MXPA00004935A - Device to limit valve seating velocities in limited lost motion tappets - Google Patents

Abstract

An internal combustion engine valve actuation system (10) is disclosed. The present invention provides a hydraulic actuator for operating an engine valve (300), which includes a control element (120) for controlling the seating velocity of the valve. The present invention provides for free, unrestricted movement of the valve during opening, and an unrestricted return of the valve until the valve is within a predetermined distance of the valve seat. Once within this predetermined range, the return velocity of the engine valve is limited by the rate at which a fluid may escape through a flow restriction. The restriction is calibrated to provide the desired maximum valve seating velocity.

Description

DEVICE FOR LIMITING VALVE SEAT SPEEDS IN MOVING IMPULSORS LOST MITTED CROSS REFERENCE TO RELATED PATENT APPLICATIONS This application concerns and claims priority over United States Provisional Patent Application Serial Number 60 / 066,378, entitled "Device to Limit Valve Seat Speeds in Lost Motion Impellers. Limited, "filed on November 21, 1997. FIELD OF THE NINETION The present invention relates generally to systems and methods for opening 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. The invention also relates to a means for controlling the speed of the valve seat. BACKGROUND OF THE INVENTION In many internal combustion engines, the exhaust and inlet valves of the engine cylinder can be opened and closed by fixed profile cams on the engine, and more specifically by one or more fixed projections that can be an integral part of each of the cams. The use of fixed profile cams makes it difficult to adjust the timing and / or engine valve stroke amounts to optimize the stroke and valve opening times for various engine operating conditions, such as different engine speeds. A method to adjust the stroke and timing of the valve, given a fixed cam profile, has been incorporated into a "lost motion" device in the valve train 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 articulation means of varying length, hydraulic or otherwise. In a lost motion system, a cam shoulder can provide the "maximum" movement (the longest stop and the largest stroke) necessary over a full range of engine operating conditions. Then, a system of variable length can be included in the valve train joint, intermediate valve to be opened and the cam that provides the maximum movement, to subtract or lose part or all of the movement imparted by the cam to The valve. This variable length system (or lost motion 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 and method is provided in U.S. Patent Serial No. 5,537,976 of Hu and U.S. Patent Serial No. 5,680,841 also from Hu, which are assigned to same assignee of the present application and which are incorporated herein by reference. In the lost motion system of US Pat. No. 5,680,841, a motor cam can drive a master piston that moves fluid from its hydraulic chamber to a hydraulic chamber of a branch 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 master and branch piston chambers. 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 branch 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. Common lost motion systems have not had the combined ability to provide an adequate fail-safe or "flexible base" mode of operation and to provide varying degrees of valve stroke over an entire range of cam shoulder positions. In previous lost motion systems, a leaky hydraulic circuit could deactivate the ability of the master piston to open its or its associated valves. If a large enough number of valves can not be opened, the motor can not be operated. Therefore, it is important to provide a lost motion system that allows the motor to operate at some minimum level (ie, at a flexible base level) if the hydraulic circuit of this system develops a leak. A flexible base mode of operation can be provided using a lost motion system that still transmits a portion of the cam movement through the master and bypass pistons and to the valve after the hydraulic circuit for the same presents a leak or that You lose control of it. In this way, the most extreme portions of a cam profile can still be used to obtain some valve drive after the control over the variable length of the lost motion system is lost and the system has contracted to a minimum length. The foregoing assumes, of course, that the lost motion system is constructed in such a way that it will assume a fully contracted position if control over it were lost and that the valve train will provide the minimum valve drive necessary to operate the motor when the system is totally contracted. The amount of movement that can be "lost" is limited so that part of the cam movement is transmitted to the motor valve. In this way the lost motion system can be designed to allow the motor to operate, although not optimally, so that an operator can still "have a flexible base" and perform repairs. A lost motion system with "flexible phase" capability can alternatively be referred to as a limited lost motion system. Kruger, in U.S. Patent Serial Number 5,451, 029 (September 19, 1995) for a Variable Valve Current Configuration, assigned to Volkswagen AG, describes a lost motion system that when fully contracted can provide some valve drive. However, Kruger does not disclose that the lost motion system may be designed to provide flexible base capacity. Rather, Kruger reports a system of lost motion that starts from a fully contracted position in each engine cycle. Therefore, the lost motion system provides a base level of valve actuation when fully contracted, and this base level can be modified only after the lost motion system has moved a predetermined distance. Therefore it is estimated that Kruger's lost motion system is inconveniently limited to starting from a fully contracted position every motor cycle and can not vary the amount of movement lost until after the lost motion system has been moved by a movement Of cam. Previous lost motion systems have not commonly used high-speed mechanisms to quickly vary the length of the lost motion system. The lost motion systems of the prior art have not been variable so that they can assume more than one length during a single cam projection movement, or even during a motor cycle. When using a high-speed mechanism to vary the length of the lost motion system, more precise control over the actuation of the valve can be achieved, and therefore an optimum valve drive can be achieved for a wide range of engine operating conditions. The lost movement system and method of the present invention can be particularly useful in engines that require valve drive for positive energy and for compression release delay and exhaust gas recirculation events. Commonly, compression release and exhaust gas recirculation events include much less valve stroke than valve events related to positive energy. However, compression release and exhaust gas recirculation events require very high pressures and temperatures to occur in the engine. Therefore, if not controlled, (which can occur with the failure of a lost motion system) the release of compression and recirculation of exhaust gas could cause pressure or temperature damage to an engine at higher operating speeds. . Therefore, it may be beneficial to have a lost motion system that is capable of providing control over positive energy events, compression release, and exhaust gas recirculation, and that will provide only positive energy or some low level of valve events. of compression release and recirculation of exhaust gas, if the lost motion system fails. An example of a lost motion system used to obtain exhaust gas recirculation and retardation is provided by United States Patent No. Serial No. 5, 146,890 to Gobert (September 15, 1992) for a Method and a Device. for Engine Braking a Four-Race Internal Combustion Engine, assigned to AB Volvo, and incorporated herein by reference. Gobert describes a method of conducting exhaust gas recirculation by placing the cylinder in communication with the exhaust system during the first part of the compression stroke and optionally also during the latter part of the entry 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. Additionally, U.S. Patent 5,829,397 (the '397 patent) incorporated by reference herein, discloses a lost movement system and method for precise control of valve drive to optimize valve movement for different operating conditions of the engine, while maintaining an acceptable capacity of acceptable flexible base. Additionally, the '397 patent discloses the use of a high speed lost motion system capable of varying the amount of movement lost during a valve event so that the system independently controls valve opening and closing times, while maintaining a Acceptable capacity of acceptable flexible base. This independent control can be carried out by modifying a valve opening event initiated by standard cam projection with precise amounts of lost motion, which can range from a minimum to a maximum amount at different times during the valve event. In addition, the '397 patent discloses a system for defaulting to a predetermined level of positive-energy valve drive (which may or may not include some exhaust gas recirculation) if control of the lost motion system were lost. The impeller of the present invention can be incorporated into the systems disclosed in the '397 patent. The prior art systems have used damping devices in conjunction with lost motion systems to control the valve seat velocity through temporary restriction of fluid flow. The Patent of the United States of North America Serial Number 5, 485, 813 of Molitor and co-inventors disclose the use of a damping device to reduce the valve seating speed. Molitor and coinvenors reduce the rate of fluid flow change by providing staggered free-flowing ports that close gradually. The Molitor damper and co-winding device is directed only to a lost motion system capable of losing all movement imparted by the cam to the valve. The prior art does not disclose, teach or suggest any method for controlling the engine valve seat speed in conjunction with a lost motion system with flexible base capacity. Commonly, the valve seat velocity control is for the full range of piston stroke derived. The full-range valve seat control does not allow for fine control of motor valve closure since the seat speed is controlled for the entire closing stroke of the valve. Therefore, it is desirable to control the valve seat speed for the limited range just before the valve seat. Therefore, there is a significant need for a system and method for controlling the lost movement that also provides a means to control the seating speed of the motor valve. OBJECTS OF THE INVENTION Therefore, an object of the present invention is to provide a system and method for optimizing the operation of the engine under various operating conditions of the engine by controlling the actuation of the valve.

A further object of the present invention is to provide a system and method for providing precise control of lost motion in a valve train. A further object of the present invention is to provide a system and method for limiting the amount of lost movement provided by a lost motion system. A further object of the present invention is to provide a system and method for controlling the amount of lost movement provided by a lost motion system. A further object of the present invention is to provide a valve actuation system and method that provides a flexible base capacity. A further object of the present invention is to provide a system and method for achieving the variation of the length of a lost motion system. A further object of the present invention is to provide a system and method for selectively actuating a valve with a lost motion system for positive energy operation modes, compression release delay and exhaust gas recirculation. A further object of the present invention is to provide a system and method for valve actuation that is compact and light in weight. A further object of the present invention is to provide an economical integral design that includes a means for limiting the seating speed for motor valves in a lost motion system. A further object of the present invention is to provide a means for controlling the engine valve seat speed in a lost motion system without compromising the fail-safe mechanical nature of the limited lost movement. A further object of the present invention is to provide a full range valve seat speed control for a limited lost motion system. A further object of the present invention is to provide a limited range valve seat speed control for a Limited lost motion system. 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 INVENTION In response to this challenge, the Applicants have developed an innovative and economic system and method to achieve the control of a motor valve that uses lost motion. The present invention may comprise a valve drive system for driving motor valves in an internal combustion engine comprising: a valve train element; a variable length driver for transmitting movement of the valve train member to a motor valve member causing a motor valve to open, wherein the impeller includes an internal variable volume fluid chamber; a fluid control element in hydraulic communication with the impeller to control the length of the variable length impeller through the hydraulic fluid flow control a and the variable volume fluid chamber; and a speed control element that provides a restriction in hydraulic fluid flow of the variable length impeller during the closing stroke of the motor valve thus limiting the seating speed of the motor valve. The variable length impeller may comprise a master piston slidably disposed in a bore of a branch piston or a branch piston slidably positioned in a bore in a master piston so that a fluid chamber of variable volume is formed between the bores. pistons. The master piston can be placed adjacent to the valve train element and the branch piston can be adjacent to the motor valve element. The valve train element may comprise an exhaust cam, or a rotating cam, or a hydraulic articulation. The valve train element may comprise a valve rod or a valve thrust tube. The fluid control element may comprise a trip valve. The trigger valve can be controlled by an electronic controller. The speed control element may be a disk placed in the variable volume chamber of the impeller. The disc may include a central hole to restrict fluid flow. The disc may also include a plurality of holes to restrict fluid flow. The fluid control element may be hydraulically hinged to the variable length impeller and the variable volume chamber through a fluid passage. The fluid control element may be a fluid restriction in the fluid passage. The speed control element may be a bolt placed in the variable volume chamber. The bolt may be deviated in the fluid passage to create a flow restriction. 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. BR EVE DESCR I PC OF THE B UJ OS. Figure 1 is a cross-sectional view of the present invention. Figure 2 is a schematic cross-sectional representation of a combination of another alternative embodiment of the present invention.

Figure 3 is a cross-sectional view of another alternative embodiment of the present invention. Figure 4 is another cross-sectional representation of the embodiment of the present invention shown in Figure 1.

Figure 5 is another cross-section of the embodiment of the present invention shown in Figure 1. Figure 6 is another cross-section of the embodiment of the present invention shown in Figure 1. Figure 7 is a cross-sectional view of another alternative mode of a lost motion impeller limited in accordance with the present invention. Figure 8 is another cross-sectional view of another embodiment of the present invention. Figure 9 is a cross-sectional view of a further alternative embodiment of a limited motion impeller in accordance with the present invention. Figure 10 is a cross-sectional view of another alternative embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION A valve drive system in accordance with the present invention is shown in Figure 1. The valve drive system 10 may include a variable length driver 100 which connects a valve train element. 200 with a motor valve element 300. The variable length driver 100 may comprise any means for transmitting a force between the valve train member 200 and the valve 300, which may be varied between plural operating lengths. Preferably, the variable length driver 100 may be limited to a minimum operating length that allows some minimum force to be transmitted between the valve train member 200 and the valve 300. The valve train member 200 may take a number of different forms, such as a mechanical joint, a hydraulic circuit, a hydro-mechanical joint, and / or an electro-mechanical joint. The movement can be imparted to the valve train element 200 by a vehicle or motor component from which a force can be derived, or even from which a signal can be derived to control the actuation of a stored force. In the preferred embodiment a rotating cam is provided, however, the invention does not have to be limited to a cam-driven design to be operative. The motor valve element 300 includes cylinder inlet and exhaust valves. The variable length driver 100 may transmit motion to a motor valve stem directly, or through an exhaust cam to a plurality of motor valves 300. Continuing with reference to FIG. 1, the variable length driver 100 may comprise a branch piston 104 slidably positioned in a master piston 102. The master piston 102 and the branch piston 104 may have any complementary transverse shape, such as coaxial, concentric cylinders or ellipses, while the master piston is slidable in the branch piston. so that a sealed chamber 106 of variable volume can be formed can be formed by the pistons. It should be noted that the hydraulic ratio of the master piston 102 and the branch piston 104 may vary in accordance with the parameters of the engine in which the system is to be used. To obtain various hydraulic ratios, the configuration and relative sizes of the master and branch pistons can vary widely. The variable length driver 100 disclosed in Figure 1 comprises a guide housing 600 that is positioned between the motor valve element 300 and the valve train member 200. The guide housing 600 may be an integral portion of a block or head of motor and the variable length driver 100 may be slidably positioned directly on the head or engine block. The housing 600 includes the fluid inlet and outlet passage 1 1 1. The passage 11 1 connects the variable length driver 100 to a Trigger valve (not shown). The trigger valve may be positioned to vent the passage 1 1 1 and the impeller 100 to either a storage accumulator or collector. Contents within the housing 600 are the external master piston 102 and the internal branch piston 104. The master piston 102 makes contact with the valve train member 200 and the branch piston 104 makes contact with the motor valve element 300. Trigger valve can be controlled by a control system. The control system not shown may comprise any electronically or mechanically driven means for selecting the length of the variable length driver 100. The control system may include a microprocessor, articulated with other motor components, to determine and select the appropriate length of the variable length driver 100. The valve drive can be optimized to a plurality of motor speeds by controlling the length of the variable length driver 100 based on the information collected in the microprocessor of the engine components. The control system may be connected to and / or in communication with the trip valve by any of numerous communication schemes, including but not limited to, a wired electrical connection, a hydraulic connection, a mechanical connection, a wireless radio connection, and / or any combination of the foregoing. Preferably, the control system and the trigger valve may comprise a "high speed" device capable of varying the length of the variable length driver 100, one or more times per engine cycle in which the drive system of the variable speed motor is installed. valve 10. Using the control system, the valve actuation system 10 can be controlled by selectively varying the length of the variable length system 100 to vary the amount of force and / or displacement that is transmitted from the valve train member 200 to the Motor valve element 300. In this way, the valve drive system can optimize the operation of the motor under various operating conditions of the motor, provide precise control of the motion lost by the variable length driver 100, provide flexible base capacity acceptable and / or provide high-speed variation of variable length 100 length impeller length. E The master piston 102 includes passages to allow the filling of the hydraulic chamber 106 formed between the two pistons. A disc restricting the flow 120 is positioned between the two pistons so that, when the disc 120 is against the master piston 102, the flow of oil out of the impeller 100 is restricted by a central hole 121 in the disc 120. When the disc 120 is against the branch piston 104, the oil can freely flow in the cavity 106 between the two pistons. A spring 1 18 deflects the disk 120 towards the master piston 102. The operation of the impeller 100 is shown in Figures 4-6. When the chamber 106 is at a pressure less than that required to overcome the deviation of the spring from the engine valve, there is no hydraulic articulation between the master piston 102 and the branch piston 104. However, the master piston 102 still couples in a the driven piston 104 to provide some valve opening force (i.e., no displacement) of the valve train member 200 to the valve member 300. To transmit a greater valve opening force to the valve member 300 and to establish a complete hydraulic joint between the master piston 102 and the branch piston 104, hydraulic fluid is provided to the impeller 100. Hydraulic fluid can be provided to the impeller 100 of a source of engine lubricant (not shown) through the passage 1 1 1 to the chamber 106. As shown in Figure 4, the incoming fluid flows into the branch piston 104, and pushes down the pressure disc. role of the valve seat 120. The free flow of oil is achieved through the central hole 121 and the side holes 122 of the disk 120. The fluid fills the branch piston 104 without restriction, taking the complete clearance between the master piston 102 and the Derived piston 104. Once the chamber 106 is full and fluid flow is stopped, as shown in Figure 5, the valve seat control disc 120 is biased upwards by the spring 1 18. The valve firing closes and stops the flow of fluid in or out of the impeller 100. The complete movement of the valve train element 200 is imparted to the motor valve element 300, without lost movement. The master piston 102 and the branch piston 104 move together as a solid articulation. When you want lost movement, the trigger valve opens to vent the chamber 106. The impeller 100 begins to collapse at a rate proportional to the speed at which the fluid escapes from the branch piston 104. The branch piston 104 moves toward the master piston 102 at a speed controlled since the oil flow is limited by the size of the central hole 121 in the disk 120. The speed of the motor valve element 300 and the motor valve to its seat is also limited. Should valve seat occur while the impeller 100 is collapsing, the speed at which the valve impacts the seat is limited by the flow of oil through the orifice disk 120. The disk 120 restricts the flow of fluid out of the impeller 100. As shown in Figure 6, the seat velocity of the valve is limited through the full range of the stroke of the branch piston 104. Therefore, the mode shown in Figure 1 can be referred to as a control system. of full-range valve seat speed. In an alternative embodiment, shown in Figure 2, the impeller 100 is positioned between the engine valve 300 and the motor valve drive source 200. Contained in the impeller 100 is a pair of concentric pistons having a master piston. external 102 and an internally derived piston 104. The oil is supplied to the impeller 100 by a dedicated passage 618 with a high-pressure check valve 617. The passage 618 has very little flow restriction. A trigger valve 410 can also be provided. For example, the trip valve 410 may be similar to the trip valves disclosed in U.S. Patent Serial Number 5,460,329 to Sturman (issued October 24, 1995), for a High Speed Fuel Injector; and / or U.S. Patent Serial Number 5,479,901 to Gibson (issued January 2, 1996) for an Electro-Hydraulic Reel Control Valve Assembly Adapted for a Fuel Injector. When the shut-off valve 410 is opened, the fluid between the pistons escapes, and the impeller 100 begins to collapse. When the impeller 100 collapses, the oil must flow through a separate passage 615 equipped with a specific orifice 616 to control the flow velocity. Similar to the embodiment shown in Figure 1, the impeller 100 in Figure 2 provides full-range limited valve seat. The trigger valve 410 can simultaneously lock and unlock the hydraulic passage 615 going to the impeller 100 and a second passage going to a second impeller (not shown). In this way, a trigger valve can control the operation of two (or more impellers). In alternative embodiments, the trip valve 410 does not have to be a solenoid operated trip valve, but instead could be operated hydraulically or mechanically. However, regardless of the manner in which it is implemented, the trigger valve 410 is preferably capable of providing one or more opening and closing movements per engine cycle and / or one or more opening and closing movements during a valve event. individual. If there were a fault in the system that would prevent the variable length driver 100 from receiving hydraulic fluid, the default valve drive system would go to a maximum lost movement value that causes a minimum valve opening amount. The maximum amount of lost motion may be predetermined to provide a degree of valve actuation necessary for the positive energy operation of the engine, and little or no compression release delay valve or exhaust gas recirculation valve actuation. Therefore, the maximum amount of motion lost would allow the engine to produce some positive energy level and possibly some levels of compression release delay and / or exhaust gas recirculation even with a failure of the valve actuation control system or a variable length driver fault. If the valve drive system were not by default at a maximum lost movement value, extreme temperatures and pressures in the engine could develop due to uncontrolled compression release delay and / or exhaust gas recirculation at engine speeds. greater if the impeller was left expanded, or no motor function could be obtained if the impeller did not "solidify". System 1 0 of Figure 2 may also include an accumulator 620 and an oil supply source 630. The hydraulic fluid supply may comprise motor oil used for other engine functions, such as crankcase lubrication. In addition to the two modes described above, an integral limiter can be made by substituting any combination of verification and restriction device internally to the concentric pistons to achieve the same result (such as a small orifice and a ball check valve). . Figure 3 discloses a limited lost motion impeller 100. The impeller 1 00 comprises an external master piston 1 02, an internal bypass piston 104, and an optional bypass spring 125. The bypass spring 125 serves to deflect the piston derivative 1 04 to the master piston 1 02 when the fluid chamber between the pistons is vented. The master piston 1 02 includes a downward projecting extension 122. The design of the impeller of Figure 4 provides valve seat velocity current of limited range. The valve seat velocity is limited only when the branch piston 104 collapses to the point that the upper part of the branch piston 1 04 is flush with the bottom of the extension of the master piston 122. As the branch piston 104 continues to move towards above the extension 122 the escaping fluid must follow a tortuous flow path between the collapsing master piston 102 and the branch piston 104 through a passage 123. The clearance between the master and derivative pistons and, therefore, the passage size 123, can be adjusted to control the valve seat velocity. Reducing the free space causes the speed of the fluid to escape and, as a result, the valve seat velocity decreases. The length of the extension 122 can also be adjusted to control the valve seat velocity control range. The seat velocity of the valve is limited to the limited range shown by distance D i. Figure 7 discloses another mode of the limited lost motion impeller 100. The impeller 100 is comprised of an internal master piston 102 and an external branch piston 104. The impeller additionally includes a speed disk 124 and a speed disk shell 126. The housing includes a fluid delivery passage 653. The passage 653 is derived in a fluid passageway 654 that carries fluid to the top of the velocity disc 124, and a lower fluid passageway 655 that carries fluid to the chamber. 106 between the pistons. The housing 600 additionally includes a restricted passage 627 that connects to an area above the speed disc 124 with the passageway 654. As shown in Figure 7, grooving the master piston 102 may be preferred because it can prevent the feeding passages and Drain, communicating with the sealed chamber, is occluded when the master piston tapers the branch piston 104. When lost motion is desired, the passage 653 which connects the impeller 100 to the trip valve is vented. Therefore, passages 654 and 655 are also ventilated allowing the branch piston 104 to rise freely because the spring deflects the motor valve 300. The branch piston 104 will continue to rise freely until it contacts the velocity disc 124 The branch piston 104 forces the speed disk 124 upwards to the speed disk shell 126. The volume of oil above the speed disk 124 escapes through the restricted passage 627. The restricted area of the passage 627 limits the speed to which the branch piston 104 can be increased and, as a result, the valve seat velocity. The valve seat velocity is limited for the period when the branch piston 104 makes contact with the velocity disk 124 until the valve 300 settles. The external branch piston 104 is connected to the motor valve 300 and, as a result, it is known exactly when the valve settling will occur. Therefore, the speed disk 124 can be set to operate only for a short distance just before valve seating. Figure 8 discloses another mode of a limited lost motion impeller 100. The impeller 100 includes the design elements of the impeller 100 shown in Figure 7, but also additionally includes a clearance adjustment means 107. The adjustment means of clearance 107, commonly, a lock nut, can be adjusted for variations in cylinder-to-cylinder engine valve clearance. The gap adjusting means 107 adjusts the position of the velocity disc shell 126. A further embodiment of the present invention is described in Figure 9. The impeller 100 shown in Figure 21 provides range valve seat velocity control. limited. The impeller 100 includes an internal master piston 102 and an external branch piston 104. The branch piston 104 includes an outer ring 129. A housing 600 is provided and includes a passage 653 that connects the impeller 100 to a trip valve and accumulator; a ball check valve 656; a filling passage 657; and a restricted area 658. When lost motion is desired, the trip valve is positioned to vent passage 653. As a result, chamber 106 is also vented and the impeller begins to collapse freely. The branch piston 104 moves up towards the master piston 102. The branch piston 104 moves up freely until the ring 129 loses communication with the passage 653. After the passage 653 is blocked, all the return fluid must flow through the restricted area 658. The flow rate of the escaping fluid is reduced and, as a result, the flow velocity of the upward movement of the diverted piston and the velocity of the valve member 300 towards the valve seat is also reduced. Impeller 100 provides limited range valve seat velocity current for the range in which passage 653 is blocked by branch piston 104, and fluid must escape through restricted passage 658. This range is indicated by the letter D2. The seat velocity of the valve is controlled by adjusting the size of the restricted area 658. When it is desired to re-establish the complete hydraulic joint between the master piston 102 and the branch piston 104, high pressure fluid is introduced into the passage 653. The fluid moves through passage 657 and dislodges ball check valve 656. Fluid flows into chamber 106 and re-establishes the joint between the two pistons. Figure 10 discloses a further embodiment of the present invention, Figure 10 discloses a housing 600 and an impeller 100 comprised of an internal master piston 102 and an external branch piston 104. Placed between the pistons in the chamber 106 is a bolt of flow restriction 140. Flow restriction bolt 140 includes flow restriction bolt disk 141. Flow restriction bolt 140 is deflected downwardly by flow restriction spring 144, creating a restricted area 164. area 164 is between the bottom of the flow restriction bolt disk 141 and the horizontal surface 165 of the branch piston 104. During the filling of the chamber 106, the force of the incoming fluid forces the disk 141 and the bolt 140 upwards allowing the free flow of fluid in the chamber 106. Once the chamber 106 is full and fluid is stopped, the spring 144 deflects the flow restriction bolt 140 and the disk 1 41 down. When the lost movement starts, passage 653 is ventilated. Due to the ventilation of the passageway 653, the chamber 106 vents through the area 164 and the passageway 162. The speed at which the fluid from the chamber 106 can escape is limited by the restricted area 164. The seat velocity of the valve it is a function of the speed at which the fluid escapes from the chamber 106 and, as a result, the seat velocity of the valve is correspondingly limited. Figure 10 describes an impeller with full-range valve seat speed control. As the impeller 100 collapses, the speed at which the fluid escapes the impeller is controlled over the full range of the piston movement. It will be apparent to those skilled in the art that various modifications and variations may be made in the construction, configuration, and / or operation of the present invention without departing from the scope or spirit of the invention. For example, in the aforementioned embodiments, various changes can be made to the design of the impeller without departing from the scope and spirit of the invention. Additionally, it may be appropriate to make additional changes or modifications to the master and derivative pistons without departing from the scope of the invention. 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 (19)

1. CLAIMS 1. A valve drive system for driving engine valves in an internal combustion engine comprising: a valve train element, wherein said valve train element comprises one of an exhaust cam, a rotating cam, a joint hydraulic, a thrust tube and a cam follower; a variable length driver for transmitting movement of the valve train element to a motor valve element causing a motor valve to open, wherein said driver includes a fluid chamber of internal variable volume; a fluid control element in hydraulic communication with the impeller for controlling the length of said variable length impeller through the control of the hydraulic fluid flow to and said variable volume fluid chamber; and a speed control element that provides a restriction in the hydraulic fluid flow of said variable length impeller during the closing stroke of the motor valve thus limiting the seating speed of the motor valve. The system of claim 1, wherein said variable length impeller comprises a master piston slidably positioned in a bore of a branch piston so that said fluid volume chamber of variable volume is formed between said pistons. The system of claim 1, wherein said variable length impeller comprises a bypass piston slidably disposed in a bore of a master piston so that said variable volume fluid chamber is formed between said pistons. The system of claim 2, wherein said master piston is adjacent to the valve train member and said branch piston is adjacent to said motor valve member. The system of claim 1, wherein said motor valve element comprises a valve rod. The system of claim 1, wherein said motor valve element comprises a valve thrust tube. The system of claim 1, wherein said motor valve element comprises a bridge. The system of claim 1, wherein said motor valve element comprises an exhaust cam. The system of claim 1, wherein said motor valve element comprises a valve rod. The system of claim 1, wherein said fluid control element comprises a trip valve. The system of claim 10, further comprising an electronic controller operatively connected to said trigger valve. The system of claim 1, wherein said speed control element is a disk placed in said variable volume chamber. The system of claim 12, wherein said disc includes a central hole for restricting fluid flow. The system of claim 13, wherein said disc includes a plurality of holes for restricting fluid flow. 15. The system of claim 1, wherein said fluid control element is hydraulically hinged to said variable length driver and said variable volume chamber through a fluid passage. 16. The system of claim 15, wherein said speed control element is a flow restriction in said fluid passage. The system of claim 1, wherein said speed control element is a bolt placed in said variable volume chamber. The system of claim 17, wherein said branch piston includes a fluid passage that hydraulically articulates said variable volume chamber to said fluid control element. The system of claim 18, wherein said pin is biased in said fluid passage so that a flow restriction is created.