Valve train for the variable actuation of an inlet valve and an outlet valve, and internal combustion engine having a valve train of this type

Abstract

A valve train for the variable actuation of an inlet valve and an outlet valve of a combustion chamber of an internal combustion engine, having a first operative connection between a valve actuating device and the inlet valve and a second operative connection between the valve actuating device and the outlet valve. The first operative connection and the second operative connection are assigned an interrupting element which is set up to temporarily interrupt the operative connections. The first operative connection and the second operative connection are connected to the same interrupting element in such a way that the first operative connection and the second operative connection can be interrupted temporarily by way of the interrupting element.

Claims

1. An internal combustion engine, comprising: a plurality of combustion chambers; an inlet valve and an outlet valve assigned to each of the combustion chambers, the inlet valve and the outlet valve of each combustion chamber being assigned to each other as a valve pair; a valve train comprising a valve actuating device, a first operative connection between the valve actuating device and the inlet valve of each valve pair, and a second operative connection between the valve actuating device and the outlet valve of each valve pair; an interrupting element assigned to each valve pair by being connected to the first operative connection and the second operative connection, the interrupting element being configured to temporarily interrupt the first and second operative connections; and a control unit, including a respective actuation means for each interrupting element assigned to a valve pair, wherein the control unit is configured to actuate each interrupting element at least twice per working cycle of a corresponding combustion chamber of the plurality of combustion chambers.

2. The internal combustion engine according to claim 1, wherein the first and second operative connections are hydraulic operative connections, wherein the interrupting element is a switching valve.

3. The internal combustion engine according to claim 1, wherein the first operative connection includes a first hydraulic path to a first slave cylinder, wherein the second operative connection includes a second hydraulic path to a second slave cylinder, wherein the interrupting element is connected to the first hydraulic path and to the second hydraulic path.

4. The internal combustion engine according to claim 3, wherein the interrupting element is connected to the first hydraulic path and to the second hydraulic path by a common fluid connection.

5. The internal combustion engine according to claim 3, wherein the interrupting element is connected to the first hydraulic path by a first interrupting nonreturn valve, and the interrupting element is connected to the second hydraulic path by a second interrupting nonreturn valve.

6. The internal combustion engine according to claim 3, further comprising a hydraulic medium accumulator fluidically connected to the interrupting element, wherein the interrupting element is configured to selectively and independently bring the first hydraulic path and the second hydraulic path into fluidic connection with the hydraulic accumulator.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The invention is explained in more detail below with reference to the drawing, which:

(2) FIG. 1 shows a schematic illustration of an example of a variable valve train for an inlet valve;

(3) FIG. 2 shows a schematic illustration of an example of a valve train for variable actuation of an inlet valve and an outlet valve, and

(4) FIG. 3 shows a schematic illustration of an exemplary embodiment of an internal combustion engine with a valve train for variable actuation of an inlet valve and an outlet valve.

DETAILED DESCRIPTION OF THE INVENTION

(5) FIG. 1 shows a schematic illustration of an example of a valve train 1 for the variable actuation of an inlet valve 3. The inlet valve 3 is assigned to a combustion chamber 7 (only indicated schematically here) of an internal combustion engine 9 (likewise only indicated schematically).

(6) The valve train 1 has a first operative connection 11 between a valve-actuating device 13, here specifically between a first actuating element 15, which is in the form of a cam of a camshaft, and the inlet valve 3. Said first operative connection 11 is in the form of a hydraulic operative connection and to this extent comprises a first hydraulic path 17. The first hydraulic path 17 has a first master cylinder 19, which interacts with the first actuating element 15, and a first slave cylinder 21, wherein, during a rotational movement of the first actuating element 15, the first master cylinder 19 is caused to perform a stroke movement, by means of which hydraulic medium is forced out of the first master cylinder 19 via the first hydraulic path 17 into the first slave cylinder 21, wherein the first slave cylinder 21 is operatively connected to the inlet valve 3 in such a manner that the latter is forced by the first slave cylinder 21 counter to the prestressing force of a prestressing element 23, in particular a spring, into an open position.

(7) In the first hydraulic path 17, a first nonreturn valve 25 and a first bypass 27, which bypasses the first nonreturn valve 25 and in which a first throttle element 29 is arranged, are arranged between the first master cylinder 19 and the first slave cylinder 21.

(8) If hydraulic medium is forced out of the first master cylinder 19, the first nonreturn valve 25 can open, and therefore hydraulic medium can flow via the first nonreturn valve 25 to the slave cylinder 21. If the first actuating element 15 rotates further, a volume in the first master cylinder 19 is increased again, and therefore hydraulic medium can flow back into the latter. At the same time, the hydraulic medium in the first slave cylinder 21 is pressurized by the prestressing element 23. In this operating state, the first nonreturn valve 25 is forced into its blocking position. The hydraulic medium then flows out of the first slave cylinder 21 via the first bypass 27 and the first throttle element 29 back into the first master cylinder 19, with the inlet valve 3 being shifted at the same time to its closed position. The closing behavior of the inlet valve 3 is determined in particular by the first prestressing element 23, on the one hand, and the first throttle element 29, on the other hand, in particular by the coordination thereof with each other.

(9) In order to bring about variable actuation of the inlet valve 3, the valve train 1 has a first interrupting element 31 which is assigned to the first operative connection 11 and is configured to interrupt the first operative connection 11 at times. The first interrupting element 31 is preferably in the form of a switching valve, here in particular in the form of a 2/2-way valve.

(10) The first interrupting element 31 is connected here by a first fluid connection 33on the side of the first master cylinder 19to the first hydraulic path 17. The first interrupting element 31 is fluidically connected by a second fluid connection 35 to a hydraulic medium accumulator 37. The first interrupting element 31 is configured in order. In a first switching state, to produce a fluidic connection between the first fluid connection 33 and the second fluid connection 35 and therefore at the same time between the first hydraulic path 17 and the hydraulic medium accumulator 37, and in order, in a second switching state (illustrated here), to interrupt the fluidic connection between the first fluid connection 33 and the second fluid connection 35.

(11) A variable actuation of the inlet valve 3 is now brought about by the first interrupting element 31 in accordance with the lost-motion principle by the latter being shifted into its first switching state, for example at a predetermined point in time during a stroke movement of the first valve 3 as a result of which the fluidic connection between the first hydraulic path 17 and the hydraulic medium accumulator 37 is opened up, h e hydraulic medium forced out of the first master cylinder 19 is then at least partially shut off via the first interrupting element 31 into the hydraulic medium accumulator 37, as a result of which the pressure in the first hydraulic path 17 on the side of the first master cylinder 19 drops, and therefore blocks the first nonreturn valve 25. The valve stroke of the inlet valve 3 is thereby interrupted, and the latter closes, with hydraulic medium being likewise forced out of the first slave cylinder 21 by the prestressing force of the prestressing element 23 via the first bypass 27 and the first throttle element 29 and further via the first interrupting element 31 into the hydraulic medium accumulator 37. A delayed valve stroke of the inlet valve 3 can also be brought about in an analogous manner by, at the beginning of the stroke movement of the first master cylinder 19, the first interrupting element 31 being shifted into its first switching state and only subsequently being shifted into its second switching state during the stroke movement of the first master cylinder 19. It is therefore possible to provide a fully variable valve train for the inlet valve 3 by means of the first interrupting element 31. If, by contrast, the first interrupting element 31 remains in its second switching state during an operating cycle of the internal combustion engine 9, a normal valve stroke of the inlet valve 3 is brought about, the stroke curve of which is substantially determined by the configuration, in particular shape, of the first actuating element 15. In particular whenever the first interrupting element 31 is in the form of a continuous switching valve which can take up a multiplicity of intermediate positions between the first switching state and the second switching state, a valve stroke curve virtually as desired can be produced in a very flexible manner below the normal valve stroke curve determined by the first actuating element 15.

(12) In a period of time in which the volume of the first master cylinder 19 is increased again, hydraulic medium is conducted out of the hydraulic medium accumulator 37 via a bypass path 39 and a first bypass nonreturn valve 41 back Into the first master cylinder 19.

(13) In particular for an Initial supply of the first hydraulic path 17 with hydraulic medium, but also for leakage compensation, the bypass path 39 is connected here to a hydraulic medium source 43 via a source nonreturn valve 45. It is possible here for a filter 47 to be provided in this connection, in particular upstream of the source nonreturn valve 45.

(14) FIG. 2 shows a schematic illustration of a second example of a valve train 1 for the variable actuation of an inlet valve 3 and of an outlet valve 5. Identical and functionally identical elements are provided with the same reference signs, and therefore reference is made in this respect to the previous description. The inlet valve 3 and the outlet valve 5 are in particular preferably assigned to the same combustion chamber 7 of the internal combustion engine 9.

(15) The outlet valve 5 here is assigned a second operative connection 11 between the valve-actuating device 13, here specifically a second actuating element 15, which is likewise in the form of a cam, wherein the second operative connection 11 is in the form of a hydraulic operative connection and has a second hydraulic path 17. The latter connects a second master cylinder 19 to a second slave cylinder 21, wherein the second actuating element 15 acts on the second master cylinder 19. The outlet valve 5 has a second prestressing element 23. A second nonreturn valve 25 which is bypassed by a second bypass 27 by the arrangement of a second throttle element 29 is arranged in the second hydraulic path 17.

(16) The second hydraulic path 17 is fluidically connectedon the side of the second master cylinder 19to a second first inlet 33 of a second interrupting element 31, wherein the second interrupting element 31 has a second second fluid connection 35. The first interrupting element 31 and the second interrupting element 31 are fluidically connected via their second fluid connections 35, 35 to the same hydraulic medium accumulator 37.

(17) The second interrupting element 31 here is also in the form of a switching valve, in particular a 2/2-way valve.

(18) The operating principle of the actuation of the outlet valve 5 and of the second hydraulic path 17 and of the second interrupting element 31 is identical to the operating principle explained previously in conjunction with FIG. 1 with regard to the inlet valve 3. Reference is therefore made to this extent to the previous description. Hydraulic medium is also returned from the hydraulic medium accumulator 37 into the second hydraulic path 17 here via the bypass path 39 and via a second bypass nonreturn valve 41.

(19) It is important that an interrupting element is provided in each case here for the inlet valve 3, on the one hand, and the outlet valve 5, on the other hand, namely the first interrupting element 31 and the second interrupting element 31. This necessitates a comparatively expensive and construction-space-demanding configuration of the valve train 1.

(20) FIG. 3 shows a schematic Illustration of an exemplary embodiment of the valve train 1. Identical and functionally identical elements are provided with the same reference signs, and therefore reference is made to this extent to the previous description. The first operative connection 11 and the second operative connection 11apart from the variable actuation of the inlet valve 3 and the outlet valve 5function here precisely as has been described with respect to FIGS. 1 and 2.

(21) However, it has been recognized that it is possible to achieve full variability of the actuation for both valves, namely the inlet valve 3 and the outlet valve 5, by only one and precisely one interrupting element 31 being used jointly for the two valves, namely the inlet valve 3 and the outlet valve 5. In the exemplary embodiment illustrated here, only one interrupting element 31 is therefore provided which is assigned both to the first operative connection 11 and to the second operative connection 11. Said interrupting element is configured for temporarily interrupting both the first operative connection 11 and the second operative connection 11. This is possible because there is a gap in time between the actuation times of the inlet valve 3, on the one hand, and the outlet valve 5, on the other hand, and therefore precisely one interrupting element 31 can be actuated at a first time for the variable actuation of the inlet valve 3, wherein said interrupting element can be actuated at a second time, which is different from the first time, for the variable actuation of the outlet valve 5. The first time and the second time typically do not overlap during the operation of the internal combustion engine 9, and therefore the full variability for both valves can be ensured with the one interrupting element 31.

(22) The one interrupting element 31 is connected here via its first fluid connection 33 both to the first hydraulic path 17 and to the second hydraulic path IT.

(23) In particular, it is shown with reference to FIG. 3 that the first fluid connection 33 is connected to the first hydraulic path 17 via a first interrupting nonreturn valve 49, wherein the first fluid connection 33 is connected via a second interrupting nonreturn valve 49 to the second hydraulic path 17. The interrupting nonreturn valves 49, 49 are arranged here fluidically parallel to each other; in particular, a branching is produced from the first fluid connection 33 to the first and second interrupting nonreturn valves 49, 49. The interrupting nonreturn valves 49, 49 are in each case prestressed in a direction pointing away from the first fluid connection 33 and toward the hydraulic paths 17, 17 into a closed position. Since hydraulic medium pressure is built up with a time delay in the first and second hydraulic paths 17, 17, the operating principle is produced by the fact that, for example, during the build-up of pressure in the first hydraulic medium path 17 by the first master cylinder 19 and simultaneous opening of the first interrupting element 31, i.e. the switching thereof into the first switching state, the first interrupting nonreturn valve 49 can open, and therefore hydraulic medium can be shut off out of the first hydraulic path 17 via the first interrupting nonreturn valve 49 and the interrupting element 31 into the hydraulic medium accumulator 37. At the same time, however, the second interrupting nonreturn valve 49 is closed, and therefore there is no communication between the hydraulic paths 17, 17. The same applies precisely conversely for a period of time in which hydraulic medium pressure is built up in the second hydraulic path IT by the second master cylinder 19 and the switch-over element 31 is switched into its first open switching state. Overall, the interrupting nonreturn valves. 49, 49 therefore prevent an undesirable hydraulic communication between the two hydraulic paths 17, 17 in a simple and efficient manner.

(24) The interrupting element 31 is configured overall in order optionally, namely in particular depending on its switching position, on the one hand, and the pressure levels in the hydraulic medium paths 17, 17, on the other hand, to bring the first hydraulic path 17, the second hydraulic path 17, orin its second switching stateneither of the hydraulic paths 17, 17 into fluidic connection with the hydraulic medium accumulator 37.

(25) The internal combustion engine 9 preferably has a plurality of combustion chambers 7, wherein in particular each of the combustion chambers 7 is in each case assigned an inlet valve 3 and an outlet valve 5. In particular, each of the combustion chambers 7 can also be assigned two inlet valves 3 and two outlet valves 5. The inlet valves 3 and the outlet valves 5 of the individual combustion chambers 7 are assigned to one another in pairs, wherein each valve pairas illustrated in FIG. 3is assigned precisely one interrupting element 31. In addition, the internal combustion engine 9 has a control unit 51 which has an actuating means 53, in particular a power amplifier, for each interrupting element 31 assigned to a valve pair. In the case of the exemplary embodiment according to FIG. 3, in particular in contrast to the configuration according to FIG. 2, only half the number of actuating means 53 are required for the internal combustion engine 9 because each valve pair is assigned only one interrupting element 31 instead of two interrupting elements 31, 31.

(26) The control unit 51 is configured in particular in order to actuate the interrupting elements 31, which are assigned thereto, at least twice per operating cycle of a combustion chamber 7 assigned to the respective interrupting element 31, namely once for the variable actuation of the inlet valve 3, and a second time for the variable actuation of the outlet valve 5.

(27) The fact that the control unit 51 is configured for this purpose does not, of course, exclude the fact that also at least one of the valves 3, 5 is not variably actuated once during an operating cycle, wherein then the interrupting element 31 is also not actuated. It is also possible for the interrupting element 31 not to be actuated at all in an operating cycle because none of the valves 3, 5 is actuated variably.

(28) Overall, it has been shown that, with the valve train 1 proposed here, in particular in a same construction space volume as in the case of a fully variable valve train only on the inlet side, use can be made of a valve train which is second interrupting element 31 per valve pair being omitted. This also results in a cost reduction on account of a lower number of components. Furthermore, the required power amplifiers in the control unit 51 are reduced, and therefore costs and energy expenditure are also omitted in this respect.