192 clutches and power-stop control – Vortex-flow drive and clutch – With brake
Patent
1985-11-22
1988-08-02
Bonck, Rodney H.
192 clutches and power-stop control
Vortex-flow drive and clutch
With brake
192 0076, 192103F, 303 95, F16D 2514, G05D 1362
Patent
active
047609028
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to friction clutches of the type, hereinafter referred to as being of the type specified, in which the clutch has an input portion which receives a driving input and an output portion for connection with a component to be driven by the clutch, the clutch being engaged by fluid pressure supplied from a pressure source via a solenoid-operated valve.
Clutches of the type specified are frequently used, for example, in tractor power take-off (PTO) drive lines to connect and disconnect a power take-off (PTO) shaft from the engine.
Problems arise with such clutches when used in a PTO drive line since if the clutch is engaged too quickly high shock loading can occur which will damage the drive line or any implement connected thereto and if the clutch is too slowly engaged excessive slippage will occur which can damage the clutch due to excessive heat build-up.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide an improved tractor power take-off drive line including a friction clutch of the type specified in which the above clutch engagement problems are at least mitigated.
Thus according to the present invention there is provided a tractor power take-off drive line including a friction clutch having an input portion which is driven from an engine and an output portion which drives a power take-off output shaft, fluid pressure operated clutch engaging means, a solenoid-operated valve for supplying pressurised fluid to the engaging means, and a system for controlling the engagement of the clutch, said system comprising a pulse width modulation function for providing a series of electrical pulses to the solenoid of the valve in successive predetermined time intervals during engagement of the clutch, each pulse having an "on" period during which the valve connects the engaging means to a source of pressurised fluid and an "off" period during which the valve connects the engaging means to a dump line, sensing means to provide signals indicative of the input and output speeds of the clutch, and processing means for establishing for successive time intervals the ratio between the input and output speeds of the clutch and the change in this ratio by comparison with said ratio for a previous time interval, said processing means comparing said change in input to output speed ratio with a target change in said ratio set by the system for the respective time interval to produce an error signal, and using said error signal to set the ratio of the "on" and "off" periods of the pulse width modulation function for the next successive time interval, said processing means also using the value of the input to output speed ratio to determine the target change in said input to output speed ratio for the next successive time interval so as to adjust the clutch engagement pressure to tend to reduce said error signal to zero.
Preferably during engagement of the clutch the processing means also compares the input speed of the clutch for the current time interval with the initial input speed of the clutch at the commencement of engagement of the clutch, and switches control of the system to comparison with a heavy duty target change in the input to output speed ratio if the input speed for the cuttent time interval is less then the initial clutch input speed by more than a first predetermined factor.
Typically the first predetermined factor may be 12.5%.
Preferably during engagement of the clutch the processing means also compares the input speed of the clutch for the current time interval with the initial input speed at the commencement of the engagement of the clutch, and initiates disengagement of the clutch if the input speed for the current time interval is less than the initial clutch input speed by more than a second larger predetermined factor (indicating a potential stall condition). Typically the second predetermined factor may be 50 percent. Alternatively the second predetermined factor can be defined in r.p.m. terms, for example, a decrease of 500 r.p.m.
Th
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Bonck Rodney H.
Lorence Richard M.
Massey-Ferguson Services N.V.
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