Blade and ground speed control system

A lawn cutting machine comprising:

• a motor having an output shaft;
• a rotatable cutting blade rotationally fixed on a blade shaft;
• a variable speed torque transmitting mechanism operably disposed between said output shaft and said blade shaft, said torque having a variable rotational speed ratio between said blade shaft and said output shaft;
• a variable speed transmission operably coupled to said output shaft and having a variable speed driven shaft, said motor, output shaft, transmission and driven shaft together defining a drive train;
• a driven wheel coupled with said driven shaft and engagable with the ground for propelling said machine at a ground speed;
• an electronic control unit, said control unit having a speed ratio change output operably coupled to said torque transmitting mechanism, said control unit having a speed change output operably coupled to said transmission;
• a blade speed sensor having an output connected to said control unit with a blade speed signal representative of the speed of said rotatable cutting blade;
• a ground speed sensor having an output connected to said control unit with a ground speed signal representative of the ground speed of said machine;
• whereby the blade speed signal is monitored and one or both of the speed of said driven shaft and the rotational speed ratio of the blade speed are raised when the blade speed falls below a predetermined rate.

A lawn cutting machine comprising:

• a motor having an output shaft;
• a rotatable cutting blade rotationally fixed on a blade shaft;
• a variable speed torque transmitting mechanism operably disposed between said output shaft and said blade shaft, said torque having a variable rotational speed ratio between said blade shaft and said output shaft;
• a variable speed transmission operably coupled to said output shaft;
• a driven wheel operably coupled to said transmission, whereby said machine may be propelled;
• an electronic control unit, said control unit having a speed ratio change output operably coupled with said torque transmitting mechanism, said control unit having a speed change output operably coupled with said transmission, said control unit programmed with a quality cut algorithm and a quick cut algorithm;
• a blade speed sensor having an output to said control unit with a signal representative of the speed of said rotatable cutting blade;
• a ground speed sensor having an output to said control unit with a signal representative of the ground speed of said machine;
• and
• a user-operable input device having an output connected to said electronic control unit to select between said quality cut algorithm and said quick cut algorithm;
• whereby:
• operating said machine in accordance with said quality cut algorithm includes said control unit monitoring the speed of said cutting blade and adjusting one of the ground speed and the rotational speed ratio between said output shaft and said blade shaft to raise the blade speed when the blade speed falls below a predetermined blade speed value;
• and
• operating said machine in accordance with said quick cut algorithm includes said control unit monitoring the ground speed of said machine and adjusting one of the ground speed and the rotational speed ratio between said output shaft and said blade shaft to raise the ground speed when the ground speed falls below a selected ground speed value.

A lawn cutting machine comprising:

• an internal combustion engine adapted to run at a substantially constant engine speed and having an output shaft;
• a rotatable cutting blade rotationally fixed on a blade shaft;
• a torque transmitting means operably disposed between said output shaft and said blade shaft, said torque transmitting means transferring rotational motion from said output shaft to said blade shaft and selectively adjusting a rotational speed ratio between said blade shaft and said output shaft;
• a transmission operably coupled to said output shaft and having a variable speed driven shaft;
• a driven wheel coupled with said driven shaft and engagable with the ground for propelling said machine at a ground speed;
• an electronic control unit means, said control unit means operably coupled with said torque transmitting mechanism for adjusting the rotational speed ratio between said blade shaft and said output shaft, said control unit means operably coupled with said transmission and adjusting the speed of said driven shaft;
• a blade speed sensor providing said control unit means with a blade speed signal representative of the speed of said rotatable cutting blade;
• a ground speed sensor providing said control unit means with a ground speed signal representative of the ground speed of said machine;
• and
• wherein said control unit means monitors the blade speed signal and adjusts one of the speed of said driven shaft and the rotational speed ratio to maintain the blade speed at a substantially constant blade speed value.

A method of cutting grass, said method comprising:

• providing a lawn cutting machine having a user-operable input device, a motor with an output shaft, a rotatable cutting blade and a driven shaft with a driven wheel coupled thereto, said output shaft operably coupled to said cutting blade and said driven shaft, said driven wheel engagable with the ground for propelling said machine at a ground speed;
• monitoring the speed of said cutting blade;
• monitoring the ground speed of said machine;
• and
• selecting one of a quality cut algorithm and a quick cut algorithm based upon a user input and operating said machine in accordance with the selected algorithm wherein operating said machine in accordance with said quality cut algorithm includes adjusting one of the speed of said cutting blade and the ground speed to raise said blade speed when the speed of said cutting blade falls below a predetermined blade speed value and wherein operating said machine in accordance with said quick cut algorithm includes adjusting one of the speed of said cutting blade and the ground speed to raise said ground speed when the ground speed falls below a selected ground speed value.

A method of cutting grass, said method comprising:

• providing a lawn cutting machine having an internal combustion engine with an engine output shaft, a rotatable cutting blade and a driven shaft with a driven wheel coupled thereto, said engine output shaft operably coupled to said cutting blade and said driven shaft, said driven wheel engagable with the ground for propelling said machine at a ground speed;
• operating said engine at a substantially constant engine speed;
• monitoring the speed of said cutting blade;
• monitoring the ground speed of said machine;
• adjusting one of the speed of said cutting blade and said ground speed when one of the speed of said cutting blade and said ground speed falls below a predetermined value without directly adjusting the rotational speed of said engine output shaft.