JP2015194114A - Internal combustion engine valve gear mechanism cam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress release of coating due to the point contact of a driver with the side edge of a cylindrical surface of a cam at a time of switching a valve opening state to a valve closing state.SOLUTION: A cam 6 of a valve gear mechanism of an internal combustion engine used to drive an intake valve or an exhaust valve of the internal combustion engine to be opened or closed comprises: a cam lobe pressing a driver driving a valve body of the intake valve or the exhaust valve; a cylindrical surface 62a continuous to the cam lobe, constituting part of a base circle, and proximate to the driver; an inclined surface 62b located laterally to the cylindrical surface 62a, directed in a direction of inclining with respect to an axial direction, expanding along a circumferential direction; and a protective portion 62c obtained by chamfering a corner in which the cylindrical surface 62a crosses the inclined surface 62b or forming the corner into an R-corner and extending along a circumferential direction without interruption.

Description

  The present invention relates to a cam for a valve mechanism of an internal combustion engine.

  2. Description of the Related Art Conventionally, in an internal combustion engine, there is known a valve operating mechanism that presses a valve body, typically a valve lifter, to open and close an intake valve or an exhaust valve by a cam lobe of a rotating cam.

  In such a valve operating mechanism, the drive body is urged together with the valve body by a spring toward the valve closing side, and when opening the intake valve or the exhaust valve, the cam lobe resists the urging force of the spring to lift the valve lifter. Press down.

  Further, in order to reduce the weight of the cam, it has been practiced to chamfer both sides of the cylindrical surface forming the base circle of the cam to cut the meat (for example, see Patent Document 1).

JP 2001-82111 A

  For the purpose of reducing friction loss as much as possible in the valve mechanism, the cam and the drive are operated so that a clearance exists between the base circle of the cam and the drive body when the intake valve or the exhaust valve is closed. It is conceivable to design the relative position with the body.

  On the other hand, in this type of valve operating mechanism, a strong spring is always applied toward the valve closing side with a strong spring so that the valve body is securely seated on the valve seat and the intake port or exhaust port is securely closed. Giving power. For this reason, the drive body may collide with the cam in spite of providing a clearance when the valve opening state is changed to the valve closing state. Moreover, at the moment of the collision, the contact surface of the driving body with respect to the cam, typically the top surface of the valve lifter and the axis passing through the center of the base circle of the cam are not necessarily parallel to the cylindrical surface of the cam. The cam contact surface of the inclined driving body may touch the side edge of the cylindrical surface of the cam in a dotted line.

  Then, the friction reducing coating (for example, DLC (Diamond Like Carbon) coating) applied to the contact surface of the drive body with respect to the cam may be peeled off. When such a coating is peeled off, a mechanical loss due to an increase in friction between the driving body and the cam lobe occurs, resulting in deterioration of fuel consumption.

  The present invention pays attention to the above points, and suppresses the peeling of the coating due to the dotted line touching the side edge of the cylindrical surface of the cam when the valve is changed from the open state to the closed state, thereby reducing the fuel consumption. The purpose is to stop.

  In order to solve the above problems, the valve operating mechanism of the internal combustion engine according to the present invention has the following configuration. That is, the valve mechanism of the internal combustion engine according to the present invention is a cam for the valve mechanism used for opening / closing driving of the intake valve or exhaust valve of the internal combustion engine, and drives the valve body of the intake valve or exhaust valve. A cam lobe that presses the cam lobe, forms a part of the base circle and is connected to the cam lobe, and is adjacent to the drive body, and a direction that is located on the side of the cylindrical surface and is inclined with respect to the axial direction is the circumferential direction. An inclined surface extending along the corner and a corner where the cylindrical surface and the inclined surface intersect are chamfered or R is added to the corner, and the protective portion extends without interruption along the circumferential direction. And.

  If this is the case, even when the driving body collides with the cam when the valve is opened, the protective portion is provided at the corner where the cylindrical surface and the inclined surface intersect. The coating peeling due to the dotted line contact between the cam contact surface and the cam can be suppressed.

  According to the present invention, when the valve body of the intake valve or the exhaust valve is changed from the open state to the closed state, the driving body that drives the valve body of the intake valve prevents the peeling of the coating due to the dotted line touching the side edge of the cylindrical surface of the cam As a result, deterioration of fuel consumption can be prevented.

1 is a schematic view of an upper part of a cylinder of an internal combustion engine according to an embodiment of the present invention. The side view of the cam which concerns on the same embodiment. AA sectional drawing in FIG. The enlarged view of the principal part in FIG.

  One embodiment of the present invention will be described below with reference to FIGS.

  The vehicle internal combustion engine of the present embodiment is a spark ignition type four-stroke engine and includes a plurality of cylinders. FIG. 1 is an enlarged view of the upper part of one of the cylinders 1. In the figure, reference numeral 1 is a cylinder, reference numeral 2 is an intake port, reference numeral 3 is an intake valve, reference numeral 4 is an exhaust port, and reference numeral 5 is an exhaust valve. An injector (fuel injection valve; not shown) in the internal combustion engine may be a port injection type that injects fuel into the intake port 2 or in-cylinder injection that directly injects fuel into the combustion chamber of the cylinder 1. It may be of the formula.

  As shown in FIG. 1, the intake valve 3 is a poppet valve that closes the end portion of the intake port 2 when the valve body 30 is seated on a valve seat 21 that is a valve seat at the end portion of the intake port 2. The valve body 30 has a dish shape and is formed integrally with one end of a rod-shaped valve stem 31. The other end of the valve stem 31 is connected to a valve lifter 33 via a shim 32. The valve lifter 33 is a driving body that transmits an action for opening and closing the valve body 30 via the shim 32 and the valve stem 31 to drive the valve body 30.

  The valve body 30, the valve stem 31, the shim 32 and the valve lifter 33 of the intake valve 3 are elastically urged in the valve closing side, that is, the direction in which the valve body 30 is seated on the valve seat 21 by a coil spring 35 as urging means. . A spring retainer 34 is interposed between the coil spring 35 and the valve lifter 33. The spring retainer 34 is disposed so as to surround the valve stem 31. One end of the coil spring 35 is supported on a wall surface at a predetermined location of the cylinder head, and the other end is supported on a proximal end portion of the spring retainer 34.

  The valve lifter 33 has a cylindrical shape with one opening, and is attached to the valve stem 31 via a shim 32 so as to accommodate the valve stem 31 and the coil spring 35 therein. The top surface 33a of the valve lifter 33 is provided with a coating for reducing friction, for example, DLC coating.

  A cam 6 exists above the top surface 33 a of the valve lifter 33. The cam 6 is fixed to the camshaft 7. The cam 6 and the camshaft 7 are rotated by receiving a rotational driving force from a crankshaft (not shown) of the internal combustion engine via a winding transmission mechanism (timing belt or timing chain). The cam profile of the cam 6 has a known configuration having a cam lobe 6a and a base circle 6b as shown in FIGS.

  Further, as shown in FIG. 1, the exhaust valve 5 of the internal combustion engine of the present embodiment has the same configuration as the drive mechanism of the intake valve 3. That is, the exhaust valve 5 is a poppet valve that closes the start end portion of the exhaust port 4 when the valve body 50 is seated on a valve seat 41 that is a valve seat at the start end portion of the exhaust port 4. The valve body 50 has a dish shape and is formed integrally with one end of a rod-shaped valve stem 51. The other end of the valve stem 51 is connected to the valve lifter 53 via a shim 52. The valve lifter 53 is a drive body that transmits an action for opening and closing the valve body 50 via the shim 52 and the valve stem 51 to drive the valve body 50.

  The valve body 50, the valve stem 51, the shim 52, and the valve lifter 53 of the exhaust valve 5 are also elastically urged in the valve closing side, that is, the direction in which the valve body 50 is seated on the valve seat 41 by the coil spring 55 that is the urging means. . A spring retainer 54 is also interposed between the coil spring 55 and the valve lifter 53.

  The valve lifter 53 has the same configuration as the intake-side valve lifter 33. The top surface 53a of the valve lifter 53 is also provided with a coating for reducing friction, such as a DLC coating. The cam 6 is also present above the top surface 53a of the valve lifter 53 on the exhaust side.

  More specifically, as shown in FIGS. 2 to 4, the cam 6 includes a cam lobe portion 61 that forms a cam lobe 6a that presses the valve lifters 33 and 53, and a base circle portion 62 that forms a part of the base circle 6b. Become. The base circle portion 62 is connected to the cam lobe 6a to form a part of the base circle 6b, and is adjacent to the valve lifters 33 and 53, and is located on the side of the cylindrical surface 62a and inclined with respect to the axial direction. And an inclined surface 62b extending along the circumferential direction, and a protective portion 62c provided at a corner where the cylindrical surface 62a and the inclined surface 62b intersect. The protection part 62c is a chamfered corner and extends without interruption along the circumferential direction. In addition, when the valve is closed, a clearance exists between the base circle portion 62 of the cam 6 and the valve lifters 33, 53. In other words, the cylindrical surface 62a and the top surfaces 33a, 53a of the valve lifters 33, 53 The relative positions of the cam 6 and the valve lifters 33 and 53 are designed so that they come close to each other without sliding.

  In this embodiment, the valve lifter 33 of the intake valve 3 and the valve lifter 53 of the exhaust valve 5 are subjected to exactly the same action by the cam 6 and operate in exactly the same manner. Hereinafter, the operation of the valve lifter 33 of the intake valve 3 by the cam 6 and the state of the cam 6 at that time will be described.

  When the intake valve 3 is opened, the cam lobe 6 a of the cam 6 and the top surface 33 a of the valve lifter 33 come into contact with each other, and the valve lifter 33 is pushed down against the biasing force of the coil spring 35.

  Thereafter, when the cam lobe 6a is brought into contact with the top surface 33a of the valve lifter 33 and the cylindrical surface 62a is moved to the state facing the top surface 33a of the valve lifter 33, the valve lifter 33 is pushed up by the urging force of the coil spring 35. The valve body 30 is seated on the valve seat 21.

  In the middle of this, the valve lifter 33 receives a strong biasing force from the coil spring 35, and may hit the side edge of the cylindrical surface 62a of the cam 6 or its vicinity in an inclined posture. However, in the present embodiment, since the protective portion 62c is provided without interruption at the side edge of the cylindrical surface 62a, in other words, at the portion where the cylindrical surface 62a and the inclined surface 62b intersect, the valve lifter 33 faces the protective portion 62c. Collide with each other, or collide with a portion where the cylindrical surface 62a and the protection portion 62c intersect. As described above, since the protective portion 62c is formed by chamfering the corner where the cylindrical surface 62a and the inclined surface 62b intersect, the angle formed between the cylindrical surface 62a and the protective portion 62c is the same as that of the cylindrical surface 62a. It is larger than the angle formed by the inclined surface 62b.

  That is, according to the present embodiment, even if the valve lifters 33 and 53 hit the vicinity of the side edge of the cylindrical surface 62a of the cam 6, the protective portion 62c is provided at this portion. Therefore, as described above, the cylindrical surface 62a Even if it may collide with a portion where the protective portion 62c intersects, the angle formed by the cylindrical surface 62a and the inclined surface 62b is larger, so that only the inclined surface 62b is provided on the side of the cylindrical surface 62a. In comparison, peeling of the coating applied to the top surfaces 33a and 53a of the valve lifters 33 and 53 due to the dotted contact of the valve lifters 33 and 53 with the side edges of the cylindrical surface 62 of the cam 6 can be suppressed, and as a result Can be prevented.

  Further, since the protective part 62c is provided without interruption in the entire area where the cylindrical surface 62a and the inclined surface 62b intersect, the top surfaces 33a and 53a of the valve lifters 33 and 53 are located with respect to the cylindrical surface 62a. Even if it is pressed by the cam lobe 6a in an inclined state, only a part of the valve lifters 33 and 53 are not pressed strongly, and vibration and noise can be reduced.

  The present invention is not limited to the embodiment described above.

  For example, in the above-described embodiment, the base circle is formed thinner than the cam lobe, but the thickness dimension of each part may be arbitrarily set such that the entire thickness dimension is uniform.

  In addition to the valve mechanism that opens the valve by pushing down the valve lifter with the cam, the cam applies an operating force to one end of the rocker arm, which is the object to be driven, and transmits the operating force from the rocker arm to the valve. Of course, the present invention may be applied to the cam of the valve mechanism that opens the valve.

  In addition, in the above-described embodiment, the protective portion is provided by further chamfering the portion where the cylindrical surface and the inclined surface intersect, but by adding R to the corner portion where the cylindrical surface and the inclined surface intersect. Of course, a protective part may be provided.

  In addition, various changes may be made without departing from the spirit of the present invention.

3 ... Intake valve 5 ... Exhaust valve 30, 50 ... Valve body 33, 53 ... Driver (valve lifter)
6 ... Cam 6a ... Cam lobe 6b ... Base circle 62a ... Cylindrical surface 62b ... Inclined surface 62c ... Protection part

Claims (1)

A cam for a valve mechanism used for opening and closing an intake valve or an exhaust valve of an internal combustion engine,
A cam lobe for pressing a drive body that drives a valve body of an intake valve or an exhaust valve;
A cylindrical surface connected to the cam lobe and forming a part of the base circle and close to the driving body;
An inclined surface located on the side of the cylindrical surface and extending along the circumferential direction in a direction inclined with respect to the axial direction;
A valve for an internal combustion engine having a chamfered corner portion where the cylindrical surface and the inclined surface intersect or a corner portion with an R, and a protective portion extending without interruption along the circumferential direction. Cam for mechanism.

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