MXPA00004934A - Integrated lost motion system for retarding and egr - Google Patents

Abstract

A variably timed internal combustion engine valve actuation system (10) and method for opening valves in internal combustion engines. The system functions during both positive power and engine braking, to control the amount of"lost motion"between a valve (160) and a means for opening the valve (150). In particular, the invention relates to a lost motion engine valve actuation system (10) using dedicated cam (100) for effecting exhaust valve (160) openings for compression release braking and exhaust gas recirculation (EGR).

Description

LOST MOVEMENT SYSTEM INTEGRATED FOR DELAY AND RECIRCULATION OF EXHAUST GAS REFERENCES TO THE RELATED PATENT APPLICATIONS This application refers to and claims priority over the United States Provisional Patent Application Serial Number 60 / 066,702, entitled "Integrated Lost Motion System for Gas Delay and Recirculation. of Escape ", filed on November 21, 1997. FIELD OF THE INVENTION The present invention relates generally to systems and actuation methods of internal combustion engine valves variably timed to open valves in internal combustion engines. More specifically, the invention relates to systems and methods, used during positive energy and motor braking, to control the amount of "lost motion" between a valve and a means for opening the valve. In particular, the invention relates to a lost motion motor valve drive system that uses a dedicated cam to perform valve openings for compression release and exhaust gas recirculation braking ("EGR"). BACKGROUND OF THE INVENTION Compression release-type retarder or braking systems are well known in the art. Engine retarders temporarily convert a compression-ignition internal combustion engine into an air compressor to reduce engine speed. A compression release retarder reduces the kinetic energy of a motor by opposing the upward movement of the motor pistons in the compression stroke. As a piston travels upward in its upward compression stroke, the gases trapped in the cylinder are compressed. The compressed gases oppose the upward movement of the piston. When the piston approaches the top of its stroke, an exhaust valve is opened to release the compressed gases. After the pressure has been released from the cylinder, the piston can not recapture the energy stored in the compressed gases in the downward stroke of subsequent expansion. The braking system provides the operator with increased control over the vehicle. Properly designed and adjusted compression-type motor retarders can generate delay energy equal in magnitude to a substantial portion of the energy generated during positive energy operations. Compression release type retarders of this type complement the braking capacity of the primary braking system of a vehicle's tires. By doing so, these retarders can substantially extend the life of the primary braking system of the vehicle's tires. The hydraulic valve control systems of compression release engine retarders commonly have a number of components. A solenoid valve is commonly provided to control the supply of engine oil to the hydraulic circuit of the compression release engine retarder. A master piston engages the hydraulic valve control system, commonly on an exhaust cam or cam. The master piston is articulated to a piston derived through a hydraulic circuit. The branch piston is connected to an engine exhaust valve. When the compression release retarder is actuated, the exhaust cam or cam boss pushes against the master piston. The movement of the master piston is transferred to the piston bypassed through the hydraulic circuit causing the derived piston to actuate and open the exhaust valve at a point near the end of the compression stroke. Much of the potential energy created by compressing the gas in the cylinder is not recovered during the subsequent expansion or power stroke of the engine. Instead, it is dissipated through the exhaust systems and the engine radiator. By dissipating the energy developed by compressing the cylinder load, the compression release type retarder reduces vehicle speed. The effectiveness of engine braking can be improved through the use of exhaust gas recirculation. The exhaust gas can be recirculated in the cylinder at the moment when the cylinder piston is at or near the Lower Dead Center (BDC) at the start of the normal compression stroke. The recirculation of exhaust gas allows a greater volume of air to be admitted to the cylinder. Therefore, the engine works harder by compressing the denser air volume, and superior braking is achieved. The exhaust gas recirculation can also be used during normal positive energy operation. The benefits derived from the recirculation of positive energy exhaust gas are mainly reduced exhaust gas emissions. Exhaust gas recirculation and engine braking operations require that the cylinder exhaust valve be opened at times other than the normal positive energy openings. Engine braking requires that the exhaust valves open at or near the Top Dead Center (TDC) at the completion of a compression stroke of a cylinder; Exhaust gas recirculation at or near the Lower Dead Center at the beginning of the compression stroke. A typical engine exhaust valve operation system keeps the exhaust valve closed at this time. An engine may include a delay exhaust gas recirculation event, a positive energy exhaust gas recirculation event, or both. These events can be implemented as additional projections on a cylinder valve exhaust cam. It has been proposed to mount a separate addition system to the motor to significantly increase the externally installed dimensions. In addition, the exhaust valve cam may include a compression release brake lug, as well as the main exhaust event lug. The limited space in the exhaust valve cam makes it difficult to include projections for recirculation events of exhaust gas and positive gas recirculation events, together with projections for braking of compression release and the main escape event. The valve stroke profiles for the main exhaust event and the positive exhaust gas recirculation event can overlap. The after lap is not desirable because it can limit the motor's ability to achieve all the desired events. As a result, there is a need to provide a valve drive system that can accommodate multiple motor valve events. Current valve drive systems also have other deficiencies. In many internal combustion engines, the exhaust and inlet valves of the engine cylinder are opened and closed by fixed profile cams, and more specifically by one or more fixed projections that are an integral part of each of the cams. The use of fixed profile cams makes it difficult to make the necessary adjustments for timing and / or engine valve stroke amount for various conditions of or, such as different engine speeds. A method for adjusting the valve timing and timing has been to incorporate a "lost motion" device into the joint between the valve and the cam. The lost motion is the term applied to a class of technical solutions to modify the movement of the proscribed valve by a cam profile with a mechanical, variable or hydraulic length articulation means of another type. A cam shoulder provides the maximum movement (the longest stop and the largest stroke) necessary over a full range of engine operating conditions. In a lost motion system, a variable length system is included in the valve train joint to subtract or lose part or all of the movement imparted by the cam to the valve. This variable length system can when fully expanded, transmit all the movement of the cam to the valve, and when it is fully contracted, transmit no or a minimum amount of movement of the cam to the valve. An example of such a system is provided in U.S. Patent Serial No. 5,537,976 to Hu and U.S. Patent Serial No. 5,680,841 also to Hu, which are assigned to the same assignee as the present application and which are incorporated herein by reference. In the lost motion system of U.S. Patent Serial Number 5,680,841, (the "841 patent") a motor cam shaft drives a master piston that displaces fluid from its hydraulic chamber to a hydraulic chamber of a Derived piston. The derived piston in turn acts on the motor valve to open it. The lost motion system can be a solenoid valve and a check valve in communication with the hydraulic circuit including the chambers of the master and branch pistons. The solenoid valve can be maintained in a closed position to retain the hydraulic fluid in the circuit. While the solenoid valve remains closed, the derived piston and the engine valve respond directly to the movement of the master piston, which in turn displaces hydraulic fluid in direct response to the movement of a cam. When the solenoid opens temporarily, the circuit can be partially drained, and part or all of the hydraulic pressure generated by the master piston can be absorbed by the circuit instead of being applied to displace the branch piston. Previous lost motion systems have not used high-speed mechanisms to quickly vary the length of the lost motion system. These systems of lost motion have not been able to take more than one length during a single movement of cam projection, or even during a motor cycle. The use of a high-speed mechanism to vary the length of the lost motion system allows for more precise control over the valve drive, and therefore an optimum valve drive can be achieved for a wide range of conditions. of engine operation. As mentioned above, the efficiency and operation of the motor can be maximized through the use of events of recirculation of exhaust gas of negative and positive time variably timed. Similarly, braking operation can be improved by braking two cycles. A lost motion system can be used to implement these operations. In a lost motion system, the working fluid is drained and added at precise times to the hydraulic joint between the master piston and the branch piston. The profile of the motor valve can be modified by modifying the movement of the master piston, which follows a cam, prior to its transfer to the branch piston. In this way, variable timing is achieved. The recirculation of exhaust gas of negative and positively timed energy in a variable manner, as well as the braking of two cycles, can be difficult to achieve in an already exhausted exhaust valve cam with a main exhaust event relief and a projection of Compression release brake event due to inadequate base circle "residence time". The residence time refers to the amount of time in which the cam presents a zero stroke profile to the master cam or follower. This time is generally proportional to the amount of space on the cam not taken by different projections. An example of a lost movement system and method used to obtain exhaust gas recirculation and retardation is provided by US Pat. No. Ser. No. 5, 146,890 to Gobert (September 15, 1992) for a Method and a Motor Braking Device, a Four-Race Internal Combustion Engine, assigned to AB Volvo, and incorporated herein by reference. Gobert describes a method of conducting recirculation of exhaust gas by placing the cylinder in communication with the exhaust system during the first part of the compression stroke and optionally also during the last part of the intake stroke. Gobert uses a lost motion system to activate and deactivate the exhaust gas recirculation and delay, but such a system is not variable in a motor cycle. The '841 patent discloses an internal combustion engine with valves that are opened by cams that cooperate with hydraulic circuits that are partially controlled by electrically operated hydraulic fluid valves. The '841 patent system is limited by inadequate residence time since its system includes the use of a single cam to control all openings in the motor valve regardless of the mode of operation of the motor. As a result of the disadvantages of the existing motor valve drive systems. There is a need for a system that can accommodate all valve events necessary for efficient motor operation, including operations of recirculation of exhaust gas, compression release braking and positive energy. OBJECTS OF THE INVENTION Therefore, an object of the present invention is to provide an integrated variable motion and lost-motion valve drive system. A further object of the present invention is to provide a method and apparatus for controlling emissions by recirculating exhaust gas to the cylinders of the engine. A further object of the present invention is to provide variable exhaust gas recirculation capacity in an addition system without adding externally installed dimensions. Therefore, an object of the present invention is to provide a method and apparatus for recirculating exhaust gas during compression release braking. Another object of the present invention is to provide a method and apparatus for recirculating exhaust gas during positive energy. Another object of the present invention is to provide the use of a dedicated cam to implement negative and positive energy exhaust gas recirculation with lost motion. Still another object of the present invention is to provide a method and apparatus for optimizing the timing of the exhaust gas recirculation event for positive energy operation. Still another object of the present invention is to provide a method and apparatus for optimizing the magnitude of the exhaust gas recirculation event for positive energy operation. Still another object of the present invention is to provide a method and apparatus for optimizing the timing of the exhaust gas recirculation event for compression release braking operation. Yet another object of the present invention is to provide a method and apparatus for optimizing the magnitude of the exhaust gas recirculation event for compression release braking operation. Still another object of the present invention is to provide a method and apparatus for achieving improved delay operation. Still another object of the present invention is to provide a method and apparatus for achieving increased delay energy. Still another object of the present invention is to provide a method and apparatus for optimizing the operation of the compression release retarder at operating speeds other than the measured engine speed. Still another object of the present invention is to provide a method and apparatus for optimizing the operation of the compression release retarder at operating speeds other than the speed at which the compression release retarder is fixed in the installation. Another object of the present invention is to provide braking of two cycles. Additional objects and advantages of the invention are set forth, in part, in the description presented below and in part, will be apparent to those skilled in the art from the description and / or practice of the invention. BRIEF DESCRIPTION OF THE NONDION In response to this challenge, the Applicants have developed an innovative and economical internal combustion engine that includes: an engine cylinder exhaust valve that can be selectively opened and closed; a cam having a plurality of projections synchronized with openings of the engine cylinder exhaust valve for events of exhaust gas recirculation and engine braking; a hydraulic joint containing hydraulic fluid operatively coupled between the cam and the engine cylinder exhaust valve to selectively respond to the projections causing the valve to open; and means for controlling the pressure of the hydraulic fluid in the hydraulic fluid joint to selectively modify the openings of the cylinder valve of the engine in response to the projections, wherein the means for controlling the hydraulic fluid pressure is capable of maintaining the motor cylinder valve completely closed in response to a first projection and open in response to a second projection, each of the plurality of projections may be selected at different times to be either the first or the second of the projections. The means for controlling the hydraulic fluid pressure may comprise a control valve for selectively releasing hydraulic fluid from the hydraulic joint. The control valve may be a valve electrically operated by electronic circuits that include a microprocessor. The engine may also include a hydraulic fluid supply and a check valve to allow hydraulic fluid to flow from the supply to the hydraulic joint but not in an opposite direction. The hydraulic fluid supply may comprise an accumulator. The means for controlling the hydraulic fluid pressure may comprise an electrically operated valve for releasing hydraulic fluid selectively from the hydraulic joint to the accumulator. The hydraulic joint may comprise: a master piston that alternates in response to the flow and pressure of the hydraulic fluid in the hydraulic joint to selectively open the exhaust valve of the engine cylinder. The hydraulic joint may be arranged in an exhaust cam that rotates in response to the projections. The motor may include a bypass piston placed on the exhaust cam, the reciprocating bypass piston relative to the exhaust cam in response to the flow and pressure of the hydraulic fluid in the hydraulic joint to selectively open the engine cylinder valve . In an alternative embodiment, the present invention may comprise an internal combustion engine capable of operating in braking and energy modes and providing recirculation of exhaust gas in any manner comprising: a reciprocating engine piston mounted in a racing cylinder of successive cyclic expansion and compression; an exhaust valve that can be operated to open near the end of an expansion stroke of the engine piston when the engine is operated in an energy mode and operable to open in a variable timed relationship with the compression stroke of the engine piston when the engine is operated in braking mode; a first exhaust valve actuation means for imparting reciprocal movement to the exhaust valve when the engine is operated in the power mode; and a second exhaust valve actuation means for imparting reciprocating movement to the exhaust valve when the engine is operated in the braking mode and when recirculation of exhaust gas is required. The second exhaust valve actuation means may comprise: a second cam having a plurality of projections synchronized with openings of the exhaust valve of the engine cylinder for engine braking events and for exhaust gas recirculation; a second hydraulic linkage containing hydraulic fluid operatively coupled between the second cam and the exhaust valve of the engine cylinder to selectively respond to the projections causing the valve to open. The engine may also include a means for controlling the hydraulic fluid pressure in the second hydraulic fluid joint to selectively modify the openings of the engine cylinder valve in response to the projections., wherein the means for controlling the hydraulic fluid pressure is capable of maintaining the motor cylinder valve completely closed in response to a projection. The first valve actuating means may comprise: a first cam having a projection synchronized with openings in the exhaust valve of the engine cylinder for power events; a first hydraulic joint containing hydraulic fluid operatively coupled between the cam and the exhaust valve of the engine cylinder to selectively respond to the projections causing the valve to open. The first hydraulic joint can be placed on an exhaust cam that rotates in response to the projections. The motor may additionally include a branched piston placed in the exhaust cam, the diverted piston being reciprocable relative to the exhaust cam in response to the flow and pressure of the hydraulic fluid in the first hydraulic link to open in a manner selective exhaust valve of the engine cylinder. The engine may also include a means for controlling the hydraulic fluid pressure in the first hydraulic fluid joint to selectively reduce the pressure in the joint so that the exhaust valve will not open in response to movement of the exhaust cam . Another embodiment of the present invention may be an internal combustion engine capable of operating in an energy mode or a braking mode comprising: a motor piston reciprocally mounted in a cylinder for successive cyclic expansion and compression strokes; an exhaust valve that can be operated to open near the end of an expansion stroke of the engine piston when the engine is operated in an energy mode and operable to open in a variable timed relationship with the compression stroke of the engine piston when the engine is operated in braking mode; a first exhaust valve actuation means for opening the exhaust valve when the engine is operated in the power mode; a second means of actuating an exhaust valve to open the exhaust valve when the engine is operated in the braking mode; wherein the second exhaust valve actuation means opens the exhaust valve for recirculation of exhaust gas. The second exhaust valve actuation means is independent of the first exhaust valve actuation means. It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed.

The accompanying drawings, which are incorporated herein by reference, and which form a part of this specification, illustrate certain embodiments of the invention and, together with the detailed description, serve to explain the principles of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS. Figure 1 is a graph showing valve stroke profiles for the inlet valve event and for various exhaust valve events, as well as the exhaust gas recirculation cam profile and unmodified braking. Figure 2 is a schematic cross-sectional view showing one embodiment of the invention. Figure 3 is a schematic cross-sectional view showing one embodiment of the invention having a hydraulic lifter to deactivate the main escape event. DETAILED DESCRIPTION OF THE INVENTION The invention is first described with reference to Figure 1. Figure 1 discloses a graph of valve stroke profiles for the exhaust and inlet valves of a motor cylinder against the crank angle of the distribution shaft . The magnitude of the stroke of the valve is shown on the vertical axis 100. The degree of rotation of the distribution shaft is shown on the horizontal axis 200. The cam projection profile for a dedicated cam according to the present invention is shown through curve 300 in the upper portion of the graph. Curve 300 represents a cam profile for a dedicated exhaust valve cam having a compression relief brake lining, a positive exhaust gas recirculation projection (doubles as a second brake lining), and a projection flange. Negative exhaust gas recirculation. The cam highlights of the main escape event and the cam projections of the main entry event are in separate cams. By implementing the braking event and exhaust gas recirculation highlights on a dedicated cam cam of the main exhaust event it is possible to achieve positive energy exhaust gas recirculation with improved functionality as well as optimize compression release braking. Attempting to implement a positive energy exhaust gas recirculation in a standard exhaust cam would likely result in overlap in the main exhaust bosses and positive energy exhaust gas recirculation. In the present invention, the positive energy exhaust gas recirculation event does not overlap with the events of negative energy exhaust gas recirculation and compression release braking. The valve events that would be combined in the dedicated cam are the compression release braking event 410, the positive energy exhaust gas recirculation event 440, and the negative energy 450 exhaust gas recirculation event. main escape event 420 and main entrance event 430 would be triggered by different cams. As can be seen from the curves, the positive energy exhaust gas recirculation event 440 and the main exhaust event 420 overlap. In the present invention, two-cycle braking can be implemented using the same projection used for recirculation of positive energy exhaust gas. A hydraulic lifter can be used to reduce the main exhaust event 420 to perform and achieve two-cycle braking. Reducing the main exhaust event is necessary to transform the engine exhaust stroke into a second compression stroke. Each event would be used to obtain brake gas recirculation (BGR) for the second brake event. The embodiment of the invention employing the hydraulic lifter is shown in Figure 3. A valve actuation system 10 in accordance with the present invention is shown in Figure 2. This system includes a dedicated cam 100 with projections for an event of compression release braking 102 and an exhaust gas recirculation event 103. The projections actuate a master piston 140. The present invention includes a cam with at least one compression release braking projection, but may include many different cam configurations including the one shown in Figure 1. The master piston moves in response to a cam roller 141. Any cam roller configuration, such as an oscillating roller, a flat roller, or a rotating roller, can be used, as shown in Figure 2. As shown, the master piston 140 is connected to a branch piston 150 by a derivative master hydraulic circuit. It is within the scope of the invention to employ a separate exhaust cam in place of a hydraulic joint. The circuit includes a high pressure passage 170 that connects the master piston 140 to the branch piston 150. The branch piston is housed in a housing 152. In alternative embodiments of the invention, the passages shown in Figure 2 can be included in tubes external. The branch piston 150 is moved to drive the exhaust valves 160. A two-way, high-speed solenoid valve 120 is provided to control the pressure in the hydraulic circuit 170. The hydraulic working fluid can be provided from the lubricating oil system 1 motor 10. The system may additionally include an accumulator 130 to provide an expansion volume for pressurized hydraulic fluid. The present invention provides "lost motion". The valve 120 can be controlled to eliminate or vary valve events as required. For example, when it is necessary to eliminate a valve event, the valve 120 performs a stroke to connect the hydraulic passages 171 and 172 allowing a pressurized fluid in the circuit 170 to drain the accumulator 130. When the master piston 140 performs a stroke, the movement is not transferred to the branch piston 150. The movement is absorbed by the accumulator 130. The exhaust valves 160 do not perform a stroke. The control signals for the valve 120 may be provided by electronic circuits which may include a microprocessor. Referring now to Figure 3, the system in accordance with the present invention may also include a hydraulic lifter to deactivate the main escape event. A hydraulic lifter can be used to deactivate the main exhaust event by achieving two-cycle braking. Deactivating the main exhaust event is necessary to transfer the exhaust race of the engine in a second compression stroke. With reference to Figure 3, the distribution shaft 550 includes a main exhaust event protrusion 551 which imparts movement to the exhaust cam 500. The hydraulic lifter member 520 in the exhaust cam 500 acts on the exhaust bridge 180 to operate the exhaust valves 160 to perform the main exhaust event. The hydraulic fluid in passage 510 can be drained and re-filled as necessary to deactivate and activate the main escape event or portions of the main escape event, as desired. The branch piston 150 drives the exhaust valves 160 via the dedicated distribution shaft circuit shown in Figure 2, as mentioned above.

It will be apparent to those skilled in the art that various modifications and variations may be made in the construction and configuration of the present invention without departing from the scope or spirit of the invention. Various modifications and variations may be made in the construction of the valve drive system without departing from the scope or spirit of the use of the invention of a dedicated cam. For example, the displacement of the cam shoulder can be transferred to the motor valve by means of an exhaust cam or hydraulic circuit. Additionally, it may be appropriate to make additional modifications, such as different configurations of valve oscillators, thrust tubes, cam rollers, etc. , to form the valve drive train. Therefore, it is intended that the present invention cover the modifications and variations of the invention as long as they are within the scope of the appended claims and their equivalents.

Claims (12)

1. REVIVAL DICATIONS 1. An internal combustion engine having at least one positive energy operating mode and one engine braking operation mode, said engine comprising: at least one exhaust valve of the engine cylinder, said at less an exhaust valve of the engine cylinder is operated selectively between an open position and a closed position; a cam assembly having a plurality of projections therein, wherein said plurality of projections allows the selective opening of said at least one exhaust valve of the engine cylinder during the positive energy operation mode and the braking mode motor; an articulation assembly that is operatively coupled between said cam and such at least one exhaust valve of the engine cylinder to selectively respond to said plurality of projections to selectively open said at least one exhaust valve; and a control means for controlling said articulation assembly to selectively modify the openings of such a motor cylinder valve in response to said plurality of projections, wherein said control means operates such a joint assembly to selectively operate said valve. exhaust to produce at least one exhaust gas recirculation event during the positive energy operation mode and at least one exhaust gas recirculation event during the engine braking operation mode. The motor according to claim 1, wherein said plurality of projections includes a first projection to produce at least one exhaust gas recirculation event during the positive energy operation mode, and a second projection to produce for at least one event of recirculation of exhaust gas during the engine braking operation mode. The motor according to claim 2, wherein said first projection is operative during such motor braking operation mode to produce two cycle braking. The motor according to claim 1, wherein said articulation assembly is a lost movement articulation assembly. The motor according to claim 4, wherein said articulation assembly comprises: a master piston alternating in response to said plurality of projections; and a branched piston that alternates selectively in response to the operation of said master piston to selectively open said exhaust valve of the engine cylinder. The engine according to claim 4, wherein said articulation assembly is positioned within an exhaust cam assembly positioned between said cam and said at least one exhaust valve of the engine cylinder. The engine according to claim 1, wherein said control means controls the operation of the at least one exhaust valve to optimize at least one of the timing and magnitude of the exhaust gas recirculation event during the positive energy operation mode. The engine according to claim 1, wherein said control means controls the operation of the at least one exhaust valve to optimize at least one of the timing and magnitude of the exhaust gas recirculation event during the Engine braking operation mode. 9. A method for operating an internal combustion engine during a positive energy operation mode and an engine braking operation mode, said method comprising the steps of: selectively operating at least one exhaust valve in response to a first cam shoulder to produce at least one exhaust gas recirculation event during the positive energy operation mode; and selectively operating the at least one exhaust valve in response to a second cam shoulder to produce at least one exhaust gas recirculation event during the engine braking operation mode. 1 0. The method of claim 9, which additionally comprises the step of: selectively operating the at least one exhaust valve in response to the first cam shoulder during the motor braking operation mode for performing two-cycle braking. The method according to claim 9, wherein said step of selectively operating the at least one exhaust valve in response to the first cam shoulder includes the step of optimizing at least one of the timing and magnitude. of the exhaust gas recirculation event during the positive energy operation mode. The method according to claim 9, wherein said step of selectively operating the at least one exhaust valve in response to the second cam shoulder includes the step of optimizing at least one of the timing and magnitude of the Exhaust gas recirculation event during the engine braking operation mode. RESU MEN A variably timed internal combustion engine valve drive system (10) and a method for opening valves in internal combustion engines. The system operates during positive energy and motor braking to control the amount of "lost motion" between a valve (160) and a means to open the valve (150). In particular, the invention relates to a lost motion motor valve drive system (10) using a dedicated cam (100) to perform exhaust valve openings (160) for compression release and gas recirculation braking. of escape (EG R).