A variable belt tensioner for an engine includes: a first damper; and a second damper connected to the first damper through a driver. The first damper, the second damper, and the driver causes a belt connected to a crankshaft pulley and a starter-generator pulley to have a first tensile strength when the engine including the crankshaft pulley starts, the first damper, the second damper, and the driver causes the belt to have a second tensile strength that is less than the first tensile strength when an electric power is generated by the starter-generator pulley, and the first damper, the second damper, and the driver causes the belt to have a third tensile strength that is less than the second tensile strength when the vehicle is accelerated by the engine.

A transmission speed control system for a walk-behind lawn mower includes a transmission, a transmission positioning assembly, and an electronic control unit. The transmission is tiltable about and operably engaged with a drive axle shaft. The transmission positioning assembly tilts the transmission between first and second angular positions. A belt tension between a drive belt and a transmission pulley of the transmission continuously increases from a minimum belt tension when the transmission is in the first angular position to a maximum belt tension when the transmission is in the second angular position. The rotational drive force exerted on the drive axle shaft by the transmission and a resulting driving speed of the lawn mower vary proportionally with the belt tension. The electronic control unit controls the transmission positioning assembly to tilt the transmission based on target and detected driving speeds.

The disclosure relates to a method for detecting belt slip of a belt drive driving a generator of an internal combustion engine, said belt drive having a belt tensioner that can be adjusted in operation and adjusts the pre-tensioning force of the belt according to the detected belt slip. According to said method, the rotational speed profile of the crankshaft is recorded during an angular window of the crankshaft of m.Math.360 degrees and an average value of the crankshaft rotational speed is formed from said rotational speed profile; temporally independently from the recording of the rotational speed profile of the crankshaft, the rotational speed course of the generator shaft is recorded during an angular window of the generator shaft of n.Math.u.sup.1.Math.360 degrees and an average value of the generator shaft rotational speed is formed from said rotational speed profile.

An automatic tensioning apparatus is provided that includes a tensioning drive unit having: a longitudinally extending stationary base frame with a plurality of guides extending between a lower portion and an upper portion, and a plurality of rotatable feed wheels axially secured at the lower portion, as well as a translatable drive frame slidably coupled to the plurality of guides with a drive assembly coupled to the drive frame, the drive assembly including a drive motor and a tensile member interface for engaging and rotationally translating a tensile member. The tensioning drive unit further including a plurality of drive frame actuators actuatable to move the drive frame between a bottom frame position and a top frame position, as well as a sensor for at least indirectly sensing the position of the drive frame along a longitudinal base frame axis.

A transmission speed control system for a walk-behind lawn mower includes a transmission, a transmission positioning assembly, and an electronic control unit. The transmission is tiltable about and operably engaged with a drive axle shaft. The transmission positioning assembly tilts the transmission between first and second angular positions. A belt tension between a drive belt and a transmission pulley of the transmission continuously increases from a minimum belt tension when the transmission is in the first angular position to a maximum belt tension when the transmission is in the second angular position. The rotational drive force exerted on the drive axle shaft by the transmission and a resulting driving speed of the lawn mower vary proportionally with the belt tension. The electronic control unit controls the transmission positioning assembly to tilt the transmission based on target and detected driving speeds.

Methods and systems are provided for tensioning a belt of a belt drive of an internal combustion engine. In one example, a movable tensioning means assigned to an active tensioner is provided, which applies a force to a belt of a belt drive, and the active tensioner is controlled such that a compression of a spring of the tensioner is at least countered, so that a movement of the tensioning means under the load of the belt is at least hindered. The belt is then excited to vibration in a contact zone between the belt and the movable tensioning means by use of a starter so that the tensioning means exposed to the force of the spring is moved further in the direction of the belt under expansion of the spring, whereby the belt is tensioned.

A variable belt tensioner for an engine includes: a first damper; and a second damper connected to the first damper through a driver. The first damper, the second damper, and the driver causes a belt connected to a crankshaft pulley and a starter-generator pulley to have a first tensile strength when the engine including the crankshaft pulley starts, the first damper, the second damper, and the driver causes the belt to have a second tensile strength that is less than the first tensile strength when an electric power is generated by the starter-generator pulley, and the first damper, the second damper, and the driver causes the belt to have a third tensile strength that is less than the second tensile strength when the vehicle is accelerated by the engine.

Methods and systems are provided for identifying degradation of a belt-driven integrated starter generator (BISG) active belt tensioner coupled to a vehicle engine. By using the monitored change in FEAD load to compare the actual state of the tensioner (either in retracted or extended state) relative to the commanded state, the presence of excess belt tension may be distinguished from the presence of insufficient belt tension. Timely diagnosis of a belt tensioner may be improve belt health and extend fuel economy benefits of a BISG system.

In one aspect the invention relates to a tensioner that is capable of precognitively anticipating when it is desirable to increase the tension in a belt or other endless drive element so as to prevent belt slip prior to events that would raise the risk of it.

A pressure regulator is in fluid communication with a supply inlet of a hydraulic tensioner to actively control fluid to the inlet of the hydraulic tensioner. By actively controlling the pressure regulator based on engine conditions and thus the oil pressure being fed to the hydraulic tensioner, the oil pressure to the hydraulic tensioner may be reduced at low engine speeds, increasing the efficiency of the timing system, or allowing full oil pressure at high engine speeds and low engine temperature.