JP2016075193A - Engine valve gear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To highly accurately switch valve timing according to an engine rotation number, to stabilize a motion characteristic related to the changeover of the valve timing, and to improve responsiveness.SOLUTION: An engine valve gear has a phase variable device 44 which relatively changes a phase of an intake cam 15 in a rotational direction with respect to a crankshaft. The phase variable device has a driven member 45, a guide member 46, a centrifugal weight 47 and an energization member 48. The guide member is relatively displaced with respect to the driven member by the action of an energization force of the energization member by the movement of the centrifugal weight by the action of a centrifugal force. A torsion spline 55 which connects an intake cam-side shaft part 31 of the camshaft 17 to the guide member 46 converts the relative displacement of the guide member in an axial direction with respect to the driven member 45 into the relative displacement of an intake cam-side shaft part 31 in a rotational direction with respect to the crankshaft, and relatively changes a phase of the intake cam 15 in the rotational direction with respect to the crankshaft.SELECTED DRAWING: Figure 9

Description

  The present invention relates to a valve operating apparatus for an engine that includes a phase variable device that changes the phase of a rotation direction of an intake cam or an exhaust cam with respect to a crankshaft and that can change valve timings of an intake valve and an exhaust valve.

  The valve gears for engines disclosed in Patent Documents 1 and 2 change the phase of the camshaft in the rotational direction with respect to the crankshaft according to the operating state of the engine, A camshaft phase varying device has been proposed as a valve timing varying device that changes the valve timing of an exhaust valve.

  In this camshaft phase varying device, a plurality of centrifugal weights are interposed between a follower member that can be displaced relative to the camshaft in the rotational direction and a guide member that is provided integrally with the camshaft. The guide groove is provided in each of a plurality of radially formed guide grooves on the opposing surfaces of the driven member and the guide member.

  Of these, for example, the guide groove of one of the driven members is inclined with respect to the radial direction of the driven member. Therefore, when the centrifugal weight moves in the guide grooves in the radial direction of the driven member and the guide member by the action of centrifugal force, the guide member rotates relative to the driven member, thereby rotating the camshaft relative to the crankshaft. The phase of the direction changes, and the valve timings of the intake valve and the exhaust valve are changed.

JP 2013-7293 A JP 2010-31855 A

  However, in order to change the valve timings of the intake valve and the exhaust valve with high accuracy according to the engine speed, each of the plurality of centrifugal weights needs to move simultaneously in each of the plurality of guide grooves. For this reason, high processing accuracy is required for each guide groove of the driven member and the guide member.

  The object of the present invention has been made in consideration of the above-mentioned circumstances. The valve timing can be switched with high accuracy in accordance with the engine speed, and the operation characteristics are stabilized and responsive with respect to the switching of the valve timing. An object of the present invention is to provide a valve operating apparatus for an engine that can improve performance.

  According to a first aspect of the present invention, there is provided a valve operating apparatus for an engine, comprising: a camshaft having a cam that is rotated by a crankshaft and that opens and closes a valve of the engine; and a rotational direction of the cam relative to the crankshaft. A valve operating device for an engine having a phase varying device for relatively changing a phase, wherein the phase varying device is transmitted with rotation of the crankshaft and is relatively displaceable in a rotational direction with respect to the camshaft. And a driven member that is not relatively displaceable in the axial direction, and is connected to the camshaft via a torsional engagement mechanism so as to be integrally rotatable, and is relatively displaceable in the axial direction and relative to the driven member in the rotational direction. An impossible guide member, a centrifugal weight disposed between the driven member and the guide member, and the driven member and the guide member in a direction approaching each other. And the guide member is relatively displaced in the axial direction with respect to the driven member under the action of the urging force of the urging member as the centrifugal weight is moved by the action of the centrifugal force. The torsional engagement mechanism converts a relative displacement in the axial direction of the guide member with respect to the driven member into a relative displacement in the rotational direction of the camshaft with respect to the crankshaft, and rotates the cam with respect to the crankshaft. The directional phase is relatively changed.

  According to a second aspect of the present invention, there is provided a valve operating apparatus for an engine, wherein the intake cam and the exhaust valve of the engine are rotated by a crankshaft and the intake cam and the exhaust valve are respectively opened and closed. And a camshaft provided with an exhaust cam, and a phase variable device that changes the phase of the rotation direction of the intake cam or the exhaust cam relative to the crankshaft, The camshaft has an intake cam side shaft portion provided with the intake cam and an exhaust cam side shaft portion provided with the exhaust cam, and these both shaft portions can be relatively displaced in the rotation direction. The phase varying device is configured such that the rotation of the crankshaft is transmitted and the driven portion is fixed to the exhaust cam side shaft portion or the intake cam side shaft portion. Are coupled to the intake cam side shaft portion or the exhaust cam side shaft portion via a torsional engagement mechanism so as to be integrally rotatable, and are relatively displaceable in the axial direction and not relatively displaceable in the rotational direction with respect to the driven member. A guide member; a centrifugal weight disposed between the driven member and the guide member; and a biasing member that biases the driven member and the guide member toward each other. When the centrifugal weight is moved by the action of the centrifugal force, the centrifugal weight is relatively displaced in the axial direction with respect to the driven member under the action of the urging force of the urging member, and the torsional engagement mechanism is provided with the guide for the driven member. The relative displacement in the axial direction of the member is converted into the relative displacement in the rotational direction of the intake cam side shaft portion or the exhaust cam side shaft portion with respect to the crankshaft, and the intake cam or the crankshaft Serial is characterized in that the rotational direction of the phase of the exhaust cam configured to relatively changing.

  According to the first aspect of the present invention, when the centrifugal weight is moved by the centrifugal force generated according to the engine speed, the guide member is not relatively displaced in the rotational direction with respect to the driven member, but in the axial direction. Therefore, the relative displacement of the guide member is facilitated. Since this guide member is connected to the camshaft via a torsional engagement mechanism, the axial displacement of the guide member relative to the driven member described above is caused by the torsional engagement mechanism to rotate the camshaft relative to the crankshaft. Thus, the phase in the rotational direction of the cam relative to the crankshaft changes relatively.

  Thus, the axial displacement of the guide member is facilitated and the camshaft is smoothly displaced relatively in the rotational direction, so that the valve timing can be switched with high accuracy according to the engine speed. Moreover, since the valve timing can be switched without using hydraulic oil, the operation characteristics regarding the switching of the valve timing are stabilized, and the responsiveness is also improved.

  According to the second aspect of the present invention, when the centrifugal weight is moved by the action of the centrifugal force generated according to the engine speed, the guide member is not relatively displaced in the rotational direction with respect to the driven member. Since the relative displacement is performed only in the direction, the relative displacement of the guide member is facilitated. Since the guide member is connected to the intake cam side shaft portion or the exhaust cam side shaft portion via the torsion engagement mechanism, the relative displacement in the axial direction of the guide member with respect to the driven member is caused by the torsion engagement mechanism. The phase in the rotational direction of the cam relative to the crankshaft changes relative to the relative displacement in the rotational direction of the intake cam side shaft or exhaust cam side shaft relative to the crankshaft.

  In this way, the relative displacement in the axial direction of the guide member is facilitated, and the intake cam side shaft portion or the exhaust cam side shaft portion is smoothly displaced relatively in the rotational direction. Therefore, the valve timing is increased according to the engine speed. It can be switched to accuracy. Moreover, since the valve timing can be switched without using hydraulic oil, the operation characteristics regarding the switching of the valve timing are stabilized, and the responsiveness is also improved.

1 is a cross-sectional view showing an SOHC type valve operating device to which a first embodiment of an engine valve operating device according to the present invention is applied, cut along a direction orthogonal to the axis of a camshaft, together with a cylinder head and the like. The perspective view shown with a cylinder head etc. except the intake valve, the exhaust valve, the rocker arm, etc. in the valve operating apparatus of FIG. The top view which shows a part of valve operating apparatus of FIG. 2, a cylinder head, etc. FIG. Sectional drawing which follows the IV-IV line of FIG. The perspective view which shows the camshaft and phase variable apparatus in FIGS. The perspective view which decomposes | disassembles and shows the camshaft and phase variable apparatus of FIG. The side view which decomposes | disassembles and shows the camshaft and phase variable apparatus of FIG. FIG. 6 is a side view showing the camshaft and the phase variable device of FIG. 5. Sectional drawing which follows the IX-IX line | wire of FIG. 8 and 9 show the exhaust cam side shaft portion and the driven member of the phase varying device, (A) is a perspective view showing the exhaust cam side shaft portion, and (B) is a front view showing the driven member. (A) is a front view which shows the driven member of FIG.8 and FIG.9, (B) is sectional drawing which follows the XIB-XIB line | wire of FIG. 11 (A). (A) is a front view which shows the guide member of FIG.8 and FIG.9, (B) is sectional drawing which follows the XIIB-XIIB line | wire of FIG. 12 (A). (A) is a cross-sectional view taken along line XIII-XIII in FIG. 12 (A), (B) is a cross-sectional view showing an enlarged part of FIG. 13 (A), and (C) is a part of FIG. 13 (B). Enlarged view. Operation | movement explanatory drawing which shows the position of the centrifugal weight in the engine low rotation speed area in the phase variable apparatus of FIG.8 and FIG.9. Operation | movement explanatory drawing which shows the position of the centrifugal weight in the engine high rotation area in the phase variable apparatus of FIG.8 and FIG.9. Sectional drawing which shows a part of DOHC type valve gear to which 2nd Embodiment in the valve gear of the engine which concerns on this invention was applied.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
[A] First embodiment (FIGS. 1 to 15)
FIG. 1 is a cross-sectional view showing an SOHC type valve operating apparatus to which a first embodiment of an engine valve operating apparatus according to the present invention is applied, cut along a direction perpendicular to the axis of a camshaft, together with a cylinder head and the like. It is. FIG. 2 is a perspective view showing a cylinder head and the like excluding an intake valve, an exhaust valve, a rocker arm, and the like in the valve operating device of FIG. Further, FIG. 3 is a plan view showing a part of the valve operating device of FIG. 2, a cylinder head and the like.

  A four-cycle single-cylinder engine 10 shown in FIG. 1 is equipped with an SOHC (single overhead camshaft) type valve gear 12 in a cylinder head 11 joined to a cylinder block 1. The valve operating device 12 includes an intake valve 13 and an exhaust valve 14, respectively, a camshaft 17 provided with an intake cam 15 and an exhaust cam 16, and an intake rocker arm 18 and an exhaust rocker arm 19 respectively. And a phase varying device 44 (FIGS. 2 and 3) described later.

  A cam driven sprocket 20 shown in FIGS. 2 and 3 is formed on a driven member 45 (described later) of the phase varying device 44 provided on the camshaft 17. The cam driven sprocket 20 is operatively connected to a cam drive sprocket (not shown) provided on the crankshaft 5 (FIG. 1) via a cam chain (not shown). Thereby, rotation of the crankshaft 5 is transmitted to the camshaft 17 via the cam chain, and the camshaft 17 rotates. The camshaft 17 is provided with an intake cam 15 and an exhaust cam 16 side by side in the axial direction. For example, the exhaust cam 16 is positioned on the cam driven sprocket 20 side.

  Here, the cylinder block 1 shown in FIG. 1 is formed with a cylinder bore 3 in which the piston 2 reciprocates in a sliding state. The reciprocating motion of the piston 2 is transmitted to the crankshaft 5 through the connecting rod 4 and converted into rotational motion.

  Each of the intake rocker arm 18 and the exhaust rocker arm 19 is pivotally supported by a rocker shaft 24, and is provided with a roller 22 at one end and an adjusting screw 23 at the other end. The intake rocker arm 18 is provided so as to be able to roll when the roller 22 contacts the intake cam 15, and the adjustment screw 23 contacts the intake valve 13. Further, the exhaust rocker arm 19 is provided so as to be able to roll when the roller 22 contacts the exhaust cam 16, and the adjustment screw 23 contacts the exhaust valve 14.

  Therefore, when the intake cam 15 and the exhaust cam 16 are rotated by the rotation of the camshaft 17, the intake rocker arm 18 swings due to the roller 22 of the intake rocker arm 18 rolling along the cam profile of the intake cam 15. The adjusting screw 23 of the rocker arm 18 drives the intake valve 17 to open and close. At the same time, the roller 22 of the exhaust rocker arm 19 rolls along the cam profile of the exhaust cam 16 to swing the exhaust rocker arm 19, and the adjusting screw 23 of the exhaust rocker arm 19 drives the exhaust valve 14 to open and close.

  In FIG. 1, reference numeral 25 denotes an adjustment nut, and reference numeral 26 denotes a valve spring. Reference numeral 21 denotes a stem guide that is attached to the cylinder head 11 and guides the movement of the stems of the exhaust valve 13 and the intake valve 14.

  As shown in FIG. 4, the camshaft 17 of the valve gear 12 configured as described above is provided with a first ball bearing 27 at one end on the cam driven sprocket 20 side and a second at the other end. A ball bearing 28 is provided. The first ball bearing 27 and the second ball bearing 28 are supported by a camshaft housing 29 provided on the upper portion of the cylinder head 11, thereby supporting the camshaft 17 rotatably.

  4 and 5, the camshaft 17 provided with the intake cam 15 and the exhaust cam 16 has an intake cam side shaft portion integrally formed with the intake cam 15, as shown in FIGS. 31 and an exhaust cam side shaft portion 32 in which the exhaust cam 16 is integrally formed. As shown in FIGS. 8 and 9, the shaft portion 31A of the intake cam side shaft portion 31 is inserted into the exhaust cam side shaft portion 32, so that the exhaust cam side shaft portion 32 is coaxial with the outside of the shaft portion 31A. Arranged in a state. In this manner, the intake cam side shaft portion 31 and the exhaust cam side shaft portion 32 are configured to be relatively displaceable in the rotation direction.

  However, relative displacement in the rotational direction between the intake cam side shaft portion 31 and the exhaust cam side shaft portion 32 is allowed only in a predetermined range described later. That is, as shown in FIGS. 5 to 8, the intake cam side shaft portion 31 is integrally formed with the shaft portion 31 </ b> A and a cam forming portion 31 </ b> B in which the intake cam 15 is formed with a diameter larger than that of the shaft portion 31 </ b> A. Has been. A locking pin 33 is provided on the cam forming portion 31B of the intake cam side shaft portion 31 so as to project parallel to the axis O of the intake cam side shaft portion 31 toward the shaft portion 31A. Further, the exhaust cam side shaft portion 32 has a locking groove 34 on the side surface of the exhaust cam 16 for locking the locking pin 33 in the assembled state of the intake cam side shaft portion 31 and the exhaust cam side shaft portion 32. Is formed.

  When the intake cam side shaft portion 31 arranged coaxially in the exhaust cam side shaft portion 32 is displaced relative to the exhaust cam side shaft portion 32 in the rotational direction, the locking pin 33 of the intake cam side shaft portion 31 is By contacting both end surfaces 35 of the locking groove 34 of the exhaust cam side shaft portion 32, the relative displacement in the rotational direction of the intake cam side shaft portion 31 relative to the exhaust cam side shaft portion 32 is restricted.

  On the other hand, as shown in FIG. 3, a plurality of, for example, four bolt insertion holes 36 are formed in the camshaft housing 29 so as to penetrate the camshaft housing 29 and the cylinder head 11. By inserting a head tightening bolt (not shown) into the bolt insertion hole 36, the cylinder head 11 with the camshaft housing 29 integrally formed is fastened and fixed to a crankcase (not shown) together with the cylinder block 1.

  As shown in FIGS. 3 and 4, the camshaft housing 29 is formed with an oil introduction groove 37 that communicates with at least one of the bolt insertion holes 36. As shown in FIGS. 4 and 9, the intake cam side shaft portion 31 is formed with a main oil groove 38 extending along the axis O and a sub oil groove 39 communicating with the main oil groove 38. The intake cam side shaft portion 31 is formed so as to extend in the radial direction. The main oil groove 38 communicates with the oil introduction groove 37. Further, the discharge port 40 of the sub oil groove 39 communicates with an annular groove 42 formed on the outer peripheral surface of the shaft portion 31 </ b> A of the intake cam side shaft portion 31, that is, the sliding contact surface 41 with the exhaust cam side shaft portion 32.

  Therefore, as shown in FIGS. 3 and 4, the lubricating oil that has risen in the bolt insertion hole 36 is supplied to the main oil groove 38 of the intake cam side shaft portion 31 through the oil introduction groove 37 of the camshaft housing 29, Further, the intake cam side shaft portion 31 is supplied from the sub oil groove 39 into the annular groove 42 to lubricate the relatively rotatable intake cam side shaft portion 31 and the exhaust cam side shaft portion 32.

  Incidentally, as shown in FIGS. 4, 5, 8, and 9, the camshaft 17 is sequentially provided with an intake cam 15, an exhaust cam 16, and a phase varying device 44. The phase varying device 44 relatively changes the phase in the rotational direction of the intake cam 15 or the exhaust cam 16 (in the present embodiment, the intake cam 15) with respect to the crankshaft 5, and includes a driven member 45, a guide member 46, A centrifugal weight 47, an urging member 48, and a circlip 49 are included.

  In this embodiment, the exhaust cam 16 is rotationally driven with the same phase in the rotational direction as the crankshaft 5 to open and close the exhaust valve 14. On the other hand, the intake cam 15 is rotationally driven by the phase varying device 44 in the same or different phase in the rotational direction with respect to the crankshaft 5 to open and close the intake valve 13. By this phase varying device 44, the valve timing of the intake valve 13 is controlled in accordance with the operating state of the engine 10, and the valve overlap in which the opening timing of the intake valve 13 and the opening timing of the exhaust valve 14 overlap is adjusted.

  For example, the phase varying device 44 sets the valve overlap of the intake valve 13 and the exhaust valve 14 to be small in the high rotation range of the engine 10 to prevent intake air blow-through, improve output and fuel consumption, and Reduce emissions of hazardous substances. Further, the phase varying device 44 sets the valve overlap of the intake valve 13 and the exhaust valve 14 to be large in the low rotation range of the engine 10 to increase the intake efficiency by utilizing the inertia of the intake and improve the torque of the engine 10. Let

  As shown in FIGS. 9 and 11, the driven member 45 has a cam driven sprocket 20 formed on the outer circumferential surface thereof, and is driven by the rotation of the crankshaft 5 transmitted through the cam chain. The phase in the rotation direction is constant (that is, the same). Further, as shown in FIG. 12, a fitting groove 53 is formed on the inner peripheral surface of the driven member 45, and a fitting convex portion 54 is formed at one end of the exhaust cam side shaft portion 32. The driven member 45 is fixed to the exhaust cam side shaft portion 32 by fitting the cam groove 53 and the fitting convex portion 54 together.

  As shown in FIGS. 4, 6, 7 and 9, the guide member 46 is connected to the intake cam side shaft via a torsion spline 55 (a torsion spline key 55A and a torsion spline groove 55B) as a torsion engagement mechanism. It is connected to the part 31 so as to be integrally rotatable. In other words, the shaft portion 31A of the intake cam side shaft portion 31 has a twist angle θ (FIG. 7) on one side in the circumferential direction with respect to the axis O of the intake cam side shaft portion 31 in a side view of the intake cam side shaft portion 31. A twisted spline key 55A that is twisted only by one is formed integrally. Further, as shown in FIGS. 12A and 13A, a torsion spline groove 55B that meshes with the torsion spline key 55A is formed on the inner periphery of the guide member 46.

  The torsional spline groove 55B of the guide member 46 is engaged with the torsional spline key 55A of the intake cam side shaft portion 31 so that the guide member 46 is connected to the intake cam side shaft portion 31 so as to be integrally rotatable and is also connected to the driven member 45. On the other hand, it is configured to be relatively displaceable in the axial direction (the direction of the axis O of the intake cam side shaft portion 31). The relative displacement in the axial direction of the guide member 46 with respect to the driven member 45 is converted into the relative displacement in the rotational direction of the intake cam side shaft portion 31 with respect to the crankshaft 5 by the action of the torsion spline 55.

  The centrifugal weight 47 is formed in a cylindrical shape as shown in FIGS. 6, 7, and 9, and is held one by one between a plurality of guide grooves 51 and 52 (described later) of the driven member 45 and the guide member 46. A plurality of them are provided to transmit the rotation of the driven member 45 to the guide member 46. Further, the biasing member 48 applies a biasing force to bias at least one of the driven member 45 and the guide member 46 (the guide member 46 in the present embodiment) in the direction in which the driven member 45 and the guide member 46 approach each other. give. Further, the circlip 49 is attached to the shaft end of the shaft portion 31 </ b> A of the intake cam side shaft portion 31 and holds the biasing member 48 via the washer 50.

  More specifically, the driven member 45 is formed with a plurality of radial guide grooves 51 on the surface facing the guide member 46 in the inner portion of the cam driven sprocket 20 as shown in FIGS. 9 and 11. The guide groove 51 guides a cylindrical centrifugal weight 47, and is formed in a flat groove shape having a rectangular cross section as shown in FIG. The guide groove 51 is formed to have a constant groove depth and to extend linearly along the radial direction of the driven member 45.

  As shown in FIGS. 9, 12, and 13, the guide member 46 has a plurality of radial guide grooves 52 formed on the surface facing the driven member 45. The guide groove 52 guides the centrifugal weight 47, and is formed in a flat groove shape having a rectangular cross section as shown in FIG. Further, the guide groove 52 is formed to extend linearly along the radial direction of the guide member 46. Both the guide groove 51 of the driven member 45 that holds the centrifugal weight 47 and the guide groove 52 of the guide member 46 are linearly formed along the respective radial directions. It is configured so that it cannot be displaced relative to the rotation direction.

  Further, as shown in FIG. 13 in particular, the guide groove 52 of the guide member 46 is provided with a gradient in which the groove depth becomes shallower toward the outer side in the radial direction of the guide member 46. It is comprised so that it may become steep as it goes to radial direction outward. That is, the gradient of the groove depth of the guide groove 52 is set to the gradient α on the radially inner side of the guide member 46 and the gradient β (β> α) on the outer side. The gradient α and the gradient β are configured to change smoothly near a certain point (point X in FIG. 13B) at the bottom of the guide groove 52. Due to the gradients α and β of the guide groove 52, the guide groove 51 of the driven member 45 and the guide groove 52 of the guide member 46 are configured such that the groove bottoms approach each other as they go radially outward.

  Specifically, in the guide groove 52 of the guide member 46, the radially inner plane of the gradient α smoothly continues to the radially outer plane of the gradient β via a curved surface having a required curvature P. As shown in FIG. 13C, a curved surface passing through a certain point X is formed with a required curvature P, and both sides (radially inner side and radially outer side) of the curved surface are configured as a plane of gradient α and gradient β. Yes.

  The guide groove 51 of the driven member 45 is provided with a gradient in which the groove depth becomes shallower toward the radial direction of the driven member 45, and this gradient becomes steeper as it goes outward in the radial direction of the driven member 45. Further, the guide groove 52 of the guide member 46 may be formed with a constant groove depth.

  The centrifugal weight 47 shown in FIGS. 4 and 9 is made of a material having a large specific gravity such as steel or tungsten. The urging member 48 is a disc spring in the present embodiment, but may be a corrugated spring, a spiral spring (bamboo spring), or the like. Further, the circlip 49 is coupled to the shaft end of the shaft portion 31 </ b> A of the intake cam side shaft portion 31, supports the biasing member 48 via the washer 50, and holds the biasing member 48 between the guide member 46. To do. Thereby, the urging force of the urging member 48 is applied to the guide member 46.

  In the phase varying device 44 configured in this way, as shown in FIG. 9, centrifugal force acts on the centrifugal weight 47, and the centrifugal weight 47 is guided by the guide grooves 51 and 52 of the driven member 45 and the guide member 46. When moving inward radially outward, the guide member 46 moves away from the driven member 45 along the direction of the axis O of the intake cam side shaft portion 31 of the camshaft 17 against the biasing force of the biasing member 48. Move in the direction you want. Further, when the centrifugal force acting on the centrifugal weight 47 decreases and the centrifugal weight 47 moves radially inward in the guide grooves 51 and 52 of the driven member 45 and the guide member 46, the guide member 46 is attached. Due to the urging force of the urging member 48, the cam member 17 moves in the direction approaching the driven member 45 along the direction of the axis O of the intake cam side shaft portion 31 of the camshaft 17.

  The torsion spline 55 moves in a direction in which the guide member 46 moves away from or approaches the driven member 45, and the intake cam side shaft portion 31 moves relative to the exhaust cam side shaft portion 32 and the driven member 45, that is, relative to the crankshaft 5. Convert to displacement in the rotating direction. As a result, the rotational direction phase of the intake cam 15 relative to the crankshaft 5 changes relatively, and the intake cam 15 changes the opening timing of the intake valve 13.

Next, the operation will be described.
As shown in FIG. 14, when the engine 10 is in the low rotation range, the centrifugal force acting on the centrifugal weight 47 is small, and this centrifugal weight 47 is applied to the gradient α of the guide groove 52 of the guide member 46 and the biasing member 48. The action of the force remains at the initial position of the radially inner ends of the guide grooves 51 and 52. For this reason, the intake cam side shaft portion 31 of the camshaft 17 has the same rotational phase as the cam driven sprocket 20 (that is, the crankshaft 5), and the intake cam 15 formed integrally with the intake cam side shaft portion 31. Drives the intake valve 13 at the phase during assembly. As a result, the intake valve 13 and the exhaust valve 14 have a valve timing for low and medium speed with a large valve overlap, and the medium speed torque is improved.

  As shown in FIG. 15, when the engine 10 reaches a high rotation range, the centrifugal force acting on the centrifugal weight 47 increases, and the centrifugal weight 47 is in the guide groove 51 of the driven member 45 and the guide groove 52 of the guide member 46. Is moved radially outward. As a result, the guide member 46 moves outward along the axis O of the intake cam side shaft portion 31 of the camshaft 17 against the biasing force of the biasing member 48 by the action of the gradients α and β of the guide groove 52. Move to the side (arrow A direction).

  At this time, since the guide member 46 and the intake cam side shaft portion 31 of the camshaft 17 are connected via the torsion spline 55, the intake cam side shaft portion 31 includes the exhaust cam side shaft portion 32 and the driven member 45 ( That is, relative to the crankshaft 5), the torsion spline 55 rotates relative to the direction of the arrow B in FIGS. 15B and 15C by the torsion angle θ of the torsion spline key 55A. Note that the direction opposite to the arrow B direction in FIGS. 15B and 15C is the direction of rotation of the camshaft 17 by the driving force of the crankshaft 5.

  As a result, the intake cam side shaft portion 31 of the camshaft 17 changes the rotation direction phase with respect to the crankshaft 5 in the direction opposite to the rotation direction R of the camshaft 17 (retarded side). Therefore, the intake cam 15 formed integrally with the intake cam side shaft portion 31 drives the intake valve 13 with a phase changed to the retard side from the phase at the time of assembly. As a result, the intake valve 13 and the exhaust valve 14 have a high valve timing with a small valve overlap, the output of the engine 10 and the fuel efficiency are improved, and the emission of harmful substances is suppressed.

  When the rotational speed of the engine 10 decreases, the centrifugal force acting on the centrifugal weight 47 decreases, so that the urging force by the urging member 48 is superior to the force that moves the guide member 46 in the direction of arrow A by the centrifugal force. The guide member 46 is moved to the driven member 45 side by the action of the urging force of the urging member 48, the centrifugal weight 47 is moved inward in the radial direction of the guide grooves 51 and 52, and the guide member 46 and the centrifugal weight 47 are eventually shown in FIG. 14 returns to the original position.

  As the centrifugal weight 47 returns to the original position, the guide member 46 moves in the axial direction in a direction approaching the driven member 45, so that the intake cam side shaft portion 31 of the camshaft 17 is moved by the action of the torsion spline 55. The intake cam 15 rotates relative to the exhaust cam side shaft portion 32 and the driven member 45 (that is, the crankshaft 5) in the advance side (the direction opposite to the arrow B in FIGS. 15B and 15C). The phase is changed to the advance side with respect to the crankshaft 5. As a result, the intake valve 13 and the exhaust valve 14 have a valve timing for low and medium speed with large valve overlap, and the medium speed torque is improved as described above.

With the configuration as described above, the following effects (1) to (4) are achieved according to the first embodiment.
(1) As shown in FIGS. 4 and 9, when the centrifugal weight 47 moves between the guide groove 51 of the driven member 45 and the guide groove 52 of the guide member 46 due to the centrifugal force generated according to the engine speed. The guide member 46 is not relatively displaced in the rotational direction with respect to the driven member 45, but is relatively displaced in the axial direction. For this reason, the frictional force decreases between the centrifugal weight 47 and the guide grooves 51 and 52, and the movement of the centrifugal weight 47 is facilitated, and the plurality of centrifugal weights 47 are reliably moved simultaneously. The relative displacement in the axial direction of the member 46 is also facilitated.

  Since the guide member 46 is connected to the intake cam side shaft portion 31 of the camshaft 17 via the torsion spline 55, the relative displacement in the axial direction of the guide member 46 with respect to the driven member 45 is the torsion spline. 55 is converted into a relative displacement in the rotation direction of the intake cam side shaft portion 31 with respect to the driven member 45 and the exhaust cam side shaft portion 32 (that is, the crankshaft 5), and the phase in the rotation direction of the intake cam 15 with respect to the crankshaft 5 is changed. It changes relatively.

  In this way, the axial displacement of the guide member 46 with respect to the driven member 45 is facilitated, and the torsion spline 55 causes the intake cam side shaft portion 31 provided with the intake cam 15 to rotate with respect to the crankshaft 5. Therefore, the valve timings of the intake valve 13 and the exhaust valve 14 can be switched with high accuracy according to the engine speed. Moreover, since the valve timing can be switched without using hydraulic oil, the operation characteristics regarding the switching of the valve timing are stabilized, and the responsiveness is also improved.

  (2) As shown in FIGS. 9, 11, and 12, the centrifugal weight 47 is formed in a cylindrical shape, and the guide grooves 51 and 52 of the driven member 45 and the guide member 46 correspond to the cylindrical shape of the centrifugal weight 47. Thus, it is formed in a flat groove shape having a rectangular cross section. For this reason, the processing of the guide grooves 51 and 52 is facilitated, the cost can be reduced, and the processing accuracy of the guide grooves 51 and 52 can be improved.

  (3) As shown in FIGS. 7 and 9, the relative displacement in the axial direction of the guide member 46 with respect to the driven member 45 is changed to the relative displacement in the rotational direction of the intake cam side shaft portion 31 with respect to the crankshaft 5. By converting, the phase of the rotation direction of the intake cam 15 with respect to the crankshaft 5 changes relatively. Therefore, the degree of relative displacement in the rotational direction of the intake cam 15 with respect to the crankshaft 5 can be adjusted by changing the twist angle θ of the torsion spline key 55A of the torsion spline 55. As a result, the intake valve 13 and the exhaust valve 14 can be adjusted. The degree of change of valve timing can be adjusted.

  (4) In the phase varying device 44, the centrifugal weight 47 moves between the guide grooves 51 and 52 of the driven member 45 and the guide member 46 by the action of centrifugal force, so that the guide member 46 is biased by the biasing member 48. The torsional spline 55 is displaced in the axial direction of the guide member 46 with respect to the driven member 45 and the exhaust cam side shaft 32 under the action of the urging force. The phase of the rotation direction of the intake cam 15 provided on the intake cam side shaft portion 31 with respect to the crankshaft 5 is changed relative to the displacement in the rotation direction of the intake cam side shaft portion 31 with respect to the exhaust cam side shaft portion 32. Let Therefore, also in the SOHC type valve gear 12 including one camshaft 17 provided with the intake cam 15 and the exhaust cam 16, the intake valve 13 and the exhaust valve are operated during the operation of the intake cam 15 and the exhaust cam 16. 14 valve timings can be changed reliably.

[B] Second Embodiment (FIG. 16)
FIG. 16 is a cross-sectional view showing a part of a DOHC type valve gear to which the second embodiment of the valve gear for an engine according to the present invention is applied. In the second embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description is simplified or omitted.

  The valve operating device 60 in the second embodiment is different from the first embodiment in that a DOHC (double overhead camshaft) is provided with an intake cam on one camshaft and an exhaust cam on the other camshaft. The phase variable device 44 is applied to the valve operating device 60.

  That is, the phase varying device 44 is applied to the intake cam shaft 63 integrally formed with the intake cam 62 that drives the intake valve 61 to open and close. Specifically, the phase varying device 44 is transmitted with the rotation of the crankshaft 5 and can be relatively displaced in the rotational direction with respect to the intake camshaft 63 but not in the axial direction, and the intake camshaft. 63, a guide member 46 that is connected to the drive member 45 via a torsion spline 55 so as to be integrally rotatable, can be relatively displaced in the axial direction with respect to the driven member 45, and cannot be relatively displaced in the rotational direction, and the guide groove 51 and guide of the driven member 45 A cylindrical centrifugal weight 47 disposed between the guide grooves 52 of the member 46 and an urging member 48 that urges the driven member 45 and the guide member 46 toward each other are configured.

  The guide member 46 is moved under the action of the urging force of the urging member 48 by the centrifugal weight 47 moving between the guide grooves 51 and 52 in the radial direction of the driven member 45 and the guide member 46 by the action of the centrifugal force. Thus, relative displacement in the axial direction with respect to the driven member 45 is achieved. The torsion spline 55 (the torsion spline key 55A and the torsion spline groove 55B) converts the relative displacement in the axial direction of the guide member 46 with respect to the driven member 45 into the relative displacement in the rotation direction of the intake camshaft 63 with respect to the crankshaft 5. Thereby, the phase of the rotation direction of the intake cam 62 with respect to the crankshaft 5 changes relatively, and the valve timing of the intake valve and the exhaust valve is changed.

  Also in the second embodiment, the guide groove 51 of the driven member 45 is formed so as to extend linearly in the radial direction of the driven member 45 and the guide member 46, similarly to the guide groove 52 of the guide member 46. Since it is formed in a flat groove shape having a rectangular cross section corresponding to the cylindrical centrifugal weight 47, the same effects as the effects (1) to (3) of the first embodiment are obtained.

  As mentioned above, although embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention.

  For example, in the first embodiment, reference numeral 31 is an exhaust cam side shaft portion integrally provided with an exhaust cam, reference number 32 is an intake cam side shaft portion integrally provided with an intake cam, and an intake cam side shaft is provided. Is fixed to the driven member 45, and the exhaust cam side shaft portion is connected to the guide member 46 via the torsion spline 55 so as to be integrally rotatable, so that the phase varying device 44 is, for example, in the high rotation range of the engine 10. The valve timing of the intake valve 13 and the exhaust valve 14 may be changed to a high-speed valve timing with a small valve overlap by changing the phase of the rotation direction of the exhaust cam relative to the crankshaft 5 to the advance side. Good.

  In the second embodiment, the phase varying device 44 is applied to the exhaust camshaft instead of the intake camshaft 63, and the phase of the exhaust camshaft in the rotational direction of the engine 10 with respect to the crankshaft 5 is high. The valve timing of the intake valve 13 and the exhaust valve 14 may be changed to a high-speed valve timing with a small valve overlap.

5 crankshaft 10 engine 12 valve operating device 13 intake valve 14 exhaust valve 15 intake cam 16 exhaust cam 17 camshaft 31 intake cam side shaft portion 32 exhaust cam side shaft portion 44 phase varying device 45 driven member 46 guide member 47 centrifugal weight 48 Biasing member 49 Circlip 51, 52 Guide groove 55 Torsion spline (torsion engagement mechanism)
55A Torsion Spline Key 55B Torsion Spline Groove 60 Valve Operating Device 62 Intake Cam 63 Intake Cam Shaft θ Torsion Angle

Claims (4)

A camshaft having a cam that rotates by a crankshaft and opens and closes an engine valve;
A variable valve device for changing the phase of the cam in the rotational direction relative to the crankshaft,
The phase varying device includes:
A driven member to which the rotation of the crankshaft is transmitted and is relatively displaceable in the rotational direction with respect to the camshaft and is not relatively displaceable in the axial direction;
A guide member coupled to the camshaft via a torsional engagement mechanism so as to be integrally rotatable, and capable of relative displacement in the axial direction with respect to the driven member, and relative displacement in the rotational direction;
A centrifugal weight disposed between the driven member and the guide member;
An urging member that urges the driven member and the guide member toward each other;
The guide member is relatively displaced in the axial direction with respect to the driven member under the action of the urging force of the urging member, as the centrifugal weight is moved by the action of the centrifugal force,
The torsional engagement mechanism converts a relative displacement in the axial direction of the guide member with respect to the driven member into a relative displacement in the rotational direction of the camshaft with respect to the crankshaft, so that the rotational direction of the cam with respect to the crankshaft is changed. A valve operating apparatus for an engine, characterized in that the phase is relatively changed. Engine intake and exhaust valves,
A camshaft provided with an intake cam and an exhaust cam that are rotated by a crankshaft and that respectively open and close the intake valve and the exhaust valve;
A phase varying device that relatively changes a phase of the intake cam or the exhaust cam in the rotational direction with respect to the crankshaft;
The camshaft has an intake cam side shaft portion provided with the intake cam and an exhaust cam side shaft portion provided with the exhaust cam, and both shaft portions can be relatively displaced in the rotation direction. Composed of
The phase varying device includes:
The rotation of the crankshaft is transmitted, and a driven member provided fixed to the exhaust cam side shaft portion or the intake cam side shaft portion;
A guide member that is connected to the intake cam side shaft portion or the exhaust cam side shaft portion via a torsional engagement mechanism so as to be integrally rotatable, and is relatively displaceable in the axial direction and not relatively displaceable in the rotational direction with respect to the driven member. When,
A centrifugal weight disposed between the driven member and the guide member;
An urging member that urges the driven member and the guide member toward each other;
The guide member is relatively displaced in the axial direction with respect to the driven member under the action of the urging force of the urging member, as the centrifugal weight is moved by the action of the centrifugal force,
The torsional engagement mechanism converts the relative displacement in the axial direction of the guide member with respect to the driven member into relative displacement in the rotational direction of the intake cam side shaft portion or the exhaust cam side shaft portion with respect to the crankshaft, A valve operating apparatus for an engine, characterized in that a phase in a rotational direction of the intake cam or the exhaust cam with respect to the crankshaft is relatively changed. The centrifugal weight is formed in a cylindrical shape, and the guide groove formed on the mutually facing surfaces of the driven member and the guide member to guide the movement of the centrifugal weight is formed in a rectangular cross section corresponding to the shape of the centrifugal weight. The valve gear for an engine according to claim 1 or 2, wherein The follower member and the guide member have a plurality of guide grooves that guide movement of each of the plurality of centrifugal weights on surfaces facing each other, and extend radially in a radial direction, and are radially formed.
The guide groove of one of the driven member and the guide member is formed with a constant groove depth, and the other guide groove is formed with a gradient in which the groove depth becomes shallower toward the outside in the radial direction. The valve operating apparatus for an engine according to any one of claims 1 to 3, wherein

Images