System and method for improving performance of hydraulic actuating system

Abstract

A system and method is disclosed for supplying hydraulic fluid to a lost motion system in an internal combustion engine. The system may comprise a reservoir; a gallery circuit connected to the reservoir, wherein the gallery circuit is adapted to be connected to the one or more lost motion systems; and a control valve adapted to provide selective hydraulic communication between the gallery circuit and the one or more lost motion systems.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application relates to and claims priority on U.S. Provisional Application No. 60/468,088, filed May 6, 2003 and entitled “Hydraulic Circuit to Improve Starting of Hydraulic Actuating System,” a copy of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to systems and methods of improving the performance of a hydraulic system. In particular, the present invention relates to a reservoir system and method using same that provides hydraulic fluid to a lost motion system disposed in an internal combustion engine and used to actuate engine valves.

BACKGROUND OF THE INVENTION

Valve actuation in an internal combustion engine is required in order for the engine to produce positive power, as well as to produce engine braking. During positive power, intake valves may be opened to admit fuel and air into a cylinder for combustion. The exhaust valves may be opened to allow combustion gas to escape from the cylinder.

During engine braking, the exhaust valves may be selectively opened to convert, at least temporarily, an internal combustion engine of compression-ignition type into an air compressor. This air compressor effect may be accomplished by cracking open one or more exhaust valves near piston top dead center position for compression-release type braking, or by maintaining one or more exhaust valves in a cracked open position for much or all of the piston motion for bleeder type braking. In doing so, the engine develops retarding horsepower to help slow the vehicle down. This can provide the operator increased control over the vehicle and substantially reduce wear on the service brakes of the vehicle. A properly designed and adjusted engine brake can develop retarding horsepower that is a substantial portion of the operating horsepower developed by the engine in positive power.

For both positive power and engine braking applications, the engine cylinder intake and exhaust valves may be opened and closed by fixed profile cams in the engine, and more specifically by one or more fixed lobes which may be an integral part of each of the cams. The use of fixed profile cams can make it difficult to adjust the timings and/or amounts of engine valve lift needed to optimize valve opening times and lift for various engine operating conditions, such as different engine speeds.

One method of adjusting valve timing and lift, given a fixed cam profile, has been to incorporate a “lost motion” device in the valve train linkage between the valve and the cam. Lost motion is the term applied to a class of technical solutions for modifying the valve motion proscribed by a cam profile with a variable length mechanical, hydraulic, or other linkage means. An example of a lost motion system 100 is shown in FIG. 1. The lost motion system 100 may include a master piston 110 hydraulically linked to a slave piston 120 by the hydraulic passage 130. A check valve 140 allows hydraulic fluid to be supplied to and retained in the hydraulic passage 130. A control valve 150 permits fluid in the hydraulic passage 130 to be selectively released. In connection with the lost motion system 100, a cam 200 may provide the “maximum” (longest dwell and greatest lift) motion needed for engine operating conditions.

The lost motion system 100 may be included in the valve train linkage, intermediate of the valve 300 to be opened and the cam 200 providing the maximum motion. Cam motion imparted to the master piston 110 may be transferred to the slave piston 120, and thus the engine valve 300, when the hydraulic passage 130 is full of fluid. In this manner, the engine valve 300 (e.g., exhaust or intake valve), may be actuated by the lost motion system only when hydraulic fluid is maintained in the hydraulic passage 130. Selective operation of the control valve 150 allows the lost motion system to subtract or lose part or all of the motion imparted by the cam to the master piston 110 by releasing fluid from the hydraulic passage 130.

Other examples of such systems are provided in U.S. patent application serial number Vorih et al., U.S. Pat. No. 5,829,397 (Nov. 3, 1998), Hu, U.S. Pat. No. 6,125,828 (Oct. 3, 2000), and Hu, U.S. Pat. No. 5,680,841 (Oct. 28, 1997), which are assigned to the same assignee as the present application, and which are incorporated herein by reference.

Lost motion systems, while beneficial in many aspects, have also been subject to some drawbacks. The use of hydraulics may result in initial starting difficulties as the result of a lack of hydraulic fluid in the system. With respect to the lost motion system 100 shown in FIG. 1, for example, when the engine in which it is installed is shut off for a period of time, fluid in the hydraulic passage 130 may drain out of the system due to leakage past the master piston 110, the slave piston 120, the check valve 140, and/or the control valve 150. As a result, when the engine is started there may be no fluid in the hydraulic passage 130 to enable motion from the cam 200 to be transferred to the engine valve 300. The oil supply pump (not shown) that provides hydraulic fluid to the passage 130 may not be capable of supplying fluid quickly enough. In some instances, it is possible that the hydraulic passage 130 may not be completely filled until more than a minute after initial cranking of the engine. In a multi-cylinder engine, there may be numerous lost motion systems 100 that must be charged with hydraulic fluid.

If actuation of the engine valve 300 is required immediately during engine starting, as is often the case with variable valve actuation (WA) systems, this lack of hydraulic fluid can frustrate and prevent starting, or cause engine damage. It may be particularly difficult to charge the system 100 with hydraulic fluid when the fluid is cold and has a lower viscosity.

It is therefore an advantage of some, but not necessarily all, embodiments of the present invention to improve upon charging a lost motion valve actuation system with hydraulic fluid.

Operation of the lost motion system 100 may also be interfered with by the presence of air in the hydraulic passage 130 connecting the master and slave pistons. Air is not a hydraulic fluid, but rather a compressible fluid. Air entrained in the hydraulic passage 130 can cause the hydraulic circuit to compress instead of transferring motion from the master piston 110 to the slave piston 120. This can result in loss of the cam motion even when it is desired that it not be lost.

It is therefore an advantage of some, but not necessarily all, embodiments of the present invention to improve upon the venting of air from the hydraulic circuit connecting the master piston to the slave piston in a lost motion system.

Additional advantages of various embodiments of the invention are set forth, in part, in the description that follows and, in part, will be apparent to one of ordinary skill in the art from the description and/or from the practice of the invention.

SUMMARY OF THE INVENTION

Responsive to the foregoing challenges, Applicant has developed an innovative reservoir system for supplying hydraulic fluid to a lost motion system in an internal combustion engine. In one embodiment, the system comprises: a reservoir; a gallery circuit connected to the reservoir, wherein the gallery circuit is adapted to be connected to one or more lost motion systems; and a control valve adapted to provide selective hydraulic communication between the gallery circuit and the one or more lost motion systems.

Applicant has further developed an innovative method of providing hydraulic fluid to a lost motion system during start up of an internal combustion engine. In one embodiment, the method comprises the steps of: providing hydraulic fluid in a reservoir, the reservoir being disposed relative to the lost motion system to facilitate the flow of hydraulic fluid to the lost motion system under the influence of gravity; blocking hydraulic communication between the reservoir and the lost motion system during application of at least an initial portion of an engine valve event motion to the lost motion system; and providing hydraulic communication between the reservoir and the lost motion system during application of at least a later portion of the engine valve event motion to the lost motion system.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to assist the understanding of this invention, reference will now be made to the appended drawings, in which like reference characters refer to like elements.

FIG. 1 is a cross-section of a lost motion valve actuation system.

FIG. 2 is a cross-section of a lost motion valve actuation system including a system for charging the lost motion valve actuation system with hydraulic fluid in accordance with a first embodiment of the present invention.

FIG. 3 is a cross-section of a lost motion valve actuation system including a system for charging the lost motion valve actuation system with hydraulic fluid in accordance with an alternative embodiment of the present invention.

FIG. 4 is a cross-section of a portion of a lost motion valve actuation system including an orthogonal master-slave piston arrangement in accordance with an alternative embodiment of the present invention.

FIG. 5 is a graph of crank angle position versus cam lobe motion and control valve position which illustrates an example of control valve timing that may be employed in a method embodiment of the present invention.

FIG. 6 is a cross-section of a lost motion valve actuation system including a system for charging the lost motion valve actuation system with hydraulic fluid in accordance with an alternative embodiment of the present invention.

FIG. 7 is a cross-section of a lost motion valve actuation system including a system for charging the lost motion valve actuation system with hydraulic fluid in accordance with an alternative embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Reference will now be made in detail to a first embodiment of the present invention, an example of which is illustrated in the accompanying drawings. With reference to FIG. 2, each lost motion system 100 may be disposed between a cam 200 and an engine valve 300. The cams 200 may include one or more cam lobes 210, 220, etc., for imparting an engine valve actuation motion to the lost motion system 100. The lost motion system 100 is shown to act on a single engine valve 300, however, it is appreciated that the lost motion system 100 may act on more than one engine valve through a valve bridge in alternative embodiments.

In one embodiment of the present invention, as shown in FIG. 2, each lost motion system 100 may include a master piston 110 hydraulically linked to a slave piston 120 by a hydraulic passage 130. A control valve 150 is disposed in the hydraulic passage 130 so that it may selectively block or unblock the hydraulic passage. Electronic or mechanical control of the control valve 150 permits fluid to enter the hydraulic passage 130 when the control valve 150 is in an open position (as shown). When the control valve 150 is closed (downward as shown in FIG. 2), hydraulic fluid is trapped in the passage 130, thereby hydraulically locking the master piston 110 to the slave piston 120. Reopening the control valve 150 may also allow fluid in the passage 130 to be selectively released, thereby unlocking the master piston 110 from the slave piston 120.

An optional accumulator piston 160 may assist in maintaining low pressure fluid in the vicinity of the hydraulic passage 130 so that it may be drained and refilled rapidly. The optional accumulator piston 160 may be particularly useful when the lost motion system 100 is used to provide variable valve actuation. In the instances where variable valve actuation is provided, the control valve 150 may be a high-speed trigger valve. High-speed trigger valves may be capable of being opened and closed one or more times per engine cycle to enable locking and unlocking the master piston 110 from the slave piston 120 one or more times per engine cycle.

Hydraulic fluid may be supplied to the hydraulic passage 130 by the reservoir system 400. The reservoir system 400 may include a reservoir 410, a low pressure feed 420, an optional check valve 430, an inlet port 440, an air bleed opening 450, and a common gallery circuit 460. Hydraulic fluid, such as, for example, engine oil, may be provided from the low pressure feed 420 to the reservoir 410. The optional check valve 430 may prevent hydraulic fluid in the reservoir 410 from flowing back to the low pressure feed 420.

In one embodiment of the present invention, the reservoir system 400 may include an air bleed opening 450 near the top of the reservoir 410. The air bleed 450 may allow air entrained in the hydraulic fluid that enters the reservoir 410 from the low pressure feed 420 to exit the system before it enters the one or more lost motion systems 100. The air bleed opening 450 may be sized to allow small quantities of air to exit from the reservoir system 400 freely, while still offering restriction to the exit of hydraulic fluid, even at relatively high pressure. The air bleed 450 may also allow air to enter the reservoir 410 to make up for hydraulic fluid that is fed by the reservoir to the gallery circuit 460. This may prevent a vacuum effect from preventing hydraulic fluid from flowing out of the reservoir 410 under a relatively small gravitational force. Still further, the air bleed 450 may permit air that does become entrained in the hydraulic fluid of the lost motion systems 100 to bubble up and out of these systems over time.

The inlet port 440 may be located near the top of the reservoir 410. Placement of the inlet port 440 near the top of the reservoir 410 may enhance the ability of the reservoir system 400 to allow air entrained in the fluid provided by the low pressure feed 420 to exit through the air bleed 450.

The gallery circuit 460 may provide hydraulic fluid from the reservoir system 400 to each of the possible plurality of lost motion systems 100. The reservoir system 400 may be located at any point along the expanse of the gallery circuit 460. The upper level of hydraulic fluid in the reservoir 410 may be above the level of the hydraulic passages 130 so that gravity can facilitate the flow of hydraulic fluid from the reservoir to the hydraulic passages.

It is appreciated that in alternative embodiments, more than one reservoir system could be provided to service the lost motion systems 100 included in the engine. In fact, each lost motion system 100 may benefit from incorporating a reservoir system 400 local to the lost motion system. These local reservoir systems 400 may be integrally incorporated into the housing of each lost motion system 100.

It is appreciated that the low pressure feed 420 need not connect directly to the reservoir 410. With reference to FIG. 3 for example, the low pressure feed 420 may connect to the gallery circuit 460 directly, instead of connecting through the reservoir 410.

In one embodiment, as shown in FIG. 6, the lost motion system 100 may further comprise an optional passage 170 for bypassing the control valve 150, and an optional check valve 175 disposed in the passage 170. The optional passage 170 and check valve 175 may permit hydraulic fluid to enter and refill the hydraulic passage 130 when there is insufficient time to open the control valve 150 between engine valve events, for example, in a variable valve actuation system.

With renewed reference to FIG. 2, operation of the lost motion system 100 may begin by filling the reservoir 410 with hydraulic fluid from the low pressure feed 420. The optional check valve 430 permits hydraulic fluid flow into the reservoir 410 from the low pressure feed 420, but does not permit a substantial amount of fluid to flow back to the low pressure feed from the reservoir.

As will be apparent to those of ordinary skill in the art, the control valve 150 may be normally open, or normally closed. For illustrative purposes, as shown in FIG. 2, an embodiment of the present invention including a normally open control valve 150 will be described. Embodiments of the present invention may use either a normally open or a normally closed control valve 150.

At the time that the engine is shut down, the reservoir 410 may contain a substantial amount of hydraulic fluid. At this time each of the control valves 150 open, thereby connecting the hydraulic passage 130 from the gallery circuit 460 and the reservoir 410, as shown in FIG. 2. Over time, hydraulic fluid may leak out of the hydraulic passage 130 due to leakage past the master piston 110 and the slave piston 120. Hydraulic leakage may also occur past the accumulator 160. Features of various embodiments of the present invention, however, may limit the amount of leakage past these and other system components, which could deplete the level of hydraulic fluid in the reservoir 410. First, the accumulator 160 may be disposed so that it is inverted as compared to its position shown in FIG. 2. The accumulator 160 position in FIG. 2 is provided for ease of illustration, and is not intended to show the only, or even preferred, positioning of the accumulator. Second, the master piston 110 and/or the slave piston 120 may be inverted to limit the drainage of hydraulic fluid. Third, the reservoir 410 may be provided with a sufficiently great amount of hydraulic fluid that it will continue to retain a useful amount of fluid over a prolonged period even if a low to moderate level of fluid leakage occurs past the accumulator 160. Fourth, the bottom of the reservoir 410 may be positioned below the level of the gallery circuit 460 such that the fluid in the reservoir 410 is prevented from being entirely drained out. Fifth, the reservoir feed 440 may be positioned at the top of the reservoir 410 to prevent hydraulic fluid drainage into the engine should the check valve 430 fail or be absent. Some, but not necessarily all, embodiments of the present invention may include one or more of these features.

At the time of engine start up, the hydraulic passage 130 may be so depleted of hydraulic fluid that displacement of the master piston 110 fails to result in sufficient displacement of the slave piston 120 to produce a desired actuation of engine valve 300. Hydraulic fluid may be supplied by the reservoir 410 to the hydraulic passage 130 at this time. The supply of fluid to the hydraulic passage 130 may begin by opening the control valve 150. By opening the control valve 150, fluid is permitted to flow from the reservoir 410, through the gallery circuit 460 to the hydraulic passage 130. The gallery circuit 460 may be located relative to the individual lost motion systems 100 so that gravity encourages the flow of fluid from the gallery circuit to the individual lost motion systems.

The flow of fluid into each of the hydraulic passages 130 may be further encouraged by the pumping action of the master piston 110 in conjunction with selective control of the control valve 150. As the master piston 110 pumps downward with each revolution of the cam 200, the control valve 150 may be open so that fluid may be drawn into the hydraulic passage 130 by the vacuum created by the master piston. As the master piston 110 pumps back upward under the influence of the main exhaust lobe on the cam 200, the control valve 150 may be maintained closed so that the master piston 110 does not drive fluid back out of the hydraulic passage 130. This cycle may be repeated until the passage 130 and accumulator 160 are refilled with fluid.

In addition, the high pressure generated in the master-slave circuit may force any air in the circuit out past the close clearance between the master piston 110 and the slave piston 120 and their respective bores. In one embodiment of the present invention, as shown in FIG. 4, the master piston 110 may be disposed in a direction substantially orthogonal or perpendicular to the orientation of the slave piston 120, such that any air in the circuit may be located at the piston/bore interface and may be readily forced out.

An example of the control valve timing that may be used to further enhance the refilling of the lost motion system 100 is provided in FIG. 5. The cam may be provided with one or more cam lobes that provide a main exhaust motion 500 and a compression release motion 510, for example. The control valve position may be maintained in an open position until just prior to the main exhaust motion 500. At this time the control valve may be closed, and maintained closed until approximately the mid-point of the main exhaust motion 500, at which time the control valve may be re-opened. This timing may be used during the first part of cranking (engine start-up) to facilitate refilling of the circuits, after which time the normal starting valve motion may be generated. It is contemplated that the control valve timing of embodiments of the present invention may be used in conjunction with other engine valve events, such as, a main intake valve event and an engine braking valve event.

It will be apparent to those skilled in the art that variations and modifications of the present invention can be made without departing from the scope or spirit of the invention. For example, as shown in FIG. 7, the one or more lost motion systems 100 may include a collapsible tappet assembly 180 operatively connected to a rocker arm 182, which, in turn, is operatively connected to one or more engine valves 300. Other embodiments of the one or more lost motion systems 100 for selectively losing part or all of the motion imparted to the system 100 are considered well within the scope and spirit of the present invention.

Claims

1. A system for supplying hydraulic fluid to one or more lost motion systems in an internal combustion engine, comprising:

a reservoir;

a gallery circuit connected to said reservoir, wherein said gallery circuit is adapted to be connected to the one or more lost motion systems; and

a control valve adapted to provide selective hydraulic communication between said gallery circuit and the one or more lost motion systems.

2. The system of claim 1 further comprising an air bleed opening provided in said reservoir.

3. The system of claim 1 wherein said gallery circuit is disposed relative to the one or more lost motion systems to facilitate the flow of hydraulic fluid from said gallery circuit to the one or more lost motion systems under the influence of gravity.

4. The system of claim 1 wherein said reservoir is disposed relative to the one or more lost motion systems to facilitate the flow of hydraulic fluid from said reservoir to the one or more lost motion systems under the influence of gravity.

5. The system of claim 1 further comprising means for selectively opening said control valve during an engine start up period.

6. The system of claim 1 further comprising a hydraulic fluid supply passage for supplying hydraulic fluid to the reservoir system.

7. The system of claim 6, wherein said fluid supply passage connects to an inlet port in said reservoir.

8. The system of claim 7, wherein the inlet port is disposed proximate the top of said reservoir.

9. The system of claim 6, wherein said fluid supply passage connects to said gallery circuit.

10. The system of claim 6, a check valve disposed in said fluid supply passage.

11. The system of claim 1, wherein the lost motion system comprises:

a master piston;

a slave piston; and

a hydraulic passage operatively connecting said master piston to said slave piston.

12. The system of claim 11, wherein said master piston is disposed in a direction substantially orthogonal to the direction of said slave piston.

13. The system of claim 11, wherein at least one of said master piston and said slave piston is inverted.

14. The system of claim 11, further comprising an accumulator piston disposed proximate said hydraulic passage.

15. The system of claim 11, wherein the level of hydraulic fluid in said reservoir is above the level of said hydraulic passage.

16. The system of claim 11, further comprising:

a bypass passage providing hydraulic fluid bypass of said control valve; and

a check valve disposed in said bypass passage.

17. A hydraulic actuating system in a multi-cylinder internal combustion engine, said system comprising:

a plurality of lost motion systems, wherein one lost motion system is provided for each cylinder in the multi-cylinder engine;

a reservoir;

a gallery circuit connected to said reservoir, wherein said gallery circuit is adapted to be connected to said plurality of lost motion systems; and

a control valve adapted to provide selective hydraulic communication between said gallery circuit and said plurality of lost motion systems.

18. The system of claim 17, further comprising means for selectively opening said control valve during an engine start up period.

19. The system of claim 17, wherein said gallery circuit is disposed relative to said lost motion systems to facilitate the flow of hydraulic fluid from said gallery circuit to said lost motion systems under the influence of gravity.

20. The system of claim 17, wherein said reservoir is disposed relative to said lost motion systems to facilitate the flow of hydraulic fluid from said reservoir to said lost motion systems under the influence of gravity.

21. A method of providing hydraulic fluid to a lost motion system during start up of an internal combustion engine, said method comprising the steps of:

providing hydraulic fluid in a reservoir, the reservoir being disposed relative to the lost motion system to facilitate the flow of hydraulic fluid to the lost motion system under the influence of gravity;

blocking hydraulic communication between the reservoir and the lost motion system during application of at least an initial portion of an engine valve event motion to the lost motion system; and

providing hydraulic communication between the reservoir and the lost motion system during application of at least a later portion of the engine valve event motion to the lost motion system.

22. The method of claim 21, wherein the engine valve event comprises a main exhaust event.

23. The method of claim 21, further comprising the step of venting air from the reservoir through an air bleed opening provided in said reservoir.