Clutching device of an automatic transmission
A clutching device of an automatic transmission includes: a clutch drum connected with a first rotation element, a clutch connected with the clutch drum and also a second rotation element, and a piston unit to operate the clutch. In particular, the piston unit includes: a first piston forming a first sealed space with the first rotation element and the clutch drum and moving toward the clutch to directly press the clutch by a hydraulic pressure supplied to the first space, a second piston forming a second sealed space with the first piston and the first rotation element, a spring retainer arranged on the first rotation element and forming a third sealed space with the first and second pistons and the first rotation element, a first return spring disposed between the first and second pistons, and a second return spring disposed between the spring retainer and the second piston.
1. A clutching device of an automatic transmission, the clutching device comprising:
a clutch drum connected with a first rotation element;
a clutch connected with the clutch drum and also connected with a second rotation element to connect or disconnect torque delivery between the first rotation element and the second rotation element; and
a piston unit configured to operate the clutch to connect the torque delivery between the first rotation element and the second rotation element,
wherein the piston unit comprises:
a first piston forming a first sealed space with the first rotation element and the clutch drum and configured to move toward the clutch to directly press the clutch by a hydraulic pressure supplied to the first sealed space through a first hydraulic line formed in the first rotation element;
a second piston forming a second sealed space with the first piston and the first rotation element;
a spring retainer arranged on the first rotation element and forming a third sealed space with the first and second pistons and the first rotation element;
a second hydraulic line formed in the first rotation element and configured to supply a hydraulic pressure to the third sealed space;
a first return spring disposed between the first piston and the second piston and configured to provide a first restoring force to the first and second pistons; and
a second return spring disposed between the spring retainer and the second piston and configured to provide a second restoring force to the spring retainer and the second piston.
2. The clutching device of claim 1 , wherein the piston unit further comprises a first stopper disposed on the first rotation element and arranged between the first piston and the second piston to limit a moving stroke of the second piston.
3. The clutching device of claim 2 , wherein the first stopper is formed as a snap ring fitted on the first rotation element and arranged between the first hydraulic line and the second hydraulic line and limits a return direction stroke of the second piston.
4. The clutching device of claim 1 , wherein:
the spring retainer is abutted by a second stopper in a direction toward the clutch to support the second return spring, and tightly contacts an exterior rim of the first piston by interposing a seal; and
the second hydraulic line is formed in the first rotation element at a location between the second piston and the spring retainer such that a compensation hydraulic pressure is formed in the third sealed space by receiving the hydraulic pressure through the second hydraulic line.
5. The clutching device of claim 4 , wherein the second stopper is formed as a snap ring fitted on the first rotation element.
6. The clutching device of claim 1 , wherein an exterior rim of the first piston is axially elongated in parallel with the clutch drum and slidably contacts the clutch drum by interposing a sealing.
7. The clutching device of claim 1 , wherein interior rims of the first and second pistons are slidably arranged on the first rotation element and contact the first rotation element by interposing a sealing, respectively.
8. The clutching device of claim 7 , wherein an exterior rim of the second piston is slidably contact an exterior rim of the first piston by interposing a sealing.
9. The clutching device of claim 1 , wherein
the first rotation element is an input shaft that receives an output torque of an engine; and
the second rotation element is one rotation element of three rotation elements of a planetary gear set.
10. The clutching device of claim 1 , wherein a third hydraulic line is formed in the first rotation element at a location between the first piston and the second piston and configured to supply a compensation hydraulic pressure to the second sealed space.
11. A clutching device of an automatic transmission, the clutching device comprising:
a clutch drum connected with an input shaft;
a clutch connected with the clutch drum and also connected with a rotation element of a planetary gear set and configured to connect or disconnect torque delivery between the input shaft and the rotation element; and
a piston unit configured to operate the clutch to connect or disconnect the torque delivery between the input shaft and the rotation element,
wherein the piston unit comprises:
a first piston forming a first sealed space with the input shaft and the clutch drum and configured to move toward the clutch to directly press the clutch by a hydraulic pressure supplied to the first sealed space through a first hydraulic line formed in the input shaft;
a second piston forming a second sealed space with the first piston and the input shaft;
a spring retainer arranged on the input shaft and forming a third sealed space with the first and second pistons and the input shaft;
a second hydraulic line formed in the input shaft and configured to supply a hydraulic pressure to the third sealed space;
a first stopper disposed on the input shaft and arranged between the first piston and the second piston to limit a moving stroke of the second piston;
a second stopper disposed on the input shaft and configured to abut the spring retainer;
a first return spring disposed between the first piston and the second piston and configured to provide a first restoring force to the first and second pistons; and
a second return spring disposed between the spring retainer and the second piston and configured to provide a second restoring force to the spring retainer and the second piston.
12. The clutching device of claim 11 , wherein the first stopper is formed as a snap ring fitted on the input shaft and arranged between the first hydraulic line and the second hydraulic line and limits a return direction stroke of the second piston.
13. The clutching device of claim 11 , wherein the second stopper is formed as a snap ring fitted on the input shaft.
14. The clutching device of claim 11 , wherein a third hydraulic line is formed in the input shaft at a location between the first piston and the second piston and configured to supply a compensation hydraulic pressure to the second sealed space.