JP4474075B2 - Variable lift valve gear - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to an improvement in a variable lift valve operating system in which an opening lift amount of an engine valve that is an intake valve or an exhaust valve is changed.
[0002]
[Prior art]
  Conventionally, as disclosed in Japanese Patent Application Laid-Open No. 7-63023, it is displaceable between a first rocker arm that is swingably supported at a first fulcrum and abuts against an engine valve, and a cam of a camshaft. The second rocker arm supported so as to be swingable at the second fulcrum is interposed, and the contact point of the second rocker arm to the first rocker arm is changed steplessly, thereby changing the lift amount of the engine valve steplessly. There is already known a variable lift valve actuating device.
[0003]
[Problems to be solved by the invention]
  However, in the conventional apparatus, the contact point of the second rocker arm with the first rocker arm is set below the axis of the camshaft, whereas the contact point of the second rocker arm with the cam is lateral to the camshaft axis. The direction of the load acting on the second rocker arm from the cam and the direction of the load acting on the first rocker arm from the second rocker arm are greatly different, and the bending load acting on the second rocker arm becomes large. For this reason, the second rocker arm is easily deformed, and if the rigidity of the second rocker arm is increased in order to prevent the deformation, the weight of the second rocker arm, and hence the weight of the valve operating device, is increased.
[0004]
  The present invention has been made in view of such circumstances, and a lift that suppresses the bending load applied to the second rocker arm and changes the valve opening lift amount of the engine valve while avoiding an increase in the weight of the second rocker arm. An object is to provide a variable valve operating apparatus.
[0005]
[Means for Solving the Problems]
  In order to achieve the above-mentioned object, the invention according to claim 1 is characterized in that a camshaft provided with a cam and a camshaft supported on a first fulcrum and capable of swinging about an axis parallel to the camshaft and mounted on an engine valve. A first rocker arm abutted on and a second fulcrum that is displaceable so as to be able to swing around an axis parallel to the camshaft and is interposed between the cam and the first rocker arm. In the lift variable valve operating apparatus including the rocker arm, the first and second imaginary triangles connecting the axis of the camshaft, the first fulcrum, and the second fulcrum on the projection onto the plane orthogonal to the axis of the camshaft. The contact points of the two rocker arms and the contact points of the cam and the second rocker arm areAlwaysPlacedIn the displacement range of the second fulcrum, the camshaft axis and both contact points are aligned on a straight line on the projection view when the lift amount of the engine valve is larger than the maximum and minimum intermediate values. The displacement range of the second fulcrum is set asIt is characterized by that.
[0006]
  According to such a configuration of the first aspect of the invention, the contact point of the second rocker arm with the first rocker arm and the contact point of the second rocker arm with the cam can be changed by displacing the second fulcrum. Thereby, the lift amount of the engine valve can be changed. Moreover, on the projection onto the plane orthogonal to the axis of the camshaft, the contact points of the first and second rocker arms, the cam and the first and second rocker arms are within a virtual triangle connecting the axis of the camshaft, the first fulcrum and the second fulcrum. 2 The contact point of the rocker armAlwaysTherefore, the direction of the load acting on the second rocker arm from the cam is not greatly different from the direction of the load acting on the first rocker arm from the second rocker arm, and the bending load acting on the second rocker arm is suppressed. Therefore, it is possible to prevent the second rocker arm from being deformed, and since it is not necessary to increase the rigidity of the second rocker arm, it is possible to reduce the weight of the second rocker arm and hence the valve operating device.
[0007]
  Also,in frontOf the displacement range of the second fulcrum, at one point when the lift amount of the engine valve is larger than the maximum and minimum intermediate values, the axis of the camshaft and the two contact points are aligned on the projection view. The displacement range of the second fulcrum is setBecauseThe direction of the load acting on the second rocker arm from the cam when the load applied to the second rocker arm increases and the direction of the load acting on the first rocker arm from the second rocker arm can be made the same direction on a straight line.The,The bending load applied to the second rocker arm can be minimized, and the direction of the load acting on the second rocker arm from the cam and the load acting on the first rocker arm from the second rocker arm over the entire displacement range of the second fulcrum. The direction is almost the same direction,Bending load on the second rocker armEffectIt can be suppressed effectively.
[0008]
  Claim2The invention described is the above claim.1In addition to the configuration of the invention described above, in the direction along the axis of the cylinder bore provided in the cylinder block by slidably fitting a piston that faces the top of the combustion chamber, the second fulcrum is more than the camshaft. According to this configuration, the second rocker arm is effectively arranged in the space between the camshaft and the combustion chamber, which contributes to downsizing of the entire valve operating apparatus. be able to.
[0009]
  Claim3The invention described is the above claim 1.Or 2In addition to the configuration of the described invention, the second fulcrum is arranged between the axis of the camshaft and the first fulcrum in a direction along the axis of the cylinder bore provided in the cylinder block. The second rocker arm can be effectively arranged between the camshaft and the first rocker arm, which contributes to the compactness of the entire valve operating apparatus.
[0010]
  Claim4The invention according to claim 1 to claim 13In addition to the configuration of any of the inventions described above, the first rocker arm is provided with a pair of valve abutting portions that respectively abut against a pair of engine valves arranged in a direction along the axis of the camshaft, and these valve abutting portions A single second rocker arm that is common to both engine valves is disposed between the two engine valves, and according to such a configuration, a pair of engine valves are provided using the single first and second rocker arms, respectively. It is possible to reduce the number of parts and make the valve operating device more compact by opening and closing.
[0011]
  Further claims5The invention according to claim 1 to claim 14In addition to the configuration of any one of the inventions described above, a slipper surface provided on the first rocker arm for contacting the second rocker arm, the second fulcrum being angularly displaceable around the third fulcrum set at a fixed position, In this configuration, the second fulcrum is displaced to change the contact point of the second rocker arm with the first rocker arm. In addition, the tappet clearance between the first rocker arm and the engine valve can be kept constant, and abnormal noise can be prevented from occurring due to a change in the lift amount of the engine valve.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on examples of the present invention shown in the accompanying drawings.
[0013]
  1 to 6 show a first embodiment of the present invention. FIG. 1 is a partial longitudinal sectional view of an internal combustion engine showing a closed state of an engine valve with a minimum lift amount. FIG. 2 is a cross-sectional view taken along line 2-2 in FIG. 1, FIG. 3 is a cross-sectional view taken along line 3-3 in FIG. 2 with the cylinder head omitted, and FIG. 4 is a minimum lift amount. FIG. 5 is a partial vertical sectional view of the internal combustion engine showing the engine valve closed state at the maximum lift amount, and FIG. 6 is a maximum lift amount. It is a partial longitudinal cross-sectional view of the internal combustion engine which shows an engine valve open state.
[0014]
  First, in FIGS. 1 to 3, a piston 13 is slidably fitted in a cylinder bore 12 provided in the cylinder block 11, and the piston 13 is connected between the cylinder head 15 and the cylinder block 11 coupled to the cylinder block 11. A combustion chamber 14 is formed to face the top.
[0015]
  The cylinder head 15 is provided with a pair of ports 16 that are intake ports or exhaust ports so as to communicate with the combustion chamber 14, and a pair of engine valves 17 that are intake valves or exhaust valves are provided with It arrange | positions at the cylinder head 15 so that the opening end to the combustion chamber 14 of each port 16 ... can be closed.
[0016]
  The engine valve 17 includes an umbrella-shaped valve portion 17a that can close an opening end of the port 16 to the combustion chamber 14, and is integrally formed at one end of a valve stem 17b that extends in a rod shape. 17 b slidably penetrates the guide cylinder 18 fitted and fixed to the cylinder head 15, and is interposed between the retainer 19 and the cylinder head 15 fixed to the other end of the valve stem 17 b protruding from the guide cylinder 18. A valve spring 20 that biases the engine valve 17 in the valve closing direction is contracted.
[0017]
  The pair of engine valves 17, which are respectively urged in the valve closing direction by the valve springs 20, are given a driving force in the valve opening direction from the variable lift valve operating device 21 </ b> A. 21A is rotatable about an axis parallel to the parallel direction of the pair of engine valves 17... And a camshaft 23 provided with one cam 22 for both engine valves 17. The first rocker arm 24A that is supported at the first fulcrum F1 and abutted against the engine valve 17 and the camshaft 23 can be swung around the axis parallel to the camshaft 23. The second rocker arm 25A is supported by the displaceable second fulcrum F2 and is interposed between the cam 22 and the first rocker arm 24A.
[0018]
  Moreover, the second fulcrum F2 can be displaced at a position closer to the combustion chamber 14 than the camshaft 23 in the direction along the axis of the cylinder bore 12, and the axis C and the first axis of the camshaft 23 in the direction along the axis of the cylinder bore 12. A second fulcrum F2 is disposed between the fulcrums F1.
[0019]
  Further, on the projection onto the plane orthogonal to the axis C of the camshaft 23, the first and second rocker arms 24A, 24A, 24C are located within a virtual triangle T connecting the axis C of the camshaft 23, the first fulcrum F1 and the second fulcrum F2. The contact point P1 of 25A and the contact point P2 of the cam 22 and the second rocker arm 25A areAlwaysFirst and second rocker arms 24A and 25A are formed so as to be arranged.
[0020]
  A first rocker shaft 26A that arranges an axis on the first fulcrum F1 is fixedly arranged on the combustion chamber 14 side (lower side in FIG. 1) with respect to the camshaft 23, and one end of the first rocker arm 24A is connected to the first rocker arm 24A. The first rocker shaft 26A is supported so as to be able to swing while the movement of the shaft 26A in the direction along the axis is restricted. The other end side of the first rocker arm 24A is formed in a substantially T shape, and a tappet screw 27, 27 as a pair of valve abutting portions arranged in the direction along the axis of the camshaft 23 can adjust the advance / retreat position. 1 is provided at the other end of the rocker arm 24A, and both tappet screws 27 are brought into contact with the other end (upper end in FIG. 1) of the valve stem 17b in the engine valve 17.
[0021]
  A single second rocker arm 25A that is common to the pair of engine valves 17 is disposed between the two tappet screws 27, 27 of the first rocker arm 24A. The second rocker arm 25A is a second rocker arm 25A. The second rocker shaft 28A having the fulcrum F2 as an axis is supported so as to be swingable.
[0022]
  The second rocker shaft 28A is supported between one end of a pair of levers 29, 29 arranged on both sides of the first and second rocker arms 25A, and between the second rocker arm 25A and one end of both levers 29, 29. Cylindrical spacers 30 and 30 through which the second rocker shaft 28A is inserted are interposed. Further, the other ends of both levers 29 and 29 are fixed so that rotating shafts 31 and 31 having axes arranged on a third fulcrum F3 arranged at a fixed position extend outward of both levers 29 and 29. Connected to
[0023]
  A rotation driving means 32 is connected to one of the rotation shafts 31, 31. The rotation drive means 32 includes a fan-shaped worm wheel 33 fixed to the rotation shaft 31, and a drive shaft 34 having an axis perpendicular to the rotation shaft 31 and rotatably supported by the cylinder head 15. A worm 35 meshed with the worm wheel 33 and fixed to the drive shaft 34, and an actuator 36 such as an electric motor connected to the drive shaft 34.
[0024]
  The rotation drive means 32 is provided on the side where the timing transmission mechanism is arranged in order to reduce the size of the internal combustion engine while avoiding interference with the timing transmission mechanism provided between the crankshaft and the camshaft 23. Are arranged in the internal combustion engine on the opposite side (ie the transmission side).
[0025]
  Thus, the levers 29, 29 and the rotation shafts 31, 31 provided between the rotation drive means 32 and the second rocker shaft 28A are configured in a crank shape so as to sandwich the first and second rocker arms 24A, 25A. Thus, it is possible to contribute to downsizing of the entire variable lift valve operating device 21A. In particular, in this first embodiment, the rotary shafts 31, 31 are arranged at positions that partially overlap the first rocker arm 24A on a projection view onto a plane orthogonal to the axis line, and the valve operating device 21A. The overall size can be further reduced.
[0026]
  Further, the pivot shaft 31 is supported by the cylinder head 15 so as to be pivotable, and a dedicated holder for supporting the pivot shaft 31 is not required. The parts can be reduced and the variable lift valve operating device 21A can be made compact. In addition, the support rigidity of the rotating shaft 31 can be increased, and the angular displacement control accuracy of the second fulcrum F2 can be increased.
[0027]
  By the operation of the rotation driving means 32, the second fulcrum F2, that is, the second rocker arm 25A is angularly displaced around the third fulcrum F3, and the cam slipper surface provided on the second rocker arm 25A to be in sliding contact with the cam 22. No. 37 is formed in an arc shape centered on the third fulcrum F3 so as to be slidably contacted with the cam 2 regardless of the angular displacement of the second fulcrum F2.
[0028]
  The first rocker arm 24A is provided with a slipper surface 39 for slidingly contacting the pressing portion 38 provided on the second rocker arm 25A. The slipper surface 39 is also formed in an arc shape centered on the third fulcrum F3. The Thereby, even if the contact point P1 of the second rocker arm 25A to the first rocker arm 24A is changed by angularly displacing the second fulcrum F2, the tappet clearance between the first rocker arm 24A and the engine valve 17 is kept constant. Therefore, it is possible to prevent the generation of noise due to the change in the lift amount of the engine valves 17.
[0029]
  Thus, as shown in FIGS. 1 to 3, the contact point P1 between the first and second rocker arms 24A, 25A is located farthest from the first fulcrum F1, and the contact point P2 between the second rocker arm 25A and the cam 22 is reached. When the rotational drive means 32 determines the position of the second fulcrum F2 so that the second fulcrum F2 is located farthest from the second fulcrum F2, the swing amount of the second rocker arm 25A driven by the cam 22 around the second fulcrum F2 Accordingly, the swing amount of the first rocker arm 24A around the first fulcrum F1 is also minimized, and as shown in FIG. 4, the valve opening lift amount of the engine valve 17 is also minimized.
[0030]
  On the other hand, as shown in FIGS. 5 and 6, the contact point P1 of the first and second rocker arms 24A and 25A is located closest to the first fulcrum F1, and the contact point P2 of the second rocker arm 25A and the cam 22 is the first contact point P2. When the rotational drive means 32 determines the position of the second fulcrum F2 so that it is closest to the two fulcrum F2, the amount of swinging around the second fulcrum F2 of the second rocker arm 25A driven by the cam 22 is maximum. Accordingly, the swing amount of the first rocker arm 24A around the first fulcrum F1 is also maximized, and the valve opening lift amount of the engine valve 17 is also maximized.
[0031]
  That is, the rotation drive means 32 moves the second fulcrum F2 around the third fulcrum F3 between the minimum lift amount position shown in FIGS. 1, 3, and 4 and the maximum lift amount position shown in FIGS. By angularly displacing the second fulcrum F between the lift amount minimum position and the lift amount maximum position, the contact point of the second rocker arm 25A with the first rocker arm 24A and the second rocker arm 25A The contact point P2 to the cam 22 can be changed steplessly, whereby the valve opening lift amount of the engine valves 17 can be changed steplessly.
[0032]
  Moreover, in JP-A-7-63023, a specially shaped control cam that is difficult to be molded is used to change the lift amount of the engine valve. However, the lift amount of the engine valve 17... Can be changed steplessly.
[0033]
  Further, in the displacement range of the second fulcrum F2, one point when the lift amount is larger than the maximum and minimum intermediate values, preferably at the maximum lift of the engine valve 17. As shown, the axis C of the camshaft 23, the contact point P2 of the cam 22 and the second rocker arm 25A, and the contact point P1 of the first and second rocker arms 24A and 24B are perpendicular to the axis C of the camshaft 23. The displacement range of the second fulcrum F2 is set so as to be aligned on a straight line on the projection.
[0034]
  By the way, as the cam shaft 23 rotates, a force in the direction of moving the second rocker arm 25A around the third fulcrum F3 acts on the second rocker arm 25A from the cam 22, but is supported at the first fulcrum F1. Since the force is reduced by the frictional force with the first rocker arm 24A, an unreasonable load does not act on the rotation drive means 32 side.
[0035]
  Next, the operation of the first embodiment will be described. A virtual triangle connecting the axis C of the camshaft 23, the first fulcrum F1 and the second fulcrum F2 on the projection onto the plane orthogonal to the axis C of the camshaft 23. Within T, the contact point P1 of the first and second rocker arms 24A, 25A and the contact point P2 of the cam 22 and the second rocker arm 25A areAlwaysTherefore, the direction of the load acting on the second rocker arm 25A from the cam 22 and the direction of the load acting on the first rocker arm 24A from the second rocker arm 25A can be prevented from being greatly different.
[0036]
  As a result, it is possible to suppress the bending load acting on the second rocker arm 25A and prevent the deformation of the second rocker arm 25A, and it is not necessary to increase the rigidity of the second rocker arm 25A. As a result, the weight of the variable lift valve operating device 21A can be reduced..
[0037]
  ShiMoreover, in the displacement range of the second fulcrum F2, the axis C of the camshaft 23 and the contact points P2 and P1 are at one point when the lift amount of the engine valve 17 is larger than the maximum and minimum intermediate values. Set to align on a straight line on the projection onto the plane orthogonal to axis CBecauseThe direction of the load acting on the second rocker arm 25A from the cam 22 when the load applied to the second rocker arm 25A increases and the direction of the load acting on the first rocker arm 24A from the second rocker arm 25A are in the same direction on a straight line. Bending load applied to the second rocker arm 25AEffectIt can be suppressed effectively. In particular, as in the first embodiment, during the maximum lift of the engine valve 17..., The axis C of the camshaft 23, the contact point P2 of the cam 22 and the second rocker arm 25A, and the first and second rocker arms 24A and 24B. By arranging the contact points P1 in a straight line on the projection, the effect of suppressing the bending load applied to the second rocker arm 25A can be made more remarkable.In addition, by including such one point in the displacement range, the direction of the load acting on the second rocker arm 25A from the cam 22 and the first rocker arm 24A from the second rocker arm 25A also acts over the entire displacement range of the second fulcrum F2. The bending load applied to the second rocker arm 25A can be effectively suppressed with the direction of the load being substantially the same direction.
[0038]
  The second fulcrum F2 is disposed closer to the combustion chamber 14 than the camshaft 23 in the direction along the axis of the cylinder bore 12, and the second rocker arm 25A is disposed in the space between the camshaft 23 and the combustion chamber 14. It can arrange | position effectively and can contribute to the compactization of the whole lift variable valve operating apparatus 21A. Further, since the second fulcrum F2 is disposed between the axis C of the camshaft 23 and the first fulcrum F1 in the direction along the axis of the cylinder bore 12, the second rocker arm 25A is effectively disposed between the camshaft 23 and the first rocker arm 24A. It can arrange | position and can contribute more by making the said valve operating apparatus 21A compact.
[0039]
  By the way, the first rocker arm 24A is provided with a pair of tappet screws 27, 27 that respectively contact a pair of engine valves 17 arranged in the direction along the axis of the camshaft 23, and between the tappet screws 27, 27. In addition, a single second rocker arm 25A that is common to the pair of engine valves 17 is disposed. Therefore, the pair of engine valves 17 can be opened / closed using the single first and second rocker arms 24A, 25A, respectively, so that the number of parts can be reduced and the variable lift valve operating device 21A can be made compact. Can do.
[0040]
  FIGS. 7 and 8 show a second embodiment of the present invention. FIG. 7 is a partial longitudinal sectional view of an internal combustion engine showing an engine valve open state at a maximum lift amount, and FIG. 8 is a minimum lift amount. FIG. 8 is a longitudinal sectional view corresponding to FIG. 7 showing an open state of the engine valve.
[0041]
  The variable lift valve operating device 21B in which a driving force in the valve opening direction is applied to the pair of engine valves 17 is capable of swinging around a camshaft 23 provided with a cam 22 and an axis parallel to the camshaft 23. A first rocker arm 24B supported by the first fulcrum F1 and abutted against the engine valve 17... And swingable about an axis parallel to the camshaft 23 is interposed between the cam 22 and the first rocker arm 24B. The second rocker arm 25B is mounted to support the second rocker arm 25B so as to be swingable, and the second fulcrum F2 that can be angularly displaced around the fixed third fulcrum F3 is in a direction along the axis of the cylinder bore 12. The second fulcrum F2 is disposed between the axis C of the camshaft 23 and the first fulcrum F1.
[0042]
  The first and second rocker arms 24B, 24B are located in a virtual triangle T connecting the axis C of the camshaft 23, the first fulcrum F1 and the second fulcrum F2 on the projection onto the plane orthogonal to the axis C of the camshaft 23. The contact point P1 of 25B and the contact point P2 of the cam 22 and the second rocker arm 25B areAlwaysFirst and second rocker arms 24B and 25B are formed so as to be arranged.
[0043]
  A first rocker shaft 26B having an axis line disposed on the first fulcrum F1 is fixedly disposed on the combustion chamber 14 side (lower side in FIGS. 7 and 8) from the camshaft 23, and one end of the first rocker arm 24B is The first rocker shaft 26B is pivotally supported. The second rocker arm 25B is supported so as to be swingable by a second rocker shaft 28B having the second fulcrum F2 as an axis.
[0044]
  The second rocker shaft 28B is supported by one end of the lever 29, and the other end of the lever 29 is fixedly connected to a rotating shaft 31 having an axis line arranged on a third fulcrum F3 arranged at a fixed position. The rotation driving means 32 is connected to the rotation shaft 31.
[0045]
  By the operation of the rotation driving means 32, the second fulcrum F2, that is, the second rocker arm 25B is angularly displaced about the third fulcrum F3, and the cam slipper surface 40 for always slidingly contacting the cam 22 regardless of the angular displacement. Is provided on the second rocker arm 25B. In addition, the first rocker arm 24B is provided with a slipper surface 42 that slidably contacts the pressing portion 41 provided on the second rocker arm 25B.
[0046]
  Thus, in this second embodiment, the cam slipper surface 40 and the slipper surface 42 are not formed in an arc shape centered on the third fulcrum F3, and the tappet between the first rocker arm 24B and the engine valve 17. Although the clearance cannot be kept constant, the relative shape of the cam slipper surface 40 and the slipper surface 42 is devised so that the cam slipper surface 40 and the slipper surface 42 remain substantially parallel regardless of the displacement of the second fulcrum F. As a result, the change in the tappet clearance is kept small.
[0047]
  As shown in FIG. 7, the contact point P1 of the first and second rocker arms 24B, 25B is closest to the first fulcrum F1, and the contact point P2 of the second rocker arm 25B and cam 22 is the most from the second fulcrum F2. When the rotation drive means 32 determines the position of the second fulcrum F2 so that it is in a close position, the valve opening lift amount of the engine valve 17 is maximized.
[0048]
  On the other hand, as shown in FIG. 8, the contact point P1 of the first and second rocker arms 24B and 25B is located farthest from the first fulcrum F1, and the contact point P2 of the second rocker arm 25B and the cam 22 is the second fulcrum F2. When the rotational driving means 32 determines the position of the second fulcrum F2 so that it is at the farthest position from the engine, the valve opening lift amount of the engine valve 17 is also minimized.
[0049]
  The first rocker shaft 26B for supporting the first rocker arm 24B is formed in a cylindrical shape so as to form an oil passage 43 through which oil flows, and the first rocker shaft 24B is formed at a portion corresponding to the first rocker arm 24. An oil jet 44 is provided on the side wall of the shaft 26B toward the contact point P1 side of the first and second rocker arms 24B, 25B, and a cutout 45 is provided on the first rocker arm 24B. It is done.
[0050]
  According to the second embodiment, although the tappet clearance between the first rocker arm 24B and the engine valve 17 cannot be kept constant, the same effect as the first embodiment can be obtained. Further, lubrication at the contact point P1 between the first and second rocker arms 24B and 25B is possible without complicating the oil path configuration. That is, in the configuration in which the oil jet is provided on the second rocker shaft 28B side with the axis line disposed at the displaceable second fulcrum F2, the oil path configuration for supplying oil to the oil passage in the second rocker shaft 28B is complicated. However, since the oil jet 44 is provided on the first rocker shaft 26B at the fixed position, the oil passage configuration is simplified.
[0051]
  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the present invention described in the claims. It is.
[0052]
  For example, in the above-described embodiment, the second fulcrum F2 is displaced steplessly to change the lift amount of the engine valve 17 steplessly. The lift amount of the engine valve 17 can be changed stepwise by shifting the valve stepwise.
[0053]
【The invention's effect】
  As described above, according to the first aspect of the present invention, it is possible to change the valve opening lift amount of the engine valve while suppressing the bending load applied to the second rocker arm and avoiding an increase in the weight of the second rocker arm.
[0054]
  MaTheThe direction of the load acting on the second rocker arm from the cam when the load applied to the second rocker arm becomes large and the direction of the load acting on the first rocker arm from the second rocker arm are made to be the same direction on a straight line. Such bending loadEffectIt can be suppressed effectively.
[0055]
  Claim2According to the described invention, it is possible to effectively dispose the second rocker arm in the space between the camshaft and the combustion chamber, thereby contributing to the compactness of the entire valve operating apparatus.
[0056]
  Claim3According to the described invention, it is possible to effectively dispose the second rocker arm between the camshaft and the first rocker arm, thereby contributing to the compactness of the entire valve operating apparatus.
[0057]
  Claim4According to the described invention, the number of parts can be reduced and the valve operating apparatus can be made compact.
[0058]
  Further claims5According to the described invention, the tappet clearance between the first rocker arm and the engine valve can be kept constant, and it is possible to prevent the generation of noise due to the change in the lift amount of the engine valve.
[Brief description of the drawings]
FIG. 1 is a partial longitudinal sectional view of an internal combustion engine showing a closed state of an engine valve with a minimum lift amount in the first embodiment, and is a sectional view taken along line 1-1 of FIG.
FIG. 2 is a cross-sectional view taken along line 2-2 of FIG.
3 is a cross-sectional view taken along line 3-3 of FIG. 2 in a state where the cylinder head is omitted.
FIG. 4 is a partial longitudinal sectional view of the internal combustion engine showing an engine valve open state with a minimum lift amount.
FIG. 5 is a partial longitudinal sectional view of the internal combustion engine showing a state where the engine valve is closed when the lift amount is maximum.
FIG. 6 is a partial longitudinal sectional view of the internal combustion engine showing a state in which the engine valve is opened at the maximum lift amount.
FIG. 7 is a partial longitudinal sectional view of an internal combustion engine showing an engine valve open state at a maximum lift amount in a second embodiment.
FIG. 8 is a longitudinal sectional view corresponding to FIG. 7 showing an engine valve open state with a minimum lift amount.
[Explanation of symbols]
11 ... Cylinder block
12 ... Cylinder bore
13 ... Piston
14 ... Combustion chamber
17 ... Engine valve
21A, 21B ... Variable lift valve operating device
22 ... Cam
23 ... Camshaft
24A, 24B ... 1st rocker arm
25A, 25B ... 2nd rocker arm
27 ... Tappet screw as valve contact part
39 ... slipper surface
C ... Camshaft axis
F1 ... 1st fulcrum
F2 ... Second fulcrum
P1: Contact point between the first and second rocker arms
P2: Contact point between cam and second rocker arm
T ... Virtual triangle

Claims (5)

The camshaft (23) provided with the cam (22) and the camshaft (23) are supported at the first fulcrum (F1) so as to be able to swing around an axis parallel to the camshaft (23) and against the engine valve (17). The first rocker arm (24A, 24B) that is in contact with the cam and the cam (22) while being supported by a second fulcrum (F2) that can be swung around an axis parallel to the camshaft (23). And a second rocker arm (25A, 25B) interposed between the first rocker arm (24A, 24B),
A virtual triangle (T) connecting the axis (C), the first fulcrum (F1), and the second fulcrum (F2) of the camshaft (23) on the projection onto the plane orthogonal to the axis of the camshaft (23). The contact points (P1) of the first and second rocker arms (24A, 25A; 24B, 25B) and the contact points (P2) of the cam (22) and the second rocker arms (25A, 25B) are always arranged inside. ,
Of the displacement range of the second fulcrum (F2), at one point when the lift amount of the engine valve (17) is larger than the maximum and minimum intermediate values, the axis (C) of the camshaft (23) and the both contacts points (P1, P2) such that aligned on the drawing the projection, the lift valve operation device which displacement range of the second fulcrum (F2) is characterized Rukoto set. The second fulcrum (F2) is in a direction along the axis of the cylinder bore (12) provided in the cylinder block (11) by slidably fitting the piston (13) facing the top to the combustion chamber (14), the camshaft (23) the combustion chamber (14), characterized in that disposed on the side close to claim 1 Symbol placement of the lift variable valve device than. The second fulcrum (F2) is arranged between the axis of the camshaft (23) and the first fulcrum (F1) in a direction along the axis of the cylinder bore (12) provided in the cylinder block (11). The lift variable valve operating apparatus according to claim 1 or 2 . The first rocker arm (24A) is provided with a pair of valve abutting portions (27) that respectively abut against a pair of engine valves (17) arranged in a direction along the axis of the camshaft (23). 27) The variable lift valve operating apparatus according to any one of claims 1 to 3 , wherein a single second rocker arm (25A) common to both engine valves (17) is disposed between the two engine valves (17). The second fulcrum (F2) can be angularly displaced around the third fulcrum (F3) set at the fixed position, and a slipper surface (39) provided on the first rocker arm (24A) to contact the second rocker arm (25A). ) Is formed in an arc shape centered on the third fulcrum (F3), the variable lift valve operating device according to any one of claims 1 to 4 .

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