Engagement device and automatic transmission
A translational force Fh to one side in a rotational axis direction is caused to act from a hydraulic piston to a sleeve when an engaged stage between an engagement tooth and an engaged tooth is maintained, so that translation of the sleeve to the other side in the rotational axis direction and consequent disengagement of the engagement tooth and the engaged tooth can be prevented. Therefore, the engaged state between the engagement member and the engaged member can be stably maintained regardless of the condition of the torque acting from the drive source to the engagement member.
1. An engagement device comprising:
a movable element in which an engagement section is provided;
an engagement element in which a support section that supports the movable element is provided; and
an engaged element in which an engaged section is provided, wherein
a torque from a drive source acts on the engagement element or the engaged element,
the support section supports the movable element in a manner such that the movable element moves to one side in a rotational axis direction corresponding to a relative rotation of the engagement element in a predetermined direction with respect to the movable element,
the engagement device further comprises an engagement force generation device that causes a force to the one side in the rotational axis direction to act on the movable element,
when the movable element is at a predetermined engagement position in the rotational axis direction, the engagement section engages the engaged section and movement of the movable element to the one side in the rotational axis direction with respect to the predetermined engagement position is restrained by a restraining section, and
the engagement force generation device causes, when a state of engagement between the engagement section and the engaged section is maintained, the force to the one side in the rotational axis direction to act on the movable element so that the movable element does not move to the other side in the rotational axis direction with respect to the predetermined engagement position.
2. The engagement device according to claim 1 , wherein
the support section is provided on the engagement element in an inclined manner in the predetermined direction from the one side in the rotational axis direction toward the other side with respect to the rotational axis direction, and
when the state of engagement between the engagement section and the engaged section is maintained, the force to the one side in the rotational axis direction that the engagement force generation device causes to act on the movable element is greater than Tn×tan (θ)/r, wherein Tn represents a torque in a direction opposite from the predetermined direction acting on the engagement element, r represents a radius of the support section, and θ represents an inclination angle of the support section with respect to the rotational axis direction.
3. The engagement device according to claim 2 , wherein
when the state of engagement between the engagement section and the engaged section is maintained, a torque in the direction opposite from the predetermined direction is caused to act on the engagement element by a resistive torque of the drive source, and
when the state of engagement between the engagement section and the engaged section is maintained, the force to the one side in the rotational axis direction that the engagement force generation device causes to act on the movable element is greater than ρ×Tr×tan (θ)/r, wherein Tr represents the resistive torque of the drive source, and ρ represents a torque ratio between the engagement element and the drive source.
4. The engagement device according to claim 2 , further comprising:
a disengagement force generation device that causes a force to the other side in the rotational axis direction to act on the movable element, wherein
when the state of engagement between the engagement section and the engaged section is maintained, the force to the one side in the rotational axis direction that the engagement force generation device causes to act on the movable element is greater than Fs+Tn×tan (θ)/r, wherein Fs represents a force to the other side in the rotational axis direction that the disengagement force generation device causes to act on the movable element.
5. The engagement device according to claim 3 , further comprising:
a disengagement force generation device that causes a force to the other side in the rotational axis direction to act on the movable element, wherein
when the state of engagement between the engagement section and the engaged section is maintained, the force to the one side in the rotational axis direction that the engagement force generation device causes to act on the movable element is greater than Fs+Tn×tan (9)/r, wherein Fs represents a force to the other side in the rotational axis direction that the disengagement force generation device causes to act on the movable element.
6. An automatic transmission which gear-changes a motive power from a drive source and outputs the motive power, and in which a gear stage can be selected from among a plurality of gear stages, comprising:
a brake device that allows or restrains rotation of a rotational member to which a torque from the drive source acts, wherein
the brake device restrains the rotation of the rotational member at a first gear stage among the plurality of gear stages and allows the rotation of the rotational member at a second gear stage among the plurality of gear stages,
the brake device is the engagement device according to claim 1 , one of the engagement element and the engaged element is connected to the rotational member, and a rotation of the other of the engagement element and the engaged element is fixed, and
when the first gear stage is maintained, the engagement force generation device causes the force to the one side in the rotational axis direction to act on the movable element such that the movable element does not move to the other side in the rotational axis direction with respect to the predetermined engagement position.