SYSTEM FOR MEASURING THE ANGULAR POSITION OF AN INTERNAL COMBUSTION ENGINE CRANKSHAFT

Abstract: A system is described for measuring the angular position of an internal combustion engine crankshaft (1), comprising a magnetic sensor (5) and at least two projections (6) provided on a flywheel (2) which is rigid with the crankshaft (1). The main characteristic of the present invention is that the sensor (5) has its longitudinal axis parallel to the axis of the crankshaft (1) and is supported by that portion (4) of the crankcase (3) which faces the flywheel (2). As the projections (6) pass in proximity to the sensor (5), this latter generates an electrical pulse which is utilised in a central control unit for electronic ignition and/or electronic injection.

Description: This invention relates to a system for measuring the angular position of an internal combustion engine crankshaft, particularly for controlling an electronic ignition device. Currently used systems of the aforesaid type, e.g. those shown in US-A 4235101 and EP-A 0004416, are known to comprise a magnetic sensor mounted in proximity to the flywheel and arranged to sense the presence of projections provided on the engine flywheel, so as to generate for each projection a corresponding electrical pulse which is utilised in a central control unit for electronic ignition and/or electronic injection. The main drawback of the aforesaid systems is that the position of the sensor has necessarily to be finally adjusted relative to the engine. In this respect, it is well known that if it is positioned on parts which are detached from the crankcase, large tolerances arise and therefore, as the sensor can be installed either before or after the installation of the flywheel, it is apparent that the position of this sensor must then be modified on the basis of its position relative to the flywheel. The object of the present invention is to provide a system for measuring the angular position of an internal combustion engine crankshaft which is free from the aforesaid drawback, by obviating any need for radial and axial adjustment subsequent to assembly. The present invention provides a system for measuring the angular position of a crankshaft in an internal combustion engine, comprising at least two projections provided on a flywheel which is angularly rigid with said crankshaft, and a magnetic sensor arranged to sense the passage of said projections in order to generate an electrical pulse utilised preferably by a central control unit for electronic ignition and/or electronic injection; said magnetic sensor being supported by that portion of the engine crankcase which faces said flywheel, and having its longitudinal axis parallel to that of said crankshaft, and said projections extending from that face of said flywheel which faces said portion of said crankcase; said projections consisting of respective circular pins and being located on the same circumference having the centre of said flywheel as its centre; characterized in that said portion of said crankcase comprises an appendix in which a seat is provided for housing said sensor, which has a head extending towards said flywheel. The present invention will be more apparent from the description of a preferred embodiment thereof given hereinafter by way of non-limiting example with reference to the accompanying drawings, in which: Figures 1 and 2 are sectional and frontal views respectively of a region of an internal combustion engine in which a system for measuring the angular position of a crankshaft is installed. As shown in Figures 1 and 2, the measuring system according to the present invention is mounted on an internal combustion engine comprising a crankshaft 1, a flywheel 2 angularly rigid with the crankshaft 1, and a crankcase 3, a portion 4 of which is parallel to the flywheel 2. The system comprises a magnetic sensor 5 of known type easily available commercially, and two projections defined by respective cylindrical pins 6 extending from that face of the flywheel 2 facing the portion 4 of the crankcase 3 and perpendicular to the flywheel. The flywheel is made rigid with the crankshaft by screws 11. The sensor 5 is substantially cylindrical and has its longitudinal axis parallel to that of the crankshaft 1. The sensor 5 is housed in a hole 12 acting as a seat with its axis parallel to the axis of the crankshaft 1 and provided in an appendix 13 extending from and coplanar with the portion 4 of the crankcase 3. The sensor 5 has its head 14 extending beyond the hole 12 towards the flywheel 2. It should be noted (Figure 2) that the cylindrical projections or pins 6 are located on the same circumference having the centre of the flywheel 2 as its centre. As each projection 6 passes in proximity to the sensor 5, this latter generates an electrical pulse which, when in use, is utilised in a central control unit for electronic ignition and/or electronic injection. The advantages of the present invention are apparent from the aforegoing description. In particular, the sensor 5 is installed on the engine which, as is well known, is of high precision construction, ie with minimum tolerances. Consequently, there is no need to either radially or axially adjust the position of the sensor 5 relative to the projections 6 of the flywheel 2. Moreover, it should be noted that the sensor 5 is installed in a region of limited space and, in spite of this, its installation is less complicated than that of current systems as there are no adjustment brackets. Finally, it should be noted that the engine requires no modification (except for the hole 12) for the installation of the sensor 5, and that all those sometimes complicated operations involved in the installation and fixing of the sensor support members on other parts of the power unit are dispensed with. Finally, modifications can be made to the system heretofore described and illustrated, but without leaving the protective scope of the present invention.

Claims: A system for measuring the angular position of a crankshaft (1) in an internal combustion engine, comprising at least two projections (6) provided on a flywheel (2) which is angularly rigid with said crankshaft (1), and a magnetic sensor (5) arranged to sense the passage of said projections (6) in order to generate an electrical pulse utilised preferably by a central control unit for electronic ignition and/or electronic injection; said magnetic sensor (5) being supported by a portion (4) of the engine crankcase (3) which faces said flywheel (2), and having a longitudinal axis parallel to that of said crankshaft (1), and said projections (6) extending from that face of said flywheel (2) which faces said portion (4) of said crankcase (3); said projections consisting of respective circular pins (6) and being located on the same circumference having the centre of said flywheel (2) as its centre; characterized in that said portion (4) of said crankcase (3) comprises an appendix (13) in which a seat (12) is provided for housing said sensor (5), which has a head (14) extending towards said flywheel (2).

Inventors: RICORDI, EPPO
Applicants: FIAT AUTO S.P.A.
Application year: 1987
Main classification: G01M15
IPC codes: G01M15, F02P7