Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16H—GEARING
  • F16H53/00—Cams or cam-followers, e.g. rollers for gearing mechanisms
  • F16H53/02—Single-track cams for single-revolution cycles; Camshafts with such cams
  • F16H53/025—Single-track cams for single-revolution cycles; Camshafts with such cams characterised by their construction, e.g. assembling or manufacturing features
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
  • F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
  • F01L1/02—Valve drive
  • F01L1/04—Valve drive by means of cams, camshafts, cam discs, eccentrics or the like
  • F01L1/047—Camshafts
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
  • F16D1/00—Couplings for rigidly connecting two coaxial shafts or other movable machine elements
  • F16D1/06—Couplings for rigidly connecting two coaxial shafts or other movable machine elements for attachment of a member on a shaft or on a shaft-end
  • F16D1/08—Couplings for rigidly connecting two coaxial shafts or other movable machine elements for attachment of a member on a shaft or on a shaft-end with clamping hub; with hub and longitudinal key
  • F16D1/0894—Couplings for rigidly connecting two coaxial shafts or other movable machine elements for attachment of a member on a shaft or on a shaft-end with clamping hub; with hub and longitudinal key with other than axial keys, e.g. diametral pins, cotter pins and no other radial clamping
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T29/00—Metal working
  • Y10T29/49—Method of mechanical manufacture
  • Y10T29/49229—Prime mover or fluid pump making
  • Y10T29/49293—Camshaft making
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T74/00—Machine element or mechanism
  • Y10T74/21—Elements
  • Y10T74/2101—Cams

Definitions

• the invention relates to a camshaft for internal combustion engines according to the generic concept of claim 1.
• the camshaft of an engine carries several cams.
• the camshaft must be supported between the cams.
• the camshaft In the case of structurally simple, undivided bearings, the camshaft must be inserted axially into the housing and, for reasons of assembly, it must have at least the diameter on the bearing points on which the cam tips rotate.
• Such large bearing diameters lead to high bearing friction, large bearing play with correspondingly inaccurate guidance of the camshaft and to a large space requirement in the area of the bearings.
• camshaft at the bearing points is given the much smaller diameter, which is necessary for reasons of load-bearing capacity, friction and play turn out to be considerably more favorable.
• the camshaft must then be mounted radially, which requires split bearings with a significantly higher design effort. Because of the necessary screw connections, the installation space requirement is even higher than with the one-piece bearings.
• a camshaft is also known from DE 39 43 426, in which the cam elements are each fastened to a smooth shaft by a cylindrical cross pin.
• the invention is therefore an object of the invention to provide a construction that firstly allows easy and quick axial insertion of the shaft into the bearings while simultaneously threading the cams, secondly leads to the correct positioning of the cams by itself, and thirdly, a quick clamping exclusively allowed with standard tools, which fourthly does not go beyond the conventional solutions in terms of installation space, but which is fifthly also economically producible and finally sixthly transmits the changing torque with absolute certainty.
• the solution according to the invention consists in the radial bracing of the cam disks with the shaft by means of at least one clamping screw arranged in the area of the cam disk and subjected to tensile stress.
• the clamping screws place part of the circumference of the joint between the shaft and cam under a pressure which is sufficient to transmit the torque essentially in a frictional manner.
• the joint can be made with a gap of slightly more than 180 ° with a gap, so that there is ample play when threading.
• the clamping screws can be tightened using a simple standard tool.
• All of the exemplary embodiments have a shoulder-free, circular cylindrical outer surface 2 of the shaft 1, which in each case forms the clamping surface 4 in the region of a cam disk 3 for fastening it and in each case the bearing journal surface 5 in the region of a bearing.
• the above shape of the lateral surface is the simplest possible, the easiest to manufacture and, in contrast to any other conceivable design, it enables the cam disks, which have a cam 6 and an essentially circular region 7 enclosing the shaft, to be placed easily, and which at axial insertion of the shaft into the housing must be axially displaced on this at the same time.
• Fig. 1 shows a relatively simple embodiment.
• the head bearing surface 12 for the clamping screw lies on the shaft in the region of its outer surface.
• the screw head projects beyond the outer surface, it thus lies in the bore or recess 11 which is coaxial with the internal thread and brings about a positive connection with the cam disk.
• the head of the clamping screw is designed as an inner square head. Heads with external profiling could only be accommodated with much more difficulty and could be less easily brought into positive engagement with the cam disk.
• the positive connection between the screw head and the cam disc must of course be as free of play as possible. However, no additional friction may occur on the head, since this would falsify the pretensioning force of the clamping screw despite the correct tightening torque. A close match fit is therefore provided.
• the head support surface of the clamping screw is conical, since this centers the head, and a centering collar on the screw shaft can be omitted.
• the screw shank can thus be carried out continuously from the head to the thread with the tension cross section of the thread used, which is optimal for maintaining the highest possible screw preload.
• the described embodiment assumes that the cam is wider in the axial direction than the inner square head of the clamping screw. This can mean a decisive limitation for motors with limited axial installation space.
• the problem is solved in a further embodiment according to FIG. 2 in that the head support surface 12 for the clamping screw 9 lies inside the shaft 1, the transverse bore 8 in the shaft of the head support surface 12 seen in the direction of the cam 6 with a diameter slightly larger than the thread diameter of the clamping screw, in the direction of the substantially annular region 7 of the cam plate with a diameter slightly larger than the head diameter must be carried out.
• the length of the clamping screw is limited to a little less than the shaft diameter, because the clamping screw must completely disappear into the shaft while the shaft is being pushed through the cam.
• the bore or the recess 11 coaxial with the internal thread only has to be as large as is necessary for producing the internal thread or for carrying out a suitable key.
• Cams for the charge exchange control in internal combustion engines are asymmetrical in some engines, i.e. the leading and trailing flanks have different contours. In this case, swapping the flanks by reversely mounting a cam on the shaft will inevitably lead to improper motor operation.
• FIG. 3 illustrates this using the example of a variant of the embodiment according to FIG. 1.
• the inner wall of the cam disk facing the shaft is designed as a simple circular cylindrical bore, its diameter must be somewhat larger than the shaft diameter. Otherwise the required easy assembly and disassembly of the camshaft would not be possible.
• the inner wall of the cam disc then only touches the shaft at one point on the circumference if the shaft and cam disc are thought to be rigid, the contact normal coinciding with the screw axis.
• a constant change in the position of the contact standards i.e. a constant back and forth movement of the contact point on the Shell surface of the shaft forced. In the long run, this would inevitably lead to the destruction of the components.
• this difficulty is circumvented according to the invention by designing the inner wall of the cam disk, in which the contact between the inner wall of the cam disk and the lateral surface of the shaft is separated in two at two points - Other angular regions 14 of the circumference come about. There are therefore two touch standards, which enclose an angle between them, so that each operating force is absorbed by changing the contact forces V nn and there is no longer any displacement.
• the inner surface of the cam disk is withdrawn with respect to the lateral surface of the shaft.
• Such a withdrawal over an angle of more than 180 ° on the side of the cam opposite the cam also ensures a clear play of the cam on the shaft before the clamping screw is installed and thus for easy assembly of the camshaft.
• FIG. 5 shows with the aid of a variant of the embodiment according to FIG. 2, according to the invention the shaft can be local, i.e. can only be withdrawn in the area 13 of the cams 3, forming a gap.
• the task is to create a sufficiently wide compression zone in the cam from the line contact in the area of the internal thread the area around the clamping screw or even over the entire circumference, so that each operating force is absorbed only by a change in the pressure distribution in the contact zone between the outer surface of the shaft and the inner surface of the cam disc and not by a constant displacement of the contact standards.
• the radius of curvature of the shaft which for the purpose of easy mounting bar is inevitably smaller than the radius of curvature of the inner surface of the cam plate, can adapt to the contour of the inner surface of the cam plate under the action of the clamping force in the environment of the clamping screw.
• the use of a hollow shaft according to the invention is also advantageous because the bore in the shaft can be used as an oil channel, for example for the lubrication of the bearings and the cam / tappet contacts.
• FIG. 6 Another embodiment is shown in FIG. 6.
• the same object is achieved according to the invention in that the cam is pressed against the shaft in the area of the cam 6 by the pretensioning force of the clamping screw, and on the other hand over the entire circumference by introducing tangential tensile forces on the head support surface 12 in the crescent-shaped area of the Cam disc is placed on the shaft.
• the solution according to the invention is characterized by a screw-side head support surface 15 designed in such a way that the head of the clamping screw completely or partially engages over the head support surface 12 on the cam disk, and by a recess 11 in the essentially circular region of the cam disk, which corresponds to the Screw head-shaped head support surface 12 through which the shaft of the clamping screw passes and through which the cam disc is completely separated at this point.
• the head support surface can be made conical, as shown in FIG. 6.
• the recess described can be produced, for example, by the operations of producing a bore, countersinking with a decreasing depth of the sink towards the central axis and slitting the cam disc in the plane spanned by the shaft axis and the screw axis.
• the inner surface of the cam disc can be designed with the shaft diameter; easy assembly is guaranteed by the radial flexibility of the slotted cam disc when the clamping screw is loosened.
• FIG. 7 shows an embodiment variant of FIG. 6. It is characterized by the use of an intermediate piece 16 between the screw head and the cam disc, the side 17 facing the shaft being designed such that it completely or partially overlaps the bearing surface 18 in the plane of the cam disc, the side 19 of the cam facing away from the shaft corresponding to the substantially circular region 7 of the cam disc, and inside of which there is the flat head support surface 12 for the clamping screw.
• This intermediate piece lies in a recess 11, which corresponds to the shape of the intermediate piece Has trained contact surface 18 for the intermediate piece, through which the shaft of the clamping screw passes and through which the cam is completely separated at this point.
• the recess described can be produced particularly easily, for example, by producing a bore which is coaxial with the screw axis, milling through in the direction of the shaft axis with the aid of a form cutter with a decreasing depth towards the center, and by longitudinally slitting the cam disc in the same direction.
• All of the design variants of the solution according to the invention shown in the exemplary embodiments enable the use of undivided bearings of small diameter by clamping the cam disks onto a shoulderless, cylindrical shaft by means of a transverse screw connection, which can be easily tightened or loosened again, for example, with an Allen key.
• the screw connections are designed in such a way that, compared to conventional camshafts, no additional installation space is required, and that the cam disks can be easily positioned during assembly without additional devices.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Valve-Gear Or Valve Arrangements (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=6445101

Family Applications (1)

Country Status (4)

Families Citing this family (11)

Family Cites Families (9)

• 1991
  • 1991-11-19 DE DE4137978A patent/DE4137978C1/de not_active Expired - Fee Related
• 1992
  • 1992-11-15 EP EP92922942A patent/EP0613519A1/de not_active Withdrawn
  • 1992-11-15 US US08/244,021 patent/US5431131A/en not_active Expired - Fee Related
  • 1992-11-15 WO PCT/DE1992/000954 patent/WO1993010336A1/de not_active Application Discontinuation

Non-Patent Citations (1)

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