Hybrid vehicle control device

Abstract

To reduce a power loss during an automatic operation in a travel-on-motor, thus enabling the travel-on-motor for as long as possible.SOLUTION: A control device has threshold setup means (steps S3, S4) that performs: setting a threshold on required drive power for determining switching from a second BEV mode where a clutch is released to prevent dragging of a first motor to a first BEV mode where the clutch is engaged to cause dragging of the first motor, in accordance with a level of an automatic operation; and increasing the threshold for a case where a degree of involvement of a driver with respect to a driving operation is a predetermined degree than a threshold for a case where the degree of involvement is higher than the predetermined degree. Further, in a case where a level of the automatic operation is higher than a level where the degree of involvement is higher than the predetermined degree, switching to the first motor travel mode is made more difficult than in the case of being at the predetermined level.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a device for controlling the switching of driving modes (or drive modes) of a hybrid vehicle having an engine and a motor as driving force sources, and in particular to a control device for a hybrid vehicle capable of autonomous driving and capable of switching the level (or mode) of autonomous driving. [Background technology]

[0002] This type of hybrid vehicle is a vehicle that improves fuel economy or energy efficiency and suppresses greenhouse gas emissions by selectively using the engine and the motor according to the required driving force, which can be grasped by the accelerator opening, etc. In order to achieve this purpose, attempts have been made to operate the engine as efficiently as possible, and one example of this is described in Patent Document 1.

[0003] The device described in Patent Document 1 aims to improve fuel efficiency by lengthening the engine stop period as much as possible. In consideration of the fact that the lower the remaining charge of the power storage device required for starting the engine, the more likely it is that the engine will start sluggishly, the device continues to run with the engine stopped until the remaining charge becomes sufficiently low in a driving state in which engine start sluggishness is not a problem, such as when the vehicle is unmanned, or in a driving state in which the impact of engine start sluggishness is small, thereby delaying engine start. In addition, in cases where the passenger is highly sensitive to the engine operation state, such as constant speed driving using so-called cruise control or manned automatic driving, the device starts the engine early when the remaining charge is relatively high and engine start sluggishness is slight. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-177102 A Summary of the Invention [Problem to be solved by the invention]

[0005] The hybrid drive device described in Patent Document 1 is a so-called two-motor type device, in which the power output by the engine is divided into a first motor side and an output side by a power split mechanism mainly composed of a planetary gear mechanism, and the reaction force by making the first motor function as a generator acts on the engine torque to control the engine speed to a fuel-efficient speed. In addition, a second motor is provided that is driven by the electric power generated by the first motor, and the output torque of the second motor is added to the torque divided to the output side by the power split mechanism. Therefore, the second motor can function as a driving force source for running like the engine, so that so-called motor running (BEV) in which the engine is stopped and the vehicle runs by the second motor is possible. In that case, in the power split mechanism, the input element connected to the engine stops rotating and the output element rotates for running, so that the reaction element to which the first motor is connected rotates. That is, the first motor rotates while being dragged as the vehicle runs by the second motor. Therefore, power loss occurs due to dragging the first motor when the vehicle runs by the second motor. To solve this problem, it is possible to disconnect the first motor from the output member that transmits the torque for driving. In this configuration, the driving form (driving mode) for motor driving can be a mode in which the first motor is disconnected and a mode in which the first motor is connected and dragged.

[0006] These motor driving modes not only differ in the amount of power consumption (or electric cost), but also in the ease of switching to hybrid driving that drives the engine, and each has its own advantages and disadvantages, so each motor driving mode is used according to the driving conditions of the vehicle. In such cases, motor driving mode switching control is required, but until now, there has been no knowledge about such switching control, and in particular, switching control in autonomous driving conditions has hardly been considered, so there is still room for development in terms of achieving both improved energy efficiency and improved drivability.

[0007] This invention has been made with a focus on the above-mentioned technical problems, and aims to provide a control device that can improve the so-called electricity consumption in a hybrid vehicle that is capable of multiple motor driving modes and different levels of autonomous driving. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention provides a hybrid vehicle having a power split mechanism that splits torque output by an engine between a first motor side and an output side, a second motor that adds / reduces torque to the torque split to the output side by the power split mechanism, an output member that outputs torque obtained by adding / reducing the torque of the second motor, and an interrupting mechanism that selectively interrupts transmission of torque between the first motor and the second motor, and a controller that can set a first motor running mode in which the vehicle runs using the second motor while allowing transmission of torque between the first motor and the second motor, and a second motor running mode in which the vehicle runs using the second motor while interrupting transmission of torque between the first motor and the second motor, and that controls the running modes of a hybrid vehicle capable of multiple levels of automatic driving with different degrees of driver involvement in driving operations, and the controller controls the running modes of the hybrid vehicle when a required driving force exceeds a predetermined threshold value while the hybrid vehicle is running in the second motor running mode. 1 motor running In a control device for a hybrid vehicle configured to switch to the first motor driving mode, the controller further has a threshold setting means for setting the threshold value according to the level of autonomous driving, and making the threshold value when the degree of involvement is a predetermined degree higher than the threshold value when the degree of involvement is higher than the predetermined degree, so that when the level of autonomous driving is a level where the degree of involvement is higher than the predetermined degree, it is more difficult to switch to the first motor driving mode compared to when the level is the predetermined degree. Effect of the Invention

[0009] According to this invention, when the requested driving force exceeds a threshold value while traveling in the second motor traveling mode in which the first motor is separated from the second motor or the output member, the mode is switched to the first motor traveling mode. The threshold value is made smaller when the level of autonomous driving is low, i.e., when the degree of the driver's involvement in the driving operation is high, and is made larger when the degree of the involvement is low. In other words, when the degree of the driver's involvement in the driving operation is low and the degree of the vehicle's independent acceleration / deceleration, steering, etc. is high, switching from the second motor traveling mode to the first motor traveling mode is less likely to occur, and the second motor traveling mode is more likely to be maintained. The second motor traveling mode is a traveling mode in which the first motor is separated from the second motor that outputs torque to the output member and the first motor is not dragged, so that the amount of power consumption is reduced by the amount of the first motor being separated. Therefore, according to this invention, when traveling by motor in a state in which the level of autonomous driving is high, it is possible to perform efficient traveling as long as possible while avoiding power loss by dragging the first motor, and as a result, power loss is reduced and energy efficiency or the electric power consumption or fuel efficiency of the vehicle can be improved. [Brief description of the drawings]

[0010] [Figure 1] 1 is a skeleton diagram illustrating an example of a hybrid drive device mounted on a hybrid vehicle according to an embodiment of the present invention. [Diagram 2] 1A is a nomographic diagram of a planetary gear mechanism for explaining the operating state in the HEV mode, FIG. 1B is a nomographic diagram of a planetary gear mechanism for explaining the operating state in the first BEV mode, and FIG. [Diagram 3] FIG. 1 is a diagram for explaining levels of autonomous driving. [Figure 4] 4 is a flowchart illustrating an example of a control executed in the embodiment of the present invention. [Diagram 5] 5 is a time chart showing an example of a change in the driving mode when the control shown in FIG. 4 is executed. [Figure 6]11 is a time chart showing an example of a change in the driving mode when the threshold value for switching from the second BEV mode to the first BEV mode is not changed even if the autonomous driving level is changed. [Figure 7] FIG. 4 is a skeleton diagram illustrating another example of a hybrid drive device mounted on a hybrid vehicle according to an embodiment of the present invention. [Figure 8] FIG. 11 is a skeleton diagram illustrating a hybrid drive device according to still another embodiment of the present invention that is mounted on a hybrid vehicle. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the embodiment described below is merely one example of the case where the present invention is implemented, and is not intended to limit the present invention.

[0012] First, to explain a hybrid vehicle, Fig. 1 shows a schematic diagram of an example of a two-motor type hybrid drive device, in which the torque output by an engine 1 is divided between a first motor (MG1) 2 and the output side, and a second motor (MG2) 3 is driven by electric power generated by the first motor 2. The engine 1 is a typical internal combustion engine such as a gasoline engine or a diesel engine, and is configured so that its output torque, starting and stopping, etc. can be electrically controlled. A power split mechanism 5 is connected to the output side of the engine 1 via a damper 4. The damper 4 is equipped with a torque limiter 6.

[0013] The power split mechanism 5 may be any mechanism that has a differential action, and Fig. 1 shows a mechanism consisting of a single-pinion planetary gear mechanism. Therefore, the power split mechanism 5 is equipped with a sun gear S that functions as a reaction element, a ring gear R that functions as an output element, and a carrier C that is disposed between the sun gear S and the ring gear R and serves as an input element holding pinion gears that mesh with the sun gear S and the ring gear R. The carrier C is connected to the damper 4 so that the torque of the engine 1 is input to the carrier C.

[0014] A first motor 2 is connected to the sun gear S. The first motor 2 is configured as a so-called motor-generator that has a function as a motor such as a permanent magnet synchronous motor and a function as a generator. Therefore, the first motor 2 is configured to apply a torque to the sun gear S in the opposite direction to the torque applied to the sun gear S from the engine 1 side, thereby amplifying the torque acting on the power split mechanism 5 from the engine 1 and outputting it from the ring gear R.

[0015] The ring gear R is connected to an output gear 8 via a clutch 7. The clutch 7 is an on-off mechanism for selectively cutting off torque transmission between the first motor 2 and the second motor 3, and is composed of a friction clutch or a meshing clutch whose engagement and release can be electrically controlled. The output gear 8 is for outputting the engine torque divided by the power split mechanism 5, and is meshed with a counter driven gear 9. That is, a counter shaft 10 is arranged in parallel with the damper 4 and the power split mechanism 5, and the counter driven gear 9 is attached to the counter shaft 10. A drive gear 11 having a smaller diameter than the counter driven gear 9 is attached to the counter shaft 10, and the drive gear 11 is meshed with a ring gear 13 of a differential gear 12, which is a final reduction gear. The differential gear 12 is configured to output drive torque to left and right drive wheels (not shown). Furthermore, the second motor 3 is disposed in parallel with the counter shaft 10, and a drive gear 15 attached to its rotor shaft 14 meshes with the counter driven gear 9. In other words, the torque of the second motor 3 is configured to be added to or subtracted from the torque output from the output gear 8.

[0016] Each of the motors 2, 3 is connected to an electricity storage device 17 via an inverter 16. The inverter 16 is configured to control the amount of discharge to each of the motors 2, 3 (i.e., the output torque of each of the motors 2, 3) and the amount of charge from each of the motors 2, 3 to the electricity storage device 17 (i.e., the reaction torque or regenerative torque by each of the motors 2, 3).

[0017] An electronic control unit (ECU) 18 is provided as a controller for controlling the engine 1, the clutch 7, or the motors 2 and 3. The ECU 18 is mainly composed of a microcomputer, a storage element, an input / output interface, etc., and is configured to perform calculations using input data and pre-stored data, and to output the results of the calculations as control command signals. Examples of input data include the accelerator opening (or throttle opening) indicating the required driving force, the vehicle speed, the state of charge (SOC) in the power storage device 17, and a signal indicating the automatic driving level, which are input to the ECU 18 from a predetermined sensor or other control device (not shown). Examples of stored data include a plurality of driving modes with different forms of generating driving force, and threshold values ​​for the required driving force (accelerator opening or throttle opening) for selecting one of these driving modes.

[0018] Here, the driving modes will be explained. According to the hybrid drive device shown in Fig. 1, three driving modes (driving modes) can be set: a hybrid mode (HEV mode) in which the engine 1 is used as the driving force source and the rotation speed of the engine 1 is controlled by the first motor 2, a first motor driving mode (first BEV mode) in which the second motor 3 is used as the driving force source and the clutch 7 is engaged to connect the engine 1 and the first motor 2 to the output gear 8 so as to be able to transmit torque, and a second motor driving mode (second BEV mode) in which the second motor 3 is used as the driving force source and the clutch 7 is released to disconnect the engine 1 and the first motor 2 so as not to transmit torque from the output gear 8.

[0019] The driving modes are explained using a collinear diagram of the planetary gear mechanism constituting the power split mechanism 5. FIG. 2A shows the operating state in the HEV mode, in which the engine 1 connected to the carrier C outputs torque, and the first motor 2 connected to the sun gear S functions as a generator to apply torque in the negative direction (opposite to the rotation direction of the engine 1) to the sun gear S. As a result, a torque in a direction to move the vehicle forward acts on the ring gear R, which is an output element to which the output gear 8 is connected. In this case, the rotation speed of the engine 1 is changed to a large or small value by controlling the rotation speed of the first motor 2, and therefore the operating point of the engine 1 can be controlled to a predetermined operating point with good fuel efficiency by the first motor 2. In this HEV mode, the engine 1 serves as a driving force source, so it can generate a large driving force, and therefore is set when the required driving force is large.

[0020] FIG. 2B shows an operating state in the first BEV mode, where the second motor (MG2) 3 outputs torque for running, causing the ring gear R, which is the output element, to rotate in the positive direction (the direction in which the engine 1 rotates). In this case, the engine 1 is stopped and the clutch 7 is engaged, so the sun gear S and the first motor 2 connected thereto are dragged by the ring gear R (second motor 3) and spin in the negative direction. In this first BEV mode, the engine 1 can be stopped while running, so that fuel consumption and greenhouse gas emissions can be reduced. In addition, energy loss occurs due to the first motor 2 spinning in the idling direction, but because the clutch 7 is engaged and the engine 1 and first motor 2 are connected to the output gear 8, it is easy to switch to the HEV mode, and therefore the first BEV mode is set when the required driving force is so-called medium, which is not large enough to select the above-mentioned HEV mode.

[0021] FIG. 2C shows an operating state in the second BEV mode, in which the engine 1 is stopped and the clutch 7 is released, and the second motor 3 outputs torque for running. Therefore, the engine 1 and the first motor 2 are disconnected from the second motor 3, which is the driving force source, so as not to transmit torque, and not only the clutch 7 to which the engine 1 is connected, but also the sun gear S and the first motor 2 connected to the sun gear S are stopped. That is, the vehicle can run with the torque of the second motor 3 without dragging the first motor 2. Therefore, compared to the first BEV mode, the energy efficiency (electricity consumption) is improved by not dragging the first motor 2. On the other hand, when the accelerator pedal (not shown) is depressed and the required driving force increases, it is necessary to control the clutch 7 to be engaged and the first motor 2 to be changed to a predetermined rotation speed, and it takes time to switch to the HEV mode, so the second BEV mode is set when the required driving force is smaller than the required driving force for setting the first BEV mode.

[0022] The hybrid vehicle according to the embodiment of the present invention is further configured to be capable of automatic driving. As is widely known, automatic driving is a driving mode in which driving operations such as starting / stopping, accelerating / decelerating, and steering for changing a course or lane are performed automatically without the assistance of a passenger (driver), and the automatic driving system may be a conventionally known system. In addition, automatic driving is classified into levels according to the degree of involvement of the passenger in the driving operation, and generally, classifications of levels 1 to 5 are known. An example is shown in FIG. 3, which is roughly divided into driving in which "monitoring by the driver" is important and driving in which "monitoring by the system" is important, with levels 1 and 2 included in "monitoring by the driver". In addition, levels 3 to 5 are included in "monitoring by the system".

[0023] Level 1 is a form of autonomous driving that is limited to so-called "driving assistance" by the system, and is a form of autonomous driving that assists in vehicle control in either the forward / reverse or left / right directions, such as automatic braking, driving to follow the vehicle ahead, and assistance in keeping the lane. Therefore, the driver is responsible for driving operations other than the functions being assisted, so the degree of driver involvement in driving operations is high. Level 2 is an "autonomous driving function under specific conditions," which includes a combination of the above-mentioned level 1 assistance functions and more advanced functions. An example of the former is a function to follow the vehicle ahead while maintaining the lane, and an example of the latter is an autonomous driving function on a highway or a motorway that automatically overtakes a low-speed vehicle ahead and automatically branches off or merges. Therefore, the driver is responsible for driving operations such as stopping and starting that are not included in the autonomous driving function, so there is involvement of the driver in driving operations in that respect.

[0024] Level 3 is what is known as "conditional autonomous driving," in which the system basically performs all driving operations, but in response to requests for system intervention, the driver performs those parts of the driving operation. Therefore, the degree of driver involvement is low. Level 4 is a form of autonomous driving in which the driver's involvement in driving operations is even lower, and is "fully autonomous driving under specific conditions." Therefore, when specific conditions are not met, the driver will be involved in driving operations. Level 5 is "fully autonomous driving," a form of autonomous driving in which the system always performs all driving operations.

[0025] The ECU 18 described above receives the autonomous driving level being executed from the autonomous driving system, and sets the driving mode according to the required driving force under that autonomous driving level. That is, the driving mode is switched when the required driving force (specifically, the accelerator opening or throttle opening) exceeds a predetermined threshold value that is a criterion for selecting each of the driving modes described above. Specifically, if the required driving force is smaller than the first threshold value, the second BEV mode is set, and the vehicle runs with the driving force of the second motor 3 without dragging the first motor 2. If the required driving force is larger than the first threshold value and smaller than the second threshold value, the first BEV mode is set. That is, the clutch 7 is engaged, and the vehicle runs with the driving force of the second motor 3 in a state in which it is easy to switch to the HEV mode. Furthermore, if the required driving force exceeds the second threshold value, the HEV mode is set, in which the engine 1 is started and a large driving force can be obtained.

[0026] In the case of low-level autonomous driving or manual driving in which the driver performs all driving operations, the driver may operate the accelerator, and in that case, the change in the accelerator opening or the requested driving force can be considered to reflect the driver's intention to accelerate or decelerate. In other words, when the accelerator pedal is depressed while driving in the second BEV mode, it can be presumed that the driver intends to accelerate, and in order to satisfy that intention, it is necessary to drive the engine 1 and increase the driving torque. Therefore, it is preferable to predict the transition to the HEV mode and switch from the second BEV mode to the first BEV mode. In contrast, in the case of an autonomous driving level in which the system determines and executes the acceleration and deceleration operation, the requested driving force may increase depending on the surrounding conditions such as the distance between the vehicle and the vehicle in front and the vehicle speed of the vehicle in front, regardless of the driver's intention, and the HEV mode is not necessarily required. Specifically, the requested driving force may increase only slightly and may be maintained without increasing to the level at which the HEV mode is set. In that case, the motor driving that drags the first motor 2 may continue, and energy efficiency (electricity consumption) may deteriorate. Therefore, in order to reduce as much as possible the power loss during motor driving, the control device in the embodiment of the present invention is configured to change the threshold value for determining the driving mode based on the level of autonomous driving. An example of such control will be described below.

[0027] Fig. 4 is a flowchart for explaining an example of such control, and in this example, the threshold value for switching from the second BEV mode to the first BEV mode is made different between the case where the vehicle is autonomously driven at the level of "monitoring by the driver" among the autonomous driving levels described above and the case where the vehicle is autonomously driven at the level of "monitoring by the system." Note that the routine shown in Fig. 4 is executed by the ECU 18 described above, and therefore the ECU 18 corresponds to the controller in this embodiment of the present invention.

[0028] First, in step S1, it is determined whether or not the vehicle is in an automatic driving state. If the determination in step S1 is negative because the vehicle is in a so-called manual driving state, the routine shown in Fig. 4 is terminated without any particular control being performed. On the other hand, if the determination in step S1 is positive, it is determined whether or not the level of automatic driving is "Level 3" or higher (step S2). In other words, it is determined whether or not the vehicle is in an automatic driving state classified as "monitoring by the system" according to the classification shown in Fig. 3 described above.

[0029] If the determination in step S2 is negative, that is, if the autonomous driving level is level 2 or lower, the threshold for switching from the second BEV mode to the first BEV mode is set to a first threshold value α (step S3), and then the routine shown in FIG. 4 is temporarily terminated. This first threshold value α may be a value that is predetermined in design, and may be the same as the threshold value adopted in so-called manual driving, for example. On the other hand, if the determination in step S2 is positive, that is, if the autonomous driving level is level 3 or higher, the threshold for switching from the second BEV mode to the first BEV mode is set to a second threshold value β (>α) that is larger than the first threshold value α (step S4), and then the routine shown in FIG. 4 is temporarily terminated. Note that the second threshold value β is a value smaller than the third threshold value γ for switching from the first BEV mode to the HEV mode described above. Therefore, the functional means for executing the control in step S3 and the functional means for executing the control in step S4 correspond to the threshold value setting means in the embodiment of the present invention.

[0030] An example of switching of driving modes when the control shown in Fig. 4 is performed is shown in Fig. 5. The example shown in Fig. 5 is an example of switching from a state in which the autonomous driving level is set to level 2 and the requested driving force is smaller than the above-mentioned first threshold value α, causing the vehicle to travel in the second BEV mode. When the requested driving force increases due to an increase in running resistance, acceleration, etc. and becomes equal to or greater than the first threshold value α (time t1), a decision to switch the driving mode from the second BEV mode to the first BEV mode is made, and a control instruction signal for the switch is output.

[0031] When the required driving force further increases and exceeds the third threshold value γ (at time t2), a decision is made to switch the driving mode from the first BEV mode to the HEV mode, and a control instruction signal for the switch is output. Since the HEV mode is a driving mode that uses the engine 1 as a driving force source, the engine 1 is started and its rotation speed gradually increases.

[0032] By maintaining the required driving force at a predetermined value equal to or greater than the third threshold value γ, the engine speed is maintained at a constant speed according to the required driving force. When the required driving force starts to decrease in this state, the engine speed also starts to decrease accordingly (time t3). When the required driving force falls below the third threshold value γ (time t4), a decision is made to switch the driving mode from the HEV mode to the first BEV mode, and a control instruction signal for the switch is output. Since the first BEV mode is a so-called motor driving mode in which the second motor 3 serves as the driving force source, the engine 1 is stopped and its speed becomes "0".

[0033] When the requested driving force further decreases and falls below the first threshold value α (at time t5), a decision to switch the driving mode from the first BEV mode to the second BEV mode is made, and a control instruction signal for the switch is output.

[0034] While traveling in the second BEV mode, the autonomous driving level is switched from level 2 to level 3 (time t6). Accordingly, the judgment threshold for the required driving force for switching from the second BEV mode traveling to the first BEV mode is changed from the first threshold value α to a larger second threshold value β. When the autonomous driving level is switched in this manner, the required driving force increases if, for example, the inter-vehicle distance with the vehicle ahead is wider than a preset distance, or the vehicle speed of the vehicle ahead to be followed is faster than that of the vehicle itself. Even if the increased required driving force exceeds the previous first threshold value α (time t7), the judgment threshold for switching to the first BEV mode has been increased to the second threshold value β, so that the judgment to switch from the second BEV mode to the first BEV mode is not made, and the second BEV mode is maintained.

[0035] Even if the increased required driving force exceeds the previous first threshold value α, the second BEV mode is maintained as long as it is below the second threshold value β, which is changed from the first threshold value α. In other words, since the vehicle runs on motor power using the second motor 3 without dragging and rotating the first motor 2, power loss is reduced compared to when the vehicle is switched to the first BEV mode, and the energy efficiency (or electricity cost) of the entire vehicle can be improved. In this case, the second motor 3 is driven by the power of the power storage device 17, and the period of so-called motor running using the second motor 3 can be extended due to the reduced power loss as described above. In other words, the number of opportunities to drive the engine 1 is reduced, improving fuel efficiency and reducing greenhouse gas emissions.

[0036] If the required driving force does not change due to constant speed driving in the level 3 autonomous driving state, the required driving force does not exceed the second threshold value β, and driving in the second BEV mode continues. If the required driving force decreases due to a narrowing of the inter-vehicle distance with the vehicle ahead or a decrease in the vehicle speed of the vehicle ahead, even if the decreased required driving force falls below the first threshold value α that was set when the autonomous driving level was level 2 (at time t8), the determination threshold value for switching the driving mode has already been changed to the second threshold value β, and the second BEV mode is maintained, so that the determination to switch the driving mode is not established. In the end, according to the control in the embodiment of the present invention, after the autonomous driving level is changed to level 3 in FIG. 5, the second BEV mode that does not drag the first motor 2 can be maintained, and energy efficiency (electricity consumption) can be improved.

[0037] For comparison, an example of a change in the driving mode when conventional control is performed without changing the threshold value for switching from the second BEV mode to the first BEV mode is shown in FIG. 6. The change in the autonomous driving level, the required driving force, and the engine speed are the same as those in the example of FIG. 5 described above, and the threshold value for switching from the second BEV mode to the first BEV mode is maintained at the first threshold value α as before, regardless of the change in the autonomous driving level. As shown in FIG. 6, the first threshold value α is maintained even when the autonomous driving level is switched to level 3, so that when the required driving force increases thereafter and exceeds the first threshold value α (at time t7), the decision to switch from the second BEV mode to the first BEV mode is made, and a control command signal for the switch is output. That is, the driving mode is switched to the first BEV mode, so that the first motor 2 is dragged and idled as shown in FIG. 2 (B). This state continues until the required driving force becomes equal to or less than the first threshold value α (at time t8), and during that time, unnecessary power loss occurs, and the energy efficiency (electricity consumption) of the vehicle deteriorates. In other words, the amount of electricity stored in the power storage device 17 consumed increases, and the start of the engine 1 is accelerated due to an insufficient SOC, resulting in poor fuel economy and increased greenhouse gas emissions.

[0038] Although one embodiment of the present invention has been described above, the hybrid vehicle of the present invention is not limited to a vehicle equipped with the hybrid drive system shown in Fig. 1, and in short, it is sufficient that the hybrid vehicle is configured to be able to cut off torque transmission from the second motor to the first motor when so-called motor driving is performed using the second motor as a driving force source. The hybrid drive system shown in Figs. 7 and 8 is an example in which the position of the clutch 7 as an interrupting mechanism for selectively cutting off torque transmission between the first motor 2 and the second motor 3 is different from the configuration shown in Fig. 1.

[0039] That is, in the hybrid drive device shown in Fig. 7, a clutch 7 is disposed between the damper 4 and the carrier C. The other configuration is the same as that shown in Fig. 1. Therefore, in the configuration shown in Fig. 7, even if the output gear 8 rotates by running with the torque of the second motor 3, the sun gear S and the first motor 2 connected thereto can be stopped by the carrier C rotating freely, and as a result, it is possible to set the second BEV mode in which the second motor 3 is used as a driving force source and the motor running is performed without dragging the first motor 2.

[0040] Moreover, the hybrid drive device shown in Fig. 8 has a clutch 7 provided between the first motor 2 and the sun gear S. The other configurations are the same as those shown in Fig. 1. Therefore, the first motor 2 can be appropriately disconnected from the second motor 3, and therefore it is possible to set a second BEV mode in which the vehicle runs on motor power without dragging the first motor 2, using the second motor 3 as a driving force source. [Explanation of symbols]

[0041] 1 Engine 2 First motor 3 Second motor 4 Damper 5 Power split mechanism 6 Torque limiter 7. Clutch 8 Output Gear 9 Counter driven gear 10 Countershaft 11 Drive gear 12 Differential gear 13 Ring gear 14 rotor shaft 15 Drive gear 16 Inverter 17 Energy storage device 18 Electronic Control Unit (ECU) C Carrier R ring gear S Sun gear

Claims

[Claim 1] A control device for a hybrid vehicle comprising: a power split mechanism that splits torque output by an engine between a first motor side and an output side; a second motor that adds / subtracts torque to the torque split to the output side by the power split mechanism; an output member that outputs torque resulting from adding / subtracting the torque of the second motor; and an interrupting mechanism that selectively cuts off transmission of torque between the first motor and the second motor, the control device being capable of setting a first motor running mode in which the vehicle runs using the second motor while allowing transmission of torque between the first motor and the second motor, and a second motor running mode in which the vehicle runs using the second motor while interrupting transmission of torque between the first motor and the second motor, and having a controller that controls running modes of a hybrid vehicle capable of multiple levels of automatic driving with different degrees of driver involvement in driving operations, the controller being configured to switch to the first motor running mode when a required driving force exceeds a predetermined threshold value while the hybrid vehicle is running in the second motor running mode; the controller further has a threshold setting means for setting the threshold in accordance with a level of the autonomous driving, and for making the threshold when the degree of involvement is a predetermined degree larger than the threshold when the degree of involvement is higher than the predetermined degree; When the level of the autonomous driving is a level in which the degree of involvement is higher than the predetermined degree, it is made more difficult to switch to the first motor running mode than when the level is the predetermined degree. A control device for a hybrid vehicle.

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