Abstract: An SOHC-type valve operating system in an internal combustion engine having a single cam shaft commonly provided for a pair of intake valves and a pair of exhaust valves. A plurality of intake valve driving members are rockably disposed between the cam shaft and the pair of intake valves and have an operative-connection switchover mechanism for switching over the connection and disconnection of the intake valve driving members. A pair of exhaust valve driving members are rockably disposed between the cam shaft and the pair of exhaust valves and independently operate each of the exhaust valves. The operative-connection switchover mechanism includes a switchover pin movable between a position for operatively connecting adjacent intake valve driving members and a position for releasing such connection, which pin is slidably mounted in a cylindrical sleeve secured to the intake valve driving members for guiding the movement of the switchover pin.

Abstract: An SOHC type internal combustion engine comprises a pair of intake valves and a pair of exhaust valves, which are carried in a cylinder head, for opening and closing operation, at a small angle formed by axes of both the pairs of the valves in a projected view on a plane perpendicular to a crankshaft axis including an axis of a cylinder, a single cam shaft rotatably disposed above a combustion chamber, a single rocker shaft fixedly disposed above the combustion chamber, a plurality of intake rocker arms interposed between the cam shaft and the pair of intake valves and swingably carried on the rocker shaft, a pair of exhaust rocker arms interposed between the rocker shaft and the pair of exhaust valves and swingably carried on the rocker shaft, and a plug insertion cylindrical portion which is provided in the cylinder head between both the exhaust valves and into which is inserted a spark plug disposed at a substantially central portion of a ceiling surface of the combustion chamber.

Abstract: A valve operating device for operating an intake or exhaust valve in an internal combustion engine includes a cam having a cam profile including a valve lifting portion for applying a force to open the engine valve and a base circle portion for allowing the valve to be closed, the cam profile having a valve opening point and a valve closing point between the valve lifting portion and the base circle portion, a cam follower slidably engaging the cam, and a hydraulic lash adjuster combined with the cam follower for eliminating any gap between the means and the engine valve. The base circle portion has a gradient cam surface or a combination of different gradient cam surfaces for canceling out valve-lifting radial displacement of the base circle portion.

Abstract: A mechanism for switching valve operating modes in an internal combustion engine that has a valve operating mechanism with high- and low-speed cams having different cam profiles corresponding to rotational speed ranges of the engine, a pair of valves disposed in intake or exhaust ports of a combustion chamber and a normally urged to be closed by spring means, a directly moving transmitting member for imparting the lift of the low-speed cam to the valve, a pair of idling transmitting members for transmitting the lift of said high-speed cam on the pair of valves and a selective coupling mechanism for selectively connecting the transmitting members when mutually adjacent portions of the transmitting members are in a predetermined positional relationship.

Abstract: A valve-operating system for an internal combustion engine, which system includes a valve-driving piston slidably received in a cylinder body and operatively connected at one end of the piston to an engine valve spring-biased in a closing direction. A check valve and an orifice are interposed between a hydraulic pressure generating means for generating an oil pressure for causing opening of the engine valve and a damper chamber defined between the cylinder body and the valve-driving piston. The check valve permits only the flow of working oil from the hydraulic pressure generating means to the damper chamber. The orifice restricts the return of working oil from the damper chamber to the hydraulic pressure generating means. The orifice is made sufficiently short relative to its width to reduce the influence due to viscosity variations of the working oil to an extremely small level.

Abstract: An oil reservoir structure for an engine having an oil reservoir chamber attached to the lower end of the cylinder block of the engine. A volume body having a predetermined volume is located in the space defined between the crankshaft of the engine and the normal oil level in the oil reservoir chamber. The volume body becomes submerged upon tilting of the oil level, such as in vehicle turning, acceleration, deceleration or on inclines, to displace a volume of oil to raise the oil level and maintain the oil level above the oil strainer inlet leading to the oil pump. The volume body may be fixedly mounted or disposed on the oil level and vertically movable in response to a change in the oil level.

Abstract: A valve operating mechanism for an internal combustion engine having a crankshaft and a plurality of intake or exhaust valves normally biased in a valve closing direction includes a rocker shaft, a cam rotatable in synchronism with the crankshaft, a plurality of rocker arms swingably supported on the rocker shaft in association with the valves, respectively, and swingable by the cam, a coupling device for selectively connecting and disconnecting adjacent ones of the rocker arms under hydraulic pressure, and a hydraulic circuit openable and closable according to a rotational speed of the engine for selectively supplying hydraulic pressure to the coupling device. The opening and closing of the hydraulic circuit are controlled in view of a delay in operation thereof based on an angular displacement of the crankshaft or the cam so that the coupling device will be inoperative when the rocker arms are in a predetermined initial interval of a valve opening stroke thereof.

Abstract: A hydraulic circuit for a valve operation timing control device for an internal combustion engine which has a low-speed cam having a shape suited for low-speed operation of the engine, a high-speed cam having a shape suited for high-speed operation of the engine, the low- and high-speed cams being integrally formed on a camshaft rotatable in synchronism with a crankshaft, a first rocker arm held in slidable contact with the low-speed cam, a second rocker arm held in slidable contact with the high-speed cam. The first and second rocker arms are adjacent to and in slidable contact with each other and pivotably supported on a rocker shaft for relative angular displacement. There is a first oil feed passage for lubricating the low-speed cam and a second oil feed passage for lubricating the high-speed cam.

Abstract: A valve operating mechanism for an internal combustion engine has a low-speed cam for operating the intake or exhaust valves during low-speed operation of the engine and a high-speed cam for operating the intake or exhaust valves during high-speed operation of the engine. A low-speed lubricating oil passage is provided for supplying lubricating oil to the low-speed cam and a separate high-speed lubricating oil passage is provided for supplying lubricating oil to the high-speed cam. A control valve is connected to said low-speed and high-speed lubricating oil passages for selectively supplying maximum oil pressure to the high-speed lubricating oil passage during high-speed operation while restricting the rate of flow of oil during low-speed operation of the engine and supplying maximum oil pressure to the low-speed lubricating oil passage during low-speed operation of the engine while restricting or eliminating the oil supplied thereto during high-speed operation.

Abstract: A hydraulic circuit for a valve operating mechanism for an internal combustion engine which has a plurality of intake or exhaust valves normally urged in a valve closing direction, a plurality of adjacent rocker arms associated respectively with the intake or exhaust valves and pivotably supported on a rocker shaft. The rocker arms are pivotable by cams rotatable in synchronism with a crankshaft. A coupling mechanism is provided in the rocker arm selectively interconnecting and disconnecting adjacent rocker arms in response to oil pressure. A hydraulic circuit supplies oil pressure to the coupling means and an oil feed passage lubricates the cams.

Abstract: In the case of a cam shaft drive structure in which a cogged belt is passed around a pair of cam shaft pulleys for two cylinder banks of an OHC V-type engine and a crank shaft pulley, it has been widely believed that the tension of the cogged belt resulting from the longitudinal vibration of the cogged belt can be minimized by reducing the masses of the cam shaft pulleys to a least possible value. However, it was discovered by the inventors that it is not necessarily the case and on the contrary a favorable result can be obtained by selecting the moment of inertia of the cam shaft pulley on the tight side to be greater than the moment of inertia of the cam shaft pulley on the slack side. The reverse surface of the cogged belt can be conveniently utilized for driving accessory equipment and for engaging an idler pulley thereto.

Abstract: A crankshaft supporting structure in a multicylinder internal combustion engine has a cylinder block made of a light alloy and including a cylinder housing and a crankcase having a plurality of spaced journal walls. A plurality of spaced bearing caps made of an iron alloy are coupled respectively to the journal walls. A crankshaft is rotatably supported in bearing holes defined by the journal walls and the bearing caps. A bridge made of a light alloy extends across the bearing caps and is coupled to the bearing caps. The bearing caps and the bridge are fastened together to the journal walls by connecting bolts disposed one on each side of the crankshaft. The bridge has a main portion defining a main gallery extending longitudinally therethrough and a plurality of legs coupled to the bearing caps, respectively. The bearing caps and the legs jointly define branch oil passages communicating with the main gallery and the bearing holes.

Abstract: A crankshaft support structure for a multicylinder internal combustion engine employing a plurality of bearihng caps with pairs of vertical and horizontal surfaces fitting mating surfaces in the cylinder block for structurally mating the bearing caps to the cylinder block. A structural bridge extends across the bearing caps and is connected through the bearing caps to the block by one set of bolts and directly to the block by a second set of bolts. A second embodiment employs a third set of bolts connecting the bearing caps separately to the block. Arcuate baffle plates form the portion of the bridge between bearing caps to inhibit oil agitation and suppress noise.

Abstract: A crankshaft support for a multicylinder internal combustion engine employing a plurality of bearing caps fitted in recesses in journal walls in the cylinder block and connected by pairs of bolts extending vertically through each bearing cap into the journal wall. An additional pair of bolts extend horizontally from each side of the cylinder block to connect the skirt portions to the bearing caps. A bridge extends the length the engine over the bearing caps and is connected thereto by another pair of vertical bolts.

Abstract: A crankcase blow-by gas breather device and arrangement where the ends of the crankcase are provided with spaces beyond the end supporting walls for the crankshaft, which spaces conduct the blow-by gas directly to a breather chamber for separating at least some of the entrained oil. The breather chamber is connected to the overhead valve chambers which, in turn, are connected to the intake system for recycling the blow-by gases to the engine. In a V-type engine the breather chamber is integrally formed in the bottom wall of the "V".

Abstract: There is disclosed a lubricant feed system for use in a journal of a crankshaft comprising first bearing supporting portions formed in a cylinder block, each having a peripheral surface, second bearing supporting portions formed in caps, each having a peripheral surface, first bearings in the form of half shells arranged on the peripheral surfaces of the first bearing supporting portions, second bearings in the form of half shells arranged on the peripheral surfaces of the second bearing supporting portions and an oil main gallery. In this arrangement, annular grooves are formed on the peripheral surfaces of the first and second bearing supporting portions and oil grooves are circumferentially formed at the inner peripheral surfaces of the first bearings. Apertures are formed at the first bearings to communicate the annular grooves with the oil grooves. The inner peripheral surfaces of the second bearings are made flat.

Abstract: A DOHC engine of the V-type has two cylinder heads each detachably secured to a cylinder block. A crank shaft on the block drives two intermediate shafts, one on each cylinder head, by means of an endless flexible element. An additional flexible endless element is provided in each cylinder head to drive two cam shafts from the intermediate shaft on that cylinder head. Each endless flexible element together with its toothed pulleys or sprockets and its timing belt or chain is described as a wrap-around transmission.