SHIFTING CYLINDER, SLIDING CAM SYSTEM AND CAMSHAFT

Description

[0001] The invention relates to a shift gate, a sliding cam system, and a camshaft. A shift gate according to the preamble of claim 1 is known, for example, from DE 10 2012 012 064 A1.

[0002] Generally, switching gates are used to move or adjust sliding cam elements in variable valve timing systems. Sliding cam elements with switching gates therefore represent an important component of variable valve timing in internal combustion engines. Essentially, such valve timing systems can influence the valve lift movements of the intake and exhaust valves by changing the cam profiles, or deactivate valves by changing the cam profiles.

[0003] For the axial displacement or adjustment of the sliding cam element, switching cams conventionally have switching grooves. Known switching groove designs include, for example, S-slots, double-S-slots, Y-slots, and X-slots. From the aforementioned DE 10 2012 012 064 A1 and DE 10 2013 111 476 A1, sliding cams with switching cams are known that have an X-slot for axial displacement of the sliding cam. An actuator pin engages in the respective slot section of the X-slot and displaces the sliding cam in an axial direction. Generally, X-slots have the disadvantage that at low switching speeds, due to the low rotational speed of the sliding cam or the camshaft, there is a risk of incorrect switching. The switching dynamics in the displacement direction are insufficient to reliably move the sliding cam from a first axial position to a second axial position, for example, using a detent device.The sliding cam can therefore snap back into the first axial position. Further documents revealing an X-groove are EP 2 839 122 B1, DE 10 2014 215428 B3 and DE 10 2013 220554 A1.

[0004] A switching cam with Y-shaped cam tracks is described, for example, in DE 10 2014 017 036 B3. The cam tracks are formed by grooves that merge into one another at a common end. Switching cams with Y-grooves require a larger axial installation space compared to switching cams with X-grooves, since with Y-grooves the maximum displacement of the sliding cam corresponds to the maximum switching stroke of the respective cam track.

[0005] The invention is therefore based on the objective of providing a shift gate in which, through an improved design, the installation space is reduced and operational reliability is increased. The invention is further based on the objective of providing a sliding cam system and a camshaft.

[0006] According to the invention, this problem is solved with regard to the shift gate by the subject matter of claim 1. With regard to the sliding cam system and the camshaft, the aforementioned problem is solved by the subject matter of claim 7 (sliding cam system) and claim 10 (camshaft), respectively.

[0007] Specifically, the problem is solved by a switching cam for a sliding cam system, which has at least two switching grooves for engaging at least one actuator pin. The two switching grooves run opposite to a direction of rotation and transition from a first section, in particular an insertion section of the actuator pin, to a second section, in particular an extension section of the actuator pin. The two switching grooves intersect each other in a crossover region between the two sections. In the crossover region, each of the two switching grooves has a maximum axial switching stroke that is greater than half of the total axial switching stroke of the switching cam.

[0008] The invention has several advantages. Due to the intersecting switching grooves, the switching mechanism according to the invention requires less axial installation space compared to known switching mechanisms with a Y-slot design. The switching grooves intersect each other in the intersection area between the first and second sections and change their axial position relative to the opposing switching groove. The total axial switching stroke of the switching mechanism is thus achieved within a narrower axial circumference than in switching mechanisms with a Y-slot design.

[0009] The total axial switching stroke of the shift gate corresponds to the maximum longitudinal displacement of the shift gate that it travels during a movement between at least two axial positions, in particular axial end positions, e.g., on a shaft, especially a camshaft. In other words, during a movement, the shift gate is moved from a first axial position to a second axial position, and the axial displacement traveled corresponds to the total axial switching stroke of the shift gate.

[0010] During a shifting operation, the switching cam is moved axially in the shifting direction by an actuator pin engaging one of the two switching grooves, starting from a first axial position and extending beyond half the total axial shifting stroke. In the first section, the respective switching groove slides along the actuator pin with its side wall facing the direction of shift. When the actuator pin is located in the region of the maximum axial shifting stroke of the switching groove, the switching cam has been shifted by more than half the total axial shifting stroke. At this position, the switching cam is closer to the second axial position than to the first, so that the switching cam is pulled to the second axial position, for example, by a detent mechanism. In the intersection area, the actuator pin switches to a side wall of the switching groove facing away from the direction of shift and slides along this side wall in the second section until the switching cam is at the second axial position.

[0011] The first axial position corresponds to the axial starting position from which the switching cam is moved towards the next, particularly the second, axial position during a displacement operation. The maximum axial switching stroke of the respective switching groove corresponds to the distance the switching cam travels in the displacement direction from the first axial position to the second axial position.

[0012] Since the maximum axial switching stroke is greater than half the total axial switching stroke of the switching cam, the switching cam, and thus preferably a sliding cam element coupled to the switching cam, moves reliably in the displacement direction from the first axial position to the second axial position. This advantageously prevents impermissible retraction or locking of the sliding cam element, especially at low switching speeds, and thus increases operational reliability.

[0013] Preferred embodiments of the invention are specified in the dependent claims.

[0014] In a particularly preferred embodiment, the maximum axial switching stroke of the switching slots is smaller than the total axial switching stroke of the switching cam. The maximum axial switching stroke is therefore preferably greater than half the total axial switching stroke and less than the full total axial switching stroke of the switching cam. In other words, the maximum axial switching stroke of the respective switching slot lies within a range between half and the full total axial switching stroke of the switching cam. This reduces the axial expansion of the switching cam, thereby saving axial installation space.

[0015] In a preferred embodiment, the two switching grooves each have a retraction flank in the first section and an extension flank in the second section, both running parallel to each other. In this embodiment, the two switching grooves have an axial distance from each other that corresponds to at least half of the total axial switching stroke of the switching cam. This axial distance is formed between the respective retraction flank of one of the two switching grooves and the respective extension flank of the other of the two switching grooves. Particularly at low switching speeds, this prevents impermissible, independent retraction of the switching cam or the sliding cam element, thus increasing operational reliability.

[0016] In a further preferred embodiment, the two switching grooves in the second section, starting from the intersection area, each have a braking flank for decelerating an actuator pin, which forms a continuous transition to the extension flank. The braking flank can thus form a jerk-free transition. This has the advantage that, during a displacement operation, the actuator pin transitions smoothly or gently through the braking flank into the extension flank, thus preventing high axial forces. This improves the switching behavior of the switching mechanism and increases the service life of the actuator pin.

[0017] Preferably, the braking flank is at least partially arcuate. The braking flank can also be at least partially concave. This further reduces the axial forces acting on the actuator pin. The braking flank can additionally have a straight section. It is also conceivable that the braking flank is formed from several straight flank sections.

[0018] According to the invention, the two switching grooves are separated from each other in the first section and partially overlap axially in the second section, so that the two switching grooves form a common groove. In other words, the switching grooves in the first section are each formed by a separate groove and merge into each other in the intersection area in such a way that they form a common groove in the second section. Preferably, the two switching grooves have a first axial distance from each other in the first section and a second axial distance from each other in the second section, which is smaller than the first axial distance. It is advantageous that the axial overlap reduces the required axial installation space for the formation of the switching grooves and enables the aforementioned braking flanks.

[0019] According to the invention, the common groove has a groove width that is greater than the groove width of the respective switching groove in the first section. The groove width of the common groove can be at least twice the groove width of the respective switching groove in the first section. The groove width of the common groove can also be less than or greater than twice the width of the respective switching groove in the first section. The large width of the common groove enables the realization of braking flanks, thereby reducing the axial forces acting on the actuator pin during a sliding operation. This further contributes to increased operational reliability.

[0020] Preferably, at least one guide rib is formed between the two switching grooves, which extends at least partially along the switching grooves in the first section. According to this embodiment, the guide rib tapers towards the intersection area. The two switching grooves can have a constant groove width or a varying, in particular changing, groove width along the guide rib.

[0021] According to dependent claim 7, the invention relates to a sliding cam system with at least one sliding cam element, at least one multi-pin actuator, in particular a double-pin actuator. The sliding cam element has at least one switching cam and can be locked in at least two axial positions. The switching cam has at least two switching grooves, wherein one of the two switching grooves interacts with at least one actuator pin of the multi-pin actuator during a sliding operation. The two switching grooves extend in the opposite direction of rotation and transition from a first section to a second section, with the two switching grooves intersecting each other between the two sections. The two switching grooves each have a maximum axial switching stroke that is greater than half of the total axial switching stroke of the switching cam.

[0022] In a preferred embodiment of the sliding cam system according to the invention, the total axial switching stroke of the switching cam is essentially equal to the distance between the two axial positions of the sliding cam element.

[0023] In a further preferred embodiment of the sliding cam system according to the invention, a detent device is provided and designed in such a way that, during a sliding operation, after reaching the maximum axial switching stroke of the respective switching groove, it moves, in particular pulls, the sliding cam element to the corresponding axial position in the direction of movement.

[0024] Preferably, the multiple pin actuator of the sliding cam system according to the invention comprises at least two actuator pins which have a distance from each other that corresponds to at least half of the total axial switching stroke of the switching cam.

[0025] According to dependent claim 10, the invention relates to a camshaft with at least one switching gate according to the invention and / or at least one sliding cam system according to the invention.

[0026] The advantages of the sliding cam system and the camshaft are described in relation to the advantages explained in connection with the shift gate. Furthermore, the sliding cam system, the camshaft, and the method can alternatively or additionally exhibit one or a combination of several of the features previously mentioned in relation to the shift gate.

[0027] The invention is explained in more detail below with reference to the accompanying drawings. The illustrated embodiments represent examples of how the switching mechanism according to the invention can be designed.

[0028] In the show, Fig. 1 is a schematic representation of the development of a switching cam with an X-switching groove according to the prior art; Fig. 2 is a schematic representation of the development of a switching cam with a Y-switching groove according to the prior art; and Fig. 3 is a schematic representation of the development of a switching cam according to a preferred embodiment according to the invention.

[0029] In Fig. 1 Figure 1 schematically shows the development of a circumferential section of a switching cam 10 according to the prior art, wherein the switching cam 10 has two switching grooves 11 which together form an X-slot. The switching cam 10 comprises a first section 12, a second section 13 and an intersection area 14 arranged circumferentially between them. The two switching grooves 11 extend from the first section 12 through the intersection area 14 into the second section 13 and intersect each other in the intersection area 14.

[0030] As in Fig. 1As shown, the two switching grooves 11 in the two sections 12, 13 have the same axial distance from each other. The two switching grooves 11 thus have a maximum axial switching stroke SH in the intersection area 14, which corresponds to half the total switching stroke GSH of the switching cam 10. Furthermore, it shows Fig. 1 an actuator pin 20 which engages in one of the two switching grooves 11 to axially displace the switching cam 10 and cooperates with it.

[0031] The maximum axial switching stroke SH described above according to Fig. 1 This has the disadvantage that, if the switching speeds are too low, e.g. due to low rotational speeds of a camshaft (not shown) with which the shift gate 10 is coupled, there is a risk of the shift gate 10 moving back or locking back into its first axial position, in particular its starting position, after passing the actuator pin 20 of the intersection area 14.

[0032] Fig. 2Figure 1 shows a schematic development of a circumferential section of a further switching cam 10 according to the prior art, wherein the switching cam 10 has two switching grooves 11 which together form a Y-slot. In contrast to the switching cam 10 according to Figure 10, the switching cam 10 has two switching grooves 11 which together form a Y-slot. Fig. 1 The two switching grooves 11 extend from the first section 12 into the second section 13 without intersecting each other. In the second section 13, the switching grooves 11 form a common groove 18, which essentially has a groove width corresponding to the two identical groove widths of the two switching grooves 11 in the first section 12. Furthermore, the two switching grooves 11 are axially separated only in the first section 12. In the second section 13, the two switching grooves 11 completely overlap each other.

[0033] As in Fig. 2As shown, the two switching grooves 11 have a maximum axial switching stroke SH in the opening area 21, which corresponds to the total switching stroke GSH of the switching cam 10. In other words, the maximum axial switching stroke SH of the respective switching grooves 11 corresponds to the full axial stroke or the full displacement travel of the switching cam 10. In comparison to the switching cam 10 with X-slot arrangement according to Fig. 1 The switching gate 10 with Y-slot arrangement has an increased axial extension of the circumferential area in which the two switching slots 11 extend circumferentially. The switching gate 10 according to Fig. 2 This therefore results in an increased need for construction space.

[0034] According to Fig. 2 Furthermore, at least two actuator pins 20 are required for the axial displacement of the switching cam 10. The axial distance X' between the two pins 20 corresponds to the total axial switching stroke GSH of the switching cam 10. The in Fig. 2The switching gate 10 shown has the further disadvantage that it has a hard transition in the opening area 21, where the two switching grooves 11 meet, so that high axial forces act on the engaging actuator pin 20 during a shifting operation in the opening area 21.

[0035] According to Fig. 3 A development of a circumferential region of a switching cam 10 according to a preferred embodiment of the invention is shown. The circumferential region shown corresponds, as in the Figs. 1 and 2 The circumferential areas shown are a schematic representation. The switching cam 10 serves to axially displace a sliding cam element (not shown) on a camshaft. The switching cam 10 can also be used to displace other elements arranged on a shaft in the longitudinal direction.

[0036] The switching cam 10 comprises a first section 12, a second section 13, and a circumferentially arranged intersection area 14 between them. The first section 12 corresponds to an insertion section in which an actuator pin 20 enters the associated switching groove 11 to axially displace the switching cam 10 or a sliding cam element (not shown) coupled to the switching cam 10. The second section 13 corresponds to an extension section in which the actuator pin 20 is located after the displacement process and from which the actuator pin 20 preferably extends again.

[0037] The shift gate 10 further comprises two shift grooves 11, which extend from the first section 12 into the second section 13 in the opposite direction of rotation of the shift gate 10 and intersect each other in the intersection area 14. In the intersection area 14, the two shift grooves 11 intersect at an intersection point KP. In other words, the shift grooves 11 switch axial sides with respect to the first section 12. It should be noted that the intersection area 14 does not form a clearly separated intermediate region, but is formed by a portion of the first section 12 and a portion of the second section 13. The intersection point KP forms the center of the intersection area 14.

[0038] As in Fig. 3As shown, the two switching grooves 11 in the first section 12 have a first axial distance and in the second section 13 a second axial distance from each other, which is smaller than the first axial distance. The axial distances are measured between the parallel switching groove regions 22 of the two switching grooves 11 in the respective sections 12 and 13.

[0039] The two switching grooves 11 each have a maximum axial switching stroke SH in the intersection area 14, which is greater than half of the total axial switching stroke GSH of the switching cam 10. Additionally, the maximum axial switching stroke SH of the switching grooves 11 is less than the total axial switching stroke GSH. In summary, the maximum axial switching stroke SH is therefore greater than half the total switching stroke GSH and less than the full total switching stroke GSH of the switching cam 10.

[0040] The total axial switching stroke GSH of the switching cam 10 corresponds to the maximum longitudinal displacement of the switching cam 10 (e.g., on a shaft, particularly a camshaft, not shown) that the switching cam 10 travels during a displacement operation between at least two axial positions, particularly axial end positions, e.g., on a shaft, particularly a camshaft. In other words, during a displacement operation, the switching cam 10 is moved from a first axial position to a second axial position, the axial displacement traveled corresponding to the total axial switching stroke GSH of the switching cam 10.

[0041] As in Fig. 3As can be seen, the two switching grooves 11 are separated from each other in the first section 12. Specifically, a guide rib 19 is axially arranged between the switching grooves 11 in the first section 12, partially separating them circumferentially. The guide rib 19 extends partially along the switching grooves 11 and tapers towards the intersection area 14. The switching grooves 11 can have a constant or varying, particularly changing, width along the guide rib 19. The widths of the two switching grooves 11 are equal in the first section 12.

[0042] In the second section 13, the two switching grooves 11 partially overlap axially, so that the two switching grooves 11 form a common groove 18. In other words, the two separate switching grooves 11 merge into one another opposite to the direction of rotation, with the switching grooves 11 forming a common groove 18 from the intersection point KP onwards. In the second section 13, no web is arranged between the two switching grooves 11.

[0043] The common groove 18 has a groove width that is greater than the groove width of the respective switching groove 11 in the first section. The groove width of the common groove 18 can be twice the groove width of the respective switching groove 11 in the first section 12. The groove width of the common groove 18 can also be less than or greater than twice the width of the respective switching groove 11 in the first section 12.

[0044] According to Fig. 3The two switching grooves 11 each have a retraction flank 15 in the first section 12 and an extension flank 16 in the second section 13, which run parallel and have an axial distance X from each other that corresponds to at least half of the total axial switching stroke GSH of the switching cam 10. The axial distance X is formed between the respective retraction flank 15 of the two switching grooves 11 and the respective extension flank 16 of the axially opposite switching groove 11.

[0045] Furthermore, the switching grooves 11 in the first section 12 each have an acceleration flank 23 for an actuator pin 20, extending from the entry flank 15 towards the intersection area 14. The acceleration flank 23 has an axial offset corresponding to the maximum axial switching stroke SH. Additionally, the switching grooves 11 in the second section 13 each have a braking flank 17 extending from the intersection area 14 for decelerating the actuator pin 20, which forms a continuous transition towards the extension flank 16. The respective braking flank 17 is arc-shaped. The acceleration flank 23 is structurally separated from the braking flank 17 in the intersection area 14. In the intersection area 14, the acceleration flank 23 of each switching groove 11 structurally transitions into the braking flank 17 of the other switching groove 11.

[0046] The following describes a displacement process of the switching cam 10, in which the switching cam 10 is moved from a first axial position to a second axial position. An actuator pin 20 of a multi-actuator (not shown) interacts with one of the switching grooves 11. During the displacement process, the switching cam 10 rotates, and the actuator pin 20 is fixed in the circumferential direction. It only performs an extension and retraction movement relative to the switching groove 11.

[0047] In a first step, the actuator pin 20 enters the switching groove 11 in the first section 12 and is positively guided in the circumferential direction between the guide rib 19 and the entry flank 15. The switching groove 11 is designed to be wide enough that a clearance is formed between the guide rib 19 and the entry flank 15 or the acceleration flank 23.

[0048] As the shift cam 10 continues to rotate, the entry flank 15 transitions into the acceleration flank 23. The actuator pin 20 slides along the acceleration flank 23, thereby displacing the shift cam 10 in the direction of rotation. When the actuator pin 20 is located at the intersection 14 of the two shift grooves 11 at the maximum axial shift stroke SH of the shift groove 11, the shift cam 10 is displaced by half of its total axial shift stroke GSH. At this position, the shift cam 10 is closer to the second axial position than to the first, so that the shift cam 10 is pulled to the second axial position, for example, by a detent mechanism. In the intersection 14, the actuator pin 20 moves from the acceleration flank 23 to the braking flank 17 of the shift groove 11 and slides along it in the second section 12.The actuator pin 20 then transitions from the braking flank 17 to the extension flank 16, whereby the switching cam 10 is located at the second axial position, in particular the axial end position.

[0049] Two actuator pins 20 are provided for the axial displacement of the switching cam 10, with each actuator pin 20 acting in conjunction with the switching cam 10 in one of the two displacement directions. The two actuator pins 20 have an axial distance X' from each other, which corresponds to the axial distance X between the insertion flank 15 of one switching groove 11 and the extension flank 16 of the other switching groove 11. Reference symbol list

[0050] 10 Shift gate 11 Shift grooves 12 First section 13 Second section 14 Crossover area 15 Entry flank 16 Exit flank 17 Braking flank 18 Common groove 19 Guide rib 20 Actuator pin 21 End area 22 Parallel shift groove areas 23 Acceleration flank SH Maximum axial shift stroke of the shift grooves GSH Total axial shift stroke of the shift gate KP Crossover point X Axial distance of the entry and exit flanks X' Axial distance of the actuator pins

Claims

1. Shift gate (10) for a sliding cam system, which has at least two shift grooves (11) for engagement of a respective actuator pin (20), wherein the two shift grooves (11) extend opposite to the direction of rotation and each extend from a first section (12) into a second section (13), wherein the two shift grooves (11) cross in a crossing region (14) between the two sections (12, 13), the center of the crossing region (14) forming a crossing point (KP), characterized in that the two shift grooves (11) in the crossing region (14) each have a maximum axial shift stroke (SH) that is greater than half of an axial total shift stroke (GSH) of the shift gate (10), wherein the two shift grooves (11) are separated from one another in the first section (12) and overlap one another in the second section (13), in particular form a common groove (18), wherein the common groove (18) has a groove width that is greater than the groove width of the respective shift groove (11) in the first section (12), the groove width of the common groove (18) being present at the crossing point (KP).

2. Shift gate according to claim 1, characterized in that the maximum axial shift stroke (SH) of the shift grooves (11) is smaller than the axial total shift stroke (GSH) of the shift gate (10).

3. Shift gate according to claim 1 or 2, characterized in that the two shift grooves (11) each have an entry flank (15) in the first section (12) and an exit flank (16) in the second section (13), which extend parallel to one another and have an axial spacing (X) from one another that corresponds to at least half of the axial total shift stroke (GSH) of the shift gate (10).

4. Shift gate according to one of the preceding claims, characterized in that the two shift grooves (11) in the second section (13), starting from the crossing region (14), each have a braking flank (17) for braking an actuator pin (20), which forms a transition running continuously to the exit flank (16).

5. Shift gate according to claim 4, characterized in that the braking flank (17) is formed at least partially in an arcuate shape.

6. Shift gate according to one of the preceding claims, characterized in that at least one guide web (19) is formed between the two shift grooves (11), which extends at least partially in the first section (12) and tapers toward the crossing region (14).

7. Sliding cam system having at least one sliding cam element, at least one multi-pin actuator, wherein the sliding cam element has at least one shift gate (10) according to at least one of the preceding claims and is movable between at least two axial positions, wherein the shift gate (10) has at least two shift grooves (11),which in each case extend opposite to the direction of rotation during a shifting operation with an actuator pin (20) of the multi-pin actuator, and extend from a first section (12) into a second section (13), wherein the two shift grooves (11) cross between the two sections (12, 13) and each have a maximum axial shift stroke (SH) that is greater than half of the axial total shift stroke (GSH) of the shift gate (10).

8. Sliding cam system according to claim 7, characterized in that the axial total shift stroke (GSH) of the shift gate (10) is equal to the distance between the two axial positions of the sliding cam element.

9. Sliding cam system according to claim 7 or 8, characterized in that the multi-pin actuator comprises two actuator pins (20) which have a spacing from one another that corresponds to at least half of the axial total shift stroke (GSH) of the shift gate (10).

10. Camshaft having at least one shift gate (10) according to claim 1 and / or at least one sliding cam system according to claim 7.