GB2562497A

GB2562497A - Fluid pump

Info

Publication number: GB2562497A
Application number: GB1707842.9A
Authority: GB
Inventors: Andrew Martin Jamie
Original assignee: Perkins Engines Co Ltd
Current assignee: Perkins Engines Co Ltd
Priority date: 2017-05-16
Filing date: 2017-05-16
Publication date: 2018-11-21
Also published as: GB201707842D0

Abstract

A fluid pump 202 for pumping a fluid in an engine 102 includes a pumping chamber 204 and inlet 206 and outlet 208 conduits in fluid communication with the pumping chamber. The fluid pump also includes a plunger 210 disposed within the pumping chamber driven by a crankshaft 212 to undergo reciprocating motion in the pumping chamber. The fluid pump further includes a metering valve 220 disposed in the inlet conduit to control a flow of the fluid entering the pumping chamber. The pump may comprise a pilot line 226 to communicate pressure from the outlet conduit to control opening and / or closing of the metering valve, which preferably has a damping orifice disposed within. The metering valve may be spring loaded. The pump preferably comprises a roller to couple the plunger to the crankshaft which may be operably coupled to a cam of the camshaft. First and second strokes of the plunger may respectively suck fluid into and out of the pumping chamber. Check valves may be disposed within the inlet and outlet conduits. A method of operation is also claimed.

Description

(54) Title of the Invention: Fluid pump

Abstract Title: Fluid pump with a metering valve (57) A fluid pump 202 for pumping a fluid in an engine 102 includes a pumping chamber 204 and inlet 206 and outlet 208 conduits in fluid communication with the pumping chamber. The fluid pump also includes a plunger 210 disposed within the pumping chamber driven by a crankshaft 212 to undergo reciprocating motion in the pumping chamber. The fluid pump further includes a metering valve 220 disposed in the inlet conduit to control a flow of the fluid entering the pumping chamber. The pump may comprise a pilot line 226 to communicate pressure from the outlet conduit to control opening and I or closing of the metering valve, which preferably has a damping orifice disposed within. The metering valve may be spring loaded. The pump preferably comprises a roller to couple the plunger to the crankshaft which may be operably coupled to a cam of the camshaft. First and second strokes of the plunger may respectively suck fluid into and out of the pumping chamber. Check valves may be disposed within the inlet and outlet conduits. A method of operation is also claimed.

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-1FLUID PUMP

Technical Field [0001] The present disclosure relates to a fluid pump. More particularly, the present disclosure relates to the fluid pump for pumping a fluid in an engine.

Background [0002] Generally, an internal combustion engine employs a pump for feeding a fluid, such as an oil, a coolant, and so on, into the engine. The pump may be of a fixed displacement type powered by the engine itself. Such a fixed displacement pump causes a flow rate of the fluid to vary based on an engine speed. As such, the flow rate may be lower during a low engine speed and may be higher during a high engine speed. However, in some situations, the engine may require relatively higher flow rate of the fluid even at the low engine speed. In order to cater to such situations, an oversized pump may be employed.

[0003] The oversized pump may deliver the required flow rate of the fluid even at the low engine speed. However, in situations when the required flow rate of the fluid may be low and the delivered flow rate of the fluid by the oversized pump may be high, excessive fluid may be bled off back to a sump in order to limit over pressurization in the system using a suitable bleeding strategy, such as a relief valve and an associated circuit. The bleeding off strategy may result in wastage of pumping effort, reduced performance, reduced fuel efficiency, increased emission, reduced life of the fluid, and so on. Hence, there is a need for an improved fluid pump for the engine.

[0004] German (DE) Patent Number 4,029,428 describes an engine having a crankshaft with webs from which a pump supplying lubricating and/or cooling oil is driven. The pump is housed within an axial length of the engine. One crank web includes a cam profile by which the pump is driven. The pump is a plunger type pump and may be driven by the web via intermediate components. The pump may form part of a crankshaft main bearing. The pump provides to reduce an overall length of the engine especially for a transversely mounted automotive engine installation.

-2Summary of the Disclosure [0005] In an aspect of the present disclosure, a fluid pump for pumping a fluid in an engine is provided. The fluid pump includes a pumping chamber. The fluid pump includes an inlet conduit in fluid communication with the pumping chamber. The fluid pump includes an outlet conduit in fluid communication with the pumping chamber. The fluid pump also includes a plunger disposed within the pumping chamber and configured to be driven by a crankshaft to undergo reciprocating motion in the pumping chamber. The fluid pump further includes a metering valve disposed in the inlet conduit and configured to control a flow of the fluid entering the pumping chamber.

[0006] In another aspect of the present disclosure, a method of operating a fluid pump for pumping a fluid in an engine is provided. The fluid pump includes a plunger disposed within a pumping chamber. The method includes receiving, during a first stroke of the plunger, an inflow of the fluid into the pumping chamber from an inlet conduit. The fluid flows into the pumping chamber through a metering valve disposed in the inlet conduit. The method also includes pumping, during a second stroke of the plunger, an outflow of the fluid from the pumping chamber into an outlet conduit. The method further includes using a pressure of the fluid in the outlet conduit to control the metering valve by changing a position of the metering valve based, at least in part, on the pressure of the fluid in the outlet conduit.

[0007] Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings.

Brief Description of the Drawings [0008] FIG. 1 is a perspective view of an exemplary engine, according to an embodiment of the present disclosure;

[0009] FIG. 2 is a schematic representation of a fluid pump associated with the engine, according to an embodiment of the present disclosure;

[0010] FIG. 3 is another schematic representation of the fluid pump of FIG. 2, according to an embodiment of the present disclosure;

-3[0011] FIG. 4 is another schematic representation of the fluid pump of FIG. 2, according to an embodiment of the present disclosure;

[0012] FIG. 5 is yet another schematic representation of the fluid pump of FIG. 2, according to an embodiment of the present disclosure; and [0013] FIG. 6 is a flowchart illustrating a method of working of the fluid pump of FIG. 2, according to an embodiment of the present disclosure.

Detailed Description [0014] Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or the like parts. Referring to FIG. 1, an exemplary engine 102 is illustrated. The engine 102 is an internal combustion engine powered by any fuel known in the art, such as natural gas, diesel, gasoline, and/or a combination thereof. In some embodiments, the engine 102 may be associated with a machine (not shown), such as a locomotive, a marine vessel, a land vehicle, and so on. The engine 102 and/or the machine may be employed in any industry including, but not limited to, construction, agriculture, forestry, mining, transportation, waste management, aviation, marine, material handling, and power generation.

[0015] The engine 102 includes an engine block 104. The engine block 104 includes one or more cylinders (not shown) provided therein. The cylinders may be arranged in any configuration, such as inline, radial, “V”, and so on. The engine 102 also includes a cylinder head 106 mounted on the engine block 104. The cylinder head 106 houses one or more components and/or systems (not shown) of the engine 102, such as a valve train, an intake manifold, an exhaust manifold, sensors, and so on. Additionally, the engine 102 may include various other components and/or systems (not shown), such as a crankcase, a fuel system, an air system, a cooling system, a lubrication system, a turbocharger, an exhaust gas recirculation system, an exhaust aftertreatment system, other peripheries, and so on.

[0016] Referring to FIG. 2, a schematic representation of a fluid pump 202 associated with the engine f02 is illustrated. The fluid pump 202 will be hereinafter interchangeable referred to as the “pump 202”. In the illustrated

-4embodiment, the pump 202 is an oil pump adapted to pump oil in the engine 102. In other embodiments, the pump 202 may be any pump known in the art associated with the engine 102 adapted to pump a fluid therethrough including, but not limited to, a coolant and water, based on application requirements. Also, the pump 202 may be any plunger type pump known in the art. The pump 202 may be located external or internal with respect to the engine 102 based on application requirements.

[0017] The pump 202 includes a pumping chamber 204. The pump 202 includes an inlet conduit 206 provided in fluid communication with the pumping chamber 204. The inlet conduit 206 may be further provided in fluid communication with a fluid sump (not shown), such as an oil sump of the engine 102. Accordingly, the inlet conduit 206 is adapted to provide an inflow “Fl” of the fluid from the fluid sump into the pumping chamber 204. The pump 202 also includes an outlet conduit 208 provided in fluid communication with the pumping chamber 204. The outlet conduit 208 may be further provided in fluid communication with any other portion (not shown) of the engine 102, such as an oil gallery of the engine 102. Accordingly, the outlet conduit 208 is adapted to provide an outflow “F2” of the fluid from the pumping chamber 204.

[0018] The pump 202 includes a plunger 210 disposed within the pumping chamber 204. The plunger 210 is driven by a rotating shaft 212 to undergo reciprocating motion within the pumping chamber 204. More specifically, the plunger 210 is operably coupled to an eccentric lobe or a cam 214 associated with the rotating shaft 212 through a roller 216. Accordingly, a rotation of the rotating shaft 212 and the cam 214 translates the plunger 210 within the pumping chamber 204, thus, providing the reciprocating motion to the plunger 210 within the pumping chamber 204.

[0019] In the illustrated embodiment, the rotating shaft 212 is a crankshaft of the engine 102. In other embodiments, the rotating shaft 212 may be any other shaft of the engine 102, such as a camshaft, any other power take off, and so on. Also, in the illustrated embodiment, the plunger 210 is a spring loaded piston. Accordingly, the pump 202 includes a spring 218 disposed within the pumping chamber 204 and operably coupled to the plunger 210. In other embodiments,

-5the plunger 210 may be any other plunger known in the art, such as a solenoid operated plunger, a pilot operated plunger, and so on.

[0020] As the plunger 210 translates in a first direction “DI” during a first stroke of the pump 202 based on the rotation of the rotating shaft 212 and the cam 214, the spring 218 extends within the pumping chamber 204. Also, as the plunger 210 translates in a second direction “D2” during a second stroke of the pump 202 based on the rotation of the rotating shaft 212 and the cam 214, the spring 218 compresses within the pumping chamber 204 (shown in FIG. 3). In the illustrated embodiment, the first stroke is a suction stroke of the pump 202 sucking the fluid into the pumping chamber 204 through the inlet conduit 206. Also, the second stroke is a pumping stroke of the pump 202 pumping the fluid out of the pumping chamber 204 through the outlet conduit 208. It should be noted that the first stroke and the second stroke of the pump 202 described herein is merely exemplary and may interchange or vary based on configuration of the pump 202 and/or application requirements.

[0021] The pump 202 includes a metering valve 220 disposed in the inlet conduit 206. More specifically, the metering valve 220 is provided downstream of the fluid sump and upstream of the pumping chamber 204. In the illustrated embodiment, the metering valve 220 is a pilot controlled, spring loaded valve. Accordingly, the metering valve 220 includes a metering element 222 and a valve spring 224 disposed therein. Based on a pilot pressure “PL” acting on the metering valve 220, a position of the metering element 222 and the valve spring 224 changes within the metering valve 220, in turn, providing a change in restriction within the inlet conduit 206. As such, the metering valve 220 controls the inflow “Fl” of the fluid entering the pumping chamber 204 and will be explained in more detail later.

[0022] The pump 202 includes a pilot line 226 in fluid communication with the outlet conduit 208 and the metering valve 220. More specifically, the pilot line 226 is coupled to the outlet conduit 208 downstream of the pumping chamber 204. As such, a pressure “P” of the fluid in the outlet conduit 208 or the pilot pressure “PL” is communicated through the pilot line 226 to the metering valve

-6220. Accordingly, the pilot pressure “PL” controls an opening position “OP” and/or a closing position “CP” (shown in FIG. 3) of the metering valve 220.

[0023] More specifically, as the pressure “P” of the fluid within the outlet conduit 208 may increase, the pilot pressure “PL” may act on the metering valve 220 displacing the metering element 222 towards the valve spring 224 by compressing the valve spring 224. Accordingly, the metering element 222 may increase the restriction within the inlet conduit 206, in turn, reducing the inflow “Fl” of the fluid from the inlet conduit 206 into the pumping chamber 204.

[0024] Alternatively, as the pressure “P” of the fluid within the outlet conduit 208 may decrease, the valve spring 224 may extend displacing the metering element 222 away from the valve spring 224 against the pilot pressure “PL” acting on the metering valve 220. Accordingly, the metering element 222 may decrease the restriction within the inlet conduit 206, in turn, increasing the inflow “Fl” of the fluid from the inlet conduit 206 into the pumping chamber 204.

[0025] The pump 202 also includes a damping orifice 228 disposed within the pilot line 226. In the illustrated embodiment, the damping orifice 228 is a fixed restriction orifice. In other embodiments, the damping orifice 228 may be a variable restriction orifice based on application requirements. The damping orifice 228 reduces pressure spike within the pilot line 226 resulting from change in the pressure “P” of the fluid in the outlet conduit 208. The reduction in the pressure spike in the pilot pressure “PL” limits sudden changes in the position of the metering valve 220 and resulting pressure spike within the inlet conduit 206 and in the inflow “Fl” of the fluid into the pumping chamber 204.

[0026] Additionally, the pump 202 includes a first check valve 230 disposed in the inlet conduit 206 and in fluid communication with the pumping chamber 204 and the metering valve 220. More specifically, the first check valve 230 is provided downstream of the metering valve 220 and upstream of the pumping chamber 204. The first check valve 230 limits reverse flow of the fluid through the inlet conduit 206 from the pumping chamber 204 towards the metering valve 220. The pump 202 also includes a second check valve 232 disposed in the outlet conduit 208 and in fluid communication with the pumping chamber 204. More specifically, the second check valve 232 is provided downstream of the pumping

-Ίchamber 204 and upstream of the pilot line 226. The second check valve 232 limits reverse flow of the fluid through the outlet conduit 208 towards the pumping chamber 204.

[0027] During operation of the pump 202, as the plunger 210 reciprocates in the first direction “DI” during the first stroke based on the rotation of the cam 214, the plunger 210 draws the fluid into the pumping chamber 204 through the inlet conduit 206, the metering valve 220, and the first check valve 230. In such a situation, the second check valve 232 limits the reverse flow of the fluid from the outlet conduit 208 into the pumping chamber 204. For the purpose of explanation, the metering valve 220 is shown in the opening position “OP” providing minimum or no restriction to the inflow “Fl” of the fluid.

[0028] As the plunger 210 further reciprocates in the second direction “D2” during the second stroke based on further rotation of the cam 214, the plunger 210 pumps the fluid from the pumping chamber 204 through the outlet conduit 208 and the second check valve 232. In such a situation, the first check valve 230 limits the reverse flow of the fluid from the pumping chamber 204 into the inlet conduit 206.

[0029] During operation of the pump 202, the pressure “P” of the fluid in the outlet conduit 208 acts as the pilot pressure “PL” on the metering valve 220 through the pilot line 226 and the damping orifice 228. As shown in FIG. 3, as the pressure “P” of the fluid in the outlet conduit 208 may increase to an increased pressure “PI”, the pilot pressure “PL” may proportionally increase to an increased pilot pressure “PLI”. The increased pilot pressure “PLI” acts on the metering valve 220 displacing the metering valve 220 in the closing position “CP” and restricting the inflow “Fl” of the fluid into the pumping chamber 204 through the inlet conduit 206.

[0030] Referring to FIG. 4, as the inflow “Fl” of the fluid decreases, the travel of the plunger 210 along the first direction “DI” during the suction stroke reduces due to reduced availability of the fluid through the inlet conduit 206. As a result, a reduced volume of the fluid is drawn into the pumping chamber 204 in the closing position “CP” of the metering valve 220. Further, as shown in FIG. 5, during the pumping stroke, this reduced volume of the fluid is pumped through

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the outlet conduit 208 resulting in a reduced pressure “PR” of the fluid in the outlet conduit 208. The reduced pressure “PR” acts as a reduced pilot pressure “PLR” through the pilot line 226 on the metering valve 220. Accordingly, the valve spring 224 biases the metering valve 220 against the reduced pilot pressure “PLR” in the opening position “OP” of the metering valve 220.

[0031] As the pressure “P” of the fluid in the outlet conduit 208 may be within a threshold limit, the metering valve 220 may be held in the opening position “OP” by the pilot pressure “PL” acting thereon. As the pressure “P” of the fluid in the outlet conduit 208 may exceed the threshold limit, the increased pilot pressure “PLI” may proportionally act on the metering valve 220 in order to bias the metering valve 220 in the closing position “CP” (shown in FIGS. 3 and 4). Further, as the pressure “P” of the fluid in the outlet conduit 208 may be lower or approximately equal to the threshold limit, the reduced pilot pressure “PLR” may proportionally act on the metering valve 220 in order to bias the metering valve 220 in the opening position “OP” (shown in FIGS. 2 and 5), and the cycle continues.

[0032] It should be noted that the opening position “OP” and the closing position “CP” of the metering valve 220 described herein is merely exemplary and may vary based on application requirements. For example, based on a magnitude of the pilot pressure “PL”, the metering element 222 may be held in the opening position “OP”, or the closing position “CP”, or any other intermediate position between the opening position “OP” and the closing position “CP”. Accordingly, the metering valve 220 may proportionately control the inflow “Fl” of the fluid through the inlet conduit 206 into the pumping chamber 204 and a displacement of the plunger 210 within the pumping chamber 204 during the first stroke and/or the second stroke, in turn, controlling an output of the pump 202 through the outlet conduit 208. As such, the controlled displacement of the plunger 210 provides the constant pressure “P” of the fluid through the outlet conduit 208 during the first stroke and/or the second stroke of the pump 202.

-9Industrial Applicability [0033] The present disclosure relates to a method 600 of operating the pump 202 for pumping the fluid in the engine 102. Referring to FIG. 6, a flowchart of the method 600 is illustrated. At step 602, as shown in FIG. 2, the inflow “Fl” of the fluid is received into the pumping chamber 204 from the inlet conduit 206 during the first stroke of the plunger 210. The plunger 210 is reciprocated along the first direction “DI” within the pumping chamber 204 during the first stroke by the rotating shaft 212, the rotation of the cam 214, and the extension of the spring 218. Also, during the first stroke, the second check valve 232 limits the reverse flow of the fluid from the outlet conduit 208 into the pumping chamber 204. Accordingly, the fluid flows into the pumping chamber 204 through the metering valve 220 and the first check valve 230 disposed in the inlet conduit 206.

[0034] At step 604, the outflow “F2” of the fluid is pumped from the pumping chamber 204 into the outlet conduit 208 during the second stroke of the plunger 210. The plunger 210 is reciprocated along the second direction “D2” within the pumping chamber 204 during the second stroke by the rotating shaft 212, the rotation of the cam 214, and the compression of the spring 218. Also, during the second stroke, the first check valve 230 limits the reverse flow of the fluid from the pumping chamber 204 into the inlet conduit 206. Accordingly, the fluid flows into the outlet conduit 208 from the pumping chamber 204 through the second check valve 232 disposed in the outlet conduit 208.

[0035] At step 606, the metering valve 220 is controlled by the pressure “P” of the fluid in the outlet conduit 208. The pressure “P” of the fluid in the outlet conduit 208 is communicated as the pilot pressure “PL” to the metering valve 220 via the pilot line 226. The metering valve 220 is controlled by changing the position of the metering element 222 based, at least in part, on the pressure “P” of the fluid in the outlet conduit 208.

[0036] For example, as shown in FIG. 3, during operation of the pump 202 as the pilot pressure “PL” increases, the increased pilot pressure “PLI” acts on the metering valve 220 through the pilot line 226. Accordingly, the metering element 222 is biased towards the closing position “CP” of the metering valve

-10220 by compressing the valve spring 224. As shown in FIG. 4, this increases the restriction within the inlet conduit 206, in turn, reducing the volume of the fluid drawn into the pumping chamber 204 during the first/suction stroke.

[0037] Further, as shown in FIG. 5, during the second/pumping stroke, as the pump 202 now pumps the reduced volume of the fluid into the outlet conduit 208, the reduced pressure “PR” of the fluid and the reduced pilot pressure “PLR” acts on the metering valve 220 through the pilot line 226. Accordingly, the metering element 222 is biased towards the opening position “OP” of the metering valve 220 by extension of the valve spring 224. This reduces the restriction within the outlet conduit 208, in turn, increasing the volume of the fluid drawn into the pumping chamber 204 during the first/suction stroke.

[0038] Also, the damping orifice 228 provided in the pilot line 226 provides to reduce pressure spike acting on the metering valve 220. This controls a pulsation of the metering valve 220, a sudden variation in the volume of the fluid entering the pumping chamber 204, and, thus, a sudden pulsation in the pressure “P” of the fluid in the outlet conduit 208. Accordingly, the metering valve 220 controls the inflow “Fl” of the fluid entering the pumping chamber 204 and the displacement of the plunger 210 within the pumping chamber 204 during the first/suction stroke of the pump 202 based on the pressure “P” of the fluid in the outlet conduit 208.

[0039] The pump 202 provides a simple, efficient, and cost effective variable displacement plunger type pump without complex geometries and complex electronic circuitry. The pump 202 provides a simple alternative to a conventional variable displacement rotary vane pump. The displacement of the plunger 210 of the pump 202 is hydraulically controlled by means of throttling/metering, thus, limiting full extension of the plunger 210 in situations of increased fluid delivery.

[0040] The pump 202 provides to reduce parasitic load on the engine 102 by pumping a required volume of the oil at constant pressure at all times. As such, wastage of pumping energy is limited by eliminating discharge of excess oil via means of an additional pressure relief valve strategy. The reduced parasitic load may, in turn, result in improved performance, improved fuel efficiency, reduced emissions, and so on.

[0041] Further, a relatively smaller size of the pump 202 may be employed in comparison to a size of the conventional variable displacement rotary vane pump for a similar application, thus, reducing component cost and component footprint within the engine 102. The smaller size of the pump 202 may provide increased priming rates, reduced pumping effort, reduced wear and tear, improved engine/component/oil life, reduced maintenance cost, and so on. The pump 202 may be retrofitted in any engine with minor or no modification to the existing system as the pump 202 may be operated by any rotating shaft having an eccentrically shaped component to drive the plunger 210.

[0042] While aspects of the present disclosure have been particularly shown and described with reference to the embodiments above, it will be understood by those skilled in the art that various additional embodiments may be contemplated by the modification of the disclosed machines, systems and methods without departing from the spirit and scope of the disclosure. Such embodiments should be understood to fall within the scope of the present disclosure as determined based upon the claims and any equivalents thereof.

-12Global Claims

Claims

What is claimed is:

1. A fluid pump (202) for pumping a fluid in an engine (102), the fluid pump (202) comprising:

a pumping chamber (204);

an inlet conduit (206) in fluid communication with the pumping chamber (204);

an outlet conduit (208) in fluid communication with the pumping chamber (204);

a plunger (210) disposed within the pumping chamber (204) and configured to be driven by a crankshaft (212) to undergo reciprocating motion in the pumping chamber (204); and a metering valve (220) disposed in the inlet conduit (206) and configured to control a flow of the fluid entering the pumping chamber (204).

2. The fluid pump (202) of claim 1 further comprising a pilot line (226) in fluid communication with the outlet conduit (208) and the metering valve (220), wherein a pressure (P) of the fluid in the outlet conduit (208) is communicated through the pilot line (226) and controls an opening position (OP) and/or a closing position (CP) of the metering valve (220).

3. The fluid pump (202) of claim 2 further comprising a damping orifice (228) disposed within the pilot line (226).

4. The fluid pump (202) of claim 1, wherein the metering valve (220) is a pilot controlled, spring loaded, metering valve (220).

5. The fluid pump (202) of claim 1 further comprising a roller (216) adapted to operably couple the plunger (210) to the crankshaft (212).

6. The fluid pump (202) of claim 5, wherein the roller (216) is operably coupled to a cam (214) associated with the crankshaft (212).

7. The fluid pump (202) of claim 1, wherein a first stroke of the plunger (210) comprises a suction stroke of the fluid pump (202) sucking fluid into the pumping chamber (204).

8. The fluid pump (202) of claim 1, wherein a second stroke of the plunger (210) comprises a pumping stroke of the fluid pump (202) pumping fluid out of the pumping chamber (204) and out through the outlet conduit (208).

9. The fluid pump (202) of claim 1, wherein the plunger (210) is a spring loaded piston.

10. The fluid pump (202) of claim 1 further comprising a first check valve (230) disposed in the inlet conduit (206) and in fluid communication with the pumping chamber (204) and the metering valve (220).

11. The fluid pump (202) of claim 1 further comprising a second check valve (232) disposed in the outlet conduit (208) and in fluid communication with the pumping chamber (204).

12. The fluid pump (202) of claim 1, wherein the fluid pump (202) is at least one of an oil pump, a coolant pump, and a water pump associated with the engine (102).

13. A method (600) of operating a fluid pump (202) for pumping a fluid in an engine (102), the fluid pump (202) comprising a plunger (210) disposed within a pumping chamber (204), the method (600) comprising:

receiving, during a first stroke of the plunger (210), an inflow (Fl) of the fluid into the pumping chamber (204) from an inlet conduit (206),

-14wherein the fluid flows into the pumping chamber (204) through a metering valve (220) disposed in the inlet conduit (206);

pumping, during a second stroke of the plunger (210), an inflow (F2) of the fluid from the pumping chamber (204) into an outlet conduit (208); and using a pressure (P) of the fluid in the outlet conduit (208) to control the metering valve (220), wherein controlling the metering valve (220) comprises changing a position of the metering valve (220) based, at least in part, on the pressure (P) of the fluid in the outlet conduit (208).

14. The method (600) of claim 15 further comprising using the metering valve (220) to control, during the first stroke, the inflow (Fl) of the fluid entering the pumping chamber (204) and a displacement of the plunger (210).

15. The method (600) of claim 15 further comprising controlling a flow of the fluid from the pumping chamber (204) towards the metering valve (220) using a first check valve (230).

16. The method (600) of claim 15 further comprising controlling a flow of the fluid from the outlet conduit (208) towards the pumping chamber (204) using a second check valve (232).

17. The method (600) of claim 15 further comprising controlling pulsation in the pressure (P) of the fluid in the outlet conduit (208) using a damping orifice (228).

18. The method (600) of claim 15 further comprising operating the plunger (210) during at least one of the first stroke and the second stroke using at least one of a crankshaft (212) and a spring action.

19. The method (600) of claim 15 further comprising biasing the metering valve (220) against the pressure (P) of the fluid in the outlet conduit (208) using a spring action.

20. The method (600) of claim 15 wherein the pressure (P) of the fluid in the outlet conduit (208) is communicated to the metering valve (220) via a pilot line (226).

Intellectual

Property Office

Application No: GB 1707842.9