Engine braking apparatus with mechanical linkage and lash adjustment

An apparatus for modifying engine valve lift to produce an engine valve event in an internal combustion engine comprises actuation device for operating at least one exhaust valve, and control device for moving the actuation device between its inoperative position and operative position. In the inoperative position, the actuation device is disengaged from the at least one exhaust valve, and in the operative position, the actuation device holds open the at least one exhaust valve to produce the modified engine valve lift for the engine valve event, which includes an engine braking event. The actuation device includes a motion limiting apparatus for controlling movement of the actuation device. The actuation device can be integrated into a valve bridge and other valve train components, such as a rocker arm, wherein a plunger is slidably disposed between the inoperative position and the operative position.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates generally to the modification of engine valve lift for producing an engine valve event in an internal combustion engine, particularly to engine braking apparatus and methods for converting an internal combustion engine from a normal engine operation to an engine braking operation.

2. Prior Art

It is well known in the art to employ an internal combustion engine as brake means by, in effect, converting the engine temporarily into a compressor. It is also well known that such conversion may be carried out by cutting off the fuel and opening the exhaust valve(s) at or near the end of the compression stroke of the engine piston. By allowing compressed gas (typically, air) to be released, energy absorbed by the engine to compress the gas during the compression stroke is not returned to the engine piston during the subsequent expansion or “power” stroke, but dissipated through the exhaust and radiator systems of the engine. The net result is an effective braking of the engine.

An engine brake is desirable for an internal combustion engine, particularly for a compression ignition type engine, also known as a diesel engine. Such engine offers substantially no braking when it is rotated through the drive shaft by the inertia and mass of a forward moving vehicle. As vehicle design and technology have advanced, its hauling capacity has increased, while at the same time rolling and wind resistances have decreased. Accordingly, there is a heightened braking need for a diesel-powered vehicle. While the normal drum or disc type wheel brakes of the vehicle are capable of absorbing a large amount of energy over a short period of time, their repeated use, for example, when operating in hilly terrain, could cause brake overheating and failure. The use of an engine brake will substantially reduce the use of the wheel brakes, minimize their wear, and obviate the danger of accidents resulting from brake failure.

There are different types of engine brakes. Typically, an engine braking operation is achieved by adding an auxiliary engine valve event called an engine braking event to the engine valve event for the normal engine operation. Depending on how the engine valve event is produced, an engine brake can be defined as:(a) Type I engine brake—the engine braking event is produced by importing motions from a neighboring cam, which generates the so called Jake brake;(b) Type II engine brake—the engine braking event is produced by altering existing cam profile, which generates a lost motion type engine brake;(c) Type III engine brake—the engine braking event is produced by using a dedicated cam for engine braking, which generates a dedicated cam (rocker) brake;(d) Type IV engine brake—the engine braking event is produced by modifying the existing valve lift, which normally generates a bleeder type engine brake; and(e) Type V engine brake—the engine braking event is produced by using a dedicated valve train for engine braking, which generates a dedicated valve (the fifth valve) engine brake.

The engine brake can also be divided into two big categories, i.e., the compression release engine brake (CREB) and the bleeder type engine brake (BTEB).

Compression Release Engine Brake (CREB)

Conventional compression release engine brakes (CREB) open the exhaust valve(s) at or near the end of the compression stroke of the engine piston. They typically include hydraulic circuits for transmitting a mechanical input to the exhaust valve(s) to be opened. Such hydraulic circuits typically include a master piston which is reciprocated in a master piston bore by a mechanical input from the engine, such as the pivoting movement of the fuel injector rocker arm. Hydraulic fluid in the circuit transmits the motion of the master piston to a slave piston in the circuit, which in turn, reciprocates in a slave piston bore in response to the flow of hydraulic fluid in the circuit. The slave piston acts either directly or indirectly on the exhaust valve(s) to be opened during the engine braking operation. This is a Type I engine brake.

An example of a prior art CREB is provided by the disclosure of Cummins, U.S. Pat. No. 3,220,392 (“the '392 patent”), which is hereby incorporated by reference. Engine braking systems based on the '392 patent have enjoyed great commercial success. However, the prior art engine braking systems have certain inherent disadvantages that have limited their application to primarily larger vehicles such as heavy duty trucks (and typically, on engines having a displacement of about 10 liters or more), and their retrofit to existing engines is largely impossible without substantial modification of the engine cylinder head.

One of the disadvantages associated with the conventional prior art CREB system is due to the fact that the load from engine braking is supported by the engine components. Because the engine braking load is much higher than the normal engine operation load, many parts of the engine, such as the rocker arm, the push tube, the cam, etc. must be modified to accommodate the engine braking system. Thus, the overall weight, height, and cost of using the prior art CREB system are likely to be excessive, and limit its commercial application.

Another disadvantage associated with the conventional prior art CREB system is the high and unique noise generated by the releasing of high-pressure gas or “blow down” through the exhaust valve(s) during the compression stroke, near the top dead center position of the engine piston.

Additional disadvantages of the prior art systems reside in their relative complexity and the necessity for using precision components because they require accurate timing and hydraulic actuators capable of opening the exhaust valves precisely when required. Thus they may be comparatively expensive and difficult or impossible to install on certain engines.

Yet another disadvantage associated with the conventional prior art CREB system of hydraulic type is the compliance of the braking system, which may cause the braking valve lift to collapse at the peak braking load (near compression top dead center (TDC) of the engine piston) and further increase the braking load. The large reduction of braking valve lift due to compliance will reduce the braking performance and excessive braking load may cause engine damage.

Bleeder Type Engine Brake (BTEB)

The operation of a bleeder type engine brake (BTEB) has also long been known. During bleeder type engine braking, in addition to the normal exhaust valve lift, the exhaust valve(s) may be held slightly open during a portion of the cycle (partial-cycle bleeder brake) or open continuously throughout the non-exhaust strokes (intake stroke, compression stroke, and expansion or power stroke) (full-cycle bleeder brake). The primary difference between a partial-cycle bleeder brake and a full-cycle bleeder brake is that the former does not have exhaust valve lift during most of the intake stroke. An example of BTEB system and method is provided by the disclosure of the present inventor, U.S. Pat. No. 6,594,996, which is hereby incorporated by reference.

Usually, the initial opening of the braking valve(s) in a bleeder braking operation is far in advance of the compression TDC and then the braking valve lift is held constant for a period of time. As such, a BTEB may require much lower force to open the valve(s) due to early valve actuation, and generates less noise due to continuous bleeding instead of the rapid blow down of the CREB. Moreover, a BTEB often requires fewer components and can be manufactured at a lower cost. Thus, a BTEB can overcome some of the disadvantages of the CREB. Indeed, the BTEB systems have achieved certain commercial success, especially in the application to smaller vehicles, such as the middle and light duty trucks (and typically, on engines having a displacement of less than 10 liters). Following are some BTEB systems that are currently on the market.

(a) BTEB Operated by Rocker Arm with Eccentric Shift

U.S. Pat. No. 5,335,636 discloses a bleeder type engine brake (BTEB) system wherein the pivot center of the engine exhaust rocker arm is displaced or shifted in a downward direction by an eccentric that is connected to a hydraulic piston/actuator by a level arm. The displacement or shift of the rocker arm pivot center causes the exhaust valves to open during braking operation of the engine to create a partial cycle bleeder braking event. This is a Type IV engine brake.

The BTEB system of the type described above requires an extra mechanical component between the hydraulic piston or actuator and the rocker arm. The system also requires intermediate arms, a second rocker arm eccentric bore, features on the small end of the actuation/pivot arm and features on the mechanical actuation end of the piston. These parts and features all add cost and complexity, and reduce system reliability. Also, the system is integrated into the engine exhaust valve train. Load from engine braking by opening both exhaust valves is so high that other parts of the engine, such as the rocker arm, the push tube, the cam, etc. must be redesigned. Finally, such type of engine brakes cannot be retrofitted into existing engines.

(b) BTEB Operated by a Dedicated Engine Braking Valve

U.S. Pat. No. 5,168,848 discloses a bleeder type engine brake (BTEB) system that has an extra exhaust valve in addition to the normal engine exhaust valve(s). The extra exhaust valve is dedicated to engine braking and opened exclusively during braking operation of the engine. The dedicated engine braking valve is actuated by pneumatic or hydraulic means and held open to create a full cycle bleeder braking event. This is a Type V engine brake.

The BTEB system of the type described above is integrated into the cylinder head of the engine, thereby substantially conditioning its design and manufacture. The engine braking device is therefore dedicated to a particular type of engine. Moreover, the introduction of the extra exhaust valve creates an extra pocket in the combustion chamber, which increases engine emission. Also, such type of engine brakes can not be used in existing engines.

(c) BTEB Operated by Engine Valve Floating

U.S. Pat. No. 5,692,469 and U.S. Pat. No. 7,013,867 disclose a bleeder type engine brake (BTEB) system for engines with one and two exhaust valves per cylinder. The BTEB system includes a throttling device (also known as an exhaust brake) capable of raising exhaust pressure high enough to cause each exhaust valve to float near the end of each intake stroke. In this intermediate opening or floating of the exhaust valve, it is possible to intervene with the braking device so that the exhaust valve, which is about to close after the intermediate opening, is intercepted by a control piston charged with oil pressure and prevented from closing to create a partial cycle bleeder braking event. This is a Type IV engine brake.

The BTEB system of the type described above may not be reliable because it depends on the intermediate opening or floating of the braking exhaust valve, which is not consistent, both in timing and magnitude. As is well known in the art, exhaust valve floating is highly engine speed dependent and affected by the quality and control of the exhaust brake, and also the design of the exhaust manifold. There may be not enough or none valve floating for the actuation of the engine braking device at middle and low engine speeds when the engine brake is highly demanded since the engine is mostly driving at such speeds. Again, such type of engine brakes may not be able to retrofit into existing engines.

U.S. Pat. No. 6,866,017 and U.S. Pat. No. 6,779,506 disclose a bleeder type engine brake (BTEB) that is actuated and controlled by high-pressure hydraulic fluid, or oil. The hydraulic fluid is supplied from a hydraulic rail, or oil rail, to a respective fuel injector at each engine cylinder to act on a piston in the fuel injector to force a charge of fuel into the respective combustion chamber during normal engine operation. A hydraulic actuator in the engine brake uses the already available high-pressure oil to actuate and hold one exhaust valve open to create a full cycle bleeder braking event. This is also a Type IV engine brake.

The BTEB system of the type described above is dedicated to a particular type of engine that has high-pressure oil rail (source), which greatly limits its application. Sophisticated electronic control is needed to eliminate excessive oscillations of the shared common high pressure source and to ensure a smooth transition between engine braking operation and normal engine operation. Also, such type of engine brakes cannot be retrofitted into existing engines.

It is clear from the above description that the prior-art engine brake systems have one or more of the following drawbacks:

(a) The system can only be installed on a particular type of engines;

(b) The system cannot be retrofitted to existing engines;

(c) The engine braking load is carried by the engine components;

(d) The system installment needs redesign of the engine or engine components;

(e) The system has too many components and is too complex;

(f) The system increases the manufacturing tolerance requirements and is too costly;

(g) The system is not reliable and only work at certain engine speeds; and

(h) The system affects normal engine performance (emission, oil rail pressure, etc.).

SUMMARY OF THE INVENTION

The engine braking apparatus of the present invention addresses and overcomes the foregoing drawbacks of prior art engine braking systems.

One object of the present invention is to provide an engine braking apparatus that can be installed on all types of engines, especially on smaller size engines.

Another object of the present invention is to provide an engine braking apparatus that can be retrofitted to existing engines.

Yet another object of the present invention is to provide an engine braking apparatus wherein the engine (valve train) components are not subject to the heavy engine braking loads so that the installment of the engine braking apparatus does not need redesign of the engine or engine components.

Still another object of the present invention is to provide an engine braking apparatus with fewer components, reduced complexity, lower cost, and increased system reliability.

A further object of the present invention is to provide such an engine braking apparatus that contains a braking valve lash adjusting mechanism so that it does not increase the manufacturing tolerance requirements of many of the components.

Still a further object of the present invention is to provide an engine braking apparatus that is rugged and simple in construction, easy to install, reliable in operation and effective at all engine speeds.

Yet a further object of the present invention is to provide engine brake actuation means that transmit force, or the engine braking load, through mechanical linkage means that does not have high compliance and overloading problems associated with hydraulic means. The mechanical linkage means includes rotatable devices, slidable devices, ball-locking devices, and a toggle device.

Still another object of the present invention is to provide an engine braking apparatus that will not interfere with the normal engine operation.

These and other advantages of the present invention will become more apparent from the following description of the preferred embodiments in connection with the following figures.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1is a flow chart illustrating the general relationship between a normal engine operation20and an added engine braking operation10according to one version of the present invention. An internal combustion engine contains at least one exhaust valve300and an exhaust valve lifter200for cyclically opening and closing the exhaust valve during the normal engine operation20. The engine braking operation10is achieved through engine brake control means50and engine brake actuation means100that contains an inoperative position0and an operative position1. To convert the engine from its normal operation20to the braking operation10, the control means50will move the actuation means100from the inoperative position0to the operative position1, which takes place after the exhaust valve300is actuated by the exhaust valve lifter200. By default, the control means50is at its off position, the actuation means100at the inoperative position0, and the engine brake disengaged from the exhaust valve300.

FIG. 2is a schematic diagram of an engine braking apparatus with an engine exhaust valve train according to one embodiment of the present invention. A typical truck engine has two exhaust valves300aand300bper engine cylinder. The two valves are biased upwards against their seats320on the engine cylinder head500by engine valve springs310aand310bto seal gas (air, during engine braking) from flowing between the engine cylinder and the exhaust manifolds600. The exhaust valve lifter200includes a rocker arm210pivotally mounted on a rocker shaft205for transmitting a mechanical input from a cam230to the exhaust valves through a cam follower235and a valve bridge400. The cam contains a lift profile220above the cam inner base circle225for cyclically opening and closing the exhaust valves during the normal engine operation.

With continued reference toFIG. 2, the engine brake actuation means100includes a brake housing125that is fixed on the engine block (not shown). In the brake housing there is a bore120, in which a rotatable device135with a stem115rotates. Underneath the rotatable device there are two surfaces140and145that have a height difference130. The first surface140is commensurate with the operative position for the engine braking operation and the second surface145commensurate with the inoperative position for the normal engine operation. The rotatable device135is biased to the inoperative position by an engine brake control means50that is also fixed on the engine block. The control means50comprises an electromechanical system that may contain an electric motor51, such as the well-known step motor, which has a predetermined rotational angle53. The electric motor is turned on and off by electric current through the positive and negative terminals55and57on the electric motor.

The actuation means100as shown inFIG. 2is at its inoperative position and the engine brake is disengaged from the engine operation. When engine brake is needed, the control means50is turned on, which tends to rotate the actuation means100into the operative position. However, there is an intervention between the rotatable device135and the valve bridge400when the exhaust valve300ais at or near its seat320. The actuation means100is waiting for the lift or opening of the exhaust valve. Only after the exhaust valve300ais pushed down by the exhaust valve lifter200, the actuation means100can be rotated into its operative position at which the first surface140will be over the valve bridge surface405. When the exhaust valve300areturns, the valve bridge surface405will contact the first surface140on the actuation means100. Due to the height difference130between the first surface140and the second surface145, the exhaust valve300apushed out by the exhaust valve lifter200cannot close or return to its seat320but is held open to create an engine braking event.

The engine brake according to the embodiment shown inFIG. 2is a bleeder type or Type IV engine brake. The engine braking event is produced by modifying the existing engine valve lift. The modified lift of the engine braking valve300aby the actuation means100during non-exhaust strokes (intake stroke, compression stroke, and expansion or power stroke) is approximately 0.5 to 3.0 millimeters, much smaller than the lift of the same engine valve by the exhaust valve lifter200during the engine exhaust stroke. Such a small lift is within the regular valve seating ramp and the impact load between the actuation means100and the braking valve300ais small. However, we can further reduce such impact load by improving the existing exhaust valve lift profile with an even slower seating ramp starting before the valve300acontacts the actuation means100.

The load generated by the engine braking event according to the embodiment of the present invention is not passed to the exhaust valve lifter200, but to the engine block through a lash adjusting screw110that is secured to the brake housing125by a lock nut105, which avoids the excessive overall engine weight, height, and cost that were experienced with some prior art engine braking systems whose load is carried by the engine components.

A lash adjusting system with the lash adjusting screw110and the rotatable device135that is also slidable in the housing is designed for setting a lash between the actuation means100and the braking valve300a. The braking valve lash adjustment is necessary due to engine valve growth and manufacturing tolerance. The height difference130between the first surface140and the second surface145minus the braking valve lash determines the braking valve lift for the engine braking event or operation. Also, the lash adjusting screw110sits in a circumferential groove150in the rotatable device135, which forms a motion limiting means that can be used to control the rotational angle between the inoperative position and operative position.

Since the engine braking valve lift is controlled through the lash adjustment, not by a stroke limited piston, it is much less affected by the dimensional tolerance of the engine brake components. Therefore, the engine braking apparatus according to the embodiment of the present invention avoid using high cost precision components that some prior art engine braking systems require.

FIG. 3shows a similar embodiment to that shown inFIG. 2except that the engine brake control means50is an electrohydromechanical system that contains a three-way solenoid valve51a. The solenoid valve51ahas a spool58with a predetermined stroke53aand is turned on and off by an electric current through the positive and negative terminals55and57. The control means50could be remotely located and used for controlling multiple cylinder engine brakes. A fluid circuit is formed in the engine brake actuation means100and in the engine for transmitting hydraulic fluid, for example, engine oil, from the control means50to the actuation means100. When the spool58slides in the brake housing125, it opens or closes a port (an orifice)11or22to allow the engine oil into or out of the fluid circuit including a flow passage126in the brake housing125. There is an annular cut or groove127on the stem115through which the pressurized engine oil can pass to a flow passage128and spray out of a bleeding orifice129in the rotatable device135when the engine brake is turned on.

The rotatable device135is biased against the adjusting screw110to the inoperative position by a spring118that can provide both compressional and torsional preload. One end of the spring118is fixed in the brake housing125and the other end in the rotatable device135. When the liquid flows out of the bleeding orifice129, it generates a jet propulsion force opposite to the flow jet direction, which overcomes the torsional preload by the spring118and rotates the rotatable device135from the inoperative position into the operative position when the engine braking valve is pushed down by the exhaust valve lifter200. The angle of rotation is controlled by a motion limiting means defined by the circumferential groove150in the rotatable device135, which has stop surfaces against the adjusting screw110.

When engine braking is not needed, the three-way solenoid valve51ais turned off and the spool58will close the oil supply port11and open the drain port22(FIG. 3). There will be no oil jet flow out of the bleeding orifice129and thus no propulsion force on the rotatable device135so that it will return back to the inoperative position by the spring118, and the actuation means100will be disengaged from the normal engine operation. Note that the drain port22may be not needed for turning off the engine brake due to the bleeding orifice129. Therefore, a two-way solenoid valve plus the bleeding orifice may be used to replace the three-way solenoid valve51a.

Alternatively, the rotation of the rotatable device135can be achieved by other types of fluid and mechanical interaction, such as jet flow out of the brake housing125that impinges on the rotatable device135with an impulsion force; hydraulic piston in the brake housing125that acts on the rotatable device135; or mechanical means, such as gear system or rope and pulley system; electric means; magnetic means; and a combination of two or more of the above means, such as the electrohydromechanical system.

FIG. 4Ais a schematic diagram of an engine braking apparatus according to another embodiment of the present invention, in which the engine brake actuation means100contains a slidable device135athat will not rotate but only slide in the bore120of the brake housing125for the braking valve lash adjustment. The slidable device is biased up by a compression spring118aagainst the lash adjusting screw110. In the slidable device135athere is a horizontal bore415in which a braking plunger136shown with details inFIG. 4Bcan only slide due to an anti-rotation guide that is formed by two surfaces136aon the braking plunger fitting in a slot139cut underneath the bore415. The braking plunger contains a first surface140commensurate with the operative position and a second surface145commensurate with the inoperative position. The two surfaces are located on the protrusion portion of the braking plunger and have a height difference130. The braking plunger136is biased inwards to the inoperative position by a flat (or leaf) spring177. One end of the spring177is secured to the slidable device135aby at least one screw179and the other end is on the braking plunger surface136band hooked onto the protrusion136c.

Note that the slidable device135acan have different shapes. If it is a piston, then there will be a bore120ain the brake housing125to match the piston, and also an anti-rotation mechanism that is formed by a hole or a radial groove150against the lash adjusting screw110for preventing the rotation of the slidable device. If it is a rectangular or square block, then120awill be a flat surface. The stem115can also take different shapes as long as it can slide up and down in the brake housing for the lash adjustment between the engine brake actuation means and the engine braking valve.

When engine braking is needed, the control means50containing the solenoid valve51a(FIG. 3) is turned on. The pressurized engine oil gets into the flow passage126in the brake housing125, overcomes the preload by the spring177, and pushes the braking plunger136out after the exhaust valve300ais pushed down by the exhaust valve lifter200(FIG. 4A). There is a motion limiting means that controls the movement of the braking plunger136. The plunger movement or stroke is defined by the distance between the stop surface420at the left end of the slot or undercut139and the spring177whose stop surface contacts the stop surface136don the braking plunger. Once the first surface140on the braking plunger136is over the valve bridge top surface405, the exhaust valve300apushed out by the exhaust valve lifter200cannot close or return to its seat320but is held open to create an engine braking event.

The lash adjusting system for this engine braking apparatus comprises the lash adjusting screw110, the slidable device135ain the housing125, and the plunger136. It is designed for setting a lash between the brake actuation means100and the braking valve300a. The height difference130between the first surface140and the second surface145on the plunger minus the braking valve lash determines the braking valve lift for the engine braking event or operation.

FIGS. 5A and 5Bshow a similar embodiment to that shown inFIGS. 4A and 4Bexcept that the braking plunger136is biased to the inoperative position by a compression spring177a. One end of the spring sits on the slidable device135aand the other end on the braking plunger. Another difference is the motion limiting means. A pin142on the slidable device fits into an axial groove137in the braking plunger for controlling the axial motion of the braking plunger. The pin and groove combination also forms an anti-rotation guide for the braking plunger. Also the operative and inoperative surfaces140and145are undercuts on the braking plunger as shown inFIG. 5B.

FIG. 6shows another embodiment with a slidable device. Here the brake apparatus further comprises the valve bridge400. A braking plunger136as shown inFIG. 4Bnow is slidably disposed in a bore415in the valve bridge400. The plunger136is guided by an anti-rotation guide formed by two surfaces136a(FIG. 4B) on the plunger and a slot139that is cut on top of the bore415. The plunger136contains a first surface140(the operative position) and a second surface145(the inoperative position). Facing upwards to the lash adjusting screw110, the two surfaces are located on the protrusion portion of the braking plunger136and have a height difference130. The lash adjusting screw is secured to the brake housing125by a lock nut105. The braking plunger136is biased inwards to the inoperative position by the spring177. One end of the spring177is secured to the valve bridge400by at least one screw179and the other end is on the braking plunger surface136b(FIG. 4B).

FIGS. 7A and 7Bare schematic diagrams of an engine brake control means50at its on and off positions. When engine braking is needed, the control means50containing a three-way solenoid valve51ais turned on as shown inFIG. 7A, and the port11is opened to allow engine oil to a fluid circuit comprising a flow passage211in the rocker shaft205of the engine. The engine oil flow passes a radial orifice212, through an undercut213, and into a flow passage214in the rocker arm210. Note that the control means50could be remotely located and used for controlling multiple cylinder engine brakes, and the fluid circuit may reach other components of the engine.

With reference back toFIG. 6, the engine oil flows from the rocker arm210to a pressure chamber425in the valve bridge400through a flow passage410. The engine oil pressure overcomes the preload of the spring177, and pushes the braking plunger136out after the valve bridge400(and the braking valve300a) is pushed away from the adjusting screw110by the exhaust valve lifter200. The movement of the braking plunger136is controlled by a motion limiting means with a plunger stroke defined by the distance between the stop surface420on the valve bridge400and the spring177whose stop surface contacts the stop surface136d(FIG. 4B) on the braking plunger136. Once the operative surface140is out and under the adjusting screw110, the exhaust valve300apushed out by the exhaust valve lifter200cannot close or return to its seat320but is held open to create an engine braking event.

The lash adjusting system for this engine braking apparatus (FIG. 6) comprises the lash adjusting screw110, the valve bridge400, and the braking plunger136slidable in the valve bridge. The height difference130between the first surface140and the second surface145on the plunger minus the braking valve lash determines the braking valve lift for the engine braking event or operation.

When engine braking is not needed, the three-way solenoid valve51ais turned off and the spool58will close the oil supply port11and open the drain port22as shown inFIG. 7B. Without oil pressure acting on the plunger136, it will be pushed back by the spring system177. Once the second surface145is under the adjust screw as shown inFIG. 6, the engine brake means100is at the inoperative position and disengaged from the normal engine operation.

Note that the bleeding orifice418in the valve bridge is optional and used for turning off the engine brake faster or even totally eliminating the need of the drain port22. Therefore, a two-way solenoid valve plus the bleeding orifice418may be used to replace the three-way solenoid valve51a. Also a spring may be desirable to bias the rocker arm210against the valve bridge for a better sealing of the fluid from the passage214in the rocker arm to the passage410in the valve bridge.

FIG. 8Ashows a similar embodiment to that shown inFIG. 6except that the braking plunger136shown with details inFIG. 8Bis biased to the inoperative position by a special spring device138that also acts as a stop and an anti-rotation guide to the braking plunger as shown inFIGS. 8C,8D and8E. Another difference is that the first and second surfaces140and145are not on the protrusion (FIG. 4B) but undercuts on the braking plunger as shown inFIG. 8B. The bleeding orifice418in the valve bridge as shown inFIG. 6can still be used but is not shown here. Therefore the three-way solenoid valve with the drain port22inFIG. 7Bis used for turning off the engine brake.

With continued reference toFIGS. 8A and 8B, the braking plunger136is slidable in the valve bridge400and biased to the inoperative position by a spring138aof the spring device138whose details are shown inFIGS. 8C and 8D. There is an anti-rotation guide and the braking plunger with guiding surfaces136acan only slide between the two legs138bof the spring device that are fixed into the valve bridge400. The spring138aacts on surface136bof the braking plunger. The slot or cut138cin the spring fits onto the protrusion136con the plunger, which can also acts as a guide to the sliding of the braking plunger as shown inFIG. 8E. A motion limiting means controls the motion of the braking plunger136. The plunger stroke is defined by the distance between the stop surface420on the valve bridge400and the spring legs138bthat contact the stop surface136don the braking plunger as shown inFIGS. 8B to 8E.

FIG. 9Ashows another embodiment with the braking plunger136shown with details inFIG. 9Bsliding in the valve bridge400. The plunger136contains a first surface140commensurate with the operative position and a second surface145commensurate with the inoperative position. The two surfaces are on two cylindrical surfaces and have a height difference130(FIG. 9B). The braking plunger136is biased to the inoperative position (FIG. 9Awhere surface145is under lash adjusting screw110) by a coil spring177a. One end of spring177asits on a spring seat176that is mounted on the braking plunger136. The other end of the spring sits on another spring seat178. Seat178is slidable in the bore183abut normally is stopped against a pin142fixed in the valve bridge400. There is a slot137or axial cut across the bore183ain the braking piston136, which has a width slightly larger than the pin142. The pin142and the slot137can form a motion limiting means to control the movement of the braking plunger136.

When engine braking is needed, the control means50is turned on as shown inFIG. 7Ato allow engine oil to flow through the engine braking fluid circuit and into a pressure chamber425in the valve bridge400through a flow passage410(FIG. 9A). The engine oil pressure overcomes the preload of the spring177a, and pushes the braking plunger136out of the bore415after the valve bridge400(and the braking valve300a) is pushed away from the adjusting screw110by the exhaust valve lifter200. When the surface136din the slot137hits the pin142, the braking plunger136will stop moving. Now the braking plunger136is fully out or extended and the operative surface140is under the adjusting screw110, the exhaust valve300apushed out by the exhaust valve lifter200cannot close or return to its seat320but is held open to create an engine braking event.

The lash adjusting system for this engine braking apparatus (FIG. 9A) comprises the lash adjusting screw110, the valve bridge400, and the braking plunger136slidable in the valve bridge. The height difference130between the first surface140and the second surface145on the plunger (FIG. 9B) minus the braking valve lash132(FIG. 9A) determines the braking valve lift for the engine braking event or operation.

When engine braking is not needed, the control means50is turned off and there will be no or little oil supplied to the engine braking fluid circuit. The oil pressure will not be high enough and plunger136will be pushed back into the valve bridge400by the spring177a. Once the second surface145is under the lash adjusting screw110as shown inFIG. 9A, the engine brake means100is at the inoperative position and disengaged from the normal engine operation. Again, the bleeding orifice418in the valve bridge is optional and used for turning off the engine brake.

FIG. 10shows yet another embodiment with the braking plunger136slidably disposed in the valve bridge400. However, the plunger136only contains the first surface140commensurate with the operative position, while the second surface145commensurate with the inoperative position is on the valve bridge400and separated from the lash adjusting screw110by a lash132. The two surfaces140and145have a height difference130. The braking plunger136is biased to the inoperative position by a coil spring177a. One end of spring177ais on the braking plunger136and the other end on a spring seat178that is secured on the valve bridge400by at least one screw179. Seat178is also used as a stop to the braking plunger136, which limits the movement of the braking plunger136.

When engine braking is needed, the control means50is turned on (FIG. 7A) to allow engine oil to flow through the engine braking fluid circuit and into a pressure chamber425in the valve bridge400as shown inFIG. 10. The engine oil pressure overcomes the preload of the spring177a, and pushes the braking plunger136out of the bore415after the valve bridge400(and the braking valve300a) is pushed away from the adjusting screw110by the exhaust valve lifter200. The braking plunger136is stopped at the spring seat178and fully out or extended. The operative surface140is now under the adjusting screw110, and the exhaust valve300apushed out by the exhaust valve lifter200cannot close or return to its seat320but is held open to create an engine braking event.

The lash adjusting system for this engine braking apparatus (FIG. 10) comprises the lash adjusting screw110and the valve bridge400that contains the braking plunger136. The height difference130between the first surface140and the second surface145minus the braking valve lash132determines the braking valve lift for the engine braking event or operation. Instead of a cylindrical surface as shown inFIG. 10, the first surface140can be a flat surface on the braking plunger136as shown inFIG. 8A.

When engine braking is not needed, the control means50is turned off and there will be no or little oil supplied to the engine braking fluid circuit. The oil pressure will not be high enough and the plunger136will be pushed back into the valve bridge400by the spring177a. The engine brake means100now is at the inoperative position and disengaged from the normal engine operation.

FIG. 11Ashows a different embodiment of the engine brake actuation means100. It is a ball-locking device over the top surface405of the valve bridge400. The ball-locking device is contained in a lash adjusting system with the lash adjusting screw110secured to the brake housing125by a lock nut105. Depending on the position of the ball-locking device, a braking piston160can extend or retract to generate the operative position or inoperative position commensurate with the engine braking operation or the normal engine operation.

When engine braking is needed, the three-way solenoid valve51a(FIG. 3) is turned on and the port11will be open to allow engine oil into the fluid circuit comprising a flow passage126in the brake housing125. The engine oil flows into a chamber123through an annular groove121, one or more orifices122and flow passage180as shown inFIG. 11B. The oil pressure pushes the braking piston160downwards with the ball-locking piston165against a spring177a. The spring is supported by a spring seat178that is secured to the lash adjusting screw by screws179. The braking piston160will slide in a bore415and stop at a clip ring176when a plurality of balls175contained in holes in the braking piston are aligned with an annular groove170in the bore415. The oil pressure overcomes the preload of spring199and pushes the ball-locking piston165down to the bottom of the bore182in the braking piston, which locks the balls in the groove170. Now the braking piston160is at its extended position with a lift130, and the exhaust valve300apushed out by the exhaust valve lifter200(FIG. 11A) cannot close or return to its seat320but is held open by the braking piston160to create an engine braking event. The engine braking load from the braking piston is passed to the lash adjusting screw110through the balls175. Note that the bleeding orifice168is designed to drain the oil leaked to the backside of the ball-locking piston to avoid hydraulic lock.

The lash adjusting system for this engine braking apparatus comprises the lash adjusting screw110, the ball-locking system contained in the lash adjusting screw, and the valve bridge400. The height difference130between the retracted position and the extended position of the ball-locking device minus the braking valve lash determines the braking valve lift for the engine braking event or operation.

When engine braking is not needed, the solenoid valve51ais turned off and the spool58will close the oil supply port11and open the drain port22as shown inFIG. 3. Without oil pressure acting on the ball-locking piston165, it will be pushed upwards by the spring199and the balls forced into the recess or annular cut of the ball-locking piston165under the upward push of the braking piston160by the spring177a. Once the balls are out of the annular groove170in the bore415, the braking piston160is free to move up and back to its retracted position when the engine brake actuation means100is disengaged from the engine operation, as shown inFIG. 11A.

FIGS. 12A and 12Bshow a similar embodiment to that shown inFIGS. 11A and 11Bexcept that the balls175of the ball-locking device are contained in holes in the lash adjusting screw110and the ball-locking piston165is at the outside of the lash adjusting screw. When engine brake actuation means100is at its inoperative position, the braking piston160is biased up by the spring177or the returning braking valve300aand retracted in the bore415as shown inFIG. 12A. Note that the braking piston is part of the lash adjusting system, and the motion limiting means is formed by the ball-locking means.

When engine brake is needed, the engine brake control means50(FIG. 3) is turned on and oil pressure pushes the braking piston160down against the spring177to a stop176so that the balls are aligned with an annular groove170aon the braking piston. Now the ball-locking piston165can be pushed down by the oil pressure against a spring199aand lock the balls into the groove170aas shown inFIG. 12B. The braking piston160is now at its extended position with a lift130, and the exhaust valve300apushed out by the exhaust valve lifter200(FIG. 12A) cannot close or return to its seat320but is held open by the braking piston160to create an engine braking event. The engine braking load from the braking piston160is passed to the lash adjusting screw110through the balls175.

When engine braking is not needed, the engine brake control means50(FIG. 3) is turned off and there will be no oil pressure acting on the ball-locking piston165, which will be pushed upwards by the spring199atoward the top of the bore182. Once the annular groove170on the ball-locking piston165is aligned with the balls175in the adjusting screw holes, they will move out of the annular groove170aand the braking piston160is free to be moved up in the bore415by the spring177and the upward valve motion. The braking piston160is now back to the retracted position and the actuation means100is disengaged from the engine operation, as shown inFIG. 12A.

FIGS. 13A and 13Bshow another ball-locking device with the balls175not contained in holes as in the previous embodiments but restrained by three elements or surfaces. The first surface is the tapered surface192on the bottom of the adjusting screw110. The second surface is the flat surface on the top of the braking piston160. The third surface is on the ball-locking piston165, either on the annular groove170when the ball-locking device is at the retracted position as shown inFIG. 13Aor on the bore415when the ball-locking device is at the extended position as shown inFIG. 13B. Note that the braking piston160is also part of the motion limiting means incorporated into the ball-locking device.

When engine brake is needed, the control means50(FIG. 3) is turned on and oil pressure pushes down both the ball-locking piston165and the braking piston160, while the balls175move down and inwards along the tapered surface192. Note that the adjusting screw stem191is smaller than the braking piston160that slides in the bore415inside the ball-locking piston. Once the balls are out of the annular groove170in the bore415, the ball-locking piston can move down further. The total travel of the system is limited by the spring177that acts as a spring and a stop. Now the braking piston is at its extended position and locked with the lift130as shown inFIG. 13B, which is finalized by the upward push of the returning braking valve300a. The engine braking load is passed from the braking piston160to the lash adjusting screw110through the balls175.

The lash adjusting system for the engine braking apparatus comprises the lash adjusting screw110, the ball-locking system in the housing, and the valve bridge400(FIG. 11A). The height difference130between the retracted position and the extended position of the ball-locking device minus the braking valve lash determines the braking valve lift for the engine braking event or operation.

When engine braking is not needed, the control means50(FIG. 3) is turned off and there will be no oil pressure acting on the ball-locking piston165, which will be pushed upwards by the spring199atowards the top of the bore182. The balls are now aligned with and forced into the annular groove170in the ball-locking piston165and the braking piston160can be pushed up by the spring177or the returning braking valve300aand back to its retracted position as shown inFIG. 13A.

FIGS. 14A and 14Bshow another ball-locking device with balls175restrained by three elements or surfaces. The first surface is the tapered surface192on the braking piston160. The second surface is the bottom flat surface on the lash adjusting screw110and the third surface on the ball-locking piston165that slides in a bore182in the adjusting screw. Again, the braking piston160is part of the lash adjusting system and the motion limiting means is incorporated into the ball-locking device.

When engine brake is needed, the control means50(FIG. 3) is turned on and oil pressure pushes down the braking piston160to a stop178, while the balls175move outward along the tapered surface192. Due to the oil pressure on the ball-locking piston165, it is pushed upward against the spring199. The venting orifice168on top of the adjusting screw110is designed to eliminate hydraulic lock of the ball-locking piston165. The tapered surface192and balls175are so designed that when the braking piston160is at its extended position, the ball-locking piston165is at the highest position and its large diameter surface locks the balls into a position shown inFIG. 14B. The height difference130between the retracted position and the extended position of the ball-locking device minus the braking valve lash determines the braking valve lift for the engine braking event or operation. The engine braking load is passed from the braking piston160to the lash adjusting screw110through the balls175.

When engine braking is not needed, the control means50(FIG. 3) is turned off and there will be no oil pressure acting on the ball-locking piston165, which will be pushed downward by the spring199so that the balls175can move inward. The braking piston160can now slide upward in the bore415under the push of spring177or the returning braking valve300a. Note that the force by spring177on the braking piston160is higher than that by spring199on the ball-locking piston165so that the ball-locking device could be back to its retracted position as shown inFIG. 14A.

FIGS. 15A and 15Bshow a different embodiment of the engine brake actuation means100. It is a toggle device that contains two pins184and186, and a braking piston160that slides in a vertical bore415in the brake housing125. The upper pin184has two spherical ends; one engaged with a socket in the adjusting screw110, and the other with another socket in the lower pin186whose lower end sits in a third socket in the braking piston160.FIG. 15Ashows the retracted position of the toggle device where the two pins guided in the slot137that is cut through a pin-locking piston162are pushed to the left by the spring199a. The pin-locking piston162slides in a horizontal bore182in the braking housing125. There is a smaller pin-locking piston164that slides in the larger pin-locking piston162. The slot137in piston162has a width that matches the diameter of the two pins and a length that is smaller than the diameter of the bore415. There will be always contact (no separation) among the braking piston, the lower pin, the upper pin, and the adjusting screw due to the upward force of the spring177that is secured to the brake housing125with at least one screw179.

When engine brake is needed, the control means50(FIG. 3) is turned on and oil pressure can push both pin-locking pistons162and164to the right against the preload of the spring199a. Note that the small pin-locking piston164can be moved to the right further to lock the two pins in a vertical position, aligned with the adjusting screw and the braking piston, as shown inFIG. 15B. Now the toggle device is locked to its extended position. The motion limiting means for this toggle device is unique. The angle between the two pins decides the height difference130, while the angle itself is controlled by the two pin-locking pistons. The pin-locking piston162has a stroke131. The two bleeding orifices168and169are designed to eliminate hydraulic lock so that the two pistons can move freely. The orifice169is in a mounting screw161that acts as a spring seat and a stop to the large pin-locking piston162.

Again, a bleeding orifice could be added to the flow passage126in the engine braking fluid circuit for turning off the engine brake faster or even totally eliminating the need of the drain port22(FIG. 3), so that a two-way solenoid valve plus the bleeding orifice may be used to replace the three-way solenoid valve51a.

The lash adjusting system is incorporated into the toggle device. The height difference130between the retracted position and the extended position of the toggle device minus the braking valve lash determines the braking valve lift for the engine braking event or operation. The engine braking load is passed from the braking piston160to the lash adjusting screw110through the two pins184and186.

CONCLUSION, RAMIFICATIONS, AND SCOPE

It is clear from the above description that the engine braking apparatus according to the embodiments of the present invention have one or more of the following advantages over the prior art engine braking systems:(a) The system can be installed on all types of engines;(b) The system can be retrofitted to existing engines;(c) The engine braking load is not carried by the engine (valve train) components;(d) The system has no need for redesign of the engine or engine components;(e) The system has fewer components, reduced complexity, and lower cost;(f) The system has a braking valve lash adjusting system;(g) The system is more rugged and simple in construction, easier to install, more reliable in operation, and effective at all engine speeds; and(h) The system transmits force, or the engine braking load, through mechanical linkage means that does not have high compliance and overloading problems associated with hydraulic means used by some of the prior art engine brakes.

Due to the above advantages, the engine braking apparatus disclosed here can be used not only on truck engines, but also personal car engines; not only to slow down vehicles, but also to enhance vehicle cruise control, braking gas or exhaust gas recirculation control, and other engine or vehicle controls.

While my above description contains many specificities, these should not be construed as limitations on the scope of the invention, but rather as an exemplification of the preferred embodiments thereof. Many other variations are possible. For example, instead of sitting over the top surface405of the valve bridge400for opening one exhaust valve300afor engine braking as shown inFIG. 2and other figures, the engine brake actuation means100can sit over the top surface215of the rocker arm210or under the bottom surface of the rocker arm210on the cam follower235side for opening two exhaust valves300(300aand300b) for engine braking. The top surfaces could have different shape other than flat surface, for example, a spherical shape.

Also, instead of one plunger136in one side of the valve bridge400for opening one exhaust valve300afor engine braking as shown inFIG. 6and other figures, two plungers136can be put in both sides of the valve bridge400for opening two exhaust valves300(300aand300b) for engine braking.

Also, the engine braking apparatus disclosed here can be applied to a push tube type engine (not shown here) instead the overhead cam type engine as shown inFIG. 2and other figures, as well as to the engine's intake valve system (not shown here) instead the exhaust valve system.

Also, the engine brake actuation means100can be controlled (turned on and off) by other types of control means50, like a simple mechanical means, such as the wire control mechanism for a bicycle brake control. And a poppet type control valve could be used to replace the spool type valve51aof the control means50as shown inFIG. 3.

Also, the two surfaces140and145commensurate with the operative and inoperative positions of the engine brake actuation means100as shown inFIG. 2and other figures can be combined as one tapered or sloped surface, for example, a wedge type mechanism. And the tapered surface could be actively controlled to generated variable braking valve lift, which could be very useful for different engine braking needs, for example, at different engine speeds.

Also, the housing125can be different. It can be a rocker arm mounted on a rocker shaft; and there can be a different cam that has more than one lobe.

Further, two levels of oil supply pressure could be provided to the fluid circuit as shown inFIG. 6so that during engine braking, the oil with full supply pressure flows into the braking circuit to actuate the engine braking actuation means100, while during the normal engine operation, the oil flowing through a pressure reduction device, for example, an orifice, into the braking fluid circuit does not have high enough pressure to actuate the actuation means100but can be used for system lubrication.