US 12,352,344 B2 · Transmission structure

a Hydro Static Transmission (HST) that is capable of performing a continuously-variable gear shift between a first HST gear ratio, at which a rotational power operatively input from a drive source is output as a rotational power in one of forward and reverse rotation, and a second HST gear ratio, at which the rotational power is output as a rotational power in the other one of the forward and reverse rotation, in accordance with an operating position of an output adjusting member;

an HST actuator that operates the output adjusting member of the HST;

a gear shift operation member;

a planetary gear mechanism including first to third elements, in which the third element functions as an HST input part that inputs the rotational power output from the HST;

an input-side first transmission mechanism that is capable of operatively transmitting the rotational power of the drive source to the first element at an input-side first gear ratio;

an input-side second transmission mechanism that is capable of operatively transmitting the rotational power of the drive source to the second element at an input-side second gear ratio;

friction-plate-type input-side first and second clutch mechanisms that engage and disengage power transmission of the input-side first and second transmission mechanisms, respectively;

a gear shift output shaft;

an output-side first transmission mechanism that is capable of operatively transmitting a rotational power of the second element to the gear shift output shaft at an output-side first gear ratio;

an output-side second transmission mechanism that is capable of operatively transmitting a rotational power of the first element to the gear shift output shaft at an output-side second gear ratio;

friction-plate-type output-side first and second clutch mechanisms that engage and disengage power transmission of the output-side first and second transmission mechanisms,

respectively;

a clutch actuator that switches operation states of the clutch mechanisms;

a vehicle speed sensor that directly or indirectly detects a vehicle speed;

an HST sensor that directly or indirectly detects an output rotation speed of the HST;

and

a control device that performs operation control of the HST actuator and the clutch actuator,

wherein the HST and the planetary gear mechanism are configured so that, in a first HMT transmission state where the input-side first and second clutch mechanisms are respectively in an engaged state and a disengaged state and the first element functions as a reference power input part that inputs a reference rotational power from the drive source and the second element functions as a composite power output part that outputs a composite rotational power toward the gear shift output shaft, an output rotational power of the second element becomes a zero speed when the HST is set to a zero speed gear ratio and the output rotational power of the second element is accelerated as the HST is shifted from the zero speed gear ratio toward the second HST gear ratio, and, in a second HMT transmission state where the input-side first and second clutch mechanisms are respectively in a disengaged state and an engaged state and the second element functions as the reference power input part and the first element functions as the composite power output part, an output rotational power of the first element is accelerated as the HST is shifted from the second HST gear ratio toward the first HST gear ratio,

the input-side first and second gear ratios are set so that a rotation speed of the second element that is attained when the HST is set to a first/second gear switching gear ratio in the first HMT transmission state is the same as a rotation speed of the second element caused by the rotational power transmitted via the input-side second transmission mechanism in the second HMT transmission state, and so that a rotation speed of the first element that is attained when the HST is set to the first/second gear switching gear ratio in the second HMT transmission state is substantially the same as a rotation speed of the first element caused by the rotational power transmitted via the input-side first transmission mechanism in the first HMT transmission state,

the output-side first and second gear ratios are set so that a rotation speed created in the gear shift output shaft when the HST is set to the first/second gear switching gear ratio in the first HMT transmission state is substantially the same as a rotation speed created in the gear shift output shaft when the HST is set to the first/second gear switching gear ratio in the second HMT transmission state,

the control device stores HST control data, which is for obtaining a reference HST gear ratio of the HST corresponding to an operating position of the gear shift operation member and includes first gear HST control data used in the first HMT transmission state and second gear HST control data used in the second HMT transmission state, and stores a load correction data, which is for obtaining a load correction value to be added to the reference HST gear ratio in accordance with a traveling load applied to the gear shift output shaft, and

the control device

operates the clutch actuator, in a first gear range where the vehicle speed is in a range from the zero speed to a predetermined first/second switching speed, so as to create the first HMT transmission state and then create a first gear transmission state in which the output-side first and second clutch mechanisms are respectively brought into an engaged state and a disengaged state, thereby operatively transmitting the rotational power of the second element to the gear shift output shaft,

operates the clutch actuator, in a second gear range where the vehicle speed is higher than the first/second switching speed, so as to create the second HMT transmission state and then create a second gear transmission state in which the output-side first and second clutch mechanisms are respectively brought into a disengaged state and an engaged state, thereby operatively transmitting the rotational power of the first element to the gear shift output shaft,

operates the HST actuator, when the vehicle speed is within the first gear range, using, as a control target value, a reference HST gear ratio obtained by applying the operating position of the gear shift operation member to the first gear HST control data, so that the HST is set to the zero speed gear ratio or a predetermined creep speed gear ratio in response to an operation on the gear shift operation member to a lowest speed position and the HST is shifted toward the second HST gear ratio in response to an acceleration operation on the gear shift operation member,

operates the HST actuator, when the vehicle speed is within the second gear range, using, as the control target value, a reference HST gear ratio obtained by applying the operating position of the gear shift operation member to the second gear HST control data, so that the HST is shifted toward the first HST gear ratio in response to an acceleration operation on the gear shift operation member,

operates the HST actuator, in a case where the traveling load applied to the gear shift output shaft exceeds a predetermined value, using, as the control target value, a load correction HST gear ratio obtained by adding the load correction value, which is obtained by applying the traveling load to the load correction data, to the reference HST gear ratio, and

calculates the load correction HST gear ratio, in a case where the control target value of the HST actuator includes the load correction value at the point in time where switching of the first gear transmission state and the second gear transmission state is started, by adding, in a direction that causes an excess change in the vehicle speed, an absolute value of the load correction value to the reference HST gear ratio, which is obtained by applying the operating position of the gear shift operation member to the HST control data, so as to operate the HST actuator using the load correction HST gear ratio as the control target value at the point in time where the switching is completed.

Transmission structure

Life of this patent

Transmission structure

Life of this patent

Abstract

Claims15