Pneumatic spring with a vibration damper

A pneumatic spring having a vibration damper and a rolling bellows which defines a spring chamber. The rolling bellows is actively connected at one end to the vibration damper which has a container pipe which possesses a connecting bearing to a motor vehicle chassis. The connecting bearing is arranged in the region of the outer surface of the container pipe. The connecting bearing is of circular design and possesses a sealing ring which seals the spring chamber. Furthermore, the connecting bearing can be designed as a pivot bearing, having at least one universal ball joint in conjunction with a ball socket. Optionally, an air direction device may be assigned to the pneumatic spring, producing a targeted air flow onto the container pipe.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The invention relates to a pneumatic spring with a vibration damper.
 2. Discussion of the Prior Art
 German reference DE 197 55 549 A1 describes a pneumatic spring having a
 vibration damper. Frequently, a pneumatic spring and a vibration damper
 are installed separately in a vehicle as individual subassemblies. There
 is an important reason for this method of construction. The structural
 space within the chassis is so confined that a pneumatic spring of
 sufficiently large dimensions cannot always be installed concentrically
 with the vibration damper.
 In order to eliminate axial structural space problems in the case of
 vibration dampers, some solutions are known in which the connecting
 members of the vibration damper have been specially designed. For example,
 German reference DE 196 25 106 A1 describes a vibration damper in which at
 least two laterally mounted bearings have been produced. The gain in axial
 structural space corresponds to the structural height of a bearing.
 A further problem resides in the fact that, during operation of vibration
 dampers, waste heat is produced due to the operating principle, caused by
 the throttling of a damping medium within the vibration damper. This waste
 heat is adequately removed by the slipstream. The container pipe of the
 vibration damper represents a heat exchanger with the ambient air. In the
 event of deficient heat removal, the sealing of the vibration damper may
 be damaged, which would result in a functional failure of the whole
 vibration damper.
 SUMMARY OF THE INVENTION
 Accordingly, it is an object of the present invention to find a solution
 for the confined structural space of a pneumatic spring with a vibration
 damper. A further object lies in ensuring heat removal for the vibration
 damper. In addition, adequate angular mobility of the vibration damper
 within the chassis is to be guaranteed.
 The object regarding the structural space is achieved, according to the
 invention, in that the connecting bearing is arranged in the region of the
 outer surface of the container pipe, the connecting bearing being of
 circular design and possessing a sealing ring which seals the spring
 chamber.
 First, advantageously, a substantial saving of axial structural space is
 achieved. A further essential advantage resides in the fact that a
 conventional elastic bearing element, in addition to its anti-vibration
 insulation function, also performs a sealing function for the spring
 chamber. The bearing element is of such large dimensions that a
 correspondingly large sealing surface and sealing gap lengths are present,
 which ensure reliable sealing of the spring chamber of the pneumatic
 spring.
 In a further embodiment, the connecting bearing possesses a radial
 prestress sleeve whose prestress force is active toward the container
 pipe. The effect of this is that the connecting bearing or the sealing
 ring of the connecting bearing is not dependent on its own prestress to
 perform its function.
 To absorb the tensile forces acting on the vibration damper, the prestress
 sleeve possesses a base which represents an axial prestress surface for
 the connecting bearing. Furthermore, the connecting bearing possesses a
 fixing disk which prestresses the sealing ring axially to the base of the
 prestress sleeve. As a result, the sealing ring is guided on all sides
 within the prestress sleeve between the base and the fixing disk. Said
 components form an independent structural unit.
 To transmit forces from the container pipe to the connecting bearing, the
 sealing ring possesses a support ring actively connected to the container
 pipe. In this arrangement, the support ring is at least axially enclosed
 by the sealing ring.
 In an embodiment of the invention, that the connecting bearing possesses a
 sealing ring for sealing the spring chamber and a bearing ring for
 absorbing the damping support forces. A bearing ring may also have to meet
 other specific requirements, which for example demand a different
 material. The use of two ring elements may therefore be entirely logical.
 In order, furthermore, to obtain a compact pneumatic spring/vibration
 damper structural unit, the sealing ring and the bearing ring are
 supported on the support ring.
 With regard to the partial object of particularly smooth angular movement
 between the vibration damper and the pneumatic spring, the connecting
 bearing is designed according to the invention as a pivot bearing,
 possessing at least one universal ball joint in connection with a ball
 socket.
 In order for the connecting bearing to be simple to install, the ball
 socket is of divided design in the axial direction of the pneumatic
 spring.
 It has proven highly advantageous here if the sealing ring is inserted
 within the running surface of the ball socket. In this area, the sealing
 ring has a constant prestress.
 In a further embodiment, the sealing ring is inserted between ball socket
 shells which form the ball socket. The sealing ring is thus able to
 undertake a sealing function at its inner and its outer diameters.
 In order for the radial structural space requirement to remain low, the
 ball socket shells are radially held by the prestress sleeve.
 The further components of the connecting bearing are likewise used for
 guidance, the ball socket shells being axially held by the base of the
 prestress sleeve and/or by the fixing disk.
 With appropriate numbers of units, provision may be made for the fixing
 disk and a ball socket shell to be of integral design. Consequently, the
 prestress sleeve may also be designed integrally with a ball socket shell.
 It is envisaged that at least one of the parts, prestressing the sealing
 ring, of the connecting bearing is connected to the chassis. The spring
 force of the pneumatic spring is thus decoupled from the vibration damper.
 The container pipe may be produced with thin walls. A small structural
 space can also be provided for the bearing, since only the damping forces
 now have to be supported.
 In yet another embodiment, the prestress sleeve possesses a dimension
 extending beyond the connecting bearing with a connection to the chassis.
 The prestress sleeve can easily be produced with fairly thick walls, so
 that sufficient structural space exists, for example, for a screw
 connection to the chassis.
 In a further embodiment of the pneumatic spring, a stop buffer is arranged
 in the spring chamber and moves relative to the container pipe of the
 vibration damper. The pneumatic spring possesses an impact surface which
 is held by the prestress sleeve in a fixed position relative to the
 connecting bearing. The compressive forces of the stop buffer which arise
 are directly supported on the chassis. For this purpose, cylindrical
 pipe-end caps are generally used which form the impact surface in order to
 protect the sensitive seal of the piston rod of the vibration damper. This
 expense is completely eliminated by the present invention.
 With a sufficiently large number of units of the pneumatic spring according
 to the invention, it is possible to arrange for the impact surface to be
 designed integrally with the prestress sleeve. In order not to waste any
 structural space, the impact surface of the prestress sleeve is formed by
 the back of the base.
 To achieve the partial object of the invention relating to heat removal,
 the pneumatic spring is assigned an air direction device which produces a
 targeted air flow onto the container pipe. A heat build-up critical for
 the vibration damper is thus prevented.
 In this arrangement, the air direction device is formed by a spoiler. The
 spoiler may be a simple molding of metal or plastic which deflects the air
 flow at the chassis.
 The shaping of the air direction device is selected so that the air
 direction device is directed toward the connecting bearing. A critical
 component is thus specially protected.
 The various features of novelty which characterize the invention are
 pointed out with particularity in the claims annexed to and forming a part
 of the disclosure. For a better understanding of the invention, its
 operating advantages, and specific objects attained by its use, reference
 should be had to the drawing and descriptive matter in which there are
 illustrated and described preferred embodiments of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 FIG. 1 shows a pneumatic spring 1 in connection with a vibration damper 3.
 The pneumatic spring 3 comprises a rolling bellows 5 which is sealingly
 clamped against a fixing plate 7. The fixing plate 7 serves as an element
 connecting the pneumatic spring to a vehicle structure. At its other end,
 the rolling bellows 5 is stressed on a rigid rolling pipe 9 which is
 arranged in a fixed position relative to the vibration damper 3.
 Concentrically with the rolling bellows 5, the vibration damper 3 is
 connected by its piston rod 11 to the fixing plate 7. The piston rod 11
 has a pin-type joint 13 which permits a cardanic movement of the piston
 rod 11 relative to the fixing plate 7. A container pipe 15 of the
 vibration damper 3 is also shown as an individual part, which is connected
 via a connecting bearing 17 to a chassis 19, only shown diagrammatically.
 The connecting bearing 17 is provided on an outer surface 21 of the
 container pipe 15. In addition, the connecting member has a support ring
 23 which is enclosed on both sides and externally by a sealing ring 25.
 The sealing ring 25 is of elastic design and permits an angular movement
 of the container pipe 15.
 The sealing ring 25 is radially prestressed by a prestress sleeve 27 toward
 the container pipe 15. The prestress sleeve has a base 27a, which supports
 the sealing ring 25 in an upward movement of the container pipe 15. In the
 opposite direction, a fixing disk 29 serves as a retaining means for the
 sealing ring 25. The container pipe 15, the prestress sleeve 27 with the
 sealing ring 25 and the fixing disk 29 form a prefittable structural unit.
 Arranged between the prestress sleeve 27 and the rolling pipe 9 is an
 angled cover plate 31, so that a main spring chamber 33, essentially
 defined by the fixing plate 7 and the rolling bellows 5, and an additional
 spring chamber 37 are provided between the rolling pipe 9 and the
 prestress sleeve 27, closed by the cover plate 31. The rolling pipe 9 has
 connection apertures 39 between the spring chambers. The intention of the
 additional spring chamber 37 is to provide the largest-volume spring
 chamber possible, which allows a lower spring rate.
 In the illustrated embodiment, the connecting bearing 17 is arranged
 directly on the chassis 19. As a result, an angularly rigid arrangement of
 the vibration damper 3 is achieved. The fixing disk 29, as part of the
 connecting bearing, is directly connected to the chassis 19, for example
 by screwing. As a result, all spring forces are directly supported by the
 chassis 19. The vibration damper 3 is in practice parallel-connected and
 only has to absorb the damping forces, so that the vibration damper 3 can
 be designed for lower loads because the load is reduced by comparison with
 the state of the art.
 Within the main spring chamber 33, a stop buffer 41 is fixed to the piston
 rod 11 and, above a particular state of spring deflection, comes into
 contact with an impact surface 43. The impact surface 43 is likewise
 supported by the prestress sleeve 27, so that this load is also supported
 on the chassis 19, circumventing the vibration damper 3.
 The embodiment according to FIG. 2 differs from that of FIG. 1 in that the
 connecting bearing 17 is at a significant axial distance from the chassis
 19. In this arrangement, the prestress sleeve 27 is connected to the
 chassis 19, for example screwed to the end face. The fixing disk 29 can be
 welded, pressed or screwed into the prestress sleeve 27. As a result of
 the raised position of the connecting bearing 17, the vibration damper 3
 can more easily move cardanically relative to the prestress sleeve 27 and
 hence to the chassis 19.
 The intention of FIGS. 3 and 4 is to illustrate that the prestress sleeve
 27 may also have a contour such as a rolling pipe. In these pneumatic
 springs 1, the use of an additional spring chamber has been dispensed
 with. Moreover, in both embodiments, the connecting bearing 17 has been
 raised and the connection to the chassis 19 taken over by the prestress
 sleeve 27. A prestress sleeve 27 corresponding to FIGS. 3 and 4 may be
 produced as a casting or forging. The fixing disk 29 is simply screwed to
 the underside of the prestress sleeve 27.
 The intention of FIG. 4 is to illustrate that the additional structural
 space below the connecting bearing 17 can be used, for example, for an
 external adjustment valve 45 of the vibration damper 3 which, depending on
 the method of construction, may also be controlled by the pneumatic
 spring. Moreover, the circular stop buffer 41 is used, whose inner
 diameter is greater than the outer diameter of the container pipe 15. The
 impact surface 43 for the stop buffer is formed by the base 27a of the
 prestress sleeve.
 FIG. 5 shows a modification of FIG. 1 in the region of the connecting
 bearing 17, in which, as a variation, the sealing ring 25 and, in
 addition, a bearing ring 47 are used. The sealing ring 25 can of course
 also take on bearing forces and the bearing ring 47 can also take on the
 sealing function, but a more specific selection and dimensioning of the
 individual rings may be undertaken.
 A further difference from FIG. 1 resides in the fact that the bearing ring
 47 rests directly on the chassis 19. It is useful for the installation
 procedure if the bearing ring 47 possesses a slight prestress relative to
 the support ring 23 or to the prestress sleeve 27, so that the bearing
 ring 47 does not unintentionally fall out from the connecting bearing 17.
 FIG. 6 shows a further modification of the connecting bearing 17 in a
 pneumatic spring 1 in connection with a vibration damper 3. The connecting
 bearing 17 has an annular ball socket 49 on which two ball socket shells
 51a, 51b engage, thus forming a running surface for the universal ball
 joint. Arranged between the ball socket shells 51a, 51b is the sealing
 ring 23, which can perform a sealing function with its inner and outer
 diameters. Radially, the ball socket shells 51a, 51b are held by the
 prestress sleeve 27. Axially, the base 27a and the fixing disk 29 serve as
 fixing means. It is entirely conceivable for the ball socket shell 51a to
 be designed integrally with the prestress sleeve 27. In the left-hand
 half-section, the fixing disk 29 is screwed to the prestress sleeve.
 Another screw fastening exists between the fixing disk and the chassis 19.
 In the right-hand sectional half of FIG. 6, it is shown that not only can
 the upper ball socket shell 51a be designed integrally with the prestress
 sleeve 27 but the fixing disk 29 can be designed integrally with the lower
 ball socket shell 51b. As is apparent, the connection of the connecting
 bearing 15 to the chassis 19 is simplified in that simple through screws
 can be used between the prestress sleeve 27 and the fixing disk 29. In the
 embodiment according to FIG. 6, an obliquely positioned vibration damper
 can be produced very simply, so that transverse force compensation
 relative to the piston rod 11 is possible.
 FIG. 7 shows a further development of FIG. 4, the use of an air direction
 device 53 not necessarily having to be combined with an embodiment of a
 pneumatic spring/vibration damper structural unit according to FIGS. 1 to
 6. The air direction device 53 can also be used in a conventional
 pneumatic spring, as referred to in the prior art. The air direction
 device is a spoiler whose shape is designed so that the slipstream within
 the chassis is directed toward the vibration damper 3. In particular, the
 connecting bearing 17 and the piston rod seal (not shown) of the vibration
 damper are to be cooled by the circulating air.
 The invention is not limited by the embodiments described above which are
 presented as examples only but can be modified in various ways within the
 scope of protection defined by the appended patent claims.