JPS6325292Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to the structure of a camshaft that opens and closes intake and exhaust valves of an engine, and particularly relates to a lubrication structure for the bearing portion of the camshaft.

(Prior Art) Conventionally, as a camshaft structure for this type of engine, as disclosed in, for example, Japanese Patent Laid-Open No. 55-37552, the camshaft of the engine is hollow and an oil gear rally is formed inside it. At the same time, by forming a branch passage (lubricating oil supply passage) that communicates the oil gear rally with the outer periphery of each journal part, lubricating oil is force-fed from the oil gear rally to the journal part via the branch passage to lubricate the bearing part of the camshaft. Structures that allow this to occur are known. When branch passages are formed in the journal portion of the camshaft in this manner, from the viewpoint of workability, usually all the branch passages are opened in the same direction with respect to the camshaft.

(Problem to be solved by the invention) By the way, in order to reduce the inertial mass of the intake and exhaust valves of the engine and increase the speed and output of the engine, at least one of the intake and exhaust valves per cylinder is In an engine that has two valves that are opened and closed simultaneously by two cams installed on the same camshaft, the intake and exhaust When the valve is moved to the center of the cylinder, the camshaft is also placed to the center of the cylinder.In order to avoid interference with the head bolts located between each cylinder, the journal part of the camshaft is moved between the two points above. It is provided between the cams.

In that case, in order to make the opening and closing operations of the two valves accurately follow the rotation of the cam up to the high speed range of the engine,
Because the spring force of the valve springs that bias each valve to close is set relatively strong, when both valves open due to the lift of the cam, both cams receive a large reaction force from the valve springs and close. Pushed in the direction of the valve, the journal located between the two cams partially bends with respect to the central axis of the camshaft, and the clearance between the outer peripheral surface on the valve side and the bearing becomes larger than the normally required clearance. A phenomenon occurs.

Therefore, if the branch passages that open on the outer periphery of the journal part are all opened in the same direction relative to the camshaft as in the conventional example above, the opening and closing timing of the valves will differ in each cylinder, so the journal part of the camshaft corresponding to a certain cylinder will Then, a branch passage is opened in the increased clearance, and lubricating oil excessively flows out through the increased clearance, and the oil pressure supplied to the journal corresponding to other cylinders decreases. There was a risk that the parts would lack lubrication.

The present invention was developed in view of these points, and its purpose is to provide branch passages for pressure-feeding lubricating oil from the oil gear rally in the camshaft to the journal between the two cams. , by opening in a specific direction relative to the cams on the sides of the journal, to avoid the opening of the branch passage corresponding to the increased clearance between the journal and the bearing when both cams are lifted. Therefore, the object is to prevent oil pressure from decreasing due to excessive outflow of lubricating oil from the branch passage.

(Means for Solving the Problem) In order to achieve the above object, the solution of the present invention is to provide at least two intake/exhaust valves per cylinder, and to connect the two valves to the same valve. In the engine camshaft structure, the camshaft is opened and closed by two cams provided on the camshaft, and lubricating oil is force-fed from an oil gear rally in the camshaft to a journal part of the camshaft through a branch passage, wherein the camshaft is rotatable. The journal portion for supporting is disposed between the two cams, and the branch passage at each journal portion is connected to the base circle portion of the cam adjacent to the journal portion, that is, a portion other than the buffer portion and the lift portion. The opening is made in the overlapping part (the part corresponding to the base circle part) when viewed from the axial direction.

(Function) With the above configuration, in the present invention, when both cams lift as the camshaft rotates to open both valves, the reaction force from the valve spring causes both cams of the camshaft and the journal portion between them to open. Even if the clearance at the valve stem between the journal part and the bearing part increases due to partial deflection in the valve closing direction,
The opening of the branch passage does not face the increased clearance, thereby preventing excessive outflow of lubricating oil from the clearance.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings.

Figure 2 shows the direct drive system according to the embodiment of the present invention.
Part of the DOHC type 4-cylinder engine is shown, 1, 1,
...are four cylinders formed by a cylinder head 2 and a cylinder block (not shown), 3
4 is an intake valve that opens and closes the downstream end opening of an intake passage (not shown) for supplying intake air into the combustion chamber of each cylinder 1, and 4 is an exhaust passage (not shown) for discharging exhaust gas from each combustion chamber. The intake valve 3 and the exhaust valve 4 are provided in each half of each cylinder 1, two for each cylinder.

On the upper surface of the cylinder head 2, there are intake and exhaust camshafts 5, 5 that extend parallel to each other in the cylinder row direction (in the figure, the upper camshaft 5 is the intake camshaft, and the lower camshaft 5 is the exhaust camshaft, respectively). ) are divided into two bearing parts 6, 6 on the upper and lower surfaces of the cylinder head 2, respectively.
Each camshaft 5 is rotatably supported by being fitted into the engine, and each camshaft 5 is rotationally driven in synchronization with the crankshaft (not shown) of the engine. Further, each camshaft 5 has two cylinders in each cylinder 1.
Two cams 7, 7 are formed to simultaneously open and close two intake valves 3, 3 or exhaust valves 4, 4, and each journal portion 5a is located between the two cams 7, 7, that is, corresponds to each cylinder 1. It is located in the same position.

Further, as shown in enlarged detail in FIGS. 1 and 3, each of the camshafts 5 is formed in a hollow shape,
An oil gear rally 8 to which lubricating oil is pumped is formed inside. In addition, each camshaft 5
The above oil gear rally 8 is attached to each journal part 5.
The outer peripheral surface of a, that is, the bearing portion 6 of the cylinder head 2
Branch passages 9, 9, which communicate with the surface that comes into sliding contact with the inner surface.
... is formed, and this branch passage 9 carries lubricating oil from the oil gear rally 8 to each journal portion 5a.
Each journal portion 5a and bearing portion 6 are compressed to the outer periphery.
It is designed to lubricate the gap between the

The branch passages 9 are connected to the base circle portions 7a of the two cams 7, 7 adjacent to the journal portions 5a on the outer peripheral surface of the journal portions 5a,
Of the parts that overlap with cam 7a when viewed from the 5-axis direction of the camshaft (the part shown by range A in Fig. 3), cam 7,
The cam top portions 7b and 7b are opened at positions corresponding to the back side of the cam top portions 7b and 7b.

In Fig. 2, 10 is a head bolt for joining the cylinder head 2 to the cylinder block;
1 is a fixing bolt for fixing the upper half of each bearing part 6 to the lower half; 12 is a spark plug mounting hole for mounting a spark plug (not shown) facing the top of each cylinder 1; 13 is each This is a tappet interposed between the intake/exhaust valves 3 and 4 and the cam 5. Also, in Figure 3, 1
4 is a valve spring that biases the intake valve 3 (exhaust valve 4) in the valve-closing direction.

Therefore, in the above embodiment, the two cams 7, 7 corresponding to each cylinder 1 are lifted by the rotation of each camshaft 5, and the two intake valves 3, 3 or the exhaust valves 4, 4 are moved by the valve springs 14, 4. When the valves are simultaneously opened against the biasing force of the valve springs 14, the two cams 7, 7 and the journal portion 5a between the cams 7, 7 move against the camshaft 5 due to the reaction force from the valve springs 14, 14. The journal portion 5a is partially displaced in the valve closing direction with respect to the central axis of the journal portion 5a.
Due to the displacement of In this case, from the oil gear rally 8 in each camshaft 5 to each journal part 5
Each branch passage 9 for supplying lubricating oil under pressure to a
However, in the journal part 5a, the journal part 5
The branch passages 9, 9, .
This prevents the lubricating oil from excessively flowing out from the increased clearance, thereby distributing the lubricating oil to all the journal parts 5a of the camshaft 5.
5a, ... evenly to the journal parts 5a, 5.
A, ... can be stably lubricated.

In the above embodiment, each branch passage 9 was provided in a portion of the journal portion 5a corresponding to the back side of the cam top portions 7b, 7b of the two cams 7, 7 adjacent to the journal portion 5a. Of course, it may be provided at any portion of the base circle portions 7a, 7a of No. 7 as long as it overlaps with the base circle portions 7a, 7a when viewed from the axial direction (the portion indicated by range A in FIG. 3).

Further, the above embodiment is an example applied to an engine equipped with two intake/exhaust valves 3 and 4 per cylinder, but the present invention has two intake/exhaust valves per cylinder. Of course, the present invention can also be applied to other engines.

Furthermore, it goes without saying that the present invention can be applied to engines with three or less cylinders or five or more cylinders, in addition to the four-cylinder engine as in the above embodiment.

(Effects of the invention) As described above, according to the invention, two cams for opening and closing the two intake valves or exhaust valves provided per engine cylinder are provided on the same camshaft, and a journal is provided between the two cams. At the same time, a branch passage for supplying lubricating oil from the oil gear rally in the camshaft to each of the journal parts is opened at a portion of each journal part corresponding to the base circle part of the adjacent cam. Even if the clearance between the journal part and the bearing part increases due to the reaction force from the valve spring when both cams are lifted, lubricating oil is prevented from excessively flowing out from the increased clearance to other journal parts. It is possible to prevent a decrease in the oil pressure supplied to the engine, thereby stably maintaining the lubricating effect on the camshaft of the engine.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is a front view of the main parts of a camshaft, FIG. 2 is a plan view of the main parts of the engine, and FIG. 3 is a sectional view taken along the line -- in FIG. 1...Cylinder, 3...Intake valve, 4...Exhaust valve, 5
...Camshaft, 5a...Journal section, 7...
...Cam, 8...Oil gear rally, 9...Branch passage, 14...Valve spring.

Claims (1)

[Scope of utility model registration request] At least two intake/exhaust valves are provided per cylinder, and the two valves are opened and closed by two cams provided on the same camshaft, and branched from an oil gear rally provided within the camshaft. In an engine camshaft structure in which lubricating oil is force-fed to a journal part of a camshaft through a branch passage, the camshaft is rotatably supported by a journal part disposed between the two cams, and all of the branch passages are A camshaft structure for an engine, characterized in that the passage is opened in a portion of the journal portion that overlaps a base circle portion of a cam adjacent to the journal portion when viewed from the axial direction.