Direct-acting valve lifter of internal combustion engine

Abstract

A valve lifter with a variable lift mechanism is required to be deployed at a predetermined angle with respect to a cam unit, and the present invention is intended to achieve this requirement with a simple configuration without too much processing such as a fitting of the conventional longitudinal groove and a pin. A cam sliding contact surface of a valve lifter on which a high lift cam and a low lift cam slides is formed to be a smooth inclined surface and a cam slide starting point is lower than a cam slide terminating point, thereby establishing an elevation difference between the cam slide starting point and the cam slide terminating point. As a result, since the high lift cam and the low lift cam always move uphill on the cam sliding contact surface, namely, from the low cam slide starting point toward the high cam terminating point along the slope of the cam sliding contact surface, the valve lifter is not subjected to a force around the reciprocating axis from the cam and therefore, the direction of the valve lifter is maintained constant.

Claims

1. A cylindrical direct-acting valve lifter of an internal combustion engine with a variable lift mechanism which can switch between a high lifter comprising a high lift cam sliding surface with which a high lift cam comes into slidable contact and low lifter comprising a low lift cam sliding surface with which a low lift cam comes into slidable contact, wherein; the high lift cam sliding surface and the low lift cam sliding surface are integrally formed with an upper surface of the valve lifter and are formed as inclined surfaces whose surface roughness is smooth; each of the inclined surfaces of the cam sliding contact surfaces is formed by a flat surface inclined with respect to a plane perpendicular to a reciprocating direction of the valve lifter and a cam slide starting point on the cam sliding contact surface that is the inclined surface is positioned to be lower than a cam slide terminating point thereon; and the high lift cam and the low lift cam come into point contact with .[.a.]. .Iadd.the .Iaddend.cam slide starting point on the cam sliding contact surface that is higher than a center of the cam sliding contact surface, the high lifter and the low lifter rotate due to friction resistance generated by a rotation of the high lift cam and the low lift cam, the cam slide starting point is arrived to a lower position on the cam sliding contact surface and the rotation of the high .[.lift cam.]. .Iadd.lifter .Iaddend.and the low .[.lift cam.]. .Iadd.lifter .Iaddend.stops, and the high lift cam and the low lift cam moves along the inclined surface of the cam sliding contact surface to the cam slide terminating point that is higher than the cam slide starting point.

2. A cylindrical direct-acting valve lifter of an internal combustion engine with a variable lift mechanism which can switch between a high lifter comprising a high lift cam sliding surface with which a high lift cam comes into slidable contact and low lifter comprising a low lift cam sliding surface with which a low lift cam comes into slidable contact, wherein; the high lift cam sliding surface and the low lift cam sliding surface are integrally formed with an upper surface of the valve lifter and are formed as inclined surfaces whose surface roughness is smooth; each of the inclined surfaces of the cam sliding contact surfaces is formed by a crowned surface and a cam slide starting point on the cam sliding contact surface is positioned to be lower than a cam slide terminating point thereon; and the high lift cam and the low lift cam come into point contact with .[.a.]. .Iadd.the .Iaddend.cam slide starting point on the cam sliding contact surface that is higher than a center of the cam sliding contact surface, the high lifter and the low lifter rotate due to friction resistance generated by a rotation of the high lift cam and the low lift cam, the cam slide starting point is arrived to a lower position on the cam sliding contact surface and the rotation of the high .[.lift cam.]. .Iadd.lifter .Iaddend.and the low .[.lift cam.]. .Iadd.lifter .Iaddend.stops, and the high lift cam and the low lift cam moves along the inclined surface of the cam sliding contact surface to the cam slide terminating point that is higher than the cam slide starting point.

3. A cylindrical direct-acting valve lifter of an internal combustion engine with a variable lift mechanism which can switch between a high lifter comprising a high lift cam sliding surface with which a high lift cam comes into slidable contact and low lifter comprising a low lift cam sliding surface with which a low lift cam comes into slidable contact, wherein; the high lift cam sliding surface and the low lift cam sliding surface are integrally formed with an upper surface of the valve lifter and are formed as inclined surfaces whose surface roughness is smooth; each of the inclined surfaces of the cam sliding contact surfaces is formed by a reverse-crowned surface and a cam slide starting point on the cam sliding contact surface is positioned to be lower than a cam slide terminating point thereon; and the high lift cam and the low lift cam come into point contact with .[.a.]. .Iadd.the .Iaddend.cam slide starting point on the cam sliding contact surface that is higher than a center of the cam sliding contact surface, the high lifter and the low lifter rotate due to friction resistance generated by a rotation of the high lift cam and the low lift cam, the cam slide starting point is arrived to a lower position on the cam sliding contact surface and the rotation of the high .[.lift cam.]. .Iadd.lifter .Iaddend.and the low .[.lift cam.]. .Iadd.lifter .Iaddend.stops, and the high lift cam and the low lift cam moves along the inclined surface of the cam sliding contact surface to the cam slide terminating point that is higher than the cam slide starting point.

4. The cylindrical direct-acting valve lifter of an internal combustion engine of claim 1, wherein: a hydraulic pressure pin laterally penetrating the high lifter is provided so that the high lifter and the low lifter can be switched by moving the hydraulic pressure pin so as to insert a leading end portion into the low lifter, thereby integrating the high lifter and the low lifter, or moving the hydraulic pressure pin away from the low lifter, thereby disconnecting the high lifter and the low lifter.

5. The cylindrical direct-acting valve lifter of an internal combustion engine of claim 2, wherein: a hydraulic pressure pin laterally penetrating the high lifter is provided so that the high lifter and the low lifter can be switched by moving the hydraulic pressure pin so as to insert a leading end portion into the low lifter, thereby integrating the high lifter and the low lifter, or moving the hydraulic pressure pin away from the low lifter, thereby disconnecting the high lifter and the low lifter.

6. The cylindrical direct-acting valve lifter of an internal combustion engine of claim 3, wherein: a hydraulic pressure pin laterally penetrating the high lifter is provided so that the high lifter and the low lifter can be switched by moving the hydraulic pressure pin so as to insert a leading end portion into the low lifter, thereby integrating the high lifter and the low lifter, or moving the hydraulic pressure pin away from the low lifter, thereby disconnecting the high lifter and the low lifter.

7. The cylindrical direct-acting valve lifter of an internal combustion engine of claim 2, wherein: one half of the crowned surface with respect to a center thereof is formed as a horizontal plane and another half of the crowned surface is formed as a declivitous plane, and a border between the horizontal plane and the declivitous plane is continuously connected by a smooth curved plane.

8. The cylindrical direct-acting valve lifter of an internal combustion engine of claim 3, wherein: one half of the reverse-crowned surface with respect to a center thereof is formed as a declivitous plane and another half of the reverse-crowned surface is formed as a horizontal plane, and a border between the declivitous plane and the horizontal plane is continuously connected by a smooth curved plane.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a cross sectional view of a portion in the vicinity of a direct acting type valve lifter of an internal combustion engine that is an embodiment of the present invention.

(2) FIG. 2 is an explanatory diagram of an internal mechanism of the valve lifter shown in FIG. 1 in a low lift operation.

(3) FIG. 3 is a diagram for explaining an operation in the vicinity of the valve lifter shown in FIG. 2.

(4) FIG. 4 is an explanatory diagram of an internal mechanism of the valve lifter shown in FIG. 1 in a high lift operation.

(5) FIG. 5 is a diagram for explaining an operation in the vicinity of the valve lifter shown in FIG. 4.

(6) FIGS. 6 to 8 are explanatory functional diagrams of the valve lifter shown in 1 wherein FIG. 6 is a front view of the valve lifter and FIGS. 7 and 8 are plan views.

(7) FIGS. 9 to 11 are cross sectional views showing cam slidable surfaces of the valve lifters according to embodiments of the present invention, wherein FIG. 9 shows an example in which the cam slidable surface is constituted as a crowned surface, FIG. 10 shows an FIG. 11 shows an example in which the cam slidable surface is constituted as an inclined plane.

(8) FIGS. 12 and 13 are perspective views of the valve lifters according to other embodiments of the present invention.

(9) FIG. 14 is a cross sectional view of a conventional valve lifter and vicinity.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(10) In FIG. 1, the reference numeral 11 designates a cylinder head of an automobile engine and the reference numeral 12 designates an intake port. The reference numerals 13, 14, 15 and 16 designate an intake valve, a valve stem, a valve lifter with a variable lift mechanism and a cam, respectively. The reference numeral 16a designates a high lift cam and the reference numeral 16b designates a low lift cam. The high lift cam 16a and the low lift cam 16b are integrated with a cam shaft 17 for unitization.

(11) The reference numeral 18 designates a cylinder bore and the intake port 12 is closed by pressing the intake valve 13 against the intake port 12 using a coil spring 19 provided in the cylinder bore 18. The cam 16 (16a or 16b) is constituted so as to press the valve lifter 15 downward in FIG. 1 against the spring force of the coil spring 19, thereby opening the intake valve 13. The reference numeral 20 designates a cam sliding contact surface of the valve lifter 15. The cam 16 slides on the cam sliding contact surface 20 to push the valve lifter 15, thereby opening the intake valve 13. This operation is repeated so that the valve lifter 15 linearly reciprocates in the cylinder bore 18.

(12) The cam sliding contact surface 20 of the valve lifter 15 is provided with a high lifter 15a having a high lift cam sliding contact surface 20a and low lifters 15b, 15b having low lift cam sliding contact surfaces 20b, 20b (See FIGS. 2 to 5). These are disposed in such a manner that the high lifter 15a is sandwiched between the low lifters 15b, 15b from either side. When a hydraulic pressure pin 21 laterally penetrating the high lifter 15a is moved by hydraulic pressure, the leading end portion of the hydraulic pressure pin 21 is inserted into the low lifter 15b (See FIG. 4), whereby the high lifter 15a and the right-and-left low lifters 15b, 15b are integrated (See FIG. 5). When the hydraulic pressure pin 21 comes away from the low lifter 15b (See FIG. 2), the high lifter 15a and the low lifter 15b are disconnected from each other so that the high lifter 15a can freely move up and down with respect to the low lifter 15b (See FIG. 3).

(13) As apparent from the above, in the state shown in FIG. 3, although the high lift cam 16a is in contact with the high lift cam sliding contact surface 20a, it does not push down the valve lifter 15, in other words, it makes a blank shot. As a result, the low lift cam 16b comes into contact with the low lift cam sliding contact surface 20b and pushes down the valve lifter 15 so that the valve lifter 15 operates to produce a low lift. To the contrary, in the state shown in FIG. 5, the high lifter 15a is integrated with the low lifter 15b and the high lift cam 16a comes into contact with the high lift cam sliding contact surface 20a to push down the valve lifter 15. As a result, the valve lifter 15 operates to produce a high lift.

(14) In FIGS. 1, 2 and 4 the reference numeral 22 designates an opening for receiving oil for generating hydraulic pressure, the reference numeral 23 designates an operating pin for pushing the hydraulic pressure pin 21 and the reference numeral 24 designates a return spring for returning the high lifter 20a to its initial position (the position where the high lift cam sliding contact surface 20a and the low lift cam sliding contact surface 20b are located at the same level).

(15) Here, the cam sliding contact surface 20 (the high lift cam sliding contact surface 20a and/or the low lift cam sliding contact surface 20b) according to the present invention is configured as a smooth inclined surface.

(16) As a result, as shown in FIG. 6, the cam 16 (the high lift cam 16a or the low lift cam 16b) first comes into point contact with a high position H offset from the center of the cam sliding contact surface 20. Assuming this position H to be a cam slide starting point A, the cam 16 slides on the cam sliding contact surface 20 from point A in accordance with the rotation of the cam 16 and the cam 16 until it leaves the cam sliding contact surface 20 at cam slide terminating point B (See FIG. 7). Since a line segment connecting point A and point B is offset from the center of the cam sliding contact surface 20, the valve lifter 15 rotates owing to the friction resistance of the cam 16 in a direction from point A toward point B, namely, the direction (clockwise direction) indicated by an arrow in FIG. 7. In other words, the valve lifter 15 receives clockwise torque from the cam 16. When the valve lifter 15 rotates and the cam slide starting point A arrives at the low position L of the cam sliding contact surface 20, the direction of the friction resistance of the cam 16 from point A toward point B bisects the center line of the valve lifter 15 and no rotational force is any longer applied to the valve lifter 15, whereby the rotation of the valve lifter 15 stops.

(17) The same applies to a case where the cam 16 rotates in the reverse direction.

(18) In the case where the cam 16 rotates in the reverse direction, the cam slide starting point corresponds to point B in FIG. 8 and the cam slide terminating point corresponds to point A. At this time, the friction resistance of the cam 16 is applied in the direction from point B toward point A, whereby the valve lifter 15 rotates in the direction (counterclockwise direction) indicated by an arrow in FIG. 8. As a result, when the cam slide starting point B arrives at the low portion L of the cam sliding contact surface 20, no rotational force is any longer applied to the valve lifter 15, whereby the rotation of the valve lifter 15 stops.

(19) As apparent from the above, according to the present invention, since the cam sliding contact surface 20 is configured as an inclined surface, the cam slide starting point arrives at the low position L of the cam sliding contact surface 20 and the rotation of the valve lifter 15 stops, irrespective of the rotational direction of the cam 16.

(20) The inclined surface of the cam sliding contact surface 20 is not limited to a flat surface (See FIG. 11). The inclined surface of the cam sliding contact surface 20 may be configured as a crowned shape (See FIG. 9) or as a reverse crowned shape (See FIG. 10). In short, it is sufficient for the cam slide starting point to be lower than the cam slide terminating point, whereby an elevation difference is present between the cam slide starting point and the cam slide terminating point.

(21) As shown in FIG. 9, in the case where the inclined surface of the cam sliding contact surface 20 is formed to have the crowned shape, the cam sliding contact surface 20 is formed so that the left half thereof with respect to the center thereof is formed as a horizontal plane 25 and the right half thereof is formed as a declivitous plane 26. The border between the horizontal plane 25 and the declivitous plane 26 is continuously connected by a smooth curved plane so that the cam sliding contact surface 20 has a crowned shape in which the central portion is high as a whole. As a result, the cam slide starting point A where the cam 16 comes into contact with the cam sliding contact surface 20 becomes lower than the cam slide terminating point B where the cam 16 leaves the cam sliding contact surface 20.

(22) FIG. 10 shows the cam sliding contact surface 20 having a reverse crowned shape. More specifically, the cam sliding contact surface 20 is formed so that the right half thereof with respect to the center thereof is formed as a declivitous plane 27 and the left half thereof is formed as a horizontal plane 28. The border between the declivitous plane 27 and the horizontal plane 28 is continuously connected by a smooth curved plane so that the cam sliding contact surface 20 has a reverse crowned shape in which the central portion is low as a whole.

(23) In the example in which the cam sliding contact surface 20 has the reverse crowned shape, similarly to in the case of the cam sliding contact surface 20 having the crowned shape, the cam slide starting point becomes lower than the cam slide terminating point B.

(24) In the case where the outer diameter of the valve lifter 15 is equal to 30 mm, it is necessary for the elevation difference to exceed 15 m and it is preferable for the elevation difference to be equal to or larger than 30 m. By calculations, the mean gradient is equal to or larger than 0.05% (=0.015/30100).

(25) Moreover, there are valve lifters with a variable lift mechanism which are different in arrangement relationship between the high lifter having the high cam sliding contact surface and the low lifter having the low cam sliding contact surface.

(26) FIG. 12 shows an example in which a low lifter 30 is disposed inside of an annular high lifter 29 and FIG. 13 shows an example in which arc-like low lifters 32 are disposed on opposite sides of a rectangular high lifter 31. The cam sliding contact surface according to the present invention includes these arrangements of the high lifter and the low lifter shown in FIGS. 12 and 13.

(27) The present invention can be widely applied to a valve lifter with a variable lift mechanism built in an internal combustion engine of, for example, an automobile, industrial vehicle or the like.

(28) The reference numeral 11 designates a cylinder head, the reference numeral 12 designates an intake port, the reference numeral 13 designates an intake valve, the reference numeral 14 designates a valve stem, the reference numeral 15 designates a valve lifter, the reference numeral 16 designates a cam, the reference numeral 18 designates a cylinder bore, the reference numeral 19 designates a coil spring, the reference numeral 20 designates a cam sliding contact surface, the reference symbol A designates a cam slide starting point on the cam sliding contact surface, and the reference symbol B designates a cam slide terminating point on the cam sliding contact surface, respectively.