JP2007032505A - Valve gear for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce and avoid the one-sided contact of a rocking cam, by forming a predetermined chamfered portion only at an angle portion on a non-link connection side opposite to a link connection side, out of angle portions on both axial sides of each of cam lobes. <P>SOLUTION: This valve gear comprises the rocking cam 20 having a cylindrical journal portion 31 rotatably supported on the side of a cylinder head and a pair of cam lobes 32A, 32B for thrusting the valve lifter of an intake(exhaust) valve, and a link mechanism connected only to the cam lobe 32A on the link connection side FA. At the angle portion 35 on the non-link connection side FB out of the angle portions 35, 36 on both axial sides of each of the cam lobes 32A, 32B, a chamfered portion 35 is formed which is recessed greater than the angle portion 36 on the link connection side FA. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a valve operating apparatus for an internal combustion engine, and in particular, a lift operating angle provided with a swing cam capable of changing both a valve lift amount and an operating angle of an intake valve and an exhaust valve (hereinafter referred to as an intake / exhaust valve). The present invention relates to a technique suitable for a change mechanism.

As a valve operating device for an internal combustion engine, Patent Document 1 describes a lift operating angle changing mechanism capable of continuously and continuously changing both the valve lift amount and the operating angle of an intake / exhaust valve. This mechanism links the drive shaft and the swing cam by a link mechanism including a rocker arm so that the swing cam swings in response to the rotation of the drive shaft driven by the crankshaft to open and close the intake / exhaust valve. In addition, both the valve lift amount and the operating angle of the intake / exhaust valve are changed by changing the position of the rocking fulcrum of the rocker arm via the control shaft and the control cam. In the above-described swing cam, a pair of cam lobes are integrally provided on both sides of a cylindrical journal portion rotatably supported on the cylinder head side, and these cam lobes are valve lifters of a pair of intake valves or exhaust valves of each cylinder. Is to be pressed.
JP 2001-164912 A

  The rocking cam is in a so-called cantilevered form in which the link of the link mechanism is connected only to one cam lobe located on the link connection side in the axial direction. For this reason, during actual engine operation, particularly during high lift, the rocking cam falls in a direction inclined with respect to the axis due to input from the link, etc., and the link connecting side of the corners on both sides in the axial direction of the cam lobe is There is a possibility that the corner portion on the non-link connection side on the opposite side locally contacts the upper surface of the valve lifter strongly.

  The present invention has been made in view of such problems. That is, according to the present invention, the drive shaft and the swing cam are linked by a link mechanism so that the swing cam swings in conjunction with the rotation of the drive shaft that is rotationally driven by the crankshaft. A cylindrical journal portion rotatably supported on the cylinder head side and a pair of cam lobes that press the valve lifter of the intake / exhaust valve are located on the link connection side in the axial direction of the pair of cam lobes. In the valve operating apparatus of the internal combustion engine in which the link mechanism is connected only to one cam lobe, among the corners on both sides in the axial direction of each cam lobe, on the corner on the non-link connection side opposite to the link connection side, Compared to the corner portion on the link connection side, a chamfered portion that is greatly recessed with respect to the cam surface formed on the outer periphery of the cam lobe is formed.

  According to the present invention, the predetermined chamfered portion is formed only at the corner portion on the non-link connection side opposite to the link connection side among the corner portions on both sides in the axial direction of each cam lobe. While ensuring the directional dimension, it is possible to reduce / eliminate local contact at the corner portion on the non-link connection side, and to improve the reliability and durability of the cam lobe and the valve lifter contacting the cam lobe.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a lift operating angle changing mechanism capable of continuously changing both the operating angle of an intake valve 12 and the valve lift amount (maximum lift amount) as a valve operating apparatus for an internal combustion engine according to an embodiment of the present invention. 10 is shown in a simplified manner. Since this mechanism 10 is already known as described in Japanese Patent Application Laid-Open No. 2002-54466, etc., only its outline will be described. Each cylinder is provided with a pair of intake valves 12 and a pair of exhaust valves (not shown), and a valve lifter 19 is provided above each intake valve 12. Above these valve lifters 19, a hollow drive shaft 13 having a lubricating oil passage formed therein extends in the cylinder row direction. The drive shaft 13 receives rotational power from the crankshaft and is driven to rotate in conjunction with the crankshaft. On the outer periphery of the drive shaft 13, a swing cam 20 is swingably attached to each cylinder.

  Each rocking cam 20 has a pair of cam lobes 32A and 32B that respectively abut against the upper surfaces of the pair of valve lifters 19 of each cylinder. The intake valve 12 moves up and down, that is, lifts through the valve lifter 19.

  The lift operating angle changing mechanism 10 is provided eccentrically on the outer periphery of the drive shaft 13, an eccentric cam 15 that rotates integrally with the drive shaft 13, and a control shaft that extends substantially parallel to the drive shaft 13 in the cylinder row direction. 16, a control cam 17 that is eccentrically provided on the outer periphery of the control shaft 16 and rotates integrally with the control shaft 16, and a rocker arm that is swingably fitted to the outer peripheral surface forming the cylindrical surface of the control cam 17. 18, a ring-shaped link (first link) 25 that links one end of the rocker arm 18 and the eccentric cam 15, and a rod-shaped link (second link) 26 that links the other end of the rocker arm 18 and the swing cam 20. ,have. One end of the ring-shaped link 25 is fitted on the outer peripheral surface forming the cylindrical surface of the eccentric cam 15 so as to be relatively rotatable, and the other end is connected to one end of the rocker arm 18 by the first connecting pin 21 so as to be relatively rotatable. One end of the rod-shaped link 26 is connected to the other end of the rocker arm 18 via the second connecting pin 28 so as to be relatively rotatable, and the other end is rotated relative to one cam lobe 32A of the swing cam 20 by the third connecting pin 29. Connected as possible. The shaft center of the eccentric cam 15 is eccentric by a predetermined amount with respect to the shaft center of the drive shaft 13, and the shaft center of the control cam 17 is eccentric by a predetermined amount with respect to the shaft center of the control shaft 16. The journal portion 31 and the control shaft 16 of the swing cam 20 are rotatably supported by the cylinder head via a bearing bracket. The control shaft 16 is rotationally driven by a motor 51 as an actuator and is held at a predetermined rotational position. In this embodiment, the worm 52 provided on the output shaft 51 a of the motor 51 has a simple structure in which it directly meshes with a worm wheel 50 that is coaxially fixed to one end of the control shaft 16.

  With such a configuration, when the drive shaft 13 rotates in conjunction with the crankshaft, the ring-shaped link 25 moves substantially in translation through the eccentric cam 15 and the rocker arm 18 swings around the axis of the control cam 17. Then, the swing cam 20 swings through the rod-shaped link 26 to raise and lower the intake valve 12. Further, by changing the rotation angle of the control shaft 16, the position of the shaft center of the control cam 17, which is the swing fulcrum position of the rocker arm 18, changes, and the posture of the swing cam 20 changes. As a result, the operating angle of the intake valve 12 (opening / closing period of the intake valve) and the valve lift amount are continuously maintained while the central phase (opening / closing timing phase) of the operating angle of the intake valve 12 with respect to the drive shaft 13 remains substantially constant. Change.

  In such a lift operating angle changing mechanism 10, since the bearing portion of the eccentric cam 15, the bearing portion of the control cam 17, and the bearing portion of each pin are in surface contact, it is easy to lubricate, durability, In addition to being excellent in reliability, resistance when changing the operating angle is also suppressed to a low level. Further, since the swing cam 20 that drives the intake valve 12 is arranged coaxially with the drive shaft 13, for example, the configuration is such that the drive cam is supported by another support shaft different from the drive shaft 13. And while being excellent in control precision, the apparatus itself becomes a compact thing and vehicle mounting property is good. Furthermore, since the rod-shaped link 26 is disposed so as to be substantially along the engine vertical direction, the amount of overhang to the engine side (left-right direction in FIG. 1) is suppressed. In addition, since it is a simple link mechanism without a biasing means such as a spring in the transmission path from the drive shaft 13 to the swing cam 20, there is little loss and excellent reliability and durability.

  The control unit 54 receives an engine rotation signal, an engine load signal, a cooling water temperature signal, a hydraulic oil temperature signal, and the like, and outputs a control signal to the motor 51 based on these detection signals. In addition to controlling the operating angle and the valve lift amount, it has a function of storing and executing various engine control processes. The angle of the control shaft 16 corresponding to the lift characteristic amount (valve lift amount and operating angle) by the lift operating angle changing mechanism 10 is detected by an operating angle sensor (control axis sensor) 53 such as a potentiometer.

  2 and 3 show the swing cam 20 as a single unit. With reference to FIGS. 1-3, the structure and shape of the rocking cam 20 which makes the principal part of a present Example, and its effect are demonstrated. The swing cam 20 is mounted on the drive shaft 13 so as to be swingable for each cylinder, and constitutes a link mechanism so as to swing in conjunction with the rotation of the drive shaft 13 driven to rotate by the crankshaft. The ring-shaped link 25, the rocker arm 18, and the rod-shaped link 26 are linked to the drive shaft 13. Each swing cam 20 is provided integrally with a cylindrical journal portion 31 that is rotatably supported to the cylinder head 23 using a cam bracket 22 and both axial ends of the journal portion 31. The pair of first cam lobes 32A and the second cam lobes 32B press the valve lifter 19 of the pair of intake valves. Each cam lobe 32A, 32B protrudes radially outward from a cylindrical base portion 33 arranged coaxially with the journal portion 31, and the valve lifter 19 of the intake valve 12 is valved in response to the swing of the swing cam 20. The intake valve 12 is opened and closed by pushing down against the spring reaction force.

  Since the swing cam 20 is provided with the pair of cam lobes 32A and 32B, the swing cam 20, the ring-shaped link 25, the rod-shaped link 26, and the rocker arm 18 with respect to the pair of intake valves 12 of each cylinder. The link parts such as can be shared with each other, and the weight reduction and simplification can be achieved by reducing the number of parts. Since the swing cam 20 is provided with the pair of cam lobes 32A and 32B, one of the pair of cam lobes 32A and 32B is positioned on the predetermined link connection side (upper side in FIG. 3) FA in the axial direction. A link mechanism is connected only to the first cam lobe 32A. Specifically, the pin hole 30 is formed only in the first cam lobe 32A of the pair of cam lobes 32A and 32B, and the third connecting pin 29 inserted through the pin hole 30 constitutes a part of the link mechanism. The link 26 and the swing cam 20 are connected so as to be relatively rotatable.

  As described above, when the link mechanism is connected only to one cam lobe 32A of the swing cam 20, a so-called cantilevered support structure is caused by a load acting from the link mechanism side during actual operation of the engine. 3, the load / moment of the predetermined inclination direction M1 inclined with respect to the axis 20A of the swing cam 20, more specifically, the direction in which the pin hole 30 approaches the axis 20A (clockwise direction in FIG. 3) M1. Act. For this reason, the swing cam 20 falls in the inclination direction M1, and the non-link connection side FB (on the opposite side of the link connection side FA among the corners 35, 36 on both axial sides of the cam lobes 32A, 32B) The lower part of FIG. 3 locally contacts the valve lifter 19 so as to cause a so-called one-side contact, which causes a specific problem that it is difficult to ensure the reliability and durability of the swing cam 20. . In order to reduce the above-described tilting of the swing cam 20, the gap between the outer periphery of the drive shaft 13 and the inner periphery of the swing cam 20, the inner periphery of the journal portion 31 of the swing cam 20, the cam bracket 22 and the cylinder head. If the gap between the bearing portion 23 and the bearing portion 23 is excessively reduced, the sliding resistance and friction at this portion will increase.

  Therefore, in the present embodiment, among the corner portions 35 and 36 on both axial sides of the cam lobes 32A and 32B, the corner portion 35 on the non-link connection side FB (the lower side in FIG. 3) opposite to the link connection side FA. Further, a chamfered portion (35) that is greatly recessed with respect to the cam surface 34 formed on the outer periphery of the cam lobes 32A and 32B is formed as compared with the corner portion 36 of the link connection side FA. By forming the chamfered portion 35 in this way, even if the swing cam 20 falls in the inclined direction M1, which is a problem specific to the swing cam 20 having the cantilever support shape as described above, Since the chamfered portion 35 is formed at the corner portion of the non-link connection side FB (lower side in FIG. 3) of 32A and 32B, the so-called one-side contact that locally and strongly contacts the upper surface of the valve lifter 19 at this portion. It is possible to effectively reduce or avoid the occurrence. As a result, the reliability and durability of the swing cam 20 and the valve lifter 19 can be improved.

  Further, in order to ensure a sufficient dimension in the width direction of the cam surface 24, the corner portion 36 of the link connection side FA is not provided with a chamfered portion that is recessed with respect to the cam surface 34, or the above-mentioned chamfering A chamfered portion in which the amount of depression with respect to the cam surface 34 is sufficiently smaller than that of the portion 35 is formed.

  For example, the chamfered portion 35 is cut into a substantially triangular cross-section by using a cutting blade 37 having a predetermined tapered tip portion 38 as shown in FIG. The chamfered portion 35 is provided only in a partial section 39 on the distal end side corresponding to the high lift section in the circumferential direction. In other words, no chamfered portion is provided in the cam ramp section. Thus, unnecessary cutting can be omitted by providing the chamfered portion 35 only at the high surface pressure portion where the one-piece contact is particularly problematic. Note that the chamfered portion 35 may be formed at the time of casting. In this case, the above-described cutting process can be omitted.

  Among the cam lobes 32A and 32B, in the section 39 on the high lift side where the chamfered portion 35 is formed, the cam surface 34 that contacts the valve lifter 19 is in the width direction range excluding the chamfered portion 35. Therefore, in this embodiment, the cam lobes 32A and 32B are offset to the non-link connection side FB with respect to the center of the valve lifter 19. That is, the center lines 40 of the cam lobes 32A and 32B are offset from the lifter center line 41 passing through the center of the valve lifter 19 and parallel to the center line 40 by a predetermined amount α to the non-link connection side FB. Thereby, compared with the case where both center lines 40 and 41 are arranged at the same axial position, the range of the cam surface 34 that contacts the valve lifter 19 at the time of maximum lift, that is, the range excluding the chamfered portion 35, is the center of the valve lifter 19. Since the cam travel range can be expanded, the valve lift amount can be set large.

  Further, in the base portions of the cam lobes 32A and 32B that do not substantially come into contact with the valve lifter 19, cutting portions 42 are formed on both sides thereof by cutting or the like for lightening.

  The swing cam 20 is typically fitted to the outer periphery of the drive shaft 13 so as to be swingable as in the above embodiment. In this case, since it is necessary to secure a clearance so that excessive friction does not act between the outer periphery of the drive shaft 13 and the inner periphery of the swing cam 20, the swing cam 20 is allowed to fall. Since it is easy to invite, it is very useful to provide the chamfered portion 35 as described above.

  The swing cam 20 is preferably applied to the lift operating angle changing mechanism 10 that can continuously change both the valve lift amount and the operating angle of the intake valve 12 (or the exhaust valve) as in the above embodiment. The lift operating angle changing mechanism 10 includes a circular drive cam 15 provided eccentrically on the drive shaft 13, a control shaft 16, a circular control cam 17 provided eccentrically on the control shaft 16, and suction (discharge). And an actuator (motor) 51 that changes the rotation angle of the control shaft 16 so as to change the valve lift amount and the operating angle of the air valve 12. The link mechanism includes a rocker arm 18 that is swingably attached to the circular outer periphery of the control cam 16, a first link (ring-shaped link) 25 that links the eccentric cam 15 and one end of the rocker arm 18. A second link (rod-shaped link) 26 that links the other end of the rocker arm 18 and one cam lobe 32 </ b> A of the swing cam 20 is provided.

  As described above, the present invention has been described based on the specific embodiments. However, the present invention is not limited to the above-described embodiments, and includes various modifications and changes without departing from the spirit of the present invention. . For example, in the above embodiment, the valve gear according to the present invention is applied to the intake valve side, but it can also be applied to the exhaust valve side.

The perspective view which shows simply the lift operating angle change mechanism which is an example of the valve gear of this invention. Sectional drawing which shows the rocking | fluctuation cam of the said lift operating angle change mechanism. The plane corresponding | compatible figure which similarly shows the said rocking cam. Explanatory drawing which shows the chamfering part of the said rocking cam, and the cutting tool for the cutting process.

Explanation of symbols

10 ... Lift operating angle changing mechanism (valve operated device)
DESCRIPTION OF SYMBOLS 12 ... Intake valve 13 ... Drive shaft 15 ... Eccentric cam 16 ... Control shaft 17 ... Control cam 18 ... Rocker arm 20 ... Swing cam 25 ... Link-like link (1st link)
26 ... Rod-shaped link (second link)
31 ... Journal part 32A, 32B ... Cam lobe 34 ... Cam surface 35 ... Chamfered part (corner part)
36 ... Corner

Claims (5)

The drive shaft and the swing cam are linked by a link mechanism so that the swing cam swings in conjunction with the rotation of the drive shaft driven to rotate by the crankshaft.
The swing cam has a cylindrical journal portion rotatably supported on the cylinder head side, and a pair of cam lobes that press the valve lifter of the intake / exhaust valve. Of these pair of cam lobes, In the valve operating apparatus for an internal combustion engine in which the link mechanism is connected only to one cam lobe located on the link connection side,
The cam surface formed on the outer periphery of the cam lobe at the corner on the non-link connection side opposite to the link connection side of the corners on both sides in the axial direction of each cam lobe compared to the corner on the link connection side A valve operating apparatus for an internal combustion engine, characterized in that a chamfered portion that is greatly recessed is formed.   2. The valve operating apparatus for an internal combustion engine according to claim 1, wherein the chamfered portion is provided only at a portion corresponding to the high lift section in the circumferential direction.   3. The valve operating apparatus for an internal combustion engine according to claim 1, wherein each cam lobe is offset to the non-link connection side with respect to the center of the valve lifter.   The valve operating apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein the swing cam is swingably fitted to the outer periphery of the drive shaft. A circular drive cam provided eccentric to the drive shaft, a control shaft, a circular control cam provided eccentric to the control shaft, and the valve lift amount and operating angle of the intake / exhaust valve are changed. An actuator for changing the rotation angle of the control shaft,
A rocker arm that is swingably attached to the circular outer periphery of the control cam; a first link that links the eccentric cam and one end of the rocker arm; the other end of the rocker arm; and one cam lobe of the rocking cam; 5. The valve operating apparatus for an internal combustion engine according to claim 1, further comprising a second link that links the two.

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