ADJUSTABLE CAMSHAFT

An adjustable camshaft for an internal combustion engine includes an outer shaft and a support shaft defining at least one bore with a relief groove configured outside of the bore. The support shaft extends along a longitudinal axis. The outer shaft may include a cam element disposed on the support shaft such that the outer shaft is displaceable along the support shaft along the longitudinal axis wherein the outer shaft is latchable on the support shaft in at least two axial latching positions. A biasing means, a press-fit retainer, and a latching element are disposed within the bore such that the biasing means urges the latching element toward any one recess of the plurality of recesses defined in the outer shaft.

TECHNICAL FIELD

The present disclosure relates to a valve operating device for an engine of a vehicle, particularly a valve operating device which switches a cam for opening and closing a valve.

BACKGROUND

Adjustable camshafts for internal combustion engines having a support shaft which extends in a longitudinal axis are known, and at least one outer shaft which is received on the support shaft such that it can be moved in the direction of the longitudinal axis. The outer shaft rotates with the rotation of the support shaft, for which purpose a splined structure between the support shaft and the outer shaft can serve, and a rotation of the outer shaft on the support shaft is prevented by way of the spline structure. In order to latch the outer shaft in discrete, reproducible axial positions on the support shaft, latching elements may be provided which can be prestressed by way of biasing a means, and the latching elements can latch into latching element receptacles, as a result of which, the axial position of the outer shaft on the support shaft may then be defined. The different axial positions of the outer shaft on the support shaft serve to bring the different cam elements of the outer shaft into connection with valves or tapping elements for actuating valves. The different cam elements can define different control times for opening and closing the valves of the internal combustion engine, or the valve stroke can be changed by way of different cam elements in operative connection with a tapping element or directly with a valve.

The change takes place by way of different, discrete axial positions of the outer shaft being assumed on the support shaft, and the displacement of the outer shaft takes place, for example, by way of a manipulation means which is received in a stationary manner in the cylinder head and can interact with an adjusting element which can likewise be included by the outer shaft.

For example, DE 10 2010 011 897 A1 discloses an adjustable camshaft for an internal combustion engine having a support shaft which extends in a longitudinal axis, and an outer shaft is received on the support shaft such that it can be moved axially. A latching element in the form of a ball which is loaded by way of a spring force of a biasing means serves to latch the outer shaft in discrete axial positions. The ball can latch into different profile grooves defined in lobe back as a result of the spring force, and the profile grooves are arranged with regard to the axial position in such a way that each profile groove corresponds to the contact of an associated cam track of a cam element against a tapping element.

However, a traditional adjustable camshaft as described above presents assembly issues in that the outer shaft must be installed on the support shaft adjacent to receptacle on the support shaft when the latching element and spring are assembled onto support shaft given that the outer shaft is used to prevent the ball and spring from falling out of the receptacle on the support shaft. As a result, the support shaft must have an extended length so as to accommodate the outer shaft on the support shaft when the ball and spring are installed onto the support shaft to enable the outer shaft to then immediately slide over the ball and spring in order to retain the ball and spring in the support shaft.

SUMMARY

The present disclosure provides an adjustable camshaft for an internal combustion engine. The adjustable camshaft includes an outer shaft and a support shaft which defines at least one bore with a relief groove configured outside of the bore. The support shaft extends along a longitudinal axis. The outer shaft may include a cam element disposed on the support shaft such that the outer shaft is displaceable along the support shaft along the longitudinal axis wherein the outer shaft is latchable on the support shaft in at least two axial latching positions. A biasing means, a press-fit retainer, and a latching element are disposed within the bore such that the biasing means urges the latching element toward any one recess of a plurality of recesses defined in the outer shaft. The latching element may or may not be provided in the form of a detent ball.

In various embodiments of the present disclosure, the relief groove may be configured as one of a straight groove, a semi-circle groove, and a full-circle groove. The relief groove defines a groove depth which may vary along the length of the relief groove or which may be fixed along the length of the relief groove. Regardless of whether the groove depth varies along the relief groove length or the groove depth is fixed along the relief groove length, the groove depth may fall in a depth range of about 1.5 mm to about 6 mm. Similarly, regardless of the fixed or varying nature of the relief groove depth, the relief groove may also define a groove width which falls in a width range of about 1.5 mm to about 6 mm. The groove width also may be fixed or may vary along the length of the relief groove. With respect to the aforementioned relief groove, the associated bore for the aforementioned relief groove may define a bore diameter which falls in a diameter range of about 8 mm to about 16 mm.

The manufacturing method includes the steps of: (1) providing a support shaft with a bore and a relief groove defined in the support shaft; (2) inserting a biasing means into a lower region of the bore: (3) inserting a latching element into the bore such that the latching element is adjacent to an upper end the biasing means: (4) press-fitting a press-fit retaining ring in an upper region of the bore so that the latching element is disposed in an aperture defined by the press-fit retaining ring; (5) positioning the outer shaft onto the support shaft so that the latching element may be disposed in one of a plurality of detent positions defined on the outer shaft.

The relief groove of the aforementioned support shaft is defined outside of the at least one bore such that the relief groove is configured to reduce cam shaft deflection along a longitudinal axis of the cam shaft when the press-fit retaining ring is inserted into the upper region of the at least one bore. The relief groove may be configured as one of a full-circle groove, semi-circle groove, straight groove and a circumferential groove.

The present disclosure and its particular features and advantages will become more apparent from the following detailed description considered with reference to the accompanying drawings.

DETAILED DESCRIPTION

Reference will now be made in detail to presently preferred compositions, embodiments and methods of the present disclosure, which constitute the best modes of practicing the present disclosure presently known to the inventors. The figures are not necessarily to scale. However, it is to be understood that the disclosed embodiments are merely exemplary of the present disclosure that may be embodied in various and alternative forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for any aspect of the present disclosure and/or as a representative basis for teaching one skilled in the art to variously employ the present disclosure.

It is also to be understood that this present disclosure is not limited to the specific embodiments and methods described below, as specific components and/or conditions may, of course, vary. Furthermore, the terminology used herein is used only for the purpose of describing particular embodiments of the present disclosure and is not intended to be limiting in any way.

The phrase “consisting of” excludes any element, step, or ingredient not specified in the claim. When this phrase appears in a clause of the lifter body14of a claim, rather than immediately following the preamble, it limits only the element set forth in that clause; other elements are not excluded from the claim as a whole.

The terms “comprising”, “consisting of”, and “consisting essentially of” can be alternatively used. Where one of these three terms is used, the presently disclosed and claimed subject matter can include the use of either of the other two terms.

With reference toFIG. 1A, a vehicle engine (not shown) may include a shifting actuator54and an actuator pin56connected to the actuator54. The actuator pin56may be cylindrical, as shown, or may be any other suitable shape. The shifting actuator54may move the actuator pin56into contact with the shifting feature52(FIG. 1B) when in an actuated state and may withdraw the actuator pin56from contact with the shifting feature52when in an unactuated state. The actuator pin56may cooperate with the shifting feature52to move the outer shaft24axially (longitudinal axis14arrow A) to the respective axial position40A,40B,40C (FIG. 1A) that corresponds to the selected one of the plurality of selectable cams36A,366,36C (FIG. 1B) when the shifting actuator54is in the actuated state. It is understood that, inFIG. 1A, the outer shaft24is in axial position40A. There may be more than one shifting feature52and more than one actuator pin56, as shown. The outer surface34of the outer shaft24is subjected to actuator loading in the region between the shifting feature52and the actuator pin56.

The adjustable camshaft10is for shifting to a selected one or more selectable cam lobes36A,368,36C (FIG. 1B). The adjustable camshaft10includes an inner shaft22and an outer shaft24. The adjustable camshaft10may include one or more outer shaft24. The inner shaft22has an external spline26. The outer shaft24has an inner surface28(FIG. 1A) configured with an internal spline30(FIG. 1A) for transferring a torque from the external spline26of the inner shaft22and for sliding axially (longitudinal axis14arrow A) on the external spline26of the inner shaft22.

Referring toFIG. 1B, the cam follower mechanism44of the engine (not shown) connects the valve42to the selected cam lobe shown as element36A inFIG. 1Bso as to open and close the valve42according to the respective cam profile (shown as38A inFIG. 1B). The cam follower mechanism44may be a roller finger follower, as shown and as understood to those skilled in the art, or may be any other suitable cam follower mechanism. The cam follower mechanism44includes a cam follower46. The cam follower46may be a roller, as shown, or may be any other type of cam follower. A valve spring48may be connected to the valve42and may bias the valve42to urge the valve42toward a closed position (not shown) in an engine cylinder (not shown) and toward the selected cam lobe (shown as36A). The outer surface34of the outer shaft24is subjectable to both wear and valve loading (arrow FV) at a second interface50between the cam lobes36A,36B,36C and the cam follower46.

As shown inFIG. 1A, the outer shaft24has an outer surface34. As shown inFIG. 1B, the outer surface34is configured with the one or more selectable cam lobes36A,36B,36C that have respective cam profiles38A,38B,38C and that correspond to respective axial positions40A,40B,40C of the outer shaft24relative to the inner shaft22. The selected cam lobe (shown as36A inFIG. 1B) and its respective cam profile (shown as38A inFIG. 1B) is selected by locating the outer shaft24at the respective axial position (shown as40AFIG. 1B).

The inner surface28of the outer shaft24may be configured with a locating feature74in the form of a plurality of recesses75for temporarily locating the outer shaft24at the respective axial position40A,40B,40C relative to the support shaft22that corresponds to the selected one of the plurality of selectable cam lobes36A,36B,36C. The adjustable camshaft10may include a detent mechanism60which may further include a biasing means70(such as a spring) and a detent ball72(or latching element)72.

With reference toFIG. 3, during the assembly process of the adjustable camshaft10of the present disclosure, it is understood that the biasing means70, a press-fit retainer18ring, and a latching element72are inserted into the bore12of the support shaft22wherein the latching element (ball) is disposed in the press-fit retainer18ring at the upper region of the bore12. The press-fit retainer18maintains the latching element (detent ball72) in position within the bore12of the support shaft22during the assembly process. Accordingly, the use of the press-fit retainer18of the present disclosure obviates the need to install the outer shaft24on an end region of a support shaft before or during the installation process of the biasing means70and the latching element into the support shaft22.

Under traditional adjustable camshaft10designs (not shown), the outer shaft24(having the cam pack) was immediately moved from its “stored” position on the end of the support shaft22to the region of the support shaft22which defined the bore12as soon as the detent ball72or latching element was assembled within the bore12. This assembly step was necessary to prevent the detent ball72or latching element from inadvertently falling out of the bore12in the support shaft22. In light of the present disclosure's implementation of the press-fit retainer18ring, the assembly process is improved given that there is no longer a risk of the detent ball72falling out of the support shaft22given that the detent ball72or latching element maintains position within the bore12during the assembly process without the aid of the outer shaft24. As a further benefit, the support shaft22length may be shortened given that the region for only supporting the outer shaft24in the assembly process is no longer needed. Again, previously, the assembly process required that the outer shaft24be readily moved over the biasing means70and latching element upon inserting the detent ball72and biasing means70in the bore12.

However, it is also understood that a traditional support shaft22may experience excessive shaft bending and axial run-out due to the stresses imposed on the support shaft22by the retainer18ring. Referring now toFIG. 4, the retainer ring18′ imposes stresses92′ on the traditional support shaft22′ so as to cause the support shaft22′ to bend or deflect as shown inFIG. 4. Under the undesirable condition shown inFIG. 4, the region of the support shaft22′ which surrounds the press fit retainer ring18′ absorbs the energy and deflects along the longitudinal axis14A-A of the support shaft22′. The undesirable bending in the support shaft22′ may then cause the support shaft22′ to rotate off center.

Accordingly, in order to reduce shaft bending (shown inFIG. 4) and axial run out, the present disclosure provides for an improved adjustable camshaft10which experiences reduced deflection and reduced axial run-out. The adjustable camshaft10of the present disclosure may be implemented in an internal combustion engine wherein the adjustable camshaft10includes an outer shaft24with a cam pack and a support shaft22which defines a bore12with a relief groove16(FIGS. 2A-2E,FIGS. 3 and 5) configured outside of the bore12. The support shaft22extends along a longitudinal axis14(A-A). The outer shaft24is displaceable along the length of the support shaft22(along the longitudinal axis14) in example positions40A,40B,40C wherein the outer shaft24is latchable on the support shaft22in at least two axial latching positions. A biasing means70, a press-fit retainer18, and a latching element may be disposed within the bore12such that the biasing means70urges the latching element (or detent ball72) toward any one recess of a plurality of recesses defined in the outer shaft24. The biasing means70may or may not be in the form of a spring as shown inFIG. 1. Moreover, as further shown inFIG. 1, each recess in the plurality of recesses enables the outer shaft24to move between three different positions.

As shown inFIGS. 1A and 3, the biasing means70may be disposed within the bore12of the support shaft22. The biasing means70may be a coil spring, as shown, or any other suitable biasing means70. As shown inFIG. 1A, the detent ball72may be disposed between the biasing means70/support shaft22on one side of the detent ball72and the outer shaft24on the other side of the detent ball72. The biasing means70applies a radially outward biasing force on the detent ball72. The locating feature74(FIG. 1A) may be a circumferential detent groove with multiple recesses75, as shown, which is formed on the inner surface28of the outer shaft24. The locating feature74may be configured to temporarily locate the outer shaft24at the respective axial position40A,40B,40C relative to the support shaft22by engaging the detent ball72of the detent mechanism60.

With reference to the aforementioned relief groove16defined outside of the bore12, the relief groove16is defined on the outer surface of the support shaft22and may be configured in different ways. Non-limiting example configurations for the relief groove16may be a full-circle relief groove37(FIGS. 2A-2B), a semi-circle relief groove38(FIG. 2C), a straight relief groove40(FIG. 2D) or a circumferential relief groove40(FIG. 2E). The circumferential relief groove shown inFIG. 2Emay have a length which travels about the entire circumference of the support shaft or the circumferential relief groove may have a length which is less than the circumference of the support shaft thereby making such a groove a partial circle. It is understood that an intermediate region80is also defined on the support shaft22wherein the intermediate region80is defined as the region of the support shaft22which is disposed between the bore12and relief groove16. The intermediate region80is therefore the region of the support shaft22which is defined between the upper end of the bore12and the relief groove16as shown inFIGS. 2A-2E, 3 and 5. Therefore, regardless of which form the relief groove16takes, the relief groove16and the intermediate region80associated with the relief groove16are configured to absorb structural loads imposed by the press-fit retainer18ring on the support shaft22such that the deflection of the support shaft22is significantly limited to the intermediate region80of the support shaft22. It is understood that the intermediate region80of the support shaft22is the region of the support shaft22which is defined between the upper end of the bore12and the relief groove16.

In the various embodiments of the present disclosure, the groove depth20of the relief groove16may vary or may be fixed along a length27of the relief groove16. Regardless of whether the groove depth20is fixed or varies along the length27of the relief groove16, the groove depth20may fall in a depth range of about 1.5 mm to about 6.0 mm. It is also understood that regardless of whether the groove depth20is fixed or varies along the length27of the relief groove16, the relief groove width31may also be fixed or may vary along the length27of the relief groove16. Regardless of whether the groove width31is fixed or varies, the relief groove16may define a groove width31which falls in a width range of about 1.5 mm to about 6 mm. Referring now toFIGS. 2A, 2C-2E, and 3, the support shaft22bore12of various example embodiments may, but not necessarily, have a bore diameter32which falls in a diameter range of about 8 mm to about 16 mm.

With reference toFIG. 6of the present disclosure, a flowchart90is shown which illustrates an example, non-limiting method for manufacturing an adjustable camshaft10in accordance with the present disclosure. The manufacturing method includes the steps of: (1) providing a support shaft with a bore and a relief groove defined in the support shaft; step44(2) inserting a biasing means into a lower region of the bore; step46(3) inserting a latching element into the bore such that the latching element is adjacent to an upper end the biasing means; step48(4) press-fitting a press-fit retaining ring in an upper region of the bore so that the latching element is disposed in an aperture defined by the press-fit retaining ring; step50(5) positioning the outer shaft onto the support shaft so that the latching element may be disposed in one of a plurality of detent positions defined on the outer shaft24. Step51

It is understood that, in the aforementioned method to manufacture an adjustable camshaft10, the relief groove16is defined outside of the at least one bore12such that an intermediate region80of the support shaft22is defined between the relief groove16and the bore12. The relief groove16is configured to reduce the support shaft deflection along a longitudinal axis14of the cam shaft. The relief groove16may be provided in various forms. Example, non-limiting configurations include is configured as one of a full-circle37groove, semi-circle groove, a straight groove and a circumferential groove. The latching element72(detent ball72) and the biasing means70for loading the latching element72with force may be arranged in a receiving bore12of the support shaft22as illustrated inFIG. 1A. Furthermore, as illustrated inFIG. 1A, recesses75or latching element receptacles75may be defined on the inner side in the outer shaft24in the form of the profile grooves.

If the camshaft10has to be assembled, first of all the biasing means70has to be inserted into the receiving bore12in the camshaft10, and subsequently the latching element (ball) has to be inserted into the receiving bore12counter to the spring force before the outer shaft24is arranged on the support shaft22. When the outer shaft24is subsequently pushed on, the difficulty arises that the latching element has to be pressed into the receiving bore12counter to the spring force of the biasing means70, in order to prevent blocking of the outer shaft24when being pushed onto the support shaft22by way of the spherical latching element.

As previously described, the manufacturing process for the adjustable camshaft10has improved given that there is no longer a risk of the detent ball72falling out of the support shaft22given that the detent ball72or latching element maintains position within the bore12during the assembly process without the aid of the outer shaft24. Also, as previously noted, the support shaft22length may be shortened given that the region for only supporting the outer shaft24in the assembly process is no longer needed.