Patent Publication Number: US-2003230850-A1

Title: Device for sealing the gap between a stationary housing and rotating shaft

Description:
[0001] Priority to German Patent Application No. 102 25 959.3-52, filed Jun. 11, 2002 and hereby incorporated by reference herein, is claimed.  
       BACKGROUND INFORMATION  
       [0002] The present invention relates to a device for sealing the gap between a stationary housing and a rotating shaft, including a radial packing ring in a stationary mount in the housing, the packing ring having a sealing lip made of a polymer material that comes in contact with the shaft under an elastic prestress, and including a pulse wheel which is mounted upstream from the radial packing ring in the direction of the outside air, rotates with the shaft and has a pulse generator surrounding the shaft at a radial distance, and including a sensor in a stationary mount for detecting rotational movements of the pulse wheel.  
       [0003] European Patent 726 468 B1, for example, describes such a device in which the pulse generator rotates with the shaft and an additional pickup is provided for the pulse signals. However, the known device requires a relatively large installation space and cannot be used if this space is not available. This is the case at the rear end of the crankshaft, for example, because space there is very limited due to the flywheel.  
       SUMMARY OF THE INVENTION  
       [0004] An object of the present invention is to design a device for sealing the gap between a stationary housing and a rotating shaft so that it may be used in radial and/or axial directions with an extremely small installation space. The sensor should be readily accessible, which is very important in the event of repairs. This device should be inexpensive to manufacture and simple to install while also having a long service life.  
       [0005] The present invention provides a device for sealing the gap between a stationary housing and a rotating shaft characterized by the fact that the pulse generator is formed by a cylindrical sleeve having magnetic poles facing radially outward or is composed of a generator wheel having teeth and spaces between the teeth on the outer circumference, that the sealing lip is in the form of a circular ring disk due to the manufacturing method, and in the area of its inner circumference it becomes wider from the direction of the pulse wheel, its inner circumference engaging in the gap formed by the distance between the sleeve and the shaft. A device having such a design may be mounted on the rear end of the crankshaft of a reciprocating piston engine, for example. This location is advantageous in particular in determination of the running smoothness of the crankshaft and for detection of misfiring.  
       [0006] The ring disk is provided with hydrodynamic recirculation elements for fluid leakage at least in the section adjacent to the shaft. When it comes in contact with the shaft, the disk is converted into a type of gasket which surrounds the shaft concentrically. The recirculation elements may run in a helical pattern from the free end of the gasket to the tie-down area of the gasket at the greatest extent. In addition, the gasket may be blocked by an interruption in the twist in the area where it contacts the shaft. The cross section of the recesses, which function as recirculation elements, may be U-shaped, V-shaped or of a similar design. A single trhead recesses or multiple thread recesses may be provided.  
       [0007] The disk is preferably made of PTFE or rubber, but PTFE compounds, elastomers or crosslinkable thermoplastics may also be used.  
       [0008] The entire device may be designed as a modular unit composed of the radial packing ring, the pulse wheel and the sensor.  
       [0009] A space-saving design of the device is achieved in particular when the pulse wheel has a mounting flange which extends radially and is clamped between an end face of a crankshaft and a flywheel on an internal combustion engine when used as intended. The pulse wheel may be bolted to the end face of the crankshaft via the mounting flange.  
       [0010] The sensor is preferably situated on the ambient side of the sealing site. This is cost efficient and requires less space. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
     [0011] The invention is explained in greater detail below on the basis of several exemplary embodiments illustrated in the drawing, in which:  
     [0012]FIG. 1 shows a longitudinal section through the device having a pulse wheel, a sensor and a gasket,  
     [0013]FIG. 2 shows the device having a gasket of a different design, also shown in a longitudinal section,  
     [0014]FIG. 3 shows a longitudinal section of the device having a generator wheel and a gasket mounted in an adhesive part,  
     [0015]FIG. 4 shows a device like that in FIG. 2, having a generator wheel and a gasket mounted on the medium side, and  
     [0016]FIG. 5 shows the device having a generator wheel which is pressed onto the shaft and functions as a bearing surface for the gasket. 
    
    
     DETAILED DESCRIPTION  
     [0017] A first embodiment of the present invention with device  20  shown in FIG. 1 includes essentially radial packing ring  21 , multi-pole wheel  7  and sensor  5 . Radial packing ring  21  has a gasket  9 , which is made of a polymer material and is in turn secured at its outer edge  23  radially on mount  22 . Mount  22  includes reinforcing ring  10  made of metal surrounded by a sheathing  11  of a polymer material. Gasket  9  is made of PTFE in a trumpet-shaped design. On its straight section  26 , gasket  9  is in contact with shaft  3 . Mount  22  is pressed into bore  6  in housing  4  in a stationary position. Pulse generator  7  is composed of a cylindrical sleeve  24 , which is provided with magnetic poles  8  pointing radially outward. In addition, sleeve  24  has a mounting flange  25 , which extends in the radial direction and by which pulse wheel  7  is bolted to the end face of crankshaft  3 . A flywheel  50  (shown schematically) may also be bolted to the crankshaft at the same time. Sensor  5  is mounted on housing  4  and is used in a known way to pick up the various measurement data. Sensor  5  is opposite the magnetized polymer layer on the outer circumference of multi-pole wheel  7  and protrudes into housing bore  6 . The configuration of sensor  5 , multi-pole wheel  7  and gasket  9  is such that sensor  5  is radially above magnetized polymer layer  8  of multi-pole wheel  7  and section  26  of gasket  9 , which is in contact with shaft  3 . This minimizes the axial extent of the entire device. The medium to be sealed is in space  1 , while space  2  contains the ambient air.  
     [0018] Section  26  may be helically shaped, so that fluid may be transferred, and thus the protrusions on section  26  may define hydrodynamic recirculation elements.  
     [0019]FIG. 2 shows another embodiment of device  20  in a longitudinal section, the essential parts of which correspond to the embodiment according to FIG. 1, the difference being that mount  22  is inserted in an inverted position, and fastening part  23  of gasket  9  is oriented toward ambient side  2 .  
     [0020]FIG. 3 shows an embodiment in which a generator wheel  13  is used, having teeth  14  alternating with spaces on its outer circumference. In addition, gasket  9  with its fastening part  23  is mounted in an adhesive part  15  made of plastic. This adhesive part is pressed into bore  6  of housing  5 .  
     [0021]FIG. 4 shows a further embodiment of the design of the packing ring and the attachment of gasket  9  to the same. Packing ring  21  in this case is composed of reinforcement ring  10 , which is provided with a sheathing  11  of a polymer material only on its outer side facing housing  4  and gasket  9 . In this embodiment, a generator wheel  13  is also provided with teeth  14 .  
     [0022]FIG. 5 shows an embodiment in which gasket  9  is mounted in housing  4  using plastic adhesive part  15 . Generator wheel  13 , however, is provided with attachment sleeve  27  which is used for attaching generator wheel  13  onto shaft  3  and simultaneously as a running face for gasket  9  with its side  28  facing away from shaft  3 .  
     [0023] The device according to the present invention may be given an extremely compact design. Gasket  9  may, for example, be designed as a disk with a thickness of just 1 mm and it is provided with its trumpet shape by sliding onto shaft  3 , while shaft  3  is to be provided with a chamfered edge  29  (FIG. 1) on its outer end.