Patent ID: 12233891

DETAILED DESCRIPTION

To enhance the acceleration performance of a hybrid vehicle, it is important to increase the torque and output of an electric motor. However, increasing the torque and output of the electric motor can result in an increase in size and cost of the electric motor and an increase in size and cost of a battery. Therefore, it has been desired to enhance the acceleration performance of the hybrid vehicle by appropriately controlling a transmission and the electric motor of the hybrid vehicle while reducing the sizes and costs of the electric motor and the battery.

It is desirable to enhance the acceleration performance of a hybrid vehicle by appropriately controlling a transmission and an electric motor.

In the following, some example embodiments of the technology are described in detail with reference to the accompanying drawings. Note that the following description is directed to illustrative examples of the disclosure and not to be construed as limiting to the technology. Factors including, without limitation, numerical values, shapes, materials, components, positions of the components, and how the components are coupled to each other are illustrative only and not to be construed as limiting to the technology. Further, elements in the following example embodiments which are not recited in a most-generic independent claim of the disclosure are optional and may be provided on an as-needed basis. The drawings are schematic and are not intended to be drawn to scale. Throughout the present specification and the drawings, elements having substantially the same function and configuration are denoted with the same reference numerals to avoid any redundant description. In addition, elements that are not directly related to any embodiment of the technology are unillustrated in the drawings.

[Overall Configuration of Vehicle Control Apparatus]

FIG.1illustrates a configuration example of a hybrid vehicle11including a vehicle control apparatus10according to one example embodiment of the technology. As illustrated inFIG.1, the hybrid vehicle11may include a power train15. The power train15may include an engine12, a continuously variable transmission13, and a motor generator14. In one embodiment, the continuously variable transmission13may serve as a “transmission”. In one embodiment, the motor generator14may serve as an “electric motor”. The power train15may also be provided with an output shaft16. The output shaft16may be coupled to rear wheels19rvia a propeller shaft17and a differential mechanism18. In the example illustrated inFIG.1, the power train15may be a rear-wheel drive power train for driving the rear wheels19r.However, the power train15should not be limited to this example. For example, the power train15may be a front-wheel drive power train for driving front wheels19f,or an all-wheel drive power train for driving both the front wheels19fand the rear wheels19r.In one embodiment, the rear wheel19rmay serve as a “first wheel”. In one embodiment, the front wheel19fmay serve as a “second wheel”.

FIG.2illustrates a configuration example of the vehicle control apparatus10. As illustrated inFIG.2, the power train15may include the continuously variable transmission13. The continuously variable transmission13may include a primary pulley20, a secondary pulley21, and a drive chain22. The primary pulley20may be supported by a primary shaft23. The engine12may be coupled to one side of the primary shaft23via a forward-backward travel changeover mechanism24and a torque converter25. In addition, the motor generator14may include a rotor14rcoupled to the other side of the primary shaft23, which supports the primary pulley20. The secondary pulley21may be supported by a secondary shaft26. The secondary shaft26may be coupled to the rear wheels19rvia the output shaft16, the propeller shaft17, and the differential mechanism18.

As described above, the engine12and the rear wheels19rmay be coupled to each other via a power transmission path30. The power transmission path30may include the torque converter25, the forward-backward travel changeover mechanism24, the continuously variable transmission13, the propeller shaft17, the differential mechanism18, and other components. That is, the rear wheels19rmay be coupled to the engine12via the continuously variable transmission13. Further, the motor generator14and the rear wheel19rmay be coupled to each other via a power transmission path31. The power transmission path31may include the continuously variable transmission13, the propeller shaft17, the differential mechanism18, and other components. The forward-backward travel changeover mechanism24may include a forward clutch, a reverse brake, and a planetary gear train, and other components that are not illustrated in the drawings. The forward-backward travel changeover mechanism24may switch a direction in which the primary pulley20rotates.

The power train15may also be provided with a valve unit32to control the continuously variable transmission13, the torque converter25, the forward-backward travel changeover mechanism24and other components. The valve unit32may include, for example, a plurality of magnetic valves and oil passages. In addition, the valve unit32may be coupled to an oil pump33. The oil pump33may be driven by the engine12, for example. The valve unit32may control, for example, a supply destination and the pressure of hydraulic oil discharged from the oil pump33to thereby supply the hydraulic oil to the continuously variable transmission13, the torque converter25, the forward-backward travel changeover mechanism24, and other components. To control the continuously variable transmission13and other components via the valve unit32, the valve unit32may be coupled to a speed control unit34.

The engine12may be provided with an intake manifold40. The intake manifold40may include a throttle valve41. The throttle valve41may regulate an intake air amount. The engine12may also include an injector42and an ignition device43. The injector42may inject a fuel into an intake port or a cylinder. The ignition device43may include, for example, an ignitor or an ignition plug. To control the engine12via the throttle valve41and other components, the throttle valve41, the injector42, the ignition device43, and other components of the engine12may be coupled to an engine control unit44.

The motor generator14may include a stator14scoupled to a battery pack51via an inverter50. The battery pack51may include a battery module53and a main relay54coupled to the battery module53. The battery module53may include a plurality of battery cells52. In one embodiment, the battery module53may serve as an “electric power storage device”. The battery pack51may also include a battery control unit55and a battery sensor56. The battery control unit55may monitor charging and discharging of the battery module53. The battery sensor56may detect, for example, a charging current, a discharging current, and a terminal voltage. The battery control unit55may have a function of calculating a state of charge (SOC) of the battery module53on the basis of, for example, the charging current, the discharging current, and the terminal voltage detected by the battery sensor56. Note that the SOC of the battery module53may refer to the rate indicating the remaining amount of electric power in the battery module53. That is, the SOC of the battery module53may be the rate of a charged amount to the full charge capacity of the battery module53.

To control the motor generator14via the inverter50, the inverter50may be coupled to a motor control unit57. The motor control unit57may control an energization state of the stator14sby controlling the inverter50, which includes a plurality of switching elements and other elements, to thereby control the torque and the revolution speed of the motor generator14. To bring the motor generator14into a power running state, electric power may be supplied from the battery module53to the stator14svia the inverter50. In contrast, to bring the motor generator14into a power generation state, electric power may be supplied from the stator14sto the battery module53via the inverter50.

[Control System]

As illustrated inFIG.2, the vehicle control apparatus10may include a control system60that controls the power train15and other components. The control system60may include a plurality of electronic control units. Examples of the electronic control units in the control system60may include the speed control unit34, the engine control unit44, the battery control unit55, and the motor control unit57that are described above, and a vehicle control unit61. The vehicle control unit61may output control signals to the speed control unit34, the engine control unit44, the battery control unit55, and the motor control unit57. The speed control unit34, the engine control unit44, the battery control unit55, the motor control unit57, and the vehicle control unit61may be communicably coupled to each other via an in-vehicle network62, such as a controller area network (CAN) or a local interconnect network (LIN). The vehicle control unit61may set operation targets of the engine12, the continuously variable transmission13, and other components on the basis of input information received from the speed control unit34, the engine control unit44, the battery control unit55, the motor control unit57, and various sensors described below. Thereafter, the vehicle control unit61may generate control signals on the basis of the operation targets of the engine12, the continuously variable transmission13, and other components, and output the control signals to the speed control unit34, the engine control unit44, the battery control unit55, and the motor control unit57.

Examples of sensors coupled to the vehicle control unit61may include a vehicle speed sensor70, an acceleration sensor71, an acceleration sensor72, and an engine revolution sensor73. The vehicle speed sensor70may detect a vehicle speed which is a traveling speed of the hybrid vehicle11. The acceleration sensor71may detect forward/backward acceleration exerted in a front/back direction of the hybrid vehicle11. The acceleration sensor72may detect lateral acceleration exerted in a width direction of the hybrid vehicle11. The engine revolution sensor73that detects an engine revolution number which is a revolution speed of the engine12. Other examples of sensors coupled to the vehicle control unit61may include an accelerator sensor74, a brake sensor75, and a steering angle sensor76. The accelerator sensor74may detect an operational state of an accelerator pedal. The brake sensor75may detect an operational state of a brake pedal. The steering angle sensor76may detect the steering angle of a steering wheel. Still other examples of sensors coupled to the vehicle control unit61may include a primary revolution sensor77and a secondary revolution sensor78. The primary revolution sensor77may detect the revolution speed of the primary pulley20. The secondary revolution sensor78may detect the revolution speed of the secondary pulley21. In addition, a start switch79may be coupled to the vehicle control unit61. The start switch79may be operated by a driver who drives the hybrid vehicle11to start the control system60.

FIG.3schematically illustrates a basic configuration of each of the speed control unit34, the engine control unit44, the battery control unit55, the motor control unit57, and the vehicle control unit61. As illustrated inFIG.3, the speed control unit34, the engine control unit44, the battery control unit55, the motor control unit57, and the vehicle control unit61may each include a microcontroller82. The microcontroller82may include, for example, a processor80and a memory81. The memory81may store a predetermined program, and the processor80may execute a command set of the program. The processor80and the memory81may be communicably coupled to each other. In the example illustrated inFIG.3, the microcontroller82may include one processor80and one memory81. However, the microcontroller82should not be limited to this example. Alternatively, the microcontroller82may include a plurality of processors80and a plurality of memories81.

The speed control unit34, the engine control unit44, the battery control unit55, the motor control unit57, and the vehicle control unit61may each include an input conversion circuit83, a drive circuit84, a communication circuit85, an external memory86, a power circuit87, and other components. The input conversion circuit83may convert signals received from various sensors into signals receivable by the microcontroller82. The drive circuit84may generate drive signals for driving an actuator, such as the valve unit32described above, on the basis of signals outputted from the microcontroller82. The communication circuit85may convert signals outputted from the microcontroller82into communication signals to be transmitted to the other control units. The communication circuit85may also convert communication signals received from the other control units into signals receivable by the microcontroller82. The power circuit87may supply a stable power voltage to the microcontroller82, the input conversion circuit83, the drive circuit84, the communication circuit85, the external memory86, and other components. The external memory86may be, for example, a non-volatile memory that stores data to be held even while electric power is not supplied thereto.

[Speed Control]

In the following, speed control performed by the control system60is described. The control system60may control the continuously variable transmission13in two speed modes: an ordinary speed mode and an adaptive speed mode. The ordinary speed mode may be executed for ordinary traveling of the hybrid vehicle11. In one embodiment, the ordinary speed mode may serve as a “first speed mode”. The adaptive speed mode may be executed for sport traveling of the hybrid vehicle11. In one embodiment, the adaptive speed mode may serve as a “second speed mode”. In a case where a driving intensity (to be described later) imparted by the driver is less than a predetermined threshold D1, the ordinary speed mode may be selected and executed. In contrast, in a case where the driving intensity imparted by the driver is greater than the predetermined threshold D1, the adaptive speed mode may be selected and executed. The term “driving intensity” used herein may refer to an index calculated by the control system60on the basis of a driving operation performed by the driver. That is, the driving intensity may indicate the degree of intensity of a driving operation performed by the driver. In a case where the driving operation, such as an accelerator operation, is performed softly, the control system60may calculate a small driving intensity. In contrast, in a case where the driving operation, such as an accelerator operation, is not performed softly, the control system60may calculate a large driving intensity. Note that the control system60may calculate and update the driving intensity in a predetermined cycle on the basis of the driving operation, such as an accelerator operation and a brake operation, performed for a predetermined period of time or over a predetermined travel distance.

For example, a large driving intensity may be calculated in a case where the operation amount of the accelerator pedal (hereinafter referred to as an accelerator position) is large or where the operation speed of the accelerator pedal is high. A large driving intensity may be calculated also in a case where the operation amount of the brake pedal is large, where the operation speed of the brake pedal is high, where the operation amount of the steering wheel is large, or where the operation speed of the steering wheel is high. Further, a large driving intensity may be calculated also in a case where the vehicle speed is high, where the forward/backward acceleration rate is high, or where the lateral acceleration rate is high. In contrast, a small driving intensity may be calculated in a case where the accelerator position is small or where the operation speed of the accelerator pedal is low. A small driving intensity may be calculated also in a case where the operation amount of the brake pedal is small, where the operation speed of the brake pedal is low, where the operation amount of the steering wheel is small, or where the operation speed of the brake pedal is low. Further, a small driving intensity may be calculated also in a case where the vehicle speed is low, where the forward/backward acceleration rate is low, or where the lateral acceleration rate is low.

<Speed Control: Ordinary Speed Mode>

In the following, the ordinary speed mode is described.FIG.4illustrates a speed characteristic map used in the ordinary speed mode. The control system60may set a target speed ratio to be used in the ordinary speed mode on the basis of the accelerator position and the vehicle speed by referring to the speed characteristic map. As illustrated inFIG.4, the speed characteristic map may have a characteristic line LOW and a characteristic line HIGH. The characteristic line LOW may indicate a maximum speed ratio on a low side. The characteristic line HIGH may indicate a minimum speed ratio on a high side. The speed characteristic map may also have a plurality of other characteristic lines, as indicated by broken lines. These characteristic lines may correspond to respective accelerator positions, i.e., respective required driving forces. Note that the term “speed ratio” may refer to the ratio of the revolution speed of the primary pulley20(i.e., a primary revolution number Np) to the revolution speed of the secondary pulley21(i.e., a secondary revolution number Ns) (i.e., Np/Ns). Accordingly, the speed ratio may be set on a lower side as the value of the speed ratio increases, whereas the speed ratio may be set on a higher side as the value of the speed ratio decreases.

As illustrated inFIG.4, a characteristic line to be selected may be shifted in the direction indicated by an arrow α as the accelerator position is increased by depressing the accelerator pedal, i.e., as the driving force required to the hybrid vehicle11increases. In contrast, a characteristic line to be selected may be shifted in the direction indicated by an arrow β as the accelerator position is decreased by releasing the accelerator pedal, i.e., as the driving force required to the hybrid vehicle11decreases. For example, in a case where the accelerator pedal is depressed while the hybrid vehicle11is traveling at a vehicle speed V1, a target primary revolution number may be increased from “Npa” to “Npb”, and a target speed ratio of the continuously variable transmission13may be continuously controlled from “Tra” toward “Trb” on the low side, as indicated by an arrow γ. As described above, in the ordinary speed mode, the target speed ratio may be set on the basis of the accelerator position and the vehicle speed, and the groove widths of the primary pulley20and the secondary pulley21may be controlled toward the target speed ratio.

<Speed Control: Adaptive Speed Mode>

In the following, the adaptive speed mode is described.FIG.5illustrates examples of fixed speed ratios used in the adaptive speed mode, andFIG.6illustrates an exemplary target speed level used in the adaptive speed mode. As illustrated inFIG.5, a plurality of fixed speed ratios R1 to R10 may be set in the adaptive speed mode as target speed ratios or target speed levels of the speed mode. In addition, as illustrated inFIG.6, the control system60may set the target speed level on the basis of the vehicle speed and the driving intensity. That is, the control system60may set the target speed level on a higher speed level side (on the high side) as the vehicle speed increases, whereas may set the target speed level on a lower speed level side (on the low side) as the vehicle speed decreases. Further, the control system60may set the target speed level on a lower speed level side (on the low side) as the driving intensity increases, whereas may set a target speed level on a higher speed level side (on the high side) as the driving intensity decreases.

Further, in the adaptive speed mode, the target speed level may be corrected on the basis of a road surface gradient.FIG.7illustrates an exemplary correction of the target speed level. As illustrated inFIG.7, the target speed level may be corrected to a lower speed level side as the upward gradient of a traveling road surface increases, whereas may be corrected to a higher speed level side as the downward gradient of the traveling road surface increases. For example, in a case where the upward gradient of the traveling road surface is “S1”, the target speed level set on the basis ofFIG.6may be corrected to the low speed side by one level. In contrast, in a case where the downward gradient of the traveling road surface is “−S2”, the target speed level set on the basis ofFIG.6may be corrected to the high speed level side by one level. Note that the control system60may calculate the gradient of the traveling road surface on the basis of a frontward/backward acceleration rate detected by the acceleration sensor71.

FIG.8is a timing chart illustrating an exemplary transition of an engine revolution number.FIG.8illustrates a traveling state of the hybrid vehicle11from the time when the hybrid vehicle11enters a corner to the time when the hybrid vehicle11exits from the corner. For example, in a case where the driving intensity calculated on the basis of the accelerator operation and other factors is greater than a predetermined threshold D1 at a time t1 as indicated by a reference sign a1 inFIG.8, the adaptive speed mode may be executed as the speed mode of the continuously variable transmission13. Thereafter, when the hybrid vehicle11enters the corner at a time t2, the driver may release the accelerator pedal to decrease the accelerator position, as indicated by a reference sign b1.

Even in a case where the accelerator position decreases as described above, the target speed level in the adaptive speed mode may be set on the basis of the vehicle speed and the driving intensity, as illustrated inFIG.6. Thus, the target speed level, i.e., the speed ratio of the continuously variable transmission13may be maintained, as indicated by a reference sign c1. This suppresses an excessive decrease in the engine revolution number, as indicated by a reference sign d1. Thereafter, when the hybrid vehicle11exits from the corner at a time t3 after cornering, the driver may depress the accelerator pedal to start increasing the accelerator position, as indicated by a reference sign b2. In this case, the engine revolution number may be kept at a relatively high level during the cornering due to the adaptive speed mode, as indicated by a reference sign d2. This enhances the acceleration responsivity of the hybrid vehicle11at the time of exit from the corner.

In contrast, in a case where the ordinary traveling mode is executed from the time when the hybrid vehicle11enters the corner to the time when the hybrid vehicle11exits from the corner, the engine revolution number may be greatly decreased during the cornering, as indicated by a broken line inFIG.8. This makes it difficult to enhance the acceleration responsivity of the hybrid vehicle11at the time of exit from the corner. For example, in a case where the driving intensity calculated on the basis of the accelerator operation and other factors is less than the predetermined threshold D1 at the time t1 as indicated by a reference sign e1 inFIG.8, the ordinary speed mode may be executed as the speed mode of the continuously variable transmission13. Thereafter, when the hybrid vehicle11enters the corner at the time t2, the driver may release the accelerator pedal to decrease the accelerator position, as indicated by a reference sign b1.

As described above with reference toFIG.4, the target speed ratio in the ordinary speed mode may be set on the basis of the accelerator position, i.e., the required driving force. Accordingly, in a case where the accelerator position is decreased, the target speed ratio may be upshifted to the high side, as indicated by a reference sign f1, and the engine revolution number may be greatly decreased, as indicated by a reference sign g1. Thereafter, when the hybrid vehicle11exits from the corner at the time t3 after cornering, the driver may depress the accelerator pedal to start increasing the accelerator position, as indicated by the reference sign b2. In this case, the engine revolution number may be greatly decreased during the cornering due to the ordinary speed mode, as indicated by a reference sign g2. This reduces the acceleration responsivity of the hybrid vehicle11at the time of exit from the corner.

As described above, when the accelerator pedal is released, upshifting is suppressed in the adaptive speed mode, whereas upshifting is actively executed in the ordinary speed mode. That is, when the accelerator operation is cancelled by the driver, the speed ratio is set to a lower side in the adaptive speed mode than in the ordinary speed mode. Accordingly, even in a case where the accelerator operation is cancelled when the hybrid vehicle11enters a corner, it is possible to suppress the upshifting and maintain the engine revolution number at a relatively high level by executing the adaptive speed mode as the speed mode. This enhances the acceleration responsivity of the hybrid vehicle11at the time of exit from the corner.

[Assist Control]

Next, a description is given of assist control executed by the control system60. To enhance the acceleration responsivity in the adaptive speed mode, the control system60executes the assist control in which the motor generator14is brought into a power-running state while the hybrid vehicle11is accelerating. In the assist control, two assist modes may be used: an ordinary assist mode and an acceleration assist mode. In the ordinary assist mode, a small target motor torque may be set. In the acceleration assist mode, a large target motor torque may be set. In one embodiment, the ordinary assist mode may serve as a “first assist mode”. In one embodiment, the acceleration assist mode may serve as a “second assist mode”. For example, in a condition where the required driving force to the hybrid vehicle11is the same between the ordinary assist mode and the acceleration assist mode, i.e., the accelerator position is the same between the ordinary assist mode and the acceleration assist mode, power-running torque of the motor generator14may be set to a larger value in the acceleration assist mode than in the ordinary assist mode. Note that the power-running torque of the motor generator14may refer to motor torque outputted from the motor generator14that has been brought into the power-running state.

<Assist Control: Ordinary Assist Mode>

In the following, the ordinary assist mode is described.FIG.9is a diagram illustrating an exemplary operating point of the engine12.FIG.9illustrates exemplary target engine torque and exemplary target motor torque that are set in a case where the ordinary assist mode is executed. Note that dashed-dotted lines inFIG.9each connect points equal to each other in heat efficiency. The heat efficiency of the engine12may increase toward a dashed-dotted line La, as indicated by an arrow α inFIG.9, whereas may decrease toward a dashed-dotted line Lb, as indicated by an arrow β inFIG.9. A solid line Ma1 inFIG.9may indicate maximum torque of the engine12, and a broken line Ma2 inFIG.9may indicate maximum total torque of the power sources, i.e., the engine12and the motor generator14.

As illustrated inFIG.9, in a case where the ordinary assist mode is executed, the control system60may set a required driving force to the drive wheel (e.g., the rear wheel19r) on the basis of the accelerator position set by the driver, and set a target operating point Pt of the power sources (i.e., the engine12and the motor generator14) on the basis of the required driving force. Thereafter, the control system60may set a target operating point Pe of the engine12and target engine torque Te1 of the engine12to increase the heat efficiency. Thereafter, the control system60may set target motor torque Tm1 of the motor generator14so that the power sources (i.e., the engine12and the motor generator14) operate at the target operating point Pt when the engine12is controlled to the target engine torque Te1. As described above, in a case where the ordinary assist mode is executed, the target engine torque Te1 may be set to increase the heat efficiency, following which the target motor torque Tm1 may be set to obtain a desired required driving force. This allows the engine12to operate in a high heat efficiency region even while the hybrid vehicle11is accelerating. Accordingly, it is possible to enhance the fuel economy performance of the hybrid vehicle11. <Assist Control: Acceleration Assist Mode>

In the following, the acceleration assist mode is described.FIG.10is a diagram illustrating an exemplary operating point of the engine12.FIG.10illustrates exemplary target engine torque and exemplary target motor torque that are set in a case where the acceleration assist mode is executed.FIG.11illustrates the exemplary target motor torque set in the acceleration assist mode. Note that the vehicle speed and the required driving force are the same between the examples illustrated inFIG.9and the condition illustrated inFIG.10.

As illustrated inFIG.10, in a case where the acceleration assist mode is executed, the control system60may set a required driving force to the drive wheel on the basis of the accelerator position set by the driver, and set a target operating point Pt of the power sources (i.e., the engine12and the motor generator14) on the basis of the required driving force. Thereafter, the control system60may set target motor torque Tm2 on the basis of the accelerator position by referring to the torque map illustrated inFIG.11. As illustrated inFIG.11, the target motor torque Tm2 may be set to a larger value as the accelerator position increases, whereas to a smaller value as the accelerator position decreases. Thereafter, the control system60may set the target engine torque Te2 so that the power sources (i.e., the engine12and the motor generator14) operate at the target operating point Pt when the motor generator14is controlled to the target motor torque Tm2. As described above, in a case where the acceleration assist mode is executed, the target motor torque Tm2 may be set on the basis of the accelerator position, following which the target engine torque Te2 may be set to obtain a desired required driving force. This allows the motor generator14to be used actively. Accordingly, it is possible to enhance the acceleration responsivity of the hybrid vehicle11. Note that, in the acceleration assist mode illustrated inFIG.10, the operating point of the engine12is indicated by a reference sign Pe2.

[Assist Mode Switching Control (Flowchart)]

As described above, the motor generator14may be used more actively in the acceleration assist mode than in the ordinary assist mode. This increases the acceleration responsivity of the hybrid vehicle11. Accordingly, it is desirable to actively execute the acceleration assist mode in sport traveling in which the adaptive speed mode is executed. However, the execution of the acceleration assist mode can result in a large decrease in the SOC of the battery module53. Accordingly, it has been desired to execute the acceleration assist mode contributing to an increase in the acceleration responsivity at an appropriate timing. To this end, the control system60may execute the acceleration assist mode contributing to an increase in the acceleration responsivity at an appropriate timing by executing assist mode switching control described below.

In the following, the assist mode switching control executed by the control system60is described.FIG.12is a flowchart illustrating an exemplary procedure for the assist mode switching control.FIG.13illustrates an exemplary starting threshold Xa1.FIG.14illustrates exemplary coefficients k1 to k4 used to set an execution time Xt.FIG.15illustrates an exemplary stopping threshold Xa2. Each step illustrated in the flowchart ofFIG.12indicates a process executed by the processor(s)80in the control system60. Note that the assist mode switching control illustrated inFIG.12may be executed by the control system60in a predetermined cycle after the driver operates the start switch79to start the control system60, which includes the vehicle control unit61and other components.

As illustrated inFIG.12, it may be determined in Step S10whether the adaptive speed mode is being executed. If it is not determined in Step S10that the adaptive speed mode is being executed (Step S10: NO), the procedure may exit the routine of the assist mode switching control. If it is determined in Step S10that adaptive speed mode is being executed (Step S10: YES), the procedure may proceed to Step S11. In Step S11, the ordinary assist mode may be selected as the assist mode. That is, in a case where the hybrid vehicle11is accelerated by depressing the accelerator pedal, the ordinary assist mode may be executed as the assist mode. Thereafter, the procedure may proceed to Step S12. In Step S12, the starting threshold Xa1 may be set on the basis of the vehicle speed and the road surface gradient, following which the procedure may proceed to Step S13. In Step S13, it may be determined whether an accelerator position Acp is greater than the starting threshold Xa1. In one embodiment, the accelerator position Acp may serve as an “amount of the accelerator operation”. As illustrated inFIG.13, the starting threshold Xa1 may be set to a larger value as the vehicle speed increases or as the upward gradient of the traveling road surface increases. That is, the starting threshold Xa1 may be set to a larger value as a traveling resistance of the hybrid vehicle11increases.

As illustrated inFIG.12, if it is determined in Step S13that the accelerator position Acp is less than or equal to the starting threshold Xa1, i.e., if it is not determined that high acceleration is required by the driver (Step S13: NO), the procedure may return to Step S11in which the ordinary assist mode is kept selected. In contrast, if it is determined in Step S13that the accelerator position Acp is greater than the starting threshold Xa1 (Step S13: YES), i.e., if it is determined that high acceleration is required by the driver, the procedure may proceed to Step S14in which the acceleration assist mode is executed. As described above, in a case where the accelerator position Acp is increased greater than the starting threshold Xa1 while the adaptive speed mode is being executed, the ordinary assist mode is switched to the acceleration assist mode. This allows the motor generator14to be actively driven in order to accelerate the hybrid vehicle11at the time of exit from the corner, for example. Accordingly, it is possible to further enhance the acceleration responsivity of the hybrid vehicle11in the adaptive speed mode.

In Step S15, a predetermined reference time Tb may be multiplied by the coefficients k1 to k4 to set an execution time Xt. The execution time Xt may be a duration time of the acceleration assist mode. As illustrated inFIG.14, the coefficient k1 may be set on the basis of the vehicle speed, and may be set to a larger value as the vehicle speed decreases. The coefficient k2 may be set on the basis of the road surface gradient, and may be set to a larger value as the downward gradient increases. The coefficient k3 may be set on the basis of the accelerator position, and may be set to a larger value as the accelerator position increases. The coefficient k4 may be set on the basis of the SOC, and may be set to a larger value as the SOC increases. That is, the execution time Xt may be set to a longer time as the vehicle speed decreases, as the downward gradient increases, as the accelerator position increases, or as the SOC is increases. In contrast, the execution time Xt may be set to a shorter time as the vehicle speed increases, as the upward gradient increases, as the accelerator position decreases, as the SOC decreases.

After the execution time Xt is set on the basis of the accelerator position and other factors as described above, the procedure may proceed to Step S16. In Step S16, it may be determined whether an elapsed time Tacc from the start of the acceleration assist mode is longer than the execution time Xt. If it is determined in Step S16that the elapsed time Tacc is longer than the execution time Xt (Step S16: YES), i.e., if the acceleration assist mode has been executed for a longer time than the predetermined execution time Xt, the procedure may proceed to Step S17in which the acceleration assist mode is stopped. Thereafter, the procedure may proceed to Step S18in which it is determined whether the adaptive speed mode is to be stopped. If it is determined in Step S18that the adaptive speed mode is to be stopped (Step S18: YES), the procedure may exit the routine. In contrast, if it is determined in Step S18that the adaptive speed mode is to be maintained (Step S18: NO), the procedure may return to Step S11in which the ordinary assist mode is selected. That is, in a case where the adaptive speed mode is to be maintained, the assist mode may be switched from the acceleration assist mode to the ordinary assist mode.

In contrast, if it is determined in Step S16that the elapsed time Tacc is shorter than or equal to the execution time Xt (Step S16: NO), i.e., if the acceleration assist mode has not been executed for a longer time than the predetermined execution time Xt, the procedure may proceed to Step S19in which the stopping threshold Xa2 is set on the basis of the vehicle speed and the road surface gradient. Thereafter, the procedure may proceed to Step S20in which it is determined whether the accelerator position Acp is less than the stopping threshold Xa2. As illustrated inFIG.15, the stopping threshold Xa2 may be set to a larger value as the vehicle speed increases, or as the upward gradient of the traveling road surface increases. That is, the stopping threshold Xa2 may be set to a larger value as the traveling resistance of the hybrid vehicle11increases. Note that the stopping threshold Xa2 may be less than the starting threshold Xa1 described above.

As illustrated inFIG.12, if it is determined in Step S20that the accelerator position Acp is greater than or equal to the stopping threshold Xa2 (Step S20: NO), i.e., if it is determined that acceleration is continuously requested by the driver, the procedure may return to Step S14in which the acceleration assist mode is kept executed. In contrast, if it is determined in Step S20that the accelerator position Acp is less than the stopping threshold Xa2 (Step S20: YES), i.e., if it is determined that high acceleration is no longer required by the driver, the procedure may proceed to Step S17in which the acceleration assist mode is stopped. Thereafter, the procedure may proceed to Step S18in which it is determined whether the adaptive speed mode is to be stopped.

As described above, in a case where the accelerator position Acp is increased greater than the starting threshold Xa1 while the adaptive speed mode is being executed, the ordinary assist mode may be switched to the acceleration assist mode. This allows the motor generator14to be actively driven at an appropriate timing. Accordingly, it is possible to further enhance the acceleration responsivity of the hybrid vehicle11in the adaptive speed mode. Further, in a case where the acceleration assist mode has been maintained for a longer time than the predetermined execution time Xt, the acceleration assist mode may be switched to the ordinary assist mode. In addition, if it is determined that the accelerator position Acp is decreased less than the stopping threshold Xa2, which is less than the starting threshold Xa1, while the acceleration assist mode is being executed, the acceleration assist mode may be switched to the ordinary assist mode. This allows the acceleration assist mode to end at an appropriate timing. Accordingly, it is possible to use the electric power energy of the battery module53in an efficient manner.

In addition, the starting threshold Xa1 on the basis of which a timing to start the acceleration assist mode is determined and the stopping threshold Xa2 on the basis of which a timing to stop the acceleration assist mode is determined may be set to larger values as the traveling resistance of the hybrid vehicle11increases. This allows the acceleration assist mode contributing to the acceleration responsivity to be executed at an appropriate timing. Note that, although the starting threshold Xa1 and the stopping threshold Xa2 may be set on the basis of the vehicle speed and the road surface gradient in the examples illustrated inFIGS.13and15, these examples are non-limiting examples. The starting threshold Xa1 and the stopping threshold Xa2 may be set on the basis of only the vehicle speed or only the road surface gradient.

In addition, the execution time Xt on the basis of which the duration time of the acceleration assist mode is determined may be set to a longer time as the vehicle speed decreases or the downward gradient increases. This allows the acceleration assist mode to be maintained for a long time in a condition where the acceleration assist mode contributes to the acceleration responsivity. Accordingly, it is possible to enhance the acceleration responsivity in the adaptive speed mode. In addition, the execution time Xt on the basis of which the duration time of the acceleration assist mode is determined may be set to a longer time as the accelerator position or the SOC increases. This allows the acceleration assist mode to be maintained for a long time in a case where the driver requests high acceleration or where sufficient electric power energy is stored in the battery module53. Accordingly, it is possible to enhance the acceleration responsivity in the adaptive speed mode.

In the example illustrated inFIG.14, the coefficient k1 may be set to a larger value as the vehicle speed decreases, and the coefficient k2 may be set to a larger value as the downward gradient increases. However, this example is a non-limiting example. For example, as indicated by a broken line inFIG.14, the coefficient k1 may be set to a larger value as the vehicle speed increases, and the coefficient k2 may be set to a larger value as the upward gradient increases. That is, the execution time Xt on the basis of which the duration time of the acceleration assist mode is determined may be set to a longer time as the vehicle speed or the upward gradient increases. For example, in a case where the battery module53has a large electric storage capacity, it is possible to actively expand the power-running region of the motor generator14. Such a hybrid vehicle allows the acceleration assist mode to be maintained for a long time in a case where the vehicle speed is high or where the upward gradient is large. Accordingly, it is possible to enhance the acceleration responsivity in the adaptive speed mode.

In the above example embodiments, the execution time Xt on the basis of which the duration time of the acceleration assist mode is determined may be set on the basis of the vehicle speed, the road surface gradient, the accelerator position, and the SOC. However, these embodiments are non-limiting examples. For example, the execution time Xt may be set on the basis of only the vehicle speed, only the road surface gradient, only the accelerator position, or only the SOC. That is, the execution time Xt only has to be set on the basis of at least one of the vehicle speed, the road surface gradient, the accelerator position, or the SOC.

[Assist Mode Switching Control (Timing Chart)]

Next, the assist mode switching control described above is described with reference to a timing chart.FIG.16is a timing chart illustrating an exemplary execution status of the assist mode switching control. In a case where the driving intensity imparted by the driver is greater than a threshold D1 at a time t1 inFIG.16, as indicated by reference sign a1, the adaptive speed mode may be executed as the speed mode, as indicated by a reference sign b1. In addition, in a case where the accelerator position is lower than the stopping threshold Xa2 at the time t1, as indicated by a reference sign c1, the ordinary assist mode may be executed at the time of acceleration of the hybrid vehicle11, as indicated by a reference sign d1. Thereafter, at a time t2, the accelerator position may be increased greater than the starting threshold Xa1 by depressing the accelerator pedal, as indicated by a reference sign c2. This causes the assist mode to be switched from the ordinary assist mode to the acceleration assist mode, as indicated by a reference sign d2. Thereafter, at a time t3, the duration time of the acceleration assist mode may be longer than the execution time Xt. This causes the assist mode to be switched from the acceleration assist mode to the ordinary assist mode, as indicated by a reference sign d3. In a case where the accelerator position is decreased lower than the stopping threshold Xa2 by releasing the accelerator pedal at a time t3a, as indicated by a broken line inFIG.16, while the adaptive speed mode and the acceleration assist mode are being executed, the assist mode may be switched from the acceleration assist mode to the ordinary assist mode, as indicated by a reference sign f1.

As described above, in a case where the accelerator position is increased greater than the starting threshold Xa1 while the adaptive speed mode is executed, the assist mode is switched from the ordinary assist mode to the acceleration assist mode. This allows the motor generator14to be actively driven at an appropriate timing. Accordingly, it is possible to further enhance the acceleration responsivity in the adaptive speed mode. Further, in a case where the acceleration assist mode has been executed for the predetermined execution time Xt, the assist mode is switched from the acceleration assist mode to the ordinary assist mode. Further, in a case where it is determined that the accelerator position Acp is decreased less than the stopping threshold Xa2, which is less than the starting threshold Xa1, while the acceleration assist mode is being executed, the assist mode is switched from the acceleration assist mode to the ordinary assist mode. This allows the acceleration assist mode to end at an appropriate timing. Accordingly, it is possible to use the electric energy of the battery module53in an efficient manner.

It is to be appreciated that the technology should not be limited to this example embodiments described above and may be modified in various ways without departing from the gist of the technology. Although the control system60may include the plurality of control units34,44,55,57, and61in the example embodiments described above, the control system60should not be limited to this example. For example, the control system60may include one control unit. In addition, although the motor generator14may be coupled to the input side of the continuously variable transmission13in the example illustrated inFIG.2, this is a non-limiting example. Alternatively, the motor generator14may be coupled to an output side of the continuously variable transmission13. Further, although both the engine12and the motor generator14may be coupled to the rear wheels19rin the example illustrated inFIG.2, this is a non-limiting example. For example, both the engine12and the motor generator14may be coupled to the front wheels19f.Alternatively, the engine12may be coupled to the front wheels19f,while the motor generator14may be coupled to the rear wheels19r.Still alternatively, the engine12may be coupled to the rear wheels19r,while the motor generator14may be coupled to the front wheels19f.Still alternatively, the engine12may be coupled to both the front wheels19fand the rear wheels19r,or the motor generator14may be coupled to both the front wheels19fand the rear wheels19r.In the above description, the rear wheel19rmay serve as the first wheel, and the front wheel19fmay serve as the second wheel. However, this is a non-limiting example. Alternatively, the front wheel19fmay serve as the first wheel, and the rear wheel19rmay serve as the second wheel.

In the example embodiments illustrated inFIGS.12and14, to set the execution time Xt of the acceleration assist mode, the coefficients k1 to k4 may be set on the basis of the vehicle speed, the accelerator position, and other parameters, and the reference time Tb may be multiplied by the coefficients k1 to k4. However, this is a non-limiting example. For example, a plurality of execution times may be set respectively on the basis of the vehicle speed, the road surface gradient, the accelerator position, and the SOC, and these execution times may be added to each other to set the execution time Xt. In addition, although the continuously variable transmission13may be used as a transmission in the example illustrated inFIG.2, this is a non-limiting example. For example, a planetary gear automatic transmission or a parallel axis automatic transmission may be used as a transmission. Further, although the speed ratio may be continuously changed in the ordinary speed mode in the above description, this is a non-limiting example. Alternatively, the speed ratio may be changed in a stepwise manner in the ordinary speed mode. Further, although the speed ratio may be changed in a stepwise manner in the adaptive speed mode in the above description, this is a non-limiting example. Alternatively, the speed ratio may be continuously changed in the adaptive speed mode.

According to the vehicle control apparatus of any one of the example embodiments described above, the assist mode is switched to the second assist mode in a case where the amount of accelerator operation performed by the driver is increased greater than the starting threshold while the second speed mode is being executed. This allows the transmission and the electric motor to be appropriately controlled. Accordingly, it is possible to enhance the acceleration performance of the hybrid vehicle.

The control system60inFIG.2is implementable by circuitry including at least one semiconductor integrated circuit such as at least one processor (e.g., a central processing unit (CPU)), at least one application specific integrated circuit (ASIC), and/or at least one field programmable gate array (FPGA). At least one processor is configurable, by reading instructions from at least one machine readable non-transitory tangible medium, to perform all or a part of functions of the control system60. Such a medium may take many forms, including, but not limited to, any type of magnetic medium such as a hard disk, any type of optical medium such as a CD and a DVD, any type of semiconductor memory (i.e., semiconductor circuit) such as a volatile memory and a non-volatile memory. The volatile memory may include a DRAM and a SRAM, and the nonvolatile memory may include a ROM and a NVRAM. The ASIC is an integrated circuit (IC) customized to perform, and the FPGA is an integrated circuit designed to be configured after manufacturing in order to perform, all or a part of the functions of the control system60illustrated inFIG.2.