Valve driving device of engine

Abstract: A valve driving device of an engine under the present invention is provided with a cam shaft (71) for exclusive use of intake for driving intake valves and a cam shaft (72) for exclusive use of exhaust for driving exhaust valves. At least either the intake valve or the exhaust valve is pluralized and a transmitting (133) member is trained between the cam shaft with more valves to drive and an engine output shaft. Gears (143) to mesh with each other are provided on said two cam shafts (71,72). Under the above composition, only one pulley (132) on the driven side or only one sprocket is required and therefore compactness of the engine can be realized. Also, rotation of the cam shaft having more valves to drive and large torque fluctuation can be stabilized and reliability of gears can be improved, without reinforcing the gears.

Description: The present invention relates to a valve driving device of an engine having a single camshaft for exclusively driving more than one intake valve and a single camshaft for exclusively driving more than one exhaust valve at each cylinder of the type as referred in the preamble of the independent claim 1. In a known valve driving device of this kind as disclosed in US-A-4 674 452 the two camshafts are arranged for driving two intake valves and two exhaust valves, respectively at each cylinder of the engine. For improving the intake and exhaust efficiency of such a multiple valve arrangement it has also become known as disclosed in JP-A-62-78453 to arrange three intake valves and two exhaust valves at each cylinder so that the overall number of intake valves in such an engine will be larger than the overall number of exhaust valves. The problem which exists with such engines having different numbers of intake valves and exhaust valves when being driven by two independent camshafts resides in the fact that, as shown in Fig. 10 of the appended drawings, fluctuations of torque applied to one of the camshafts become large at the time of the opening and the closing of the valves which are driven by this one camshaft so that such torque fluctuations are being transmitted through the gearing also to the second camshaft whereby any backlash that exists in the gears of the gearing enhances such torque fluctuations. It is, therefore, a principle object of the present invention to provide an improved valve driving device of the type as referred in the preamble of the independent claim 1 that reduces the torque fluctuations which are existent when a different number of intake and exhaust valves are arranged at each cylinder for being driven by two independent camshafts. With this principle object in mind it is a further object of the present invention to provide at the same time such a driving arrangement for the two independent camshafts that its assembly work will be made easy and will yet guarantee that any backlash that exists in the gearing will not contribute to a malfunction in the driving of such a multiple valve arrangement. In accordance with the present invention there is therefore provided a valve driving device of an engine having a single camshaft for exclusively driving more than one intake valve and a single camshaft for exclusively driving more than one exhaust valve at each cylinder of the type as referred in the preamble of the independent claim 1 and which is provided with its characterizing features. Additional features of the valve driving device according to the present invention are further referred to in the dependent claims. The present invention will be understood more clearly by reading the following description in connection with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS The attached drawings show preferred embodiments of the present invention, in which: Fig.1 is a cross sectional view of a front part of the engine; Fig.2 is a cross sectional view of the front part of the engine, sectioned at the part near the gear between cams; Fig.3 is a plan view, showing a cam carrier member and a gear housing, partly in section; Fig.4 is a simple plan view of the engine; Fig.5 is a cross section, taken along the line V-V in Fig.8; Fig.6 is a cross section, taken along the line VI-VI in Fig.8; Fig.7 is a cross section, taken along the line VII-VII in Fig.8; Fig.8 is a plane perspective view around a cylinder; Fig.9 is a side view, in vertical section, of an oil pressure type lash adjuster, on an enlarged scale; and Fig.10 is an explanatory drawing, showing the fluctuations of torque applied to the camshaft. DETAILED DESCRIPTION OF THE INVENTION Fig.1 to Fig.8 show a V type 6-cylinder engine with three intake valves and two exhaust valves in the embodiment of the present invention. In Fig.4, reference numeral 1 designates a cylinder block. A cylinder head 2 is provided at each of a left bank L and a right bank R. Three cylinders 5 are formed between the cylinder block 1 and each bank L, R. A cam carrier member 3 is provided on the cylinder head 2 of each bank L, R. Construction around each cylinder 5 is explained with reference to Fig.5 to Fig.8. In these figures, only one cylinder 5 of the right bank R is shown as a representative but the other cylinders 5 are all the same in construction. In these figures, a piston 6 is put slidably in the cylinder 5. A combustion chamber 7 of pent roof shape having two inclined walls 7a, 7b is formed at the cylinder head 2. Three independent intake ports 11, 12, 13 which lead intake to the cylinder 5 are provided at the left side part of a cylinder bore of the cylinder head 2. The independent intake ports 12, 13 open at one end thereof to the inclined wall 7a on the left side of the combustion chamber 7 and open at the other end thereof to the left side wall of the cylinder head 2. Openings of the independent intake ports 11, 13 (on both sides) on the combustion chamber side are in line in longitudinal direction of the engine (in vertical direction in Fig.8) and are arranged nearer the center of the cylinder bore than the independent intake port 12 at the center. These three independent intake ports 11, 12, 13 converge into one intake port 10 at the left wall side of the cylinder head 2. Two independent exhaust ports 21, 22 which lead exhaust of the cylinder 5 outward are provided at the right side part of the cylinder bore of the cylinder head 2. These independent exhaust ports 21, 22 open at one end thereof to the inclined wall 7b on the right side of the combustion chamber 7 and open at the other end thereof to the right side wall of the cylinder head. Openings on the combustion chamber side of these two independent exhaust ports 21, 22 form in line in longitudinal direction of the engine. The independent exhaust ports 21, 22 converge into one exhaust port 20. Three intake valves 31, 32, 33 which open and close the openings on the combustion chamber side of the independent intake ports 11, 12, 13 are provided at the cylinder head 2. Each of the intake valves 31, 32, 33 has a valve head part of umbrella shape arranged at the above opening and a valve shaft extending upward from the valve head part and is put slidably in the cylinder head 2 at the valve shaft, namely, is movable up and down. Spring sheets 51, 52, 53 of disc shape are fitted to the valve shaft end portions of the intake valves 31, 32, 33 respectively. Valve springs 61, 62, 63 are disposed in compression between the spring sheets 51, 52, 53 and the cylinder head 2. By spring force of the spring sheets 51, 52, 53, each intake valve 31, 32, 33 is biassed upward, namely, in valve closing direction. These three intake valves 31, 32, 33 incline to the left side of the cylinder bore toward the end portion of the valve shafts and valve shafts are arranged in parallel with each other. Two exhaust valves 41, 42 which open and close the openings on the combustion chamber side of the independent exhaust ports 21, 22 are provided at the cylinder head 2. These exhaust valves 41, 42 are similar in composition to the intake valves 31, 32, 33, are movable up and down and are biased in valve closing direction by spring sheets 54, 55 and valve springs 64, 65. These two exhaust valves 41, 42 incline to the right side of the cylinder bore toward the valve shaft end portion. An explanation is made below about the driving mechanism for the intake valves 31, 32, 33 and the exhaust valves 41, 42. As shown in Fig.3, a camshaft 71 for exclusive use of intake and a camshaft 72 for exclusive use of exhaust, both extending in longitudinal direction of engine, are arranged on the left side and on the right side respectively. These two camshafts 71, 72, are driven by an engine output shaft (not shown in the drawing). While the camshaft 71 for exclusive use of intake rotates clockwise in Fig.5, the camshaft 72 for exclusive use of exhaust rotates counterclockwise in Fig.5. Three intake cams 73 corresponding to each intake valve 31, 32, 33 are formed integrally with the camshaft 71 for exclusive use of intake and two exhaust cams 74 corresponding to each exhaust valve 41, 42 are formed integrally with the camshaft 72 for exclusive use of exhaust. The intake valves 31, 32, 33 are driven by the camshaft 71 for exclusive use of intake through the medium of swing arms 81, 82, 83 respectively. Conventional oil pressure type lash adjusters 91, 92, 93 are provided at the cylinder head 2. A support part is provided for each of these oil pressure type lash adjusters 91, 92, 93. The swing arms 81, 82, 83 rest at one end thereof on the support part of the oil pressure type lash adjusters 91, 92, 93 and rest at the other end thereof on the valve shaft end portion of the intake valves 31, 32, 33. A roller having an axis of rotation in longitudinal direction of engine is provided at the halfway part of the swing arms 81, 82, 83 and this roller is in contact with the intake cam 73. Therefore, when the camshaft 71 for exclusive use of intake rotates, the roller moves up and down according to the lift of the intake cam 73, whereby the swing arms 81, 82, 83 swing up and down with their end portion on the oil pressure type lash adjuster side as center. Thus, the end portions on the valve shaft end portion side of the swing arms 81, 82, 83 swing up and down according to the arm ratio. According to this up and down motion of the end portions, the intake valves 31, 32,33 open and close. The exhaust valves 41, 42, 43 are also driven by the camshaft 72 for exclusive use of exhaust through the medium of the swing arms 84, 85. Similarly to the case of the intakes valve 31, 32, 33, this driving mechanism comprises oil pressure type lash adjusters 94, 95 which support the swing arms 84, 85. When the camshaft 72 for exclusive use of exhaust rotates, the roller of the swing arms 84, 85 moves up and down according to the lift of the exhaust cam 74, whereby the swing arms 84, 85 swing up and down with their end portion on the oil pressure type lash adjuster side as center and the end portion on the valve shaft end portion side of the swing arms 84, 85 swings up and down according to the arm ratio. According to this up and down movement of the end portion, the exhaust valves 41, 42 open and close. An explanation is made about the construction of the oil type lash adjusters 91, 92, 93, with reference to Fig.9. In Fig.9, reference numeral 101 designates a bottomed, cylindrical casing. Reference numeral 102 designates an inner sleeve put slidably in the casing 101. An oil pressure chamber 104 is formed between the casing 101 and the inner sleeve 102. A pivot 103 (as a support part for the end portion of the swing arm 81, 82, 83) is provided at the upper end of the inner sleeve 102. An oil passage 105 which communicates at one end thereof with the oil pressure chamber 104 and communicates at the other end thereof with an oil intake 106 provided at the outer wall of the casing, is provided for the casing 101 and the inner sleeve 102. A check valve 108 for keeping oil pressure of the oil pressure chamber 104 high is provided at the end portion on the oil pressure chamber side of the oil passage 105. Provided in the inner sleeve 102 is an oil discharge passage 107 which communicates at one end thereof with the oil passage 105 and opens at the other end thereof to the center of the pivot 103. Referring to the operation of the oil pressure type lash adjusters 91, 92, 93, in the case where a lash exists in the valve driving system and bearing power which the pivot 103 receives from the swing arms 81, 82, 83 is low, oil pressure of the oil pressure chamber 104 is low and therefore the check valve 108 opens. Thus, oil is supplied to the oil pressure chamber 104 from the oil intake 106 via the oil passage 105 and due to cubical expansion of the oil pressure chamber 104, the inner sleeve 102 gets out of the casing 101. By this operation, clearance between the swing arms 81, 82, 83 and the camshaft 71 for exclusive use of intake and clearance between the swing arms 81, 82, 83 and the intake valves 31, 32, 33 become zero. In this state, bearing power which the pivot 103 receives from the swing arms 81, 82, 83 becomes higher and oil pressure of the oil pressure chamber 104 rises. Thus, the check valve 108 closes. By this operation, the position of the inner sleeve 102 in relation to the casing is fixed and the swing arms 81, 82, 83 are received by the pivot 103. An explanation is made about the arrangement of the oil pressure type lash adjusters 91, 92, 93, 94, 95. In the case of the intake side, the oil pressure type lash adjuster 92 of the central intake valve 32 is provided near the center of the cylinder bore in relation to the intake valve 31, 32, 33. This oil pressure lash adjuster 92 inclines to the left side by the specified angle toward the pivot 103, namely, it is provided in such a fashion that its center axis conforms to bearing power to be received from the swing arm 82. The oil pressure type lash adjusters 91, 93 of the intake valves 31, 33 on both sides are provided on the side far from the center of the cylinder bore in relation to the intake valves 31, 32, 33, namely, the oil pressure type lash adjusters 91, 92, 93 on the intake side are arranged straddling the intake valves 31, 32, 33 in longitudinal direction of engine. Provided in the cylinder head 2 are an oil supply passage 111 which communicates with the oil intake 106 of the oil pressure lash adjuster 92 of the central intake valve 32 and an oil supply passage 112 which communicates with the oil intake 106 of the oil pressure type lash adjusters 91, 93 of the intake valves 31, 33 on both sides. In the case of the exhaust side, oil pressure type lash adjusters 94, 95 of the two exhaust valves 41, 42 are provided on the side far from the center of the cylinder bore in relation to the exhaust valves 41, 42. An oil supply passage 113 which communicates with the oil intake 106 of the two oil pressure type lash adjusters 94, 95, is provided in the cylinder head 2. A plug hole 121 is provided, passing through the cylinder 2 and the cam carrier member 3, above the combustion chamber 7. Fitted in this plug hole 121 is an ignition plug 122 with its ignition point 122a facing the combustion chamber 7. The plug hole 121 and the ignition plug 122 are arranged in parallel with the valve shaft of the exhaust valves 41, 42 so that the ignition point 122a is located at the center of the cylinder bore of the combustion chamber 7. A signal injector 123 which supplies fuel by injection to the intake is provided at the cylinder head 2 at the upper side of the intake port. An explanation is made about the construction for driving the camshafts 71, 72 by the engine output shaft, with reference to Fig.1 and Fig.2. In Fig.1 and Fig.2, reference numeral 131 designates a gear housing provided on the front side of the cylinder head 2 and the cam carrier member 3. A forward end of the camshaft 71 for exclusive use of intake extends frontward, passing through the gear housing 131, and is fitted with a timing pulley 132. The engine output shaft is also fitted with a timing pulley (not shown in the drawing). A timing belt 133 (as a transmitting member) is wound round these two timing pulleys, and the camshaft 71 for exclusive use of intake is driven by the specified timing by the engine output shaft through the medium of the timing belt 133. A gear cover 134 which covers the timing pulley 132 is fitted to the gear housing 131. As shown in Fig.3, the camshafts 71, 72 for exclusive use of intake and of exhaust are disposed rotatably by bearing parts 4a and 4b, namely, on the left side of the cam carrier member 3, the bearing parts being formed at a front end portion, a rear end portion and between cylinders 5. The camshaft 71 for exclusive use of intake has at its halfway part a bearing collar part 71a which is put in and supported by the bearing part 4a. The camshaft 72 for exclusive use of exhaust has at its halfway part a bearing collar part 72a which is put in and supported by the bearing part 4b. Inside the gear housing 131, both front end parts of the camshafts 71, 72 for exclusive use of intake and for exclusive use of exhaust (on the left side in Fig.1 and Fig.2) are extended outward from the cam carrier member 3. Fixed to both extensions of the camshafts 71, 72 for exclusive use of intake and for exclusive use of exhaust respectively are the first and the second flange parts 141, 142 of T-shape. Provided at the outer peripheral surface of the flange part 141 of the camshaft 71 for exclusive use of intake is a gearing 143, comprising a driving gear 143a which is fixed by compression to the first flange part 141 of the camshaft 71 for exclusive use of intake and driven by the engine output shaft (not shown in the drawing) through the medium of the timing pulley 132 and a driven gear 143b which is fixed by compression to the second flange part 142 of the camshaft 72 for exclusive use of exhaust and meshes with the driving gear 143a. As the gearing 143 (driving gear 143a, driven gear 143b), a helical gearing which makes a slight meshing sound in rotation and has high transmitting capacity is used. An edge front part of the driven gear 143b of the camshaft 72 for exclusive use of exhaust is formed in T-shape (broken in annular shape). A friction gear 144 of annular shape is provided at this broken part to generate friction. A T-shape nut 146 (locking member) for fitting a dish spring 145, which presses elastically the friction gear 144 against the front surface of the broken part of the driven gear 143b, to the camshaft 72 for exclusive use of exhaust is provided forwardly of the driven gear 143b. This T-shape nut 146 contacts the front surface of the second flange part 142 and is screwed to the extension of the cam shaft 72 for exclusive use of exhaust. As the friction gear 144, a gear whose number of teeth is one tooth less than the driven gear 143b is used. By the specified elastic pressing force (friction) of the friction gear 144 against the front surface of the broken part of the driven gear 143b, backlash to be generated at each cam shaft 71, 72 is checked. Provided at the gear housing 131 is the first contact part 151 which contacts the first flange part 141 when the gear housing 131 is fitted to the front surface of the cam carrier member 3. The front surface of the second flange part 142 of the camshaft 72 for exclusive use of exhaust contacts the T-shape nut 146, and the second contact part 152 which contacts the front surface of the second flange part 142 through the medium of the T-shape nut 146, when the gear housing 131 is fitted to the front surface of the cam carrier member 3, is provided at the gear housing 131. The second contact part 152 is composed of a plated material 153 (plated steel material). In Fig. 4, reference numeral 160 designates a cover member fitted to the cam carrier member 3 so that it is located above the camshaft 72 for exclusive use of intake. Referring to the case where the camshaft 71 for exclusive use of intake and the camshaft 72 for exclusive use of exhaust are positioned in thrust direction in relation to the cam carrier member 3, each camshaft 71, 72 is inserted from the side without the gear 143 between cams (namely, from the rear end part) in relation to the front wall surface of the cam carrier member 3 through which the camshafts 71, 72 can be put so as to have each camshaft 71, 72 contact the rear surface of the first and the second flange part 141, 142 respectively. Then, the first flange part 141 of the camshaft 71 for exclusive use of intake is contacted with the first contact part 151 of the gear housing 131 and the second flange part 142 of the camshaft 72 for exclusive use of exhaust is contacted with the second contact part 152 of the gear housing 131 through the medium of the T-shape nut 146. In this state, the gear housing 131 is fitted to the cam carrier member 3 and the camshafts 71, 72 are positioned in thrust direction. The three swing arms 81, 82, 83 are made of the same material and community of parts is planned. In this case, it is suggested to concentrate the centers of rollers of the three swing arms 81, 82, 83 fitted to the engine but we do not dare to do so in order to avoid larger size of the swing arms 81, 82, 83. In the above embodiment, therefore, the camshaft 71 for exclusive use of intake is driven by the engine output shaft through the medium of the timing belt and the camshaft 72 for exclusive use of exhaust is driven by the camshaft 71 for exclusive use of intake through the medium of the gearing 143 (driving gear 143a and driven gear 143b). Thus, only one timing pulley 132 on the driven side is required and compactness of the engine is realized. In this case, since the camshaft 71 for exclusive use of intake having many valves to drive and large torque fluctuation is not gear-driven but is driven by the engine output shaft through the medium of the timing belt 133, rotation of the camshaft 71 is stabilized. Also, since the camshaft 72 for exclusive use of exhaust having less number of valves to drive and small torque fluctuation is driven through the medium of the gearing 143, it is easy to restrict rotation fluctuation of the camshaft 72 due to backlash of the driven gear 143b, for example, within the tolerance limit. Moreover, small torque fluctuation results in improving reliability of the driving gear 143a and the driven gear 143b, without taking a reinforcing measure (lengthening of width), and compactness of the engine can be promoted. Furthermore, since the camshaft 72 for exclusive use of exhaust can be positioned in thrust direction in relation to the cam carrier member 3 by simple composition (the second contact part 152 which contacts the T-shape nut 146 (second flange part 142) with the gear housing 131 is composed of the plated material 153), a thrust plate which is located on the cylinder head side, a bolt which locks the thrust plate to the cylinder head, etc., can be dispensed with. Thus, assembling work including positioning the camshafts 71, 72 can be done easily. The present invention is not limited to the above embodiment but includes various modifications, for example, in the above embodiment three intake valves and two exhaust valves are provided but the number of exhaust valves can be increased. In short, the present invention can be safely applied to the engine, so far as the engine is provided with a plurality of valves at least as the intake valve or as the exhaust valve. In the above embodiment, the camshaft 72 having less valves to drive is driven by the belt transmitting mechanism with the timing belt 133 but can be driven by the chain transmitting mechanism with the timing chain. Furthermore, in the above embodiment the T-shape nut 146 in used as a locking member but conventional nuts and bolts can be used. Also, only the dish spring 145 for pressing the friction gear 144 against the front surface side of the driven gear 143b is fitted by the T-shape nut 146 but a T-shape nut for fitting a driven gear (which cannot be fitted to the second flange part by compressing), together with a dish spring, can be used. Also, in the above embodiment the second contact part 152 of the gear housing 131 is composed of the plated material 153 but any material can be used, so far as it has good wear-resistance and is compatible with the T-shape nut, for the second contact part 152. In the above embodiment, the present invention is stated about the case where it is applied to the V-type engine but is applicable to a vertical type engine.

Claims: A valve driving device of an engine having a single camshaft (71) for exclusively driving more than one intake valve (31, 32, 33) and a single camshaft (72) for exclusively driving more than one exhaust valve (41, 42) at each cylinder (5), the two camshafts (71, 72) being supported by multiple bearing parts (4a, 4b) on a cylinder head (2, 3) of the engine and each extending outwardly with respect to an outer front wall surface of the cylinder head (2, 3) whereby the extended end portions of the two camshafts (71, 72) are provided with intermeshing gears (143a, 143b) of a gearing (143) which is arranged within a gear housing (131) and which is drivably connected to an output shaft of the engine by a transmitting member (132, 133), characterized in that the number of intake valves (31, 32, 33) is different from the number of exhaust valves (41, 42); the transmitting member (132, 133) is connected to the gearing (143) at the camshaft (71) which drives the larger number of either the intake (31, 32, 33) or the exhaust (41, 42) valves; the extended end portion of the camshaft (72) which drives the lesser number of either the intake (31, 32, 33) or the exhaust (41, 42) valves is provided with a flange part (142) for fixing its co-operative gear (143b) of the gearing (143) together with a separate friction gear (144) coaxially arranged at an outer face thereof and which flange part (142) is in contact with the outer front wall surface of the cylinder head (2, 3); the friction gear (144) is fixed against the outer face of its adjacent gear (143b) by a locking member (146) which is in contact with the gear housing (133). A valve driving device as claimed in claim 1 wherein the locking member (146) is in contact with the gear housing (131) through a separate contact part (153) made of a plated steel material. A valve driving device as claimed in claim 1 or claim 2 wherein the locking member (146) is a nut member (146) screwed to the extended end portion of the camshaft (72) which drives the lesser number of valves (41, 42). A valve driving device as claimed in any of the claims 1 to 3 wherein the extended end portion of the camshaft (71) which drives the larger number of valves (31, 32, 33) is provided with a flange part (141) for fixing its cooperated gear (143a) of the gearing (143) whereby the flange part (141) is in contact with the gear housing (131).

Inventors: HASHIMOTO KAZUHIKO, IWATA NORIYUKI, SADO OSAMU, UESUGI TATSUYA, HASHIMOTO, KAZUHIKO, IWATA, NORIYUKI, SADO, OSAMU, UESUGI, TATSUYA
Applicants: MAZDA MOTOR, MAZDA MOTOR CORPORATION
Application year: 1990
Main classification: F01L1
IPC codes: F01L1, F02B75