JP2008202513A - Variable valve mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a variable valve mechanism efficiently adjusting an energizing mechanism. <P>SOLUTION: The variable valve train 10 comprises a camshaft 41 for intake system, first and second cams 43, 42 for intake system, a rocker shaft 44 for intake system, first and second rocker arms 45, 46 for intake system, a transmission mechanism 80, and a leaf spring member 70. The first rocker arm 45 for intake system is disposed to be capable of oscillating around a shaft center line of the rocker shaft 44 for intake system and is driven by the first cam 43 for intake system. The second rocker arm 46 for intake system is rockably disposed to the rocker shaft 44 for intake system and is connected to an intake valve 23. The transmission mechanism 80 transmits displacement of the first cam 43 for intake system to the intake valve 23, by selectively abutting the first rocker arm 45 for intake system on the second rocker arm 46 for intake system. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a variable valve mechanism that varies the phase of an intake valve or an exhaust valve.

  Many variable valve mechanisms for engines mounted on automobiles are equipped with multiple cams that correspond to the engine operating conditions from the viewpoint of engine exhaust gas countermeasures, etc., and these cams are switched according to the engine operating conditions. Is adopted. For example, a low-speed cam and a high-speed cam are provided, and an appropriate one according to the operating state of the engine is used.

  This type of variable valve mechanism is used, for example, in a high-speed rocker arm driven by a high-speed cam used in high-speed operation with a high engine speed and in a low-speed operation with a low engine speed. And a low-speed rocker arm driven by a low-speed cam.

  The low-speed rocker arm drives an intake valve or an exhaust valve. The high speed rocker arm does not directly drive the intake valve or the exhaust valve, but indirectly drives the intake valve by driving the low speed rocker arm.

  Specifically, a transmission mechanism is provided between the high-speed rocker arm and the low-speed rocker arm that can contact each other and release the contact.

  As an example of this mechanism, a low-speed rocker arm is provided with a cylindrical housing that is partially opened toward a high-speed cam, and a piston that moves in the housing is accommodated in the housing. The high-speed rocker arm is formed with a protrusion that protrudes toward the opening.

  When the engine is operating at a low speed, the piston is disposed at a position that is out of the opening. As a result, even if the rocker arm driven by the high-speed cam is driven, the protrusion only moves back and forth between the inside and the outside of the cylinder through the opening. Therefore, the displacement of the high-speed rocker arm driven by the high-speed cam is not transmitted to the low-speed rocker arm. As a result, the intake valve or the exhaust valve is driven with an opening / closing timing and a valve lift amount suitable for low-speed operation of the engine.

  When the engine is in a high speed operation state, the piston is disposed at a position covering the opening. As a result, the protrusion of the high-speed rocker arm comes into contact with the piston through the opening. As a result, the low-speed rocker arm is driven by the high-speed rocker arm. That is, the intake valve or the exhaust valve is indirectly driven by the high-speed rocker arm, so that the intake valve or the exhaust valve is driven at an opening / closing timing and a valve lift amount suitable for high-speed operation of the engine.

  In this type of variable valve mechanism, the high-speed rocker arm is driven by the high-speed cam even when the engine is in a low-speed operation state. At this time, since the high-speed rocker arm does not contact the low-speed rocker arm, its posture becomes unstable. In other words, the high-speed rocker arm is free to rotate around the rocker shaft. Therefore, a hitting sound when the high-speed rocker arm comes into contact with the high-speed cam or rattling of the high-speed rocker arm occurs. The problem occurs.

As a countermeasure, the cylinder head is provided with a biasing mechanism that biases the high-speed rocker arm toward the high-speed cam. The urging mechanism prevents the high-speed rocker arm from moving away from the high-speed cam, and therefore, it is possible to suppress the occurrence of hitting sound and rattling of the high-speed rocker arm (see, for example, Patent Document 1).
JP 2005-105953 A

  However, in Patent Document 1, the urging mechanism is provided in the cylinder head. Therefore, after each element constituting the variable valve mechanism is assembled to the cylinder head, the urging mechanism and the high-speed rocker arm are adjusted.

  The member to which the urging mechanism is attached is a cylinder head, and the member to which the high speed rocker arm is attached is a rocker shaft. Thus, since the members to which each is attached are different, it may be difficult to adjust the alignment between the urging mechanism and the high-speed rocker arm due to an assembly error or the like.

  Accordingly, an object of the present invention is to provide a variable valve mechanism that can efficiently adjust the urging mechanism.

  The variable valve mechanism of the present invention includes a camshaft, a first cam, a rocker shaft, a first rocker arm, a second rocker arm, a transmission mechanism, and an urging mechanism. The camshaft is rotatably provided. The first cam is provided on the camshaft. The first rocker arm is provided on the rocker shaft and is swingable about an axis of the rocker shaft. The first rocker arm is driven by the first cam. The second rocker arm is provided on the rocker shaft and is swingable about the axis of the rocker shaft. The second rocker arm is connected to a valve. The transmission mechanism transmits the displacement of the first cam to the valve by selectively abutting the first rocker arm and the second rocker arm. The urging mechanism is provided on the rocker shaft and urges the first rocker arm toward the first cam.

  In this structure, the biasing mechanism and the first rocker arm are integrally assembled to the rocker shaft. Therefore, for example, a unit configured by assembling the urging mechanism and the first rocker arm to the rocker shaft can be mounted on the internal combustion engine. As a result, adjustment such as alignment between the biasing mechanism and the first rocker arm can be performed only by the above-described unit.

  In a preferred form of the invention, the second rocker arm is driven by a second cam having a different cam profile than the first cam. In this configuration, the valve can be driven with different cam profiles.

  In a preferred embodiment of the present invention, the biasing mechanism is a leaf spring member. With this structure, the urging mechanism can be made simple and compact.

  In a preferred embodiment of the present invention, second rocker arms are provided on both sides of the first rocker arm. In this structure, two valves can be driven simultaneously.

  In a preferred embodiment of the present invention, the transmission mechanism is a contact mechanism including a cylinder and a piston, and a transmission unit that selectively contacts the piston. With this structure, transmission / non-transmission of displacement by the first cam can be switched reliably. Furthermore, when the transmission portion is provided in the first rocker arm, an increase in the weight of the first rocker arm can be suppressed, which is advantageous in adjusting the urging force and durability of the urging mechanism.

  According to the present invention, the biasing mechanism can be adjusted efficiently.

  A variable valve mechanism according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows an engine 20 including a variable valve mechanism 10. The engine 20 is, for example, a reciprocating type in which four cylinders are arranged in series, and a DOHC (DOUBLE OVERHEAD CAMSHAFT) type. As shown in FIG. 1, the engine 20 includes a cylinder head 21 and a cylinder block (not shown). FIG. 1 is a perspective view showing the cylinder head 21 from above.

  The variable valve mechanism 10 is fixed to a mounting surface 22 of the cylinder head 21 (a surface positioned upward in the drawing). The variable valve mechanism 10 includes an exhaust system 30 and an intake system 40. The engine 20 is provided with, for example, a pair of intake ports and a pair of exhaust ports per cylinder, and is provided with a pair of intake valves and a pair of exhaust valves.

  The exhaust system 30 includes an exhaust system camshaft 31, a pair of exhaust system cams 32 per cylinder, an exhaust system rocker shaft (not shown), a pair of exhaust system rocker arms 33 per cylinder, and the like. It has.

  The exhaust system camshaft 31 is supported on the mounting surface 22 of the cylinder head 21 by a plurality of exhaust system support portions 34. The exhaust system support 34 includes a fixed member 35 and a cover member 36. The fixed member 35 is fixed to the mounting surface 22 of the cylinder head 21. The covering member 36 is attached to the fixed member 35 from the side opposite to the mounting surface 22 with the fixed member 35 interposed therebetween.

  The exhaust system camshaft 31 is rotatably supported between the fixed member 35 and the covering member 36. Although not shown, a cam pulley is provided at one end of the exhaust system camshaft 31. The rotation of the crankshaft is transmitted to the cam pulley via a timing belt.

  A pair of exhaust system cams 32 is provided for each cylinder on the exhaust system cam shaft 31. The exhaust system rocker shaft extends in parallel with the exhaust system camshaft 31 and is fixed to the cylinder head 21, for example. The exhaust system rocker shaft is disposed, for example, on the rear side of the exhaust system camshaft 31 in the figure, and is therefore not shown.

  The exhaust system rocker arm 33 is swingably supported by the exhaust system rocker shaft. The exhaust system rocker arm 33 drives an exhaust valve (not shown). The exhaust system rocker arm 33 is disposed, for example, closer to the mounting surface 22 of the cylinder head 21 than the exhaust system camshaft 31. The exhaust system rocker arm 33 is provided with a roller member that contacts the exhaust system cam 32, and the roller member contacts the exhaust system cam 32 from the mounting surface 22 side. When the roller member comes into contact with the exhaust system cam, the displacement of the exhaust system cam is transmitted to the exhaust system rocker arm 33, so that the exhaust system rocker arm 33 swings.

  The intake system 40 includes an intake system camshaft 41, a second intake system cam 42, a first intake system cam 43, an intake system rocker shaft 44, and a first intake system rocker arm 45. The second intake system rocker arm 46, a transmission mechanism 80, a leaf spring member 70, and the like are provided.

  FIG. 2 is an exploded perspective view showing a part of the intake system 40. In FIG. 2, the part corresponding to one cylinder in the intake system 40 is disassembled. As shown in FIG. 1, the intake system camshaft 41 extends in parallel with the exhaust system camshaft 31.

  The intake system camshaft 41 is fixed to the mounting surface 22 of the cylinder head 21 by a plurality of intake system support portions 47. The intake system camshaft 41 is a camshaft referred to in the present invention. The intake system support 47 includes a fixed member 48 and a cover member 49.

  The fixed member 48 is fixed to the attachment surface 22. The cover member 49 is attached to the fixed member 48 from the opposite side of the attachment surface 22. The intake system camshaft 41 is rotatably supported between a fixed member 48 and a cover member 49. A cam pulley (not shown) is provided at one end of the intake system camshaft 41. The rotation of the crankshaft is transmitted to the cam pulley via a timing belt (not shown).

  The intake system camshaft 41 is provided with a pair of second intake system cams 42 and one first intake system cam 43 per cylinder. The second intake system cam 42 is used when the engine 20 is in a low-speed operation state where the engine speed is low, and the intake air is taken in with an opening / closing timing and a valve lift amount suitable for low-speed operation of the engine 20. It has a cam profile that can drive the valve 23. The second intake system cam 42 is the second cam referred to in the present invention. The intake valve 23 is an example of a valve in the present invention.

  The first intake system cam 43 is a cam used when the engine 20 is in a high-speed operation state, and is a cam profile that can drive the intake valve 23 with an opening / closing timing and a valve lift amount suitable for high-speed operation of the engine 20. Have The first intake system cam 43 is the second cam referred to in the present invention.

  The lift amount of the first intake system cam 43 is larger than the lift amount of the second intake system cam 42. One second intake system cam 42 is disposed on each side of the first intake system cam 43.

  The intake system rocker shaft 44 extends in parallel with the intake system camshaft 41. The intake system rocker shaft 44 is disposed on the opposite side of the exhaust system camshaft 31 with the intake system camshaft 41 interposed therebetween. The intake system rocker shaft 44 is fixed to the cylinder head 21 with bolts 24, for example. The intake system rocker shaft 44 is an example of a rocker shaft according to the present invention.

  As shown in FIG. 2, the second intake system rocker arm 46 is disposed on both sides of the first intake system rocker arm 45, and is swingably supported by the intake system rocker shaft 44. ing. In other words, the second intake system rocker arms 46 are arranged on the left and right sides of the first intake system rocker arm 45 along the axial direction of the intake system rocker shaft 44.

  The second intake system rocker arm 46 is driven by the second intake system cam 42 to drive the intake valve 23. The second intake system rocker arm 46 is disposed closer to the mounting surface 22 side of the cylinder head 21 than the intake system camshaft 41. The second intake system rocker arm 46 is the second rocker arm referred to in the present invention.

  The second intake system rocker arm 46 includes a second main body 60 and a second roller member 61. The second main body 60 is, for example, a frame type having a space B inside. A second insertion hole 63a is formed in one end 63 of the second main body 60, and the intake system rocker shaft 44 is swingably inserted into the second insertion hole 63a.

  An adjustment screw part 200 is provided at the other end of the second main body 60 (opposite the one end 63). The adjusting screw part 200 is in contact with the intake valve 23. In other words, the second intake system rocker arm 46 is connected to the intake valve 23.

  The second roller member 61 is rotatably supported by the second shaft member 62 in the second main body 60. The second roller member 61 is disposed closer to the attachment surface 22 than the intake system camshaft 41 and is in contact with the second intake system cam 42 from the attachment surface 22 side. Therefore, the displacement of the second intake system cam 42 accompanying the rotation of the intake system camshaft 41 is transmitted to the second roller member 61.

  As a result, the second intake system rocker arm 46 is driven by the second intake system cam 42. FIG. 3 is a side view showing the second intake system rocker arm 46 with a part cut away. As shown in FIG. 3, the second intake system rocker arm 46 swings within the range of the angle β. The shape of the second intake system rocker arm 46 described above is merely an example, and other structures may be employed.

  Note that, as described above, the intake valve 23 is driven via the adjusting screw portion 200 by the swing of the second intake system rocker arm 46.

  As shown in FIG. 2, the first intake system rocker arm 45 is swingably supported by the intake system rocker shaft 44, and is closer to the mounting surface 22 side of the cylinder head 21 than the intake system camshaft 41. Is arranged. The first intake system rocker arm 45 is driven by the first intake system cam 43. The first intake system rocker arm 45 is the first rocker arm referred to in the present invention.

  The first intake system rocker arm 45 includes a first main body 50 and a first roller member 51. The first main body 50 is swingably supported by the intake system rocker shaft 44. The first main body 50 has a shape in which one end portion 52 is divided into two forks. A first insertion hole 53a is formed in the other end portion 53, and is communicated with the intake system rocker shaft 44 in the first insertion hole 53a in a swingable manner.

  The first roller member 51 is rotatably accommodated in one end portion 52 formed in a bifurcated shape in the first main body 50, and is rotatably supported between the one end portions 52 by the first shaft member 54. ing. The first roller member 51 is disposed at a position facing the first intake system cam 43 for intake system, and is in contact with the first intake system cam 43 from the mounting surface 22 side. Therefore, the displacement of the first intake system cam 43 accompanying the rotation of the intake system camshaft 41 is transmitted to the first roller member 51.

As a result, the first intake system rocker arm 45 is driven by the second intake system cam 42. FIG. 4 is a side view showing the first intake system rocker arm 45. As shown in FIG. 4, the first intake system rocker arm 45 swings in the range of the angle α. The first intake system rocker arm 45 faces the first intake system cam 43 by the leaf spring member 70. Is energized. As shown in FIG. 2, an opening 55 is formed in a portion of the first main body 50 facing the intake system rocker shaft 44 in the middle of the stomach along the intake system rocker shaft 44. A portion of the intake system rocker shaft 44 is exposed to the outside through the opening 55.

  As shown in FIG. 4, one end portion 71 of the leaf spring member 70 is fixed to a portion exposed through the opening 55 in the intake system rocker shaft 44. For example, as shown in FIG. 2, a groove 110 may be formed in the intake system rocker shaft 44, and one end 71 of the leaf spring member 70 may be fitted and fixed to the groove 110. The fixing structure of the leaf spring member 70 and the intake system rocker shaft 44 is not limited to the above. In short, the leaf spring member 70 and the intake system rocker shaft 44 may be fixed. The other end 72 extends around the intake system rocker shaft 44 and extends to the opposite side of the intake system camshaft 41. Therefore, as shown in FIG. 2, the leaf spring member 70 is substantially L-shaped.

  As shown in FIG. 4, the first main body 50 is formed with a protrusion 56 that contacts the other end 72 of the leaf spring member 70. The protrusion 56 protrudes gently toward the opposite side of the intake system camshaft 41, that is, toward the other end 72 of the leaf spring member 70, and abuts against the other end 72. The other end 72 of the leaf spring member 70 is curved so as to gently protrude toward the protrusion 56.

  The leaf spring member 70 is bent in an L shape and the other end 72 is in contact with the projection 56, so that the first main body 50 is shown as an arrow A in FIG. It is energizing towards.

  Since the first intake system cam 43 is larger than the second intake system cam 42, the angle β is smaller than the angle α.

  As shown in FIG. 2, the displacement of the first intake system rocker arm 45 is transmitted to the second intake system rocker arm 46 to the first intake system rocker arm 45 and the second intake system rocker arm 46. A transmission mechanism 80 is provided.

  The transmission mechanism 80 includes a transmission unit 81 and a contact mechanism 82. The transmission portion 81 is formed integrally with the first intake system rocker arm 45. Specifically, the transmission portion 81 is located on the other end portion 53 of the first main body 50 on the opposite side of the mounting surface 22 of the cylinder head 21 with the first insertion hole 53a interposed therebetween.

  As shown in FIGS. 2 and 4, the transmission portion 81 extends outward from the first main body 50 along the intake system rocker shaft 44, and further toward the intake system camshaft 41. It protrudes.

  As shown in FIG. 2, the contact mechanism 82 is provided in each second intake system rocker arm 46. In the second main body 60, the second insertion hole 63 a is sandwiched between the mounting surface 22 and the second abutment mechanism 82. Are arranged. FIG. 5 shows a state in which the first and second intake system rocker arms 45 and 46 are assembled to the intake system rocker shaft 44 from the opposite side of the intake system camshaft 41 across the intake system rocker shaft 44. It is a perspective view which shows the state seen. As shown in FIG. 5, specifically, the abutment mechanism 82 is disposed in the second main body 60 at a position overlapping the swinging direction of the transmission portion 81.

  FIG. 3 is a side view showing the second intake system rocker arm 46 as seen from the side, with a part cut away. In FIG. 3, the vicinity of the second insertion hole 63 a and the contact mechanism 82 in the second main body 60 are shown in cross-section in a direction crossing the intake system rocker shaft 44.

  As shown in FIG. 3, the contact mechanism 82 includes a housing 83, a first piston 84, a spring 87, and a second piston 85 for improving responsiveness. Note that the second piston 85 may not be used depending on performance specifications, cost, and the like. The housing 83 is fixed to the second main body 60. An opening 86 is formed in a portion of the housing 83 that faces the transmission portion 81 when the first intake system rocker arm 45 swings. The transmission portion 81 has a shape that can enter the housing 83 through the opening 86.

  The first piston 84 is substantially fitted in the housing 83 and is slidable in the housing 83. A spring 87 is provided between the first piston 84 and the roof portion 83 a of the housing 83. Therefore, the first piston 84 is biased by the spring 87 toward the intake system rocker shaft 44 side. The first piston 84 can move against the biasing force of the spring 87 until, for example, the upper end 88 of the first piston 84 abuts against the roof portion 83a of the housing 83, as indicated by a two-dot chain line in the figure. is there.

  The first piston 84 is urged by a spring 87, and can move in the housing 83 against the spring 87. This point will be specifically described. A passage 44 a through which engine oil flows is formed in the intake system rocker shaft 44. A first communication hole 89 penetrating the peripheral wall toward the housing 83 is formed at a location facing the housing 83 on the peripheral wall of the intake system rocker shaft 44.

  A second communication hole 90 that penetrates through the second main body 60 and connects the inside of the housing 83 and the first communication hole 89 is formed at a position facing the first communication hole 89 in the second main body 60. Has been. With this structure, the inside of the housing 83 and the passage 44 a communicate with each other through the first and second communication holes 89 and 90.

  A second piston 85 is accommodated in the first and second communication holes 89 and 90. The second piston 85 is substantially fitted in the first and second communication holes 89 and 90. An oil control valve for opening and closing the passage is provided in a passage for engine oil following the passage 44 a in the intake system rocker shaft 44. The oil pressure in the passage 44a is increased by the control of the oil control valve, and as a result, the second piston 85 is pushed up. The tip of the second piston 85 is in contact with the first piston 84.

  The first piston 84 is biased toward the second main body 60 by the spring 87, but is pushed up by the second piston 85 as the pressure in the passage 44 a increases and moves toward the roof portion 83 a of the housing 83. Move. The position where the first piston 84 is pressed down by the spring 87 and contacts the second main body 60 is defined as a first position P1. A position where the first piston 84 is pushed up by the second piston 85 and contacts the roof portion 83a of the housing 83 is defined as a second position P2.

  The first piston 84 is formed with a notch 92. The notch 92 is formed by cutting out a portion of the first piston 84 facing the opening 86 of the housing 83 from the upper end to the middle. Specifically, the notch 92 is configured so that the peripheral wall of the first piston 84 does not cover the opening 86 of the housing 83 when the first piston 84 is at the first position P1. When in the second position P <b> 2, the peripheral wall of the first piston 84 is formed so as to cover the opening 86.

  Here, the positional relationship between the transmission portion 81 of the first intake system rocker arm 45 and the first piston 84 of the second intake system rocker arm 46 will be specifically described. The first piston 84 is in the second position P2, and the base circle portions of the first and second intake system cams 43 and 42 are in contact with the first and second roller members 51 and 61. That is, in a state where the first and second intake system rocker arms 45 and 46 are not swinging, the transmission portion 81 is disposed at a position that substantially contacts the first piston 84 through the opening 86.

  FIG. 7 is a side view showing the first and second intake system rocker arms 45 and 46 in a state in which the first piston 84 is positioned at the first position P1. As shown in FIG. 7, in a state where the first piston 84 is in the first position P <b> 1, the transmission unit 81 is configured so that the transmission unit 81 passes through the opening 86 and the transmission unit 81 enters the housing 83. It is formed so as not to contact the first piston 84.

  Further, for example, a detent mechanism 100 is provided between the housing 83 and the first piston 84. The anti-rotation mechanism 100 prevents the first piston 84 from rotating within the housing 83. As an example of the anti-rotation mechanism 100, for example, a protrusion 101 formed on the outer peripheral surface of the first piston 84 and a groove 102 formed on the inner peripheral wall of the housing 83 to movably accommodate the protrusion 101 are provided. Have. The protrusion 101 extends in the axial direction of the first piston 84. The groove 102 extends in the axial direction of the first piston 84.

  Therefore, when the first piston 84 moves in the housing 83, the protrusion 101 is guided by the groove portion 102, so that the rotation of the first piston 84 about the axial direction is suppressed. The

  Next, an example of a procedure for assembling the variable valve mechanism 10 to the cylinder head 21 will be described. As shown in FIG. 2, in the intake system 40, for example, first and second intake system rocker arms 45 and 46 are first assembled to the intake system rocker shaft 44. Next, the leaf spring member 70 is assembled to the intake rocker shaft 44 through the opening 55 formed in the first main body 50. At this time, the leaf spring member 70 and the first intake system rocker arm 45 are adjusted. Specifically, alignment between the protrusion 56 of the first main body 50 and the other end 72 of the leaf spring member 70 is performed.

  Next, the units of the intake system rocker shaft 44 and the first and second intake system rocker arms 45 and 46 are fixed to the cylinder head 21. Further, the intake system camshaft 41 is fixed to the cylinder head 21 via the intake system support 47.

  As shown in FIG. 1, the exhaust system rocker arm 33 and the exhaust system rocker shaft unit are similarly fixed to the cylinder head 21 even in the exhaust system 30. Further, the exhaust system camshaft 31 is fixed to the cylinder head 21 via the exhaust system support portion 34.

  Next, the operation of the intake system 40 of the variable valve mechanism 10 will be described. In a low-speed operation state where the engine 20 has a low speed, the oil control valve is closed. Therefore, engine oil is not supplied to the passage 44 a in the intake system rocker shaft 44. However, in order to supply a small amount of oil for lubrication between the intake system rocker shaft 44 and the first and second intake system rocker arms 45 and 46, for example, a small hole is provided in the oil control valve. The oil flows into the passage 44a through the hole. However, the hole is designed so that even if oil flows into the passage 44a through this hole, the second piston 85 is not pushed up by the flowing oil.

  As a result, in a state where the engine 20 is operating at a low speed, the first piston 84 is not pushed up by the second piston 85, and thus is positioned at the first position P1 by the biasing force of the spring 87.

  As shown in FIG. 7, the first intake system rocker arm 45 is driven by the first intake system cam 43 even when the engine 20 is in a low-speed operation state. However, since the first piston 84 is in the first position P1, even if the first intake system rocker arm 45 swings, the transmission portion 81 does not come into contact with the first piston 84. The swing of the first intake system rocker arm 45 is not transmitted to the second intake system rocker arm 46.

  In a state where the engine 20 is operating at a low speed, the intake valve 23 is driven by a second intake system rocker arm 46 driven by a second intake system cam 42. As a result, the intake valve 23 is driven with an opening / closing timing and a valve lift amount suitable for low-speed operation.

  FIG. 8 is a graph showing the opening / closing valve timing and lift amount of the exhaust valve and the intake valve 23 when the engine 20 is operating at a low speed and when the engine 20 is operating at a high speed. FIG. 8 shows the opening / closing valve timing and lift amount of the intake valve 23 when the engine 20 is operating at a low speed (operating state driven by the second intake cam 42).

  Note that the first roller member 51 is always in contact with the first intake system cam 43 by the leaf spring member 70. Therefore, even if the transmission portion 81 of the first intake system rocker arm 45 is in the free state, that is, the transmission portion 81 can enter the housing 83 through the opening 86 and is not biased from anywhere. The posture of the intake system rocker arm 45 does not become unstable. Therefore, the hitting sound caused by the first roller member 51 colliding with or separating from the first intake system cam 43 does not occur. Furthermore, the occurrence of rattling due to the unstable posture of the first intake system rocker arm 45 is suppressed.

  When the engine 20 is in a high-speed operation state, specifically, in a state where the engine 20 is operated in a high-speed range where the engine speed exceeds the threshold speed, the oil control valve opens. Thus, the engine oil passes through the passage 44 a in the intake system rocker shaft 44. As a result, the pressure in the passage 44a increases.

  FIG. 6 is a side view showing the first and second intake system rocker arms 45 and 46 in a state where the first piston 84 is at the second position P2. As shown in FIG. 6, the second piston 85 is pushed up by increasing the pressure in the passage 44a. As the second piston 85 rises, the first piston 84 is pushed up by the second piston 85 and moves from the first position P1 to the second position P2. As a result, the transmission portion 81 of the first intake system rocker arm 45 comes into contact with the first piston of the second intake system rocker arm 46 through the opening 86.

  When the engine 20 is in a high speed operation state, the displacement of the first intake system rocker arm 45 is displaced via the transmission mechanism 80 by the transmission portion 81 coming into contact with the first piston 84. 46. Therefore, the second intake system rocker arm 46 swings by the angle α, which is the swing amount of the first intake system cam 43.

  As described above, when the engine 20 is in a high speed operation state, the intake valve 23 is driven by the first intake system cam 43, so that the intake valve 23 is operated at an opening / closing timing and a valve lift amount suitable for high speed operation. FIG. 8 shows the opening / closing valve timing and lift amount of the intake valve 23 when the engine 20 is in a high-speed operation state (a state driven by the first intake system cam 43). As described above, the transmission mechanism 80 causes the first intake system rocker arm 45 to abut on the second intake system rocker arm 46 in accordance with the operating state of the engine 20, thereby causing the first intake system cam 43 to contact the first intake system rocker arm 46. This displacement is transmitted to the intake valve 23.

  In the variable valve mechanism 10 thus configured, the leaf spring member 70, which is an example of an urging mechanism, is fixed to the intake system rocker shaft 44. Therefore, the leaf spring member 70 and the first intake system rocker arm are fixed. Adjustment operations such as alignment with 45, specifically, alignment between the protrusion 56 and the other end 72 of the leaf spring member 70 can be performed efficiently.

  Further, since the first and second intake system cams 43 and 42 have different cam profiles, the intake valve 23 can be driven in different operating states. In other words, the engine 20 can be operated in different operating states.

  Further, since the second intake system rocker arm 46 is disposed on both the left and right sides of the first intake system rocker arm 45, the two intake valves 23 can be driven simultaneously.

  Furthermore, by using the leaf spring member 70 as an example of the urging mechanism, the structure of the variable valve mechanism 10 can be simplified and the variable valve mechanism 10 can be made compact.

  The transmission mechanism 80 includes a contact mechanism 82 including a cylinder and a piston, and a transmission unit 81 that selectively contacts the contact mechanism 82. For this reason, transmission / non-transmission of the displacement of the first intake system cam 43 is reliably switched.

  Further, by providing the first intake system rocker arm 45 with the transmission portion 81, the weight of the first intake system rocker arm 45 can be reduced. This is advantageous for adjustment and durability of the urging mechanism, specifically the urging force of the leaf spring member 70.

  Next, a variable valve mechanism according to a second embodiment of the present invention will be described with reference to FIGS. In addition, the structure which has a function similar to 1st Embodiment attaches | subjects the same code | symbol, and abbreviate | omits description.

  In the present embodiment, the structure of the intake system camshaft 41 and the structure of the first intake system rocker arm 45 are different from those of the first embodiment. Other structures may be the same as those in the first embodiment. The different points will be specifically described.

  FIG. 9 is a perspective view showing a state in which the first intake system rocker arm 45 of the present embodiment is disassembled and the intake system camshaft 41. FIG. 10 is a side view showing the intake system camshaft 41 and the first intake system rocker arm 45 of the present embodiment.

  As shown in FIGS. 9 and 10, in the present embodiment, the intake system camshaft 41 is disposed closer to the mounting surface 22 of the cylinder head 21 than the first intake system rocker arm 45. The first intake system cam 43 is in contact with the first roller member 51 from the mounting surface 22 side. The first roller member 51 is provided so that the first intake system cam 43 can come into contact with the first roller member 51 from the mounting surface 22 side.

  The leaf spring member 70 biases the first main body 50 from the side opposite to the mounting surface 22 with the first main body 50 interposed therebetween. Therefore, the protrusion 56 is provided on the first main body 50 on the side opposite to the attachment surface 22. Further, in the vicinity of the first insertion hole 53 a of the first main body 50, a groove 57 through which the leaf spring member 70 is passed is formed on the side opposite to the attachment surface 22.

  Although not shown, the second intake system rocker arm 46 is also disposed closer to the mounting surface 22 than the intake system camshaft 41. The second roller member 61 is in contact with the second intake system cam 42 from the attachment surface 22 side. The second roller member 61 is provided so that the second intake system cam 42 can come into contact with the second roller member 61 from the mounting surface 22 side.

  In this embodiment, in addition to the effects of the first embodiment, the leaf spring member 70 is used, so that the intake system camshaft 41 has the first and second intake system rocker arms 45 and 46 as in the above-described structure. In addition, the height of the variable valve mechanism 10 can be kept low in the structure that is disposed closer to the mounting surface 22 side.

  In the first and second embodiments, the case where the leaf spring member 70 which is an example of the urging mechanism is used in the intake system 40 has been described, but the present invention is not limited to this. For example, a structure in which the leaf spring member 70 is used for the exhaust system 30 may be used. Further, the biasing mechanism is not limited to the leaf spring member 70. Other mechanisms and members may be used for the urging mechanism. In short, it is sufficient that the first rocker arm referred to in the present invention can be biased to the first cam referred to in the present invention.

  In the first and second embodiments, the variable valve mechanism using the low speed cam and the high speed cam has been described. For example, the second cam has no base circle or the cam itself, and the valve lift is stopped. It can also be applied to a cylinder resting mechanism.

  In the first and second embodiments, the contact mechanism 82 is provided in the second intake system rocker arm 46 and the transmission unit 81 is provided in the first intake system rocker arm 45. However, the present invention is not limited to this. . For example, the contact mechanism 82 may be provided in the first intake system rocker arm 45, and the transmission unit 81 may be provided in the second intake system rocker arm 46.

1 is a perspective view showing an engine including a variable valve mechanism according to a first embodiment of the present invention. The perspective view which decomposes | disassembles and shows a part of intake system shown by FIG. FIG. 3 is a side view of the first intake system rocker arm shown in FIG. The side view which shows the 2nd rocker arm for intake systems shown by FIG. FIG. 2 shows a state in which the first and second intake system rocker arms are assembled to the intake system rocker shaft shown in FIG. 2 as viewed from the opposite side of the intake system camshaft across the intake system rocker arm. Perspective view. FIG. 2 is a side view showing the first and second intake system rocker arms shown in FIG. 2 when the first piston is in the second position. FIG. 7 is a side view showing first and second intake system rocker arms in a state where the first piston shown in FIG. 6 is positioned at a first position. FIG. 2 is a graph showing opening / closing valve timings and lift amounts of an exhaust valve and an intake valve when the engine shown in FIG. 1 is operating at a low speed and when operating at a high speed. The perspective view which shows the state by which the 1st rocker arm for intake systems of the variable valve mechanism which concerns on the 2nd Embodiment of this invention was decomposed | disassembled, and the camshaft for intake systems. FIG. 10 is a side view showing the intake system camshaft and the first intake system rocker arm shown in FIG. 9.

Explanation of symbols

  23 ... Intake valve (valve), 41 ... Intake system camshaft (camshaft), 42 ... First intake system cam (first cam), 43 ... Second intake system cam (second cam) ) 44... Intake system rocker shaft (Rocker shaft) 45. Second intake system rocker arm (second rocker arm) 46. First intake system rocker arm (first rocker arm) 70. Member (biasing mechanism), 80 ... transmission mechanism, 81 ... transmission section, 82 ... contact mechanism.

Claims (5)

A camshaft provided rotatably,
A first cam provided on the camshaft;
A rocker shaft provided in parallel with the camshaft;
A first rocker arm provided on the rocker shaft and swingable about an axis of the rocker shaft, and driven by the first cam;
A second rocker arm provided on the rocker shaft and swingable about an axis of the rocker shaft and connected to a valve;
A transmission mechanism capable of transmitting the displacement of the first cam to the valve by selectively abutting the first rocker arm and the second rocker arm, and the rocker shaft provided to the first rocker arm. An urging mechanism that urges toward the first cam;
A variable valve mechanism characterized by comprising:   The variable valve mechanism according to claim 1, wherein the second rocker arm has a cam profile different from that of the first cam and is driven by a second cam provided on the camshaft.   The variable valve mechanism according to claim 1, wherein the urging mechanism is a leaf spring member. The second rocker arm is provided on each side of the first rocker arm,
One transmission mechanism is provided corresponding to one second rocker arm and the first rocker arm, and one transmission mechanism is provided corresponding to the other second rocker arm and the first rocker arm. The variable valve operating structure according to any one of claims 1 to 3, wherein: The transmission mechanism is provided on one of the first rocker arm and the second rocker arm, a cylinder communicating with an oil passage provided on the rocker shaft, and a piston slidably inserted into the cylinder. A contact mechanism comprising:
2. The transmission device according to claim 1, further comprising: a transmission portion that is provided on one of the first rocker arm and the second rocker arm and selectively contacts the piston by sliding of the piston. Item 5. The variable valve operating structure according to any one of Items 4 to 5.

Images