EP3184760A1 - Combustion engine with an engine brake with exhaust throttle and a decompression brake - Google Patents

Abstract

The invention relates to an internal combustion engine with at least one actuatable via a camshaft and a transmission valve per cylinder, wherein between the camshaft and the exhaust valve, a hydraulic valve clearance compensation element is arranged in the transmission device, and with an engine brake device comprising an engine exhaust brake for building an exhaust back pressure and a decompression brake with which at least one exhaust valve can be kept open at least in an engine braking phase, wherein the decompression brake is formed by the hydraulic valve clearance compensation element. The internal combustion engine further comprises a fuel injection control device configured to restart fuel injection after an end of an engine braking operation only after a predetermined delay time has elapsed, wherein the predetermined delay time is set to be greater than a closing timing of the exhaust valve Termination of engine braking operation.

Description

The invention relates to an internal combustion engine with at least one actuatable via a camshaft and a transmission valve per cylinder, wherein between the camshaft and the exhaust valve, a hydraulic valve clearance compensation element is arranged in the transmission device, and with an engine brake device comprising an engine exhaust brake for building an exhaust back pressure and a decompression brake with which at least one exhaust valve can be kept open at least in an engine braking phase, in particular also in a cam base circle phase.

From the publications EP 2 143 894 A1 and EP 2 143 896 A1 are known internal combustion engines with engine braking devices and valve clearance compensation mechanisms. In each case, a hydraulic valve clearance compensation mechanism is arranged in a valve bridge. The valve play compensation mechanism in this case has a piston adjacent to a pressure chamber, the pressure chamber being flow-connected via a check valve to a pressure line having a constant pressure. From the pressure chamber goes from a discharge line, which opens via a controllable relief valve in an oil outlet opening. In the valve bridge, a hydraulic additional valve control unit of the engine control device is further arranged, whose control pressure chamber is flow-connected to the pressure chamber of the controllable relief valve. The control pressure chamber communicates via an oil passage with a control pressure line in a counter-holder in flow connection, wherein a counter-holder via a stop piston contacts the valve bridge on a side facing away from the exhaust valves. Due to the numerous arranged in the valve bridge hydraulic piston and pressure lines a high processing and manufacturing effort of the valve bridge is required, the valve bridge is structurally weakened and thus must be designed correspondingly massive.

The engine brake devices described in the cited publications are each a hybrid form of an engine dust brake and a decompression brake, which is also referred to in particular as EVB (abbreviation for exhaust valve brake). The hydraulic additional valve control unit is mounted on one side in a two outlet valves simultaneously actuated valve bridge of the connection mechanism. The supply of the hydraulic additional valve control unit with oil by means of the already existing oil circuit of the respective internal combustion engine. In this type of engine braking devices The use of hydraulic lash adjusters requires additional measures to avoid uncontrolled inflation of the lash adjuster during engine braking operation, which could result in severe engine damage. In the EP 2 143 894 A1 and the EP 2 143 896 A1 This is done by the fact that the pressure chamber of the hydraulic valve clearance compensation device is depressurized via a controllable relief valve during engine braking operation. The well-known from the prior art arrangement with numerous oil holes and hydraulic piston in the valve bridge has the disadvantage that the valve bridge is structurally weakened and this must therefore be sized larger.

In the published patent application DE 10 2012 100 962 A1 is described a way to combine a hydraulic valve clearance compensation with a relief valve and thus simultaneously realize an engine brake device and a maintenance-free valve train only with a hydraulic valve clearance compensation. The decompression brake is thus formed by the hydraulic valve clearance compensation element. In order to avoid unwanted opening of the exhaust valve by the hydraulic valve clearance compensation after completion of the engine braking operation, in addition to the usual components of a hydraulic valve clearance compensation but the following components for a braking operation is required: a discharge line with controllable relief valve including control line and a hold-down with adjusting screw.

The function of this embodiment is similar to that in the published patent applications EP 2 143 894 A1 and the EP 2 143 896 A1 If the exhaust throttle valve is closed, the exhaust gas pressure in the exhaust duct before the compression (bottom dead center) increases so much that the exhaust valve is briefly pushed by the pressure wave of an adjacent cylinder. The hydraulic valve lash adjuster piston, which is constantly pressurized with engine oil pressure, prevents the valve from re-closing. There remains a small stroke, whereby the compression stroke in the engine already a part of the compressed air can flow out of the cylinder. After reaching top dead center, this opening is retained. The pressure on the then moving down piston is significantly reduced, the braking performance improves. By throttling the exhaust gas, both the upward and the downward movement of the engine piston can be used for braking. At the same time the relief valve is switched in the engine braking operation, which releases a relief hole to the high pressure chamber of the hydraulic valve clearance compensation. But this relief hole is initially still closed by the hold-down. At the beginning of the exhaust stroke, the relief hole is released by the rocker arm movement, the oil escapes and relieves the piston. Thus, the "extended" piston of the hydraulic valve clearance compensation can reset and close the exhaust valve again completely.

Also in this solution are thus still the aforementioned components in the form of relief line with controllable relief valve including control line and hold-down with adjusting screw in addition to a classic hydraulic valve clearance compensation for a braking operation necessary.

It is thus an object of the invention to provide in an improved manner both an engine brake and an automatic valve lash adjuster. The invention is in particular the object of a simpler, cost-saving and space-saving provision of an engine brake as well as an automatic valve clearance compensation basis.

These objects are achieved by a device having the features of the independent claim. Advantageous embodiments and applications of the invention are the subject matter of the dependent claims and are explained in more detail in the following description with partial reference to the figures.

According to general aspects of the invention, a device, in particular an internal combustion engine, with at least one actuatable via a camshaft and a mechanical transmission device exhaust valve per cylinder is provided. Here, a hydraulic valve clearance compensation element is arranged in the transmission device between the camshaft and the exhaust valve. The hydraulic valve clearance compensation element may comprise a piston adjacent to a pressure chamber and an oil pressure line opening into the pressure chamber via a check valve loaded by a spring.

Hydraulic valve clearance compensation elements (HVA) in internal combustion engines are known per se and serve, in particular, to compensate for the change over the operating length length dimensions of the charge exchange valves so that in the base circle phase of the valve-actuating cam secure valve closing is ensured. On the other hand, the cam lobe should be transferred without loss to the valve and thus converted into a valve lift. The operation of such hydraulic lash adjusters, which are arranged in the power flow of a valve control, in particular an internal combustion engine, is assumed to be known in the following.

The internal combustion engine further comprises an engine brake device, comprising a per se known engine dust brake for establishing an exhaust back pressure. The engine dust brake may include, for example, a controllable or controllable damper located in the exhaust tract. When closing the flap, the back pressure increases on the side lying against the flow direction and thus creates a braking effect in effect on the drive motor of the motor vehicle.

The engine braking device further comprises a decompression brake with which at least one exhaust valve can be kept open at least in an engine braking phase. The decompression brake is initiated by the gas-controlled over the increased exhaust back pressure at at least partially closed brake flap, in which a targeted "valve jump" of the exhaust valves is triggered.

A special feature lies in the fact that the decompression brake is formed here by the hydraulic valve clearance compensation element. In other words, the engine dust and the hydraulic lash adjuster are designed so that a sum of the force acting on the exhaust valve forces in the engine braking operation leads to an open position of the exhaust valve. For example, the forces acting on the exhaust valve include a valve spring force of the exhaust valve, a gas pressure force generated in the closing direction of the exhaust valve, a frictional force acting in the transmission device, and a gas pressure force of the exhaust gas pressure generated by the engine dust exhaust, an oil pressure force generated by the valve lash adjuster, and a spring force of the return spring of the hydraulic valve clearance compensation element, each acting in a direction opposite to the closing direction. Thus, in engine braking operation, a force exerted by the hydraulic lash adjuster acts on the exhaust valve together with the gas force of the exhaust pressure generated by the engine pawl and causes the exhaust valve to be forced to the open position and / or held in the open position. The hydraulic valve clearance compensation thus assumes a dual function. On the one hand it is realized in a conventional manner, a maintenance-free valve train, on the other hand it is used in engine braking for braking power increase, in which at least one exhaust valve can be kept open by means of the hydraulic valve train in an engine braking phase, so that the hydraulic Valve train also performs the function of a decompression brake. This saves components and costs.

A particular advantage of the invention is that the hydraulic valve clearance compensation can be designed as a classic or conventional hydraulic valve clearance compensation, d. H. may be provided in the form of a hydraulic lash adjuster having no additional means to allow accelerated pressure relief of the hydraulic valve lash adjuster pressure space to allow for faster closure of the exhaust valve upon completion of engine braking operation.

In order to ensure that the exhaust valves are fully closed again after the engine braking operation is completed prior to the fired operation, and thus to ensure a safe transition from engine braking operation to fired operation, the internal combustion engine includes a fuel injection control device that is configured to inject fuel to restart after an end of an engine braking operation only after a predetermined delay time has elapsed. Here, the predetermined delay time is set to be greater than a closing time of the exhaust valve after completion of the engine braking operation. The fired operation is thus not resumed immediately after an end of the engine braking operation, but initiated only after waiting for a delay time.

Under the closing time of the exhaust valve is understood the period between the opening of the engine dust exhaust, which corresponds to the end of the engine braking operation, and the closed position of the exhaust valve kept open by the hydraulic valve play compensation element in engine braking operation. The closing time can be measured experimentally on a test bench, for example.

The hydraulic lash adjuster is preferably configured such that a duration of the closing time is substantially equal to a leakage-related return action of the deflected piston of the hydraulic lash adjuster triggered at the end of the engine braking operation by a reduction in gas pressure of the exhaust pressure acting on the exhaust valve , This is the case, for example, if the hydraulic valve clearance compensation element has no additional means to allow an accelerated pressure relief of the pressure chamber of the hydraulic valve clearance compensation. In such a valve clearance compensation element, after eliminating the gas force of the exhaust gas pressure, the valve spring and the gas pressure from the Combustion chamber that the hydraulic valve clearance compensation element is pushed back into the starting position. When "pushing back" oil is squeezed out of the high pressure chamber through the leakage gap, which corresponds to an oil volume reduction in the high pressure chamber of the hydraulic valve clearance compensation.

According to this embodiment, substantially the decrease of the gas power generated by the engine dust brake and not a change in the oil force generated by the valve lash adjuster is essential for the return of the exhaust valve to the closed position upon completion of the engine braking operation and thus also for the value of the closing time. A duration of the closing time can thus essentially depend on a reduction in the gas pressure of the exhaust gas pressure acting on the exhaust valve when opening the engine dust brake at the end of the engine braking operation.

In accordance with a preferred embodiment, no relief line is provided which originates from a pressure chamber of the valve play compensation element and can be connected to a pressure sink via a controllable relief valve. A particularly advantageous variant of this embodiment further provides that no counter-holder is provided, which is designed to release an outlet opening of the discharge line only at the beginning of an exhaust stroke. In particular, no counter-holder is provided on which the transmission device rests in an end position on the preferably adjustable counter-holder. As a result, costs for these additional parts and the space required for it can be saved.

One possibility of the realization according to the invention, for example, provides that the delay time is in a range of 0.5 to 3 seconds, more preferably in a range of 1 to 2 seconds. Furthermore, the delay time can be stored in the control device or in a memory device used by the control device.

In a preferred embodiment, the mechanical transmission device comprises a valve bridge and a valve lever designed as a rocker arm or rocker arm, which is driven by the camshaft and acts on the exhaust valves via the valve bridge.

According to a preferred embodiment, a piston, a check valve and a spring of the hydraulic valve clearance compensation element between the valve lever and be arranged the valve bridge. Depending on the valve train construction, however, other installation locations or designs for the hydraulic valve clearance compensation are possible. For example, the hydraulic valve clearance compensation can be arranged between the push rod and the rocker arm, integrated in a bucket tappet or a valve tappet.

According to a further aspect, the invention further relates to a motor vehicle, in particular a commercial vehicle, with an internal combustion engine, as described in this document.

Figur 1

einen Ventiltrieb mit hydraulischem Ventilspielausgleich gemäß einer Ausführungsform der Erfindung;

Figur 2

eine Illustration der im Motorbremsbetrieb wirkenden Kräfte auf die Auslassventile des Ventiltriebs der Figur 1; und

Figur 3

eine Illustration des Übergangs von Motorbremsbetrieb zum befeuertem Betrieb gemäß einer Ausführungsform der Erfindung.

The preferred embodiments and features of the invention described above can be combined with one another as desired. Further details and advantages of the invention will be described below with reference to the accompanying drawings. Show it:

FIG. 1

a valve train with hydraulic valve clearance compensation according to an embodiment of the invention;

FIG. 2

an illustration of the forces acting in the engine braking operation forces on the exhaust valves of the valve train of FIG. 1 ; and

FIG. 3

an illustration of the transition from engine braking operation to fired operation according to an embodiment of the invention.

Identical or functionally equivalent elements are denoted by the same reference numerals in all figures.

FIG. 1 shows a valve train 11 with hydraulic lash adjuster 6 of an internal combustion engine according to an embodiment of the invention. The internal combustion engine comprises a 4-stroke reciprocating internal combustion engine, not shown, having at least one inlet valve (not shown) and two exhaust valves 1 per cylinder.

The intake and exhaust valves 1 are controlled by a (not shown) camshaft ago. The camshaft may be lower or upper with respect to the rocker arm 3. FIG. 1 corresponds to the version with overhead camshaft (not shown) in the area of the control of the two exhaust valves 1 of a cylinder. The rocker arm 3 is rotatably mounted on the cylinder head 7 on a bearing block 9 on a bearing axis with plain bearings. The rocker arm 3 in turn acts on a valve bridge 4 a. This valve bridge 4 is used to control the two axially parallel to each other arranged exhaust valves 1 of a cylinder (not shown) of the internal combustion engine (not shown). Each of the exhaust valves 1 is mounted with its shaft 1 a in the cylinder head 7 (shown highly schematically) axially movable and by a closing spring (return spring) 5, the one end is supported on a cylinder head surface 7a and the other to a mounted on the Auslassventilschaft 1 a spring plate 1 b, with a certain biasing force F3 (see also FIG. 2 ) acted in the closing direction C. Each of the two closing springs 5 can be realized either by only one coil spring or two mutually coaxial coil springs.

Between the rocker arm 3 and the valve bridge 4, a hydraulic valve clearance compensation element 6 is arranged, so that the rocker arm acts on the valve bridge 4 [EC (1) and thus on the exhaust valves 1 via the hydraulic valve play compensation element 6 and a ball joint hinged support dome 8.

The executed in a conventional manner hydraulic lash adjuster 6 has a piston adjacent to a pressure chamber and in the pressure chamber via a loaded spring loaded by a check valve oil pressure line (each not shown). The piston, the check valve and the spring of the hydraulic valve clearance compensation element 6 are arranged between the valve lever 3 and the valve bridge 4.

The hydraulic valve clearance compensation element 6 serves in particular to compensate the wear (valve works into the valve seat) over the engine service life, so that reliable valve closure is ensured in the base circle phase of the cam actuating the exhaust valve 1.

The exhaust ports 2 of the cylinder open into an exhaust tract of the internal combustion engine, in which the engine as possible in a conventional manner, an engine dust brake is built to build up an exhaust back pressure. This can be formed by a throttle valve or a poppet valve or a slider. In most cases, a throttle is used. The engine dust brake, including its control and / or regulating members forms part of the engine braking device and is used during engine braking operations for at least partial shut-off of the exhaust gas tract and thereby an upstream impingement of the exhaust gas. Another part of the engine brake device is a decompression brake for engine brake power increase, which is formed in the present case by the hydraulic valve clearance compensation element 6.

• Wird die Abgasdrosselklappe für einen Motorbremsbetrieb geschlossen, baut sich eine auf das Auslassventil 1 wirkende Gaskraft F5 des Abgasdruckes auf. Hierbei steigt der Abgasdruck im Auslasskanal vor der Verdichtung, insbesondere im Ansaugtakt vor dem unterem Totpunkt und im unteren Totpunkt, so stark an, dass das Auslassventil 1 durch die Druckwelle eines benachbarten Zylinders kurzzeitig aufgedrückt wird, wodurch in der Nockengrundkreisphase ein Spalt zwischen Auslassventil 1 und dem Ventilsitzring gebildet wird bzw. eine Öffnung zum Auslasskanal 2 entsteht (sogenanntes Ventilspringen oder Ventilflattern). Unterstützt wird das Aufdrücken des Ventils noch durch eine erste Kraftkomponente F1, die von dem hydraulischen Ventilspielausgleichselements 6 infolge des Öldruckes ausgeht, und durch eine zweite Kraftkomponente F2, die von dem hydraulischen Ventilspielausgleichselement 6 infolge der Rückstellfeder ausgeht.

The function of the hydraulic valve clearance compensation element 6 for engine brake power increase can be described as follows:

• When the exhaust throttle valve is closed for an engine braking operation, a gas force F5 of the exhaust gas pressure acting on the exhaust valve 1 builds up. In this case, the exhaust gas pressure in the outlet channel before compression, in particular in the intake stroke before bottom dead center and bottom dead center, increases so much that the exhaust valve 1 is briefly pressed by the pressure wave of an adjacent cylinder, whereby in the cam base circle phase, a gap between exhaust valve 1 and the valve seat ring is formed or an opening to the outlet channel 2 is formed (so-called valve jump or valve flutter). The pressing of the valve is supported by a first force component F1, which starts from the hydraulic valve clearance compensation element 6 due to the oil pressure, and by a second force component F2, which emanates from the hydraulic valve clearance compensation element 6 due to the return spring.

The pressing of the exhaust valve 1 by the two described effects leads to a relief of the hydraulic valve clearance compensation element 6 and thus due to the constant applied oil pressure and the spring force of the return spring of the hydraulic valve clearance compensation element for readjusting the hydraulic valve clearance compensation element 6. The piston of the hydraulic valve clearance compensation element thus extends. The re-closing of the valve is prevented.

There remains a small gap of size V1 between exhaust valve 1 and valve seat ring, hereinafter referred to as gap, whereby the compression stroke in the engine already a part of the compressed air can flow out of the cylinder. The pressure on the then moving back down piston (power stroke) is significantly reduced. This improves the engine braking performance. By throttling the exhaust gas, both the upward and the downward movement of the engine piston can be used for braking.

1. (a) dem Abgasdruck, der die auf das Auslassventil 1 wirkenden Gaskraft F5 erzeugt.
2. (b) dem Gasdruck von der Brennraumseite, der die Gaskraft F6 erzeugt, die in Schließrichtung C wirkt,
3. (c) dem Öldruck, der am hydraulischen Ventilspielausgleich anliegt, der die Öldruckkraft F1 erzeugt;
4. (d) der Federkraft F2 der Rückstellfeder des hydraulischen Ventilspielausgleichs;
5. (e) der Ventilfederkraft F3 der Schließfedern 5;
6. (f) der Reibung im Ventiltrieb, die eine Reibungskraft F4 erzeugt.

The gap, which is set between exhaust valve 1 and its valve seat ring during engine braking operation, depends on the following influencing variables:

1. (a) the exhaust pressure that generates the gas force F5 acting on the exhaust valve 1.
2. (b) the gas pressure from the combustion chamber side producing the gas force F6 acting in the closing direction C,
3. (c) the oil pressure applied to the hydraulic lash adjuster that generates the oil pressure force F1;
4. (d) the spring force F2 of the return spring of the hydraulic valve clearance compensation;
5. (e) the valve spring force F3 of the closing springs 5;
6. (f) the friction in the valvetrain which generates a friction force F4.

The force acting on the exhaust valve 1 forces F1 to F6 are in the Figures 2 and 3 shown. The engine exhaust brake generated force F5 and the valve lash adjuster F1 and F2 both act in the same direction O, that is, in a direction toward the open position of the exhaust valve 1. The spring force F3 of the closing spring 5 (return spring) of the exhaust valve and the gas force F6, which is generated by the combustion chamber pressure in the cylinder, however, act in the closing direction C of the exhaust valve.

By adjusting these factors or forces, the maximum gap size and the engine speed, from which it comes to the occurrence of a gap between each of the exhaust valves 1 and the associated valve seat rings influence. The two exhaust valves 1 thus both jump and are kept open by the hydraulic valve clearance compensation element 6, which communicates with the two exhaust valves 1 via the valve bridge 4.

An increase in the gap between exhaust valve 1 and valve seat ring or a shift in the occurrence of the gap towards lower engine speeds can be achieved by at least one of the following measures: increase exhaust pressure, reduce gas pressure from the combustion chamber side, increase oil pressure, which is applied to the hydraulic valve clearance compensation; Increase the spring force of the return spring of the hydraulic valve lash adjuster; Reduce valve spring force or reduce friction in the valve train.

A reduction in the gap or a shift in the occurrence of the gap towards greater engine speeds can be achieved in an analogous manner by at least one of the following measures: reduce exhaust pressure, increase gas pressure from the combustion chamber side, reduce oil pressure applied to the hydraulic valve clearance compensation; Reduce the spring force of the return spring of the hydraulic valve lash adjuster; Increase valve spring force or increase friction in the valve train.

In this way, the set in the engine braking operation on the valve clearance compensation element 6 gap size and thus the desired increase in the engine braking power can be adjusted. The gap always approaches a maximum value at a certain engine speed at. The maximum value of the gap adjusts itself with an equilibrium of forces of the influencing variables listed above. With increasing engine speed, this maximum value increases.

Based on FIG. 3 the operation of the engine braking device is explained and in particular a transition from an engine braking operation to the subsequent fired operation explained.

In the FIG. 3 with "I.", "II." and "III." designated states of the valve train 11 respectively show the state of the valve train, in particular the exhaust valve position in the cam base circle phase, ie, the valve lever 3 is not deflected. In this context, the term "cam base circle phase" should be understood as meaning, in particular, an angular range of the cam unit in which cam contours of all partial cams of the cam unit occupy a common base circle level.

The state I. corresponds to the state of the valve train 11 during an engine braking phase (period before t1). The state II. Corresponds to the state of the valve train 11 during a transitional phase t1 to t2, during which a towing operation takes place after the end of the engine braking operation, d. H. no injection takes place. Condition III. corresponds to the state of the valve train 11 during a fired operation, which begins after a deceleration phase of the duration .DELTA.t at time t2.

A particular challenge is the transition from engine braking operation to fired engine operation. It should be ensured that the exhaust valves 1 are fully closed again before the engine operation is fired in order to prevent increased valve / seat ring wear or overloading of the valve train by opening the exhaust valves 1 in the fired operation.

In braking mode, after a certain time, a maximum value V1 for the gap between the exhaust valve 1 and the valve seat ring is established, the maximum value being dependent on the engine speed. In this state, the piston of the hydraulic lash adjuster 6 is in the extended state P1, indicated by the solid line P1. The starting position is shown by the dotted line P3.

In this state, the forces of oil pressure force F1, return spring force F2 of the hydraulic lash adjuster, gas force F5 of the exhaust gas pressure, valve spring force F3, friction force F4, and the gas force F6 generated by cylinder space pressure are in equilibrium.

This corresponds to the state I. of FIG. 3 (Period before t1). Immediately after the end of the engine braking operation at time t1, at which the exhaust flap of the engine dust brake is opened, the exhaust valve 1 is initially still open due to the deflected piston of the hydraulic valve clearance compensation element 6.

By opening the exhaust valve at the time t1, however, the gas force F5 of the exhaust gas pressure is abruptly greatly reduced and thus disturbs the balance of power described. The gas force F6 from the cylinder chamber and significantly the valve spring force F3 now cause the piston of the hydraulic valve lash adjuster element 6 to return again in the direction of the starting position and the exhaust valves 1 to be completely closed again.

This closing time of the exhaust valve 1 after completion of the engine braking operation can be previously measured experimentally on a test bench.

One way to ensure complete closure of the exhaust valves 1 prior to engine fired operation is retarded fuel re-injection using appropriate engine control unit specifications.

To this end, the engine control unit 10 which controls the fuel injection is configured to restart fuel injection after an end of an engine braking operation (time t1) only after elapse of a predetermined delay time Δt, the predetermined delay time Δt being set to be larger by a distance value is as a predetermined closing time of the exhaust valve 1 after completion of the engine braking operation. In the period t1 to t2, which is in FIG. 3 corresponds to the state II. The valve gear, the gap between the exhaust valve 1 and valve seat ring thus has an increasingly smaller size V2 and finally goes back to the value V3 = zero. Accordingly, the piston of the hydraulic valve clearance compensation element 6 retracts. The exhaust valve is closed again before the time t2. In the time between t1 (end of engine braking operation) and t2 = t1 + .DELTA.t thus takes place a towing operation and thus no injection. This ensures that the piston of the hydraulic valve lash adjuster 6 has enough time to retract or the exhaust valve 1 has enough time to close. In state II. The FIG. 3 an intermediate position P2 of the piston of the hydraulic valve clearance compensation element 6 is shown, in which this almost retracted back to the starting position P3.

At time t2, the piston of the hydraulic valve clearance compensation element 6 is again in the starting position P3. The gap size V3 is zero, d. h., The exhaust valve 6 is closed again. At time t2, the engine control unit 10 then restarts the fired operation.

According to this embodiment can thus be avoided to combine a hydraulic valve clearance compensation element with a discharge line with controllable relief valve including control line and a hold-down with adjusting screw. Instead, the transition from engine braking operation to fired operation is controlled so that the fired operation begins after completion of the engine braking operation only after a delay time selected to allow the exhaust valve sufficient time to move to the closed position.

Although the invention has been described with reference to particular embodiments, it will be apparent to those skilled in the art that various changes may be made and equivalents may be substituted for without departing from the scope of the invention. In addition, many modifications can be made without leaving the associated area. Accordingly, the invention should not be limited to the disclosed embodiments, but should include all embodiments which fall within the scope of the appended claims. In particular, the invention also claims protection of the subject matter and the features of the subclaims independently of the claims referred to.

LIST OF REFERENCE NUMBERS

1

outlet valve

1a

shaft

1b

spring plate

2

exhaust port

3

rocker arm

4

valve bridge

5

closing spring

6

Lash adjuster

7

cylinder head

7a

Cylinder head surface

8th

Stützkalotte

9

bearing block

10

Control device, for. B. engine control unit

11

valve train

t1

End of engine braking operation

t2

Start-fired operation

.delta.t

Delay Time

F1

Oil pressure force of the hydraulic valve clearance compensation element

F2

Spring force of the hydraulic valve clearance compensation element

F3

Spring force of the closing spring

F4

frictional force

F5

Gas power through engine dust brake

F6

Gas power by combustion chamber pressure in the cylinder

V1, V2, V3

Gap size between exhaust valve and valve seat ring

Claims (10)

Internal combustion engine having at least one exhaust valve (1) per cylinder operable via a camshaft and a transmission device (3, 4), wherein a hydraulic valve clearance compensation element (6) is arranged in the transmission device (3, 4) between the camshaft and the exhaust valve (1), and with an engine brake device, comprising an engine dust brake for building up an exhaust back pressure and a decompression brake with which at least one exhaust valve (1) can be kept open at least in an engine braking phase,
wherein the decompression brake is formed by the hydraulic valve clearance compensation element (6),
characterized,
in that the internal combustion engine comprises a control unit (10) for controlling fuel injection, which is designed to restart fuel injection after an end of an engine braking operation only after a predetermined delay time (Δt) has elapsed, the predetermined delay time (Δt) being set such that it is greater than a closing time of the exhaust valve (1) after completion of the engine braking operation. Internal combustion engine according to claim 1, characterized in that the hydraulic valve clearance compensation element (6) comprises a piston adjacent to a pressure chamber and an opening into the pressure chamber via a loaded by a spring check valve oil pressure line. Internal combustion engine according to claim 2, characterized in that none of the pressure chamber of the valve clearance compensation element (6) outgoing, via a controllable relief valve with a pressure sink connectable relief line is provided. Internal combustion engine according to claim 3, characterized in that no counter-holder, which is designed to release an outlet opening of the discharge line only at the beginning of an exhaust stroke, is provided. Internal combustion engine according to one of claims 2 to 4, characterized in that the hydraulic valve clearance compensation element (6) is designed so that a duration of the closing time substantially corresponds to a duration, which is a leakage-induced return operation of the deflected piston of the hydraulic valve clearance compensation element (6) which is triggered at the end of the engine braking operation by reducing a gas force (F5) of the exhaust gas pressure acting on the exhaust valve (1). Internal combustion engine according to one of the preceding claims, characterized in that the delay time (Δt) is in a range of 0.5 to 3 seconds, more preferably in a range of 1 to 2 seconds. Internal combustion engine according to one of the preceding claims, characterized in that the delay time (At) is stored in the control device (10) or in a memory device used by the control device. Internal combustion engine according to one of the preceding claims, characterized in that the transmission device comprises: (a) a valve bridge (4); and (B) designed as a rocker arm (3) or drag lever valve lever which is driven by the camshaft and acts on the valve bridge (4) on the exhaust valves. Internal combustion engine according to one of claims 2 to 8, characterized in that the piston, the check valve and the spring of the hydraulic valve clearance compensation element (6) between the valve lever and the valve bridge (4) are arranged. Motor vehicle, in particular commercial vehicle, with an internal combustion engine according to one of the preceding claims.

Images