US3922853A

US3922853A - Speed control device

Info

Publication number: US3922853A
Application number: US479181A
Authority: US
Inventors: Hans Kalb
Original assignee: AEG Kanis Turbinenfabrik GmbH
Current assignee: Alstom Power Turbinen GmbH
Priority date: 1973-06-15
Filing date: 1974-06-13
Publication date: 1975-12-02
Anticipated expiration: 1992-12-02
Also published as: JPS5076601A; DE2331282A1; JPS5838805B2; GB1463716A; DE2331282B2; DE2331282C3

Abstract

A speed control device working with hydraulic fluid makes use of a displacement type pump. The pressure head delivered by the pump is used directly as control pressure actuating a servo-motor. The pressure head is dependent upon the pump speed which, in turn, is a function of the speed to be controlled. The regulating range of the pressure head of the pump is increased by a differential pressure controller, making use of a nozzle member, cooperating with a diaphragm and a throttle plate.

Description

United States Patent Kalb 1 Dec. 2, 1975 [54] SPEED CONTROL DEVICE 2.111.964 3/1938 Crane 60/468 2.456.431 12/1948 Price 60/329 [75] Kalb Nuremberg Germany 3.392.633 7/1968 Kokuly 60/468 X [73] Assignee: AEG-Kanis Turbinenfabrik GmbH,

Numberg Germany Primary E.\'aminer-Edgar W. Geoghegain [22] Filed: June 13, 1974 [211 Appl. No.: 479,181 [57] ABSTRACT [30] Foreign Application Priority Data A skpeed corfitroidelvice workting with hyqdgnulic fluid ma '65 use 0 a isp acement ype pump. e pressure June 1973 Gummy 2331282 head delivered by the pump is used directly as control pressure actuating a servo-motor. The pressure head is 60/325 i g ighg dependent upon the pump speed which. in turn, is a Fie'ld 459 468 function of the speed to be controlled. The regulating range of the pressure head of the pump is increased by a differential pressure controller, making use of a noz- References Cited zle member, cooperating with a diaphragm and a throttle late. UNITED STATES PATENTS p 2.005 731 6/1935 Ernst ct a]. 60/329 6 Claims, 4 Drawing Figures SPEED CONTROL DEVICE BACKGROUND OF THE INVENTION The invention relates to a speed control device working with hydraulic fluid and comprising a displacement type pump which serves as signal transmitter of the device. It has been attempted to make use of such a dis placement type pump for speed control devices. Difficulties have been encountered however, because the pressure head of such a pump increases only slightly when the rate of output flow of the pump increases in a linear proportion according to the speed.

Therefore, the pressure head of the pump is ineffective for a use to act directly upon a final control element in order to control a mass flow of an engine. In addition, the volumetric slip of a displacement type pump and alterations in the viscosity of a pressure oil may distort the control signal.

SUMMARY OF THE INVENTION It is an object of the invention to provide a speed control system making use of a displacement type pump.

It is another object of the invention to improve the sensitivity of response of the pressure controller of such a control system.

It is a further object of the invention to increase the working capacity of the servo-motor by increasing the output pressure range of the pressure controller.

Finally, it is an object of the invention to provide an integrated control system which is integrated together with the servomotor into one housing.

The foregoing objects are achieved in accordance with the present invention by providing a speed control device working with hydraulic fluid and including a displacement type pump and comprising an adjustable orifice which is the inlet of a valve chamber that communicates by that orifice with the high pressure side of the pump. The control device comprises further a differential pressure controller comprising a valve forming a first outlet of the valve chamber. The valve comprises a nozzle member and a throttle plate carried by a diaphragm and cooperates with the mouth of the nozzle member which opens into the valve chamber. Further the diaphragm is charged from within the valve chamber by a spring force, which is directed against the throttle plate. The diaphragm and the throttle plate forms one wall of the valve chamber and separates it from a second chamber. This second chamber communicates on the one hand with the high pressure side of the pump by a viscosity dependent throttle and on the other hand with the main outlet of the valve chamber by an adjustable throttling device. The control pressure to actuate the piston of a servo-motor is delivered by the main outlet of the valve chamber.

By using a differential pressure controller provided with a diaphragm the sensitivity of response of the pressure controller is very high.

The main advantage achieved by the invention is that no pump of the precision type is required although the exactness of speed control achieved is excellent, whereas the influence of alterations in the viscosity of the hydraulic fluid used is very weak. This is so because the viscosity alterations are compensated for by the viscosity dependent throttle and the adjustable throttle following each other. The intermediate pressure be- 2 tween them actuates the diaphragm and its throttle plate from the other side of the nozzle member.

In a preferred embodiment of the invention the speed -control device and the servo-motor are integrated in one and the same housing so that the effectiveness of the servo-motor is improved, because the control pressure can directly actuate the piston of the servo-motor.

In this embodiment preferably a negative feedback is achieved when the spring, charging the ball of the second valve, is supported by the piston of the servomotor.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram of the control device according to the invention.

FIG. 2 shows the curves of different pressures of the hydraulic fluid in the control device.

FIG. 3 is a longitudinal sectional view of the control ler and servo-motor housing.

FIG. 4 is a sectional view of an example of an adjustable orifice used in the arrangement according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Turning now to the figures, the invention will be explained in detail.

In FIG. 1 the circuit diagram shows the control device including the displacement type pump 50, the differential pressure controller D, a negative feedback valve RV, the servo-motor SV and a relief pressure and safety valve UV.

The main duct 101 leading to the servo-motor charging it with the control pressure p receives pressure oil from the

ducts

103, 105 and 106. An adjustable orifice 19 is installed in the duct 106 for setting the rated value of speed, while a throttle 22 and an adjustable throttle 20 are installed in the duct 105. The duct 104 leads from the relief pressure valve UV to the outlet and return duct 102.

The pressure in the main duct 101 is specified as p,, the discharge pressure of the pump 50 as p, and the pressure in the return duct 102 as p,,. The pressure oil reservoir 108 is indicated by a dash-dot line.

The pressures indicated as p, and p are intermediate pressures, their significance will follow from the description of FIG. 3.

The speed X of the machine to be controlled may be adjusted by a conventional valve (not shown) controlling, for example, the main power duct for fuel in the case of an internal-combustion machine or turbine, or the main steam supply of a steam turbine. The adjusting of the valve is effected by the stem rod 41 of the piston 2 belonging to the servo-motor SV (see FIGS. 1 and 3).

The movements of the piston 2 depend in a proportional relation on the deviations of the speed of the machine to be controlled, since the displacement type pump is coupled to a rotating member of the machine as will be explained now turning to FIG. 3. FIG. 3 shows the pressure control device and the servo-motor integrated in one housing. The servo-motor comprises a piston 2, biased by a spring 4, and a piston rod 41. The latter can be coupled e.g. with a stem of a valve which governs the flow of elastic fluid of a turbine, and it may be likewise coupled with a valve device adjusting the fuel flow of an internal-combustion machine or a gas turbine. The hydraulic fluid arrives from the high pressure side of the displacement type pump 50, which 3 may be a gear pump, e.g. of the-straight spur or the helical type, to the inlet of a valve chamber 17. The inlet is formed by an adjustable orifice 19 which serves as'the setpoint adjuster for the desired speed of the engine to be controlled.

Furthermore the pressure in the valve chamber 17 depends on the pressure p, in a second chamber separated from the valve chamber 17 by a diaphragm l2 and a throttling plate 14, carried by the diaphragm.

The hydraulic fluid arrives in the second chamber 10 through a throttle 22, which is formed by a narrow channel or bore of a certain length so that its throttling effect depends on the viscosity of the hydraulic fluid, since as it is well known, the pressure loss depends on the Reynolds number. In this manner the influence of the viscosity is compensated for.

The throttling plate 14 is further biased by a spring 18. It follows from the above that the fluid flow escaping from the valve chamber 17 through the mouth 16 and the bore 13 of the nozzle member decreases by the same ratio as the pressure p, in the second chamber 10 increases. In this manner there is provided a constant difference between the pressure p, in the second chamber 10 and the pressure p, in the valve chamber 17. Consequently there is effected a nearly constant fluid flow through orifice 19. Because the delivery of the pump is, by this means, restricted to be nearly constant too, the pressure head of the pump 50 increases at the same ratio as its shaft revolutions increase with the rotating engine member with which the pump 50 is coupled. The control pressure p which passes from the main outlet 40 of the valve chamber 17 through a channel 31 to the piston chamber 25 where it actuates the piston 2, is increased accordingly.

The movement of the piston 2 may then be transmitted to a further regulating device, e.g. a final control valve as described above.

With decreasing speed the effect is contrary. For regulating the proportional band of the control device, a second throttle is provided which is adjustable. There is additionally generated a negative feedback by the spring 8 which is supported by the piston 2 and transmits spring forces to the valve ball 6 which are proportional to the movements of the piston 2.

Accordingly there is, in the bore 13 of the nozzle member 15 a pressure is generated which, acting on the throttle plate, causes a certain quantity of hydraulic fluid to escape from the valve chamber 17 through the bore 13, to an extent proportional to the magnitude of the pressure in the bore 13.

This quantity of fluid flows off through the outlet 27. A safety valve, formed by a ball 29 biased by a spring 30 opens a passageway to the outlet 27, whereby the pump 50 is protected against overload.

Turning now to FIG. 2 it will be explained now how the volumetric slip of the displacement type pump 50 is compensated for. This compensation is effected by the differential pressure controller which generates a pressure p so that the course of the curve p, is steeper than that of the curve p,, the pressure head of the pump 50. As a result, there is obtained a differential pressure p p, which diminishes from Ap to Ap proportional to increasing speed, i.e. revolutions of the pump, and ac- 4 cordingly, proportional to increasing movement Y of the final control element.

Accordingly there is a diminished flow of hydraulic fluid through orifice 19 at the same rate as the slip of the pump 50 increases; in this way the slip is compensated for.

The adjustable orifice 19 shown in detail in FIG. 4 consists of a threaded screw having an incision 61 at its hollow tip 62 which extends into a bore 60. The flow through the bore depends on the position of the incision 61 relative to the bore which can be adjusted by the knurl 65. A ring-seal 63 is provided between two shoulders of the screw.

It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations and it is intended to cover in the appended claims all such modifications which fall within the scope of the invention.

I claim:

1. A speed control device working with hydraulic fluid and including a displacement type pump, comprising an adjustable orifice being the inlet of a valve chamber that communicates through said orifice with the high pressure side of said pump, and a differential pressure controller including a valve forming a first outlet of said valve chamber, said valve including a nozzle member and a throttle plate carried by a diaphragm and cooperating with the mouth of said nozzle member opening into said valve chamber, the said diaphragm being charged from within the valve chamber by a spring force, the said diaphragm and throttle plate being one wall of said valve chamber separating it from an additional chamber, the additional chamber communicating with the high pressure side of said displacement type pump and with a second, main outlet of said valve chamber through a throttling device, the said main outlet of said valve chamber delivering the control pressure actuating a piston of a servo-motor.

2. Speed control device according to claim 1, wherein said additional chamber communicates with the high pressure side of said displacement type pump through a viscosity dependent throttling device.

3. Speed control device according to claim 1, wherein said nozzle has a nozzle bore, the outlet of which opposite the nozzle mouth is governed by a second valve.

4. Speed control device according to claim 3, wherein said second valve is a ball biased by a spring.

5. Speed control device according to claim 4, wherein said control device and said servo-motor are arranged in one housing, said servo-motor including a piston and a piston rod movable in a piston chamber of said housing, a first part of said piston chamber being the pressure side where the control pressure is actuating the piston, a second part of said piston chamber situated on the other side of said piston being provided with an outlet for the flow-off of pressure oil, the said nozzle bore communicating with said second part of said piston chamber through said second valve, said spring biasing the valve ball being supported by said piston.

6. Speed control device according to claim 5,.

wherein said piston is biased by a second spring pro-

Claims

1. A speed control device working with hydraulic fluid and including a displacement type pump, comprising an adjustable orifice being the inlet of a valve chamber that communicates through said orifice with the hIgh pressure side of said pump, and a differential pressure controller including a valve forming a first outlet of said valve chamber, said valve including a nozzle member and a throttle plate carried by a diaphragm and cooperating with the mouth of said nozzle member opening into said valve chamber, the said diaphragm being charged from within the valve chamber by a spring force, the said diaphragm and throttle plate being one wall of said valve chamber separating it from an additional chamber, the additional chamber communicating with the high pressure side of said displacement type pump and with a second, main outlet of said valve chamber through a throttling device, the said main outlet of said valve chamber delivering the control pressure actuating a piston of a servomotor.

2. Speed control device according to claim 1, wherein said additional chamber communicates with the high pressure side of said displacement type pump through a viscosity - dependent throttling device.

6. Speed control device according to claim 5, wherein said piston is biased by a second spring provided in said second part of said piston chamber.