Internal combustion engine

Abstract: This invention concerns internal combustion engines comprising a valve mechanism including a camshaft (3) rotatably supported in a cylinder head (1) by camshaft bearings (5,6,7) including camshaft bearing caps (7) attached to said cylinder head and an angle sensor (14) for detecting the angular position of said camshaft. The internal combustion engine has been improved in that one of the camshaft bearing caps (7) is designed to support said angle sensor.

Description: This invention relates to an internal combustion engine comprising a valve mechanism including a camshaft rotatably supported in a cylinder head by camshaft bearings including camshaft bearing caps attached to said cylinder head and an angle sensor for detecting the angular position of said camshaft. Some engines are equipped with dynamic valve mechanisms which open and close the air intake and exhaust valve in synchronization with the rotation of the crankshaft. The air intake and exhaust valves comprising this dynamic valve mechanism are opened and closed at the appropriate timing by means of the rotation of camshafts. The camshafts used in dynamic valve mechanisms are supported by camshaft caps over cylinder head bearings. In some cases, a trigger wheel is mounted on this camshaft, an angle sensor being positioned opposite this trigger wheel. This angle sensor is used to detect the stroke conditions in a specific cylinder, and this detection information may then be used for example to control the ignition timing. The mounting of the angle sensor is normally implemented, for example by drilling a mounting hole in the side of the cylinder head. Or, as disclosed in Japan Patent Sho 63-26267 or in Japan Patent Application Kokai Publication Hei 4-287841 (corresponding to US-A-5 293 776 and disclosing the features defined in the preamble of claim 1), the mounting hole may be placed in the head cover, and the sensor may be attached at this hole. The former mounting method wherein the angle sensor is attached to the cylinder head increases the number of process steps in fabricating the cylinder head. Moreover, the mounting hole must be positioned either on the air intake side or the exhaust side, but it is necessary to locate the VVT (Variable Valve Timing, i.e., a valve timing variation mechanism) which changes the air intake valve timing, on the air intake side, and injectors and fuel rails must be attached, giving rise to concern over interference between them and the angle sensor and thereby making it difficult to secure the space needed for the angle sensor. If it is mounted on the exhaust side, an insulator must be attached to prevent it from being affected by the heat of the exhaust; this complicates the structure of the angle sensor and increases costs. With the latter mounting method, wherein the angle sensor is mounted to the head cover, the gap between the trigger wheel on the camshaft and the angle sensor increases and may oe a cause of detection error. Accordingly, it is necessary to make adjustments to the mounting position of the sensor in order to improve the accuracy of positioning. Accordingly, it is an objective of the present invention to provide an internal combustion engine having an improved engine angle sensor arrangement, which is compact so as to meet the mounting space requirements and which allows simplified mounting and improves the mounting accuracy. According to the present invention this objective is performed in that at least one of the camshaft bearing caps is designed to support the angle sensor. According to a preferred embodiment of the invention, the angle sensor is attached to a sensor holder formed integrally with said camshaft bearing cap. Preferably, the angle sensor is positioned facing a trigger wheel mounted on said camshaft and the said sensor holder comprises a sensor accommodating portion, which extends above said trigger wheel. According to another preferred embodiment of the invention the sensor holder is provided with a mounting member affixed to the cylinder head at a portion thereof spaced from the camshaft bearing. According to yet another preferred embodiment of the invention a head cover attached to the cylinder head and covering the same is provided with a window surrounding said angle sensor. Preferably, the said angle sensor is attachable to said sensor holder and removable therefrom from the outside of said head cover. In a preferred embodiment of the invention the angle sensor is associated with an intake camshaft for operating at least one intake valve. The angle sensor is mounted on the camshaft cap, positioned inside the cylinder head, thereby easily affording the required mounting space and making it difficult for water, and grime to adhere to it. Also, since it is positioned well away from the exhaust side, no insulator is required to protect it from heat, thereby simplifying the structure of the angle sensor and lowering cost. Further, by attaching the angle sensor to the camshaft cap which supports the camshaft, the accuracy of positioning of the angle sensor can be improved because of the possible variations in the gap between the angle sensors and the caps being kept very small. Furthermore, the sensor holder is formed integral with the camshaft cap so that the sensor holder extends over the trigger wheel, and the sensor holder is firmly supported by the cylinder head. The mounting of the angle sensor in this sensor holder accurately positions the angle sensor above the trigger wheel. The positioning of the angle sensor opposite a window formed in the head cover with the angle sensor being installable and removable from the outside of the head cover permits easy inspection and replacement of the angle sensor. Further preferred embodiments of the invention are laid down in further dependent claims. Hereinafter, the invention will be explained and illustrated in greater detail by means of a preferred embodiment thereof in connection with accompanying drawings, wherein: Fig. 1, is a top view of an internal combustion engine according to a preferred embodiment of the invention, showing the cylinder head of the engine with the head cover removed, Fig. 2, is an enlarged top view similar to Fig. 1, showing the angle sensor system, Fig. 3, is a sectional view along line III-III of Fig. 2, and Fig. 4, is a sectional view along line IV-IV of Fig. 2. The cylinder portion of an internal combustion engine according to a preferred embodiment of the invention can be seen in Fig. 1. The engine is a four-cylinder engine, with sparkplug holes la being formed to correspond to the cylinders in the cylinder head 1. Spark plugs (not shown) are mounted in these plug holes 1a. Also, for each cylinder, there are two air intake valves 9 mounted on the air intake side, and two exhaust valves 10 are mounted on the exhaust side to the cylinder head 1 of each cylinder. Further, injector mounting holes 1b are present in the cylinder head 1 on the air intake side opposite the cylinders, and these injector mounting holes 1b hold injectors (not shown). Head cover 2 is attached to the cylinder head 1 of the engine, and also attached to the cylinder head 1 and housed inside the head cover 2 are the air intake camshaft 3 and exhaust camshaft 4 of the dynamic valve system, which are respectively supported by bearings 5, 6 of cylinder head 1 and camshaft caps 7, 8. Cams 3a, 3b formed on the air intake camshaft 3 operate air intake valves 9 on each cylinder, and cams 4a, 4b formed on the exhaust side camshaft 4 operate exhaust valves 10. Camshaft caps 7 are mounted by mounting bolts 11 between cams 3a and 3b on camshaft 3 to the bearings 5, and camshaft caps 8 are mounted to the bearings 6 by bolts 12 between cams 4a and 4b on camshaft 4, so that the camshaft caps 7, 8 are positioned over the cylinders. Pulleys 50, 51 are mounted to the end of the air intake camshaft 3 and the exhaust camshaft 4, respectively, and these pulleys 50, 51 are linked to the crankshaft (not shown) by means of a timing belt 52 spanning them. Thus, the air intake camshaft 3 and the exhaust camshaft 4 rotate synchronously with the rotation of the crankshaft, and open and close the air intake valves 9 and exhaust valves 10. Also, a VVT 53, to vary the intake valve timing, is siutated on the pulley 50 side of the air intake camshaft 3, and this VVT 53 drives a hydraulical, regulated valve 54. A trigger wheel 13 is mounted on the opposite end of the air intake camshaft 3 from the end where the pulley 50 and the VVT 53 are located. This trigger wheel 13 rotates integrally with the camshaft. An angle sensor 14 is mounted on the end camshaft cap 7, opposite the trigger wheel 13. This angle sensor 14 is used to detect the stroke condition of a certain cylinder, for example to control the ignition timing based upon the determination for that cylinder. This angle sensor 14 is affixed to the camshaft cap 7 by means a sensor holder 7a which is integral with the end camshaft cap on the air intake side. This sensor holder 7a extends in the camshaft direction to above the trigger wheel 13. A cylinder mounting member 7b is formed on the sensor holder 7a, and this cylinder mounting member 7b is affixed to the boss 1a on the cylinder head 1 by means of a mounting bolt 15. That sensor mounting area 7c of the sensor holder 7a which extends above the trigger wheel 13 is positioned opposite a window area 2a formed in the head cover 2 covering the cylinder head 1, and the angle sensor 14 is attached to this sensor mounting member 7b in a manner such that it is removable from the outside of the head cover 2. Thus, by positioning the sensor mounting member 7c of the sensor holder 7a at this window 2a formed in the head cover, and by making the angle sensor 14 removably attachable to this sensor mounting member 7c, it is possible to inspect or replace the angle sensor from outside the head cover. A seal 16 is mounted in the window area 2a formed in the head cover, and this seal 16 prevents the entry of water or dust into the head cover. Thus, the angle sensor 14 is mounted to the camshaft cap 7, and because the angle sensor 14 is positioned inside the cylinder head, it is easy to provide adequate mounting space and to protect it from water, dust, etc. Also, it requires no insulator because it has been located away from the exhaust side. This simplifies the structure of the angle sensor 14 and lowers cost. Furthermore, because the angle sensor 14 is attached to the camshaft cap 7 that supports the camshaft, there is but little variation in the gap D between the angle sensor 14 and the trigger wheel 13 of the camshaft, the positioning accuracy of the angle sensor is improved thereby. Furthermore, the sensor holder 7a is integral with the camshaft cap 7, and the sensor holder 7a extends above and beyond the trigger wheel, but the cylinder mounting member 7b of the sensor holder 7a is securely supported by the boss 1a on the cylinder head 1. In addition, the sensor holder 7a extends above the trigger wheel 13, and the angle sensor is attached to the sensor mounting member 7c to securely hold the angle sensor 14 over the trigger wheel 13. In this example, the camshaft cap 7 to which the angle sensor was attached at a position over the cylinder and the sensor holder 7a was designed to overhang the trigger wheel 13, but it would also be possible to position the camshaft cap over the bearings to the side of the cylinders, and mounting the angle sensor 14 to the camshaft cap that supports the camshaft in these bearings. In this case, there would be no need for an overhanging sensor holder, and the angle sensor could be securely held without additional support of the sensor holder from the cylinder head. As described above, the angle sensor is mounted to the camshaft cap and is positioned inside the cylinder head, making it easy to secure the required space even when a VVT is located on the air intake side, and it is thus protected from water, dust and the like. Also, since the angle sensor is located away from the exhaust side, there is no need to provide an insulator to protect it from the heat, thereby simplifying its structure and lowering its cost. Further, since the angle sensor is mounted on the camshaft cap that holds the camshaft, there is but a small gap between the angle sensor and the trigger wheel on the camshaft, and the accuracy of positioning the angle sensor is thereby improved. Furthermore the sensor holder is formed integrally with the camshaft cap and is supported oil the cylinder head to allow the sensor holder to be securely extended over the trigger wheel. Since the angle sensor is attached to the sensor holder that extends over the trigger wheel, it is possible to accurately position that angle sensor over the trigger wheel. Moreover, the above described arrangement enables the removal and installation of the angle sensor through a window formed in the head cover at the position of the angle sensor, thereby simplifying inspection and replacement.

Claims: Internal combustion engine comprising a cylinder block with a cylinder head (1) affixed thereto, a valve mechanism including a camshaft (3,4) rotatably supported in said cylinder head (1) by camshaft bearings (5,6) including camshaft bearing caps (7) attached to said cylinder head (1), and an angle sensor (14) for detecting the angular position of said camshaft characterised in that at least one of said camshaft bearing caps (7) is designed to support said angle sensor (14). Internal combustion engine according to claim 1, characterised in that said angle sensor (14) is attached to a sensor holder (7a) formed integrally with said camshaft bearing cap (7). Internal combustion engine according to claim 2, characterised in that said angle sensor (14) is positioned facing a trigger wheel (13) mounted on said camshaft (3,4), and that said sensor holder (7a) comprises a sensor accommodating portion (7c) which extends above said trigger wheel (13). Internal combustion engine according to claim 2 or 3, characterised in that said sensor holder (7a) is provided with a mounting member (7b) affixed to the cylinder head (1) at a portion thereof spaced from the camshaft bearing. Internal combustion engine according to at least one of claims 1 to 4, characterised in that a head cover (2) attached to the cylinder head and covering the same is provided with a window (2a) surrounding said angle sensor (14). Internal combustion engine according to claim 5, characterised in that said angle sensor (14) is attachable to said sensor holder (7a) and removable therefrom from the outside of said head cover (2). Internal combustion engine according to claim 5 or 6, characterised in that said sensor accommodating portion (7c) extends through the said window (2a) and a sealing member (16) is provided for sealing the gap between said sensor accommodating portion (7c) and said head cover (2) defining the window (2a). Internal combustion engine according to at least one of claims 1 to 7, characterised in that the angle sensor (14) is associated with an intake camshaft (3) for operating at least one intake valve (9). Internal combustion engine according to at least one of claims 1 to 8, characterised in that the angle sensor (14) is disposed at one end of said camshaft (3,4) while drive means (50,51,52,53) for driving said camshaft (3,4) are positioned at the other end thereof. Internal combustion engine according to claim 9, characterised in that said drive means includes a valve timing variation mechanism (53) for varying the rotary position of said camshaft (3) relative to the crankshaft.

Inventors: KOMATSU KENJI, ONO KATSUMASA, KOMATSU, KENJI, ONO, KATSUMASA
Applicants: YAMAHA MOTOR CO LTD, YAMAHA HATSUDOKI KABUSHIKI KAISHA
Application year: 1995
Main classification: F01L1
IPC codes: F01L1, F02D35, F02B77