Automatic transmission and control method of automatic transmission

Patent metadata

Field	Value
Publication number	US-10393229-B2
Application number	US-201715440980-A
Country	US
Kind code	B2
Filing date	Feb 23, 2017
Priority date	Feb 29, 2016
Publication date	Aug 27, 2019
Grant date	Aug 27, 2019

Abstract

A dual clutch automatic transmission includes a one-way clutch provided in a driving force transmission path that establishes a certain gear ratio in a first set of gear ratios. A driving transmission direction of the one-way clutch is set such that a rotation inputted from a wheel side to an output member in a predetermined rotational direction is transmitted to the input shaft. The predetermined rotational direction corresponds to a backward movement of a vehicle. On condition that the vehicle has stopped, backward movement prevention control of causing the switching mechanism to engage a transmission gear for another gear ratio in the first set with the input shaft can be executed.

First claim

What is claimed is:

1. An automatic transmission comprising:
a first transmission mechanism to which a driving force of a driving source is input through a first clutch and which is configured to switch driving force transmission paths to an output member to establish a first set of gear ratios;
a second transmission mechanism to which the driving force of the driving source is input through a second clutch and which is configured to switch driving force transmission paths to the output member to establish a second set of gear ratios; and
a control unit,
wherein a one-way clutch is provided in a driving force transmission path that establishes a first certain gear ratio in the first set,
the first transmission mechanism comprises:
an input shaft to which the driving force of the driving source is input through the first clutch;
a first transmission gear provided on the input shaft and configured to establish the first certain gear ratio;
a plurality of second transmission gears provided on the input shaft and configured to establish remaining gear ratios in the first set; and
a switching mechanism configured to perform engagement and disengagement between the input shaft and the plurality of second transmission gears,

a driving transmission direction of the one-way clutch is set such that a rotation inputted from a wheel side to the output member in a predetermined rotational direction is transmitted to the input shaft, the predetermined rotational direction corresponding to a backward movement of a vehicle,
the switching mechanism comprises:
a dog clutch; and
an actuator configured to operate the dog clutch,

the control unit can execute backward movement prevention control of causing the switching mechanism to engage a third transmission gear that is one of the plurality of second transmission gears with the input shaft on condition that the vehicle has stopped, and
after the third transmission gear engages with the input shaft, the control unit instructs the switching mechanism to disengage the third transmission gear from the input shaft immediately regardless of whether or not the vehicle starts.

2. The transmission according to claim 1 , wherein the control unit can execute the backward movement prevention control on condition that the vehicle has stopped on a climbing hill.

3. The transmission according to claim 1 , wherein the control unit can execute the backward movement prevention control without using, as a condition, a tilt of a terrain on which the vehicle stops.

4. The transmission according to claim 1 , further comprising a sensor configured to detect a shift position,
wherein the control unit can execute the backward movement prevention control on condition that selection of a parking range is not detected as the shift position.

5. The transmission according to claim 1 , wherein an output of the actuator has a magnitude that makes disengagement of the dog clutch difficult in a case in which the backward movement prevention control is executed when the vehicle has stopped on the climbing hill.

6. The transmission according to claim 1 , wherein the gear ratios in the first set are odd-numbered speed gear ratios, and
the gear ratios in the second set are even-numbered speed gear ratios.

7. The transmission according to claim 5 , wherein the first certain gear ratio is a 1st-speed gear ratio, and
the third transmission gear is configured to establish a 3rd-speed gear ratio.

8. The transmission according to claim 1 , further comprising a countershaft provided in parallel to the input shaft,
wherein the output member is provided on the countershaft, and
a gear configured to mesh with the first transmission gear is provided on the countershaft through the one-way clutch.

9. A control method of an automatic transmission which comprises:
a first transmission mechanism to which a driving force of a driving source is input through a first clutch and which is configured to switch driving force transmission paths to an output member to establish a first set of gear ratios; and
a second transmission mechanism to which the driving force of the driving source is input through a second clutch and which is configured to switch driving force transmission paths to the output member to establish a second set of gear ratios,
wherein a one-way clutch is provided in the driving force transmission path that establishes a first certain gear ratio in the first set,
the first transmission mechanism comprises:
an input shaft to which the driving force of the driving source is input through the first clutch;
a first transmission gear provided on the input shaft and configured to establish the first gear ratio;
a plurality of second transmission gears provided on the input shaft and configured to establish remaining gear ratios in the first set; and
a switching mechanism configured to perform engagement and disengagement between the input shaft and the plurality of second transmission gears,

a driving transmission direction of the one-way clutch is set such that a rotation inputted from a wheel side to the output member in a predetermined rotational direction is transmitted to the input shaft, the predetermined rotational direction corresponding to a backward movement of a vehicle, and
the switching mechanism comprises:
a dog clutch; and
an actuator configured to operate the dog clutch,

the control method comprising:
determining whether a predetermined condition including at least a stop of the vehicle is met;
upon determining that the predetermined condition is met, causing the switching mechanism to engage a third transmission gear that is one of the plurality of second transmission gears with the input shaft, and

after the third transmission gear engages with the input shaft, instructing the switching mechanism to disengage the third transmission gear from the input shaft immediately regardless of whether or not the vehicle starts.

Assignees

• Honda Motor Co Ltd

Inventors

• Muto Akio
• Taka Shohei
• Murasawa Hiroki

Classifications

• F16H2312/04

  Holding or hillholding · CPC title

• F16H2061/205

  Hill hold control, e.g. with torque converter or a friction device slightly engaged to keep vehicle stationary · CPC title

• F16H61/20

  Preventing gear creeping {; Transmission control during standstill, e.g. hill hold control} · CPC title

• F16H61/0059

  Braking of gear output shaft using simultaneous engagement of engaging means, e.g. clutches or brakes, applied for different gear ratios · CPC title

• F16H2200/0065

  the gear ratios comprising nine forward speeds · CPC title