Provided is an opposed-piston engine which attains high output, ensures combustion toughness, and includes a simplified configuration of a crankshaft counter-rotation synchronization mechanism which rotates crankshafts in engine units in opposite directions. An opposed-piston engine 10 of the present invention includes a first engine unit 11 and a second engine unit 21. The first engine unit 11 and the second engine unit 21 respectively include a first cylinder 12 and a second cylinder 22 independent of each other. In addition, a first valve driving mechanism 19 and a second valve driving mechanism 20 which control valves also function as a crankshaft counter-rotation synchronization mechanism 29 which rotates a first crankshaft 14 of the first engine unit 11 and a second crankshaft 24 of the second engine unit 21 in the opposite directions.

Reducing engagement noise in a chain drive or belt drive for an internal combustion engine having a crankshaft having a driving sprocket and at least one shaft having a first driven sprocket and a second driven sprocket, where the driving sprocket and at least one of the first driven sprocket and the second driven sprocket contain a pattern of pitch radii such that the radial variation of the pitch radii excite tensions at non-prevalent orders in a drive system of the internal combustion engine. The non-prevalent engine cycle orders excited by each of the driving sprocket, the first driven sprocket and the second driven sprocket are different.

A valve drive for an internal combustion engine may include a cam shaft, at least one cam follower, at least one adjusting device, and at least one control shaft. The cam shaft may include at least one cam group that may include a first cam and a second cam The at least one adjusting device may include a first adjustable engagement element and a second adjustable engagement element. The at least one control shaft may include at least one control cam group that may include a first control cam and a second control cam. The first control cam may include a cam lobe corresponding to the first engagement element and the second control cam may include a cam lobe corresponding to the second engagement element. The at least one control shaft may be rotatable about a longitudinal axis between a starting position and a rotational position.

A valve drive for an internal combustion engine may include a camshaft, at least one cam follower, at least one adjusting device, and at least one control shaft. The camshaft may include at least one cam group including a first cam and a second cam. The at least one adjusting device may include a first engagement element and a second engagement element. The at least one control shaft may include at least one control cam group including a first control cam and a second control cam. The at least one control shaft may rotate such that at least one stop region of the first control cam adjusts the first engagement element from the basic position into the switching position and at least one stop region of the second control cam adjusts the second engagement element from the basic position into the switching position one after the other.

The present disclosure employs a pair of camshafts for intake valves. A first phase controller is installed at a first end of the first intake camshaft connecting to the crankshaft. A second phase controller is installed at a second end of the first intake camshaft connecting to the second intake camshaft. Each phase controller can adjust phase angle accordingly to modify intake valve timing and intake valve lift. This set up is duplicated for the exhaust valves to modulate exhaust valve timing and exhaust valve lift. First and second camshafts are connected via a series of levers, which merges the rotations of both camshafts into one. The phase controllers can be differential gear sets, epicyclical gear sets, or a combination thereof.

Methods and systems are provided for a cam drive system of an engine. In one example, a front end of an engine includes an idler gear assembly including an idler gear and idler pulley, the idler gear in meshing engagement with a first end of a crankshaft and the idler pulley coupled to and sharing a rotational axis with the idler gear. The front end of the engine may further include first and second camshaft pulleys positioned vertically above the idler gear assembly and a cam drive belt contacting each of the first and second camshaft pulleys and the idler pulley.

A torsion spring assembly according to the invention includes a torsion spring having a cylindrical spring body of wound spring wire and with a plurality of torsion spring windings, and having first and second torsion spring ends for taking up forces in a direction of rotation, and a damping spring abutting the torsion spring on the inner side and having a cylindrical spring body of wound spring wire and with a plurality of damping spring windings, and having first and second damping spring wire ends, wherein the damping spring windings have their outer sides extending partially into the space formed between two respectively adjacent torsion spring windings and abutting in particular rounded, round or beveled inner abutment areas of respectively adjacent torsion spring windings with substantially radially outwardly directed bias.

An endless band drive system having a variable center distance between the drive pulley and the driven pulley also has a rotatable control shaft and an endless band guide, where the guide is positioned by the rotatable control shaft for maintaining a slackless endless band with change of pulley center distance. Rotation of the control shaft pivots the endless band guide thereby maintaining a slackless endless band with change of the pulley center distance. Preferably, the rotatable control shaft also provides means for adjusting the center distance between the drive pulley and the driven pulley. The present invention provides a slackless endless band system for a variable compression ratio engine having a variable center distance between the drive pulley mounted on the crankshaft and the driven pulley mounted on the camshaft. The system provides slackless operation of the endless band at two or more compression ratio values.

A camshaft phaser arrangement configured for a concentric camshaft assembly having an inner camshaft and an outer camshaft is provided. The camshaft phaser arrangement can facilitate independent phasing of intake and exhaust valves. The camshaft phaser arrangement includes a first driven wheel and a second driven wheel, both configured to be driven by a driving wheel. A first camshaft phaser is connected to the first driven wheel and configured to be connected to either the inner or outer camshaft. A second camshaft phaser is connected to the second driven wheel and configured to be connected to either the inner or outer camshaft which is not connected to the first driven wheel. A motion transfer assembly can connect the second camshaft phaser to the concentric camshaft assembly. One or both of the camshaft phasers can be an electric camshaft phaser or a hydraulic camshaft phaser.

A sound reducing device (30) for an internal combustion engine (1, 101) comprises a chamber forming member (33) defining a sound reducing chamber (32) having a prescribed column length jointly with a belt cover, and the sound reducing chamber communicates with the belt chamber via an opening (31), and the opening opposes a part of a timing belt passed around the cam pulley.