Vehicle braked by motor torque and method of controlling the vehicle

A vehicle that is driven while regulating power output from a power source to a drive shaft through an operation of an accelerator unit, the vehicle comprising:

• a power transmittable engine that is capable of transmitting power to the drive shaft;
• a motor that is capable of applying a braking force to the drive shaft;
• a detection unit that measures an operating amount of the accelerator unit;
• a target speed reduction rate setting unit that, when the measured operating amount of the accelerator unit is not greater than a predetermined level, sets a target speed reduction rate of the vehicle corresponding to the measured operating amount, based on a predetermined relationship between operating amount and speed reduction rate;
• a motor driving state specification unit that specifies a target driving state of the motor to apply a required braking force to the drive shaft, in order to attain the setting of the target speed reduction rate;
• a control unit that controls the motor to be driven in the target driving state, so as to brake the vehicle;
• a torque converter having a mechanism that converts the output power to a combination of torque and revolving speed by utilizing a slip between two rotating members and transmits the converted power, and a lock mechanism that locks up relative rotations of the two rotating members to allow direct transmission of the output power, the mechanism and the lock mechanism being provided on a pathway for transmitting the braking force of the motor to the drive shaft;
• and
• a lock mechanism regulation unit that, when the observed operating amount of the accelerator unit is not greater than a predetermined value, regulates the lock mechanism to fall into a specific state for restricting the slip between the two rotating members of the torque converter.

A method of controlling a drive of a vehicle that is driven while regulating power output from a power source to a drive shaft through an operation of an accelerator unit, the vehicle being braked with a torque of a motor, comprising:

• measuring an operating amount of the accelerator unit;
• when the observed operating amount of the accelerator unit is not greater than a predetermined level, setting a target speed reduction rate of the vehicle corresponding to the observed operating amount, based on a preset relationship between operating amount and speed reduction rate;
• specifying a target driving state of the motor, in order to attain the setting of the target speed reduction rate;
• actuating the motor in the target driving state, so as to brake the vehicle;
• selecting one among a plurality of different gear ratios within a transmission interposed between the motor and the drive shaft in the course of applying braking force;
• selecting a target gear ratio to attain the target speed reduction rate with a torque of the motor;
• and
• controlling the transmission to effect the target gear ratio.

A vehicle that is driven while regulating power output from a power source to a drive shaft through an operation of an accelerator unit, the vehicle comprising:

• a motor that is capable of applying a braking force to the drive shaft;
• a detection unit that measures an operating amount of the accelerator unit;
• a target speed reduction rate setting unit that, when the measured operating amount of the accelerator unit is not greater than a predetermined level, sets a target speed reduction rate of the vehicle corresponding to the measured operating amount, based on a predetermined relationship between operating amount and speed reduction rate;
• a motor driving state specification unit that specifies a target driving state of the motor to apply a required braking force to the drive shaft, in order to attain the setting of the target speed reduction rate;
• a control unit that controls the motor to be driven in the target driving state, so as to brake the vehicle, wherein the predetermined relationship referred to by the target speed reduction rate setting unit gives a significantly greater speed reduction rate in a specific state practically corresponding to the operating amount of zero than speed reduction rates in residual states of the operating amount;
• a transmission that, in the course of applying a braking force, is capable of selecting one among a plurality of different gear ratios and is interposed between the motor and the drive shaft;
• a selection unit that selects a target gear ratio to attain the target speed reduction rate with a torque of the motor;
• and
• a change speed control unit that controls the transmission to effect the target gear ratio.

A vehicle that is driven while regulating power output from a power source to a drive shaft through an operation of an accelerator unit, the vehicle comprising:

• a motor that is capable of applying a braking force to the drive shaft;
• a detection unit that measures an operating amount of the accelerator unit;
• a target speed reduction rate setting unit that, when the measured operating amount of the accelerator unit is not greater than a predetermined level, sets a target speed reduction rate of the vehicle corresponding to the measured operating amount, based on a predetermined relationship between operating amount and speed reduction rate;
• a motor driving state specification unit that specifies a target driving state of the motor to apply a required braking force to the drive shaft, in order to attain the setting of the target speed reduction rate;
• and
• a control unit that controls the motor to be driven in the target driving state, so as to brake the vehicle;
• a torque converter having a mechanism that converts the output power to another combination of torque and revolving speed by utilizing a slip between two rotating members and transmits the converted power, and a lock mechanism that locks up relative rotations of the two rotating members to allow direct transmission of the output power, the mechanism and the lock mechanism being provided on a pathway for transmitting the braking force of the motor to the drive shaft;
• and
• a lock mechanism regulation unit that, when the measured operating amount of the accelerator unit is not greater that a predetermined value, regulates the lock mechanism to fall into a specific state for restricting the slip between the two rotating members of the torque converter.