Compressed-air engine with integrated active chamber and active distribution with balanced valve

An active chamber engine operating according to a three-phase thermodynamic cycle comprising:

• an isobaric and isothermal transfer phase;
• a polytropic expansion phase with work;
• an exhaust phase at ambient pressure;
• the engine comprising
• at least one cylinder fed with a gas under pressure contained in a high-pressure storage tank,
• at least one piston which is slidably mounted in the cylinder,
• a crankshaft driven by the piston by means of a conventional connecting rod-crank device,
• a cylinder head which closes the volume of the cylinder, at the cylinder's upper part, which is swept by the piston, and which comprises at least one intake duct into which flows a flow of gas under pressure for filling the cylinder an intake for the gas under pressure above the piston, and at least one exhaust orifice and one exhaust duct, the cylinder head being arranged in such a way that, when the piston is at top dead centre, a residual volume contained between the piston and the cylinder head is, by construction, reduced to minimum clearances allowing operation of the cylinder,
• at least one intake valve which cooperates in a sealing manner with a valve seat formed in the cylinder head and which delimits an intake orifice, wherein:
• the volume of the cylinder swept by the piston is divided into two distinct parts, a first part of which constitutes an active chamber which is included in the cylinder and a second part of which constitutes an expansion chamber,
• under the continuous thrust of the gas under pressure admitted into the cylinder, at constant working pressure, the volume of the active chamber increases producing work corresponding to the isobaric and isothermal transfer phase of a thermodynamic cycle of operation,
• the admission of the gas under pressure into the cylinder is closed as soon as the maximum volume of the active chamber is reached, the quantity of the gas under pressure contained in said active chamber then expanding by pushing back the piston over the second part of the piston's stroke which determines the expansion chamber, producing work corresponding to the polytropic expansion phase of the thermodynamic cycle of operation,
• the piston having reached bottom dead centre, the exhaust orifice is then opened to carry out the exhaust phase of the thermodynamic operating cycle during the upstroke of the piston over the piston's entire stroke to top dead centre,
• a torque and an engine speed are controlled by opening and closing the intake valve, by opening the intake valve at the top dead centre of the piston stroke, and by allowing a duration and/or an angular sector of the intake as well as a cross-sectional area of an intake opening to be varied by closing the intake valve in order, depending on the pressure of the gas under pressure in the storage tank and on the pressure at the end of the expansion phase, to determine the quantity of gas under pressure admitted as well as the volume of a working chamber,
• wherein:
• a) the intake valve is mounted so as to be axially displaceable between a lower closed position, in which the intake valve bears in a sealed manner on the intake valve's valve seat, and an upper open position,
• b) in the intake valve's opening direction, the intake valve moves axially in the direction opposite to that of the flow of gas under pressure filling the cylinder,
• c) in the intake valve's closed position, the intake valve is held closed on the intake valve's seat by a return spring,
• d) the axial forces acting on the intake valve resulting from the pressure in the intake duct and in the cylinder are permanently balanced,
• e) the engine has a pneumatic actuator for controlling the opening of the intake valve, at the top dead centre of the stroke of the piston, in order to cause the intake valve to lift off from the intake valve's seat to allow the establishment of the intake pressure in the active chamber, the intake valve then travelling a full opening stroke against the force exerted by the return spring,
• f) the pneumatic actuator has an actuator cylinder and an actuator piston which is connected to the intake valve and which delimits a pilot chamber which is connected to a low-pressure gas source,
• g) the engine has a channel which connects the low-pressure gas source to the pilot chamber, and a first controlled valve for admitting low pressure gas into the pilot chamber,
• i) the engine has a channel for controlling the closing of the intake valve which connects the pilot chamber to the open air or to an energy recovery system, and a second controlled valve for emptying the pilot chamber, and
• wherein the low-pressure gas source is a pressure reducer, an intake of which is connected to the high-pressure storage tank or to the intake duct, and an outlet of which is connected to the pilot chamber.