EP1549828A1

EP1549828A1 - Locking device for a camshaft adjuster

Info

Publication number: EP1549828A1
Application number: EP03750562A
Authority: EP
Inventors: Kai Lehmann; Jens Plank; Holger Rudsinzki
Original assignee: DaimlerChrysler AG
Current assignee: Mercedes Benz Group AG
Priority date: 2002-10-08
Filing date: 2003-09-17
Publication date: 2005-07-06
Also published as: US7234427B2; JP2006502339A; US20050205032A1; JP4156594B2; DE10246838A1; WO2004033860A1

Abstract

The invention relates to a locking device for a camshaft adjuster (10), the latter comprising a rotor (12), which is connected to a camshaft in a rotationally fixed manner, is mounted to have limited rotation in a drive part (11) and whose vanes (13, 14) engage in gaps by means of sections extending from an inner base ring (16) to an outer peripheral ring (17), said gaps being formed by radial projections (15) of the drive part (11). A respective pressure chamber (18, 19) is formed in a peripheral direction on both sides of a vane (13, 14). Compressed oil can be fed to said pressure chamber via a control valve, in such a way that the rotor (13, 14) is shifted through a rotation angle in relation to the drive part (11), in accordance with the pressure ratios that are prevailing in the pressure chambers (18, 19). The locking device has at least one locking bolt (23, 31, 32, 33) that can be hydraulically released and that is impinged in a locking direction by a compression spring. Said locking bolt co-operates with a respective detent recess and couples the rotor (12) to the drive part (11) in a locked position.

Description

Locking device for a camshaft adjuster

The invention relates to a locking device for a camshaft adjuster according to the preamble of claim 1.

Camshaft adjusters are used in valve-controlled internal combustion engines to change the angular position of the camshaft relative to the crankshaft or other camshafts or to cause a phase shift. As a result, the opening times of the gas exchange valves are adjusted in the early or late direction relative to the top dead center of a piston in order to optimize the charge exchange of the combustion chambers or cylinders depending on the respective operating point of the internal combustion engine.

From DE 101 27 168 AI a camshaft adjuster is known which has an impeller. This is non-rotatably connected to the camshaft and rotatably supported to a limited extent in a drive part which is generally driven by the crankshaft of the internal combustion engine via a toothed belt. The impeller engages with its wings in spaces between the drive part, which are formed by projections pointing radially inwards. The projections limit the maximum angle of rotation by which the impeller can be rotated relative to the drive part. Hydraulic pressure chambers are formed between the vanes and the projections, which are controlled via a control valve, so that the relative position of the impeller to the drive part results from the pressure ratios of the pressure chambers, which are circumferential to both sides of a wing. During the breaks in operation of the internal combustion engine, the impeller is adjusted to one of the two end positions by springs. When the internal combustion engine starts, the rotating cams of the camshaft exert reaction forces that change in the direction of rotation, which lead to leading and lagging torques. If no or a low pressure has built up in the pressure chambers, the reaction forces overcome the spring forces, so that the vanes lift off their contact with the radial projections and move to the opposite radial projection. If they strike there or if they hit the contact surface again when the reaction forces change, they generate annoying noises. For this reason, the impeller is generally locked in relation to the drive part by a locking bolt, which is axially or radially displaceably mounted either in the impeller or in the drive part and engages in a locking hole in the other part. A spring presses the locking bolt into the locking hole. The locking bolt is unlocked hydraulically by initially applying a pressure chamber to the control valve when the internal combustion engine is started. If the pressure in the pressure chamber becomes greater than the force of the locking spring, the locking bolt is pushed out of the locking hole and the camshaft adjuster is unlocked.

In the locked end position of the impeller, the camshaft must assume an angular position in relation to the crankshaft in which the internal combustion engine can be started cheaply. For this reason, a camshaft adjuster for intake valve is usually locked late in an end position and early for exhaust valve in an end position. In order to enable a larger adjustment range, in particular for the intake valves, the impeller for starting the internal combustion engine is locked between the two end positions. After starting er or controls a control valve in the unlocked position of the locking bolt, the rotational angle position according to an operating map of the internal combustion engine.

Locking the camshaft adjuster in a middle position is difficult because the relative speed between the impeller and the drive part is very high when the camshaft adjuster is not activated and the pressure chambers are depressurized. In this operating state, the camshaft adjuster tends to move late into the position because of the driving forces that act on the drive part from the crankshaft. To better engage the locking bolt, the known locking device has a stepped locking hole, the outer step of which is designed as an elongated hole in the adjustment direction. In the case of pressure-free pressure chambers and a movement in the late direction, the locking bolt first engages in the first stage, which prevents the movement in the opposite direction beyond the middle position by one end of the elongated hole matching the middle position. At this end, both stages are congruent, so that the locking bolt can snap into the second stage and thus lock the impeller in both directions. According to one embodiment, several stages can also be provided, which restrict the freedom of movement of the locking bolt more and more, the innermost stage being designed as a fixing hole. Furthermore, the steps may extend circumferentially to either side of the innermost step.

The steps result in a relatively long radial travel of the locking bolt and, in connection with this, a long spring travel of the locking spring. Furthermore, its free end is heavily loaded when threading and striking the limit of a step, so that great wear can be expected. This allows between the innermost Step, which serves as a fixing hole, and the locking bolt a large game arise over time. The steps and the locking bolt are therefore hardened at the critical points.

From DE 199 18 910 AI a camshaft adjuster is known which has two spring-loaded locking bolts distributed over the circumference of the impeller, which are guided radially or axially displaceably in the drive part and engage in the locking position in a locking hole of the impeller. The locking bolts are unlocked hydraulically in that an effective pressure in the pressure chambers acts on an end face of the locking bolts and moves them against the force of the loading spring into an unlocked position as soon as the pressure has reached a corresponding value. It is provided that the unlocking bolts are cylindrical and are each only acted upon by the pressure of the pressure chambers which act in the late or in the early direction.

As a variant, it is provided that the locking bolts are designed as stepped pistons, the small piston area being acted upon by the pressure of one pressure chamber and the larger piston area being acted upon by the pressure of the other pressure chamber. The resulting force generated by the pressures shifts the locking bolts into the unlocked position.

While one of the locking bolts works together with a cylindrical fixing bore designed as a fixing bore, through which the impeller is locked in both directions of rotation, the other locking bolt works together with an elongated hole extending on a circular path, one end of which determines the same locking position of the impeller, while the other End extends towards late. If one of the locking bolts is in the area of the elongated hole when the internal combustion engine is switched off, it can snap into it as soon as the pressure in the pressure chambers falls below a corresponding value. When the locking bolt reaches the end of the elongated hole in the middle position of the impeller, the second locking bolt engages in the fixing hole so that the impeller is locked in both directions of rotation to the drive part. If the one locking bolt is outside the area of the elongated hole, for example in the area in which the greatest adjustment in the late direction is reached, the impeller will move early due to vibrations when the internal combustion engine starts, whereby the one locking bolt engages and locks into the elongated hole Prevents turning back in the late direction so that the other locking bolt can snap into the fixing hole.

The object of the invention is to improve the unlocking and locking of a camshaft adjuster between the end positions of its adjustment range with simple means. It is solved according to the invention by the features of claim 1. Further advantageous embodiments result from the subclaims.

According to the invention, the locking bolt is arranged hydraulically in the flow direction in front of the pressure chambers and releases the inflow in the unlocked position. The locking bolt can either be arranged in front of the control valve or between it and the pressure chambers. It can have various embodiments, e.g. B. it can be designed as a stepped piston and control with its piston step a connecting channel to the pressure chambers or the control valve. Furthermore, the locking bolt can have a second piston stage, which controls a second connecting channel to a pressure chamber for the opposite direction of adjustment, so that the locking bolt flows to the Pressure chambers controls and unlocks whichever of the pressure chambers is acted on.

Instead of a stepped piston, the locking bolt can also be designed as a cylindrical control piston, which forms a pressure chamber with the associated locking bore, which is connected via a central bore to a radial control bore, which controls the connecting channel to the pressure chambers or the control valve. The design of the locking bolt as a cylindrical control piston can be combined with the design as a stepped piston, so that one connecting channel is controlled by the piston step and the other connecting channel is controlled by the radial control bore.

When the internal combustion engine is started or when the camshaft adjuster is activated, an actuation pressure builds up in front of the locking bolt, which unlocks the locking bolt as soon as it overcomes the spring force of the compression spring which loads the locking bolt in the locking direction. In the unlocked state, the inlet to the pressure chambers is released, which within a very short time, for. B. fill within a few milliseconds. The camshaft adjuster responds very quickly to activation on the one hand, since it is already unlocked before the pressure chambers fill. On the other hand, the pressure chambers fill up so quickly that the noises described above are definitely avoided.

Furthermore, the locking bolt is held in the unlocked position by both the actuation pressure and the pressure in the pressure chambers, so that it does not engage during operation, even if the locking position assumes an intermediate position between the end positions and must be overrun when adjusting. If the internal combustion engine is switched off, the actuation pressure and the pressure in the pressure chambers decrease and the locking bolt is released by the Compression spring moved in the locking direction so that it engages in the locking hole.

Since the relative speed of the impeller to the drive part can be very high due to the reaction forces acting on it, a secure locking of the locking bolt is not always guaranteed, especially if the locking position is between the two end positions. It is therefore expedient that the locking device has at least two locking bolts distributed over the circumference, of which at least one cooperates with a catch groove extending in the circumferential direction. When the associated locking bolt is in the engaged state, one end of the catch groove limits the actuating movement of the impeller in the position in which the other locking bolt engages. Due to the extent of the catch groove in the circumferential direction, the associated locking bolt has a larger time window for engaging. In this embodiment, the one locking bolt acts as a catch bolt, which restricts the freedom of movement in the region of the locked position, while the other locking bolt acts as a fixing bolt and prevents the impeller from rotating relative to the drive part in both directions.

According to a further embodiment of the invention, a catch groove is assigned to each locking bolt, the locking bolts resting in the locked position on ends of the catch grooves which are opposite in relation to the adjustment direction. Thus, the impeller to the drive part between the two contact surfaces of the locking bolts is blocked. Furthermore, the safety device acts regardless of the direction of the relative movement between the impeller and the drive part.

In order to control the inflow to the pressure chambers which are assigned to different adjustment directions, the adjustment bolt can be designed in accordance with this double function. If at least two locking bolts distributed over the circumference are provided, it may be expedient that the functions are divided among the locking bolts and that one locking bolt is assigned to the pressure chambers for one adjustment direction and the other locking bolt is assigned to the other pressure chambers.

Further advantages result from the following description of the drawing. Exemplary embodiments of the invention are shown in the drawing. The drawing, the description and the claims contain numerous features in combination. The person skilled in the art will expediently also consider the features individually and combine them into useful further combinations.

Show:

1 shows a schematic cross section through a camshaft adjuster,

2 shows a section along the line II-II in Fig. 1,

3 to 5 variants of FIG. 2,

6 shows two schematic partial longitudinal sections in the area of two mutually associated locking bolts,

Fig. 7 is an orientation sketch for the position of the locking bolt in the adjustment direction of the camshaft adjuster and

8 to 9 variants of FIG. 6.

A camshaft adjuster 10 has a drive part 11 and an impeller 12, which engages with its wings 13, 14 in spaces between the drive part 11. The gaps are formed by radial projections 15, which are located between an inner base circle 16 and an outer circumferential circle 17 extend. On both sides of the wings 13 and 14, pressure chambers 18, 19 are formed between the wings 13 and 14 and the radial projections 15, which can be pressurized with pressure oil by a control valve (not shown). In accordance with the pressure conditions in the pressure chambers 18, 19, the impeller 12 is adjusted relative to the drive part 11 in one adjustment direction 21 or the other adjustment direction 22.

The impeller 12 is rotatably connected to a camshaft, not shown, while the drive part is driven by a crankshaft, also not shown, of an internal combustion engine. An adjustment of the impeller 12 in the adjustment direction 21 means that the gas exchange valves of the internal combustion engine actuated by the camshaft are opened later, while an adjustment in the adjustment direction 22 opens the gas exchange valves earlier.

The drive part 11 has end covers 20 which limit the pressure chambers 18, 19 on the end face. During the breaks in operation, in particular shortly before the start or in the start phase, the impeller 12 is locked in relation to the drive part 11. For this purpose, two locking bolts 23 and 33 distributed over the circumference are used, which cooperate with latching recesses in the form of a locking bore 24 or catch grooves 37 to 41. The locking bolts 23, 31, 32, 33 can be arranged axially or radially in the impeller 12 or drive part 11, the latching recesses being in the other component 11 or 12, respectively. The impeller 12 can be locked to the drive part 11 in an end position in which the vanes 13, 14 rest against a radial projection 15, or as shown in an intermediate position between the two possible end positions.

The locking bolts 23, 31, 32, 33 are arranged hydraulically in the flow direction in front of the pressure chambers 18, 19 and release the inflow in the unlocked position. 2 to Fig. 5 show different versions of locking bolts 23, 31, 32, 33. The locking bolt 23 is formed according to Fig. 2 is designed as a stepped piston with a piston step 26 which is acted upon by an actuating connection 25 with pressure oil while it is in the locking direction by the Spring force 30 of a compression spring is loaded. If the actuation pressure increases in the actuation connection 25, the locking bolt 23 is displaced counter to the spring force 30 and moves out of the locking bore 24. At the same time, a connecting channel 29 is opened, which leads to the pressure chambers 18 or 19 or to a control valve, not shown, which controls the pressure chambers 18, 19.

The embodiment according to FIG. 3 differs from the embodiment according to FIG. 2 in that the locking bolt 31 has a cylindrical circumferential contour and forms a pressure space on the face side with the locking bore 24, which has a central bore 28 and a radial control bore 27 with the actuation connection 25 communicates. If the pressure in the actuation connection 25 rises, the locking bolt 31 is unlocked against the spring force 30 and at the same time opens the flow between the actuation connection 25 and the connecting channel 29.

4 and 5 have two connecting channels 29, 36, of which one 29 z. B. the one pressure chambers 18 and the other connecting channel 36 z. B. is assigned to the other pressure chambers 19. 4, the locking bolt 32 has a piston stage 34 which controls the flow between the actuation port 25 and the connecting channel 29, while the free end of the locking bolt 32 is designed as in the example according to FIG. 3 and a central bore 28 and has a radial control bore 27. This controls the inflow between an actuation connection 35 and the connecting channel 36. In the embodiment according to FIG. 5, the locking bolt 33 has two piston stages 26 and 34, of which the piston stage 26 controls the inflow between the actuation connection 25 and the connecting channel 29, as in the embodiments according to FIGS. 2 and 4. The second piston stage 34 controls the inflow between the actuation connection 35 and the connecting channel 36.

To lock the impeller 12 with respect to the drive part 11, only one locking bolt in the described variants is generally required. If the inflow between two actuation connections 25, 35 to form two connecting channels 29, 36 is to be realized, the embodiments according to FIGS. 4 and 5 can be considered for a locking bolt. If several locking bolts 25, 33 distributed over the circumference are provided, it is possible that one is designed in the embodiment according to FIG. 4 or 5 or that both are designed in the embodiment according to FIG. 2 or 3 and in each case the inflow to the pressure chambers 18 or 19 taxes.

6 to 9 show locking bolts 23, 31 in connection with locking recesses in the form of a locking bore 24 and / or catch grooves 37, 38, 39, 40 and 41. FIG. 7 shows a possible arrangement of the locking bolts 23 and 31 distributed over the circumference. The locking bolt 23 cooperates with the locking bore 24 and acts as a centering bolt which locks the impeller 12 in the locking position in both adjustment directions 21, 22 via the cover 20 of the drive part 11. The second locking bolt 31 cooperates with a catch groove 37. If the impeller 12 moves in the adjustment direction 22 relative to the cover 20, the locking bolt 31 engages in the catch groove 37 under the spring force 30 and blocks the impeller at the end of the catch groove 37. In this position, the centering bolt 23 can snap into the locking bore 24. whereby the impeller 12 is locked in both directions 21, 22. In the embodiments according to FIGS. 8 and 9, a locking groove 38, 39 is assigned to both locking bolts 23, 31. In the embodiment according to FIG. 8, the catch groove 38 limits the relative movement of the impeller 12 in the adjustment direction 22 in the locking position shown, while the catch groove 39 limits the relative movement in the opposite adjustment direction 21. In the embodiment according to FIG. 9, the catch grooves 40 and 41 are arranged such that, in the locked position shown, the locking bolts 23 block the relative movement of the impeller 12 in the adjustment direction 21, while the catch groove 41 limits the relative movement in the opposite adjustment direction 22. The locking bolts 23, 31 can be replaced at will by locking bolts 32, 33 according to FIGS. 4 and 5.

Claims

claims

1. Locking device for a camshaft adjuster, which comprises an impeller rotatably connected to a camshaft, which is rotatably supported in a drive part to a limited extent and engages with its wings from an inner base circle to an outer circumferential circle in spaces which are formed by radial projections of the drive part are, with a pressure chamber being formed in the circumferential direction on both sides of a wing, to which pressure oil can be supplied via a control valve, so that the impeller is adjusted by an angle of rotation relative to the drive part in accordance with the pressure conditions established in the pressure chambers, and the locking device is at least has a hydraulically unlockable locking bolt loaded in a locking direction by a compression spring, each of which cooperates with a locking recess and which couples the impeller in a locked position to the drive part t that the locking bolt (23, 31, 32, 33) is arranged hydraulically in the flow direction in front of the pressure chambers (18, 19) and releases the inflow in the unlocked position.

2. Locking device according to claim 1 d a d u r c h g e k e n n z e i c h n e t that the locking bolt (23, 31, 32, 33) is arranged in front of the control valve.

3. Locking device according to claim 1, characterized in that the locking bolt (23, 31, 32, 33) is arranged between the control valve and the pressure chambers (18, 19).

4. Locking device according to one of the preceding claims, that the locking bolt (23, 32, 33) is designed as a stepped piston and controls a connecting channel (29) to the pressure chambers (18, 19) or the control valve with a piston step (26). (Fig. 2)

5. Locking device according to claim 4, so that the locking bolt (33) has a second piston stage (34) which controls a second connecting channel (36) to a pressure chamber (18, 19) for the opposite actuating direction. (Fig. 5)

6. Locking device according to one of claims 1 to 3, characterized in that the locking bolt (31) is designed as a cylindrical control piston which, with the associated snap-in recess (24, 31, 32, 33), forms a pressure chamber which has a central bore (28 ) is connected to a radial control bore (27) which controls the connecting channel (29, 36) to the pressure chambers (18, 19) or the control valve. (Fig. 3)

7. Locking device according to claim 4, characterized in that the locking bolt (32) is formed at the end facing the latching recess (24) as a cylindrical control piston which forms a pressure chamber with the latching recess (24, 31, 32, 33), which via a central bore (28) with a radial control bore (27) is connected, which controls the second connecting channel (36) to the pressure chambers (18, 19) or the control valve. (Fig. 4)

8. Locking device according to one of the preceding claims, characterized in that it has at least two locking bolts (23, 31) distributed over the circumference, of which at least one cooperates with a circumferentially extending catch groove (37 to .41), one end of which in engaged state of the associated locking bolt (31) limits the actuating movement of the impeller (12) in the position in which the other locking bolt (23) engages in the associated latching recess (24, 31, 32, 33). (Figs. 6 to 9)

9. Locking device according to claim 8, characterized in that each locking bolt (23, 31) is assigned a catch groove (38, 39; or 40, 41) and the locking bolt (23, 31) in the locked position at the ends of the catch grooves (38 and 39; 40 and 41), which are opposite in relation to the adjustment direction (21, 22). (Fig. 8 and Fig. 9)

10. Locking device according to claim 8 or 9, so that the locking bolts (23, 31) are each associated with pressure chambers (18, 19), each of which is assigned to an adjustment direction (21, 22).