Abstract:
The present invention is generally directed towards a catalytic converter installed in the motor vehicles. More specifically to a method of measuring the pressure on the substrate as the catalytic converter is subject to the spin forming process. A pressure-measuring device such as a sensor is contact with the substrate. In order to transfer data from the rotating catalytic converter to a stationary object, a slip ring device is connected to the pressure-measuring sensor.

Description:
PRIORITY CLAIM 
     This application claims priority to U.S. Provisional Application, Serial No. 60/251,490 filed Dec. 05, 2000. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     This invention relates to a catalytic converter installed in a motor vehicle. More specifically, this invention relates to a method and apparatus for measuring pressure on a substrate of a catalytic converter. 
     BACKGROUND OF THE INVENTION 
     Automotive vehicles use catalytic converters to reduce emissions. Catalytic converters occupy various position in the vehicles, some of which require the exhaust inlet and the outlet tubes to be positioned in specific angles with respect to the catalytic convertor body. 
     One of the preferred way of assembling a catalytic converter is to form the external shell out of a single piece of steel tube. By varying the diameter of the of the tube from narrow to wide and then narrow, a converter body is formed. 
     One of the techniques known to form catalytic converters is a spinform techniques. During the spin forming method the catalytic substrate present in the catalytic converter is subject to high pressure that can result in the breakage of the substrate. Therefore, there is a need to measure the pressure on the substrate as the catalytic converter is subject to the spin forming process. 
     SUMMARY OF THE INVENTION 
     In accordance with the teachings of the present invention a method and apparatus of measuring pressure on the substrate during the spin forming process. Preferably, a pressure-measuring device is in contact with the substrate. The pressure-measuring device is connected to a slip ring device comprising a rotating part and a stationary part. In accordance with the teachings of the preferred embodiment of the present invention, the stationary part of the slip ring device is connected to a controlling device such that the pressure is measured on the controlling device. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further features of the invention will become apparent from the following discussion and the accompanying drawings in which: 
     FIG. 1 is a cut out view of the catalytic converter having a substrate formed in accordance with the teachings of the present invention; and 
     FIG. 2 is a cross sectional view of the catalytic converter having pressure-measuring device inserted inside the catalytic converter in accordance with the teachings of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the invention or its application or uses. 
     Referring in particular to the FIG. 1, a catalytic converter to be installed in an exhaust system of a motor vehicle is generally illustrated by reference numeral  10 . Although not shown in the drawings the catalytic converter  10  is typically installed in the under body of a vehicle and forms a part of the vehicle exhaust system. Alternatively, it may be installed in any other suitable place in the vehicle to typically convert the noxious emissions emitted from the engine. 
     The catalytic converter  10  comprises a housing or an outer shell  12 . Although not shown in the drawings, typically one end of the housing  12  is connected a conduit for receiving exhaust gasses from the engine. The other end of the housing  12  is connected to a exhaust pipe that emits gases that have been converted by the catalytic converter  10 . The housing  12  comprises an inner wall  14 , an outer wall  15  and defines a hollow interior  16 . 
     The catalytic converter  10 , as shown has only one housing  12 . Alternatively, it is possible to have a dual housing catalytic converter  10  having an inner housing and an outer housing. The housing  12  preferably include a central portion  20  and two end portions  22  and  24  connected on either side of the central portion  20 . The catalytic converter  10  defines a central axis represented by reference numeral  26 . The catalytic converter  10  also defines a vertical axis  25 . The central portion  20  is preferably symmetrical around the central axis  26  and the vertical axis  25 . Alternatively, the cross section of the central portion  20  can be round, ellipse or oval. 
     The catalytic converter  10  in accordance with the teachings of the present invention also includes a catalytic substrate  30  inserted into the hollow interior  16  of the housing  12 . Preferably the substrate  30  is present in the central portion  20  of the housing  12 . The substrate  30  used in the present invention is commercially available from Corning, Inc. and is a ceramic composite brick with the suitable catalyst coated on the ceramic brick. 
     In order to protect the substrate  30  from environmental damage during use of the catalytic converter  10 , a mat  32  (as shown in FIG. 2) is wrapped around the substrate  30 . The mat  32  is made of a fiberglass. Preferably, the thickness of the mat  32  is around 10 mm thick. The mat  32  is preferably attached to the substrate  30  with the help of an adhesive such as tape. 
     Referring in particular to FIG. 2, the substrate  30  and the mat  32  are inserted inside the hollow interior  16  of the central portion  20  using well known techniques. Once the substrate  30  and the mat  32  are inserted inside the hollow interior  16 , a gap  34  is defined between the mat  32  and the inner walls  14  of the housing  12 . In order to reduce the gap  34  between the mat  32  and the inner wall  14 , the catalytic converter  10  is subject to the spin forming process. In the alternate, the spinning process is used to form the housing of the catalytic converter  10  having the central portion  20 , and the end portions  22  and  24 . In order to form the catalytic converter  10 , a tubular work piece is used and the substrate is inserted inside the tubular work piece. The tubular work piece is then subject to spin forming process to form the housing  12  having a central portion  20  and end portions  22  and  24 . 
     Although not shown in the drawings, the spin forming process comprises the use of a spinning machine. As shown in FIG. 2 the catalytic converter  10  is mounted horizontally on a shaft (not shown) and is held in place with the help of a chuck  36 . The catalytic converter  10  is capable of rotating around its central axis  26  in the direction of arrows shown by reference numeral  38 . 
     As shown in FIG. 1, the spinning machine includes a roller  40 . The roller  40  used in the present invention is well known in the art and is not explained in details. The roller  40  is placed perpendicular or at an angle to the central axis  26  and is in contact with the outer wall  15  of the catalytic converter  10  such that the roller  40  moves in a desired direction. Preferably, the roller  40  is mounted on actuators (not shown) that move the roller  40  in a direction transverse, shown by arrows  42 , to the central axis  26  such that the roller  40  is moving towards the central axis  26 . In this direction the rollers  40  will reduce the diameter of the outer wall  15  of the catalytic converter  10 . In addition, the roller  32  is also capable of moving in a direction parallel shown by arrows  44  to the central axis  26  such that the roller  40  forms the desired shape of the housing  12 . 
     Referring in particular to FIGS. 1 and 2 as the catalytic converter  10  is subject to the spinning process, a substantial pressure is exerted on the substrate  30 . In order to measure the pressure exerted on the substrate  30  during the spinning process, a pressure-measuring device is provided. The pressure-measuring device is placed in contact with the substrate  30  such that pressure on the substrate  30  is measured as the catalytic converter  10  is subject to the spin forming process. 
     The pressure-measuring device comprises a pressure sensor  48  and at least one lead wire  50  connected to the pressure sensor  48 . The pressure sensor  48  is in contact with the substrate  30 . The pressure sensor  48  is capable of outputting a pressure signal indicative of the pressure exerted on the substrate  30 . Preferably, a film type pressure sensor is used and is commercially available from Tekscan, Inc. The lead wire  50  carries the pressure signal to a signal processing electronics board  56 . Preferably, the signal processing electronics board  56  is an analog digital board (A/D Board). The signal processing electronics board  56  acts as a signal conditioner to the pressure signal from the pressure sensor. In particular, signal processing electronics board converts analog signals to digital signals. The signal processing electronics board  56  preferably comprises an input section  58  and an output section  60 . The signal processing electronics board  56  is attached to the housing  12  with the help of clamps  57  and is capable of rotating with the catalytic converter  10 . 
     In order to measure the pressure exerted on the substrate  30  during the spin forming process, a cable  51  from the output section  60  of the signal processing electronics board  56  is connected to a slip ring device  62 . The cable  51  is capable of rotating with the catalytic converter  10 . The slip ring device  62  comprises a slip ring rotor  64 , a slip ring stator  66  and a slip ring adapter  68 . The slip ring rotor  64  comprises an input socket  70 , wherein the cable  51  from the output section  60  of the signal processing electronics board  56  is connected to the input socket  70  of the slip ring rotor  64 . The slip ring rotor  64  receives the pressure signal from the pressure sensor  48 . The slip ring rotor  64  is capable of rotating around an axis in the direction shown by arrow  72  with the catalytic converter  10 . Therefore, as the catalytic converter  10  is rotating around axis  26 , the slip ring rotor  64  is also rotating with the catalytic converter  10 . The slip ring rotor  64  is mechanically and electrically connected to the slip ring stator  66 . The slip ring stator  66  is preferably stationary and is connected to a stationary object  74  such as a tailstock mandrill with the help of a slip ring adaptor  68 . 
     The slip ring stator  66  comprises an output socket  78  corresponding to the input socket  70 . The output socket  78  is connected to a processor  80  such as a computer. The processor  80  measures the pressure signal from the slip ring rotor  64  and thereby measuring the amount of pressure exerted on the substrate  30 . It is preferred that the pressure exerted on the substrate  30  does not exceed 100 psi. If the processor  80  measures pressure on the substrate  30  to exceed the preferred limit, the processor  80  can change spin forming parameters such as the speed of rotation of the catalytic converter  10 , the speed at which the rollers  40  move perpendicular or parallel to the central axis  26  or the distance traveled by the roller  40  towards the central axis  26 . By controlling the spin forming parameters the pressure exerted on the substrate  30  can be controlled and will help prevent premature breaking of the substrate  30 . 
     As any person skilled in the art will recognize from the previous description and from the figures and claims, modifications and changes can be made to the preferred embodiment of the invention without departing from the scope of the invention as defined in the following claims.