US3083697A - Engine governors - Google Patents

Description

April 2, 1963 A. G. WALFORD ENGINE GOVERNORS Filed Nov. 7, 1958 I n u enlo r 1425mm? fame )Zyzmw A ltorneys 3383,59? ENGINE GQVEE Q @123 Alexander G. Walford, Colchester, England, assignor to Darcy, l arman Sr flompzmy Limited, olchesten England Nov. 7, -953, Ser. No. 772,571 Qlaims priority, application Great Britain Nov. 12, 1957 This invention relates to engine governors designed to control the speed of an engine under varying conditions of load and in particular to a centrifugal fiyweight governor of the servo-operated type utilizing fluid-pressure feedback on to the main pilot valve sleeve or, preferably, on to the main pilot valve itself.

According to the invention, means is provided for varying the steady state feedback pressure to vary the equilibrium speed of the governor so as to obtain any desired value of permanent speed droop (i.e. a predetermined speed variation in proportion to applied load). Means is also provided for adjusting the governor to give isochronous running when desired.

An embodiment of the invention will now be described with reference to the accompanying drawing. In this embodiment, the feedback is on to the main pilot valve.

The basic governor comprises two units. These may be mounted together or separately with pipe connections (shown dotted). The two units are (a) the speed sensing and oil supply unit on the left, and (b) the power unit on the right.

Unit (a) is the larger of the two units and is mounted vertically. It contains the fiyweights 4, spring drive as sembly 3, pilot valve 9, oil pump 11, hydraulic accumulator 16 loaded by springs 17, speed setting mechanism 1 and 2 and the oil storage reservoir.

The fulcrum bearings 7 of the conventional flyweights 4- are of the needle roller type to minimize friction. The fiyweight force is transmitted to the speeder spring 3 by an angular contact ball race and spring carrier 5. The pilot valve 9 moves inside a sleeve 1% which rotates with respect to it to minimize friction. The oil pump 11 is of the gear type and is driven together with the governor from a drive shaft 13 by a set of change-speed gears 12 for speed adjustment. The drive shaft 13 runs in bearings 14 and is provided with an oil seal 15. All the Working parts are immersed in oil except the fiyweight system and spring drive.

The speed sensing and oil supply unit also comprises a feedback receiver having a fioating spring-loaded pisto 18 in a cylinder, the force from spring 2% being transmitted through a point contact strut 19 so that lateral forces are minimized.

Unit (1)) comprises the power piston 22, feedback transmitter elements and integral action control valve 40.

The power piston 22 which operates the mechanism for taking the necessary corrective action is of the differential area type, thus eliminating a return spring within the governor. (A return spring to perform the required duty at the pressures involved would be of excessively large proportions.) The difierential areas of the piston are so arranged that the return force is 75% of the force to increase fuel. This allows a return spring giving a force equivalent to 25 of the governor force to be fitted on the external linkage acting in the direction to reduce fuel in order to eliminate backlash.

The basic droop piston 39 and the spring guide 26 of the permanent droop control valve 29, which is of the spring-loaded ball-type, are mechanically connected to the power piston 22. by an adjustable linkage 59, allowing the amounts of basic and permanent droop to be varied to suit requirements. The piston 39 is operated niteti rates atone from a lever 44- connected to the piston rod passing through a bushing 38.

The fulcrum 4-1 of the lever 25 connected to the permanent droop control valve can be moved bodily to vary the amount of movement given to the control valve by a given movement of the power piston. In one position of the fulcrumin line with the central axis of the valve 29 and its spring 27this movement is reduced to zero. This is for isochronous operation as will appear later.

The means for moving the fulcrum 41 include an adjusting screw 31 rotatable by a knob 36. Similar means is provided for adjusting the fulcrum 3d of lever 44. This means comprises a fulcrum bracket 33 which can be moved relative to a slide 32 by rotating an adjusting screw 47 by means of a knob 37. A friction adjustment is provided in the form of a nut 35.

A load sensing unit (not shown) may be added to the governor at 42 to decrease the frequency variations on an alternator set. A solenoid, energized from a wattmeter circuit in the alternator output, controls the movement of a pilot valve which in turn controls a piston in the feedback circuit. Displacement of this piston created by a change in alternator load in turn causes a movement of the power piston, varying the engine power output to suit the power required. This action will precede a speed variation and will greatly reduce temporary variations of frequency during load changes.

As applied to this embodiment the operation of the load sensing unit is as follows.

The input to the solenoid corresponds to the load on the prime-mover, thus deflecting the solenoid core and pilot valve controlled thereby against a spring. This admits oil to the space above the piston of the load sensing unit (or drains it) depending upon the variation of load. The displacement of this piston causes a corresponding movement of the sleeve of the speed sensing unit and movement of the power piston. The movement of the power piston causes a corresponding movement of the basic droop piston, until the displacement of this piston cancels out the movement of the load sensing unit piston, restoring the sleeve to its original position and causing movement to cease. In practice, due to the time delays in the system, exact follow up of the power piston to load change does not occur and a small variation of speed takes place. The speed sensing system corrects this in the normal way.

It is to be understood that the load sensing unit need not be electrically operated nor indeed is its presence in any way essential to the working of the invention.

The operation of this embodiment will now be de scribed under various working conditions.

Increase of Load (lsochronous Setting) An increase in load causes the speed of the prime mover to drop. The fiywe-ights 4 move inwards because the force exerted by the speeder spring 3 overcomes the force exerted by the flyweights. This causes the pilot valve 9 to move downwards resulting in a flow of high pressure oil past the control land of the pilot valve and through connection 43 to the underside of the power piston 22 causing it to move upwards and increase the fuel supply to the prime mover by rotating the control shaft 21. Cont-r01 shaft 21 which rotates with lever 23 connected to piston 22 may be operatively connected for example by linkage 51 to a suitable throttle valve assembly 52 disposed in a fuel conduit 53 for supplying more fuel to the prime mover. This upward movement of the power piston causes a downward movement of the basic droop piston 39 via the links 24-, the control lever 23, and the adjustable feed back lever 44. The levers 25 and 44 although shown separately have their left hand ends on the same axis so that they move in synchronism. The

downward movement of the basic droop piston 39 causes a flow of oil from the space below the piston to the feedback circuit. This oil is .forced into the feedback receiver via connetion .45 and causes the piston 18 therein to rise, compressing its spring 20. The increase of force exerted by this spring causes the pressure under the feedback piston and in thefeedback circuit to rise. Asa result, the pressureentering through conduit 54 into the space under the main pilot valve 9 rise-s causing an upward force on-thepilot valve, acting in the same direction as the flywheel force. 'This increase in force tends to cause the pilot valve to rise and shut off the flow of the control oil to the power piston 22. The rise in pressure created in the feedback circuit'by upward power piston movement exerts a force on the pilotvalve equivalent to a certain increase in speed, hence, before further power piston movement takes place, the speed must drop until equilibrium exists between the force exerted by thechange in feedback pressure and the force reduction caused by the reduced rotational speed of the flyweights. Thus, if the feedback did not leak, a force would be exerted on the pilot valve system dependent upon the power piston position and the ratio of the adjustable feedback lever 44. Inpractice, leakage does exist, and in time, the feed back pressure would fall to atmospheric unless oil were supplied to the system to make up leakage. In this system, the leakage is made up through the permanent droop control valve restriction 28 which is in the axial passage through the valve sleeve 30. When the governor is set isochronously the pressure setting of this valve 29 remains'constant irrespective of power piston position. This valve is connected .to the feedback system via the integral adjust-mentrestriction 40 which allows oil to flow from or to the feedback system at a predetermined rate, depending upon the pressure variation across this restriction. When an increase of load occurs-the pressure in the feedback system will rise due to the displacement of the feedback system oil by the basic droop piston into the feedback receiver. A pressure diiference, will then exist across the restriction and flow will take place from the feedback system, through the pressure control valve 29 to drain via connection 46. As this flow occurs, the feedback receiver piston 18 will drop, the pressure decreasing proportionately until the pressure in the feedback system is equal to the set pressure of the pressure control valve, and flow across the integral restrictor 40 ceases. In practice, the setting of the restrictor is adjusted to give optimum rate of return to a steady state, dependent upon the characteristics of the prime mover. When the pressures have equalised, the forces acting on the pilot valve 9 will return to their original values and the equilibrium speed of the governor will return to its original value. 7

"Increase of Load (With Permanent Droop) When the governor is :set to give permanent droop, power piston movement causes a proportional movement of the permanent droop valve spring 27 altering the pressure setting of the permanent droop valve 29. When an increase of load occurs, the power piston 22 moves upwards, the compression of spring 27 is increased and the pressure output of the valve 29 increases; thus the pressure in the-feedback circuit-will attain an increased steady'state value. This increases the force acting on the pilot valve 9 causing the equilibrium speed to decrease. The amount of spaced variation with change inload is varied by adjustment of the fulcrum 41 of the permanent droop control lever'25, which, in turn, varies the relationship between power piston movement and the pres'sur'echange of the permanent droop control valve 29.

Decrease of Load Decrease of load causes the prime mover speed to rise. The flyweights 4 then move outwards releasing the control oil under the power piston. The high pressure oil on the upper surface of the piston (supplied through connection 48) pushes it downwards to decrease the fuel input to the prime mover; the downward movement is transmitted to the basic droop piston 39 causing the feedback pressure to drop, which in turn tends to cause the pilot valve to close the oil port. If operating with a permanent droop the pressure setting of the permanent droop valve will decrease, resulting in a drop in feedback system pressure and an increase in the equilibrium speed of the governor.

Shut Down This is effected by draining the control oil by means of a solenoid-controlled valve (not shown). The valve used is of the pilot-operated type eliminating the need for a large solenoid.

When the solenoid is de-energized to shut down the engine the oil in the space above this valve is allowed to escape. The spring force under the valve pushes the valve upwards, cutting off the oil supply from the main control ports to the underside of the power piston and draining the oil under the power piston. The high pressure oil on the upper surface of the power piston pushes it downwards, cutting the energy supply to the prime mover. When the solenoid is energized the oil in the space above the valve is trapped and oil coming through the restriction will push the valve downward, opening the passage between the control port and the power piston and so allowing the governor to operate in the normal manner.

It is to be noted that in addition to operating isochroriously and with a positive droop, i.e. speed falling as load increases, the power unit can be adjusted to give operation with a negative droop, i.e. speed rising as load increases. The term droop should therefore be taken in its broadest sense to cover both modes of operation.

The governor according to the invention has the following principal advantages.

(1) The permanent droop control obtained by varying the steady state pressure in the feedback system eliminates the need for linkage between the power piston and the main pilot valve, simplfying the construction of I the governor.

(2) The use of the system allows,the power piston to be remote from the flyweight speed sensing mechanism and pilot valve.

(3) The use of the feedback system operating at above atmospheric pressure allows large transient feedback pressures to be used, so that large forces are exerted on the pilot valve. This in turn allows large flyweight forces to be used (obtained by running the flyweights at high speed) and requires stifi speeder springs giving the flyweights a high natural frequency and good response characteristics.

(4) The use of a feedback system operating at above atmospheric pressure eliminates troubles caused by aeration of the fluid in the feedback circuit (as would occur in systems where the feedback pressure became subatmospheric).

I claim:

1. Apparatus for controlling the speed of an engine in response to changes in load on the engine comprising a governor responsive to engine speed, means for varying the engine speed, means includ n a fluid pressure motor operably connected to said engine speed varying means sure and having a pressure equalizing restricted connection to said control fluid pressure means.

2. Apparatus for controlling the speed of an engine in response to changes in load on the engine comprising a governor responsive to engine speed, means for varying the engine speed comprising a fluid pressure responsive motor, means operated by the governor in response to a change in engine speed in one direction for applying a control fluid pressure to said motor for actuating said engine speed varying means to change the engine speed in the other direction, feedback means actuated by said governor operated means for opposing action of said governor operated means for attaining a desired variable engine speed condition, said feedback means comprising a system wherein said control fluid pressure is varied by action of said governor operated means, and means for varying the action of said feedback means comprising a restricted pressure equalizing connection for gradually restoring the fluid pressure in said feedback means to equalization with said control fluid pressure. p

3. Apparatus for controlling the speed of an engine in response to load changes on the engine comprising a governor responsive to engine speed changes, means for controlling the engine fuel supply, a power piston operably connected to said fuel control means, a source of control fluid pressure connected by conduit means to said power piston, a movable pilot valve in said conduit means operably connected to said governor so that a change in engine speed acts through the governor to apply said control fluid pressure to the power piston to cause actuation of said fuel control means to effect a change in engine speed opposing that which acted through the governor, feedback means between the power piston and pilot valve comprising a fluid pressure transmitting system containing a droop piston, means providing a pressure equalizing connection between said conduit means and said'system for restoring the fluid pressure in said system to equal said control fluid pressure; and linkage interconnecting the power and droop pistons so that actuation of said droop piston by the power piston changes the fluid pressure in said system applied to move said pilot valve, said means providing the pressure equalizing connection and comprising a passage having a restriction to control the pressure equalization time and a permanent droop valve which is operably connected to said linkage and, opening in response to a transient pressure rise in said system, controls the pressure in said system.

4. Apparatus for controlling the speed of an engine in response to load changes on the engine comprising a governor responsive to engine speed changes, means for controlling the engine fuel supply, a power piston operably connected to said fuel control means, a source of control fluid pressure connected by conduit means to said power piston, a movable pilot valve in said conduit means operably connected to said governor so that a change in engine speed acts through the governor to apply said control fluid pressure to the power piston to cause actua tion of said fuel control means to effect a change in engine speed opposing that which acted through the governor, feedback means between the power piston and pilot valve comprising a fluid pressure transmitting system containing a droop piston, means providing a pressure equalizing connection between said conduit means and said system for restoring the fluid pressure in said system to equal said control fluid pressure; and linkage interconnecting the power and droop pistons so that actuation of said droop piston by the power piston changes the fluid pressure in said system applied to move said pilot valve, and means for adjusting the connection between said linkage and said permanent droop valve, said means providing the pressure equalizing connection and comprising a passage having a restriction to control the pressure equalization and a permanent droop valve which is operably connected to said linkage and, opening in response to a transient pressure rise in said system, controls the pressure in the said system.

References Cited in the file of this patent UNITED STATES PATENTS 2,364,115 Whitehead Dec. 5, 1944 2,623,504 Rodeck et al Dec. 30, 1952 2,734,490 Moulton Feb. 14, 1956 2,756,725 Parker July 31, 1956 2,762,384 Rosenberger Sept. 11, 1956 2,769,431 Massey Nov. 6, 1956 2,769,432 Massey NOV. 6, 1956

Claims (1)

1. APPARATUS FOR CONTROLLING THE SPEED OF AN ENGINE IN RESPONSE TO CHANGES IN LOAD ON THE ENGINE COMPRISING A GOVERNOR RESPONSIVE TO ENGINE SPEED, MEANS FOR VARYING THE ENGINE SPEED, MEANS INCLUDING A FLUID PRESSURE MOTOR OPERABLY CONNECTED TO SAID ENGINE SPEED VARYING MEANS AND A SOURCE OF CONTROL FLUID PRESSURE OPERATED BY THE GOVERNOR IN RESPONSE TO A CHANGE IN ENGINE SPEED IN ONE DIRECTION FOR ACTUATING SAID ENGINE SPEED VARYING MEANS TO CHANGE THE ENGINE SPEED IN THE OTHER DIRECTION, FEEDBACK MEANS ACTUATED BY SAID GOVERNOR OPERATED MEANS FOR OPPOSING ACTION OF SAID GOVERNOR OPERATED MEANS FOR ATTAINING A DESIRED VARIABLE ENGINE SPEED CONDITION, AND TIME DELAY MEANS OPERABLE AFTER ACTUATION OF SAID FEEDBACK MEANS FOR VARYING THE ACTION OF SAID FEEDBACK MEANS, SAID FEEDBACK MEANS COMPRISING A CONDUIT SYSTEM CONTAINING FLUID PRESSURE AT LEAST ABOVE ATMOSPHERIC PRESSURE AND HAVING A PRESSURE EQUALIZING RESTRICTED CONNECTION TO SAID CONTROL FLUID PRESSURE MEANS.

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