Patent Publication Number: US-6334429-B1

Title: Integrated lost motion rocker brake with control valve for lost motion clip/reset

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application relates to and claims priority on U. S. Provisional Applications Ser. No. 60/154,474, entitled “CHECK/SHUTTLE VALVE (CONTROL VALVE) FOR AN INTEGRATED LOST MOTION ROCKER BRAKE,” filed on Sep. 17, 1999 and Ser. No. 60/172,138, entitled “VALVE FOR LOST MOTION CLIP/RESET LOCATED IN THE ROCKER SHAFT,” filed on Dec. 17, 1999. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to the control of exhaust and intake valves during positive power and engine braking. In particular, the present invention is directed to a control valve that combines a check valve and a shuttle valve for use in a lost motion engine brake system. The present invention is also directed to a system and method to allow the clipping or resetting of a lost motion engine brake system. 
     BACKGROUND OF THE INVENTION 
     For many internal combustion engine applications, such as for powering heavy trucks, it is desirable to operate the engine in a braking mode. This approach involves converting the engine into a compressor by cutting off the fuel flow and opening the exhaust valve for each cylinder near the end of the compression stroke. 
     An early technique for accomplishing the braking effect is disclosed in U.S. Pat. No. 3,220,392 to Cummins, wherein a slave hydraulic piston located over an exhaust valve opens the exhaust valve near the end of the compression stroke of an engine piston with which the exhaust valve is associated. To place the engine into braking mode, the three-way solenoids are energized, which causes pressurized lubricating oil to flow through a control valve, creating a hydraulic link between a master piston and a slave piston. The master piston is displaced inward by an engine element (such as a fuel injector actuating mechanism) periodically in timed relationship with the compression stroke of the engine which in turn actuates a slave piston through hydraulic force to open the exhaust valves. The compression brake system as originally disclosed in the &#39;392 patent has evolved in many aspects, including improvements on the control valves (see, for example, U.S. Pat. No. 5,386,809 to Reedy et al.; see also U.S. Pat. No. 4,996,957 to Meistrick, which is assigned to the assignee of the present application and incorporated herein by reference.) Improvements have also been made in the piston actuation assembly (see U.S. Pat. No. 4,475,500 to Bostelman). In a typical modem compression braking system, the exhaust valves are normally operated during the engine&#39;s power mode by an exhaust rocker lever. To operate the engine in a braking mode, a control valve separates the braking system into a high pressure circuit and a low pressure circuit using a check valve which prevents flow of high pressure fluid back into the low pressure supply circuit, thereby allowing the formation of a hydraulic link in the high pressure circuit. 
     Various problems are known in conventional compression braking system. First, a time delay may occur between the actuation of the three-way solenoid valve and the onset of the braking mode. This time delay is due in part to the positioning of the solenoid valve a spaced distance from the control valve, which creates longer than ideal fluid passages and thus delayed response time. The high pressure circuit may also comprise long fluid passages between the master and slave pistons, which disadvantageously increase the compressed fluid volume and thus the response time. 
     In addition, in conventional compression braking systems, the braking system is a bolt-on accessory that fits above the overhead. In such systems, in order to provide space for mounting the braking system, a spacer is positioned between the cylinder head and the valve cover. The valve cover is bolted to the spacer, which adds unnecessary height, weight, and costs to the engine. Many of the above-noted problems result from viewing the braking system as an accessory to the engine rather than as part of the engine itself. 
     One possible solution is to integrate components of the braking system with the rest of the engine components. One attempt at integrating parts of the compression braking system is found in U.S. Pat. No. 3,367,312 to Jonsson, which discloses an engine braking system including a rocker arm having a plunger, or slave piston, positioned in a cylinder integrally formed in one end of the rocker arm. The plunger may be locked in an outer position by hydraulic pressure in order to permit braking system operation. Jonsson also discloses a spring for biasing the plunger outward from the cylinder into continuous contact with the exhaust valve to permit the cam-actuated rocker lever to operate the exhaust valve in both the power and braking modes. 
     In addition, a control valve is used to control the flow of pressurized fluid to the rocker arm cylinder so as to permit selective switching between braking operation and normal power operation. The control valve unit is positioned separately from the rocker arm assembly, however, which results in unnecessarily long fluid delivery passages and therefore a longer response time. This may also lead to an unnecessarily large amount of oil that must be compressed before activation of the braking system can occur, resulting in less control over the timing of the compression braking. 
     Jonsson also discloses using the control valve to control the flow of fluid to a predetermined set of cylinders in the engine, thereby undesirably preventing individual engine cylinders or different groups of engine cylinders from being selectively operated in the braking mode. 
     Furthermore, the control valve as disclosed by Jonsson is a manually-operated, rotary type valve requiring actuation by the driver. Manual operation often results in unreliable and inefficient braking operation. Also, rotary valves are subject to undesirable fluid leakage between the rotary valve member and its associated cylindrical bore. 
     Other designs known in the art include U.S. Pat. No. 3,332,405 to Haviland, assigned to the assignee of the present application and incorporated herein by reference. Haviland discloses a compression braking system with a control valve unit for enabling the formation of a hydraulic link. The control valve unit is mounted in a cavity formed in a rocker arm that operates the exhaust valves during the braking mode. Separate cam lobes are used for normal power operation and braking operation. However, a single rocker arm is used to actuate the exhaust valves during both normal and braking modes. A drawback in this design is that the braking cam lobe profile design, and therefore the braking system operation, may be at least partially dependent on, or influenced by, the design of the cam lobe used for operating the exhaust valve during normal engine operation. 
     Another known design is disclosed in U.S. Pat. No. 4,251,051 to Quenneville, assigned to the assignee of the present application and incorporated herein by reference. Quenneville discloses a solenoid valve assembly with an inlet communicating with a supply of fluid, and one or more outlet passages communicating with respective loads requiring intermittent fluid supply and a drain passage. A respective ball valve is positioned between the inlet and each outlet and is spring-biased to block flow between the supply and outlet passage while opening the drain passage. An armature and pin are actuated to move the ball valve so as to connect the supply to the outlet and close the drain passage. However, while the valve assembly in the actuated position permits supply flow to the outlet passage, it does not prevent the return flow of fluid from the outlet passage into the supply passage and therefore does not permit the formation of a hydraulic link between different pressurized circuits as required by a control valve during compression braking system operation. 
     Designs in the known art have required independent check and shuttle valves in order to control a lost motion integrated rocker brake. Accordingly, there is a need for a simplified rocker brake control valve assembly. The design of the present invention integrates the check and shuttle valves into a single unit. This single unit serves to control the flow of oil within the integrated lost motion rocker brake. In addition, there have been many attempts to design systems to clip or reset lost motion circuits. The present invention also provides a system and method to allow the clipping or resetting of a lost motion engine brake system. 
     The present invention meets these needs and provides other benefits as well. 
     OBJECT OF THE INVENTION 
     It is therefore an object of the present invention to provide an economical control valve for an integrated lost motion rocker brake. 
     It is another object of the present invention to provide a simplified means of controlling the flow of hydraulic fluid in an integrated lost motion rocker brake. 
     It is still another object of the present invention to provide an improved means of switching an engine brake between positive power and braking. 
     It is yet another object of the present invention to provide control of an integrated lost motion rocker brake without using an independent check valve and shuttle valve. 
     It is a further object of the present invention to provide an integrated lost motion rocker brake with a single valve having the same function as a known check valve and shuttle valve. 
     It is still a further object of the present invention to provide a control valve with a shuttle valve that indexes to direct the flow of hydraulic fluid in an integrated lost motion rocker brake. 
     It is yet a further object of the present invention to provide a control valve that permits a constant directional (checked) flow of hydraulic fluid for automatic lash adjustment in an integrated lost motion rocker brake. 
     It is another object of the present invention to provide an integrated lost motion rocker brake with a control valve that allows check hydraulic fluid to fill behind the accumulator, thereby preventing the accumulator from indexing. 
     It is still another object of the present invention to provide a control valve for clipping or resetting an engine valve in a lost motion system. 
     It is yet another object of the present invention to provide means of clipping or resetting an engine valve in a lost motion system and thereby to prevent the need for piston pockets. 
     It is another object of the present invention to provide an indexed or rotated valve located in the rocker arm or shaft of an integrated lost motion rocker brake. 
     Additional objects and advantages of the invention are set forth, in part, in the description which 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 
     In response to the foregoing challenge, Applicant has developed an innovative and economical design for a single control valve for a lost motion integrated rocker brake. As illustrated in the accompanying drawings and disclosed in the accompanying claims, the invention is a braking system for an internal combustion engine having an engine valve selectively openable in response to movement of a rotary cam about a cam shaft and a rocker assembly cooperative therewith, and having a control valve hydraulically connected to an engine valve assembly and thereby to the engine valve, wherein the engine is operable in either a power mode or a braking mode, having an improvement comprising means for checking hydraulic fluid to provide constant directional flow of hydraulic fluid for automatic lash adjustment of a valve actuating piston having an upper end and a lower end; and means for controlling a supply of hydraulic fluid in order to provide actuation of the engine valve by the piston. 
     In an embodiment of the braking system of the present invention, the engine valve assembly may further comprise an accumulator slidably disposed in an accumulator bore in the upper end of the piston, the accumulator being biased upward by an accumulator spring, having a swivel foot disposed on a valve stem of the engine valve, and wherein the lower end of the piston is in contact with the swivel foot. The braking system of the present invention may combine the hydraulic fluid checking means and the controlling means together in the control valve. 
     The control valve may further comprise a control valve body having an upper end and a lower end and being slidably disposed in a control valve bore in the rocker arm and biased upward by a control valve spring, an inner body having a ball seat formed therein, and a check ball disposed in the inner body and biased upward by a check spring. 
     The control valve body may further comprise an upper annulus located toward the upper end of the control valve body, a lower annulus located toward the lower end of the control valve body, a middle annulus located around the control valve body between the upper annulus and the lower annulus, a first horizontal bore which diametrically spans the control valve body, having each end of the first horizontal bore opening within the upper annulus, and a second horizontal bore, which diametrically spans the control valve body, having each end of the second horizontal bore opening within the middle annulus, and wherein a first vertical bore and a second vertical bore are axially disposed in the inner body about a longitudinal axis. 
     In the braking system of the present invention, the check ball may be disposed in the second vertical bore, and the first vertical bore may connect the first horizontal bore with the second horizontal bore to provide hydraulic communication from the upper annulus, through the control valve body, to the middle annulus. 
     The braking system may further comprise a hydraulic system having a switched low pressure supply circuit and a constant low pressure supply circuit connected to the hydraulic fluid supply and to the control valve, and a lashless fluid supply circuit and an accumulator control circuit connecting the control valve to the engine valve assembly. Upon activation of a solenoid switch in braking mode, the control valve may index in the control valve bore, aligning the middle annulus with the lashless fluid supply circuit and the accumulator control circuit so that the lashless fluid supply circuit and the accumulator control circuit become hydraulically locked and the motion of the cam is translated directly into the motion of the engine valve. 
     In the braking system of the present invention, the hydraulic fluid controlling means may further comprise an accumulator control circuit and a switched low pressure supply circuit for providing clipping of the valve actuating piston and thereby provide lost motion braking. The braking system may further comprise a clipping/reset spool disposed in the cam shaft, and the clipping/reset spool may further comprise a plurality of clipping annuluses described therearound. 
     In the braking system of the present invention, the plurality of clipping annuluses may each form a reduced diameter about only a portion of the clipping/reset spool, such that when the reduced diameter portion is aligned with a clip passageway and thereby with the accumulator control circuit, hydraulic fluid dumps into the supply of hydraulic fluid, and when a full outer diameter portion of the clipping/reset spool is aligned with the clip passageway and thereby with the accumulator control circuit, the accumulator control circuit is closed and hydraulically locked, and the rocker assembly follows a braking bump on the cam. 
     In addition, Applicant has developed an innovative and economical design for clipping or resetting of a lost motion engine brake system. As embodied herein, the invention is a braking system for an internal combustion engine having an engine valve selectively openable in response to movement of a rotary cam about a cam shaft and a rocker assembly cooperative therewith, and having a control valve hydraulically connected to an engine valve assembly and thereby to the engine valve, wherein the engine is operable in either a power mode or a braking mode, and the improvement comprising a clipping/reset spool disposed in the cam shaft and connected to an accumulator control circuit, wherein movement of the clipping/reset spool provides clipping of a valve actuating piston and thereby lost motion braking, and wherein the clipping/reset spool further comprises a plurality of clipping annuluses described therearound, the plurality of clipping annuluses each forming a reduced diameter about only a portion of the clipping/reset spool, such that when the reduced diameter portion is aligned with a clip passageway and thereby with the accumulator control circuit, hydraulic fluid dumps into the supply of hydraulic fluid, and when a full outer diameter portion of the clipping/reset spool is aligned with the clip passageway and thereby with the accumulator control circuit, the accumulator control circuit is closed and hydraulically locked, and the rocker assembly follows a braking bump on the cam. 
     In the clipping/reset braking system, the accumulator control circuit may further comprise a check valve biased by a check valve spring, wherein the check valve checks a supply of hydraulic fluid in the accumulator control circuit. 
     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. The accompanying drawings, which are incorporated herein by reference, and which constitute 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 
     The invention will now be described in conjunction with the following drawings in which like reference numerals designate like elements and wherein: 
     FIG. 1 depicts a cross section in elevation of a rocker brake valve actuation assembly according to the present invention. 
     FIG. 2 depicts a cross section in elevation of a control valve for a rocker brake valve actuation assembly during positive power operation according to the present invention. 
     FIG. 3 depicts a cross section in elevation of control valve for a rocker brake valve actuation assembly during braking operation according to the present invention. 
     FIG. 4 a  depicts a cross section in elevation of a rocker brake valve actuation assembly according to the present invention during Stage  1  of positive power operation. 
     FIG. 4 b  depicts a cross section in elevation of a rocker brake valve actuation assembly according to the present invention during Stage  2  of positive power operation. 
     FIG. 5 depicts a cross section in elevation of a rocker brake valve actuation assembly according to the present invention during braking operation. 
     FIG. 6 a  depicts a cross section in elevation of a rotationally driven, ported rocker arm and valve system for clipping/reset of a lost motion circuit according to an alternate embodiment of the present invention. 
     FIG. 6 b  depicts a cross section in elevation of the rotationally driven, ported rocker arm and valve system for clipping/reset of a lost motion circuit of FIG. 6 a , rotated 90° about a vertical axis. 
     FIG. 7 depicts a cross section in elevation of a linear-activated, ported rocker arm and valve system according to an alternate embodiment of the present invention. 
     FIG. 8 depicts a cross section in elevation of a miniature axial flow check valve according to an alternate embodiment of the present invention. 
     FIG. 9 depicts a cross section in elevation of a miniature radial flow check valve according to an alternate embodiment of the present invention. 
     FIG. 10 depicts a cross section in elevation of a miniature radial flow check valve according to an alternate embodiment of the present invention utilizing a different assembly technique. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. 
     A rocker brake valve actuation assembly according to the present invention is shown in FIG. 1 as  1 . Valve actuation assembly  1  comprises control value  20  according to the present invention and engine valve assembly  10  from the known art. Control value  20  is housed in rocker arm  400  (not shown) and is hydraulically connected to engine valve assembly  10 . 
     As shown in FIG. 1, known engine valve assembly  10  comprises engine valve  100 , which further comprises upper portion or engine valve stem  105 , engine valve spring  110 , spring retainer  115 , and swivel foot  120 . Engine valve spring  110  is held in place by spring retainer  115  which biases engine valve  100  upwards, that is, in a closed position. Engine valve assembly  10  further comprises piston bore  106 , which is disposed in rocker arm  400  (not shown) and piston  130 , which is slidably disposed in piston bore  106 . Piston  130  further comprises lower end  131  and upper end  132 , and is held in place in piston bore  106  during assembly by piston retaining ring  133 . Lower end  131  of piston  130  is shaped to seat in swivel foot  120 . Top end face  134  forms the top surface of upper end  132  of piston  130 . 
     Engine valve assembly  10  further comprises accumulator  140 , which is slidably disposed within accumulator bore  141  in upper end  132  of piston  130 , and accumulator spring  145 , which biases accumulator  140  toward washer  146 . Washer  146  is held in place by accumulator retaining ring  147 . Washer  146 , accumulator retaining ring  147 , accumulator  140 , and accumulator bore  141  together proscribe the indexing distance of accumulator  140 . 
     As embodied herein, control value  20  is hydraulically connected to piston bore  106 . Control valve bore  204  is preferably disposed in rocker arm  400  (not shown). Control valve  20  comprises control valve body  200 , which has an upper end  201  and a lower end  202 . Control valve body  200  is slidably disposed in control valve bore  204  about longitudinal axis  203  and indexes to direct the flow of hydraulic fluid in the system. Control valve body  200  limits the travel of control value  20  by aligning flow paths for the hydraulic fluid, and thereby provides the lower stop for control value  20 . 
     Continuing with reference to FIG. 1, control valve body  200  further comprises inner body  210 . Inner body  210  is secured within control valve body  200  by ductile locking ring  220 . Inner body  210  further comprises ball seat  211 . Check ball  230  is disposed in inner body  210  and is biased upward into ball seat  211  by check spring  235 . Check ball  230  provides the hydraulic fluid checking function. Inner body  210  routs the flow of a constant hydraulic fluid supply to check ball  230 , and provides an upper stop that allows indexing hydraulic fluid to apply pressure to the top surface of control valve body  200 . 
     According to the present invention, control valve body  200  further comprises control valve spring  240 , which biases control valve body  200  upward, and ductile lock washer  250 , which locks control valve body  200  in control valve bore  204 . Control valve spring  240  prevents movement of control value  20  unless adequate hydraulic fluid pressure is provided at the top of control valve body  200 . After the indexing hydraulic fluid supply is turned off, control valve spring  240  returns control valve body  200  to its initial, biased upward position. Ductile lock washer  250  provides a simple means to lock the assembly of control valve body  200  in control valve bore  204 , and provides a solid stop to limit the travel of control valve body  200  . Ductile lock washer  250  further comprises washer bore  251 , through which hydraulic fluid may flow to atmosphere. 
     Continuing with reference to control value  20 , control valve body  200  further comprises three annuluses having a diameter less than that of control valve body  200 : upper annulus  260  which is located toward upper end  201 , lower annulus  262  which is located toward lower end  202 , and middle annulus  261  therebetween. Control valve body  200  further comprises first horizontal bore  270 , which diametrically spans control valve body  200 , having each end of first horizontal bore  270  opening within upper annulus  260 , and second horizontal bore  271 , which diametrically spans control valve body  200 , having each end of second horizontal bore  271  opening within middle annulus  261 . First vertical bore  280  and second vertical bore  281  are axially disposed in inner body  210  about longitudinal axis  203 . As embodied herein, first vertical bore  280  communicates with first horizontal bore  270  and second horizontal bore  271  to provide communication between upper annulus  260  and middle annulus  261 . Second vertical bore  281  houses check spring  235 . 
     Valve actuation assembly  1  further comprises of four hydraulic circuits. Two circuits, collectively  300 , enter control value  20 : switched low pressure supply circuit  320 , which preferably contains hydraulic fluid at about 50 psi, and constant low pressure supply circuit  330 , which also preferably contains hydraulic fluid at about 50 psi. Switched low-pressure supply circuit  320  connects the hydraulic fluid supply to control valve bore  204  at control valve body upper end  201 . Constant low pressure supply circuit  330  connects the hydraulic fluid supply through upper annulus  260  and first horizontal bore  270  into inner body  210 , past check ball  230  and through middle annulus  261  into lashless fluid supply circuit  340 . 
     As embodied herein, two additional hydraulic circuits, collectively  310 , exit control value  20 : lashless fluid supply circuit  340  and accumulator control circuit  350 . Lashless fluid supply circuit  340  connects piston bore  106  at piston upper end  132  to control valve bore  204  above accumulator control circuit  350 . Lashless fluid supply circuit  340  biases piston  130  down so that it is always in contact with swivel foot  120 , providing lashless operation. Accumulator control circuit  350  connects control valve body lower end  202  to accumulator  140 . 
     As contemplated by the present invention, control value  20  provides an efficient means to switch between positive power and braking in an integrated lost motion rocker brake. Control value  20  is preferably located within a rocker arm or shaft, however, the system of the present invention could also be contained in any device where a lost motion system is needed. 
     Referring now to FIG. 2, control value  20  is shown during positive power mode of engine operation. The rocker brake valve actuation assembly  1  of FIG. 1 operates as follows: a solenoid switch (not shown) is off. Low pressure hydraulic fluid is present in hydraulic circuit  300 , in both switched low pressure supply circuit  320  and constant low pressure supply circuit  330 . Control value  20  is biased upward by control valve spring  240  because the low pressure hydraulic fluid from switched low pressure supply circuit  320  transmits less force than that from control valve spring  240 . With control value  20  in this position, upper annulus  260  is aligned with constant low pressure supply circuit  330 , middle annulus  261  is aligned with lashless fluid supply circuit  340 , and lower annulus  262  is aligned with accumulator supply circuit  350 . Lower annulus  262  vents to the main hydraulic fluid supply. 
     As a result, low pressure hydraulic fluid forms a continuous circuit from constant low pressure supply circuit  330  to the lashless fluid supply circuit  340 . The flow path is as follows: from the switched low pressure supply circuit  320 , through first horizontal bore  270 , first vertical bore  280  in inner body  210 , past check ball  230 , through second horizontal bore  271 , through middle annulus  261  and into the lashless fluid supply circuit  340 . 
     During operation, check ball  230  is seated in ball seat  211  when the force on the lower portion of check ball  230  is greater than the force on the top of the ball. The force acting on the lower portion of check ball  230  is provided by the hydraulic pressure of lashless fluid supply circuit  340  and check spring  235 . The force acting on the upper portion of check ball  230  is due to the hydraulic pressure of constant low pressure supply circuit  330 . During positive power operation, when rocker arm  400  is rotated off the base circle of the cam lobe (not shown), check ball  230  is biased upward by check spring  235 , because the low pressure hydraulic fluid from constant low pressure supply circuit  330  transmits less force than that from check spring  235 . When rocker arm  400  (not shown) is on the base circle of the cam lobe, the pressure of the lashless fluid supply circuit  340  is less than the pressure of the constant low pressure supply circuit  330 , thus allowing lashless fluid supply circuit  340  to fill or refill if necessary. This provides checking, that is, a constant directional flow of the hydraulic fluid, and provides automatic lash adjustment. 
     Referring now to FIG. 4 a , engine valve assembly  10  operates during Stage  1  of positive power mode as follows: piston  130  is in a lowered position. Lower end of piston  131  is maintained in contact with swivel foot  120  and the engine valve stem  105  by means of the hydraulic pressure from lashless fluid supply circuit  340 , and engine valve  100  is closed. Accumulator  140  is biased upward by accumulator spring  145 . In this position, hydraulic fluid that has accumulated behind accumulator  140  may flow to atmosphere through washer bore  251  in ductile lock washer  250  as the accumulator indexes. This allows rocker arm  400  (not shown) to follow the normal cam profile, and permits the auxiliary cam profile (braking bump  411 , not shown) to be absorbed by the accumulator, resulting in normal exhaust valve motion. 
     Stage  2  of positive power operation is shown in FIG. 4 b . Hydraulic fluid that has accumulated behind accumulator  140  has flowed to atmosphere via accumulator supply circuit  350 , lower annulus  262  and washer bore  251 , and accumulator  140  is fully indexed. Piston  130  moves upward to absorb the braking portion of the lost motion cam lobe profile (not shown). The net result is that rocker arm  400  (not shown) only follows the exhaust profile of the cam lobe profile. 
     Referring now to FIG. 3, control value  20  is shown during braking mode of engine operation. A solenoid switch (not shown) is turned on. Hydraulic fluid flows through switched low pressure supply circuit  320  into control valve bore  204 , and as the pressure of the hydraulic fluid becomes greater than the upward force of control valve spring  240 , control valve body  200  begins to index or move downward. A minimum hydraulic fluid pressure is required to index control valve body  200 . The required pressure is determined by the size of control valve spring  240  and the wetted surface area of the control valve body  200 . 
     Check ball  230  is biased upward by check spring  235 , because the low pressure hydraulic fluid from constant low pressure supply circuit  320  transmits less force than that from check spring  235 . This provides checking, that is, a constant directional flow of the hydraulic fluid, and provides automatic lash adjustment during braking operation. Check ball  230  is checked when rocker arm  400  is on an elevated section of the cam lobe (not shown). When rocker arm  400  is on the base circle of the cam lobe, the circuit is allowed to fill or make up hydraulic fluid lost to leakage. 
     When control value  20  is fully indexed, as shown in FIGS. 3 and 5, upper annulus  260  is aligned with constant low pressure supply circuit  330 , middle annulus  261  is aligned with both lashless fluid supply circuit  340  and accumulator control circuit  350 , and hydraulic fluid flows from both circuits  340  and  350  in engine valve assembly  10 . This allows checked hydraulic fluid to fill behind accumulator  140 , preventing the accumulator from indexing. When rocker arm  400  (not shown) rotates in response to the motion of a rotating cam  410  (not shown), lashless fluid supply circuit  340  and accumulator control circuit  350  become pressurized. When circuits  340  and  350  are hydraulically locked, the motion of cam  410  is translated directly into the motion of engine valve  100 . The rocker arm  400  (not shown) must follow the auxiliary cam profile (braking bump  411 ) and transmit this motion to engine valve  100 . In this position, the additional motion causes engine valve  100  to lift greater than experienced under positive power. This may require substantial valve-to-piston clearance or the presence of piston pockets. Providing a clipping function (as described below) may eliminate the need for piston pockets. 
     Referring now to FIG. 5, engine valve assembly  10  operates during braking mode as follows: hydraulic fluid from lashless fluid supply circuit  340  enters piston bore  106  at upper end of piston  132  and biases piston  130  downward. The motion of piston  130  is linearized through swivel foot  120  when contact is made with upper end of the valve stem  105 , and the downward force compresses engine valve spring  110 , opening engine valve  100 , which results in a compression release braking event. 
     Referring now to FIGS. 6 a  and  6   b , an alternate embodiment of the present invention is shown as rotationally-driven lost motion rocker brake assembly  2 . FIG. 6 b  depicts the rotationally-driven lost motion rocker brake assembly of FIG. 6 a , rotated 90° about a vertical axis. As embodied herein, rotationally-driven lost motion rocker brake assembly  2  comprises rocker arm  400 , having a first end  401  and a second end  402 , cam  410 , spring  490  and control valve  21  (not shown). First end of rocker arm  401  further comprises cam roller follower  415 . 
     Control valve  21  (not shown) comprises only the shuttle valve features of control value  20  described in connection with FIGS. 1-5 above, that is, control valve body  200  having an upper end  201  and a lower end  202 , and slidably disposed in control valve bore  204  about longitudinal axis  203 , control valve spring  240 , which biases control valve body  200  upward, and ductile lock washer  250 , which locks control valve body  200  in control valve bore  204 . As in control value  20 , control valve spring  240  prevents movement of control valve  21  unless adequate hydraulic fluid pressure is provided at the top of control valve body  200 . After the indexing hydraulic fluid supply is turned off, control valve spring  240  returns control valve body  200  to its initial, biased upward position. Ductile lock washer  250  provides a simple means to lock the assembly of control valve body  200  in control valve bore  204 , and provides a solid stop to limit the travel of control valve body  200 . Ductile lock washer  250  further comprises washer bore  251 , through which hydraulic fluid may flow to atmosphere. 
     As embodied herein, rotationally-driven lost motion rocker brake assembly  2  further comprises engine valve  10  as described in connection with FIGS. 1-5 above. Engine valve  10  comprises piston bore  106 , which is disposed in rocker arm  400  and piston  130 , which is slidably disposed in piston bore  106 . Piston  130  further comprises lower end  131  and upper end  132 , and is held in place in piston bore  106  during assembly by piston retaining ring  133 . Lower end  131  of piston  130  is shaped to seat in swivel foot  120 . Top end face  134  forms the top surface of upper end  132  of piston  130 . 
     With continuing reference to FIGS. 6 a  and  6   b , engine valve assembly  10  further comprises accumulator  140 , which is slidably disposed within accumulator bore  141  in upper end  132  of piston  130 , and accumulator spring  145 , which biases accumulator  140  toward washer  146 . Washer  146  is held in place by accumulator retaining ring  147 . Washer  146 , accumulator retaining ring  147 , accumulator  140 , and accumulator bore  141  together proscribe the indexing distance of accumulator  140 . piston bore  106 , piston  130 , accumulator bore  141 , and accumulator  140  are housed in second end of rocker arm  402 . 
     As embodied herein, engine valve assembly  10  further comprises engine valve  100 , having engine valve stem  105  and swivel foot  120 , which is disposed on upper end of engine valve stem  105 . As described above in connection with FIGS. 1-5, lower end  131  of piston  130  is seated on swivel foot  120 . 
     As embodied herein, rocker arm  400  rotates about rocker shaft  405  in response to rotation of cam  410 , which urges cam roller follower  415  upward. Spring  490  is provided to counter inertial effects of the rotating rocker arm  400 . Rocker arm  400  further comprises lost motion rocker assembly  420 . Lost motion rocker assembly  420  comprises accumulator control circuit  350  disposed therein, and clipping/reset passageway  455  connected thereto. 
     Rocker shaft  405  further comprises switched low pressure supply circuit  320 , which is connected to piston bore  106  (passageway is not shown), and rocker shaft bore  406  with clipping/reset spool  450  slidably disposed therein. Clipping/reset spool  450  may be connected to gear  440 , or may be given rotation though a different auxiliary source. Gear  440  is connected to a source of rotational motion (not shown) in the engine. Clipping/reset spool  450  further comprises a plurality of clipping annuluses  451 . Each clipping annulus  451  comprises a reduced diameter around a portion of clipping/reset spool  450 . A portion of each clipping annulus  451  has the same outer diameter as clipping/reset spool  450 . It is this full diameter portion of each clipping/reset annulus that closes off flow hydraulic fluid to clipping/reset passageway  455 . When clipping/reset passageway  455  is not closed, hydraulic fluid may dump to the main hydraulic fluid supply. When clipping/reset passageway  455  is closed, the circuit is hydraulically locked and rocker arm  400  is allowed to follow braking bump  411 . 
     Clipping/reset passageway  455  connects clipping/reset spool  450  to accumulator control circuit  350 . In the alternate embodiment of FIGS. 6 a  and  6   b , accumulator control circuit  350  further comprises check valve  460 , which is biases toward accumulator  140  by check spring  470 . Pipe plug  480  seals accumulator control circuit  350  at first end of rocker arm  401 . 
     It is to be understood that although two lost motion rocker assemblies  420  are shown in FIG. 6 a , the present invention contemplates that a lost motion rocker assembly is present for each cylinder of the engine. Thus for a standard six-cylinder engine, the present invention would comprise six lost motion rocker assemblies, each connected to the next by intake rocker  430 . 
     With continuing reference to FIGS. 6 a  and  6   b , rotationally-driven lost motion rocker brake assembly  2  operates as follows in braking mode: in response to a source of rotational motion (not shown) in the engine, gear  440  rotates and turns clipping/reset spool  450  about first horizontal axis  403 . A solenoid switch is turned on by the operator to supply hydraulic fluid which rotates or indexes control valve  21  (not shown). Control valve  21  rotates, opening and closing the port. When the port is open, hydraulic fluid exhausts, and when it is closed, the fluid is hydraulically locked. Each lost motion exhaust rocker assembly  420  has its own separate on/off port control. This allows hydraulic fluid to evacuate from rocker brake assembly  2 , which in turn permits engine valve  100  to clip or reset. 
     As contemplated by the present invention, when rocker brake assembly  2  is in braking mode, control valve  21  is fully indexed and is blocked from exhausting hydraulic fluid to atmosphere. The presence of accumulator control circuit  350  allows accumulator  140  to separately exhaust to atmosphere at a timed interval. The interval is timed so that piston  130  moves upward into rocker arm  400 , absorbing the braking bump  411  on the profile of cam  410 . This innovation allows the clipping or resetting of the engine valve in a lost motion system, thereby precluding the need for piston pockets. 
     Referring now to FIG. 7, another alternate embodiment of the present invention is shown as linear-activated lost motion rocker brake assembly  3 . This embodiment comprises the same features (see description above in connection with FIGS. 6 a  and  6   b ) as rotationally-driven lost motion rocker brake assembly  2 , with the exception that gear  440  or other source of rotational motion is replaced by a source of linear activation (not shown) that urges clipping/reset spool  450  in a linear motion instead of a rotational motion. When the linear motion actuates clipping/reset spool  450  in, the plurality of clipping annuluses  451  line up and this causes hydraulic fluid to be evacuated from lost motion rocker brake assembly  3 , allowing engine valve  100  to clip to reset. When the linear motion actuates clipping/reset spool  450  out, the plurality of clipping annuluses  451  do not line up and clipping does not occur. When in braking mode, spool annuluses  451  will index every cycle. During the cycle, the full diameter portion of each spool annulus  451  will cover the clipping/reset passageway  455  when accumulator  140  needs to be locked into place. Rocker arm  400  will follow the braking bump  411 . Around-top dead-center, the linear or rotationally activated valve will move so that the hydraulic fluid that is trapped behind control value  20  will exhaust. 
     Referring now to FIG. 8, another alternate embodiment of the present invention is shown as miniature axial flow check valve  4 . Check valve  4  is contained within a bore and comprises check ball  230 , which is disposed in control valve body  200  and is biased upward into ball seat  211  by check spring  235 . Check ball  230  provides the hydraulic fluid checking function. Arrows show the flow of hydraulic fluid in the top and out the bottom of check valve  4 . 
     Referring now to FIGS. 9 and 10, another alternate embodiment of the present invention is shown as miniature radial flow check valve  5 . Check valve  5  is contained within a bore and comprises check ball  230 , which is disposed in control valve body  200  and is biased upward into ball seat  211  by check spring  235 . Check ball  230  provides the hydraulic fluid checking function. Arrows show the flow of hydraulic fluid in the top and out the side of check valve  5 . 
     Check valves  4  and  5  may be used in valve actuation assembly  1 , rotationally-driven lost motion rocker brake assembly  2 , or linear-activated lost motion rocker brake assembly  3 . 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the construction, configuration, and/or operation of the present invention without departing from the scope or spirit of the invention. In the embodiments of control value  20  mentioned above, various changes may be made without departing from the scope and spirit of the invention. For example, ductile locking ring  220  provides an efficient way to lock the control valve assembly together, but it may be replaced by threading the parts together or through other assembly techniques. Ductile lock washer  250  is contemplated for use with a high speed assembly, but it may be replaced with a snap ring and washer or other locking device. Further, it may be appropriate to make additional modifications or changes to the individual components, including, but not limited to, the washers, rings, or other materials without departing from the scope of the invention. 
     In the embodiments of the clipping/reset system described herein, an indexing or rotating valve may be located in a ported rocker arm or shaft and used to open the port in the rocker arm or shaft, permitting hydraulic fluid to evacuate from the lost motion rocker, the allowing the valve to clip or reset. 
     Thus, it is intended that the present invention cover the modifications and variations of the invention provided they come within the scope of the appended claims and their equivalents.