EP1526257B1 - Exhaust braking device for a 4-stroke internal piston combustion engine - Google Patents

Abstract

The parking brake device (11) within the engine has only one of the two exhaust valves (2, 3) allocated to each cylinder (1), with the other being controlled in the conventional manner. The device includes a control piston (30) built into the valve bridge (20) and controlled by a compression spring (32) pressing it in the direction of the exhaust valve.

Description

The invention relates to a motor dust brake device of a 4-stroke reciprocating internal combustion engine having features according to the preamble of claim 1.

The invention is based on the EP 0736672 B1 , This discloses a method for engine braking with a 4-stroke reciprocating internal combustion engine having an internal engine, an exhaust valve associated braking device. The relevant outlet valve can be controlled via a rocker arm which can be actuated either directly or via a push rod. The parts of the braking device are disclosed as being integrated either in the rocker arm or in the area of the pushrod. For a more than two-valve engine, however, no proposed solution is given.

Furthermore, from the US 2002/174654 A1 a method for controlling the degree of engine braking in an engine known. The latter has at least one intake valve and one exhaust valve, intake and exhaust manifold, a turbocharger connected to the intake and exhaust manifolds, and an engine cylinder. The braking method comprises the steps of: actuating the at least one exhaust valve to generate a braking operation, determining a first engine parameter and generating an exhaust backpressure in the exhaust manifold in dependence on the level of the first engine parameter, the generated exhaust back pressure communicating with the engine cylinder during an engine braking operation to control the degree of engine braking. This is a method in which the engine braking effect is set in a targeted manner in terms of control and regulation depending on operating parameters. Both the method and the device means for carrying out this method are extremely complex.

In contrast, the engine dust brake device according to the initially discussed document is much simpler and self-controlling without further aids. An application of the motor braking method known from multi-valve engines, however, does not disclose this document.

It is therefore an object of the invention to provide a motor dust brake device for a 4-stroke reciprocating internal combustion engine with each cylinder at least one inlet valve and two exhaust valves, which makes it possible, an engine braking method similar to that of EP 0736672 B1 display.

This object is achieved with a motor dust brake device having the characterizing features of claim 1.

It is an essential criterion of the invention that the engine-internal brake device is not associated with two exhaust valves per cylinder, which would be difficult to implement space reasons, but was designed from the outset so that it is effective only in conjunction with one of the two exhaust valves per cylinder on the other hand, the other outlet valve is normally or conventionally operable.

This significant feature, the other features of the invention arrange, because they are turned off on the effectiveness of the engine-internal braking device on the only one exhaust valve.

In detail, the engine-internal brake device has a control piston, on which the outlet valve is supported by its shaft. The control piston is guided axially movably guided in a blind bore of the valve bridge and from a supplied with pressure oil control pressure chamber ago and possibly by an additional control spring in the direction Exhaust valve stem pressed. The pressure oil supply to the control pressure chamber via a communicating with a rocker arm internal oil supply channel valve bridge internal oil supply channel, in which the latter is installed only in the direction of control pressure chamber permeable non-return valve. From the control pressure chamber is a discharge channel, which opens at the top of the valve bridge and the outlet opening is closed by a stop for the valve bridge forming counter-lock or released for pressure relief of the control pressure chamber after lifting the valve bridge. Furthermore, the biasing force of the closing spring associated with this exhaust valve is dimensioned such that, during engine braking, when the throttle device is in the throttle position, an intermediate opening of the exhaust valve results due to the exhaust backpressure occurring in the accumulated exhaust gas in conjunction with the pressure pulsations acting therein. In this intermediate opening is during each 4-stroke engine cycle with the engine-internal braking control technology automatically engageable such that intercepted after intermediate opening at the beginning of the 2-stroke to close the exhaust valve tilted by the oil pressure and possibly also steuerdruckfederbeaufschlagt nachrückenden control piston and during the 2nd and 3rd Clock is prevented from closing and is held partially open until its beginning of the 4th clock camshaft-controlled opening. The exhaust back pressure has its maximum when the throttle device is in the closed position, but if necessary can be lowered by controlled and / or regulated opening of the throttle device in order to reduce the engine braking power and / or the temperature of internal engine components in order to avoid their overheating. The cross-section of the oil supply channels in the rocker arm and the valve bridge and the pressure of the control pressure chamber supplied oil are coordinated so that during the said intermediate opening of the exhaust valve due to the nachrückenden control piston magnifying control pressure chamber can at least almost completely fill with pressure oil and therefore at the end of Zwischenöffnungshubes holding the exhaust valve in trapped part opening position is possible.

Evidently, this engine dust brake device according to the invention with a few, inexpensive to produce components can be realized. The engine braking is automatically self-controlling without external interference only as a function of exhaust backpressure in the locked exhaust tract and demonstrably provides a very high engine braking performance.

Fig. 1

schematisch eine 4-Takt-Hubkolbenbrennkraftmaschine und deren Abgastrakt mit Drosseleinrichtung sowie einem Prinzipbild einer möglichen Steuerung für letztere,

Fig. 2

einen Teilschnitt durch eine vier-ventilige 4-Takt-Hubkolbenbrennkraftmaschine im Bereich der Auslassventile und deren Steuerung, mit einem ersten Ausführungsbeispiel der erfindungsgemäßen motorinternen Bremsvorrichtung,

Fig. 3

die Ventilbrücke und weitere Teile der motorinternen Bremsvorrichtung gemäß Fig. 2 in Einzeldarstellung und im Schnitt,

Fig. 4

eine Draufsicht auf die Ventilbrücke gemäß Fig. 2 und 3,

Fig. 5

einen vergrößerten Ausschnitt aus der Darstellung von Fig. 3,

Fig. 6

ein weiteres Ausführungsbeispiel einer Ventilbrücke und weiterer Teile der motorinternen Bremsvorrichtung in Einzeldarstellung und im Schnitt,

Fig. 7

eine Draufsicht auf die Ventilbrücke gemäß Fig. 5,

Fig. 8

einen vergrößerten Ausschnitt aus der Darstellung von Fig. 6, und

Fig. 9

ein Diagramm, aus dem der Hubverlauf des Auslassventils, dem die erfindungsgemäße motorinterne Bremsvorrichtung zugeordnet ist, während des Bremsbetriebes hervorgeht.

The solution according to the invention is explained in more detail below with reference to the drawing. In the drawing show:

Fig. 1

schematically a 4-stroke reciprocating internal combustion engine and its exhaust system with throttle device and a schematic diagram of a possible control for the latter,

Fig. 2

a partial section through a four-valve four-stroke reciprocating internal combustion engine in the region of the exhaust valves and their control, with a first embodiment of the engine-internal braking device according to the invention,

Fig. 3

the valve bridge and other parts of the engine brake according to Fig. 2 in individual representation and on average,

Fig. 4

a plan view of the valve bridge according to Fig. 2 and 3 .

Fig. 5

an enlarged section of the representation of Fig. 3 .

Fig. 6

a further embodiment of a valve bridge and other parts of the engine-internal braking device in a single representation and in section,

Fig. 7

a plan view of the valve bridge according to Fig. 5 .

Fig. 8

an enlarged section of the representation of Fig. 6 , and

Fig. 9

a diagram from which the stroke of the exhaust valve, which is associated with the engine-internal brake device according to the invention, during the braking operation emerges.

In Fig. 1 is a detail of a 4-stroke reciprocating internal combustion engine shown, the per cylinder 1 at least one inlet valve (not shown) and two exhaust valves 2, 3 has. 4, the installation space of the cylinder 1 with 5 is a piston working in the cylinder 1, 6 denotes a cylinder head and 7 a cylinder cover. The exhaust ports 8 of the cylinder 1 open into one or more exhaust manifold and form with the latter a part of the exhaust tract 9. In the exhaust tract 9, a throttle device 10 is installed as close to the engine as possible. This can be formed for example by a throttle valve or a poppet valve or a slider. In most cases, a throttle is used. The throttle device 10, including its control and / or regulating members (which will be discussed in more detail later) forms part of the engine dust brake device according to the invention and serves during engine braking operations for at least partial shut-off of the exhaust gas tract and thereby an upstream impoundment of the exhaust gas. Another part of the engine dust brake device is an engine-internal brake device 11 of the invention type, which is also discussed in more detail later. The intake and exhaust valves are controlled by a camshaft (not shown). If this is overhead, it acts directly on rocker arms. On the other hand, if it is at the bottom, it acts indirectly on the rocker arms via pushrods. Fig. 2 shows the version with bottom camshaft in the area of the control of the two exhaust valves of a cylinder. The illustrated, supported on the camshaft push rod 12 acts on a rocker arm 13 which is rotatably mounted on the cylinder head 6 in a bearing block 14 on a bearing shaft 15 with slide bearing 16. The rocker arm 13 in turn acts via an adjustable and z. B. countered by a nut 17 bolts 18 with a ball-joint hinged at its free end Stützkalotte 19 on a valve bridge 20 a. Each of these is axially movably mounted with its shaft 21 and 22 in the cylinder head 6 and by a closing spring 23 and 24, the end face on a cylinder head surface 25 and 26 and the other end to a mounted on the outlet valve 21 and 22 spring plate 27 and 28 is supported, acted upon by a certain biasing force F1 in the closing direction. Each of the two closing springs 23 and 24 can be realized either by only one spiral spring or two mutually coaxial coil springs.

According to a criterion of the invention, the engine-internal brake device 11 per cylinder 1 is assigned to only one (2) of the two exhaust valves 2, 3, the other exhaust valve 3 is normal or conventional effective and operated, therefore also in a conventional manner with the upper end of its shaft the bottom 29 of the valve bridge 20 supported.

According to the invention, the engine-internal brake device 11 assigned to one exhaust valve 2 consists of a control piston 30, on which the exhaust valve 2 is supported by the upper end of its shaft 21. The control piston 30 is taken in a given in the valve bridge 20 blind bore 31 leakage axially movable and pressed by a supplied with pressure oil control pressure chamber 33 ago and possibly by an additional control spring 32 in the direction of exhaust valve stem 21. The pressure oil supply to the control pressure chamber 33 via a rocker arm 13 and its bolts 18 formed with Abstützkalotte 19 oil supply channel 34 and communicating with this Oil supply channel 35 in the valve bridge 20. In the valve bridge internal oil supply channel 35, an oil is installed only in the direction of the control pressure chamber 33 permeable non-return valve 36. The pressure oil supply to the rocker arm 13 takes place from the outside either via a feed line into a channel in the rocker arm pin 15 and channels in the sliding bearing 16 or a supply line to the push rod 12 and a plunger rod internal channel with which the rocker arm internal oil supply channel 34 communicates.

From the control pressure chamber 33 branches off a discharge channel 37, which opens out at the top 38 of the valve bridge 20 and its local outlet opening 39 by a stop for the valve bridge 20 forming counter-holder 40 closed or for pressure relief of the control pressure chamber 33 after lifting the valve bridge 20 is releasable ,

Under normal operating conditions of the internal combustion engine, so when no engine braking is initiated, the two exhaust valves 2, 3 of a cylinder 1 via the valve bridge 20 are operated synchronously, that is, within each 4-stroke cycle to the end of the 3rd clock (expansion stroke) opened , kept open during the 4th stroke (exhaust stroke) and then closed again at the beginning of the next 1st stroke (intake stroke).

In the engine dust brake device according to the invention, the biasing force F1 of the closing spring 23 that exhaust valve 2, the engine-internal braking device 11 is assigned, such that during engine braking with befindlichem in throttle position throttle device 10 due occurring in the pent-up exhaust gas in conjunction with the pressure pulsations acting therein Exhaust counterpressure P2 adjusts an intermediate opening of the relevant exhaust valve 2, namely - as out Fig. 9 apparent - at the end of the first cycle (intake stroke) every 4-stroke cycle. In this intermediate opening of the exhaust valve 2 is intervened with the engine-internal engine brake device 11 according to the invention control technology automatically such that intercepted after intermediate opening at the beginning of the 2nd clock (compression stroke) tends to close exhaust valve 2 and prevented during the 2nd and 3rd clock closing and up is held partially open at its beginning of the 4th stroke camshaft controlled opening. On the exact procedures and within the engine-internal engine brake device 11 is discussed in more detail later.

The exhaust back pressure P2 reaches its maximum during engine braking when the throttle device 10 is in the closed position. However, it may well be useful and useful to reduce the active during engine braking exhaust back pressure P2 by controlled and / or controlled opening of the throttle device 10 away from its closed position to a targeted reduction of engine braking performance and / or the temperature of internal engine components in order to avoid their Overheating and / or coking.

In addition, within the engine-internal brake device 11 according to the invention, the cross-section of the oil supply channels 34, 35 and the effective therein and in the control pressure chamber 33 oil pressure matched such that during the said intermediate opening of the exhaust valve 2 in the engine braking operation of the nachrückenden control piston 30 by volume magnifying control pressure chamber 33 at least almost complete with pressurized oil can be filled and thus, towards the end of the intermediate opening stroke, holding of the outlet valve 2 in the intercepted partial opening position via the control piston 30 blocked on the oil side by the control pressure chamber 33 is ensured.

In the following, details and variants of the solution according to the invention are described in greater detail.

The control piston 30 of the engine-internal braking device 11 has front - to the outlet valve 2 out - a blind hole 41, with which it engages over the upper end of the exhaust valve stem 21 like a cap with play and is thus coupled to the outlet valve 2. The control piston 30 is in the valve bridge internal blind bore 31 between two stops limited stroke movable. Here, the upper, the retracted home position defining stop 42 in the case of the example according to Fig. 3 to 5 given by an annular shoulder surface at the transition between two different diameter portions of the blind bore 31, wherein the larger diameter portion receives the control piston 30 and the smaller diameter portion forms the control pressure chamber 33 and also the control spring 32 receives laterally guided. In this case, the control compression spring 32 is centered in this embodiment in a rear blind hole 44 in the control piston 30 and supported there at the bottom 45. On the other hand, the control compression spring 32 is supported on the bottom 46 of the valve bridge-internal blind bore 31. In the case of the example according to Fig. 6 to 8 By contrast, the upper, the retracted basic position of the control piston predetermining stop 42 through the bottom 46 of the valve bridge-internal blind hole educated. On the control piston 30, a coaxial pin 47 is arranged in this case on the rear side, with its rear end face 48, it comes to rest on the bottom 46 of the blind bore 31. From there, the discharge channel 37 is preferably from the center, so that the pin 47 also fulfills the additional function, namely that in every 4th engine cycle immediately after the beginning of the camshaft controlled opening stroke of the valve bridge 20 and the associated lifting the same from the backstop 40 a Pressure relief of the control pressure chamber 33 causing cumshot of pressure oil through the discharge channel 37 is limited in quantity, because the discharge channel 37 is closed by the pin 47 of the immediately returning to its normal position control piston 30 from the inside again. This limits the loss of oil in the control pressure chamber 33 and ensures a high oil pressure therein. The control compression spring 32 is supported in this case on an annular shoulder surface 49 on the control piston 30 and centered by the coaxial pin 47.

The lower, the farthest extended position of the control piston predetermining stop 43 is in both embodiments according to Fig. 3 to 5 and Fig. 6 to 8 equal and z. B. realized by a transverse pin 50 which is pressed into a transverse bore 51 in the valve bridge 20, protrudes laterally into the clear cross section of the blind hole 31 and there dips into an outer recess 52 on the control piston 30, the upper boundary wall as a stop 43 the extension stroke of the Control piston 30 limited in cooperation with the transverse pin 50.

The anvil 40 for the valve bridge 20 is connected by a cylinder cover 7 z. B. fixed by a lock nut, adjustable with respect to their stop position stud 54. The discharge passage 37, which can be shut off or released on the outlet side, is preferably formed by a throttling bore leading from the blind bore 31 coaxially to the upper side 38 of the valve bridge 20, the diameter of which is substantially smaller than the smallest cross section of the oil supply passage 35 in the valve bridge.

The check valve 36 has a ball 55 as a control member and the associated valve seat is formed by a conical transition surface 56 between two different diameter Ölzufuhrkanalabschnitten 57, 58, wherein the ball 55 disposed in the larger diameter ÖIzufuhrkanal section 58 and where the opening stroke is limited by a stop 59 , To limit the stroke of the check valve ball 55 z. B. a the oil supply passage section 58 transversely passing, provided in a transverse bore 60 in the valve bridge stopper pin provided.

The cross section of the oil supply channel 34 in the rocker arm 13 is either the same, but preferably greater than that of the subsequent oil supply channel 35 in the valve bridge 20. The smallest cross section of the oil supply channel 35 is internally the valve bridge 20 in the region of the check valve 36, there in the annular gap around the ball 55th in the oil supply passage section 58 given. In general, the check valve 36 should be positioned as close as possible to the control pressure chamber 33.

The effective biasing force F1 of the closing spring 23 of the exhaust valve 2 is greater than the effective biasing force of the valve bridge internal control spring 32. The theoretical background of the engine dust brake device according to the invention is given at the end of the description.

In general, the components of the engine-internal braking device 11 and the pressure of the control pressure chamber 33 supplied oil are designed so that the exhaust valve 2 during the engine braking after its exhaust back pressure caused intermediate opening to an open position B (see Fig. 9 ) in a position C (see Fig. 9 ) is catchable and durable, the distance to the closing position of the exhaust valve about 1/5 to 1/20 of the full Auslassventilhubes h _max = A → D (see Fig. 9 ) is.

If the internal combustion engine has an exhaust-gas turbocharger, the throttle device 10 in the exhaust-gas tract 9 should, as far as possible, be arranged upstream of the turbine of the exhaust-gas turbocharger in terms of flow. In general, the volume of the shut-off by means of the throttle device 10 section 61 of the exhaust tract 9 should be as low as possible, so the throttle device 10 as close as possible z. B. at the output of one or more merged exhaust manifold and spatially arranged in front of the turbine of the exhaust gas turbocharger.

The control of the throttle device 10 may, as also schematically from Fig. 1 can be realized. The throttle device 10 is formed there by a throttle valve, which is installed in the exhaust tract 9 and is rotatably or pivotably mounted there with its axis 62. For adjusting or adjusting the throttle valve 10 is a servomotor 63. This can be realized by an electric motor or a hydraulically or pneumatically actuable actuating cylinder. In the example shown, the servo motor 63 by a pneumatic realized actuatable actuating cylinder, which is supplied via a compressed air supply device 64 connected to a compressed air line 65 with compressed air. The servo motor 63 is associated with a power unit 66, which consists in the illustrated example of an electromagnetic shut-off / passage valve 67 and an electrical switching member 68 for actuating the latter. This power unit 66 receives its commands via a control line 69 from an electronic control and / or regulating unit 70. Designated at 71 is a pressure sensor which detects the exhaust-gas pressure in terms of flow in front of the throttle valve 10. Instead of the pressure sensor 71 or in addition to this, a temperature sensor 72 may be provided, which detects the exhaust gas temperature in terms of flow in front of the throttle valve 10. These pressure and / or temperature measurement signals, possibly also speed signals n _{M of} the internal combustion engine and temperature measuring signals t _B of temperature-monitored engine-internal components such as injectors are fed via signal lines 73, 74, 75 of the control and / or regulating unit 70 and from this as a basis for an operation of the throttle valve 10 is used. The control and / or regulating unit 70 consists for example of an input and output peripherals, a microprocessor and data and program memories, which modules are linked together via a data bus system. In the data memories maps and operating data for the operation control of the internal combustion engine are stored both in the train operation and braking operation. The control and / or regulating unit 70 thus regulates the operation of the internal combustion engine by means of programs stored in the program memory on the basis of the maps and operating data. The latter can be done during engine braking operation either by an open-close adjustment of the throttle valve 10 or in the sense of a sensitive input or adjustment of the throttle valve 10. The control and / or regulating unit 70 gives its commands via the line 69 to the switching member 68, which is connected via switching lines 76, 77 with the shut-off / passage valve 67. In order to produce an opposite of the maximum possible lower braking power during an engine braking operation or to counteract or prevent overheating of engine internal components, such z. B. depending on data given time intervals or measured component temperatures and / or other requirements, eg. B. from the operation of the vehicle, which contains the engine, the throttle device 10 is switched on or adjusted accordingly. In the case of an internal combustion engine, which is installed in a motor vehicle, in particular a commercial vehicle such as a truck or bus, this regulation of braking power can be integrated into an electronically controlled braking strategy which optimally coordinates the use of all the brakes available in the vehicle (service brakes, retarder, engine brake) ,

Below, the interaction of the parts of the engine dust brake device according to the invention during an engine braking operation is discussed in more detail.

When an engine braking operation is initiated, the throttle device 10 is brought by commands of the control and / or regulating unit 70 in a closed position, so that upstream of the throttle device 10 results in a pressure increase with corresponding exhaust back pressure. The emerging during the expulsion of exhaust gas adjacent cylinders 1 pressure waves are superimposed on the stationary exhaust back pressure and cause due to the positive pressure difference an intermediate opening of each of an internal engine brake device 11 associated exhaust valve 2 - see phase A1 in the diagram of Fig. 9 -, which occurs at the end of the first cycle (intake stroke). In this taking place independently of the camshaft control exhaust valve intermediate opening is intervened according to the invention control technology automatically during braking operation. In this case, the after opening under the action of its closing spring 23 again tends to close exhaust valve 2 is forcibly intercepted by the associated motor-internal braking device 11 and then held by means of this over the entire compression stroke and expansion stroke in partially open intercept position - see phase A2 in the diagram according to Fig. 9 , The following processes take place in the engine-internal brake device.

At the beginning of the first stroke (intake stroke), the exhaust valve 2 is in the closed position A. The control piston 30 of the engine-internal braking device 11 is set in its blind bore 31 to stop and acts as a mechanical buffer, whereby he through the closed exhaust valve 2 in this retracted position is pressed.

Towards the end of the first cycle, the exhaust gas back pressure-induced intermediate opening of the exhaust valve 2 takes place with a valve lift A → B, which occurs at the end of the phase A1 (see diagram Fig. 9 ) is achieved. Following the opening movement of the inter-opening exhaust valve 2, the control piston 30 is tracked by the oil pressure in the control pressure chamber 33 and the force of the possibly existing control compression spring 32 and extended into its stop-related extreme intercept position. Einher goes with this extension of the control piston 30, an increase in volume of the control pressure chamber 33 and its immediate filling with pressure oil through the oil supply channels 34, 35, after complete filling of the control pressure chamber 33 - because of the blocking check valve 36 and the shut-off by the counter-holder 40 discharge channel 37 - the control piston 30 is hydraulically locked in its extended Abfangstellung in the valve bridge 20. At the intermediate opening the exhaust valve 2 is ahead of the stroke of the control piston 30 with a larger stroke. During the transition from phase A1 to phase A2 (see diagram Fig. 9 ), the exhaust valve 2 moves back in the closing direction, but is then intercepted after a short return path B → C at the beginning of the second clock (compression stroke) by the hydraulically locked in the valve bridge control piston 30. This intercept position is maintained during the entire phase A2, ie over the entire remaining second clock (compression stroke) and the following third stroke (expansion stroke).

Only when, at the end of the 3rd stroke (expansion stroke), the camshaft-side control of the exhaust valve 2 on the associated control cam on the camshaft, possibly the push rod 12, the rocker arm 13 and the valve bridge 20 is effective again, this previous hydraulic interlocking is canceled of the control piston 30, because as soon as the valve bridge 20 is moved in the direction "open outlet valve", it lifts off the counter-holder 40. As a result, the discharge channel 37 is released and pressure oil can flow through this now from the hydraulically no longer locked control pressure chamber 33 in the region of the cylinder cover 7, which also pressed by the action of the closing spring 23 in the closing direction moved exhaust valve 2 in the direction of its retracted home position Control piston 30 is supported.

As soon as the control piston 30 is pushed back fully into the blind hole 31 inside the valve bridge, it acts again only as a purely mechanical buffer on the valve bridge 20, via which in phase A3 (see diagram Fig. 9 ) during the 4th cycle (exhaust stroke) during engine braking the opening of the exhaust valve 2 then - synchronous to the second exhaust valve 3 - to the full Auslaßventilhub D, whose or holding and re-closing controlled by the corresponding cam on the camshaft and on the Rocker arm 13 takes place. At the end of the 4th stroke (Ausschubtakt), the valve bridge 20 takes during the engine braking again in Fig. 1 and 2 shown position from which runs out the next in the same way as previously described running brake cycle.

Below is some information on the theoretical background of the engine dust brake device according to the invention:

As already mentioned, the intermediate opening of an exhaust valve 2 during an engine braking phase is caused by exhaust pressure waves of adjacent cylinders 1, which in FIG the exhaust tract 9 open. To calculate the movement sequence of the exhaust valve 2 during the intermediate opening, the following equation of motion is written: $$\mathrm{mv}\mathrm{•}\ddot{\mathrm{y}}\mathrm{+}\mathrm{d}\mathrm{•}\stackrel{\mathrm{\text{'}}}{\mathrm{y}}\mathrm{+}\left(\mathrm{c}\mathrm{+}\mathrm{f}\right)\mathrm{•}\mathrm{y}\mathrm{+}\mathrm{F}\mathrm{1}\mathrm{-}\mathrm{Fk}\mathrm{-}\mathrm{Ava}\mathrm{•}\mathrm{pa}\mathrm{+}\mathrm{Avz}\mathrm{•}\mathrm{pz}\mathrm{=}\mathrm{0}$$

mv =

reduzierte Ventilmasse (Masse, die am Zwischenöffnen beteiligt ist)

ÿ =

Ventilbeschleunigung

d =

geschwindigkeitsproportionale Dämpfung des Auslassventils 2

y =

Ventilgeschwindigkeit

c =

Federrate der Schließfeder 23

f =

Federrate der optionalen Steuerdruckfeder 32

y =

Ventilhub

F1 =

Vorspannkraft der Schließfeder 23

Fk =

am Steuerkolben 30 wirksame Vorspannkraft (Öldruck + evt. Steuerdruckfeder 32)

Ava =

Auspuffseitige Ventilfläche

pa =

Druck im Abgastrakt 61

Avz =

Zylinderseitige Ventilfläche

pz =

Druck im Zylinder 1

pl =

Druck im Ansaugrohr (Ladedruck)

In this case, based on the considered exhaust valve 2:

mv =

reduced valve mass (mass involved in intermediate opening)

ÿ =

valve acceleration

d =

speed proportional damping of the exhaust valve 2

y =

valve speed

c =

Spring rate of the closing spring 23

f =

Spring rate of the optional control spring 32

y =

valve

F1 =

Biasing force of the closing spring 23

Fk =

on the control piston 30 effective biasing force (oil pressure + evt. control pressure spring 32)

Ava =

Exhaust-side valve surface

pa =

Pressure in the exhaust tract 61

Avz =

Cylinder-side valve surface

pz =

Pressure in cylinder 1

pl =

Pressure in intake manifold (boost pressure)

From this, the biasing force F1 of the closing spring 23 of the outlet valve 2 and the control pressure spring 32 is calculated as follows: $$\mathrm{Ava}\mathrm{•}\mathrm{pa}\mathrm{-}\mathrm{Avz}\mathrm{•}\mathrm{pz}\mathrm{-}\mathrm{mv}\mathrm{•}\ddot{\mathrm{y}}\mathrm{-}\mathrm{d}\mathrm{•}\stackrel{\mathrm{\text{'}}}{\mathrm{y}}\mathrm{-}\left(\mathrm{c}\mathrm{+}\mathrm{f}\right)\mathrm{•}\mathrm{y}\mathrm{=}\mathrm{F}\mathrm{1}\mathrm{-}\mathrm{Fk}$$

The biasing force F1 of the closing spring 23 of the exhaust valve 2 is within the allowable design range, which results from the Ventiltriebdynamik calculation, to interpret the functioning of the engine dust brake device so that the exhaust valve 2 safe on the basis of the given when the throttle device 10 in the accumulated exhaust gas back pressure between open. But F1 should not be too low, otherwise the air flow and the exhaust gas back pressure will drop, whereby the internal cooling of the internal combustion engine in braking mode and the braking power would be lower.

Since at the beginning of the intermediate opening the outlet valve 2, the valve lift y and thus also ẏ and ÿ are equal to 0, the equation reduces at this time to: $$\mathrm{Ava}\mathrm{•}\mathrm{pa}\mathrm{-}\mathrm{Avz}\mathrm{•}\mathrm{pz}\mathrm{=}\mathrm{F}\mathrm{1}\mathrm{-}\mathrm{Fk}$$

Since it can be approximately assumed that the cylinder-side valve surface of the outlet valve 2 corresponds approximately to the circular area with the theoretical valve seat diameter (Avm) and the shaft cross-section is approximately 4% of Avm in conventional exhaust valves, the equation can be approximated as follows: $$\mathrm{avm}\mathrm{•}\left(\mathrm{pa}\mathrm{•}\mathrm{0}\mathrm{.}\mathrm{96}\mathrm{-}\mathrm{pz}\right)\mathrm{=}\mathrm{F}\mathrm{1}\mathrm{-}\mathrm{Fk}$$

Since the exhaust gas back pressure-related intermediate opening of the exhaust valve 2 takes place at the end of the intake stroke, the boost pressure (usually equal to the atmospheric pressure during braking operation) can be used for pz.

wobei K = 1,2 ± 0,2 With pa as the desired exhaust back pressure in the lower speed range and a factor K for the dynamic pressure increase (the exhaust valve 2 is to be pressed only by pressure waves generated by adjacent cylinders), the biasing force F1 of the closing spring 23 of the exhaust valve 2 is therefore designed as follows: $$\mathrm{F}\mathrm{1}=\mathrm{avm}\mathrm{•}\left(\mathrm{K}\mathrm{•}\mathrm{pa}\mathrm{•}\mathrm{0}\mathrm{.}\mathrm{96}\mathrm{-}\mathrm{pl}\right)+\mathrm{Fk}$$

where K = 1.2 ± 0.2

With the engine dust brake device according to the invention can thus with comparatively cheap and easy to implement means even in an internal combustion engine, which has two exhaust valves per cylinder, achieve a very high engine braking performance in engine braking.

LIST OF REFERENCE NUMBERS

1

cylinder

2

outlet valve

3

outlet valve

4

Combustion chamber of 1

5

Piston of 1

6

cylinder head

7

cylinder cover

8th

exhaust ports

9

exhaust tract

10

throttling device

11

engine-internal braking device

12

pushrod

13

rocker arm

14

bearing block

15

bearing axle

16

Slide bearing on 15

17

Mother at 18

18

Bolt on 13

19

Support calotte on 18

20

valve bridge

21

Shank of 2

22

Shaft of 3

23

Closing spring of 2

24

Closing spring of 3

25

Cylinder head surface for 23

26

Cylinder head surface for 24

27

Spring plate on 2

28

Spring plate on 3

29

Bottom of 20 for 3

30

Spool of 11

31

Blind hole for 30 in 20

32

Control pressure spring

33

Control pressure chamber

34

Oil supply channel in 13

35

Oil supply channel in 20

36

check valve

37

relief channel

38

Top of 20

39

Outlet opening of 37

40

backstop

41

blind

42

Stop above, retracted spool

43

Stop below, extended control piston

44

Blind hole in 30 ( Fig. 3 to 5 )

45

Bottom of 44 ( Fig. 3 to 5 )

46

Bottom of 31

47

Tenon at 30 ( Fig. 6 to 8 )

48

rear face on 47 ( Fig. 6 to 8 )

49

Shoulder area at 30

50

cross pin

51

Cross hole in 20 for 50

52

Dent on 30

53

Locknut of 40

54

stud

55

Ball of 36

56

conical transition surface

57

Section of 35

58

Section of 35

59

Stop in 58

60

cross hole

61

lockable section of 9

62

Axis of 10

63

servomotor

64

Compressed air supply system

65

Compressed air line

66

line part

67

Isolation / gate valve

68

switching element

69

control line

70

Control and / or regulating unit

71

pressure sensor

72

temperature sensor

73

signal lines

74

signal lines

75

signal lines

76

switching line

77

switching line

Claims (19)

1. Exhaust braking device for a 4-stroke internal piston combustion engine that, for each cylinder (1) has at least one intake valve and at least one exhaust valve (2), which exhaust valve is connected to an exhaust train (9) and impinged upon in the closing direction by a closing spring (23, 24) and can be indirectly activated by a camshaft, with a throttle device (10) being installed in the exhaust train (9) and able to be activated for engine braking in such a way that upstream of the throttle device, in the pent-up exhaust gas, exhaust gas backpressure builds up that becomes effective for engine braking inside the engine in conjunction with a special braking device (11) that has a control piston (30) on which the shaft (21) of the exhaust valve (2) is supported and that is taken up and guided in an axially movable manner in a blind drilled hole of a valve train section as well as being pressed in the direction of the exhaust valve (2) from a control pressure chamber (33) and supplied with pressure oil possibly by means of an additional control pressure spring (32), which control pressure chamber (33) is connected to a pressure oil supply and can be cyclically discharged, with the preload force of the closing springs (23) assigned to the exhaust valve (2) additionally being measured in such a way that, during engine braking when the throttle device (10) is in the throttle position, as a result of the exhaust gas backpressure arising in the pent-up exhaust gas in connection with the pressure pulsations acting therein, interim opening of the exhaust valve (2) is attained, into which interim opening it is possible to automatically intervene in terms of control during each 4-stroke engine cycle with the in-engine braking device (11) in such a way that the exhaust valve (2) that inclines to close after the interim opening at the beginning of the 2^nd stroke is intercepted by the control piston (30) that is moving up due to impingement by the oil pressure, and said exhaust valve is prevented from closing during the 2^nd and 3^rd stroke as well as being kept partially open until its camshaft-controlled opening that takes place at the beginning of the 4^th stroke, characterised in that, for each cylinder (1), two exhaust valves (2, 3) connected to the exhaust train (9) are provided that can be activated either directly or indirectly via a valve bridge (20) and a rocker arm (13) that acts on the valve bridge and can be controlled either directly or indirectly via a push rod (12) from a camshaft, with the in-engine braking device (11) for each cylinder (1) being assigned to only one (2) of the two exhaust valves (2, 3), whereas the other exhaust valve (3) acts conventionally, in that the control piston (30) of the in-engine braking device (11) on which the shaft (21) of the exhaust valve (2) is supported is taken up and guided in an axially movable manner in a blind drilled hole (31) of the valve bridge (20) and pressed therein from a control pressure chamber (33) supplied with pressure oil as well as the possibly provided additional control pressure spring (32) in the direction of the shaft (21) of the exhaust valve (2), in that the pressure oil is supplied to the control pressure chamber (33) via a channel (35) that communicates with a rocker arm-internal channel (34) and is formed inside the valve bridge (20), into which channel (35) a check valve (36) that is only permeable in the direction of the control pressure chamber (33) is installed, in that a discharge channel (37) branches off from the control pressure chamber (33), which discharge channel opens out at the top (38) of the valve bridge (20) and its outlet opening (39) can be closed by a brace (40) that simultaneously forms a stop for the valve bridge (20) and can be uncovered for pressure release of the control pressure chamber (33) after the valve bridge (20) is lifted, in that the cross-section of the oil supply channels (34, 35) and the pressure of the oil supplied to the control pressure chamber (33) are coordinated with each other in such a way that, during interim opening of the exhaust valve (2), the control pressure chamber (33) that is enlarged in terms of volume due to the re-pressing control piston (30) can be almost completely filled with pressure oil and so the exhaust valve (2) is sure to be kept in an intercepted partially open position around the end of the interim opening stroke, and in that the exhaust gas backpressure P2 that reaches its maximum when the throttle device (10) is in the closed position can be lowered if necessary by means of controlled and/or regulated opening of the throttle device (10) in order to effect a reduction of the exhaust brake power and/or the temperature of in-engine components.
2. Exhaust braking device according to claim 1, characterised in that the control piston (30) of the in-engine braking device (11) is movable with lift limitation in the valve bridge-internal blind drilled hole (31) with low leakage between two stops (42, 43).
3. Exhaust braking device according to claim 2, characterised in that the upper stop (42) that defines the retracted basic position of the control piston (30) is formed by a shoulder area at the transition point between two sections of different diameter of the blind drilled hole (31), with the section with the larger diameter taking up the control piston (30) and the section with the smaller diameter forming the control pressure chamber (33) and taking up the control pressure spring (32).
4. Exhaust braking device according to claim 2, characterised in that the upper stop (42) that defines the retracted basic position of the control piston (30) is formed by the base (46) of the blind drilled hole (31) in the valve bridge (20) that defines the control pressure chamber (33) and takes up the control pressure spring (32), with a central journal (47) being arranged on the back of the control piston (30), with the rear face (48) of which journal the control piston (30) rests on the base (46) of the blind drilled hole (31), from which the discharge hole (37) also branches off, with the result that the journal (47) also fulfils that additional function, namely that the ejection of pressure oil via the discharge channel (37) that follows a pressure release of the control pressure chamber (33) in every 4^th engine stroke immediately after the start of the camshaft-controlled opening stroke movement of the valve bridge (20) and the associated lifting thereof by the brace (40) is limited in terms of quantity because the discharge channel (37) is closed again by the journal (47) of the control piston (30) that immediately returns to its basic position, as a result of which the oil loss in the control pressure chamber (33) can be limited and it can be ensured that the oil pressure therein remains high.
5. Exhaust braking device according to claim 2, characterised in that the lower stop (43) of the control piston (30) that defines the furthest extended position is realised by a transversal pin (50) that is pressed into a transversal drilled hole (51) in the valve bridge (20), also projects laterally into the narrow cross-section of the blind drilled hole (31) and thus engages with an outer recess (52) on the control piston (30), the upper limiting wall of which limits the thrusting stroke of the control piston (30) as a stop (43).
6. Exhaust braking device according to claim 1, characterised in that the control piston (30) has a blind hole (41) at the front with which it overlaps the upper end of the shaft (21) of the associated exhaust valve (2) in the form of a cap with play.
7. Exhaust braking device according to claim 1, characterised in that the control pressure spring (32) is supported at one end on the control piston (30) on the base (45) of a rear blind hole (44) and at the other end on the base (46) of the blind drilled hole (31) that takes up the control piston (30).
8. Exhaust braking device according to claim 4, characterised in that the control pressure spring (32) is centred by the central journal (47) on the control piston (30) and is supported on a ring-shaped shoulder area (49) on the control piston (30), and supported on the other side on the base (46) of the blind drilled hole (31) that takes up the control piston (30).
9. Exhaust braking device according to claim 1, characterised in that the brace (40) for the valve bridge (20) is formed by a stud bolt (54) that is fixed in the cylinder cover (7) e.g. by a lock nut (53), and adjustable in terms of its stop position.
10. Exhaust braking device according to claim 1, characterised in that the cross-section of the oil supply channel (34) in the rocker arm (13) is equal to or greater than that of the connecting oil supply channel (35) in the valve bridge (20).
11. Exhaust braking device according to claim 1, characterised in that the check valve (36) has a ball (55) as a control mechanism and the associated valve seat is formed by a conical interface (56) between two oil supply channels of different diameter (57, 58), with the ball (55) being arranged in the oil supply channel section with the larger diameter (58) and its opening stroke being limited there by a stop (59).
12. Exhaust braking device according to claim 1, characterised in that the stop (59) that limits the opening stroke of the check valve ball (55) is formed by a stop pin that transversally extends through the oil supply channel section (58) and is pressed into a cross hole (60) in the valve bridge (20).
13. Exhaust braking device according to claims 10 and 11, characterised in that the smallest cross section of the oil supply channel (35) is present inside the valve bridge (20) in the area of the check valve (36) in the area of the annular gap around its ball (55) in the oil supply channel section (58).
14. Exhaust braking device according to claim 1, characterised in that the discharge channel (37) is formed by a throttle hole that leads coaxially from the base (46) of the blind drilled hole (31) to the top (38) of the valve bridge (20), the diameter of which throttle bore is much smaller than the smallest cross section of the oil supply channel (35) in the valve bridge (20).
15. Exhaust braking device according to claim 1, characterised in that the effective preload force F1 of the valve spring (23) of the exhaust valve (2) is greater than the effective preload force of the control pressure spring (32) that impacts on the outlet valve via the control piston (30).
16. Exhaust braking device according to claim 1, characterised in that the components of the in-engine braking device (11) and the oil pressure of the pressure oil supplied to the control pressure chamber (33) are designed in such a way that, during engine braking, after its interim opening effected by exhaust gas backpressure, the exhaust valve (2) can be intercepted and held in a position C, of which the distance from the closed position of the exhaust valve (2) is around 1/5 to 1/20 of the full exhaust valve opening stroke (A → D).
17. Exhaust braking device according to claim 1, characterised in that the throttle device (10) is arranged in the exhaust train (9) of the internal combustion engine in front of the turbine of an exhaust gas turbocharger.
18. Exhaust braking device according to claim 1 or 17, characterised in that the volume of the section (61) of the exhaust train (9) that can be shut off by means of the throttle device (10) is selected to be as low as possible, i.e. the throttle device (10) is arranged as close as possible to the engine at the outlet of one or more combined exhaust manifolds and in front of the turbine of an exhaust gas turbocharger.
19. Exhaust braking device according to claim 1, characterised in that control of the throttle device (10) - in order to generate less braking power than the maximum possible during engine braking and/or to counter the overheating of in-engine components - is carried out in accordance with specified time intervals or measured component temperatures and/or on the basis of specifications from the operation of a vehicle that contains the engine and, in the case of a vehicle engine, can be integrated in an electronically regulated braking strategy that optimally coordinates the use of all brakes of the vehicle.

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