JP4552707B2 - Variable valve operating device for internal combustion engine - Google Patents

Description

  The present invention relates to a variable valve operating apparatus for an internal combustion engine that varies the drive phase and lift amount of an intake valve or an exhaust valve.

  The engine, which is an internal combustion engine mounted on automobiles, is equipped with a variable valve gear for reasons such as engine exhaust gas countermeasures and fuel efficiency reduction, and drives intake valves and exhaust valves according to the driving conditions of the automobile. Changing the opening / closing timing and the lift amount, which are phases, is performed.

  Such a variable valve device has a swing cam surface in which the displacement of the base section and the lift section on the cam surface of the drive cam integrally formed with the camshaft is once connected to the base section and the lift section. There is one that replaces the displacement of the swing cam in the swing cam moving direction. Many of the rocking cams used in such variable valve gears are designed to shift the rocking area of the rocking cam by driving the fulcrum moving mechanism in the rocker arm mechanism, so that An area where the rocker arm roller on the rocker arm side faces is variably adjusted.

  In this case, according to the driving state of the vehicle, the opening / closing timing or lift which is the drive mode of the intake valve or exhaust valve by shifting the ratio of the lift section where the rocker arm roller faces the base section, the lift section, and the rocking cam surface. The amount is adjusted.

  As an example, the rocker arm mechanism includes a variable pivot member that is switched and changed depending on the drive source, an intermediate arm that pivots on the variable pivot member and pivots on the drive cam, and a pivot point on the support shaft. Some have a swing cam that swings by receiving a pressing force from an adjacent intermediate arm that is pivotally supported at the input point and presses the rocker arm roller on the rocker arm side by the swing cam surface of the swing end. By the switching operation of the variable pivot member in the rocker arm mechanism, the driving cam facing roller of the intermediate arm moves in the rotation direction of the driving cam, thereby displacing the lift section of the intermediate arm. In other words, the input point of the opening / closing operation force for the swing cam of the intermediate arm changes, and in conjunction with this, the swing area where the rocker arm roller on the rocker arm side faces the lift section on the swing cam surface and transmits the opening / closing operation force. Changes. In this manner, the rocker arm mechanism adjusts the opening / closing timing and the lift amount, which are the drive modes of the intake valve or the exhaust valve linked to the rocker arm, by moving the driving cam facing roller in the rotation direction of the driving cam.

  An example of a displacement diagram showing the operation amount of the driven member driven by the drive cam of such a rocker arm mechanism is shown in FIG.

  Here, a solid line CH1 shows a diagram showing the amount of operation of the driven member when the driving cam opposing roller of the intermediate arm is shifted to the retard side that is the rotational direction of the driving cam by operating the variable pivot member of the rocker arm mechanism. Indicated. Further, the operation amount of the driven member when the driving cam facing roller of the intermediate arm is shifted to the advance angle side (left side in FIG. 9) opposite to the rotation direction of the drive cam with respect to CH1 indicated by the solid line is R0. The diagram shown is indicated by the dashed line CH2. In response to the operation of such a variable pivot member, the drive cam opposing roller on the intermediate arm side moves forward and backward in the rotation direction of the drive cam, so that the maximum position of the operation amount can be shifted by R0, and further, the intermediate arm swings. By forming the input point that contacts the moving cam to change, the swinging range of the swinging cam is changed so that the predetermined cam height of the driving cam does not act on the intake or exhaust valve. Alternatively, the amount acting on the exhaust valve lift height difference can be reduced to h2. Therefore, the lift amount displacement areas E1 and E2 of the intake valve or the exhaust valve interlocked with the rocker arm are shifted, and increase and decrease changes of the amounts h1 and h2 acting on the lift start point e1 and the lift end point e2 and the lift height occur.

  Patent Document 1 discloses an example of a variable valve operating device in which the ratio of the rocker arm roller on the rocker arm side to the base section and the lift section on the rocking cam surface of the rocking cam is shifted.

JP 2003-239712 A

  In general, regarding the lift of the intake valve or exhaust valve, in order to reduce the impact at the start of the seating or lift when the valve is closed, the drive cam is set so that the seating or the lift starts when the lift speed becomes substantially constant. The cam surface is set. However, as described in Patent Document 1, when a plurality of cams of a drive cam and a swing cam are used, the lift amount (also referred to as a valve lift amount) of the intake valve or the exhaust valve is determined by the combination of these cams. In addition, it is difficult to design the cam so that the valve lift speed becomes constant at the lift start timing, the impact on the intake valve or the exhaust valve is large, and there are problems in terms of sound and durability when the valve is driven.

Further, as is apparent from the operation amount displacement diagram shown in FIG. 9, the change in the crank angle direction of the change area ea of the lift start point e1 and the change area eb of the lift end point e2 due to the difference in the advance amount R0 and the cam shape. Each width varies. Here, the width eb of the change area of the lift end point e2 corresponds to the control width of the valve opening / closing timing by the rocker arm mechanism, and the valve closing control becomes easier as the width eb of the change area of the lift end point e2 increases. The variable responsiveness of the valve closing timing increases. In particular, in the case of an intake valve, the output control by greatly varying the valve closing timing related to the charging efficiency is facilitated, so that it is possible to further increase the width eb of the change range of the lift end point e2. This is presumed to be effective in controlling the closing of the exhaust valve. In this case, it has been difficult to design the cam so that the valve lift speed becomes constant at the time of seating and lift start.
It is an object of the present invention to provide a variable valve operating apparatus for an internal combustion engine that can reduce the impact of the seating of the valve and the start of the lift and can improve the durability with low noise when the lift of the intake valve or the exhaust valve is varied. And its purpose.

In order to achieve the above-mentioned object, the internal combustion engine according to the present invention is swung by receiving a camshaft rotatably provided, a drive cam integrally formed with the camshaft, and an opening / closing operation force from the drive cam. in the variable valve device for an internal combustion engine having a rocker arm mechanism comprising a swing cam surface to convey the opening and closing operation force to the intake valve or exhaust valve of an internal combustion engine Te, the rocker arm mechanism changes the cam lift period experienced by the drive cam Thus, the valve lift is performed so as to change the opening / closing timing and lift amount of the intake valve or exhaust valve in accordance with the operating state of the internal combustion engine, and the drive cam is continuously changed at least with the change of the cam lift period or and wherein the cam acceleration of the valve seating section of the drive cam corresponding to change region closed preventor timing of the exhaust valve is set to be substantially constant To have. The valve seating section is a section formed so that the operating speed of the member driven by the rotation of the camshaft is substantially constant.

  The present invention is characterized in that the down section of the cam surface of the drive cam is formed longer than the up section so that the change area at the valve closing time becomes larger than the change area at the lift valve opening time in the cam lift period.

In the variable valve operating apparatus according to the present invention, the rocker arm mechanism drives the intake valve or the exhaust valve that rotates around the fulcrum position and contacts the swing cam surface when the pivoted rocker arm roller receives a pressing force. A first arm, and a fulcrum end that receives a switching operation force that displaces the lift period forward and backward in the rotational direction of the drive cam by a predetermined amount away from the pivot support and a pivot that pivotally supports the drive cam facing roller that contacts the drive cam A fulcrum moving mechanism for displacing a fulcrum member engaged with a fulcrum end of the second arm by receiving a switching operation force from a drive source in the forward and backward directions of the drive cam;
A swing that can apply an opening / closing operation force to the rocker arm roller at the swing end of a swing extension portion that is pivotally supported by a support shaft disposed in the vicinity of the cam shaft and extends from the pivot end. And a third arm having a moving cam surface.

  According to the present invention, when the lift period in which the driving cam facing roller receives the opening / closing operation force is displaced by the rocker arm mechanism back and forth in the rotational direction of the driving cam, the cam of the driving cam is at least in the descending section of the cam surface of the driving cam. The cam surface was formed so that the height speed was constant and the cam height acceleration was zero, and the closing timing of the intake valve or exhaust valve was set to be located in the constant cam height speed section. The impact at the start of seating and lift is reduced, and the valve drive noise can be reduced, and the wear of the valve seat and the tip of the valve stem is reduced to improve durability.

  According to the present invention, by setting the descending section longer than the ascending section of the cam surface of the driving cam, the lift period is displaced back and forth in the rotational direction of the driving cam by the rocker arm mechanism, and the change in the lift valve opening time in the lifting period is achieved. It can be set so that the change range at the valve closing time is larger than the range. For this reason, it is possible to easily control the intake valve or the exhaust valve by changing the closing timing of the intake valve or the exhaust valve relatively large, and the variable response of the closing timing is enhanced. In particular, in the case of an intake valve, output control by greatly varying the valve closing timing related to the charging efficiency is facilitated, and the engine controllability is improved. In addition, since variable responsiveness is enhanced, convergence to the target control value during control is enhanced, and fuel consumption is improved. In addition, since the change range of the valve closing timing can be greatly varied, when a phase variable mechanism is additionally provided in the valve mechanism to which the present apparatus is applied, the operation amount of the phase variable mechanism can be small. Thus, the variable responsiveness and the convergence to the target control value are improved, and the fuel consumption is improved. In addition to this, the variable range of the phase variable mechanism is small, and a widely used phase variable device can be used, thereby reducing the cost.

  According to the present invention, when the valve lift amount is determined by the rocking cam surface of the third arm provided in the rocker arm mechanism and the drive cam, it can be adjusted on the cam surface side of the drive cam on the basis of the rocking cam surface. A cam shape can be formed. Furthermore, when driving the valve by combining the drive cam and the swing cam, the cam area used at the start of the seating and lifting of the valve on the swing cam side is always the same when it is variable. This can reduce the impact of the valve, reduce the valve drive noise, and improve the durability.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. A symbol E shown in FIG. 1 indicates a four-cylinder reciprocating gasoline engine (hereinafter simply referred to as “engine E”) as an internal combustion engine. A variable valve operating device 8 to be described later is applied to this engine. A cylinder block (not shown) is overlapped and fastened to the lower surface of the cylinder head 1 of the engine 1. In the cylinder block, combustion chambers 2 are respectively formed along an array of a plurality of (for example, four) cylinders along the longitudinal direction X of the cylinder head 1 (the vertical direction in FIG. 1). In each combustion chamber 2, two (a pair) intake ports 3 and exhaust ports 4 are formed. In FIG. 1, the intake port 3 and the exhaust port 4 show only one side. An intake valve 5 that opens and closes the intake port 3 and an exhaust valve 6 that opens and closes the exhaust port 4 are assembled to the top of the cylinder head 1. A plurality of intake valves 5 and a plurality of exhaust valves 6 are provided with valve springs 7 that urge the valves in the closing direction. A variable valve operating device 8 as an SOHC type valve operating system for driving a plurality of intake valves 5 and a plurality of exhaust valves 6 is mounted on the top of the cylinder head 1.

  The variable valve operating device 8 is provided with a camshaft 9 on the cylinder head 1 and above the combustion chamber 2 so as to be rotatable in the longitudinal direction of the cylinder head 1 (in the direction perpendicular to the paper in FIG. 1). A timing pulley (not shown) is connected to one end of the camshaft 9. Rotation of an engine crankshaft (not shown) is transmitted to the timing pulley, whereby the camshaft is driven and the intake cam 14 and the exhaust cam 15 are rotationally driven.

  The camshaft 9 that constitutes the variable valve operating device 8 has an intake side rocker shaft 11 that can rotate in parallel with the camshaft 9 on one side of the upper left and right sides (left and right side in the width direction of the cylinder head) sandwiching the camshaft 9. Each rocker shaft 12 is disposed. In the upper region between the rocker shaft 11 and the rocker shaft 12, a support shaft 13 as a support shaft is disposed substantially parallel to the camshaft 9.

  The camshaft 9 is formed with an intake cam 14 and an exhaust cam 15 as drive cams for each portion facing each combustion chamber 2. Specifically, the intake cam 14 is formed at a position in the center of the overhead of the combustion chamber 2, and the exhaust cam 15 is formed on both sides sandwiching the intake cam 14. The rocker shaft 12 on the exhaust side is provided with a rocker arm 17 (only one side is shown in FIG. 1) for driving the exhaust valve 6 for each exhaust cam 16 so as to be rotatable. The rocker shaft 11 on the intake side is provided with a rocker arm mechanism 18 that drives a plurality (a pair) of intake valves 5 together for each intake cam 14. The variable valve device 8 is configured so that the exhaust side and the intake side are rotated by a single camshaft 9, and the intake valve 5 and the intake valve 5 are separated every predetermined combustion cycle (4 cycles of intake stroke, compression stroke, explosion stroke, and exhaust stroke). Each exhaust valve 6 is configured to open and close.

  As shown in FIG. 2, the intake cam 14 as a drive cam has a cam surface 141 as an outer peripheral surface thereof having a base section n and a cam lift section m, and the cam top 141 has a cam top O from the base section n. The descending section md returning from the cam top O to the base section n is set longer than the reaching up section mu. The cam surface 141 in the descending section md is formed with a section mdn so that the operation speed of the driven member driven by the intake cam 14 is substantially constant and the operation acceleration is zero. In this embodiment, also in the ascending section mu, the section mun is formed so that the operation speed of the intake cam 14 is substantially constant and the operation acceleration is approximately zero in the previous period. In the intake cam 14, the cam convex curvature of the cam top O is set smaller on the down section side than the up section side mu, that is, the cam curvature radius is set larger on the down section side md than the up section side mu.

  3, the movement amount Ch1 of the driven member driven by the cam surface 141 is shown, and FIG. 8 is a schematic diagram of the Ch1. As is clear from the schematic diagrams of FIGS. 2 and 8, the cam curvature radius ru of the up section side mu on the cam surface 141 is set to be relatively small, so that the up to reach the cam top O from the base section n continuous thereto. The lift amount curve in the section mu can be formed relatively short. Further, the cam convex curvature near the cam top is set smaller on the down section side than on the up section side, that is, the cam curvature radius is set relatively large on the down section side md (> mu). The lift amount curve of the descending section md that reaches the cam top O from the section n can be formed relatively long. Further, the section mun and the section mdn that are constant operating speed sections are formed so that the distance between the rotation center of the camshaft 9 and the cam surface 141 decreases in a linear function. The effect of the cam 14 will be described later.

  Next, a specific example of the characteristics of the cam surface 141 of FIG. 2 is shown in FIG. Here, the difference between the relatively long formed down section side md and the relatively short formed up section mu is set to about 20 degrees (= md−mu) in cam angle.

  Here, the operation speed Vc obtained based on the cam surface 141 composed of the operation amount Ch1 and the operation positive acceleration Ca are shown in FIG. The operating speed Vc is set so as to increase / decrease with a positive value in the upstream section mu and increase / decrease with a negative value on the downstream section md. The movement positive acceleration Ca corresponding to the movement speed Vc shows a relatively large positive value at the initial stage of the lift in the ascending section mu, becomes substantially zero in the section mun of about 1/3 of the main region, and then suddenly becomes negative. Holds the value of. Further, the positive operating acceleration Ca is formed so as to continue to hold a negative value in the first half section mdf of about 1/3 of the down section md, reverse in the second half section mdn, and hold a substantially zero value. The Then, at the end of the descending section md, the rising operation speed Vc can be gradually reduced to a positive value and converged to zero.

  FIG. 4 shows a plan view of a rocker arm mechanism 18 that drives the intake valve 5 side of the variable valve operating device 8, and FIG. 5 shows an exploded perspective view of the rocker arm mechanism 18. The rocker arm mechanism 18 is driven by an arm rocker arm 21 as a first arm on which a boss portion 282 that is pivotally supported by a rocker shaft 11 on the intake side is swingably supported, and an intake cam 14 that is a drive cam. An intermediate arm 22 as a second arm, a swing cam 23 as a third cam that is swingably supported by the support shaft 13, and a pivot point P 0 of the intermediate arm 22 supported by the rocker shaft 11. A pin member 25 that is a fulcrum member with which the spherical surface portion 251 is fitted to the concave receiving portion 24 to be set, and a motor 26 (see FIG. 4) that swings the pin member 25 via the rocker shaft 11 are provided. Yes.

  As shown in FIGS. 4 and 5, the rocker arm 21 includes a pair of rocker arm pieces 28 each having a boss portion 282 pivotally supported by the rocker shaft 11. Each of the pair of rocker arm pieces 28 extends from one side of the boss portion 282 with an input end portion 283 receiving a pressing force from the swing cam 23 directed obliquely upward. A pair of input end portions 283 facing each other are integrally coupled to each other by a short shaft 31. A first roller 27 that is a rocker arm roller is fitted on the short shaft 31 via a bearing module (not shown). From the other side of each boss 282 of the pair of rocker arm pieces 28, a pair of working end portions 281 for driving the intake valve 5 are formed to extend, and the intake valve 5 abuts, for example, via an adjusting screw portion 29. .

  The end of the rocker shaft 11 is connected to a control motor 26 as a drive source, and the rocker shaft 11 is formed so as to be able to rotate and be displaced as desired by the operation of the motor 26. A pin member 25, which is a fulcrum member having a spherical surface portion 251 formed at the lower end portion, is screwed in a radially penetrating state at a portion located on the rocker shaft 11 and in the center between the pair of rocker arm pieces 28. The nut 31 is fastened and fixed. The rocker shaft 11 and the pin member 25 receive a switching operation force by driving the motor 26, swing the pin member 25 around the center line Ls of the rocker shaft 11, and the retard position S1 in which the pin member 25 is arranged vertically. From the posture (see FIGS. 1 and 6) to the posture of the advance angle position S2 (see FIG. 6) inclined at an angle of about 45 ° in the camshaft rotation direction (see FIG. 6). Is a fulcrum moving mechanism 34 that can be switched and displaced back and forth in the rotational direction of the intake cam 14.

  As shown in FIGS. 1 and 5, the intermediate arm 22 includes a second roller 32 as a driving cam-opposing roller that is in rolling contact with the cam surface 141 of the intake cam 14 that is a driving cam, and a second support 32 that pivots the second roller 32. And a holder portion 33 (see FIG. 5), which is an L-shaped member that is pivotally supported. The holder portion 33 pivotally supports the second roller 32 on a pivot portion 330 which is a bent portion thereof, and is used for relay extending in a column shape upward from the pivot portion 330, specifically, between the rocker shaft 11 and the support shaft 13. The arm portion 331 and a flat fulcrum arm portion 332 extending from the side portion of the pivotal support portion 330 toward the lower side of the rocker shaft 11 are formed in an L shape as a whole.

  An inclined surface fs1 that forms an input point (relay) for transmitting the displacement to the swing cam 23 is formed at the tip (upper end) of the relay arm portion 331. Here, the inclined surface fs1 is formed such that the inclined surface fs1 is inclined such that the fulcrum arm portion 332 side (right side in FIG. 6) is low and the support shaft 13 side (left side in FIG. 6) is high.

  A spherical receiving portion 24 into which the spherical portion 251 of the pin member 25 supported by the rocker shaft 11 is fitted so as to be relatively displaceable is formed at the protruding end of the fulcrum arm portion 332. Here, when the intake cam 14 makes one rotation, the intermediate arm 22 in which the second roller 32 is brought into contact with the intake cam is interlocked, and the spherical portion 251 of the intermediate arm 22 is supported by the rocker shaft 11. The intermediate arm 22 swings one reciprocating motion up and down around the pivot point P0 formed by fitting with the receiving portion 24. At this time, as shown in FIG. Is swung by the vertical displacement amount H0.

  That is, the fulcrum moving mechanism 34 supports the pivot point P0 on the rocker shaft 11 side of the intermediate arm 22 so as to be movable in a direction intersecting the axial direction of the shaft, and the displacement of the intermediate arm 22 caused by this movement is prevented. As shown in FIG. 6, the rolling contact position of the second roller 32 with respect to the intake cam 14 is configured to be displaceable around the rotation direction Q of the cam, that is, in the advance angle or retard angle direction. Yes.

  As shown in FIGS. 1, 5, and 6, the swing cam 23 is a pivot end that is rotatably inserted into a support shaft 13 as a support shaft disposed near the upper portion of the camshaft 9. A cylindrical boss 35, an arm portion 36 as a swinging extension portion extending from the cylindrical boss 35 toward the first roller 27 (the rocker arm 21 side), and a lower portion of an intermediate position in the extending direction of the arm portion 36 Formed at a displacement receiving portion 37 that forms an input point q1, a swing cam surface 38 that is formed at a bulging portion 361 that forms a swing end of the arm portion 36 and that can apply a pressing force to the first roller 27, and a pivot. It has the arm part 36 of the cylindrical boss | hub 35 as a support end part, and the spring receiving part 41 extended from an opposite side surface. Note that a pusher 42 that applies an elastic force to urge the intake cam 9, the intermediate arm 22, and the swing arm 23 in close contact with each other is in contact with the spring receiving portion 41.

  The swing cam 23 has a swing cam surface 38 formed at the swing end of its arm portion 36. The swing cam surface 38 is formed such that the distance d, which is the swing radius from the pivot point P0, which is the center of the support shaft 13, is increased or decreased. As shown in FIG. 6, the swing cam surface 38 is formed with a base circle section a on the upper side and a lift section b on the lower side.

  The base circle section a is formed by an arc surface having a constant distance from the pivot point q2 that coincides with the axis of the support shaft 13. The lift section “b” is formed as an arcuate surface in the opposite direction in which the distance from the pivot point q2 gradually increases after continuing to the arc of the base circle section “a”.

  As shown in FIG. 6, the displacement receiving portion 37 below the arm portion 36 is located immediately above the camshaft 9, and is formed with a recessed portion 371. The recessed portion 371 has the same orientation as that of the camshaft 9 and is short. A shaft 39 is pivotally attached to the shaft 39. A concave portion 391 is formed in the lower portion of the short shaft 39 exposed from the open portion of the concave portion 371. The leading end of the relay arm portion 331 is inserted in the concave portion 391 so that the inclined surface fs1 is slidably contacted with the bottom surface of the concave portion 391 to hold the input point q1.

  As shown in FIG. 6, the input point q 1 where the inclined surface fs 1 abuts against the bottom surface of the recess 391 is advanced by the fulcrum moving mechanism 34 so that the second roller 32 of the intermediate arm 22 moves forward and backward in the rotational direction Q of the intake cam 14. It is formed so that it can be displaced simultaneously when it is angled or retarded. That is, the contact position between the inclined surface fs1 and the bottom surface of the recess 391 is moved upward by the advance movement (right movement in FIG. 6) of the intermediate arm 22 as the second arm, that is, the swing cam surface of the swing cam 23. 38, the first roller 27 faces the lift section b at an early stage, and functions to increase and correct the valve lift amount hr1 (see FIG. 6).

  The operation of the variable valve operating apparatus 8 configured as described above will be described. The camshaft 9 and the intake cam 14 rotate, the second roller 32 of the intermediate arm 22 shown in FIG. 2 faces the base section n of the cam surface 141, then faces the up section side mu in the cam lift section m, and then the cam After passing through the top O, it faces the downstream section md and then again faces the base section n. In the cam lift section m at this time, the second roller 32 of the intermediate arm 22 is pressed and driven. At this time, as shown in FIG. 7, the intermediate arm 22 is swung with a vertical displacement amount hrn with the pivot point P0 of the spherical portion 251 as the pivot on the rocker shaft 11 side as a fulcrum. This oscillating displacement is transmitted from the relay arm portion 331 of the intermediate arm 22 to the swing cam 23 immediately above it. Here, between the inclined surface fs1 and the bottom surface of the concave portion 391, the return spring force of the pusher 42 keeps the pressure contact state, and the swing cam 23 is swung in the vertical direction. Here, the swing cam surface 38 of the swing cam 23 is brought into rolling contact with the first roller 27 of the rocker arm 21, and in particular, when the first roller 27 is pressed in the lift section b, the pair of rocker arm pieces 28 of the rocker arm 21 are moved. Driving around the center line Ls of the rocker shaft 11 opens and closes the pair of intake valves 5 simultaneously.

  During the operation of the variable valve apparatus 8 as described above, a control means (not shown) obtains the optimum fulcrum position P0 according to the operating state, and drives the control motor 26 with an output corresponding to the fulcrum position P0. The control motor 26 rotates the pin member 25 via the rocker shaft 11 and positions the fulcrum position P0 of the intermediate arm 22 at the retarded angle position S1 at which the maximum valve lift amount hr1 is obtained, for example, as shown by the solid line in FIG. And

  In this case, the inclined surface fs1 of the relay arm portion 331 of the intermediate arm 22 moves the swing cam 23 (corresponding to the third arm) upward, and the first roller 27 swings relatively early (crank angle θ1 in FIG. 3). In contact with the lift section b of the moving cam surface 38, the rocker arm 21 swings in the lift section E1 along the lift displacement amount diagram Dh1 corresponding to the operation amount hr1, and then at the most retarded crank angle θ11. The first roller 27 returns to the base section a of the swing cam surface 38, and the rocker arm 21 swings for one cycle. In this case, the intake valve 5 is controlled to open and close with the same displacement characteristics as the lift displacement amount diagram Dh1 of the rocker arm 21.

  Next, during operation of the variable valve operating apparatus 8, the control motor 26 rotates the pin member 25 via the rocker shaft 11, and as shown by a broken line in FIG. 6, the advance position Sn where the minimum operation amount hrn is obtained. Assume that the fulcrum position P0 of the intermediate arm 22 is positioned at the same time.

  In this case, the inclined surface fs1 of the relay arm portion 331 of the intermediate arm 22 moves the swing cam 23 downward, and the first roller 27 lifts the swing cam surface 38 at a relatively delayed time (crank angle θn in FIG. 3). In contact with the section b, the rocker arm 21 swings in the lift section En along the lift displacement amount diagram Dhn corresponding to the operation amount hrn, and then the first roller 27 swings at the crank angle θnn on the retard side. Returning to the base section “a” of the cam surface 38, the rocker arm 21 completes one cycle of swinging. In this case, the intake valve 5 is controlled to open and close with the same displacement characteristics as the lift displacement amount diagram Dhn of the rocker arm 21.

  Further, during operation of the variable valve apparatus 8, a control means (not shown) obtains an optimum fulcrum position P0 according to the operating state, and the control motor 26 is driven with an output corresponding to the fulcrum position P0, and according to each fulcrum position P0. Thus, the lift sections E1 to En in which the second roller 32 of the intermediate arm 22 contacts the intake cam 14 are adjusted in size as shown in FIG. 3, and the lift displacement of the rocker arm 21 is changed according to the fluctuation of the lift sections E1 to En. The quantity diagrams Dh1 to Dhn are adjusted in size as shown in FIG.

  3 shows only the lift sections E1 and En, but the lift sections E2, E3, E4, and E5 (not shown) located in the middle of the lift sections E1 and En operate according to the lift sections E1 and En according to the lift sections. However, illustration and duplication description are omitted here. Similarly, in FIG. 3, in addition to the lift displacement amount diagrams Dh1 to Dhn, lift displacement amount diagrams Dh2, Dh3, Dh4, and Dh5 located in the intermediate portion are shown. Since the operation according to FIGS. Dh1 to Dhn is performed, redundant description thereof is omitted here.

  As described above, in the variable valve operating apparatus 8 of FIG. 1, the optimum fulcrum position P0 is obtained in advance by the control means in accordance with the operating state of the engine, and the intermediate arm 22 is oscillated and displaced at the fulcrum position P0. According to each fulcrum position P0, the lift displacement amount Vr of the rocker arm corresponding to the lift displacement amount diagrams Dh1 to Dhn, that is, the valve lift amount of the intake valve 5 can be obtained.

  In the variable valve operating apparatus 8, as shown in FIG. 3, a section mun and a section mdn in which the operation speed is constant and the operation acceleration is substantially zero are formed in the up section mu and the down section md, and the intake valve 5 Since the valve opening timing and the valve closing timing are adjusted to be performed within the section mun and the section mdn, it is possible to reduce the impact at the time of lift (when the valve is opened) and at the time of sitting (when the valve is closed). For this reason, while being able to reduce valve drive noise, the wear of the valve seat provided in the intake port 3 or the tip of the valve stem can be reduced, and durability is improved.

  Since the descending section md of the cam surface 141 of the intake cam 14 is set longer than the ascending section mu, the lift displacement according to the rocker arm mechanism 18 being displaced in the front and back in the rotational direction Q of the intake cam 14. It is possible to switch the quantity diagrams Dh1 to Dhn and set the change range Gr of the valve closing times θnn to θ11 according to these lift displacement amount diagrams to be sufficiently large.

  As described above, since the change region Gr of the closing timing of the intake valve or the exhaust valve can be varied more greatly, the closing control is facilitated, the variable response of the closing timing is further increased, and the output control is further facilitated. Engine controllability is further improved. In particular, in the case of the intake valve 5 driven by the intake cam 14, output control by greatly varying the valve closing timing related to the charging efficiency is facilitated, and engine controllability is improved. In addition, since variable responsiveness is enhanced, convergence to the target control value during control is enhanced, and fuel efficiency is improved.

  Further, since the change region G (timing) of the valve closing timings θnn to θ11 can be greatly varied, a variable valve device 8 to which the present apparatus is applied and a crankshaft of an engine (not shown) are not separately shown. In the case where the phase variable mechanism is additionally provided, the amount of operation of the phase variable mechanism is small, and the variable response and the convergence to the target control value are increased and the fuel consumption is improved. In addition, the variable range of the phase variable mechanism can be small, and a widely used phase variable device can be used to reduce the cost.

  In the variable valve operating device 8 of FIG. 1, in addition to the cam surface 141 of the intake cam 14 having a descending section md that is longer than the ascending section mu, the cam convex curvature near the cam top O is increased from the ascending section side. Since the descending section side is also set to be small, when the rocker arm mechanism 18 is used to switch the lift period E to be displaced back and forth in the rotational direction of the intake cam 14 (drive cam), the change in the lift valve opening time θ1 during the lift period E is changed. The change region Gr of the valve closing timing θ11 can be set to be larger than the region Gf. As a result, control by greatly changing the closing timing of the intake valve 5 or the exhaust valve 6 is facilitated, variable response of the closing timing is further increased, output control is further facilitated, and engine controllability is further improved. improves.

  In the variable valve operating apparatus 8 of FIG. 1, the intake cam 14 contacting the cam surface 141 has a substantially constant and relatively small value of the operation positive acceleration Ca in the latter period mdn of the descending section md. Since the operation speed Vc can be gradually reduced and converged to zero, the impact when the valve is closed can be reduced.

  1 uses the rocker arm mechanism 18 described with reference to FIGS. 4 and 5, so that the control for displacing the cam lift section m around the rotation direction Q of the intake cam 14 (drive cam) is ensured. Can be done.

  In the present embodiment, the drive cam is described as the intake cam 14, but it may be an exhaust cam. In this case, the engine controllability is improved, the convergence to the target control value at the time of control is improved, and the fuel consumption is improved. improves.

  In this embodiment, the cam surface 141 of the intake cam 14 is formed with the section mun that is the constant operating speed section in the up section mu, but it is sufficient that the section mdn is formed at least in the down section md. Further, as the drive cam that forms the section mun and / or the section mdn, the drive cam in which the down section md is set longer than the up section mu of the cam surface 141 in this embodiment is illustrated. It is not limited to. For example, the present invention may be applied to a cam cam having a cam profile in which the ascending section mu and the descending section md of the cam surface 141 have substantially the same length. Even in such a case, the impact when the valves are opened and closed is absorbed. It is possible to reduce the noise of the valve and improve the durability. Further, since the seating impact at the time of closing the valve is larger at the time of high rotation and high lift, the seating impact may be set so as to be seated at a section of the operation positive acceleration Ca having a relatively constant relatively small value at least during the middle and high lift.

1 is a side sectional view of a cylinder head of an engine having a variable valve operating apparatus for an internal combustion engine as one embodiment of the present invention. FIG. 2 is an enlarged side view of an intake cam used in the variable valve operating apparatus for the internal combustion engine of FIG. 1. FIG. 2 is an operation characteristic explanatory diagram of the variable valve operating apparatus for the internal combustion engine of FIG. 1, and particularly shows a valve lift displacement amount diagram of an intake cam, an operation speed and acceleration diagram of a driven member, and a lift displacement amount diagram. It is a top view of the rocker arm mechanism used with the variable valve operating apparatus of the internal combustion engine of FIG. It is a disassembled perspective view of the rocker arm mechanism in the variable valve operating apparatus of the internal combustion engine of FIG. FIG. 2 is an explanatory view of an advance angle and a retard angle operation of an intermediate arm of the rocker arm mechanism in FIG. 1. It is lift displacement operation | movement explanatory drawing of the intermediate | middle arm of the rocker arm mechanism in FIG. It is a schematic operation characteristic explanatory view of an intake valve driven by the variable valve operating apparatus. It is a schematic operation characteristic explanatory view of an intake valve driven by a conventional variable valve operating device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylinder head 5 Intake valve 6 Exhaust valve 8 Variable valve operating apparatus 9 Camshaft 13 Support shaft 14 Intake cam (drive cam)
141 Cam surface 18 Rocker arm mechanism 21 Rocker arm (first arm)
22 Intermediate arm (second arm)
23 Swing cam (3rd arm)
26 Motor (drive source)
27 1st roller (Rocker arm roller)
32 Second roller (drive cam facing roller)
34 fulcrum moving mechanism 38 rocking cam surface a base section b lift section E internal combustion engine m lift period θ1 lift valve opening time θ11 valve closing time mu up section md down section mun constant cam acceleration section P0 pivot point (fulcrum position)
Q Rotation direction of drive cam

Claims (3)

A camshaft rotatably provided in the internal combustion engine, a drive cam integrally formed with the camshaft, and oscillated by receiving an opening / closing operation force from the drive cam to be an intake valve or an exhaust valve of the internal combustion engine In a variable valve operating apparatus for an internal combustion engine having a rocker arm mechanism having a rocking cam surface for transmitting an opening / closing operation force,
The rocker arm mechanism performs valve lift so as to change the opening / closing timing and lift amount of the intake valve or exhaust valve according to the operating state of the internal combustion engine by changing a cam lift period received by the drive cam,
The drive cam has a substantially constant cam acceleration in the valve seating section of the drive cam corresponding to a change region of the valve closing timing of the intake valve or the exhaust valve that is continuously changed according to a change in the cam lift period. is set so as to,
The variable valve operating apparatus for an internal combustion engine, wherein the valve seating section is a section formed so that a moving speed of the swing cam surface driven by rotation of the camshaft is substantially constant . The variable valve apparatus according to claim 1 Symbol placement of an internal combustion engine,
An internal combustion engine characterized in that a down section is formed longer than an up section of the cam surface of the drive cam so that a change area at the valve closing time is larger than a change area at the valve opening time of the cam lift period. Variable valve gear. The variable valve operating apparatus for an internal combustion engine according to claim 1 or 2,
The rocker arm mechanism is
A first arm that drives an intake valve or an exhaust valve that rotates around a fulcrum position by a pivotal rocker arm roller receiving a pressing force and contacts the rocking cam surface;
A pivot supporting portion that pivotally supports the driving cam facing roller that contacts the driving cam, and a fulcrum end portion that receives a switching operation force that displaces the lift period back and forth in the rotational direction of the driving cam by a predetermined amount from the pivot supporting portion. A second arm;
A fulcrum moving mechanism for displacing a fulcrum member engaged with a fulcrum end portion of the second arm by receiving a switching operation force from a drive source in the forward and backward directions of the drive cam;
An opening / closing operation force can be applied to the rocker arm roller at the swinging end of a swinging extending portion that is pivotally supported by a support shaft disposed in the vicinity of the camshaft and extends from the pivoting support end. A variable valve operating apparatus for an internal combustion engine, comprising: a third arm on which the swing cam surface is formed .

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