US 4,158,290 AGranted

Electro-hydraulic controller

AssigneeEaton Corporation

InventorCharles R. Cornell

Life of this patent

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Abstract

An electro-hydraulic control for a hydrostatic transmission including a variable displacement hydraulic pump, a fixed displacement hydraulic motor, and fluid operable strokers to vary the displacement of the pump. The electro-hydraulic control is in series between the charge pump and the standard manual controller and determines the pressure of the charge fluid ported to the standard controller. The electro-hydraulic control includes a spool biased toward a first position to port fluid from the charge pump to the standard controller, and biased toward a second position to relieve to tank the pressure of fluid ported to the manual controller. The biasing toward the second direction is accomplished, in part, by pressure in a fluid chamber exerting a biasing force on the spool, the fluid chamber being in communication with drain through a variable orifice which is variable in response to a pressure command signal. This signal is generated by control logic including a horsepower command signal generator which is variable to correspond to a maximum desired input horsepower, and circuitry providing a horsepower approximation signal representing the product of motor output speed and the instantaneous pressure command signal. The circuitry compares the horsepower command and horsepower approximation signals and generates a new pressure command signal tending to minimize the difference between the horsepower command and approximation signals. As a result, the commanded maximum system pressure varies, such that the product of maximum system pressure and motor output speed (proportional to pump flow) is constant, for a given input horsepower setting.

Claims14

Dependent claims

A control system for a hydrostatic transmission including a fluid pump and a fluid motor, said fluid pump having fluid operable means for varying the displacement thereof, and a source of pressurized fluid for operating the fluid operable means, said control system comprising:

(a) a housing defining a valve bore, an inlet fluid port adapted for series fluid communication with the source of pressurized fluid, a control fluid port adapted for series fluid communication with the fluid operable means, and a drain fluid port adapted for communication with a fluid drian, said ports being in fluid communication with said valve bore;
(b) valve means disposed in said valve bore and movable between a first position permitting fluid communication between said inlet fluid port and said control fluid port and a second position;
(c) first means for biasing said valve means toward said first position;
(d) second means for biasing said valve means toward said second position;
(e) one of said first and second biasing means including:
(1) means for generating a variable electrical command signal P;
and
(2) means responsive to said variable electrical command signal P to provide a variable biasing force, biasing said valve means toward said respective position, said variable biasing force being related to said variable electrical command signal P in a known manner;
(f) said means for generating said command signal P including:
(1) input command signal generator means which is variable to correspond to a maximum desired input to the transmission;
(2) means providing an electrical signal N.sub.m representative of the output speed of the fluid motor, said maximum desired input being proportional to the product of P and N.sub.m ;
(3) means providing an electrical input approximation signal representative of the product of the speed N.sub.m of the fluid motor and the instantaneous command signal P;
and
(4) means for comparing said input command signal and said input approximation signal and generating a new command signal P tending to minimize the difference between said input command signal and said input approximation signal.

11 more elements

(a) a fluid housing defining a valve bore, an inlet fluid port adapted for series fluid communication with the source of pressurized fluid, a control fluid port adapted for series fluid communication with the fluid operable means, and a drain fluid port adapted for communication with a fluid drain, said ports being in fluid communication with said valve bore;
(b) valve means disposed in said valve bore and movable between a first position permitting fluid communication between said inlet fluid port and said control fluid port, and a second position restricting fluid communication between said control fluid port and said inlet fluid port;
(c) first means for biasing said valve means toward said first position;
(d) second means for biasing said valve means toward said second position;
(e) one of said first and second biasing means including:
(1) means for generating a variable electrical pressure command signal P;
and
(2) means responsive to said variable electrical pressure command signal P to provide a variable biasing force, biasing said valve means toward said respective position, said variable force being related to said variable electrical pressure command signal P in a known manner;
(f) said means for generating said pressure command signal P including:
(1) horsepower command signal generator means which is variable to correspond to a maximum desired input horsepower to the transmission;
(2) means providing an electrical signal N.sub.m representative of the ouput speed of the fluid motor;
(3) means providing an electrical horsepower approximation signal representative of the product of the speed N.sub.m of the fluid motor and the instantaneous pressure command signal P;
and
(4) means for comparing said horsepower command signal and said horsepower approximation signal and generating a new pressure command signal P tending to minimize the difference between said horsepower command signal and said horsepower approximation signal.

11 more elements

Dependencies are inferred from the claim text.

Facts

Application: 05/909,138Filed 24 May 1978 · continuation in part
Priority: 11 May 1977
Granted: 19 Jun 1979
Term ends: Not estimatedThe source records don’t support an estimate.

Classification10 codes

F16H 61/475
Automatic regulation in accordance with output requirements: for achieving a target power, e.g. input power or output power
F04B 49/06
Control , e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided…:…
F16H 61/46
Hydrostatic: automatic regulation in accordance with output requirements
F04B 2201/1204
Parameters of driving or driven means: position of a rotating inclined plate