초록 ▼

An engine air brake device for a 4-stroke reciprocating-piston internal combustion engine is provided and has at least one intake valve and two exhaust valves per cylinder. The exhaust train incorporates a throttling device actuatable for engine deceleration so that an exhaust back pressure builds u

An engine air brake device for a 4-stroke reciprocating-piston internal combustion engine is provided and has at least one intake valve and two exhaust valves per cylinder. The exhaust train incorporates a throttling device actuatable for engine deceleration so that an exhaust back pressure builds up in the accumulated exhaust gas upstream of the throttling device and becomes effective in conjunction with an engine-internal braking device associated to only one of the two exhaust valves for each cylinder, the other exhaust valve being controlled conventionally. The engine-internal braking device comprises a control piston installed in the valve bridge and pressed in the direction of the exhaust valve from a control pressure chamber supplied with pressurized oil and possibly also by means of an additional control compression spring.

대표청구항 ▼

What is claimed is: 1. An engine air brake device for a 4-stroke recriprocating-piston internal combustion engine that has at least one intake valve per cylinder and two exhaust valves that are connected to an exhaust train and can be actuated via a valve bridge and a rocker arm that acts on said v

What is claimed is: 1. An engine air brake device for a 4-stroke recriprocating-piston internal combustion engine that has at least one intake valve per cylinder and two exhaust valves that are connected to an exhaust train and can be actuated via a valve bridge and a rocker arm that acts on said valve bridge and can be controlled by a camshaft either directly or indirectly via a push rod, each exhaust valve being biased in a closing direction by means of a closing spring, whereby a throttling device is installed in said exhaust train and can be actuated for engine deceleration such that an exhaust back pressure builds up in accumulated exhaust gas upstream of said throttling device and becomes engine-internally active for engine deceleration in conjunction with a braking device, which comprises: an engine internal braking device associated with only one of said two exhaust valves for each cylinder, wherein said braking device is provided with a control piston against which a valve stem of said one exhaust valve is supported, wherein said control piston is moveably guided axially in a blind bore of said valve bridge and is adapted to be pressed in a direction of said valve stem from a control pressure chamber that is supplied with pressurized oil, and optionally from an additional control compression spring, wherein pressurized oil is supplied to said control pressure chamber via a duct that is provided in said valve bridge and communicates with a duct in said rocker arm, wherein a check valve is disposed in said duct of said valve bridge and permits flow only in a direction toward said control pressure chamber, wherein a relief duct exits said control pressure chamber and opens out on an upper side of said valve bridge, wherein a brace, which doubles as a stop for said valve bridge, is provided for closing off an outlet orifice of said relief duct and for opening said outlet orifice for relieving pressure from said control pressure chamber after raising of said valve bridge, wherein a pre-tensioning force of said closing spring that is associated with said one exhaust valve is such that during engine deceleration when said throttling device is in a throttling position, an intermediate opening of said one exhaust valve is effected due to exhaust back pressure accumulated in the exhaust gas in conjunction with pressure pulsations effective therein, wherein in such intermediate opening it is possible to intervene with said engine-internal braking device during each 4-stroke engine cycle in a control-related automatic manner so that after the intermediate opening at the beginning of a second stroke said one exhaust valve, which is about to close, is intercepted by the approaching oil-pressure-charged control piston, is prevented from closing during second and third strokes, and is kept partially open until a camshaft-controlled opening at the beginning of a 4th stroke, wherein the exhaust gas pressure is highest when said throttling device is in a closing position and can, if necessary, be lowered through a controlled and/or regulated opening of said throttling device to reduce engine brake output and/or the temperature of engine-internal components, and wherein a cross-section of the oil-supply ducts, and a pressure of the oil supply to said control pressure chamber, are coordinated with each other such that during an intermediate opening of said one exhaust valve, said control pressure chamber, which enlarges in volume due to the departing control piston, can be filed with pressurized oil at least almost completely, thus ensuring that said one exhaust valve is kept in an intercepted partial opening position towards the end of an intermediate opening stroke. 2. An engine air brake device according to claim 1, wherein a front side of said control piston is provided with blind bore via which said control piston overlaps an upper end of said stem of the associated one exhaust valve in a cap-like manner and with play. 3. An engine air brake device according to claim 1, wherein one end of said control compression spring is supported on a base of a rear blind hole in said control piston, and wherein the other end of said compression spring is supported on a base of said blind bore in said valve bridge. 4. An engine air brake device according to claim 1, wherein said brace or said valve bridge is in the form of a stud bolt that is fixed in a cover of said cylinder and can be adjusted with respect to a stop position thereof. 5. An engine air brake device according to claim 1, wherein a cross-section of said oil-supply duct in said rocker arm is the same as or larger than a cross-section of said oil-supply duct in said valve bridge. 6. An engine air brake device according to claim 1, wherein said relief duct is in the form of a constriction bore that extends coaxially from a base of said blind bore in said valve bridge to an upper side of said valve bridge, and wherein a diameter of said relief duct is considerably smaller than a smallest cross-section of said oil-supply duct in said valve bridge. 7. An engine air brake device according to claim 1, wherein the effective pre-tensioning force of said valve spring of said one exhaust valve is higher than an effective pre-tensioning force of said control compression spring acting on said one exhaust valve via said control piston. 8. An engine air brake device according to claim 1, wherein the components of the engine-internal braking device, and the pressure of the pressurized oil supply to said control pressure chamber, are designed such that said one exhaust valve can be intercepted and kept in a first position during engine deceleration after its intermediate opening effected by the exhaust back pressure, and wherein the distance of said first position to the closing position of said one exhaust valve is approximately ⅕ to 1/20 of the full opening stroke of said one exhaust valve. 9. An engine air brake device according to claim 1, wherein said throttling device in said exhaust train is disposed spatially upstream of a turbine of a turbocharger. 10. An engine air brake device according to claim 1, wherein a volume of a section of said exhaust train that can be shut off by means of said throttling device is as small as possible, for which purpose said throttling device is disposed as close to said engine as possible, namely at an outlet of one or more combined exhaust manifolds, and is disposed spatially upstream of a turbine of a turbocharger. 11. An engine air brake device according to claim 1, wherein, in order to generate a braking power that is smaller than a maximum possible braking power during engine brake operation, and/or to prevent engine-internal components from overheating, said throttling device is controlled as a function of specific time intervals or of measured component temperatures and/or on the basis of data obtained from operation of a vehicle containing said engine, and wherein in the case of a vehicle engine, the control function for said throttling device is adapted to be integrated into an electronically controlled braking strategy that optimally co-ordinates the use of all brakes of said vehicle. 12. An engine air brake device according to claim 1, wherein said check valve is provided with a ball as a control organ, and an associated valve seat is in the form of a conical transition area between two oil-supply-duct sections having different diameters, and wherein said ball is disposed in that oil-supply-duct section having the larger diameter, where an opening stroke thereof is limited by a stop. 13. An engine air brake device according to claim 12, wherein said stop for limiting the opening stroke of said check-valve ball is in the form of a stop pin that passes through said oil-supply-duct having the larger diameter in a transverse direction and is pressed into a transverse bore said valve bridge. 14. An engine air brake device according to claim 12, wherein a smallest cross-section of said oil-supply duct in said valve bridge is disposed in the area of an annular gap about said ball in said valve bridge. 15. An engine air brake device according to claim 1, wherein said control piston is moveably disposed in said blind bore of said valve bridge between two stops in a low-leakage and stroke-limited manner. 16. An engine air brake device according to claim 15, wherein an upper one of said stops, which prescribes a retracted basic position for said control piston, is in the form of a shoulder face disposed in a transition area between two sections of said blind bore that have different diameters, wherein the section with the larger diameter holds said control piston, and wherein the section with the smaller diameter forms the control pressure chamber and holds said control compression spring. 17. An engine air brake device according to claim 15, wherein a lower one of said stops, which prescribes the farthest extended position of said control piston, is realized by a transverse pin that is pressed into a transverse bore in said valve bridge, wherein said transverse pin protrudes laterally into a clear cross-section of said blind bore of said valve bridge and thus extends into an outer recess on said control piston, and wherein an upper limit wall of said recess serves as said lower stop and delimits an extension stroke of said control piston. 18. An engine air brake device according to claim 15, wherein an upper one of said stops, which prescribes a retracted basic position for said control piston, is formed by a base of said blind bore in said valve bridge that forms said control pressure chamber and holds said control compression spring, wherein a central pin is disposed on a rear side of said control piston, wherein via a rear face of said pin said control piston contacts said base of said blind bore, wherein said base is provide with said relief duct so that said pin has the additional function that in each 4th engine stroke, immediately after a start of the camshaft-controlled opening-stroke movement of said valve bridge, and the resultant lifting of said valve bridge from said brace, the quantity of pressurized oil ejected via said relief duct for the purpose of relieving said control pressure chamber is limited since said relief duct is again closed by said pin of said control piston, which returns to its basic position immediately so that oil loss in said control pressure chamber can be limited and it can be ensured that oil pressure in said control pressure chamber remains high. 19. An engine air brake device according to claim 18, wherein said control compression spring is centered by said central pin on said control piston and is supported on the one hand on an annular shoulder base on said control piston and on the other hand on said base of said blind bore of said valve bridge.