Walk-behind power equipment unit having all-wheel drive control system
A control system for controlling engagement of a first and second transmission of an all-wheel drive (AWD) walk-behind power equipment unit such as a lawn mower. The control system may include a mechanical load balancer to split an input drive force vector into two output force vectors. These two forces act upon associated first and second connection elements coupled to the first and second transmissions, respectively. One transmission may include a resistance element selected to sequence engagement of the first and second transmissions so that both transmissions begin driving their respective wheels at or near the same time even when the wheels associated with one transmission are more heavily-loaded than the wheels associated with the other transmission.
1. An all-wheel drive power equipment unit comprising:
a housing comprising front wheels and rear wheels, wherein a front transmission is adapted to selectively provide driving power to the front wheels, and a rear transmission is adapted to selectively provide driving power to the rear wheels;
a variable speed input device;
a first connection element operatively connected to the rear transmission, the first connection element adapted to selectively actuate the rear transmission from a neutral state to an engaged state in response to manipulation of the speed input device;
a second connection element connected to the front transmission, the second connection element adapted to selectively actuate the front transmission from a neutral state to an engaged state in response to the manipulation of the speed input device;
a mechanical load balancer comprising:
an input connected to the variable speed input device;
a first output connected to the first connection element; and
a second output connected to the second connection element, wherein the load balancer is adapted to distribute a force applied at the input equally between the first output and the second output; and
a resistance element associated with the front transmission, the resistance element defining a second force resisting actuation of the front transmission, wherein the second force is greater than a first force resisting actuation of the rear transmission.
2. The power equipment unit of claim 1 , wherein the first and second connection elements each comprise a cable.
3. The power equipment unit of claim 1 , wherein each of the front and rear transmissions are selectively actuated by rocking between a neutral position corresponding to the neutral state, and an engaged position corresponding to the engaged state.
4. The power equipment unit of claim 3 , wherein the resistance element comprises a spring attached between the front transmission and the housing, the spring adapted to bias the front transmission to the neutral position.
5. The power equipment unit of claim 1 , wherein the input of the load balancer comprises a pivot adapted to attach to the speed input device with an axial force member.
6. The power equipment unit of claim 1 , wherein the first output and the second output are spaced-apart equidistantly from the input.
7. The power equipment unit of claim 1 , wherein the front and rear transmissions each comprise a sheave coupled, via an endless belt, to an output shaft of an engine attached to the housing of the power equipment unit.
8. An all-wheel drive walk-behind lawn mower, the mower comprising:
a deck comprising front wheels and rear wheels;
a front transmission adapted to selectively provide driving power to the front wheels, the front transmission adapted to rock between a neutral position and an engaged position;
a rear transmission adapted to selectively provide driving power to the rear wheels, the rear transmission adapted to rock between a neutral position and an engaged position;
a variable speed input device;
a first connection element connected to the rear transmission, the first connection element adapted to selectively rock the rear transmission from the neutral position to the engaged position;
a second connection element connected to the front transmission, the second connection element adapted to selectively rock the front transmission from the neutral position to the engaged position;
a mechanical load balancer comprising:
an input connected to the variable speed input device;
a first output connected to the first connection element; and
a second output connected to the second connection element, wherein the load balancer is adapted to distribute a force applied at the input equally between the first output and the second output; and
a resistance element associated with either the rear transmission or the front transmission, the resistance element adapted to define a second force required by the associated first or second connection element to initiate rocking of the respective rear or front transmission from the neutral position, wherein the second force is greater than a first force required by the other of the first or second connection elements to initiate rocking of its respective rear or front transmission from the neutral position.
9. The mower of claim 8 , wherein the resistance element is a spring.
10. The mower of claim 8 , wherein the resistance element is an extension spring.
11. The mower of claim 8 , wherein the first and second connection elements each comprise a Bowden cable.
12. The mower of claim 8 , wherein the rear transmission is powered via a first endless drive belt, and the front transmission is powered via a second endless drive belt.
13. The mower of claim 8 , wherein the first and second outputs of the load balancer are each spaced-apart equidistantly from the input.
14. A method for controlling an all-wheel drive system for a walk-behind lawn mower, the method comprising:
displacing a speed control device, the speed control device adapted to provide an input force to an input of a load balancer;
displacing first and second connection elements attached to respective first and second outputs of the load balancer, wherein a first and second output force applied to the first and second connection elements, respectively, is equalized by the load balancer;
applying, simultaneously, the first and second output force to a rear transmission and a front transmission, respectively;
actuating the rear transmission and the front transmission from a neutral state toward an engaged state; and
providing, with a resistance element, a second force resisting initial actuation of the front transmission, wherein the second force is greater than a first force resisting initial actuation of the rear transmission.
15. The method of claim 14 , wherein actuating the rear transmission and the front transmission comprises rocking the rear and front transmissions relative to a deck of the mower.
16. An all-wheel drive walk-behind lawn mower comprising:
a housing comprising front wheels and rear wheels, wherein a front transmission is adapted to selectively drive the front wheels, and a rear transmission is adapted to selectively drive the rear wheels, wherein the rear wheels bear more weight than the front wheels;
a variable speed input device;
a first cable operatively connected to the rear transmission, the first cable adapted to selectively actuate the rear transmission from a neutral state to an engaged state in response to manipulation of the speed input device;
a second cable connected to the front transmission, the second cable adapted to selectively actuate the front transmission from a neutral state to an engaged state in response to the manipulation of the speed input device;
a mechanical load balancer comprising:
an input connected to the variable speed input device;
a first output connected to the first cable; and
a second output connected to the second cable, wherein the load balancer is adapted to distribute a force applied at the input equally between the first output and the second output; and
a resistance element associated with the front transmission, the resistance element providing a second force resisting actuation of the front transmission, wherein the second force is greater than a first force resisting actuation of the rear transmission,
wherein the second force provided by the resistance element causes the front wheels and the rear wheels to begin driving at or near the same time when the mower is operating upon a horizontal turf surface.
17. The mower of claim 16 , wherein the resistance element comprises a spring connected between the front transmission and the housing.