Hydraulic camshaft adjuster and method for assembling the same

Abstract

In a hydraulic camshaft adjuster for a camshaft of an internal combustion engine and a method of assembling the camshaft adjuster, with an inner body, which is connected to the camshaft in a rotationally fixed manner and has outwardly extending blades and an outer body which is mounted rotatably with respect to the camshaft and has inwardly projecting blades which form, together with the outwardly extending blades, at least one hydraulic medium chamber between two covers connected to the outer body which is operatively connected to a crankshaft of an engine so as to be driven thereby, and a locking device for locking the inner body in relation to the outer body by at least one bolt which is mounted in the inner body so as to extend into a locking cavity in one of the two covers, the camshaft adjuster has a base stop, and the locking cavity has an assembly stop providing for reliable assembly of the camshaft adjuster with minimal locking play and without the need for an adjusting procedure.

Description

BACKGROUND OF THE INVENTION

The invention relates to a hydraulic camshaft adjuster and to a method of assembling the same for a camshaft of an internal combustion engine, comprising an inner body, which is connected to the camshaft in a rotationally fixed manner and has outwardly extending blades and an outer body, which is mounted rotatably relative to the camshaft and has blades extending inwardly between the outwardly extending blades so as to form at least one hydraulic medium chamber between two opposite cover plates, a driving connection from a crankshaft to the outer body, and with a locking device which locks the inner body in relation to the outer body with at least one bolt, which is movably disposed in the inner body for engagement in a locking cavity in one of the two covers, which are connected to the outer body.

In order to reduce the fuel consumption and the emissions and to increase power and torque, spark-ignition engines are generally equipped with camshaft adjusters. The latter change the phase position of the camshaft relative to the crankshaft. Currently, hydraulic blade-type adjusters with working chambers are generally used. The adjustment is undertaken by the controlled admission of oil from the engine circuit via a control valve into the chambers formed between adjacent blades. The control valve is operated by an electromagnetic control device.

DE 102 53 496 A1 discloses a camshaft adjuster of the generic type and is intended for adjusting the angle of rotation of the camshaft in relation to a crankshaft of an internal combustion engine. The camshaft adjuster has an outer body which is connected in a rotationally fixed manner to a drive wheel and an inner body which is connected in a rotationally fixed manner to the camshaft, the outer body having at least one hydraulic chamber and the inner body having at least one rotor blade which divides the hydraulic chamber into two working chambers. The rotor blade can be moved hydraulically between a late stop and an early stop by means of a controlled oil pressure. One of the stops forms the base position in which the blade can be locked by means of a spring-loaded locking pin which can be released hydraulically and which is moved into a locking groove or bore for locking purposes. The locking pin prevents an undesired movement of the camshaft adjuster if no oil pressure is present. These locking pins have a locking play in the locking grooves caused by the sum of the tolerances, some play being necessary for reliable functioning of the lock. The locking play should be large enough such that reliable locking and release operation can be obtained, but small enough to avoid the generation of noise. The generation of noise results from the undamped striking contact of a rotor blade and early stop or late stop, on the one hand, and the locking pin entering the locking groove, on the other hand. The aim of obtaining a quiet engine and a reliably operating lock can generally only be achieved by means of an exacting tolerance of the locking play. However, this exacting tolerance not only has technological limits for adjusting the locking play but moreover monitoring this adjusting operation by continuously measuring the locking play is very costly.

It is the principle object of the present invention to provide a hydraulic camshaft adjuster and a method for assembling the same in such a manner that reliable assembling of the camshaft adjuster with minimal locking play and without an adjusting process is possible.

SUMMARY OF THE INVENTION

In a hydraulic camshaft adjuster for a camshaft of an internal combustion engine and a method of assembling the camshaft adjuster, with an inner body, which is connected to the camshaft in a rotationally fixed manner and has outwardly extending blades and an outer body which is mounted rotatably with respect to the camshaft and has inwardly projecting blades which form, together with the outwardly extending blades, at least one hydraulic medium chamber between two covers connected to the outer body which is operatively connected to a crankshaft of an engine so as to be driven thereby, and a locking device for locking the inner body in relation to the outer body by at least one bolt which is mounted in the inner body so as to extend into a locking cavity in one of the two covers, the camshaft adjuster has a base stop, and the locking cavity has an assembly stop providing for reliable assembly of the camshaft adjuster with minimal locking play and without the need for an adjusting procedure.

A substantial advantage of the camshaft adjuster according to the invention is that an adjusting device for adjusting the locking play between the bolt and the locking cavity is not necessary for the assembly of the camshaft adjuster. Even minimal locking plays can be reliably provided. The shape of the cavity depends on the result to be achieved. The shape may be a bore for simple manufacture. The shape of the cavity may also be designed in such a manner that the stop edges of the base stop and installation stop point radially with respect to the axis of rotation of the camshaft adjuster in order, in the case of larger radial tolerances, to provide the same locking plays. The shape of the cavity may be designed in such a manner that both stop edges are parallel to each other and possibly also parallel to a virtual line extending radially with respect to the axis of rotation of the camshaft adjuster in order to permit the use a simple gauge test for quality assurance.

The invention will become more readily apparent from the following description of two exemplary embodiments with reference to the accompanying drawings:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a view from above of the camshaft adjuster according to the invention with an inner body arranged in an outer body and a locking device, in which a locking bolt and a compression spring are introduced into a bore, with the bodies being at a base stop,

FIG. 2 shows the camshaft adjuster according to FIG. 1, in which a drive wheel in the form of a first cover and provided with a gear structure on its outer circumference is placed onto it,

FIG. 3 shows the camshaft adjuster according to FIG. 2 in a view from below, in which, by rotation of the drive wheel, the bolt is introduced into a cavity formed in the drive wheel,

FIG. 4 shows the camshaft adjuster according to FIG. 3, in which the bolt is rotated onto an installation stop in the cavity by joint rotation of the inner body and the outer body in relation to the drive wheel,

FIG. 5 shows the camshaft adjuster according to FIG. 4, in which a second cover is placed onto the camshaft adjuster,

FIG. 6 shows the camshaft adjuster according to FIG. 5 with a second cover screwed onto the camshaft adjuster,

FIG. 7 shows the camshaft adjuster in a locked position, the camshaft adjuster being illustrated broken open in the region of the locking device,

FIG. 8 shows the camshaft adjuster in a side view with a partial section in the region of the locking device,

FIG. 9 shows the partial section in an enlarged illustration, and

FIG. 10 shows the locking gate.

DESCRIPTION OF THE PARTICULAR EMBODIMENTS

For the sake of simplicity, the same reference numbers are used for corresponding components in the figures. Furthermore, for identical components, only one element in each case is indicated as an example.

FIGS. 1 to 10 show a hydraulic camshaft adjuster 1 for adjusting a camshaft (not illustrated) in relation to a crankshaft (likewise not illustrated) of an internal combustion engine. According to FIG. 1, the camshaft adjuster 1 has two transmission parts 2, 3 which can be rotated relative to each other for the adjustment, an inner body 2 connected in a rotationally fixed manner to the camshaft, and an outer body 3 mounted rotatably with respect to the camshaft. The transmission parts 2, 3 are arranged between a first cover 4 (FIG. 2) and a second cover 5 (FIG. 5). The outer part 3 is connected in a rotationally fixed manner to the first cover 4, which is in the form of a drive wheel, the drive wheel 4 having, on its outer circumference, a gear structure 6 which is either formed integrally with the drive wheel 4 or is separate and is connected fixedly to the drive wheel 4, via which the camshaft is driven by the crankshaft of the internal combustion engine. As an alternative to this, the gear structure 6 may also be arranged directly on the outer body 3. Instead of the toothed wheel drive indicated and discussed here, other drive connections, such as toothed belt drives or chain drives, may be provided.

According to FIG. 1, the sleeve-shaped outer body 3 which surrounds the camshaft has inwardly projecting blades 7, 7.1 which have bores 8 for receiving fastening screws. The inner body 2 which is fastened in a rotationally fixed manner to the camshaft has outwardly projecting mating blades 9, 9.1. Both the blades 7 of the outer body 3 and the mating blades 9 of the inner body 2 respectively have at least one seal 10, 11 on their circumferences. The inner body 2 and the outer body 3 together with the two covers 4, 5 form at least one hydraulic medium chamber 12 which is divided by the particular mating blade 9, 9.1 into two working chambers 12a and 12b, only one gap (FIG. 3) of the working chamber 12b being visible in the illustrated position of the camshaft adjuster 1.

In order to be able to transmit the driving torque of the crankshaft to the camshaft, the inner body 2 of the camshaft adjuster 1 is connected, as already mentioned, in a rotationally fixed manner to the camshaft. The driving torque is introduced by the outer body 3 into the camshaft adjuster 1 and is transmitted via the working chambers 12a, 12b to the inner body 2. The phase position between outer body 3 of the camshaft adjuster 1 and camshaft can be adjusted by varying the hydraulic medium filling of the working chambers 12a and 12b. A control valve (not illustrated here) controls the hydraulic medium supply to the camshaft adjuster 1 and therefore the phase position or the changing thereof.

The camshaft adjuster has a locking mechanism which can be acted upon hydraulically and comprises bolt 13 and compression spring 14. The locking mechanism provides for a fixed connection between inner body 2 and outer body 3 by axial movement of the bolt 13. The bolt hole which is preferably arranged in a blade 9.1 of the inner body 2 and into which the bolt 13 is introduced together with the spring 14 is denoted by the numeral 15. The spring 14 being supported, in the case of a bolt hole 15 designed as a blind hole bore, on one side on the bottom of the bolt hole 15 and on the other side on the end side of the bolt 13. In the case where a bolt hole 15 is designed as a continuous bore closed by a cover, the spring 14 is supported, on the one hand, on the cover and, on the other hand, on the bolt 13. According to FIGS. 3 to 7, the drive wheel 4, which is in the form of a cover, has a cavity 16 in which the bolt 13 engages in the locked state. The cavity 16 is formed in one of the two covers 4, 5 depending in each case on the configuration of the locking device, the cavity 16 either being fastened as a separate part to the cover 4, 5 or being molded into the cover 4, 5, i.e. being formed integrally with the cover 4, 5. According to FIG. 10, the cavity 16 has a cross section 16a for receiving the bolt 13 and a cross section 16b designed as a release channel. In order to release, i.e. to eliminate, the fixed connection between inner body 2 and outer body 3, the bolt is acted upon by a pressure medium in a specific manner so as to counteract the spring force via the release channel 16b so that an adjustment procedure can be initiated.

FIGS. 8 and 9 show a further refinement of the locking device, in which the bolt 13′ arranged in the bolt hole 15′ is designed in the manner of a cup and accommodates at least part of the compression spring 14′ in its interior. At an end disposed opposite the cavity 16, the bolt hole 15′ has a release bore 21.

FIGS. 1 to 6 show the assembly of the hydraulic camshaft adjuster 1. The view from above according to FIG. 1 shows the inner body 2 disposed with one of its mating blades 9.1 at the stop of a locking position 17 and the outer body 3 disposed with one of its blades 7.1 abutting the stop. The locking position 17 can be seen clearly in FIGS. 3 and 4, since (only here) blade 7.1 and mating blade 9.1 bear against each other while a gap 18 can be seen between the remaining pairs of blade/mating blade. The base stop 17 prevents an undesired movement of the camshaft adjuster 1 if there is no pressure medium pressure present. The bolt 13 is introduced together with the compression spring 14 into the bolt hole 15 which is arranged in the inner body 2 and is a blind hole bore, with first the compression spring 14 and subsequently the bolt 15 being inserted, as a result of which the compression spring 14 bears against the bottom of the blind bore 15. The camshaft adjuster 1 is still situated here in a released position.

According to FIG. 2, the drive wheel which in the form of a first cover 4 is subsequently placed on with its gear structure 6 arranged on the outer circumference, the camshaft adjuster 1 still being in the released position.

The view from below according to FIG. 3 shows that, after the drive wheel 4 has been placed on, the bolt 13 is introduced into the cavity 16 by rotating the drive wheel 4 in the clockwise direction or counterclockwise, with the camshaft adjuster 1 now being in a preliminarily locked position.

According to FIG. 4, the bolt 13 in the assembly including the inner body 2 and the outer body 3 is now rotated in relation to the drive wheel 4 (counterclockwise) onto an installation stop 19, which is visible in FIG. 10, and is held by the spring pressure of the compression spring 14. In this position, the camshaft adjuster 1 is in a finally locked position and the second cover 5 can be positioned in accordance with FIG. 5 by fastening screws 20 being inserted through the bores 8 and screwed to the inner body 2. FIG. 6 shows the screwed cover 5 and therefore the “fixing” of the assembly state.

In the case of this locking device, the maximum possible locking play S is primarily formed by the clearance width W in the cavity 16a minus the diameter D of the bolt 13. Shape and position tolerances of the components and the centering accuracy also have an effect on the locking play. The installation stop 19 is designed in such a manner that, during installation, the inner body 2 is rotated with the locking bolt 13 onto the installation stop 19 and at the same time the inner body 2 and the outer body 3 are disposed at the common stop, the base stop 17. This ensures that, from this position, the locking play S is predominantly formed only by the distance between the two stops 17 and 19.

FIG. 7 shows the camshaft adjuster according to FIG. 6 but in an inverted position, with the region of the locking device being illustrated broken open for better understanding. As already mentioned above, the inner body 2 and the outer body 3 sit on the common base stop 17 and the bolt 13 bears against the installation stop 19. The inner body 2 can now be rotated in the counterclockwise direction by the locking play S, which means that the camshaft adjuster 1 can already be locked before the inner body bears against the base stop 17.

Claims

1. A hydraulic camshaft adjuster (1) for a camshaft of an internal combustion engine, comprising an inner body (2) which is connected to the camshaft in a rotationally fixed manner and has outwardly extending blades (9, 9.1) and an outer body (3) which is mounted rotatably with respect to the camshaft and has inwardly extending blades (7, 7.1) mating with the outwardly extending blades so as to form at least one hydraulic medium chamber (12) between adjacent blades and two cover plates (4, 5) connected to the outer body (3), a driving connection from a crankshaft to the camshaft extending to the outer body (3), and a locking device which locks the inner body (2) in relation to the outer body (3) by at least one bolt (13) which is movably disposed in the inner body (2) for engagement in a locking cavity (16) in one of the two cover plates (4, 5), the camshaft adjuster (1) having a base stop (17), and the locking the cavity (16) additionally having an assembly stop (19).

2. The hydraulic camshaft adjuster as claimed in claim 1, wherein the installation stop (19) acts in the direction of the base stop (17) concurrently with the latter.

3. The hydraulic camshaft adjuster as claimed in claim 1, wherein the cavity (16) is arranged in one of the covers (4, 5).

4. The hydraulic camshaft adjuster as claimed in claim 1, wherein the locking cavity (16) is arranged in the drive wheel (4).

5. The hydraulic camshaft adjuster as claimed in claim 1, wherein the cavity (16) has a cross section (16a) for receiving the locking bolt (13) and a cross section (16b) forming a release channel.

6. The hydraulic camshaft adjuster as claimed in claim 5, wherein the bolt (13) can be acted upon by a pressure medium in order to be released via the release channel (16b).

7. The hydraulic camshaft adjuster as claimed in claim 4, wherein the cross section (16a) of the cavity (16) for receiving the bolt (13) is trapezoidal or has parallel stops.

8. The hydraulic camshaft adjuster as claimed in claim 1, wherein the locking cavity (16) is formed by hard or hardened material.

9. The hydraulic camshaft adjuster as claimed in claim 8, wherein a hard or hardened bushing is disposed in the cross sectional area (16a) formed by a bore.

10. The hydraulic camshaft adjuster as claimed in claim 1, wherein the maximum possible locking play (S) is provided essentially by the clear width (W) in the cavity (16a) minus the diameter (D) of the bolt (13).

11. A method for installing a hydraulic camshaft adjuster (1) for a camshaft of an internal combustion engine, comprising an inner body (2) connected to the camshaft in a rotationally fixed manner and having outwardly projecting blades (9, 9.1) and an outer body (3) which is mounted rotatably with respect to the camshaft and having blades (7, 7.1) projecting inwardly into spaces between the outwardly projecting blades (9, 9.1), both being arranged between two cover plates (4, 5) connected to the outer body (3) and being lockable in relation to each other by at least one locking bolt (13) which is mounted in the inner body (2) and extends into a locking cavity (16) in one of the two covers (4, 5), the camshaft adjuster (1) further having a base stop (17), said method comprising the steps of moving, during assembly, the locking bolt (13) onto an assembly stop (19) arranged in the locking cavity (16).

12. The method as claimed in claim 11, wherein the inner body (2) and the outer body (3) are concurrently rotated to the base stop (17).

13. The method as claimed in claim 11, wherein starting from the position of the locking bolt (13) on the assembly stop (19) and the inner body (2) and the outer body (3) on the base stop (17), a locking play (S) is formed by a clear width (W) in the cavity (16a) minus the diameter (D) of the bolt (13).

14. The method as claimed in 13, wherein, in the locked position of the camshaft adjuster (1), the inner body (2) can be rotated in the direction counter to the installation stop (19) by a distance corresponding to the locking play (S).

15. The method as claimed in claim 11, wherein, for installation, the components (2, 3, 4) of the preassembled camshaft adjuster (1) are positioned in such a manner that the mating blade (9.1) of the inner body (2) and the blade (7.1) of the outer body (3) abut the base stop (17) and at the same time the bolt (13) abuts in the cavity (16) the installation stop (19), this state being fixed by the cover (5) being fitted.

16. The method as claimed in claim 11, comprising the following steps: for assembly a) moving the inner body (2) with its mating blade (9.1) into contact with the base stop (17) and the outer body (3) lies with its blade (7.1) into contact with the base stop (17), b) introducing the bolt (13) and the compression spring (14) into the bolt hole (15) arranged in the inner body (2), c) placing the first cover (4), which is in the form of a drive wheel, onto the two bodies (2, 3), d) inserting the bolt (13) into the cavity (16) by rotating the drive wheel (4) backward or forward, e) rotating the bolt (13) together with the inner body (2) and the outer body (3) in relation to the drive wheel (4) so as to engage the installation stop (19) in the cavity (16), f) placing the second cover (5) onto the two bodies (2, 3) and, in this position, g) screwing the second cover (5) to the camshaft adjuster (1).