CRANKSHAFT DRIVEN VALVE ACTUATION

Abstract

A hydraulic valve actuation system (30) and a method of assembly can include a plurality of hydraulically actuatable valves (34a, 34b, 34c, 34d, 134a, 134b, 134c, 134d) operably associated with an internal combustion engine (86) having a crankshaft (50) rotatable about a longitudinal axis. The actuation system (30) can include at least one cam lobe (52) mounted on or integrally formed with the crankshaft for rotation with the crankshaft (50). At least one fluid piston pump (36, 36a, 36b) connected to the at least one cam lobe (52) for generating a reciprocating fluid flow in response to rotation of the at least one cam lobe (52). At least one hydraulically actuated valve (34a, 34b, 34c, 34d, 134a, 134b, 134c, 134d) in fluid communication with the reciprocal fluid flow generated by the at least one fluid piston pump (36, 36a, 36b) to drive the valve (34a, 34b, 34c, 34d, 134a, 134b, 134c, 134d) to be controlled toward an open position.

Description

FIELD OF THE INVENTION

The invention relates to a method and apparatus for hydraulic actuation of valves in an internal combustion engine, and more particularly, to hydraulic actuation of intake and exhaust valves of an internal combustion engine.

BACKGROUND

An internal combustion engine generates power by burning fuel in a combustion chamber. Current intake and exhaust valves can be controlled and operated by camshafts and cams located in the engine. Intake valves can be opened in order to admit fuel and air into a cylinder for combustion, while exhaust valves can be opened to allow combustion gas to escape from the cylinder. The cams can be fixed profile cams which can provide difficulty in adjusting timings or amounts of engine valve lifts needed to optimize valve opening times and lift for varying engine operations. A lost motion device can be used between a valve and the cam for transmitting varying amounts of the cam motion to the valve. Current lost motion systems use a master piston which displaces fluid from a hydraulic chamber into a hydraulic chamber of a slave piston. The slave piston can act on the engine valve for opening the valve. The hydraulic system generally includes added components such as cam sensors, oil control valves, phasers, guides, timing chains, tensioners, sprockets, bearing caps, and miscellaneous bolts and fasteners. The need for the added components in order to operate a lost motion system can increase valve train inertia, which can be problematic at high engine speeds. The added components can also increase complexity and cost such that it can be desirable to minimize the additional components. Valve actuation systems have been disclosed in U.S. Pat. No. 8,365,691; U.S. Pat. No. 6,997,148; U.S. Pat. No. 6,425,357; U.S. Pat. No. 5,645,031; U.S. Pat. No. 4,716,863; U.S. Pat. No. 2,072,437; U.S. Patent Application No. 2011/0197833; and W.O. Patent Application No. 2007/142724.

SUMMARY

It can also be desirable to eliminate the camshaft as an additional component due to the added size and weight of the camshaft to the valve train. To overcome the limitation of current technology, the disclosed hydraulic valve actuation system uses at least one cam lobe connected to a crankshaft to be driven in rotation for reciprocating a master piston for pressurizing fluid to drive reciprocal fluid flow within the hydraulic valve actuation system. The use of a cam lobe connected directly to the crankshaft can eliminate added components currently used in valve actuation systems such as the cam sensors, oil control valves, phasers, guides, timing chains, tensioners, sprockets, bearing caps, and miscellaneous bolts and fasteners. The hydraulic valve actuation system can control the opening and closing of a plurality of hydraulically actuatable valves, either intake valves or exhaust valves, or both intake and exhaust valves. The valves can be associated with a plurality of cylinders of an internal combustion engine and can have a corresponding slave piston for each valve. Each of the plurality of slave pistons can be normally biased by a spring toward a first position corresponding to the valve being in a closed valve position. The slave piston can be driven toward a second position corresponding to the valve being in an open position by fluid pressure overcoming a biasing force of the spring. The hydraulic valve actuation system can include at least one accumulator operable for reciprocally receiving and releasing fluid in a lost motion manner when valve actuation is not desired, and for maintaining fluid pressure and volume in the hydraulic valve actuation system.

A hydraulic valve actuation system can include at least one fluid pressure piston pump having at least one reciprocal master piston for movement within a housing defining at least one fluid pumping chamber. The fluid piston pump can include at least one biasing spring for biasing the corresponding reciprocal master piston toward a first position within the housing. The hydraulic valve actuation system can include a crankshaft rotatable about a longitudinal axis and having at least one cam lobe carried on the crankshaft for rotation therewith. The at least one cam lobe can be driven in rotation about the longitudinal rotational axis of the crankshaft and can be engageable with a cam follower connected to a corresponding reciprocal master piston. The cam follower can drive the at least one reciprocal master piston toward a second position into the at least one fluid pumping chamber when driven by the at least one cam lobe to pressurize the working fluid for reciprocal flow through the fluid passages of the hydraulic valve actuation system. The biasing spring can normally bias the corresponding reciprocal master piston and associated cam follower toward the first position and into continuous engagement with the at least one cam lobe of the crankshaft located outside of the pump chamber.

The at least one reciprocal master piston can be operable for pressurizing fluid located in the at least one fluid pumping chamber when driven by the at least one cam lobe mounted on the crankshaft to overcome the biasing force of the at least one biasing spring creating sufficient working fluid pressure and volume to operably actuate one or more of a plurality of valves in fluid communication with the hydraulic valve actuation system as fluid flow reciprocates within the hydraulic valve actuation system fluid passages in response to reciprocation of the master piston driven by the cam lobe mounted on and driven in rotation with the crankshaft. The pump chamber can be in fluid communication with the plurality of valves allowing pressurized fluid flow toward one or more of the plurality of valves during a driven stroke of the reciprocal master piston by the cam lobe and allowing fluid flow to be drawn back into the pump chamber from one or more of the plurality of valves during a return stroke of the reciprocal master piston driven by the biasing spring. The pump chamber can also be operable for fluid communication with the at least one accumulator for maintaining working fluid volume and pressure during the operating cycle and to make up for working fluid volume losses and pressure losses due to normal leakage during operation cycles. The working fluid, being an essentially incompressible working fluid, can allow reciprocal flowing movement of the working fluid through the hydraulic valve actuation system in response to reciprocal movement of the master piston as the master piston reciprocal movement follows the cam lobe rotation corresponding to rotation of the crankshaft. The master piston is in continuous fluid communication with the hydraulic valve actuation system fluid passages during operation of the internal combustion engine.

The hydraulic valve actuation system can further include at least one first control valve operable between a first position isolating fluid flow between the at least one accumulator and the hydraulic valve actuation system fluid passages and a second position for providing fluid communication between the hydraulic valve actuation system fluid passages and the at least one accumulator. The at least one first control valve can provide for fluid communication between the at least one fluid pressure piston pump and the at least one valve assembly.

A method of operating a normally closed valve of an internal combustion engine having a rotatable crankshaft can include driving reciprocal fluid flow within a fluid passage in response to rotation of the crankshaft of the internal combustion engine, and selectively communicating an expandable fluid chamber associated with a normally closed valve with the reciprocal fluid flow within the fluid passage for cyclically driving the normally closed valve between an open position and a closed position in response to fluid flow within the passage. The method can include rotating a cam lobe mounted on a crankshaft of an internal combustion engine, and driving at least one fluid pressure piston pump having at least one reciprocal master piston in movement within a housing defining at least one fluid pumping chamber in response to rotation of the cam lobe. The method can include biasing the corresponding reciprocal master piston toward a first position within the housing with a spring for maintaining continuous contact between a cam follower connected to the corresponding reciprocal master piston and the rotating cam lobe.

A method of assembling a hydraulic valve actuation system can include mounting a cam lobe on a crankshaft of an internal combustion engine for rotation with the crankshaft, and connecting a cam follower to at least one reciprocal master piston of at least one fluid pressure piston pump for driving reciprocal movement of the master piston in response to rotation of the cam lobe driven in rotation by the crankshaft to create a reciprocal fluid flow cycle within a closed fluid flow path, and biasing the master piston toward a first position for maintaining the cam follower in continuous contact with the cam lobe. The method can include connecting at least one valve for selectively allowing and preventing fluid communication between an expandable fluid chamber operably associated with a valve to be actuated and the closed fluid flow path carrying the reciprocal fluid flow driven by the reciprocal movement of the master piston. The method can include connecting an engine control unit for selectively controlling fluid communication with each of the expandable fluid chambers associated with a valve to be actuated to prevent and allow fluid communication during a reciprocal fluid flow cycle carried within the closed fluid flow path to open and close each valve to be actuated in a predetermined sequence according to signals received from an engine control unit. The method can include connecting at least one valve for selectively allowing and preventing fluid communication between the closed fluid flow path and at least one accumulator.

Other applications of the present invention will become apparent to those skilled in the art when the following description of the best mode contemplated for practicing the invention is read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein:

FIG. 1 is a schematic view of a crankshaft driven valve actuation system including a crankshaft, a valve assembly, either intake or exhaust, and a hydraulic valve actuation system illustrating a cam lobe mounted on a crankshaft and driven in rotation by the crankshaft of an internal combustion engine, the cam lobe for driving a master piston in reciprocal movement between first and second positions to create a reciprocal fluid flow within a closed fluid flow path, a first control valve illustrated in a first position for allowing fluid communication between the master piston chamber and the valve assembly, and at least one switching valve for selectively allowing and preventing fluid communication between an expandable fluid chamber associated with a valve to be actuated and the closed fluid flow path, wherein the at least one switching valve is in a first position to allow fluid communication between the expandable fluid chamber for actuating a first valve associated with a first cylinder of an internal combustion engine and the reciprocal fluid flow within the closed fluid flow path, while preventing fluid communication between an expandable fluid chamber for actuating a second valve associated with a fourth cylinder of the internal combustion engine and the reciprocal fluid flow within the closed fluid flow path;

FIG. 2 is a schematic view of the crankshaft driven valve actuation system of FIG. 1 illustrating the at least one switching valve in a second position for allowing fluid communication between the second valve associated with the fourth cylinder of the internal combustion engine and the reciprocal fluid flow within the closed fluid flow path, while preventing fluid communication between the first valve associated with the first cylinder of the internal combustion engine and the reciprocal fluid flow within the closed fluid flow path, where the master piston is shown driven by the cam lobe angularly positioned at a maximum distance with respect to the master piston defining a first position forcing fluid into the closed fluid flow path from the master piston chamber;

FIG. 3 is a schematic view of the crankshaft driven valve actuation system of FIG. 1 illustrating the crankshaft rotated 180° from the position shown in FIGS. 1 and 2 to angularly position the cam lobe at a minimum distance with respect to the master piston defining a second position drawing fluid from the closed fluid flow path back into the master piston chamber;

FIG. 4 is a schematic view of the crankshaft driven valve actuation system of FIG. 1 illustrating the first control valve in a second position operable for allowing fluid communication between the master piston, an accumulator, and the valve assembly;

FIG. 5 is a schematic view of the crankshaft driven valve actuation system of FIG. 1, where continuous fluid communication between the master piston chamber and the valve assembly is provided through a passage, and the first control valve is operable between a first closed position and a second open position for selectively controlling fluid communication between the master piston chamber and the accumulator;

FIG. 6 is a simplified detailed perspective view of the crankshaft illustrating at least one cam lobe connected to the crankshaft with various engine components removed for clarity;

FIG. 7A is a perspective cross sectional view of the crankshaft driven valve actuation system;

FIG. 7B is a plan view of the crankshaft illustrating crank counterweights;

FIG. 8A is a schematic view of the crankshaft driven valve actuation system for selectively controlling the opening of a single valve illustrating a first control valve operable between a first closed position and a second open position for selectively controlling fluid communication between the master piston chamber and the accumulator for lost motion fluid flow when actuation of the single valve is not desired;

FIG. 8B is a schematic view of the crankshaft driven valve actuation system for selectively controlling the opening of two valves illustrating a first normally closed engine valve, a second normally closed engine valve, and a fluid switching valve in a second position for allowing fluid communication between the first valve and reciprocal fluid flow within the closed fluid flow path, while preventing fluid communication between the second valve and reciprocal fluid flow within the closed fluid flow path, where the master piston is shown driven by the cam lobe angularly positioned at a maximum distance with respect to the master piston defining a first position forcing fluid into the closed fluid flow path from the master piston chamber; and

FIG. 9 is a schematic view of a crankshaft driven valve actuation system for selectively controlling four intake valves and four exhaust valves including a crankshaft, an internal combustion engine valve assembly, including both intake and exhaust valves, and a hydraulic valve actuation system illustrating two cam lobes located at approximately 220° with respect to one another connected to the crankshaft to be driven in rotation by the crankshaft of an internal combustion engine for driving first and second master pistons in reciprocal movement between first and second positions to create a reciprocal fluid flow within two separate closed fluid flow paths, four control valves, each control valve movable between a first position operable for allowing fluid communication between the master piston chamber and the accumulator, and at least one switching valve for selectively allowing and preventing fluid communication between an expandable fluid chamber associated with each valve to be actuated and the closed fluid flow path.

DETAILED DESCRIPTION

Referring now to FIGS. 1-9, a crankshaft driven valve actuation system 30 for controlling opening and closing of a plurality of hydraulically actuated valves 34a, 34b, either intake valves, exhaust valves, or both intake and exhaust valves, corresponding to a plurality of cylinders of an internal combustion engine 86 is illustrated. The system can include a plurality of slave pistons 44a, 44b corresponding to the plurality of valves 34a, 34b. Each of the plurality of slave pistons 44a, 44b can be normally biased by a spring toward a normally closed valve position, and can be hydraulically driven with fluid pressure sufficiently high to overcome the biasing force of the spring toward an open valve position. The hydraulic valve actuation system 30 can include at least one accumulator 46 operable for receiving and releasing fluid volume for providing a lost motion fluid flow when valve actuation is not desired, and for maintaining fluid pressure and volume in the hydraulic valve actuation system 30. By way of example and not limitation, the hydraulic valve actuation system 30 can be used in a four-stroke internal combustion engine 86 having a plurality of valves 34a, 34b, either hydraulically actuated intake valves, hydraulically actuated exhaust valves, or both hydraulically actuated intake and exhaust valves.

By way of example and not limitation, a four stroke—four cylinder cycle can refer to travel of each engine piston between an intake stroke, a compression stroke, an ignition/combustion/power stroke, and an exhaust stroke, such that the at least one cam lobe 52 can drive the master piston within the master piston chamber to force fluid into the closed fluid flow path in order to open one of the valves 34a with the at least one switching valve 70 in the position shown and the cam lobe in the 0° position as illustrated in FIG. 1. By way of example and not limitation, the valves 34a, 34b can correspond to intake valves or exhaust valves associated with a first and fourth cylinder or intake valves or exhaust valves associated with a second and third cylinder of an internal combustion engine. As illustrated in FIG. 8A, the crankshaft driven valve actuation system 30 can operate directly to open a single intake valve or a single exhaust valve. It should be recognized that a plurality of cam lobes 52 can be provided mounted on the crankshaft for driving reciprocal fluid flow through separate closed fluid flow paths for opening each intake valve and/or each exhaust valve individually. It should further be recognized that a single lobe 52 can drive one master piston pump corresponding to one closed fluid flow path, or can drive multiple master piston pumps corresponding to multiple closed fluid flow paths, if the master piston pumps are offset angularly from one another by approximately 180° for operation of the same valve type, two intake valves or two exhaust valves, or offset angularly from one another by approximately 220° for operation of different type valves, e.g. one intake and one exhaust valve. By way of example and not limitation, it should also be recognized, as illustrated in FIG. 8B, that the opening and closing of two valves 34a, 34b, either intake or exhaust valves, for different cylinders of an internal combustion engine can be actuated with a single master piston pump 38 driving reciprocal fluid flow within a single closed fluid flow path, a single control valve 56, by way of example and not limitation a control valve having an actuator such as a solenoid operated actuator, a piezoelectric operated actuator, or any other mechanically or electrically operated actuator for a control valve, selectively allowing communication with an accumulator 47 and a single switching valve 64 for selectively directing reciprocal fluid flow to one of the two valves 34a, 34b to be controlled.

It should be recognized by those skilled in the art that the single switching valve can be replaced with two separate individually actuated valves, where each valve has a closed position and an open position for selectively directing fluid flow to a corresponding valve to be controlled without departing from the disclosure of the present invention. It should be recognized by those skilled in the art that the cam lobe can be mounted directly to the crankshaft or can be formed integrally with the crankshaft, in either case, the cam lobe is rotated at crankshaft speed. It should further be recognized by those skilled in the art, that additional master fluid piston pump chambers and closed fluid flow paths can be provided similar to the disclosure above to provide hydraulic valve actuation of the exhaust valves. It should be recognized by those skilled in the art that the two cam lobes illustrated in FIG. 9 can be offset at different angular orientations with respect to one another allowing control of intake valves from one lobe and exhaust valves from another lobe, or can include master fluid piston pump chambers driven by cam followers located offset at different angular orientations with respect to one another around the first cam lobe allowing control of intake and exhaust valves for two cylinders from the first cam lobe, while the intake and exhaust valves for the two other cylinders are controlled from the second cam lobe. In other words, the cam followers for a master fluid piston pump chamber for controlling exhaust valves can be located angularly offset approximately 220° from the master fluid piston pump chambers for controlling the corresponding intake valves for the same cylinder of the internal combustion engine while being driven by the same first cam lobe. Alternatively, the cam followers for master fluid piston pump chambers for intake and exhaust valve control can be driven by separate first and second cam lobes in the same angular orientation while being located offset longitudinally from one another while the cam followers are located offset approximately 220° from one another. Alternatively, the cam followers for master fluid piston pump chambers for intake and exhaust valve control can be driven by separate first and second cam lobes offset longitudinally from one another and in different angular orientations with respect to one another allowing the cam followers and/or associated master fluid piston pump chambers to be located in any desired angular orientation with respect to one another, even side by side if desired.

Each cam lobe 52 can include a cam follower for driving a master piston pump for actuating at least one or more valves. A single cam lobe 52 can drive either two intake valves and two exhaust valves associated with a first and fourth cylinder if cam followers are located angularly offset by approximately 220° from one another, or two intake valves associated with the first and fourth cylinder and two intake valves associated with a second and third cylinder if cam followers are located angularly offset by approximately 180° from one another. In order for the single cam lobe 52 to drive two intake valves and two exhaust valves associated with the first and fourth cylinder, or second and third cylinder, shorter hydraulic channel lengths can be used and the corresponding cam followers can be located approximately 220° with respect to one another. In order for the single cam lobe 52 to drive two intake valves associated with the first and fourth cylinder and two intake valves associated with the second and third cylinder, the cam followers can be located approximately 180° with respect to one another. Finally, it should be recognized by those skilled in the art that the four stroke—four cylinder engine cycle is by way of example and not limitation, since the crankshaft driven hydraulic valve actuation system can be modified to accommodate different engine configurations, such as by way of example and not limitation, two or more cylinder engine configurations, such as three cylinder, six cylinder, eight cylinder, or more than eight cylinder engine configurations without departing from the disclosure of the present invention.

The improvement of the hydraulic valve actuation system 30 can include at least one fluid piston pump 36, a crankshaft 50, and at least one first control valve 56. The at least one fluid piston pump 36 can include at least one reciprocal master piston 38, at least one fluid pumping chamber 40, and at least one biasing spring 42. The biasing spring 42 can normally bias the master piston 38 toward a first position with respect to the pump chamber 40. The master piston 38 can be operable for reciprocally driving fluid in and out of the pump chamber 40 when driven by rotation of the crankshaft. The pump chamber 40 can be in continuous fluid communication with the plurality of valves 34a, 34b, and can selectively be placed in fluid communication for fluid flow with respect to the at least one accumulator 46. The crankshaft 50 can be rotatable about a longitudinal axis and can have at least one cam lobe 52 mounted to or integrally formed as part of the crankshaft for rotation with the crankshaft. The at least one cam lobe 52 can be driven in rotation about the longitudinal axis and can be continuously engageable with a cam follower 54. The cam follower 54 can be connected to the at least one reciprocal master piston 38 for reciprocal driven motion with respect to the at least one fluid pumping chamber 40 in response to rotation of at least one cam lobe 52. The at least one first control valve 56 can provide for fluid communication between the at least one fluid pressure piston pump 36 and the at least one accumulator 46.

Referring now to FIGS. 1-4, a hydraulic valve actuation system 30 can include a fluid piston pump 36 having a master piston 38, a pump chamber 40, and a biasing spring 42 normally biasing the master piston 38 toward a first position with respect to the pump chamber 40. The master piston 38 can reciprocally drive fluid into and out of the pump chamber 40 when driven by rotation of the cam lobe 52. The pump chamber 40 can be in continuous fluid communication with a plurality of valves 34a, 34b and can be selectively in fluid communication with an accumulator 46 through a first control valve 56, by way of example and not limitation a control valve having an actuator such as a solenoid operated actuator, a piezoelectric operated actuator, or any other mechanically or electrically operated actuator for a control valve. The crankshaft 50 can be rotatable about a longitudinal axis and can have a cam lobe 52 connected to the crankshaft 50 for rotation. The cam lobe 52 can be rotatable with the crankshaft 50 about the longitudinal axis and can continuously engage a cam follower 54. The cam follower 54 can drive the master piston 38 reciprocally with respect to the pump chamber 40 when driven in response to rotation of the cam lobe 52. The hydraulic valve actuation system 30 can include a first control valve 56 and a second control valve 64.

As illustrated in FIG. 1, the first control valve 56 can provide for continuous fluid communication between the pump chamber 40 and a valve assembly 32 in a first position 62 and a second position 60, while isolating the closed fluid flow passages from fluid communication with the accumulator when in the first position 62 and providing selective fluid communication with the accumulator 46 when in the second position 60. With the first control valve 56 is in the first or second position 62, 60 as illustrated in FIG. 1, the second control valve 64 can selectively switch fluid communication between the master piston 38 and one of a plurality of slave pistons 44a, 44b for driving the corresponding engine valve 34a, 34b from a normally closed position toward an open position. The valve assembly 32 can include a plurality of hydraulically actuated engine valves 34a, 34b. By way of example and not limitation, it is contemplated that the disclosed hydraulic valve actuation system 30 can be used in any number of cylinders, by way of example and not limitation, such as a one, two, three, four, six, or eight cylinder internal combustion engine 86.

In operation, rotation of the crankshaft 50 rotates the cam lobe 52 for driving the master piston from a first position (shown in FIG. 3) toward a second position (shown in FIG. 1) within the fluid pump 36, as the cam follower 54 continuously engages with the cam lobe 52. Reciprocation of the master piston 38 can reciprocally drive fluid out of and draw working fluid back into the pump chamber 40 for providing reciprocal fluid flow within a closed fluid flow path between the fluid pump 36 and the valve assembly 32. The fluid can leave the pump chamber 40 and flow through the first control valve 56. The first control valve 56 can include a first valve position 62, a second valve position 60, and an actuator 58, by way of example and not limitation a control valve having an actuator such as a solenoid operated actuator, a piezoelectric operated actuator, or any other mechanically or electrically operated actuator for a control valve, for changing between the first and second valve positions. As illustrated in FIGS. 1-2, the first valve position 62 can provide fluid communication between the fluid pump 36 and the valve assembly 32, while being isolated from fluid communication with the accumulator 46. As illustrated in FIG. 4, the second valve position 60 can provide fluid communication between the fluid pump 36 and the valve assembly 32, while allowing fluid communication between the accumulator 46, the fluid pump 36 and the valve assembly 32. In the first and second valve positions 60, 62, fluid flow can occur between the fluid pump 36 and the valve assembly 32, as the cam lobe 52 is driven in rotation about an axis of rotation thereby generating a reciprocal movement of the master piston within the fluid pump 36.

A fluid reservoir or sump 90 can provide fluid to a fluid pump 92 for delivery through a check valve 96a to the accumulator 46 when the first control valve 56 is in either the first position 62, or the second position 60, and can additionally supply fluid to the pump chamber 40 when the first control valve 56 is in the second position 60. The accumulator 46 can operate as a lost fluid motion reservoir when valve actuation is not desired during reciprocation of the fluid pump 36, while also acting as a pressurized fluid reservoir for holding a volume of the fluid under pressure and for maintaining the fluid pressure and volume in the hydraulic valve actuation assembly 30. In other words, the accumulator 46 can be used to modify the shape of the timing curve and allow for lost motion in the hydraulic system by reducing motion of the valve while directing fluid flow to the accumulator 46. The inclusion of the accumulator 46 in the system can allow a valve in fluid communication with the accumulator to open late, close early, open partially, or prevent opening of the valve all together. The accumulator 46 can include an accumulator spring 47 for maintaining pressure of the fluid in the absence of the pump 92 running. The accumulator 46 can provide fluid flow to the hydraulic valve actuation assembly 30 when the first control valve 56 is in the second valve position 60 to replenish any fluid losses from the closed fluid flow path, dampen pressure fluctuations, and supply supplemental fluid pressure when required for changes in valve timing operation or to assist valve operation during engine startup.

The fluid can flow between the first control valve 56 and the second control valve 64. The second control valve 64 can be a high-speed switching valve for switching or skipping fluid flow between each of the plurality of intake valves 34a, 34b. The switching or skipping function can be used to make use of the lost fluid motion that would otherwise occur when controlling a single engine valve function with the hydraulic valve actuation assembly 30. It is contemplated that more than one switching valve could be used with an internal combustion engine 86 having additional cylinders and intake/exhaust valves. By way of example and not limitation, as illustrated in FIG. 1, the second control valve 64 can be in a first valve position 68 providing for fluid flow between the fluid pump 36 and an engine valve 34a corresponding to a first cylinder. The engine valve 34a can include a slave piston 44a. The slave piston 44a can be normally biased away from the engine valve 34a by a biasing spring 48a. When the slave piston 44a is pressurized by the fluid flow, the force can overcome the spring force such that the slave piston 44a can open the engine valve 34a. Fluid can also be returned from the expandable chamber of the slave piston 44a associated with the engine valve 34a to reciprocate back to the pump chamber 40 after passing through a check valve 80b and/or by reversing fluid flow direction through the second control valve 64. As illustrated in FIG. 1, the second control valve 64 when in the first position 68 can prevent fluid flow to the engine valve 34b corresponding to a third cylinder. Fluid flowing through the first control valve 56 can flow towards the second control valve 64, while being prevented from flowing directly to engine valve 34a by check valve 80b and to the engine valve 34b by a check valve 80c.

As illustrated in FIG. 2, when the second control valve 64 is in the second valve position 70, the fluid can flow between the fluid pump 36 and the engine valve 34b. The engine valve 34b can include a slave piston 44b. The slave piston 44b can be normally biased away from the engine valve 34b by a biasing spring 48b. When the slave piston 44b is pressurized by the fluid flow, the force can overcome the spring force such that the slave piston 44b can open the engine valve 34b. Fluid can also be returned from the expandable chamber of the slave piston 44b associated with the engine valve 34b to reciprocate back to the pump chamber 40 by reverse flow through second control valve 64 when in the second position 70 and/or through check valve 80c during the return stroke of piston 38. As illustrated in FIG. 2, the second control valve 64 when in the second position 70 can prevent fluid flow to the engine valve 34a corresponding to the first cylinder. When the second control valve 64 is in the second valve position 70, fluid flowing through the first control valve 56 can flow towards the second control valve 64, while being prevented from flowing directly to the engine valve 34a by the check valve 80b and to the engine valve 34b by check valve 80c. As illustrated in FIG. 3, the crankshaft 50 can be rotatable such that the cam lobe 52 is in a position 180° from the position shown in FIG. 1 with the cam follower 54 maintained in contact with the cam lobe by force from biasing spring 42 as the master piston 38 is returned to the first position.

As illustrated in FIG. 5, the first control valve 156 can isolate the pump chamber 40 from fluid communication with the accumulator 46 when in a first position 160, while providing for fluid communication between the pump chamber 40 and the accumulator 46 when in a second position 162. In the configuration illustrated in FIG. 5, the pump chamber 40 can be in constant fluid communication with the engine valve assembly 32 while the first control valve 156 provides a selectively controlled opened/closed function with respect to the accumulator 46 through the first control valve 156. The first control valve 156 can include a first valve position 160, a second valve position 162, and an actuator 158, by way of example and not limitation a control valve having an actuator such as a solenoid operated actuator, a piezoelectric operated actuator, or any other mechanically or electrically operated actuator for a control valve. As illustrated in FIG. 5, the first valve position 160 can prevent fluid communication between the accumulator 46 and the fluid pump 36, effectively isolating the reciprocal closed fluid flow path from the accumulator 46. The second valve position 162 can provide for fluid communication between the reciprocal closed fluid flow path, the fluid pump 36, and the accumulator 46. Reciprocal fluid flow through the closed fluid flow path can constantly occur between the fluid pump 36 and the engine valve assembly 32 in response to the cam lobe 52 driving reciprocation of the piston 38 of the fluid pump 36 independent of the first control valve 156 being in either the first or second positions 160, 162.

Referring now to FIGS. 6-7B, the hydraulic valve actuation system 30 disclosed can be used in a four cylinder internal combustion engine 86. FIG. 6 shows eight control valves 70a corresponding to the four cylinders. Each cylinder can have a set of intake valves 34a, 234a and a set of exhaust valves 134a, 334a. Each of the eight control valves 70a can correspond to two intake valves 34a, 34b and two exhaust valves 134a, 134b. The disclosed hydraulic valve actuation system 30 can be used for cylinders having a four-stroke cycle, but it is contemplated that the system could be used in a two-stroke engine. It is contemplated that a plurality of engine valve assemblies 32 could be used in the internal combustion engine 86 for controlling intake and exhaust valves as illustrated in FIG. 9.

As illustrated in FIGS. 6, 7B and 8B, it is contemplated that the crankshaft 50 can include at least one crank counterweight 76. The crankshaft 50 can be driven by a plurality of pistons 94 associated with the engine 86. Rotation of the crankshaft 50 can drive rotation of the at least one cam lobe 52 mounted on or formed integrally with the crankshaft for driving reciprocal movement of at least one reciprocal master piston 38, 38a, 38b. The first reciprocal master piston 38, 38a, 38b can control actuation of two engine valves for two pistons of the four cylinders similar to that shown and described in FIGS. 1-4. A switching valve 70 can control the opening and closing of two engine valves 34a, 34b. The crank counterweight 76 can counterbalance mass added to the crankshaft 50. The at least one crank counterweight 76 can be mounted to the crankshaft 50. As illustrated in FIG. 8B, a cam follower 54 can be normally biased against the at least one cam lobe 52 by a spring and can convert the rotational movement from the crankshaft 50 into the reciprocal movement of the at least one reciprocal master piston 38. In the four cylinder combustion engine, a first cam follower 54a and a second cam follower 54b can correspond to the first and second reciprocal master piston 38a, 38b. It is also contemplated that the crankshaft 50 can have more than one cam lobe 52 connected to or integrally from on the crankshaft to be driven in rotation about the longitudinal axis of the crankshaft 50. In a four cylinder engine 86, the cam lobes 52, if separate cam lobes 52 are provided, or cam followers 54a, 54b, if a single cam lobe 52 is used, can preferably be located angularly offset by approximately 220° from each other for operation of intake or exhaust valves. In a four-stroke engine 86, two intake and two exhaust valves corresponding to two cylinders can share the at least one cam lobe 52 with cam followers 54a, 54b located approximately 220° angularly offset from one another for driving a corresponding reciprocal master piston 38a, 38b. The at least one cam lobe 52 can rotate at a crankshaft speed corresponding to the rotation of the crankshaft 50. The plurality of slave pistons 44a, 44b corresponding to the plurality of engine valves 34a, 34b can be switched on alternative revolutions of the crankshaft 50.

The hydraulic valve actuation system 30 can further include a control system, or electronic engine control unit 98, for operation. The control system can include at least one controller and sensor in electrical connection with the at least one first control valve 56 and the at least one second control valve 64. The controller can include an electronic control module having at least one microprocessor and at least one memory module. The controller can be adapted to control the actuation of the at least one first control valve 56 and the at least one second control valve 64 in response to a control program stored in memory based on signals received from one or more sensors. The sensors can detect a cam angle of the at least one cam lobe 52 with respect to the crankshaft 50. The controller can control the operation of the internal combustion engine 86, such as the operation of the sump pump 92, control valves 70, 70a, and control valves 56, 156, 64

Advantages of implementing the disclosed hydraulic actuation system 30 in an engine 86 include weight savings by eliminating additional components such as cam sensors, oil control valves, phasers, guides, timing chains, tensioners, sprockets, bearing caps, and miscellaneous bolts and fasteners. The disclosed hydraulic actuation system 30 can also reduce parasitic losses in the engine 86 resulting from the use and wear of the additional components. The package size of the engine 86 can also be reduced significantly by particularly removing camshafts. The disclosed hydraulic valve actuation system 30 can provide significant economic advantages by reducing production costs associated with the engine 86 due to removing the cost of the additional components. The use of multiple control valves and cam lobes can also provide flexibility of intake and exhaust valve motion control including control of advance and retard timing events for valves.

A method of assembling a hydraulic valve actuation system 30 for controlling the opening and closing of a plurality of hydraulically actuatable valves 34a, 34b corresponding to a plurality of cylinders of an internal combustion engine 86 having a crankshaft can include mounting a cam lobe on the crankshaft for rotation with the crankshaft, driving reciprocation of at least one fluid pressure piston pump 36 in response to rotation of the cam lobe by the crankshaft, connecting the at least one fluid pressure piston pump 36 to a closed fluid flow path for directing reciprocal fluid flow from the at least on fluid pressure piston pump 36 in fluid communication with at least one valve to be controlled, and inserting at least one control valve 56 within the reciprocal closed fluid path for selectively directing reciprocal fluid flow between at least one valve to be controlled. The method can also include positioning a cam follower 54 between the cam lobe and the fluid pressure piston pump 36. The method can include hydraulically actuating at least one engine valve 34a, 34b with at least one slave piston 44a, 44b, biasing each of the slave pistons 44a, 44b normally toward a closed valve position, selectively applying fluid pressure to selected slave pistons to drive the valve to be controlled toward the open position. The method can also include providing lost fluid motion and maintaining fluid volume and pressure in the hydraulic valve actuation system 30 with at least one accumulator 46 operable for receiving and releasing pressurized fluid into the reciprocal closed fluid flow path. The method can also include reciprocating at least one master piston 38 within at least one fluid pumping chamber 40 of at least one fluid pressure piston pump 36 for generating reciprocal fluid flow in response to rotation of the cam lobe, and biasing the at least one master piston 38 toward a first position with at least one biasing spring 42. The method can also include positioning a cam follower 54 interposed between the at least one cam lobe 52 and the at least one fluid pressure piston pump 36.

Referring now to FIG. 9, a hydraulic valve actuation system 30 can include at least one cam lobe 52a, 52b and at least one fluid piston pump 36a, 36b, 36c, 36d having a master piston 38a, 38b, 38c, 38d, a pump chamber 40a, 40b, 40c, 40d and a biasing spring 42a, 42b, 42c, 42d normally biasing the master piston 38a, 38b, 38c, 38d toward a first position with respect to the pump chamber 40a, 40b, 40c, 40d, where the master piston 38a, 38b, 38c, 38d draws fluid into an enlarged volume pump chamber 40a, 40b, 40c, 40d. By way of example and not limitation, each of the at least one cam lobe 52a, 52b can correspond to two fluid piston pumps 36a, 36b, 36c, 36d. The master piston 38a, 38b, 38c, 38d can reciprocally drive fluid into and out of the pump chamber 40a, 40b, 40c, 40d when driven by rotation of the cam lobe 52a, 52b to a second position with respect to the pump chamber 40a, 40b, 40c, 40d, where the master piston 38a, 38b, 38c, 38d expels fluid from a reduced volume pump chamber 40a, 40b, 40c, 40d. The pump chamber 40a, 40b, 40c, 40d can be in continuous reciprocal fluid communication with a plurality of valves 34a, 34b; 34c, 34d; 134a, 134b; 134c, 134d through separate closed fluid flow paths independently driven by master piston 38a, 38b, 38c, 38d, and can be selectively in fluid communication with an accumulator 46a, 46b, 46c, 46d through a first control valve 56a, 56b, 56c, 56d, by way of example and not limitation a control valve having an actuator such as a solenoid operated actuator, a piezoelectric operated actuator, or any other mechanically or electrically operated actuator for a control valve. The crankshaft 50 can be rotatable about a longitudinal axis. A first and second cam lobe 52a, 52b can be mounted on or integrally formed with the crankshaft 50 for rotation. By way of example and not limitation, the first and second cam lobe 52a, 52b can be mounted on or integrally formed with the crankshaft 50 at approximately 220° with respect to one another, such that the first cam lobe 52a can correspond to operation of intake valves 34a, 34b, 34a, 34b associated with four cylinders of the internal combustion engine, while the second cam lobe 52b can correspond to operation of the exhaust valves 134a, 134b, 134c, 134d.

In either case, the cam lobe 52a, 52b can be rotatable in response to rotation of the crankshaft 50 about the longitudinal axis and can be continuously engaged by a cam follower 54a, 54b 54c, 54d. The cam follower 54a, 54b, 54c, 54d can drive the corresponding master piston 38a, 38b, 38c, 38d reciprocally with respect to the corresponding pump chamber 40a, 40b, 40c, 40d when driven in response to rotation of the cam lobe 52a, 52b. The hydraulic valve actuation system 30 can include a first control valve 56a, 56b, 56c, 56d and second control valve 64a, 64b, 64c, 64d, by way of example and not limitation a control valve having an actuator such as a solenoid operated actuator, a piezoelectric operated actuator, or any other mechanically or electrically operated actuator for a control valve. As illustrated in FIG. 9, the first control valve 56a, 56b, 56c, 56d can provide for reciprocal continuous fluid communication between the pump chamber 40a, 40b, 40c, 40d and an accumulator 46a, 46b, 46c, 46d in second position 62a, 62b, 62c, 62d, while isolating the closed fluid flow passages from fluid communication with an accumulator 46a, 46b, 46c, 46d when in the first position 60a, 60b, 60c, 60d. With the first control valve 56a in either the first or second position 60a, 62a as illustrated in FIG. 9, the second control valve 64a can selectively switch fluid communication between the master piston 38a, 38b, 38c, 38d and one of a plurality of slave pistons 44a, 44b, 44c, 44d, 144a, 144b, 144c, 144d for driving the corresponding valve 34a, 34b, 34c, 34d, 134a, 134b, 134c, 134d from a normally closed position toward an open position. The valve assembly can include a plurality of hydraulically actuated valves 34a, 34b, 34c, 34d, 134a, 134b, 134c, 134d. By way of example and not limitation, it is contemplated that the disclosed hydraulic valve actuation system 30 can be used in an internal combustion engine having any number of cylinders, such as a two, three, four, six, or eight cylinder internal combustion engine 86. By way of example and not limitation, as illustrated in FIG. 1 and FIGS. 8A-9, the present embodiment can be used in a four cylinder internal combustion engine 86 and can include intake valves 34a, 34b, 34c, 34b and exhaust valves 134a, 134b, 134c, 134d.

Fluid can also be returned from the expandable chambers of the slave pistons 44a, 44b, 44c, 44d, 144a, 144b, 144c, 144d associated with the valve 34a, 34b, 34c, 34d, 134a, 134b, 134c, 134d to reciprocate back to the pump chamber 40a, 40b, 40c, 40d after passing through optional check valve 80b, 80c; 180b, 180c; 80d, 80e, 180d, 180e and/or by reversing fluid flow direction through the second control valve 64a, 64b, 64c, 64d. The second control valve 64a, 64b, 64c, 64d can be in the first position 68a, 68b, 68c, 68d preventing fluid flow to one of the two valves associated with the second control valve 64a, 64b, 64c, 64d.

As illustrated in FIG. 9, the engine control unit 98 can control the operation of the control valves 56a, 56b, 56c, 56d, 64a, 64b, 64c, 64d and pumps 92a, 92b, 92c, 92d by control signals generated in accordance with a control program stored in memory in response to control signals received by the engine control unit 98 from sensors (not shown).

In operation, as illustrated in FIG. 9, with the first cam lobe 52a initially shown in a 0° angular position and the second cam lobe 52b located approximately 220° with respect to the first cam lobe 52a for purposes of this description, the control valves 64a, 64b, 64c, 64d initially positioned as illustrated in positions 68a, 68b, 68c, 68d. As the cam lobes 52a, 52b rotates through to a 180° angular position from that illustrated, the control valves 64a, 64b, 64c, 64d transition into positions 68a, 68b, 70c, 70d. As the cam lobes 52a, 52b rotates through from the 180° angular orientation toward a 360° angular orientation, the control valves 64a, 64b, 64c, 64d transition into positions 70a, 70b, 70c, 70d. As the cam lobes 52a, 52b rotates through from 360° toward 540°, the control valves 64a, 64b, 64c, 64d transition into positions 70a, 70b, 68c, 68d. As the cam lobes 52a, 52b rotates through 540° toward 720° (i.e. completing a second 360° rotation), the control valves 64a, 64b, 64c, 64d transition back into initial positions 68a, 68b, 68c, 68d and the cycle repeats. It should be recognized that the software program can change the duration and degree of opening defining a valve actuation curve of each valve as desired according to the control program stored in memory for execution by the engine control unit 98.

While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiments but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.

Claims

1. In a hydraulic valve actuation system (30) for controlling opening and closing a plurality of hydraulically actuated valves (34a, 34b, 34c, 34d, 134a, 134b, 134c, 134d) associated with an internal combustion engine (86) having a crankshaft (50) rotatable about a longitudinal axis, the improvement comprising:

at least one cam lobe (52, 52a, 52b) mounted on the crankshaft (50) to be driven in rotation with the crankshaft (50);

at least one fluid piston pump (36, 36a, 36b, 36c, 36d) operably connected to the at least one cam lobe (52, 52a, 52b) for generating a reciprocating fluid flow in response to rotation of the at least one cam lobe (52, 52a, 52b); and

at least one hydraulically actuated valve (34a, 34b, 34c, 34d, 134a, 134b, 134c, 134d) in fluid communication with the reciprocating fluid flow to drive the at least one hydraulically actuated valve (34a, 34b, 34c, 34d, 134a, 134b, 134c, 134d) between a normally closed position and an open position.

2. The improvement of claim 1 further comprising:

at least one accumulator (46a, 46b, 46c, 46d) for providing lost fluid flow motion to prevent valve actuation in response to the reciprocating fluid flow; and

at least one first control valve (56, 56a, 56b, 56c, 56d) for selectively placing the reciprocating fluid flow in fluid communication with the at least one accumulator (46a, 46b, 46c, 46d).

3. The improvement of claim 1 further comprising:

the at least one hydraulically actuated valves including a first hydraulically actuated valve (34a, 34c, 134a, 134c) and a second hydraulically actuated valve (34b, 34d, 134b, 134d); and

at least one second control valve (64, 64a, 64b, 64c, 64d) for selectively controlling fluid communication between the reciprocating fluid flow and one of the first hydraulically actuated valve (34a, 34c, 134a, 134c) and the second hydraulically actuated valve (34b, 34d, 134b, 134d).

4. The improvement of claim 1 further comprising:

a slave piston (44a, 44b, 44c, 44d, 144a, 144b, 144c, 144d) connected to each of the at least one hydraulically actuated valves (34a, 34b, 34c, 34d, 134a, 134b, 134c, 134d) to be controlled, each slave piston (44a, 44b, 44c, 44d, 144a, 144b, 144c, 144d) normally biased toward a closed valve position, each slave piston (44a, 44b, 44c, 44d, 144a, 144b, 144c, 144d) driven by reciprocating fluid flow toward an open valve position.

5. The improvement of claim 1, wherein the at least one fluid piston pump (36, 36a, 36b, 36c, 36d) further comprises:

at least one reciprocal master piston (38, 38a, 38b, 38c, 38d), at least one fluid pumping chamber (40, 40a, 40b, 40c, 40d), and at least one biasing spring (42, 42a, 42b, 42c, 42d), the biasing spring (42, 42a, 42b, 42c, 42d) normally biasing the master piston (38, 38a, 38b, 38c, 38d) into engagement with the at least one cam lobe (52, 52a, 52b), the master piston (38, 38a, 38b, 38c, 38d) for reciprocally driving fluid in and out with respect to the at least one fluid pumping chamber (40, 40a, 40b, 40c, 40d).

6. The improvement of claim 1 further comprising:

a cam follower (54, 54a, 54b, 54c, 54d) located between the at least one cam lobe (52, 52a, 52b) and the at least one fluid piston pump (36, 36a, 36b, 36c, 36d), the cam follower (54, 54a, 54b, 54c, 54d) reciprocally driving the at least one fluid piston pump (36, 36a, 36b, 36c, 36d) in response to rotation of the at least one cam lobe (52a, 52b).

7. A hydraulic valve actuation system (30) for an internal combustion engine (86) having a crankshaft (50) rotatable about a longitudinal axis comprising:

a cam lobe (52, 52a, 52b) mounted on the crankshaft to be driven in rotation with the crankshaft (50);

a fluid piston pump (36, 36a, 35b, 36c, 36d) connected to the cam lobe (52, 52a, 52b) for generating a reciprocating fluid flow in response to rotation of the cam lobe (52, 52a, 52b); and

a hydraulically actuated valve (34a, 34b, 34c, 34d, 134a, 134b, 134c, 134d) in fluid communication with the reciprocating fluid flow to drive the hydraulically actuated valve (34a, 34b, 34c, 34d, 134a, 134b, 134c, 134d) between a normally closed position and an open position.

8. The hydraulic valve actuation system (30) of claim 7 further comprising:

an accumulator (46a, 46b, 46c, 46d) for providing lost fluid flow motion to prevent valve actuation in response to the reciprocating fluid flow; and

a first control valve (56, 56a, 56b, 56c, 56d) for selectively placing the reciprocating fluid flow in fluid communication with the accumulator (46a, 46b, 46c, 46d).

9. The hydraulic valve actuation system (30) of claim 7 further comprising:

the hydraulically actuated valve including a first hydraulically actuated valve (34a, 34c, 134a, 134c) and a second hydraulically actuated valve (34b, 34d, 134b, 134d); and

a second control valve (64, 64a, 64b, 64c, 64d) for selectively controlling fluid communication between the reciprocating fluid flow and one of the first hydraulically actuated valve (34a, 34c, 134a, 134c) and the second hydraulically actuated valve (34b, 34d, 134b, 134d).

10. The hydraulic valve actuation system (30) of claim 7 further comprising:

a slave piston (44a, 44b, 44c, 44d, 144a, 144b, 144c, 144d) connected to the valve (34a, 34b, 34c, 34d, 134a, 134b, 134c, 134d) to be controlled, the slave piston (44a, 44b, 44c, 44d, 144a, 144b, 144c, 144d) normally biased toward a closed valve position and driven by reciprocating fluid flow toward an open valve position.

11. The hydraulic valve actuation system (30) of claim 7, wherein the fluid piston pump (36) further comprises:

a reciprocal master piston (38), a fluid pumping chamber (40), and a biasing spring (42), the biasing spring (42) normally biasing the master piston (38) into engagement with the cam lobe (52), the master piston (38) operable for reciprocally driving fluid in and out with respect to the fluid pumping chamber (40).

12. The hydraulic valve actuation system (30) of claim 7 further comprising:

a cam follower (54) located between the cam lobe (52) and the fluid piston pump (36), the cam follower (54) reciprocally driving the at least one fluid piston pump (36) in response to rotation of the cam lobe (52).

13. A method of assembling a hydraulic valve actuation system (30) for controlling opening and closing a plurality of hydraulically actuated valves (34a, 34b, 34c, 34d, 134a, 134b, 134c, 134d) corresponding to a plurality of cylinders of an internal combustion engine (86) having a crankshaft (50) rotatable about a longitudinal axis, the method comprising:

forming a cam lobe (52, 52a, 52b) connected to the crankshaft for rotation with the crankshaft (50);

assembling a fluid pressure piston pump (36, 36a, 36b, 3) for generating a reciprocating fluid flow in response to rotation of the cam lobe (52) by the crankshaft (50); and

connecting at least one hydraulically actuated valve (34a, 34b, 34c, 34d, 134a, 134b, 134c, 134d) to be controlled in fluid communication with the reciprocating fluid flow from the fluid pressure piston pump (36, 36a, 36b, 36c, 36d).

14. The method of claim 13 further comprising:

connecting a first control valve (56, 56a, 56b, 56c, 56d) for selectively directing reciprocal fluid flow between the fluid pressure piston pump (36, 36a, 36b, 36c, 36d) and an accumulator (46, 46a, 46b, 46c, 46d) to prevent actuation of the at least one hydraulically actuated valve (34a, 34b, 34c, 34d, 134a, 134b, 134c, 134d) to be controlled.

15. The method of claim 13 further comprising:

assembling the at least one hydraulically actuated valve to include a first hydraulically actuated valve (34a, 34c, 134a, 134c) and a second hydraulically actuated valve (34b, 34d, 134b, 134d); and

connecting a second control valve (64, 64a, 64b, 64c, 64d) for selectively controlling fluid communication between the reciprocating fluid flow and one of the first hydraulically actuated valve (34a, 34c, 134a, 134c) and the second hydraulically actuated valve (34b, 34d, 134b, 134d).