motor generator, a second motor generator connected to a drive shaft, a power split mechanism capable of transmitting power between the engine, the first motor generator, and the drive shaft, a battery connected to the first motor generator and the second motor generator, a position sensor that detects a current position, a memory unit that stores map data including altitude information, and a control unit that, during battery-less driving in which the battery is disconnected from the first motor generator and the second motor generator, obtains altitude by referring to the map data based on the current position detected by the position sensor, determines a minimum torque of the first motor generator based on the obtained altitude, and controls the torque of the first motor generator so that it does not become below the minimum torque. Effect of the Invention

[0008] According to the present invention, it is possible to improve the running performance during battery-less running while suppressing engine stall. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing the configuration of a hybrid vehicle. [Diagram 2] FIG. 4 is a collinear diagram during battery-less running. [Diagram 3] FIG. 2 is a diagram showing an example of map data indicating altitude. [Figure 4] FIG. 4 is a diagram showing a load factor map. [Diagram 5] FIG. 13 is a graph showing minimum torque versus air pressure. [Figure 6] FIG. 4 is a diagram showing transitions of MG1 torque, MG2 torque, and engine torque during battery-less running. [Figure 7] FIG. 4 is a diagram showing a control flow during battery-less running. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] <1. Hybrid vehicle configuration> Fig. 1 is a diagram showing the configuration of a hybrid vehicle 1. In Fig. 1, electrical connections are indicated by dashed lines, and signal flows are indicated by broken lines. As shown in Fig. 1, a hybrid vehicle 1 includes an engine 2, a first motor generator 3, a second motor generator 4, a power split mechanism 5, a first inverter 6, a second inverter 7, a battery 8, and a relay 9. In Fig. 1, the first motor generator is represented as "MG1" and the second motor generator is represented as "MG2." The hybrid vehicle 1 also includes an engine ECU (Electronic Control Unit) 21, a motor ECU 22, and a hybrid vehicle electronic control unit (HVECU) 23 as control units. The hybrid vehicle 1 also includes a plurality of sensor units 24 for detecting the state of the hybrid vehicle 1 and the surrounding conditions, and a storage unit 25 for storing various information including map data 25a.

[0011] The engine 2 is, for example, a horizontally opposed engine in which a pair of cylinder groups are arranged horizontally opposite each other in the left-right direction across a crankshaft 11. The engine 2 reciprocates pistons using combustion pressure obtained by burning a mixture of gasoline and air in the cylinders. The engine 2 obtains power by rotating the crankshaft 11, which is connected to the pistons via connecting rods. The crankshaft 11 is connected to the carrier 5d of the power split mechanism 5, and transmits the power obtained by the engine 2 to the carrier 5d. The engine 2 may be an in-line engine, a V-engine, etc. The engine 2 may be a diesel engine.

[0012] The first motor generator 3 is, for example, a three-phase AC motor, and is connected to a battery 8 via a first inverter 6. A rotating shaft 12 of the first motor generator 3 is connected to a sun gear 5a of the power split mechanism 5. The first motor generator 3 is capable of generating electricity using power input from the engine 2 via the power split mechanism 5. The power generated by the first motor generator 3 is supplied to the battery 8 via the first inverter 6. This charges the battery 8. The first motor generator 3 can also be driven using the power of the battery 8 to output power.

[0013] The second motor generator 4 is, for example, a three-phase AC motor, and is connected to a battery 8 via a second inverter 7. The second motor generator 4 is connected to a drive shaft 13. The second motor generator 4 is driven using the power of the battery 8, and outputs power that rotates the drive wheels 15. The second motor generator 4 is also capable of regenerating power by using the kinetic energy of the drive wheels 15 when the hybrid vehicle 1 is decelerating. The power generated by the second motor generator 4 is supplied to the battery 8 via the second inverter 7. This charges the battery 8.

[0014] The power split mechanism 5 is, for example, a planetary gear mechanism including a sun gear 5a, a planetary gear 5b, a ring gear 5c, and a carrier 5d. The sun gear 5 a is connected to a rotating shaft 12 of the first motor generator 3 . The ring gear 5c is disposed radially outward of the sun gear 5a. The central axis of the ring gear 5c is disposed coaxially with the sun gear 5a. The ring gear 5c is connected to a drive shaft 13. The drive shaft 13 is connected to drive wheels 15 via a differential gear 14. A plurality of planetary gears 5b are disposed between the sun gear 5a and the ring gear 5c, and are meshed with the sun gear 5a and the ring gear 5c. The carrier 5d rotatably supports the plurality of planetary gears 5b. The carrier 5d is connected to the crankshaft 11 of the engine 2.

[0015] A portion of the power of the engine 2 is transmitted to the first motor generator 3 via the power split mechanism 5. The remainder of the power of the engine 2 is transmitted to the drive wheels 15 via the power split mechanism 5. In other words, the power split mechanism 5 splits the power of the engine 2 into power that rotates the first motor generator 3 and power that rotates the drive wheels 15.

[0016] The first inverter 6 converts the DC current supplied from the battery 8 into a three-phase AC current and supplies it to the first motor generator 3. When the first motor generator 3 generates power, the first inverter 6 converts the AC current supplied from the first motor generator 3 into a DC current and supplies it to the battery 8.

[0017] The second inverter 7 converts the DC current supplied from the battery 8 into a three-phase AC current and supplies it to the second motor generator 4. When the second motor generator 4 generates power, the second inverter 7 converts the AC current supplied from the second motor generator 4 into a DC current and supplies it to the battery 8.

[0018] The battery 8 is a so-called high-voltage secondary battery, and stores power (electricity) to be supplied to the first motor generator 3 and the second motor generator 4.

[0019] A relay 9 is provided between the first inverter 6 and the battery 8 and between the second inverter 7 and the battery 8. The relay 9 is turned on and off by the HVECU 23 to electrically connect and disconnect the first inverter 6 and the battery 8 and to electrically connect and disconnect the second inverter 7 and the battery 8.

[0020] When the relay 9 electrically disconnects the first inverter 6 and the second inverter 7 from the battery 8, the second motor generator 4 can be driven by inputting the power generated by the first motor generator 3 via the first inverter 6 and the second inverter 7.

[0021] The engine ECU 21 is configured as a computer including a CPU, a RAM, and a ROM, and controls the operation of the engine 2. The engine ECU 21 is connected to the HVECU 23 so as to be able to communicate with each other.

[0022] The motor ECU 22 is configured as a computer including a CPU, a RAM, and a ROM. The motor ECU 22 controls the operation of the first inverter 6 and the second inverter 7 to drive and control the first motor generator 3 and the second motor generator 4. The motor ECU 22 is communicatively connected to the HVECU 23 .

[0023] The HVECU 23 is configured as a computer including a CPU, a RAM, and a ROM. The HVECU 23 performs overall control of the hybrid vehicle 1. The HVECU 23 calculates various values ​​related to the driving of the hybrid vehicle 1 based on, for example, various information detected by the sensor unit 24. The HVECU 23 then transmits the calculated values ​​to the engine ECU 21 and the motor ECU 22, thereby appropriately driving the engine 2, the first motor generator 3, and the second motor generator 4. In other words, it can be said that the HVECU 23 functions as a control unit that controls the driving of the engine 2, the first motor generator 3, and the second motor generator 4.

[0024] The sensor unit 24 includes, for example, an accelerator sensor 24a, a vehicle speed sensor 24b, and a position sensor 24c. Values ​​detected by the sensor unit 24 are transmitted to the engine ECU 21, the motor ECU 22, and the HVECU 23 as appropriate. The accelerator sensor 24a detects the amount of depression of an accelerator pedal (not shown). The vehicle speed sensor 24b detects the speed of the hybrid vehicle 1 (vehicle speed). The position sensor 24c detects the current position (latitude, longitude) of the hybrid vehicle 1 based on signals emitted from a plurality of GNSS (Global Navigation Satellite System) satellites.

[0025] The storage unit 25 is configured with, for example, a non-volatile memory, and stores map data 25a. The map data 25a includes altitude information, which will be described in detail later.

[0026] The hybrid vehicle 1 is capable of executing navigation processing such as reading out a map including the current position detected by the position sensor 24c from the map data 25a and displaying it on a display unit (not shown) and providing route guidance to a specified destination.

[0027] <2. Battery-less driving> In the hybrid vehicle 1, if an abnormality occurs in the battery 8, the first motor generator 3 and the second motor generator 4 are electrically disconnected from the battery 8, and the second motor generator 4 is driven by electric power generated by the first motor generator 3, thereby enabling batteryless running. Batteryless running will be described below. An abnormality in the battery 8 is detected by a battery ECU (not shown) based on the voltage, current, etc. of the battery 8, and notified to the HVECU 23.

[0028] When an abnormality in the battery 8 is detected, the HVECU 23 controls the relay 9 to cut off the connection between the first inverter 6 and the second inverter 7 and the battery 8. This electrically separates the first motor generator 3 and the second motor generator 4 from the battery 8.

[0029] Thereafter, the HVECU 23 refers to a required drive torque map based on the accelerator opening detected by the accelerator sensor 24a and the vehicle speed detected by the vehicle speed sensor 24b to calculate a required drive torque Tr* to be output to the drive shaft 13. The required drive torque map is a map in which the required drive torque Tr* is associated with the accelerator opening and the vehicle speed.

[0030] Here, in hybrid vehicle 1, engine torque Te output from engine 2 is split to sun gear 5a and ring gear 5c by power split mechanism 5. Then, first motor generator 3 generates electricity by the engine torque split to sun gear 5a. Also, engine torque split to ring gear 5c (hereinafter referred to as engine direct torque Ted) is input to drive shaft 13. Torque output from the second motor generator 4 (hereinafter referred to as MG2 torque Tmg2) is also input to the drive shaft 13. Therefore, the torque input to the drive shaft 13 is the sum of the engine direct torque Ted and the MG2 torque Tmg2.

[0031] In addition, in battery-less running, the second motor generator 4 is driven by the electric power generated by the first motor generator 3. Therefore, the MG1 generation power, which is the electric power generated by the first motor generator 3, and the MG2 drive power, which is the electric power consumed by the second motor generator 4, are equal to each other.

[0032] Therefore, the HVECU 23 calculates the target MG1 torque Tmg1* and the target MG2 torque Tmg2* so that the sum of the engine direct torque Ted and the MG2 torque Tmg2 becomes the required drive torque Tr* and the MG1 power generation power is equal to the MG2 drive power. The target MG1 torque Tmg1* is a target value of the load torque when the first motor generator 3 generates power (hereinafter, MG1 torque Tmg1). Moreover, the target MG2 torque Tmg2* is a target value of the MG2 torque Tmg2.

[0033] After calculating the target MG1 torque Tmg1* and the target MG2 torque Tmg2*, the HVECU 23 transmits these to the motor ECU 22.

[0034] The motor ECU 22 controls the first inverter 6 so that the first motor generator 3 generates power at the target MG1 torque Tmg1*. The motor ECU 22 also controls the second inverter 7 so that the second motor generator 4 is driven at the target MG2 torque Tmg2*. At this time, the motor ECU 22 controls the second motor generator 4 to be driven by the power generated by the first motor generator 3.

[0035] Furthermore, after calculating the target MG1 torque Tmg1*, the HVECU 23 notifies the engine ECU 21 of the target MG1 torque Tmg1*.

[0036] The engine ECU 21 calculates the target engine torque Te* such that a torque equivalent to the notified target MG1 torque Tmg1* can be applied to the sun gear 5a. Then, the engine ECU 21 determines a target rotation speed Ne* for outputting the target engine torque Te* from the engine 2. Here, for example, the target rotation speed Ne* is determined using an operation line (for example, a fuel efficiency optimum operation line) that indicates the relationship between the rotation speed and engine torque of the engine 2 that allows the target engine torque Te* to be efficiently output from the engine 2.

[0037] Then, the engine ECU 21 performs feedback control of the engine 2 (specifically, the throttle valve opening, the ignition timing, the fuel injection amount, etc.) so that the engine 2 is driven at the target engine torque Te* and the target rotation speed Ne*.

[0038] FIG. 2 is a collinear diagram during battery-less running. As shown in FIG. 2, during battery-less running (moving forward), the engine 2 rotates in the forward direction. The first motor generator 3 rotates in the forward direction and generates an MG1 torque Tmg1. The second motor generator 4 rotates in the forward direction and generates an MG2 torque Tmg2. At this time, as can be seen from FIG. 2, the MG1 torque Tmg1 is a negative value. Also, the MG2 torque Tmg2 is a positive value.

[0039] The drive torque Tr can be expressed as the sum of the engine direct torque Ted obtained by dividing the engine torque Te output from the engine 2 and the MG2 torque Tmg2.

[0040] It is known that the output of the engine 2 decreases as the atmospheric pressure decreases. Therefore, when the engine torque Te decreases, for example, when the hybrid vehicle 1 runs at high altitude, if the absolute value of the torque transmitted to the sun gear 5a out of the engine torque Te falls below the absolute value of the MG1 torque Tmg1 of the first motor generator 3, the engine 2 will stall.

[0041] On the other hand, if the MG1 torque Tmg1 is set to match the engine torque Te when the hybrid vehicle 1 is traveling on high ground, the MG1 torque Tmg1 when the hybrid vehicle 1 is traveling on flat ground will be the same as when the hybrid vehicle 1 is traveling on high ground. Therefore, even when the hybrid vehicle 1 is traveling on flat ground, the amount of power generated by the first motor generator 3 decreases and the MG2 torque Tmg2 of the second motor generator 4 also decreases, resulting in a deterioration in driving performance on flat ground.

[0042] Therefore, during battery-less running, the HVECU 23 refers to the map data 25a from the current position detected by the position sensor 24c to obtain the altitude of the current position, and estimates the atmospheric pressure of the current position based on the obtained altitude of the current position. Then, the HVECU 23 determines the minimum torque Tmin of the first motor generator 3 based on the estimated atmospheric pressure.

[0043] The minimum torque Tmin indicates the minimum value of the load torque of the first motor generator 3 that can be applied as a load to the engine 2. As described above, since the MG1 torque Tmg1 is a negative value, the minimum torque Tmin is also a negative value.

[0044] Fig. 3 is a diagram showing an example of map data 25a indicating altitude. As shown in Fig. 3, in the map data 25a, altitude information (e.g., 100 m, 200 m, 300 m) is associated with each position (latitude, longitude) on the map.

[0045] The HVECU 23 refers to the map data 25a based on the current position detected by the position sensor 24c, and acquires the altitude of the current position.

[0046] Then, the HVECU 23 calculates the atmospheric pressure at the current location based on the acquired altitude of the current location. Note that since the relationship between altitude and atmospheric pressure is known, the atmospheric pressure at the current location is calculated using that relationship.

[0047] 4 is a diagram showing a load factor map. The load factor map is stored in the ROM of the HVECU 23. As shown in Fig. 4, the load factor map associates the load factor with the atmospheric pressure. According to the load factor map, the load factor is set to be smaller as the atmospheric pressure becomes lower. The HVECU 23 determines the load factor by referring to a load factor map based on the estimated atmospheric pressure at the current location. If the estimated air pressure is a value between the air pressures shown in the load factor map, the load factor can be determined by interpolation using the air pressures shown in the load factor map.

[0048] When the HVECU 23 determines the load factor, the HVECU 23 multiplies a predetermined minimum load torque by the load factor to calculate a minimum torque Tmin according to the air pressure at the current position. The minimum load torque is the minimum value (maximum value in absolute value) of the load torque that can be generated by the first motor generator 3, and is a fixed value determined in advance based on the specifications of the engine 2 and the first motor generator 3, the gear ratio of the power split mechanism 5, etc.

[0049] Fig. 5 is a diagram showing the minimum torque Tmin versus atmospheric pressure. As shown in Fig. 5, the lower the atmospheric pressure, the smaller the load factor, and therefore the lower the atmospheric pressure, the larger the minimum torque Tmin (the smaller the absolute value of the minimum torque Tmin).

[0050] Then, when the HVECU 23 calculates the minimum torque Tmin, the HVECU 23 compares the minimum torque Tmin with the target MG1 torque Tmg1*. More specifically, the HVECU 23 determines whether the target MG1 torque Tmg1* is less than the minimum torque Tmin. Incidentally, since the target MG1 torque Tmg1* and the minimum torque Tmin are both negative values, here, it is determined whether the absolute value of the target MG1 torque Tmg1* is greater than the absolute value of the minimum torque Tmin.

[0051] As a result, when the target MG1 torque Tmg1* is equal to or greater than the minimum torque Tmin, that is, when the absolute value of the target MG1 torque Tmg1* is equal to or less than the absolute value of the minimum torque Tmin, the HVECU 23 maintains the target MG1 torque Tmg1* as is.

[0052] On the other hand, when the target MG1 torque Tmg1* is less than the minimum torque Tmin, that is, when the absolute value of the target MG1 torque Tmg1* is greater than the absolute value of the minimum torque Tmin, the HVECU 23 changes the target MG1 torque Tmg1* to the minimum torque Tmin.

[0053] This makes it possible to prevent the target MG1 torque Tmg1* from becoming a value smaller than the minimum torque Tmin (a value larger in absolute value).

[0054] When the target MG1 torque Tmg1* is changed to the minimum torque Tmin, the HVECU23 calculates the target MG2 torque Tmg2* when driving with MG2 driving power that is equal to the MG1 generating power when the first motor generator 3 generates power with the converted target MG1 torque Tmg1*.

[0055] Then, after calculating the converted target MG1 torque Tmg1* and target MG2 torque Tmg2*, the HVECU 23 transmits these to the motor ECU 22.

[0056] Further, the HVECU 23 notifies the converted target MG1 torque Tmg1* to the engine ECU 21. The engine ECU 21 determines a target engine torque Te* and a target rotation speed Ne* at which the engine 2 does not stall, based on the notified target MG1 torque Tmg1*. Then, the engine ECU 21 controls the engine 2 so that it is driven at the target engine torque Te* and the target rotation speed Ne*.

[0057] FIG. 6 is a diagram showing transitions of the MG1 torque Tmg1, the MG2 torque Tmg2, and the engine torque Te during battery-less running.

[0058] As shown in Fig. 6, assume that the accelerator pedal is operated at time T1 to increase the accelerator opening degree. Then, the required drive torque Tr* gradually increases according to the accelerator opening degree and the vehicle speed, so that the MG2 torque Tmg2 transmitted to the drive wheels 15 increases and the MG1 torque Tmg1 for generating the electric power supplied to the second motor generator 4 decreases (its absolute value increases). Then, when the MG1 torque Tmg1 decreases (the absolute value increases), the engine torque Te of the engine 2 also increases accordingly.

[0059] Thereafter, when the MG1 torque Tmg1 reaches the minimum torque Tmin, the MG1 torque Tmg1 is maintained at the minimum torque Tmin. Furthermore, since the power generated by the first motor generator 3 is also maintained, the MG2 torque Tmg2 of the second motor generator 4 driven by the generated power is also maintained at a constant value. Furthermore, since the engine 2 is drive-controlled so as not to stall at the MG1 torque Tmg1, the engine torque Te is also maintained at a constant value.

[0060] 7 is a diagram showing a control flow during battery-less running. When battery-less running is started, in step S1, the HVECU 23 opens the relay 9 to electrically disconnect the first motor generator 3 and the second motor generator 4 from the battery 8.

[0061] In step S2, the HVECU 23 acquires the current position detected by the position sensor 24c. In step S3, the HVECU 23 acquires the altitude of the current position by referring to the map data 25a based on the current position acquired in step S2. In step S4, the HVECU 23 estimates the air pressure of the current position based on the acquired altitude.

[0062] In step S5, the HVECU 23 determines the load factor by referring to a load factor map based on the estimated air pressure.

[0063] After that, in step S6, the HVECU 23 calculates the minimum torque Tmin based on the determined load factor and minimum load torque.

[0064] Furthermore, in step S7, the HVECU 23 calculates a required driving torque Tr* by referring to a required driving torque map based on the accelerator opening detected by the accelerator sensor 24a and the vehicle speed detected by the vehicle speed sensor 24b.

[0065] In step S8, the HVECU 23 calculates a target MG1 torque Tmg1* and a target MG2 torque Tmg2* that satisfy the calculated required drive torque Tr*.

[0066] In step S9, the HVECU 23 determines whether the target MG1 torque Tmg1* is less than the minimum torque Tmin. As a result, if the target MG1 torque Tmg1* is less than the minimum torque Tmin (Yes in step S9), the HVECU 23 changes the target MG1 torque Tmg1* to the minimum torque Tmin in step S10. In addition, in step S11, the HVECU 23 calculates a target MG2 torque Tmg2* for outputting MG2 driving power equal to the MG1 power generation power generated by the first motor generator 3 with the converted target MG1 torque Tmg1*, and proceeds to step S12.

[0067] On the other hand, if the target MG1 torque Tmg1* is not less than the minimum torque Tmin (No in step S9), the HVECU 23 maintains the target MG1 torque Tmg1* as is, and moves the process to step S12.

[0068] In step S12, the HVECU 23 transmits the target MG1 torque Tmg1* to the engine ECU 21. The engine ECU 21 determines a target engine torque Te* and a target rotation speed Ne* at which the engine 2 does not stall, based on the notified target MG1 torque Tmg1*. Then, the engine ECU 21 controls the engine 2 so that the engine 2 is driven at the target engine torque Te* and the target rotation speed Ne*.

[0069] In step S13, the HVECU 23 transmits the target MG1 torque Tmg1* and the target MG2 torque Tmg2* to the motor ECU 22, and ends the process. The motor ECU 22 controls the first inverter 6 so that the first motor generator 3 is driven at the target MG1 torque Tmg1*. The motor ECU 22 also controls the second inverter 7 so that the second motor generator 4 is driven at the target MG2 torque Tmg2*. At this time, the motor ECU 22 controls the second motor generator 4 to be driven by the electric power generated by the first motor generator 3.

[0070] <2. Modifications> Although the embodiment of the present invention has been described above, the present invention is not limited to the above-mentioned specific examples and can adopt various configurations. For example, in the above embodiment, the engine ECU 21, the motor ECU 22, and the HVECU 23 are provided as the control unit, but the HVECU 23 may function as the engine ECU 21 and the motor ECU 22, and only the HVECU 23 may be provided. Also, the engine ECU 21, the motor ECU 22, and the HVECU 23 may each be configured with a plurality of computers. Furthermore, the above-mentioned processes may be executed separately by the engine ECU 21, the motor ECU 22, and the HVECU 23.

[0071] In the above embodiment, the HVECU 23 estimates the atmospheric pressure based on the altitude of the current position. However, if information on the weather of the current position can be acquired, the HVECU 23 may estimate the atmospheric pressure based on the altitude and weather of the current position. In this case, for example, if the weather is sunny, the coefficient is set to 1, and if the weather is cloudy or rainy, the coefficient is set to 0.98, and the atmospheric pressure of the current position may be estimated by multiplying the coefficient by the atmospheric pressure calculated based on the altitude. Note that the weather of the current position can be acquired, for example, via a network.

[0072] In the above embodiment, the HVECU 23 estimates the air pressure based on the altitude of the current position. However, if the hybrid vehicle 1 is equipped with an air pressure sensor that detects tire air pressure, the HVECU 23 may estimate the air pressure at the current position based on the tire air pressure detected on flat ground and the tire air pressure at the current position. The HVECU 23 may also interpolate the air pressure estimated based on the altitude of the current position with the air pressure estimated based on the tire air pressure.

[0073] In the above embodiment, the HVECU 23 estimates the air pressure based on the altitude of the current position. However, the HVECU 23 may estimate the minimum torque Tmin using the air pressure detected by the intake pressure sensor when the engine 2 is stopped.

[0074] In the above embodiment, the HVECU 23 estimates the air pressure based on the altitude of the current position, and determines the minimum torque Tmin based on the estimated air pressure. However, the HVECU 23 may directly determine the minimum torque Tmin based on the altitude of the current position. In this case, the calculation for estimating the air pressure from the altitude and the calculation for determining the minimum torque Tmin from the air pressure may be performed at the same time.

[0075] <3. Summary of the embodiment> As described above, the hybrid vehicle 1 of the embodiment includes the engine 2, the first motor generator 3, the second motor generator 4 connected to the drive shaft 13, a power split mechanism 5 capable of transmitting power between the engine 2, the first motor generator 3, and the drive shaft 13, a battery 8 connected to the first motor generator 3 and the second motor generator 4, a position sensor 24c that detects a current position, a memory unit 25 that stores map data 25a including altitude information, and a control unit (HVECU 23) that, during battery-less running in which the battery 8 is disconnected from the first motor generator 3 and the second motor generator 4, acquires the altitude by referring to the map data 25a based on the current position detected by the position sensor 24c, determines a minimum torque Tmin of the first motor generator 3 based on the acquired altitude, and controls the torque of the first motor generator 3 so that it does not become less than the minimum torque Tmin. As a result, the MG1 torque Tmg1 of the first motor generator 3 is controlled so as not to fall below the minimum torque Tmin determined according to the altitude of the location where the hybrid vehicle 1 is traveling. Therefore, even when the hybrid vehicle 1 is traveling at high altitude and the torque of the engine 2 is reduced, it is possible to reduce engine stall caused by the MG1 torque Tmg1 of the first motor generator 3. Furthermore, compared to a case where the minimum torque Tmin is uniformly determined in accordance with the hybrid vehicle 1 traveling on high ground, the minimum torque Tmin can be set to a small value (large in absolute terms) when the hybrid vehicle 1 travels on flat ground. This makes it possible to increase the amount of power generated by the first motor generator 3 and also to increase the drive torque (MG2 torque Tmg2) of the second motor generator 4 when the hybrid vehicle 1 travels on flat ground, thereby improving driving performance. In this manner, in the hybrid vehicle 1, an appropriate MG1 torque Tmg1 can be set according to the air pressure at which the hybrid vehicle 1 is running. Thus, the hybrid vehicle 1 can improve the running performance during battery-less running while suppressing engine stall.

[0076] The control unit (HVECU 23) acquires the altitude by referring to the map data 25a based on the current position detected by the position sensor 24c, estimates the air pressure based on the acquired altitude, and determines the minimum torque Tmin based on the estimated air pressure. As a result, in the hybrid vehicle 1, the atmospheric pressure can be accurately estimated from the altitude of the current position acquired by referring to the map data 25a, and therefore the minimum torque Tmin can be accurately calculated.

[0077] A load factor map is provided which correlates the air pressure with the load factor of the first motor generator 3 during battery-less running, and the control unit determines the load factor by referring to the load factor map based on the estimated air pressure, and determines the minimum torque Tmin based on the determined load factor. Thus, the hybrid vehicle 1 can easily determine the minimum torque Tmin by multiplying the load factor, which is determined by referring to the load factor map, by the minimum load torque, which is a constant value.

[0078] The load factor map is set so that the lower the atmospheric pressure, the smaller the load factor value that is determined. This allows the hybrid vehicle 1 to easily and accurately set an appropriate MG1 torque Tmg1 according to the air pressure at which the hybrid vehicle 1 is running.

[0079] The control unit (HVECU 23) acquires weather information for the current location, and estimates the atmospheric pressure for the current location based on the acquired altitude and weather information. This allows the hybrid vehicle 1 to estimate the atmospheric pressure taking the weather into account, thereby making it possible to estimate the atmospheric pressure with greater accuracy. [Explanation of symbols]

[0080] 1. Hybrid vehicles 2 Engine 3. First motor generator 4. Second motor generator 5 Power split mechanism 8 Battery 13 Drive shaft 21 Engine ECU 22 Motor ECU 23 HVECU 24c Position Sensor 25a Map data

Claims

1. The engine, A first motor generator; a second motor generator connected to a drive shaft; a power split mechanism capable of transmitting power among the engine, the first motor generator, and the drive shaft; a battery connected to the first motor generator and the second motor generator; A position sensor for detecting a current position; A storage unit that stores map data including altitude information; a control unit that, during battery-less running in which the battery is disconnected from the first motor generator and the second motor generator, acquires altitude by referring to the map data based on a current position detected by the position sensor, determines a minimum torque of the first motor generator based on the acquired altitude, and controls the torque of the first motor generator so that it does not become equal to or lower than the minimum torque; A hybrid vehicle equipped with

2. The control unit refers to the map data to obtain an altitude based on a current position detected by the position sensor, estimates an air pressure based on the obtained altitude, and determines the minimum torque based on the estimated air pressure. The hybrid vehicle according to claim 1.

3. a load factor map in which the air pressure is associated with the load factor of the first motor generator during the battery-less running; The control unit determines the load factor by referring to the load factor map based on the estimated air pressure, and determines the minimum torque based on the determined load factor.

3. The hybrid vehicle according to claim 2.

4. The load factor map is set so that the lower the atmospheric pressure, the smaller the value determined as the load factor.

4. The hybrid vehicle according to claim 3.

5. The control unit acquires weather information for a current location and estimates atmospheric pressure based on the acquired altitude and weather information.

3. The hybrid vehicle according to claim 2.

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