Methods for controlling vacuum within a brake booster by modifying powertrain operation include determining an intake manifold vacuum in response to actuation of a brake pedal. Increasing the intake manifold vacuum if the brake booster vacuum is less than a desired brake booster vacuum. In some embodiments, the transmission is downshifted to increase engine speed and intake manifold vacuum. In other embodiments, engine torque is reduced to increase intake manifold vacuum and the torque of the electric machine is increased to maintain a constant output torque.

An autolift-resistant piston assembly is provided for an air compressor. The piston assembly comprises an unloader piston having an interior chamber. The piston assembly further comprises a first coil spring for biasing the unloader piston to a loaded position when the piston assembly is installed in the air compressor. The piston assembly also comprises an inner member disposed in the interior chamber of the unloader piston and including (i) a body portion, and (ii) a tapered end portion extending from the body portion and facing an unloader air passage of the air compressor when the piston assembly is installed in the air compressor.

A hydraulic unit for a vehicle brake apparatus having a master cylinder and a wheel cylinder includes a housing formed with a pipe line connecting between the master cylinder and the wheel cylinder, a pump disposed in the housing for sucking and discharging a brake fluid to boost pressure of the brake fluid, and a reservoir piston disposed in a hole formed in the housing so as to be movable slidably back and forth, the reservoir piston partitioning a reservoir chamber within the hole for temporarily storing the brake fluid discharged from the wheel cylinder. The hydraulic unit further includes a cover disposed in the hole to close one end on an atmospheric side of the hole, the cover being formed with a fluid reservoir chamber for storing the brake fluid leaking from the pump.

A hydraulic unit for a vehicle brake apparatus having a master cylinder and a wheel cylinder includes a housing formed with a pipe line connecting between the master cylinder and the wheel cylinder, a pump disposed in the housing for sucking and discharging a brake fluid to boost pressure of the brake fluid, and a reservoir piston disposed in a hole formed in the housing so as to be movable slidably back and forth, the reservoir piston partitioning a reservoir chamber within the hole for temporarily storing the brake fluid discharged from the wheel cylinder. The hydraulic unit further includes a cover disposed in the hole to close one end on an atmospheric side of the hole, the cover being formed with a fluid reservoir chamber for storing the brake fluid leaking from the pump.

A vehicle control apparatus assists a braking operation by using negative pressure in a negative pressure chamber generated by rotation of an internal combustion engine, automatically stops or restarts the engine if a first or second condition is satisfied, respectively. The apparatus determines whether a braking operation is performed, detects the rotational speed of the engine and the negative pressure in the negative pressure chamber using a negative pressure sensor. When a state has continued over a predetermined time while no braking operation has been detected, and the rotational speed has been over a threshold, the apparatus temporarily determine whether the sensor is abnormal, based on the negative pressure. When the sensor has been temporarily determined abnormal for a predetermined number of times, the abnormality is certainly determined to inhibit automatic stopping of the engine. The predetermined time may be changed depending whether the state has continued.

A vehicle control apparatus assists a braking operation by using negative pressure in a negative pressure chamber generated by rotation of an internal combustion engine, automatically stops or restarts the engine if a first or second condition is satisfied, respectively. The apparatus determines whether a braking operation is performed, detects the rotational speed of the engine and the negative pressure in the negative pressure chamber using a negative pressure sensor. When a state has continued over a predetermined time while no braking operation has been detected, and the rotational speed has been over a threshold, the apparatus temporarily determine whether the sensor is abnormal, based on the negative pressure. When the sensor has been temporarily determined abnormal for a predetermined number of times, the abnormality is certainly determined to inhibit automatic stopping of the engine. The predetermined time may be changed depending whether the state has continued.

An internal combustion engine includes an intake camshaft, a vacuum pump, an oil pump, and an oil feeding passage serving as an oil supplying path. The vacuum pump includes a rotor and a housing. The vacuum pump is formed with a negative pressure chamber that generates a negative pressure, and an oil path connected to the negative pressure chamber. An atmosphere communication hole for supplying air to the negative pressure chamber through the oil feeding passage and the oil path when the vacuum pump is stopped is arranged in the oil feeding passage. The atmosphere communication hole communicates the negative pressure chamber and the atmosphere before an amount of oil in the housing exceeds an allowable oil amount when the vacuum pump is stopped.

Devices for producing vacuum using the Venturi effect are disclosed that have a motive passageway converging toward a suction chamber, a discharge passageway diverging away from the suction chamber, and a suction passageway, all of which are in fluid communication with the suction chamber. The motive passageway has a single entrance, and subdivides downstream thereof into a plurality of subpassageways, one each leading to one of the plurality of motive exits, which are spaced apart from a discharge entrance of the discharge passageway to define a Venturi gap. The fletch having a plurality of ribs extending between an exterior surface of the generally conically-shaped main body thereof and an interior surface of the motive passageway is disposed in the motive passageway. The ribs divide the motive passageway into the plurality of sub-passageways, each converging fluid flow over the exterior surface thereof toward one of the plurality of motive exits.

An arrangement of motor vehicle units includes a vacuum pump, a power brake unit, a pump which pumps a hydraulic fluid with a control pressure, and a control valve. The vacuum pump comprises a pump rotor, a coupling element, a control connection, a coupling arrangement switchable by the control connection to lock/unlock the coupling element with the pump rotor, and a suction connection. The power brake unit comprises a negative pressure chamber connected with the suction connection. The control valve, when unlocked, switches the control pressure of the hydraulic fluid through to the control connection to unlock. The control valve comprises an actuator acted on by a pressure of the negative pressure chamber which switches the control pressure through to the control connection if the pressure in the negative pressure chamber is greater than a threshold pressure so that the switchable control valve is switched into its unlocked state.

An arrangement of motor vehicle units includes a vacuum pump, a power brake unit, a pump which pumps a hydraulic fluid with a control pressure, and a control valve. The vacuum pump comprises a pump rotor, a coupling element, a control connection, a coupling arrangement switchable by the control connection to lock/unlock the coupling element with the pump rotor, and a suction connection. The power brake unit comprises a negative pressure chamber connected with the suction connection. The control valve, when unlocked, switches the control pressure of the hydraulic fluid through to the control connection to unlock. The control valve comprises an actuator acted on by a pressure of the negative pressure chamber which switches the control pressure through to the control connection if the pressure in the negative pressure chamber is greater than a threshold pressure so that the switchable control valve is switched into its unlocked state.