Engine brake device for cylinder unit of four-stroke internal combustion engine

Abstract

In an engine brake system for a cylinder unit of a four-stroke internal combustion engine, a brake rocker arm (1) is provided for reducing the pressure of the cylinder unit during a braking process, by means of which an exhaust valve (9) or an additional pressure reducing valve is actuated. When the brake rocker arm (1) is arranged in a valve mechanism housing (49) of an internal combustion engine, the brake rocker arm (1) is pivotally supported on a rocker arm shaft (5). In order to actuate the exhaust valves (9) or pressure reducing valves, the brake rocker arm (1) performs a pivoting movement generated by a brake cam (10) of the exhaust camshaft (11). The actuation can be switched on or off via an actuating element (13) arranged on the brake rocker arm (1).

Description

TECHNICAL FIELD

[0001] The invention relates to an engine braking device for a cylinder unit of a four-stroke internal combustion engine, the engine braking device having a braking rocker arm that actuates an exhaust valve or an additional pressure reducing valve during a braking process to decompress the cylinder unit, wherein the braking rocker arm configured as a double-armed rocker arm is pivotally supported at a rocker shaft when arranged in a valve mechanism housing of the internal combustion engine, and the braking rocker arm is actuated at one of its ends by a pivoting movement generated by a braking cam to actuate the exhaust valve or the pressure reducing valve, wherein the actuation can be switched on or off via an actuating element arranged at the braking rocker arm, the actuating element being arranged between the end of the braking rocker arm and the braking cam and configured as a hydraulically actuated piston unit, the piston unit being longitudinally displaceable and extending in a blind hole of the braking rocker arm in the case of forming a pressure chamber and having a cam roller at its end facing the braking cam. BACKGROUND OF THE INVENTION

[0002] EP 3 401 517 A1 shows a braking rocker arm having the above features. On the braking cam side of the braking rocker arm, a piston unit with a cam roller that can be hydraulically displaced is inserted into a blind hole on the lower side of the braking rocker arm. Here, a control piston that is aligned with the piston unit and guides the braking rocker arm axially above the piston unit is also constructed (see Figure 7 ), the control piston closing the pressure chamber of the piston unit when pressurized (activated braking rocker arm) and ensuring the discharge of oil from the pressure chamber in the absence of oil pressure.

[0003] An engine braking device for a four-stroke internal combustion engine is known from EP 2 425 105 B1. The engine braking device consists of an engine braking rocker arm that is pivotally supported together with a rocker arm for the control drive of the internal combustion engine on a common rocker shaft. Here, the engine braking rocker arm configured as a double-armed rocker arm is actuated by a braking cam arranged on an overhead exhaust camshaft, wherein a cam roller rotatably and directly supported in the engine braking rocker arm transfers the lift movement generated by the braking cam to the end of the first arm of the braking rocker arm.

[0004] A second arm extending from the bearing of the braking rocker arm is provided with an actuating element configured as an actuating piston in its end region, wherein a blind hole provided in the end region houses the actuating piston. Pressure medium supplied to a control valve extending transversely in the second arm via a solenoid valve and longitudinal and radial holes activates or deactivates the engine braking device due to the resulting position of the control valve.

[0005] When the engine braking device is activated, the actuating piston is in a position displaced from the blind hole. When deactivated, the actuating piston is displaced into the blind hole to such an extent that a gap occurs between the end face of the actuating piston and the boot that is slipped onto the end of the valve stem of the exhaust valve. This results in the lift movement of the braking cam not being transmitted to the exhaust valve, and thus the exhaust valve remains closed.

[0006] Furthermore, reference is made to document CN 1 02 787 880 B. This document shows a rocker arm with a conventional stroke and an optional engine braking function, the hydraulic piston unit of the rocker arm being constructed on the cam side. Summary of the Invention

[0007] The aim is to provide an engine braking device with a braking rocker arm that has a relatively small inertia and is compact and simply constructed.

[0008] This aim is achieved in that a first idle spring designed as a compression spring is arranged aligned with the actuating element on the side of the braking rocker arm facing away from the actuating element, the spring end of the first idle spring within the valve mechanism housing being supported at a stationary spring support, wherein the piston unit can be moved into its two respective positions via a hydraulically actuated two-way three-way valve, the control spool of which is arranged in a valve bore extending in the longitudinal direction of the braking rocker arm in the braking rocker arm, wherein the piston unit consists of a hollow piston defining a pressure chamber and an inner piston that can be guided to move therein, wherein the cam roller is rotatably supported on the end of the inner piston facing the braking cam, and wherein an idle stroke spring that preloads the inner piston in the direction of the braking cam is arranged between the bottom of the hollow piston and the spring stop of the inner piston.

[0009] Alternatively, this aim is achieved in that a first idle spring designed as a compression spring is arranged aligned with the actuating element on the side of the braking rocker arm facing away from the actuating element, the spring end of the first idle spring within the valve mechanism housing being supported at a stationary spring support, wherein the piston unit can be moved into its two respective positions via a hydraulically actuated two-way three-way valve, the control spool of which is arranged in a valve bore extending in the longitudinal direction of the braking rocker arm in the braking rocker arm, wherein the piston unit consists only of a piston that is guided in a blind hole and defines a pressure chamber, the cam roller being supported at the end of the piston that projects axially beyond the blind hole, and wherein an idle stroke spring that preloads the piston in the direction of the braking cam is arranged between the end face of the piston facing away from the cam roller and the bottom of the blind hole.

[0010] The control element is configured as a hydraulically actuated piston unit, which is arranged longitudinally displaceably in a blind bore of the brake rocker arm in the case of forming a pressure chamber. Here, the control element has a cam roller at its end facing the brake cam, and the cam roller realizes a friction-optimized rocker arm drive mechanism. The cam roller is structurally integrated with the piston unit.

[0011] On the side of the brake rocker arm facing away from the actuating element, a play spring configured as a compression spring is arranged, and the play spring can be supported at a stationary spring support with its spring end within the valve mechanism housing. The play spring causes the cam roller to always bear against the outer contour of the cam when the engine braking system is deactivated, i.e., when the actuating element is retracted into the brake rocker arm.

[0012] The piston unit can be moved into its two corresponding positions via a hydraulically actuated two-way three-way valve, and the spool of the two-way three-way valve is arranged in a valve bore extending along the longitudinal direction of the brake rocker arm. With this arrangement of the two-way three-way valve, a valve design with different spool positions can be achieved, and these positions can be clearly defined due to the large spacing of the connected oil passages and the long movement path.

[0013] According to a first variant of the present invention, the piston unit should consist of a hollow piston defining a pressure chamber and an inner piston slidably guided therein, and a free travel spring pre-tightening the inner piston in the direction of the brake cam is arranged between the bottom of the hollow piston and the spring stop of the inner piston. Therefore, the design of the unit composed of the cam roller and the inner piston is similar to that of a roller tappet.

[0014] According to a second variant of the present invention, the piston unit consists only of a piston defining a pressure chamber and guided in the blind bore, and the cam roller is supported at the end of the piston protruding axially beyond the blind bore. A free travel spring pre-tightening the piston in the direction of the brake cam is arranged between the end face of the piston facing away from the cam roller and the bottom of the blind bore.

[0015] By means of the latter-mentioned variants of the actuating element, it is achieved that when the engine braking system is activated, only one piston of the piston unit is moved by the pressure medium supplied via the working channel. Thus, the brake rocker arm can be operated with a significantly lower switching oil pressure when using the actuating element. In the first variant, the volume of the pressure chamber of the brake rocker arm changes during operation due to the stroke movement of the cam; in the second variant of the actuating element, the pressure chamber of the brake rocker arm always has a constant volume only through a piston pre-tightened by a spring.

[0016] In an improved embodiment of the present invention, it is specified that the dead travel spring has a lower pretension force than the idle travel spring. Therefore, when the engine braking system is deactivated, the inner piston, which is supported in the hollow piston only via the soft dead travel spring, moves longitudinally in such a way that the cam travel is completely received by the inner piston. Therefore, during the deactivation operation, not the entire rocker arm moves, but only the roller tappet on the cam side moves. In this way, the moving mass can be significantly reduced. In addition, when the brake rocker arm is deactivated, the brake rocker arm operates during the cam travel in such a way that it does not oppose the idle travel spring supporting it, i.e., the idle travel spring is not compressed. In this way, a low-friction operation of the brake rocker arm is achieved.

[0017] According to a design of the present invention (first variant), the inner piston and the hollow piston are guided together torsion-proof in the blind hole of the brake rocker arm. The anti-torsion part can be embodied as a locating pin, which is pressed into the hole of the brake rocker arm in such a way that its end extends radially into the blind hole and engages therein in a longitudinal slot of the hollow piston and in a longitudinal groove of the inner piston.

[0018] In order to control the two-way three-way valve and to actuate the piston unit, according to the present invention, pressure medium is supplied to it from the solenoid valve via a pressure medium channel extending in the longitudinal direction in the rocker shaft and at least one radial channel. Description of the Drawings

[0019] To further explain the present invention, reference is made to the drawings, in which two embodiments are simply shown. The drawings show:

[0020] Figure 1 A side view of a first embodiment of the brake rocker arm and a cross-sectional view of the rocker shaft for supporting and supplying pressure medium,

[0021] Figure 2 Shows according to Figure 1 A first longitudinal sectional view of the brake rocker arm constructed according to

[0022] Figure 3 Shows a second longitudinal sectional view of the brake rocker arm according to Figure 1 Cut along different cutting planes,

[0023] Figure 3a Shows Figure 3 An enlarged partial view IIIa in

[0024] Figure 4 Shows a dimensionally enlarged cross-section of the brake rocker arm according to Figure 1 Along line IV-IV in

[0025] Figure 5 Shows according to Figure 1Stereogram of the brake rocker arm

[0026] Figure 6 Shows a partial stereogram of the valve mechanism housing in the region of the cylinder unit, which has a brake rocker arm constructed according to Figure 1 arranged beside the rocker arm of the control drive mechanism

[0027] Figure 7 Shows the hydraulic circuit diagram of the actuating element applied in the brake rocker arm according to Figure 1

[0028] Figure 8 Shows a schematic diagram in the base circle phase of the cam in interaction with the brake system when the brake system is deactivated, according to Figure 1

[0029] Figure 8a Schematically shows the brake rocker arm in the lift position of the cam when the brake system is deactivated

[0030] Figure 8b Schematically shows the brake rocker arm in the base circle phase of the cam when the brake system is activated

[0031] Figure 8c Schematically shows the brake rocker arm in the lift position of the cam when the brake system is activated

[0032] Figure 9 Shows a side view of the second embodiment of the brake rocker arm, wherein the actuating element is formed by a hollow piston accommodating a free travel spring Detailed implementation mode

[0033] Figures 1 to 3 And Figures 4 to 5 In [reference], the brake rocker arm is denoted by 1. The brake rocker arm is constructed as a double-armed rocker arm. The brake rocker arm has a first arm 2 and a second arm 3 and is pivotally supported on the rocker arm shaft 5 via a sliding bearing 4. At the end of the first arm 2, a manual setting element 6 is arranged. The setting element has a spherical head and acts jointly with the valve stem end 8 of the exhaust valve 9 shown in Figures 8 to 8c via a slider 7 which is a valve stem support. As can be seen from Figures 8 to 8c The brake rocker arm 1 acts jointly with the cam 10 of the exhaust camshaft 11 via one end of its second arm 3

[0034] Here, especially from Figures 2 to 4 ​​As can be seen, the brake rocker arm 1 accommodates an actuating element 13 at the end of its second arm 3 via a blind hole 12. The actuating element is provided with a cam roller 14 facing away from the second arm 3. The second arm 3 is supported on the side facing away from the cam roller 14 at a spring support 16 which is fixed in position and extends in the valve mechanism housing of the cylinder head by means of a floating spring 15 configured as a compression spring. For this purpose, the floating spring 15 has a spring seat 15a.

[0035] In particular, as can be seen from Figure 4 As can be seen, the actuating element 13 configured as a piston unit 17 consists of an externally hollow piston 18 implemented in a cup shape. The cylindrical piston skirt 19 of the hollow piston is guided longitudinally displaceably in the blind hole 12. Here, the piston bottom 20 of the hollow piston 18 and the bottom 21 of the blind hole 12 jointly enclose a pressure chamber 22.

[0036] An equally hollow inner piston 23 is guided longitudinally displaceably in the hollow piston 18. The inner piston accommodates a dead - stroke spring 25 also configured as a compression spring in its cylindrical cavity 24. The dead - stroke spring 25 is supported at one end on the face of the piston bottom 20 facing away from the pressure chamber 22 and at the other end on an annular spring stop 26, where the spring stop 26 extends radially into the cavity 24 of the inner piston 23. In addition, the cam roller 14 is guided in the fork - shaped section 27 of the inner piston 23 via a roller pin 28.

[0037] As can be seen from Figure 1 As can be seen, a lubricating oil hole 29 extends in the rocker arm shaft 5. The lubricating oil hole supplies lubricating oil to the internal combustion engine at a switching oil pressure. A radial channel 30 branches off from the lubricating oil hole 29 and terminates in the region of the sliding bearing 4. Preferably, in order to convey the lubricating oil used as a hydraulic medium, a bag - shaped recess or an annular groove or an annular groove section is arranged in the sliding bearing 4, which is not shown in detail. As Figure 2 As shown in

[0038] In particular, as can be seen from Figure 3 and Figure 3a As can be seen, the two - way three - way valve 31 consists of a control spool 34. The control spool is accommodated in a valve hole 35 constructed in the brake rocker arm 1 and is pressurized at the end side via a control surface 36 with the pressure of the pressure channel 33 ( Figure 3a ). The longitudinal channel 38 of the control spool 34 leading to the check valve 37 starts from the control surface 36. The check valve 37 has a compression spring 37a.

[0039] By Figure 2As can be seen, in the control spool 34, at least one transverse hole 40 leading into the annular channel 39 is provided adjacent to the check valve 37, wherein the working channel 41 is connected to the annular channel 39, and the working channel can be established via a hole closed by a plug 41a. The working channel 41 leads to the pressure chamber 22 of the piston unit 17. The control spool 34 has a control edge 34a at its end facing away from the controllable control surface 36 and is loaded by the force of the valve spring 42. The force of the valve spring 42 acts via the plug 43 here, wherein the compression spring 37a of the check valve 37 bears against the end face of the plug 43 facing away from the valve spring 42.

[0040] In the first switching state of the engine braking device, that is, corresponding to the engine braking device being deactivated, the two-way three-way valve 31 is in the position where the control spool 34 abuts against one end of the valve bore 35 with its control surface 36. Therefore, the pressure medium from the working channel 41 can be discharged without pressure via the control edge 34a of the control spool 34 that opens the working channel 41. Therefore, the hollow piston 18 is in its end position shown in Figure 1 、 Figure 2 and Figure 3 In this position, the hollow piston abuts against the end of the blind hole 12 with its end face.

[0041] When the engine braking device is activated, the control surface 36 of the control spool 34 supplies lubricating oil under the switching pressure to the radial channel 30 and the pressure channel 33 via the lubricating oil hole 29. Thereby, the control spool 34 is lifted from the end of the valve bore 35 and the pressure medium reaches the longitudinal channel 38. The switching pressure of the lubricating oil present in the longitudinal channel 38 causes the check valve 37 to open. Therefore, the pressure medium reaches the pressure chamber 22 via the transverse hole 40, the annular channel 39, and the working channel 41. The pressure of this pressure medium causes the hollow piston 18 to move out of the blind hole 12 and here drives the inner piston 23 supported thereon via the idle stroke spring 25. Thereby, the cam stroke of the cam is transmitted to the brake rocker arm 1 via the cam roller 14 and the actuating element 13, and thus to the exhaust valve.

[0042] In the case of the engine braking device being deactivated, as described above, the hollow piston 18 is in its end position, and the end of the second arm 3 of the brake rocker arm 1 is tensioned in the direction of the exhaust camshaft via the idle spring 15; however, the cam roller 14 arranged in the inner piston 23 can perform an offset movement overcoming the force of the idle stroke spring 25 during the cam lift. Therefore, the idle stroke spring 25 has a smaller spring stiffness relative to the idle spring 15, that is, the idle stroke spring is constructed softer.

[0043] Furthermore, from the cross-section showing the idle spring 15, the brake rocker arm 1, the piston unit 17, and the cam roller 14 Figure 4The anti-twist portion 44 for the piston unit can be seen therein. The anti-twist portion is constituted by a positioning pin 45 which is press-fitted into a receiving cavity 46 extending transversely to the blind hole 12, such that the positioning pin projects with its end through a longitudinal slit 47 of the hollow piston 18 into a longitudinal groove 48 of the inner piston 23.

[0044] Figure 6 A partial perspective view shows the valve mechanism housing 49 of the cylinder head 50, which is assigned to the cylinder unit of an internal combustion engine. The cylinder unit has a control drive 52 constituted by two exhaust rocker arms 51, and beside the control drive there is arranged a braking rocker arm 1 constructed according to Figures 1 to 5 When the engine braking system is activated, the lift movement can be transmitted from the slide block 7 described above in connection with other figures to the valve stem end 8 of the exhaust valve 9. For this purpose, a valve bridge (not shown) is provided.

[0045] The two exhaust rocker arms 51 of the control drive 52 actuate two exhaust valves via this valve bridge. One of these exhaust valves can be the exhaust valve 9, so that this exhaust valve serves both as a scavenging valve and as a pressure reducing valve. The braking rocker arm 1 and the valve bridge act together such that the exhaust valve 9 opens at the end of the compression stroke of the cylinder unit. This figure also shows a solenoid valve 53 via which the pressure in the lubricating oil hole 29 is controlled. In addition, Figure 6 a partial view of the spring support 16 is shown, where, as described above, the spring support supports the floating spring 15 at the spring seat ring 15a of the floating spring.

[0046] In addition, Figure 7 a hydraulic diagram showing the solenoid valve 53, the two-way three-position valve 31 and the piston unit 17 is shown. The solenoid valve 53 and the two-way three-position valve 31 are in their positions when the engine braking system is activated. If the solenoid valve 53 is moved into its second switching state, the control pressure at the two-way three-position valve 31 increases and the two-way three-position valve also moves into its second switching state, such that the pressure medium flows from the working channel 41 via the check valve 37 into the pressure chamber 22 of the piston unit 17. Thereby, as described above, the piston unit 17 moves to its position where the stroke movement transmitting the cam 10 to the cam roller 14 is continued to be transmitted to the braking rocker arm, such that the engine braking system is activated.

[0047] Figures 8 to 8c The functions of the braking rocker arm 1 when the engine braking system is deactivated and activated are respectively shown. Figure 8 and Figure 8a relate to the state when the engine braking system is deactivated. Here, the hollow piston 18 is in its end position such that its piston bottom 20 abuts against the end of the blind hole 12 on the end side. The end of the second arm 3 of the braking rocker arm 1 is tensioned in the direction of the exhaust camshaft via the floating spring 15, but Figure 8aDuring the cam lift shown, the inner piston 23 can perform an offset movement together with the cam roller 14 against the force of the dead travel spring 25. Accordingly, the inner piston 23 retracts into the hollow piston 18.

[0048] According to Figure 8b and Figure 8c , the brake rocker 1 is in its function when the engine braking system is activated. With regard to the switching state of the two-way three-way valve, reference is made to Figure 3a , which is shown in an enlarged scale. Here, lubricating oil under the switching pressure is supplied to the control surface 36 of the control spool 34 via the lubricating oil hole 29, the radial passage 30, and the pressure passage 33. The control spool 34 is lifted from the end of the valve hole 35 so that the pressure medium reaches the longitudinal passage 38. The switching pressure of the lubricating oil present in the longitudinal passage 38 causes the check valve 37 to open, so that the pressure medium reaches the pressure chamber 22 via the transverse hole 40, the annular passage 39, and the working passage 41. Due to this pressure medium pressure, the hollow piston 18 is moved out of the blind hole 12 and hereby drives the inner piston 23 supported thereon via the dead travel spring 25, whereby the cam lift of the cam is transmitted to the brake rocker 1 via the cam roller 14 and the actuator 13 and thus to the exhaust valve 9.

[0049] Finally, Figure 9 shows a second embodiment of the actuator 54 arranged in the brake rocker 1, which actuator is different from the actuator 13 of Figures 2 to 4 and Figures 8 to 8c . Additionally, the brake rocker 1, the rocker shaft 5, the two-way three-way valve 31, etc. should be constructed according to the foregoing figures, so these structural elements carry the same reference numerals. According to Figure 9 , the brake rocker 1 has an actuator 54, which is configured as a hydraulically actuated piston unit 55. Here, a blind hole 56 provided in the brake rocker 1 houses a hollow piston 57, which is designed as a cup shape.

[0050] The skirt 58 of the piston 57 guides the piston longitudinally displaceably in the blind hole 56. The skirt 58 surrounds the dead travel piston 59, which is supported on one side at the bottom 60 of the blind hole 56 and on the other side at the end face 61 constructed inside the piston 57. The pressure chamber 62 is defined by the inside of the piston 57, the blind hole 56, and its bottom 60, and the pressure chamber is connected to the working passage 41. In the fork-shaped section 64 of the piston 57, the cam roller 63 is rotatably supported at the end of the piston facing away from the dead travel spring 59 and the pressure chamber 62.

[0051] With Figures 2 to 4 and Figures 8 to 8cCompared with the first embodiment, in this embodiment of the actuating element 55, when the engine braking system is activated, the advantage is that the pressure medium supplied via the working channel no longer causes the two components of the piston unit to move relative to the outer hollow piston against the force of the dead travel spring, i.e., it no longer causes the hollow inner piston to move relative to the outer hollow piston against the force of the dead travel spring. Thereby, the actuating element 55 can be used to operate the brake rocker 1 with a significantly lower switching oil pressure. In the first embodiment, the volume of the pressure chamber of the brake rocker changes during operation due to the stroke movement of the cam; in the second embodiment of the actuating element 55, the pressure chamber always has a constant volume through only one spring-loaded piston 57.

[0052] List of reference numerals

[0053] 1 Brake rocker

[0054] 2 First arm of 1

[0055] 3 Second arm of 1

[0056] 4 Sliding bearing

[0057] 5 Rocker shaft

[0058] 6 Manual setting element

[0059] 7 Slide block of 6

[0060] 8 Valve stem end

[0061] 9 Exhaust valve

[0062] 10 Brake cam of 11

[0063] 11 Exhaust camshaft

[0064] 12 Blind hole

[0065] 13 Actuating element

[0066] 14 Cam roller

[0067] 15 Idle spring

[0068] 15a Spring seat of 15

[0069] 16 Spring support

[0070] 17 Piston unit

[0071] 18 Outer hollow piston of 17

[0072] 19 Cylindrical piston skirt of 17

[0073] 20 Piston bottom of 18

[0074] The bottom of 21 12

[0075] The pressure chamber of 22 17

[0076] The hollow inner piston of 23 17

[0077] The cylindrical hollow cavity of 24 23

[0078] The idle stroke piston of 25 13

[0079] The annular spring stop in 24

[0080] The fork-shaped section of 27 23

[0081] Roller pin 28

[0082] Lubricating oil hole 29

[0083] Radial channel 30

[0084] Two-position three-way valve 31

[0085] The protrusion of 32 1

[0086] Pressure channel 33

[0087] Control spool of 34 31

[0088] Control edge of 34a 34

[0089] Valve hole of 35 32

[0090] Control surface of 36 34

[0091] Check valve 37

[0092] Compression spring of 37a 37

[0093] Longitudinal channel of 34 38

[0094] Annular channel of 34 39

[0095] Transverse hole of 34 40

[0096] Working channel 41

[0097] Plug 41a

[0098] Valve spring of 31 42

[0099] Plug 43

[0100] Anti-twist part for 14 and 17

[0101] Positioning pin 45

[0102] 46 Accommodating hole

[0103] 47 Longitudinal seam

[0104] 48 Longitudinal groove

[0105] 49 Valve mechanism housing

[0106] 50 Piston head

[0107] 51 Exhaust rocker arm

[0108] 52 Control drive mechanism

[0109] 53 Solenoid valve

[0110] 54 Actuating element

[0111] 55 Hydraulically actuated piston unit of 54

[0112] 56 Blind hole of 1

[0113] 57 Hollow piston of 55

[0114] 58 Skirt of 57

[0115] 59 Idle stroke spring

[0116] 60 Bottom of 56

[0117] 61 End face of 57

[0118] 62 Pressure chamber of 55

[0119] 63 Cam roller

[0120] 64 Fork-shaped section of 57

Claims

1. An engine brake device for a cylinder unit of a four-stroke internal combustion engine, the engine brake device having a brake rocker arm (1) which actuates an exhaust valve (9) or an additional pressure relief valve during a braking process in order to relieve the pressure of the cylinder unit, wherein: A brake rocker arm (1) configured as a double-arm rocker arm is pivotally supported on a rocker arm shaft (5) when it is arranged in a valve train housing (49) of the internal combustion engine, and the pivoting movement of the brake rocker arm at one end thereof is transmitted to the exhaust valve (9) or the pressure reducing valve to actuate it, wherein the actuation can be connected or disconnected via an actuator (13, 54) arranged at the brake rocker arm (1), the actuator being arranged between the end of the brake rocker arm (1) and the brake cam (10) and configured as a hydraulically actuated piston unit (17, 55), the piston unit extending longitudinally movably in a blind hole (12, 56) of the brake rocker arm (1) while forming a pressure chamber (22, 62) and having a cam roller (14, 63) at its end facing the brake cam (10), The invention is characterized in that a first lost motion spring (15) configured as a compression spring is arranged on a side of the brake rocker arm (1) facing away from the actuator (13) in alignment with the actuator (13), the first lost motion spring being supported at a fixed spring support (16) with its spring end inside the valve mechanism housing (49), wherein the piston unit (17) can be moved into its two corresponding positions via a hydraulically actuated two-position three-way valve (31), the control slide valve (34) of which is arranged in the brake rocker arm (1) in the longitudinal direction of the brake rocker arm (1) The invention relates to a valve hole (35) extending in a direction thereof, wherein the piston unit (17) is composed of a hollow piston (18) defining the pressure chamber (22) and an inner piston (23) which can be guided to move therein, wherein the cam roller (14) is rotatably supported at the end of the inner piston (23) facing the brake cam (10), and wherein a free travel spring (25) is arranged between the bottom (20) of the hollow piston (18) and the spring stop (26) of the inner piston (23) for prestressing the inner piston (23) in the direction of the brake cam (10).

2. The engine brake system according to the preamble of claim 1, It is characterized in that A first lost motion spring (15) configured as a compression spring is arranged on a side of the brake rocker arm (1) facing away from the actuator (54) in alignment with the actuator (54), the first lost motion spring being supported with its spring end within the valve mechanism housing (49) on a fixed spring support (16), wherein the piston unit (55) can be moved into its two corresponding positions via a hydraulically actuated 3 / 2-way valve (31), the control slide valve (34) of which is arranged in the brake rocker arm (1) in the longitudinal direction of the brake rocker arm (1). The invention relates to a valve bore (35) extending in a direction thereof, wherein the piston unit (55) consists only of a piston (57) guided in the blind hole (56) and defining the pressure chamber (62), the cam roller (63) being supported at an end of the piston protruding axially beyond the blind hole (56), and wherein a free travel spring (59) is arranged between an end face (61) of the piston (57) facing away from the cam roller (63) and a bottom (60) of the blind hole (56) for prestressing the piston (57) in the direction of the brake cam (10).

3. The engine brake device according to claim 1 or 2, characterized in that: The lost motion spring (25, 59) has a lower tension than the lost motion spring (15).

4. The engine brake device according to claim 1, characterized in that The inner piston (23) and the hollow piston (18) are guided together in the blind hole (12) in a rotationally fixed manner.

5. The engine brake device according to claim 1 or 2, characterized in that: Pressure medium is supplied from a solenoid valve (53) via a lubricating oil hole (29) extending in the longitudinal direction of the rocker arm shaft (5) and at least one radial channel (30) to control the control slide valve (34) and actuate the actuator (13).

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