Is the clutch engaged or disengaged when pressed down?

[Nadine]

Pressing the clutch pedal disengages it, aiming to separate the clutch pressure plate from the clutch disc, thereby disconnecting the engine from the transmission. During startup, when the clutch is not pressed, the transmission input shaft rotates with the engine in neutral position, causing the transmission to idle. When attempting to shift gears, the first gear rotates with the engine, preventing the main gear from meshing with the secondary gear, making gear engagement impossible. Only by separating the two can gear engagement occur. The functions of the clutch are as follows: 1. Ensuring smooth vehicle startup: This is the primary function of the clutch. Before starting the car, the engine must first be started. During startup, the vehicle accelerates from a complete standstill. If the drivetrain (which connects the entire vehicle) is rigidly linked to the engine, engaging the transmission would cause the car to jerk forward suddenly but not start moving. This is because the transition from standstill to sudden movement generates significant inertial force, creating a substantial resistance torque on the engine. Under this inertial resistance torque, the engine's speed drops sharply below the minimum stable speed (typically 300-500 RPM), causing the engine to stall and fail to operate, thus preventing the car from starting. 2. Enabling smooth gear shifts: During driving, to adapt to changing conditions, the drivetrain frequently needs to switch between different gears. Shifting in a manual transmission typically involves moving gears or other shifting mechanisms to disengage the current gear pair and engage a new one. Before shifting, the clutch pedal must be pressed to interrupt power transmission, facilitating the disengagement of the current gear pair and allowing the new gear pair to synchronize speeds gradually. This significantly reduces engagement shock, ensuring smooth gear shifts. 3. Preventing drivetrain overload: During emergency braking, without a clutch, the engine would rapidly decelerate due to its rigid connection with the drivetrain. This would generate substantial inertial torque (potentially exceeding the engine's maximum operating torque) in all moving parts, subjecting the drivetrain to loads beyond its capacity and causing component damage. The clutch mitigates this risk by allowing relative movement between its driving and driven parts, absorbing the excess torque.