JP2004263608A - Valve train for internal combustion engine - Google Patents

Abstract

Kind Code: A1 An internal combustion engine having a variable valve operating mechanism that can suppress generation of abnormal noise due to switching of operating characteristics of an intake valve and an exhaust valve, and reduce damage and wear of the variable valve operating mechanism. Provide equipment.
A first rocker arm (32) has one of a cylinder (50) having an opening (53) in a part of a sliding surface and a cylinder whose side is not closed by an elastic member (52). A piston (51) urged toward the sliding end of the cylinder, and the second rocker arm (135) is provided with a piston at one sliding end of the cylinder by the swing of the first rocker arm. When the tip (135c) is inserted into the cylinder through the opening and the side surface of the piston is in a position to close the opening, the tip (135c) is brought into contact with the contact projection (135a) contacting the side surface. In addition, an inclined surface (135e) is formed at the tip of the contact protrusion at a corner on one sliding end side of the cylinder.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a valve train for an internal combustion engine, and more particularly, to a variable valve train for an internal combustion engine that can change the operating characteristics of an intake valve and an exhaust valve according to the operating state of the engine.
[0002]
[Related background art]
In recent years, it has become possible to optimize the operating characteristics (opening / closing timing and opening period) of poppet-type intake and exhaust valves provided in internal combustion engines (hereinafter referred to as engines) according to the load state and rotational speed state of the engine. A valve gear having a variable valve operating mechanism has been developed and put into practical use.
[0003]
For example, a low-speed cam having a cam profile suitable for low-speed rotation of the engine and a high-speed cam having a cam profile suitable for high-speed rotation of the engine. A valve train that can be selected according to the rotational speed state has been developed (for example, see Patent Document 1).
Further, the applicant has proposed a valve train shown in FIGS. 5 and 6 for an SOHC type engine (for example, see Patent Document 2).
[0004]
FIG. 6 is a cross-sectional view taken along the line AA of FIG. 5. In the valve gear, as shown in FIGS. 5 and 6, a cylinder head 10 above each cylinder of the engine is provided for each cylinder. Two intake valves 11, 12 and two exhaust valves 21, 22 which are normally closed by return springs (not shown) are provided, and these intake valves 11, 12 and exhaust valves 21, 22 are driven. For this purpose, a valve train 30 is provided.
[0005]
The valve train 30 is divided into an intake valve drive system that drives the intake valves 11 and 12 and an exhaust valve drive system that drives the exhaust valves 21 and 22. The intake valve drive system is pivotally supported by the camshaft 31, cams 31a to 31c fixed to the camshaft 31, a rocker shaft 32, and the rocker shaft 32, and swings by the cams 31a to 31c. Rocker arms 33 to 35 are provided. On the other hand, the exhaust valve drive system includes a camshaft 31 shared with the intake system, cams 31 d and 31 e fixed to the camshaft 31, a rocker shaft 36, and a cam that is swingably supported by the rocker shaft 36. Rocker arms 37 and 38 that swing by 31d and 31e are provided.
[0006]
In addition, a variable valve mechanism 40 having a connection switching mechanism 41 is provided in a portion of the valve operating device 30 corresponding to the intake valve drive system. Hereinafter, the configuration of the variable valve mechanism 40 will be described in detail.
Among the rocker arms 33 to 35 for driving the intake valves, the rocker arms 33 and 34 have the adjusting screws 33 a and 34 a at one end in contact with the stem ends of the intake valves 11 and 12, and the intake valve 11 swings the rocker arm 33. , And the intake valve 12 is configured to open and close according to the swing of the rocker arm 34.
[0007]
Specifically, the rocker arm 33 has the roller 33b at the other end in contact with the low-speed cam 31a formed with the low-speed cam profile corresponding to the low-speed rotation of the engine, and swings following the low-speed cam 31a. The intake valve 11 is configured to be opened with a characteristic shown by a dashed line in FIG. Further, the rocker arm 34 is in contact with the low-speed cam 31b on which the low-speed cam profile corresponding to the low-speed rotation of the engine is formed by the roller 34b at the other end, and swings by following the low-speed cam 31b. The intake valve 12 is also configured to be opened with the characteristic shown by the solid line in FIG.
[0008]
On the other hand, the rocker arm 35 has a pair of contact protrusions 35a, 35a formed at one end thereof extending toward the rocker arms 33, 34, and a roller 35b provided at the other end is provided with a high-speed cam corresponding to a high-speed rotation of the engine. It is in contact with the high-speed cam 31c on which the profile is formed. That is, the rocker arm 35 swings following the high-speed cam 31c, so that the tip surfaces 35d, 35d of the tip portions 35c, 35c of the contact protrusions 35a, 35a can contact the rocker arms 33, 34.
[0009]
The rocker arm 35 is urged by an arm spring 43 so that the rocker arm 35 does not separate from the cam 31c. More specifically, as shown in FIG. 5, the arm spring 43 includes a spring body 43a and a casing 43b containing the spring body 43a, and the rocker arm 35 is pressed by the urging force of the spring body 43a via the casing 43b. As a result, the roller 35b is in contact with the cam 31c. The arm spring 43 is supported by a tip 44 a of a holder 44 attached around the rocker shaft 36, while a rear end 44 b of the holder 44 is in contact with an upper end of a rib 45 erected on the cylinder head 10. . As a result, the rotation of the holder 44 around the rocker shaft 36 is suppressed, and the urging force of the spring body 43a is transmitted to the rocker arm 35 satisfactorily.
[0010]
Cylinders 50, 50 are formed at positions where the distal end surface 35d of the contact protrusion 35a contacts the rocker arms 33, 34, respectively. Inside the cylinder 50, the cylinder 50 is slidable on the sliding surface of the cylinder 50. A piston 51 is provided.
Specifically, at the position where the tip end surface 35d of the contact projection 35a contacts the rocker arms 33 and 34 in the cylinder 50, a part of the sliding surface is opened to form openings 53, respectively. The projection 35a can be inserted into the cylinder 50 from the opening 53.
[0011]
A spring 52 is provided in the cylinder 50 to bias the piston 51 toward one of the sliding ends of the cylinder 50 so that the side surface 51a of the piston 51 does not block the opening 53. Pressure oil (hydraulic oil, also used as lubricating oil, hereafter referred to as lubricating oil) is supplied through the passages 32a, 32b. Therefore, when the oil pressure in the cylinder 50 is increased, the piston 51 receives the oil pressure at one end and closes the opening 53 against the urging force of the spring 52 as shown in FIG. The inside of the cylinder 50 is slid toward the other sliding end of the cylinder 50. On the other hand, when the hydraulic pressure in the cylinder 50 is weakened, the piston 51 is moved by the urging force of the spring 52 so that the side surface 51a of the piston 51 does not close the opening 53 as shown in FIG. It is returned to the position on one sliding end side.
[0012]
Specifically, a hydraulic pressure adjustment device 42 that adjusts the oil pressure of the lubricating oil supplied into the cylinder 50 is provided upstream of the oil passage 32a, and the oil pressure adjustment device 42 operates in an operating state of the engine, for example, the engine load Le. When the hydraulic pressure is increased by switching according to the engine rotation speed Ne, the piston 51 slides toward the other sliding end side of the cylinder 50 to close the opening 53, and the hydraulic adjustment device 42 switches the operation state of the engine to the operating state. When the pressure is switched accordingly and the hydraulic pressure is weakened, the piston 51 is returned to the one sliding end side of the cylinder 50 by the urging force of the spring 52.
[0013]
As shown in FIG. 8, the hydraulic pressure adjustment device 42 supplies a lubricating oil pumped up to the cylinder block 10 from an oil pan (not shown) at the lower part of the engine to an oil passage 32 a in the rocker shaft 32. , 42b and a branch oil passage 42c extending from the common oil passage 42b for each cylinder, an oil control valve 42d interposed in the branch oil passage 42c, a filter 42e, and a controller for controlling the opening of the oil control valve 42d. (Not shown).
[0014]
Thus, for example, when a command corresponding to the engine load Le and the engine rotation speed Ne is supplied from the controller, the opening of the oil control valve 42d is set to the opening corresponding to the command, and the lubrication supplied to the cylinder 50 is controlled. The oil pressure of the oil is adjusted, and the piston 51 slides in the cylinder 50. Specifically, for example, when the engine load Le and the engine rotation speed Ne each become equal to or higher than a predetermined value and the high-speed cam 31c is selected, the oil pressure of the lubricating oil supplied into the cylinder 50 is increased, and the piston 51 The side surface 51 a slides so as to close the opening 53. On the other hand, when the engine load Le and the engine rotation speed Ne become lower than the predetermined values, respectively, and the low speed cams 31a and 31b are selected, the oil pressure of the lubricating oil supplied into the cylinder 50 is reduced, and the side surface 51a of the piston 51 is reduced. Is returned so as not to block the opening 53.
[0015]
A connection switching mechanism 41 for switching the connection state between the rocker arms 33 and 34 and the rocker arm 35 is constituted by the piston 51 in the cylinder 50 and the hydraulic pressure adjusting device 42.
In the variable valve mechanism 40 configured as described above, a small-diameter passage for supplying lubricating oil of the oil control valve 42d communicates with the selection of the low-speed cam as shown in FIG. When the hydraulic pressure in the cylinder 50 is reduced, the piston 51 is buried in the cylinder 50 by the urging force of the spring 52 so that the side surface 51 a does not block the opening 53, and is located on one of the sliding ends of the cylinder 50. A space 50a is formed from the portion 53 into the cylinder 50 (see FIG. 7A). When the space 50a is formed from the opening 53 toward the inside of the cylinder 50 as described above, when the rocker arm 35 swings, as shown by a two-dot chain line in FIG. The distal end 35c of the projection 35a does not come into contact with the rocker arms 33 and 34 at all, and comes into and out of the space 50a. In this case, the rocker arms 33 and 34 follow the corresponding low speed cams 31a and 31b, respectively. To open and close the intake valves 11 and 12. That is, the intake valves 11 and 12 open and close with valve lifts as shown by the solid line and the one-dot chain line in FIG.
[0016]
On the other hand, when the high-speed cam is selected, a large-diameter passage (not shown) for supplying the lubricating oil is communicated with the oil control valve 42d, and the hydraulic pressure in the cylinder 50 is increased by the hydraulic pressure adjusting device 42. The side surface 51a operates to close the opening 53 and close the opening 53 against the urging force of the opening 52 (see FIG. 7B). When the piston 51 operates to close the opening 53 in this manner, the tip surface 35d of the contact projection 35a of the rocker arm 35 comes into contact with the side surface 51a of the piston 51 when the rocker arm 35 swings. In this case, the rollers 33b and 34b of the rocker arms 33 and 34 are separated from the corresponding low speed cams 31a and 31b, and the rocker arms 33 and 34 follow the high speed cam 31c via the rocker arm 35 and are integrated with the rocker arm 35. It swings to open and close both intake valves 11 and 12. That is, the intake valves 11, 12 open and close simultaneously with a valve lift as shown by the solid line in FIG. 9B.
[0017]
[Patent Document 1]
JP-A-63-170513
[Patent Document 2]
Description and drawings attached to Japanese Patent Application No. 2002-151363
[0018]
[Problems to be solved by the invention]
By the way, in the variable valve mechanism 40, the piston 51 is operated by hydraulic pressure using lubricating oil. However, when switching to the high-speed cam, the hydraulic pressure of the lubricating oil to be pumped up is not sufficiently ensured. In some cases, the piston 51 does not operate sufficiently and the side face 51a of the piston 51 does not completely cover the opening 53, and the opening 53 may be partially closed.
[0019]
When the opening 53 is closed in a state where the piston 51 is halfway in this way, only the portion on the one sliding end side of the cylinder 50 on the tip surface 35d of the contact protrusion 35a of the rocker arm 35 is at the end of the piston 51. At this time, since the pressing force of the contact protrusion 35a is higher than the hydraulic pressure, the piston 51 is pushed by the contact protrusion 35a after the contact protrusion 35a pushes the end of the piston 51 to a certain extent, 50 may be returned to one of the sliding ends. When the piston 51 is pushed back to a certain extent when it is pushed to a certain extent, the tip portion 35c of the contact projection 35a is disengaged from the piston 51 and is inserted into the space 50a from the opening 53 at a stretch, and the rocker arms 33, 34 that have been separated from each other. The rollers 33b and 34b suddenly come into contact with the low speed cams 31a and 31b by the urging force of the return springs of the intake valves 11 and 12. Further, the valve faces of the intake valves 11 and 12 may suddenly come into contact with the valve seats.
[0020]
When the rollers 33b, 34b of the rocker arms 33, 34 and the low speed cams 31a, 31b suddenly come into contact with each other or the valve faces of the intake valves 11, 12 and the valve seats suddenly come into contact with each other, an impact sound is generated. This is not preferable because it causes (abnormal noise) and causes damage and wear to each part of the valve mechanism.
In particular, in the variable valve mechanism 40 of the multi-cylinder engine, as described above, the lubricating oil is supplied to the cylinders 50, 50 of the rocker arms 33, 34 in each cylinder via the common oil passages 42a, 42b. When the piston 51 is repelled back in one of the rocker arms 33 and 34, the hydraulic pressure greatly fluctuates and pulsation occurs in the common oil passages 42a and 42b, and the hydraulic pressure supplied to the cylinder 50 of the other cylinder temporarily drops. Thus, the opening 53 is easily closed when the piston 51 is in a halfway state, so that a loud impact sound is liable to be concentrated in a chain and the above problem is remarkable.
[0021]
SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to provide an internal combustion engine having a variable valve operating mechanism, which generates abnormal noise caused by switching of operating characteristics of an intake valve and an exhaust valve. It is an object of the present invention to provide a valve operating device for an internal combustion engine that can suppress the occurrence of vibration and reduce damage and wear of a variable valve operating mechanism.
[0022]
[Means for Solving the Problems]
In order to achieve the above object, in the valve gear of the internal combustion engine according to the first aspect, one of the intake valve and the exhaust valve is opened and closed by swinging in accordance with the first cam that rotates with the rotation of the camshaft. A first rocker arm to be actuated; a second rocker arm having a shape different from that of the first cam and swinging in accordance with a second cam that rotates with the rotation of the camshaft; and the first rocker arm; A cylinder formed on one of the second rocker arms and having an opening in a part of the sliding surface, slidably mounted in the cylinder along the sliding surface, and slid by an elastic member; A piston biased toward one sliding end of the cylinder whose side does not block the opening, and a side of the piston blocks the opening in the cylinder against the biasing force of the elastic member. The series Piston operating means for operating the piston toward the other sliding end of the damper; and a first rocker arm and a second rocker arm projecting from one of the first rocker arm and the second rocker arm. When the piston is at the one sliding end of the cylinder, the tip is inserted into the cylinder through the opening while the piston is moved by the operation of the piston operating means. When the side surface is at a position for closing the opening, the distal end portion has a contact projection that comes into contact with the side surface, and the distal end portion of the contact projection has a corner on one sliding end side of the cylinder. It is characterized in that an inclined surface is formed at a position.
[0023]
In other words, the valve train of the internal combustion engine has a variable valve train. Normally, when the first and second rocker arms swing following the first and second cams, respectively, the first and second rocker arms swing. When the piston in the cylinder provided on one of the rocker arms is at one of the sliding ends of the cylinder, the tip of the contact projection is inserted into the cylinder from the opening of the cylinder, and the intake valve or the exhaust valve is placed in the first position. When the piston is actuated by the piston actuating means and the side surface of the piston closes the opening of the cylinder, the tip portion contacts the side surface, and The rocker arm pushes the first rocker arm away from the first cam, and the intake valve or the exhaust valve operates following the second cam via the second rocker arm and the first rocker arm.
[0024]
However, at this time, if the piston is not sufficiently operated even by the piston operating means and the opening of the cylinder is closed in an incomplete state, the tip of the contact projection is located on the one sliding end side of the cylinder. Only the portion is hooked on the end of the piston, and after the contact projection presses the end of the piston to a certain extent, the piston is repelled by the contact projection and returned to the one sliding end side of the cylinder, and the first cam The first rocker arm separated from the first cam may suddenly contact the first cam, or the valve face of the intake valve or the exhaust valve may suddenly contact the valve seat to generate an impact sound.
[0025]
However, at the tip of the contact projection according to the present invention, an inclined surface is formed at a corner on one sliding end side of the cylinder, so that the piston can be sufficiently operated by the piston operating means. In the case where the opening of the cylinder is closed halfway without being inserted, the piston is forcibly pushed back by the inclined surface from the time when the tip of the contact projection is engaged with the piston, and the tip of the contact projection is opened. The first rocker arm is no longer separated from the first cam by being properly inserted into the space formed from the portion into the cylinder, so that the first rocker arm and the first cam can be rapidly abutted. The sudden contact between the valve face of the intake valve or the exhaust valve and the valve seat is eliminated, and the generation of the impact noise is suppressed. Further, damage and wear of the variable valve mechanism are reduced.
[0026]
Further, in the valve operating device for an internal combustion engine according to claim 2, the piston operating means operates the piston by hydraulic oil supplied from a hydraulic source via an oil passage, and a hydraulic adjusting means is provided in the oil passage. Wherein the hydraulic pressure is increased by the hydraulic pressure adjusting means in accordance with the operation state of the internal combustion engine, and the piston is operated against the urging force of the elastic member.
[0027]
That is, the piston operates by increasing the oil pressure of the hydraulic oil supplied from the oil pressure source by the oil pressure adjusting means in accordance with the operation state of the internal combustion engine. The cylinder opening is closed in an incomplete state without operation, but even in such a case, since the pressing force of the contact projection is higher than the hydraulic pressure, the piston is It is forcibly and reliably pushed back by the inclined surface formed on the distal end surface of the portion, the generation of the impact noise is suppressed, and the damage and wear of the variable valve mechanism are also reduced.
[0028]
According to a third aspect of the present invention, in the second aspect of the invention, the internal combustion engine is a multi-cylinder internal combustion engine, and the hydraulic adjustment means is provided together with the first rocker arm and the second rocker arm by a cylinder. The oil pressure adjusting means is provided in each of oil paths branched from a common oil path extending from a hydraulic pressure source.
[0029]
That is, since the hydraulic oil is supplied from the hydraulic pressure source to the cylinder provided in one of the first and second rocker arms of each cylinder via the common oil passage, the hydraulic oil is supplied to the first and second rocker arms of one cylinder. In either case, if the piston is returned by the contact projection, the hydraulic pressure will fluctuate greatly and pulsation will occur in the common oil passage, the hydraulic pressure supplied to the cylinders of the other cylinders will temporarily drop, and the piston will be halfway It is easy to close the opening, so that abrupt contact between the first rocker arm and the first cam and sudden contact between the valve face of the intake valve or the exhaust valve and the valve seat occur in a chain, and the concentration is concentrated. Although a loud impact sound is likely to be generated, the piston is forcibly pushed back by the inclined surface formed at the tip of the contact projection, thereby suppressing the generation of such a loud impact sound and enabling a variable movement. Of valve mechanism Scratches, also wear is reduced.
[0030]
Further, in the valve gear of the internal combustion engine according to claim 4, the inclination angle of the inclined surface is set within a predetermined angle range having a central value of 35 ° with respect to the distal end surface of the distal end portion. I have.
When the inclination angle of the inclined surface is set within a predetermined angle range having a median value of 35 ° with respect to the distal end surface, the piston is always stably and reliably pushed back by the inclined surface. The generation of the impact noise is accurately suppressed, and the damage to the variable valve mechanism is favorably reduced.
[0031]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
The valve gear according to the present invention is an improvement of the valve gear shown in FIGS. 5 to 9. The basic structure is the same as that described above, and a description thereof will be omitted. The part according to the present invention will be described in detail with reference to FIG.
[0032]
Referring to FIGS. 1 (a) and 1 (b), corresponding to FIG. 7, there is shown a diagram showing a characteristic portion of the valve train of the SOHC type engine according to the present invention, and see FIG. 1 (c). Then, a cross-sectional view along the line BB of FIG. 1 (b) is shown, and the characteristic configuration of the valve gear according to the present invention will be described below with reference to FIG. In FIG. 1, the same parts as those in FIG.
[0033]
Here, for example, a multi-cylinder SOHC engine having four cylinders is employed.
In the variable valve mechanism 140 according to the present invention, a pair of contact projections 135a, 135a extend from the rocker arm (second rocker arm) 135 toward the rocker arms (first rocker arm) 33, 34, respectively. The tip surfaces 135d, 135d of the tip portions 135c, 135c of the projections 135a, 135a are configured to be able to abut on the rocker arms 33, 34.
[0034]
As shown in the figure, cylinders 50 and 50 are formed as connection switching mechanisms 41 at positions where the distal end surface 135d of the contact protrusion 135a contacts the rocker arms 33 and 34, respectively. A cylindrical piston 51 is slidably provided on the sliding surface of the cylinder 50. In the cylinder 50, at the position where the distal end surface 135d of the contact protrusion 135a contacts the rocker arms 33 and 34, a part of the sliding surface is opened to form an opening 53, respectively. 135a is configured to be insertable into the cylinder 50 through the opening 53.
[0035]
In the cylinder 50, a spring (elastic member) 52 for biasing the piston 51 toward one sliding end side of the cylinder 50 in which the side surface 51a of the piston 51 does not block the opening 53 is eccentrically provided. Lubricating oil (hydraulic oil) via a hydraulic pressure adjusting device (piston operating means) 42, that is, an oil control valve (oil pressure adjusting means) 42d interposed in the common oil passages 42a and 42b, the branch oil passage 42c, and the branch oil passage 42c. Is supplied from the rocker shaft 32 through oil passages 32a and 32b.
[0036]
In the variable valve mechanism 140 configured as described above, when the oil pressure in the cylinder 50 is increased by switching the oil control valve 42d by selecting the high-speed cam, as shown in FIG. Then, it receives the oil pressure at one end and slides in the cylinder 50 toward the other sliding end of the cylinder 50 so as to close the opening 53 against the urging force of the spring 52. Thus, when the rocker arm 135 swings, the distal end surface 135d of the contact protrusion 135a of the rocker arm 135 comes into contact with the side surface 51a of the piston 51, and the rocker arm 135 and the rocker arms 33 and 34 are connected to the high-speed cam (the second cam). 3) The intake valves 11 and 12 are opened / closed by swinging integrally following 31c.
[0037]
At this time, as shown in FIG. 1 (c), the distal end surface 135d of the contact protrusion 135a has an arc surface slightly larger in diameter than the side surface 51a of the cylindrical piston 51. Line contact can be reliably made with the side surface 51a.
On the other hand, when the oil pressure in the cylinder 50 is reduced by switching the oil control valve 42d by selecting the low speed cam, the piston 51 is biased by the biasing force of the spring 52, as shown in FIG. The side surface 51a is returned to the position on the one sliding end side of the cylinder 50 so as not to block the opening 53, and a space 50a is formed from the opening 53 into the cylinder 50. As a result, as shown by the two-dot chain line in FIG. 1A, the tip 135c of the rocker arm 135 does not come into contact with the rocker arms 33, 34 and protrudes into the space 50a, and the rocker arms 33, 34 correspond to each other. The intake valves 11 and 12 are opened and closed by swinging following the low-speed cams (first cams) 31a and 31b.
[0038]
The arrangement position (eccentric position) of the spring 52, the arrangement method thereof, and the shape of the piston 51 associated therewith may be appropriately set so that the spring 52 or the piston 51 does not interfere with the tip 135c of the rocker arm 135. .
By the way, an inclined surface 135e is formed at a corner portion of the cylinder 50 on one sliding end side while sufficiently securing the leading end surface 135d at the leading end portion 135c of the contact projection 135a.
[0039]
Referring to FIG. 2, there is shown a detailed view of the tip 135c of the contact projection 135a. As shown in FIG. 2, the slope 135e has a tilt angle set within a predetermined angle range with respect to the tip 135d. Have been. Here, as will be described in detail later, the inclination angle is set within a predetermined angle range having a central value of 35 ° (FIG. 2 shows a case where the optimum value is 35 °). Note that the dimension d of the inclined surface 135e in the distal end surface 135d may be arbitrarily set based on experiments and the like (here, for example, the ratio d / D to the dimension D of the distal end surface 135d is set to 0.2, It is not limited to this).
[0040]
Hereinafter, the operation of the thus-configured valve gear according to the present invention will be described. In the variable valve mechanism 140, as described above, when switching to the high-speed cam, the hydraulic pressure of the lubricating oil to be pumped up is not sufficiently secured (insufficient hydraulic pressure), and the piston 51 does not operate sufficiently. There is a case where the side surface 51a of the piston 51 does not completely close the opening 53, and the opening 53 is partially closed. That is, as shown in FIG. 3, there is a case where the opening 53 is closed in a state where the piston 51 is halfway.
[0041]
However, an inclined surface 135e is formed on the distal end surface 135d of the contact protrusion 135a. When the piston 51 closes the opening 53 in a halfway state as shown in FIG. 3, the contact protrusion 135a is formed. When swinging, the piston 51 first comes into contact with the inclined surface 135e. Then, the piston 51 is forced by the component force of the inclined surface 135e in the sliding direction of the piston 51 as shown by a thick white arrow in FIG. 3 from the time when the tip end 135c of the contact projection 135a is applied to the piston 51. As a result, the piston 51 is pushed back to the position on the one sliding end side of the cylinder 50, that is, the piston 51 is flipped at an early stage, and the tip 135c of the contact protrusion 135a is moved as shown by the solid arrow in FIG. Then, the piston 51 is satisfactorily inserted into the space 50a from the opening 53 while pushing back the piston 51 (see FIG. 1A).
[0042]
When the piston 51 is forcibly pushed back in this way and the tip 135c of the contact projection 135a is properly inserted into the space 50a, the rollers 33b and 34b of the rocker arms 33 and 34 are separated from the low-speed cams 31a and 31b. In other words, the rocker arms 33 and 34 are continuously operated by following the low speed cams 31a and 31b.
[0043]
That is, if there is no inclined surface 135e, there is a high possibility that the piston 51 will be flipped back by the contact protrusion 135a after the contact protrusion 135a has pushed the end of the piston 51 to some extent. In this case, the rocker arms 33 and 34 The rollers 33b, 34b and the low-speed cams 31a, 31b once come into contact with each other and then suddenly come into contact with each other, or the valve faces of the intake valves 11, 12 come into rapid contact with the valve seats by the urging force of the return springs to generate an impact sound. However, since the inclined surface 135e is formed at the tip 135c of the contact projection 135a, the piston 51 is forcibly returned by the inclined surface 135e, and the generation of such an impact noise is suppressed. .
[0044]
In particular, in the variable valve mechanism 40 of the multi-cylinder SOHC engine, the lubricating oil is supplied to the cylinders 50, 50 of the rocker arms 33, 34 in the respective cylinders via the common oil passages 42a, 42b. When the piston 51 is repelled in any of the positions 33 and 34, the oil pressure greatly fluctuates and pulsation occurs in the common oil passages 42a and 42b, and the oil pressure supplied to the cylinder 50 of another cylinder temporarily decreases. It is easy to close the opening 53 in a state where the piston 51 is halfway, and it is easy to generate a loud impact noise by concentrating in a chain. However, the rocker arms 135 of all the cylinders have the tip 135c of the contact projection 135a. By forming an inclined surface 135e on the front side and forcibly pushing back the piston 51, the generation of such a loud impact sound is suitably suppressed. That.
[0045]
Further, abrupt contact between the rollers 33b, 34b of the rocker arms 33, 34 and the low speed cams 31a, 31b is suppressed, and abrupt contact between the valve faces of the intake valves 11, 12 and the valve seats is suppressed. Then, a large impact force is not applied to the variable valve mechanism 40, and damage and wear of each part of the variable valve mechanism 40 can be reduced.
[0046]
By the way, referring to FIG. 4, an inclined surface 135 e is formed at the tip 135 c of the contact protrusion 135 a by changing the inclination angle to 0 °, 15 °, 25 °, 35 °, 45 °, 55 °, The test results of the frequency of impact sound generation when the connection switching mechanism 41 is switched 10,000 times are shown in the graph. According to the figure, the most impulsive sound is obtained when the inclination angle of the inclined surface 135e is 35 °. It can be seen that the frequency of occurrence is low.
[0047]
Accordingly, it is optimal that the inclination angle of the inclined surface 135e is 35 °. However, according to the figure, when the frequency of occurrence of the impact sound is to be suppressed to about 1% or less, the optimum value is within a predetermined angle range (for example, 35 ° ± 2 °) having a central value of 35 °. It is sufficient that the inclination angle is set in. When the frequency of occurrence of the impact sound is to be suppressed to approximately 2% or less, it is sufficient that the inclination angle is set in the range of 30 ° to 55 °.
[0048]
In the drawing, the impact sound generation frequency is slightly higher when the inclination angle is 15 ° than when the inclination angle is 0 °. This is because when the inclination angle is small, the inclination direction of the inclined surface 135e in the sliding direction of the piston 51 is small. Although the component force is small and the piston 51 cannot be pushed back immediately, if there is a slight inclination angle compared to the case where there is no inclination angle, a certain amount of slippage occurs when the contact projection 135a pushes the piston 51 to some extent. This is because the piston 51 is flipped back.
[0049]
The description of the embodiment of the valve train for an internal combustion engine according to the present invention is completed above, but the embodiment is not limited to the above embodiment, and a cylinder and a piston are provided on one rocker arm, and the other is provided on the other rocker arm. The present invention can be favorably applied to any variable valve mechanism of a type in which a contact protrusion is provided, and the operating characteristics of the intake valve and the exhaust valve are switched by bringing the piston and the contact protrusion into contact or non-contact.
[0050]
For example, in the above-described embodiment, the variable valve mechanism 40 that switches the operation characteristics of the intake valves 11 and 12 is shown. However, the variable valve mechanism 40 that switches the operation characteristics of the exhaust valves 21 and 22 may be used. The operating characteristics of both the exhaust valves 21 and 22 may be switched. Further, the number of intake valves and exhaust valves for switching the operation characteristics and the rocker arms corresponding thereto may be three or more, or may be one.
[0051]
Further, in the above-described embodiment, the variable valve mechanism 40 in which the rocker arms 33 and 34 are provided with the cylinder 50 and the piston 51 and the rocker arm 135 is provided with the abutment projection 135a. A variable valve mechanism including the cylinder and the piston on the rocker arm 135 while providing the contact protrusion may be used.
[0052]
【The invention's effect】
As described above in detail, according to the valve gear of the internal combustion engine of the first aspect of the present invention, in the valve gear having the variable valve mechanism, the first and second rocker arms are usually provided with the first and second rocker arms, respectively. When the piston swings following the first and second cams, when the piston in the cylinder provided on one of the first and second rocker arms is at one of the sliding ends of the cylinder, the tip of the contact projection is moved to the cylinder. The intake valve or the exhaust valve is inserted through the opening into the interior of the cylinder, and the intake valve or the exhaust valve operates following the first cam via the first rocker arm. When the opening is closed, the tip abuts on the side surface, the second rocker arm pushes the first rocker arm away from the first cam, and the intake valve or the exhaust valve is connected to the second rocker arm and the second rocker arm. It operates according to the second cam via the first rocker arm. However, since the tip of the contact projection is formed at the corner on the one sliding end side of the cylinder, an inclined surface is formed. In the case where the piston is not sufficiently operated by the piston operating means and the opening of the cylinder is closed in an incomplete state, the piston is forcibly moved by the inclined surface from the time when the tip of the contact projection is engaged with the piston. The distal end of the contact projection can be satisfactorily inserted into the space formed from the opening toward the inside of the cylinder while being pushed back. As a result, the first rocker arm is not separated from the first cam, so that the piston is not flipped back by the contact protrusion after the contact protrusion has pressed the end of the piston to some extent. It is possible to prevent the sudden contact with the first cam and the sudden contact between the valve face of the intake valve or the exhaust valve and the valve seat, thereby suppressing the generation of the impact noise. Further, damage and wear of the variable valve mechanism can be reduced.
[0053]
According to the second aspect of the invention, the piston is operated by increasing the hydraulic pressure of the hydraulic oil supplied from the hydraulic pressure source by the hydraulic pressure adjusting means in accordance with the operating state of the internal combustion engine. Even if the hydraulic pressure is low by the means, the piston does not operate sufficiently and the opening of the cylinder is closed in an incomplete state, but even in such a case, the pressing force of the contact projection is still Since the pressure is higher than the oil pressure, the piston can be forcibly and reliably pushed back by the inclined surface formed at the distal end surface of the distal end portion of the contact projection, whereby the occurrence of the above-described impact sound can be suppressed, and the variable valve actuation can be achieved. Damage and wear of the mechanism can also be reduced.
[0054]
According to a third aspect of the present invention, in the second aspect of the invention, the internal combustion engine is a multi-cylinder internal combustion engine, and hydraulic oil is supplied from a hydraulic source through a common oil passage to each cylinder. Since the pressure is supplied to the cylinder provided in one of the first and second rocker arms, the hydraulic pressure greatly fluctuates when the piston is returned by the contact protrusion in one of the first and second rocker arms of one cylinder. Pulsation occurs in the common oil passage, the hydraulic pressure supplied to the cylinders of the other cylinders temporarily drops, and the opening is easily closed in a state where the piston is halfway, so that the first rocker arm and the first cam Abrupt contact or sudden contact between the valve face of the intake or exhaust valve and the valve seat occurs in a chain, and it is easy to generate a loud impact noise. Formed on the tip surface of the part By so forcefully securely push back the inclined surface, it is possible to suppress the generation of such a large impact sound, damage of the variable valve mechanism, it is possible to reduce wear.
[0055]
According to the valve gear of the internal combustion engine of the fourth aspect, the inclination angle of the inclined surface is set within a predetermined angle range having a central value of 35 ° with respect to the front end surface of the front end portion. The inclined surface can always push back stably and reliably, whereby the generation of the impact noise can be accurately suppressed, and the failure and wear of the variable valve mechanism can be satisfactorily reduced.
[Brief description of the drawings]
FIG. 1 is a detailed view showing a cylinder and a piston in a connection switching mechanism in a valve operating apparatus for an SOHC type engine including a variable valve operating mechanism according to the present invention.
FIG. 2 is a detailed view showing a contact protrusion having an inclined surface according to the present invention of FIG. 1;
FIG. 3 is a view showing a case where an opening is closed in a state where a piston is halfway, and is a view for explaining an operation of the present invention.
FIG. 4 is a graph showing a test result of an impact sound generation frequency with respect to an inclination angle of an inclined surface.
FIG. 5 is a view showing a configuration of a valve operating device of an SOHC type engine including a variable valve operating mechanism proposed by the applicant, and is a view showing a basic configuration of the present invention.
FIG. 6 is a sectional view taken along line AA of FIG.
FIG. 7 is a detailed view showing a cylinder and a piston in the connection switching mechanism of FIG. 5;
FIG. 8 is a detailed view showing a part of a hydraulic pressure adjusting device in the connection switching mechanism of FIG. 5;
FIG. 9 is a diagram showing operating characteristics (valve lift) of the intake valve of FIG. 5 at low speed and high speed.
[Explanation of symbols]
11,12 Intake valve
21,22 exhaust valve
31a, 31b Low-speed cam (first cam)
31c High speed cam (second cam)
32 rocker shaft
33,34 rocker arm (first rocker arm)
40 Variable valve mechanism
41 Connection switching mechanism
42 Hydraulic pressure adjusting device (piston operating means)
42a, 42b Common oil passage
42c branch oilway
42d oil control valve (oil pressure adjustment means)
50 cylinder
51 piston
51a side view
52 spring (elastic member)
53 opening
135 Rocker arm (second rocker arm)
135a contact projection
135c tip
135d tip surface
135e slope
140 Variable valve mechanism

Claims (4)

A first rocker arm that swings following a first cam that rotates with the rotation of the camshaft to open or close one of an intake valve and an exhaust valve;
A second rocker arm having a shape different from that of the first cam and swinging in accordance with a second cam that rotates with the rotation of the camshaft;
A cylinder formed on one of the first rocker arm and the second rocker arm and having an opening in a part of a sliding surface;
A piston slidably mounted along the sliding surface in the cylinder, and a side slid by an elastic member biased toward one sliding end of the cylinder that does not block the opening;
Piston actuation means for actuating the piston toward the other sliding end of the cylinder in which the side surface of the piston seals the opening in the cylinder against the urging force of the elastic member;
The piston is provided at one of the first rocker arm and the second rocker arm so that the piston is at the one sliding end of the cylinder by the swinging of the first rocker arm and the second rocker arm. Sometimes, the tip is inserted into the cylinder through the opening, while the piston is in a position where the side of the piston closes the opening by the operation of the piston operating means, the tip contacts the side. With a contact projection that touches,
A valve device for an internal combustion engine, characterized in that an inclined surface is formed at a tip portion of the contact protrusion at a corner on one sliding end side of the cylinder. The piston operating means is for operating the piston with hydraulic oil supplied from a hydraulic pressure source via an oil path, and has a hydraulic pressure adjusting means in the oil path, and the hydraulic pressure is adjusted according to an operating state of an internal combustion engine. 2. The valve train for an internal combustion engine according to claim 1, wherein the hydraulic pressure is increased by adjusting means, and the piston is operated against the urging force of the elastic member. The internal combustion engine is a multi-cylinder internal combustion engine, and the hydraulic adjustment means is provided for each cylinder together with the first rocker arm and the second rocker arm, and the hydraulic adjustment means is provided with an oil branched from a common oil passage extending from a hydraulic source. 3. The valve train of an internal combustion engine according to claim 2, wherein the valve train is provided on each of the roads. The internal combustion engine according to any one of claims 1 to 3, wherein an inclination angle of the inclined surface is set within a predetermined angle range having a central value of 35 ° with respect to a distal end surface of the distal end portion. Valve gear.

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