Transmission structure

Patent metadata

Field	Value
Publication number	US-12352344-B2
Application number	US-202418592621-A
Country	US
Kind code	B2
Filing date	Mar 1, 2024
Priority date	Mar 30, 2023
Publication date	Jul 8, 2025
Grant date	Jul 8, 2025

Abstract

The problem is in providing a transmission structure which includes low gear and high gear transmission mechanisms and an HST and can improve the vehicle speed responsiveness at the time of switching between a low gear transmission state and a high gear transmission state. Solution: At the time of switching between low gear and high gear transmission states, the present invention creates an idling state in which the power transmission state from a drive source to a drive wheel is cut off, and calculates an excess vehicle speed HST gear ratio by adding an excess correction value, which is for changing the vehicle speed at the switching completion point in time in excess of the actual vehicle speed by a predetermined speed, to an actual vehicle speed ratio, which represents an HST gear ratio that causes the vehicle speed at the switching completion point in time to match the actual vehicle speed attained immediately before the completion of the switching, so as to operate an HST actuator using the excess vehicle speed HST gear ratio as a control target value during the idling state.

First claim

The invention claimed is:

1. A transmission structure comprising:
a low gear transmission mechanism that is capable of operatively transmitting a rotational power of a drive shaft, which is operatively coupled with a drive source, to a travel output shaft, which is operatively coupled with a drive wheel, at a predetermined low gear ratio;
a high gear transmission mechanism that operatively transmits the rotational power of the drive shaft to the travel output shaft at a high gear ratio for attaining a higher speed than at the low gear ratio;
a low gear clutch mechanism and a high gear clutch mechanism that engage and disengage power transmission of the low gear transmission mechanism and the high gear transmission mechanism, respectively;
a clutch actuator that switches operation states of the low gear clutch mechanism and the high gear clutch mechanism;
a Hydro Static Transmission (HST) that is capable of performing a continuously-variable gear shift of the rotational power in each of a low gear transmission state and a high gear transmission state which are created by the low gear transmission mechanism and the high gear transmission mechanism;
an HST actuator that operates an output adjusting member of the HST;
a gear shift operation member;
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 has HST control data, which is for obtaining an HST gear ratio corresponding to an operating position of the gear shift operation member and includes low gear HST control data used in the low gear transmission state and high gear HST control data used in the high gear transmission state,
wherein the control device
operates the HST actuator using, as a control target value, a reference HST gear ratio that is obtained by applying the operating position of the gear shift operation member to the low gear HST control data, while operating the clutch actuator so that the low gear transmission state is created when the vehicle speed is within a predetermined low gear range,
operates the HST actuator using, as the control target value, a reference HST gear ratio that is obtained by applying an operating position of the gear shift operation member to the high gear HST control data, while operating the clutch actuator so that the high gear transmission state is created when the vehicle speed is within a predetermined high gear range which is higher than the low gear range,
operates the clutch actuator so that an idling state in which both of the low gear and high gear clutch mechanisms are in a disengaged state is created in a period from a start to a completion of a switching operation between the low gear transmission state and the high gear transmission state, and
calculates an excess vehicle speed gear ratio by adding an excess correction value, which causes the vehicle speed at a point in time where the switching operation is completed to be changed in excess of an actual vehicle speed by a predetermined speed, to an actual vehicle speed gear ratio, which represents an HST gear ratio that causes the vehicle speed at the point in time where the switching operation is completed to match the actual vehicle speed that is attained immediately before the switching operation is completed, so as to operate the HST actuator using the excess vehicle speed gear ratio as the control target value in the idling state.

2. The transmission structure according to claim 1 ,
wherein the control device adds a load correction value corresponding to a traveling load to the reference HST gear ratio at the time of calculating the control target value of the HST actuator and stores the load correction value at the point in time where the gear switching operation is started as a carry-over load correction value, so as to use the carry-over load correction value as the excess correction value.

3. The transmission structure according to claim 2 ,
wherein the control device uses the carry-over load correction value as the excess correction value only in a case where the load correction value at the point in time where the gear switching operation is started exceeds a predetermined value.

4. The transmission structure according to claim 2 ,
wherein, after the gear switching operation is completed, at the time of calculating the control target value of the HST actuator in the transmission state after the gear switching, the control device adds the carry-over load correction value to the reference HST gear ratio while reducing the carry-over load correction value according to the passage of time.

5. The transmission structure according to claim 1 ,
wherein, as the excess correction value, the control device stores in advance a shift-up excess correction value, which is used for a shift-up from the low gear transmission state to the high gear transmission state, and a shift-down excess correction value, which is used for a shift-down from the high gear transmission state to the low gear transmission state.

6. The transmission structure according to claim 1 ,
wherein, at the time of the gear switching between the low gear transmission state and the high gear transmission state, the control device calculates, based on an HST acceleration rate immediately before the switching operation is started and a time period of the idling state, a virtual vehicle speed to be attained at the point in time where the gear switching operation is completed on an assumption that the transmission state before the gear switching had continued during the idling state, and uses, as the excess correction value, an absolute value of a difference between a virtual vehicle speed gear ratio for creating the virtual speed and the actual vehicle speed gear ratio for creating the actual vehicle speed that is attained immediately before the gear switching operation is completed.

7. Transmission structure according to claim 1 ,
wherein, of the low gear and the high gear clutch mechanisms, at least the clutch mechanism to be in an engaged state after the gear switching is a friction-plate-type which includes a driving-side friction plate and a following-side friction plate, and
the control device operates the clutch actuator so that, when the clutch mechanism to be in an engaged state after the gear switching is shifted from a disengaged state to the engaged state, the driving-side friction plate and the following-side friction plate frictionally engage with each other in a sliding manner.

8. The transmission structure according to claim 1 comprising:
a planetary gear mechanism including first to third elements, in which the third element functions as an HST input part that inputs an output rotational power 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

Assignees

• Kanzaki Kokyukoki Mfg Co Ltd

Inventors

• Takahashi Takumi
• Ogura Kohei
• Ito Fumiaki
• Inoue Tasuku

Classifications

• F16H61/462

  for achieving a target speed ratio · CPC title

• F16H61/0403

  Synchronisation before shifting · CPC title

• B60W30/188

  Controlling power parameters of the driveline, e.g. determining the required power · CPC title

• B60W30/19

  Improvement of gear change, e.g. by synchronisation or smoothing gear shift · CPC title

• F16H3/44

  using gears having orbital motion · CPC title