US2273408A

US2273408A - Speed regulating system

Info

Publication number: US2273408A
Application number: US394109A
Authority: US
Original assignee: Woodward Governor Co
Current assignee: Woodward Inc
Priority date: 1941-05-19
Filing date: 1941-05-19
Publication date: 1942-02-17
Anticipated expiration: 1959-02-17

Description

Feb. 17, 1942. E. E. woODwARD SPEED lREGULATING SYSTEM Filed May 19, 1941 merced' Feb. 17, 1942 UNITED STATES PATENT OFFICE SPEED REGULATING SYSTEM Elmer E. Woodward, deceased, late of Rockford, Ill., by Walter T. Woodward, administrator, Rockford, Ill., assignor to Woodward Governor Company, Illinois Rockford, lll., a corporation of Application May 19,1941, Serial No. 394,109

.4 claims.

This invention relates to speed regulating systems and more particularly to governors equipped with hydraulic compensating or stabilizing mechanism to prevent hunting and having means for modifying the action of the compensating mechanism to compensate for sudden load changes.

One object is to provide in a governor of the above character a novel modifying mechanism which operates more accurately than load compensation heretofore provided.

'A more detailed object is to provide a comperisation modifying mechanism wherein load changes vare detected electromagnetically and utilized through the intermediary of an hydraulic actuator deriving energy from a separate source.

A further object is to provide a load cornpensator of the above character having an hydraulic servo actuator energized by fluid pressure derived from the pump driven by the prime mover and controlled by a sensitive load detector.

Other'objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawing which is a schematic view and wiring diagram of a current generating system and governor control embodyingk the novel features of the present invention.

For purposes of illustration, the inventiony is shown in the drawing incorporated in an hydraulic governor control for regulating the speed of a water-wheel turbine 6 actuating a generator 'I which supplies electric current tola network 8 on which a load 9 is imposed. The

turbine speed is usually regulated by a penstock valve I0 operated through intermediate hydraulic.

mechanism (not shown) in response to movements of a rod II of a servo motor. The latter comprises a piston I2 mounted on the rod Il and reciprocable in a cylinder I3 and preferably urged in the speed-decreasing direction by a compression spring Id. l

As shown, the governor proper comprises a,

head I5 carrying flyballs IB and driven from the turbine prime mover 6 through a connection indicated at Il. The yballs are urged inwardly by a coiled spring I8 which may be adjusted through a screw I9 to vary the governor speed setting. The position of the ilyballs determines the axial position of a pilot piston 20 with respect to'a port 2l in a sleeve 22 which is slidable axially in a valve body 22" and has a port 23 communieating through a conduit 24 with an accumulator 25. The latter is charged with pressure fluid by a pump 26 driven from the prime mover 6 through the connection indicated at I'I.V The lower end of the valve cylinder 28 communicates with an oil sump 29 through a port 30 and a passage 3l.. Pressure uid flows to and from the -upper end of the servo cylinder I3 through a passage 32 connected to the port 2i.

by a spring 35 toward a neutral position. A

transmitting piston. 36 moves with the servo piston I2 to cause oil trapped in the lower end of the piston cylinder 3l to ow to and from the receiving cylinder 34 through a passage 38 having a leak port 39 therein adjustable by a needle All. 'Ihe valve chamber communicates with the sump 29 through a pipe 4i.

The arrangement Ithus far described is typical of the compensating type of hydraulic'governor ,controls to which the present invention is particularly applicable, `In operation, an increase in the turbine speed causesthe ilyballs to move outwardly lifting the pilot pistn 20 and permitting oil toescape to fthe sump from the servo cylinder through the ports 2i and 30 and the passages 32 and 3i. This permits the spring Il to move the speed controller II upwardly which causes closure of the valve I0 and 'a corresponding decrease in the turbine speed. vAs an incident to this movement of the servo and transmitter pistons I2 and 36, the pressure in the cylinders 3H and-3l is reduced permitting the piston 33 and the valve sleeve 22 to' rise' and follow-up the movement of the piston 20. iThus .the lport'2l is covered slightly before the normal I speed is'again attained. Thereafter, oil from the sump 4I is drawn through the valve .38,1` gradually raising the compensating pressure and permitting lowering of the .sleeve to normal position under the action of the centering spring 35.

In response to a-decrease in speed, the piston I 20 is lowered admitting high pressure iluld from the accumulator to the servo cylinder I3 so as to lower the control rod Ii against the action of the spring Il and increase the turbine speed. This results in an increase in the compensating pressure and immediate lowering of the valvev Means actuated by power derived from the prime mover l and controlled by a sensitive load detector is provided for modifying the pressure in the compensating circuit above described in a manner such as to avoid surges ot the prime mover incident to sudden load changes. This means includes a iluid illled cylinder I3 communicating through a conduit M with the cylinder $1. A piston I5 in the cylinder Il is operated in this instance by hydraulic actuator 56 energized from the prime mover driven pump 2i and controlled automatically by a load detector Il. The latter is actuated electrically herein in accordance with changes inthe load on the generating system. While the detector, when of electrical character, may comprise a torque motor or the like, a solenoid is employed' herein comprising an armature 43 urged in one direction by a spring I9 and in the other direction by a magnetic coil 50. The latter is connected to the secondary of a transformer 5I having its Primary interposed in one of. the linesleading from the generator 1 so as to be energized constantly. By adjusting a rheostat 53, the change in energization of the solenoid for a given load change may be varied as desired thereby adjusting the amount of load compensation.

The hydraulic actuator 45 comprises a diil'er ential piston 5I rigid with the piston I5 and slidable in a cylinder 55. The piston presents an upper surface 5B substantially larger in area than the under surface 51. The lower end of the cylinder 55 is supplied with iluid under constant pressure being in this instance connected through conduits 58 and 5! to the accumulator 25. The constant pressure thus acting on the area 51 continuously urges the pistons 45 and 5l upwardly.

Pressure fluid from the conduit 5! is permitted to ow to the upper end oi the cylinder 55 under the control of a valve 60 comprising a plunger 6I slidable in a bore B2 in the piston l5 and a sleeve extension 63 thereof. The plunger 5I coacts with ports 64 connecting the upper end of the cylinder with the bore 62 which is connected through ports 55 with the conduit 59. A hole 61 through the pistons 45 and 5I and a lower extension El permits the escape of iiuid to a drain when the valve member is raised above the ports il.

The stem 6E of the valve member is rigid with the solenoid armature I8 so that the valve member 8| is raised and lowered as the load on the prime mover increases` and decreases. Because the iiuid pressure on the valve member 6| is balanced by the same pressure on the piston B9, it will be observed that the valve member is unrestrained and may be moved easily by the solenoid. Accordingly, the valve member is positioned rapidly and accurately in response to load changes detected by the solenoid.

Assuming the parts to be in equilibrium as shown, the load compensating control produces its anticipating corrective action in the following manner in response to a sudden increase in load. Such a change results in a correspending increase in the current energizing the solenoid coil 50 drawing the plunger u and the valve member 5I upwardly against the com pression of the spring 49. This uncovering of the ports 6I permits iluid to drain from the upper end of the cylinder. The resulting reduction in pressure permits the pistons I5 and 51 to rise under the predominant upward pressure on the piston area 51. During its upward movement, the piston 45 draws oil out of the transmitting cylinder 31, the consequent lowering of the pressure in the receiving cylinder Il per mitting the valve sleeve 22 to rise relative to the valve piston 20. Pressure iiuid thus iiows from the accumulator 25 into the power cylinder I3 and the servo piston I2 moves downwardly so as to start increasing the speed setting of the prime mover controller before the ilyballs have detected a drop in speed. This action tends to minimize the speed change resulting from a load change.

The reverse action occurs upon a sudden decrease in load which causes the pull of the solenoid 50 to he decreased and the valve member 6l to be lowered thereby admitting pressure fluid from the supply 'line 59 to the upper end oi the cylinder 55. As a result of the increased pres sure above the piston 54, the piston I5 is moved downwardly thus forcing oil into the compensating system and lowering the piston 33 so as to permit the passage of oil from the power cylinder I3 to the sump. The spring I4 then moves the control rod Il in the spaced decreasing direction in anticipation of the speed change that would normally result from the load'reduction.

It will be observed that the load compensator produces the same action of the governor pilot valve as the iiyballs would produce in the absence of the load detector. This action occurs in advance of the time that the ilyball action would otherwise occur and therefore is of anticipatory character so as to compensate for the inherent lag in the response of the governor and reduce surges of the prime mover that normally take place under sudden load changes. The load compensator in effect supplements the regular governor control which operates in the normal way to correct for gradual speed changes. Owing to the leakage through the valve 39 following the pressure changes instituted by the electric load change detector, .the action of the latter is of temporary character and does not produce a permanent shift in the control point oi the governor.

The claimed invention is:

1. The combination with a prime mover of a governor operable in unison with and controlling the speed of said prime mover, an hydraulic system associated with said governor to produce a compensating action in response to speed adjustments, two axially alined cylinders of different diameters, a hollow piston slidable in the smaller cylinder and having a iiange slidable in the larger cylinder, means connecting said smaller cylinder with said hydraulic system, a tubular extension projecting from the flanged end of said piston and providing a valve chlamber communicating with the remote end of the larger cylinder, means applying a substantially constant iiuid pressure to the other end of the larger cylinder, a tubular extension projecting from the smaller end of said piston and providing a drain outlet, a valve member reciprocable in said iirst extension and regulating the ilow of pressure Huid therefrom into said larger cylinder, and means operable automatically to vary the position of said valve member in accordance with load changes on said prime'mover.

2. The combination with a prime mover of a governor operable in unison with and controlling the speed of said prime mover, an hydraulic system associated with said governor to produce a compensating action in response to speed adjustments, two cylinders of diiferent diameters disposed end to end, connected pistons slidable in said cylinders and having a passage extending through the two cylinders and providing -a valve chamber communicating with the outer end of the larger cylinder and a drain outlet at the other end, means connecting the smaller cylinder to said hydraulic system, means applying a substantially constant fluid pressure to the inner end of the larger cylinder, a valve member in said chamber regulating the flow of pressure fluid therefrom into said larger cylinder, and means operable automatically to vary the position of said valve member in'accordance with load changes on said prime mover.

3. The combination with a prime mover of an hydraulic governor operablein unison with said prime mover and having a speed responsive valve and a servo motor controlled by said valve and modulating the speed of said prime mover, hydraulically connected transmitting and receiving cylinders having a leak valve outlet, pistons in said cylinders respectively connected to said `Administrator of counteracting hydraulic pressure to the other side of said third piston, and means automatically responsive to changes in the load on said prime mover for variably controlling the magnitude of said last mentioned pressure.

4. The combination with a prime mover of an hydraulic governor operable in unison with said prime mover and having a speed responsive valve and a servo motor controlled by said valve and modulating the speed of said prime mover, hydraulically connected transmitting and receiving cylinders having a leak valve outlet, pistons in said cylinders respectively connected to said servo motor and said valve so as to impart a compensating adjustment to the valve as an incident to speed adjustment of said prime mover, a third cylinder communicating at one end with said first mentioned cylinders and having a piston therein, a fluid pump adapted to deliver a counteracting hydraulic pressure to the other side of said third piston, valve means variably controlling the magnitude of said counteracting pressure, and means automatically responsive to changes in the load on said prime mover for variably positioning said valve means.

WALTER T. WOODWARD. the Estate of Elmer E. Woodward, Deceased.