JP2007224741A - Variable valve gear of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To minimize fluctuation between respective cylinders in a difference from the proper state of a valve characteristic of an engine valve, when a control shaft thermally expands in the axial direction. <P>SOLUTION: When rotatively driving the control shaft 16 inserted into a pipe-shaped rocker shaft 15, a slider 26 engaged with the control shaft 16 via a pinion gear 34 is displaced in the axial direction of the shaft 16, and a valve lift variable mechanism is driven. The control shaft 16 is formed by mutually connecting a plurality of shaft materials 16a arranged with respective cylinders so as to be relatively movable in the axial direction and integrally rotatable in the peripheral direction. The rocker shafts 15 are arranged in a plurality pieces with respective shaft materials 16a, and supports the pinion gear 34. The shaft materials 16a of the respective cylinders and the rocker shafts 15 are positioned in the axial direction in a state of having a clearance C by a positioning pin 48. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a variable valve operating apparatus for an internal combustion engine.

  In an internal combustion engine such as an automobile engine, each cylinder has a variable valve mechanism that makes variable the valve characteristics of engine valves such as an intake valve and an exhaust valve, for example, the maximum lift amount of the valve and the operating angle of a cam that drives the valve. There has been proposed one that is provided in a cylinder head for driving each of these variable valve mechanisms according to the engine operating state (see Patent Document 1).

  Such a variable valve mechanism includes an input arm that is pushed by a rotating cam and swings about a shaft, and an output arm that swings about the shaft based on the swing of the input arm and lifts the engine valve. And a cylindrical slider which is arranged in a state of penetrating the arms and is connected to both arms by gears having different inclination directions of the tooth traces.

  A common control shaft common to all cylinders is inserted into the slider of each variable valve mechanism, and the slider of each variable valve mechanism is engaged with this single control shaft by an engaging member. Are combined. The end of the control shaft is connected to, for example, a hydraulic actuator, and the control shaft is driven in the axial direction by the actuator. On the other hand, the input arm and the output arm of each variable valve mechanism are restricted in displacement in the axial direction of the control shaft by a standing wall portion formed in the cylinder head.

The slider of each variable valve mechanism is displaced in the axial direction with respect to the input arm and the output arm by driving the control shaft in the axial direction, thereby swinging the input arm and the swing arm by the action of the gear. The relative position in the direction is changed, and the valve characteristics such as the maximum lift amount and the working angle are simultaneously changed in each cylinder.
JP 2001-263015 A

  As described above, if all the variable valve gears of each cylinder are driven based on the drive of one control shaft in the axial direction, the valve characteristics of each cylinder can be changed simultaneously. It becomes. However, when the control shaft thermally expands in the axial direction during operation of the internal combustion engine, it is inevitable that the following problems occur due to this.

  The end portion of the control shaft is connected to the actuator, and when the control shaft is thermally expanded in the axial direction, the shaft extends in the axial direction with reference to the end portion. When the control shaft extends in the axial direction due to thermal expansion in this way, the engagement position of the slider by the engaging member with respect to the shaft shifts from the appropriate position in the axial direction by the thermal expansion, and accordingly the slider also moves in the axial direction. Sneak away.

  During the thermal expansion of the control shaft, the standing wall portion that restricts the displacement of the input arm and the output arm in the axial direction is also thermally expanded, whereby the input arm and the output arm are also displaced in the axial direction. Here, if the displacement in the axial direction of the input arm and the output arm due to the thermal expansion of the standing wall is equal to the displacement in the axial direction of the slider due to the thermal expansion of the control shaft, the axial direction relative to the input arm and the output arm There is no change in the relative position of the slider, and the valve characteristic does not change from the proper state.

  However, the standing wall is made of an aluminum alloy or the like with an emphasis on weight reduction of the internal combustion engine, and the control shaft is made of a different material from the standing wall and the control shaft. The coefficient of thermal expansion of both is not the same. Further, while the standing wall portion is fixed to the cylinder head, the control shaft has only its end connected to the actuator. As described above, since the thermal expansion coefficient and the installation mode of the two are different, it is unlikely that the input arm, the output arm, and the slider are displaced by the same amount in the axial direction when the standing wall portion and the control shaft are thermally expanded. More specifically, the displacement of the input arm and the output arm in the axial direction due to the thermal expansion of the standing wall portion is slight, whereas the displacement of the slider in the axial direction due to the thermal expansion of the control shaft can be large. High nature.

  Accordingly, when the control shaft is thermally expanded and the slider engaged with the shaft via the engaging member is displaced from the proper position in the axial direction, the slider, the input arm, and the output arm are relative to each other in the axial direction. As the position changes, the valve characteristics deviate from the proper state. However, if the deviation from the appropriate state of the valve characteristics is a cylinder in each cylinder, the valve characteristics can be made appropriate in all cylinders by driving the control shaft in the axial direction in consideration of the deviation. It will be possible.

  However, the amount of thermal expansion in the axial direction with the end portion of the control shaft as a reference is larger as the portion is farther from the end portion. This is because as the distance from the end of the control shaft increases, the amount of the control shaft between the ends increases.

  In this way, the portion of the control shaft that is farther from the end portion has a larger amount of thermal expansion in the axial direction with respect to the end portion, so that the cylinder that is located farther from the end portion is more controlled. The deviation in the axial direction from the appropriate value of the slider engaging position by the engaging member with respect to the shaft becomes large. As a result, the closer the cylinder is to the end, the greater the displacement in the axial direction from the appropriate position of the slider, and the greater the change in the relative position in the axial direction with respect to the input arm and output arm of the slider. For this reason, the deviation of the valve characteristic of the engine valve from the appropriate state becomes large. Therefore, when thermal expansion in the axial direction occurs in the control shaft, the deviation of the valve characteristics from the appropriate state greatly varies from cylinder to cylinder.

  In this case, by driving the control shaft in the axial direction so as to eliminate the above-mentioned deviation in any of the cylinders, the valve characteristics can be made to be in an appropriate state only for the cylinder, but the valve characteristics are in an appropriate state in the other cylinders. Therefore, it is inevitable that the combustion state in the cylinder will deteriorate.

  The present invention has been made in view of such circumstances, and its purpose is to provide a variation among the cylinders in the deviation of the valve characteristic of the engine valve from the appropriate state when the control shaft is thermally expanded in the axial direction. It is an object of the present invention to provide a variable valve operating apparatus for an internal combustion engine that can suppress the above-mentioned low.

In the following, means for achieving the above object and its effects are described.
In order to achieve the above object, according to the first aspect of the present invention, there is provided a slider provided for each cylinder of the internal combustion engine and used for changing the valve characteristic of the engine valve, and the slider via the engaging member. A variable valve operating system for an internal combustion engine that varies the valve characteristics of the engine valve of each cylinder by driving the control shaft and displacing the slider in the axial direction of the shaft The control shaft is formed by connecting a plurality of shaft members so that they can move relative to each other in the axial direction and integrally rotate in the circumferential direction, and is driven to rotate in the rotational direction around the axis by a motor. The engagement member is configured to displace the slider in the axial direction based on rotation of the shaft member, The number of shaft member, in a state with a clearance between one another, and summarized in that the positioning is made as to the axial direction by the positioning pin.

  According to the above configuration, the control shaft is formed by a plurality of shaft members, and when the shaft is thermally expanded, each shaft member extends in the axial direction with reference to the position of the positioning pin, and accordingly, the clearance between the shaft members is increased. Becomes smaller. When the shaft material extends in the axial direction due to thermal expansion, the engagement position of the slider by the engaging member with respect to the coaxial material is displaced in the axial direction, and the slider is displaced in the axial direction from the appropriate position. It will deviate from the state. Here, since the axial length of each shaft member is shorter than the axial length of the entire control shaft, the maximum distance from the reference position of thermal expansion to the engagement position in one shaft member, that is, The maximum distance from the position of the positioning pin to the engagement position is kept short. The shorter the distance from the reference position for thermal expansion to the engagement position, the smaller the deviation of the slider from the proper position during thermal expansion in the axial direction, and the smaller the deviation of the valve characteristic from the proper state. Therefore, the control shaft is formed of a plurality of shaft members, and the maximum distance from the reference position of the thermal expansion to the engagement position is kept short, so that the deviation of the valve characteristic from the appropriate state at the time of thermal expansion is between each cylinder. The variation in the can be suppressed small. In addition, when the control shaft is rotationally driven so as to eliminate the deviation of the valve characteristic from the appropriate state in any cylinder, it is possible to suppress the deterioration of the combustion state due to the valve characteristic greatly deviating from the appropriate state in the other cylinders. .

  Further, the variable valve mechanism is driven through the rotational drive of the control shaft. Here, if the variable valve mechanism is driven by driving the control shaft in the axial direction, the rotational motion of the motor is converted between the motor and the control shaft into a linear motion of the control shaft. Therefore, there is a problem that the structure on the motor side becomes complicated by the provision of the rotation / linear motion conversion mechanism. However, by driving the variable valve mechanism through the rotation drive of the control shaft, it is only necessary to transmit the rotation of the motor to the control shaft as it is, and the above-described problem that the structure of the motor side becomes complicated is generated. It can be avoided.

The invention according to claim 2 is the gist of the invention according to claim 1, wherein the shaft member is provided for each cylinder of the internal combustion engine.
According to the above configuration, since the shaft member is provided corresponding to each cylinder, the axial length of each shaft member can be shortened, and the shaft member is coaxial from the reference position of thermal expansion. The engagement position of the slider with the engagement member with respect to the material, in other words, the distance from the position of the positioning pin to the engagement position can be kept small. Therefore, the displacement of the above engagement position from the proper position at the time of thermal expansion of each shaft member, in other words, the displacement from the proper position of the slider can be kept small, and as a result, the deviation of the valve characteristic from the proper state at the time of thermal expansion. The variation between the cylinders can be kept small.

According to a third aspect of the present invention, in the second aspect of the present invention, the distance between the positioning pin and the engaging member in a plurality of shaft members is the same between the shaft members.
According to the above configuration, during the thermal expansion of the shaft member, the displacement from the proper position of the slider engagement position by the engagement member with respect to the coaxial material is made equal in each cylinder, and the displacement from the proper position of the slider is also equal in each cylinder. can do. Accordingly, it is possible to prevent the deviation of the valve characteristic from the appropriate state during thermal expansion from varying among the cylinders, and to make the deviation coincide between the cylinders. Further, by rotating the control shaft so as to eliminate the deviation of the valve characteristic from the appropriate state due to the deviation, the valve characteristic can be brought into an appropriate state in all the cylinders.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the engagement member meshes with a male screw formed on an outer peripheral surface of the shaft member, and the coaxial member rotates when the coaxial member rotates. The slider was pushed in the axial direction.

  According to the above configuration, when the shaft is rotated by the motor, the engaging member that meshes with the male screw of the shaft presses the slider in the axial direction, and the slider is displaced in the axial direction to change the valve characteristics. Thus, the rotational movement of the shaft member can be accurately converted into the linear movement of the slider by the engaging member.

  The invention according to claim 5 is the invention according to claim 4, further comprising a plurality of pipe-like rocker shafts that are provided for each of the shaft members and rotatably support the coaxial material, and each of the rocker shafts. Is formed of the same material as the shaft material, arranged in series in the axial direction of the shaft material and having a clearance between them, and the positioning pin is coaxial with the shaft material. The rocker shaft corresponding to the material is positioned in the axial direction, and the engaging member is a pinion gear having a radial direction of the shaft material as a direction in which the central axis extends, and rotates about the central axis It is supported by the rocker shaft so as to be able to be engaged, and meshes with a male screw of the shaft member and a gear surface formed on the slider.

  According to the above configuration, when the shaft is rotated by the motor, the pinion gear that meshes with the male screw formed on the outer peripheral surface of the shaft is rotated, and the slider that meshes with the pinion gear is pushed by the pinion gear in the axial direction of the shaft. Thus, the rotational motion of the shaft member can be accurately converted into the linear motion of the slider by the pinion gear. Further, when the shaft material thermally expands in the axial direction with the positioning pin as the reference position, the rocker shaft on which the pinion gear is supported also thermally expands in the axial direction with the positioning pin as the reference position, and the slider of the slider by the pinion gear with respect to the shaft material. The engaging position is displaced from the appropriate position in the axial direction. As a result, the slider is displaced from the proper position in the axial direction, and the valve characteristic is deviated from the proper state. However, the variation between the cylinders can be suppressed. Furthermore, since the thermal expansion coefficient of the rocker shaft on which the pinion gear is supported is equal to the thermal expansion coefficient of the shaft material, the axial direction of the male screw of the shaft material and the pinion gear of the rocker shaft during the thermal expansion of the rocker shaft and the shaft material. It is suppressed that the relative position of changes. Here, if the relative position changes, the pinion gear rotates by an amount corresponding to the change, and the slider is displaced in the axial direction so that the valve characteristics are shifted. However, since the change in the relative position is suppressed, occurrence of such a deviation in valve characteristics can be suppressed.

Hereinafter, an embodiment in which the present invention is applied to an in-line four-cylinder engine for an automobile will be described with reference to FIGS.
FIG. 1 is an enlarged cross-sectional view showing a structure around a cylinder head 2 in a predetermined cylinder among the first to fourth cylinders of the engine 1. In this engine 1, a combustion chamber 6 is defined by a cylinder head 2, a cylinder block 3, and a piston 5, and an intake passage 7 and an exhaust passage 8 are connected to the combustion chamber 6 in a state of being branched into two. (Only one is shown in FIG. 1). The intake passage 7 and the combustion chamber 6 are connected and cut off by the opening / closing operation of the intake valve 9, and the exhaust passage 8 and the combustion chamber 6 are connected and cut off by the opening / closing operation of the exhaust valve 10. Two intake valves 9 and two exhaust valves 10 are provided for each cylinder.

  The cylinder head 2 is provided with an intake camshaft 11 and an exhaust camshaft 12 for driving the intake valve 9 and the exhaust valve 10. The intake camshaft 11 and the exhaust camshaft 12 rotate by transmission of rotation from the crankshaft of the engine 1. The intake camshaft 11 and the exhaust camshaft 12 are provided with an intake cam 11a and an exhaust cam 12a, respectively. The intake valve 9 and the exhaust valve 10 are opened and closed through integral rotation of the intake cam 11a and the exhaust cam 12a with the intake cam shaft 11 and the exhaust cam shaft 12.

  The engine 1 includes a variable valve lift mechanism that varies the maximum lift amount of the intake valve 9 and the operating angle of the intake cam 11a as a variable valve lift mechanism that varies the valve characteristics of the engine valves such as the intake valve 9 and the exhaust valve 10. 14 is provided between the intake cam 11 a and the intake valve 9. Through the driving of the variable valve lift mechanism 14, for example, the maximum lift amount and the operating angle are controlled to increase as the engine operation state that requires a larger intake air amount is reached. This is because the larger the maximum lift amount and the operating angle, the more efficiently the air is sucked into the combustion chamber 6 from the intake passage 7 and the above-described requirements regarding the intake air amount can be satisfied.

Next, the detailed structure of the variable valve lift mechanism 14 will be described.
The variable valve lift mechanism 14 includes an input arm 17 that is pushed by the rotating intake cam 11 a and swings about the axes of the rocker shaft 15 and the control shaft 16 extending in parallel with the intake cam shaft 11, and the input arm 17 And an output arm 18 that swings about the axis based on the swing. A roller 19 is rotatably attached to the input arm 17. The input arm 17 is urged toward the intake cam 11a by the coil spring 20 so that the roller 19 is pressed against the intake cam 11a. Further, the output arm 18 is pressed against the rocker arm 21 when swinging, and lifts the intake valve 9 via the rocker arm 21.

  The base end portion of the rocker arm 21 is supported by a lash adjuster 22, and the distal end portion of the rocker arm 21 is in contact with the intake valve 9. The rocker arm 21 is urged toward the output arm 18 by the valve spring 24 of the intake valve 9, whereby a roller 23 rotatably supported between the base end portion and the distal end portion of the rocker arm 21 is applied to the output arm 18. It is pressed.

  Therefore, when the input arm 17 and the output arm 18 swing based on the rotation of the intake cam 11a, the output arm 18 lifts the intake valve 9 via the rocker arm 21, and the intake valve 9 is opened and closed. In the variable valve lift mechanism 14, the maximum lift amount of the intake valve 9 and the intake cam 11 a with respect to the intake valve 9 are changed by changing the relative positions of the input arm 17 and the output arm 18 in the swing direction. The working angle is variable. That is, as the input arm 17 and the output arm 18 are brought closer to each other in the swing direction, the maximum lift amount of the intake valve 9 and the operating angle of the intake cam 11a become smaller. Conversely, as the input arm 17 and the output arm 18 are separated from each other in the swinging direction, the maximum lift amount of the intake valve 9 and the operating angle of the intake cam 11a increase.

  Next, a structure for attaching the variable valve lift mechanism 14 to the cylinder head 2 and a structure for attaching the rocker shaft 15 and the control shaft 16 used for driving the variable valve lift mechanism 14 to the cylinder head 2 will be described with reference to FIGS. This will be described with reference to FIG.

FIG. 2 is a plan view of the cam carrier 41 formed on the upper portion of the cylinder head 2 as viewed from above.
The cam carrier 41 is provided with a plurality of standing wall portions 45 corresponding to each cylinder so as to be parallel to each other. These standing wall portions 45 are formed of a lightweight material such as an aluminum alloy in order to reduce the weight of the internal combustion engine. The variable valve lift mechanism 14 is disposed between the standing wall portions 45 corresponding to the cylinders of the internal combustion engine. The rocker shaft 15 and the control shaft 16 used for driving the variable valve lift mechanism 14 pass through the variable valve lift mechanisms 14 and the standing wall portions 45. The variable valve lift mechanisms 14 are supported by the standing wall portions 45 via the rocker shaft 15. Further, the input arm 17 and the output arm 18 of the mechanism 14 are sandwiched between the standing wall portions 45, and the vertical wall portions 45 allow the displacement of the input arm 17 and the output arm 18 in the axial direction of the rocker shaft 15. It is regulated.

  The cam carrier 41 is provided with a plurality of standing wall portions 45 corresponding to each cylinder so as to be parallel to each other. Between the standing wall portions 45, the variable valve lift mechanism 14 is disposed corresponding to each cylinder of the internal combustion engine. The rocker shaft 15 and the control shaft 16 used for driving the variable valve lift mechanism 14 pass through the variable valve lift mechanisms 14 and the standing wall portions 45. The variable valve lift mechanisms 14 are supported by the standing wall portions 45 via the rocker shaft 15.

  The rocker shaft 15 is formed in a pipe shape, and the control shaft 16 is rotatably supported inside the rocker shaft 15. The control shaft 16 connects a plurality of shaft members 16a provided for each cylinder so that they can move relative to each other in the axial direction in a state where they are in series in the axial direction and can rotate integrally in the circumferential direction. It is formed by. Further, the rocker shaft 15 is provided for each shaft member 16a, and is arranged so as to be in series with each other in the axial direction of the shaft member 16a and relatively movable in the axial direction. The plurality of rocker shafts 15 are formed of the same material as the shaft member 16a. Specifically, both the rocker shaft 15 and the shaft member 16a are formed using a high-strength material such as an iron-based material with an emphasis on ensuring the necessary strength.

  In the control shaft 16 formed by a plurality of shaft members 16a, the base end portion (the left end portion in the figure) is connected to the motor 47 via a gear or the like, and the rotation of the motor 47 causes the gear or the like to rotate. It is rotationally driven by being transmitted through. The variable valve lift mechanism 14 of each cylinder is driven through the rotational drive of the control shaft 16 to change the relative position of the input arm 17 and the output arm 18 in the swinging direction.

  Here, it is conceivable that the rotational motion of the motor 47 is converted into a linear motion in the axial direction of the control shaft 16 by a rotational linear motion conversion mechanism or the like, and the valve lift variable mechanism is made through the linear motion of the control shaft 16. In this case, the structure on the motor 47 side becomes complicated by the necessity to provide the rotation / linear motion conversion mechanism and the like. However, if the variable valve lift mechanism 14 is driven through the rotational drive of the control shaft 16 as in this embodiment, it is only necessary to transmit the rotation of the motor 47 to the control shaft 16 as it is. It is possible to avoid the occurrence of a problem that the structure on the side becomes complicated.

  FIG. 3 is a cross-sectional view showing a connection structure between the shaft members 16 a forming the control shaft 16 and a structure for attaching the shaft members 16 a and the rocker shaft 15 to the standing wall portion 45.

  The standing wall portion 45 is formed by attaching a cam cap 43 made of a lightweight material such as an aluminum alloy to the upper side of a bearing 42 made of a lightweight material such as an aluminum alloy formed on the cylinder head 2 with a bolt 44. . A hole 46 is formed in the lower surface of the cam cap 43, and a positioning pin 48 for inserting the rocker shaft 15 and the shaft member 16 a of the control shaft 16 is inserted into the hole 46. The rocker shaft 15 and the control shaft 16 penetrate between the bearing 42 and the cam cap 43 in the standing wall portion 45.

  In the shaft member 16a of the control shaft 16, a protrusion 49 is formed at one end (right end in the figure), and a slit 50 for inserting the protrusion 49 is formed at the other end (left end in the figure). Is formed. The detailed shapes of the protrusion 49 and the slit 50 are shown in FIGS. 4 and 5, respectively. As shown in FIG. 4, the protrusion 49 is formed in a plate shape extending in the radial direction of the shaft member 16a, and in the vicinity of the protrusion 49 of the shaft member 16a in the circumferential direction of the outer peripheral surface of the coaxial member 16a. A positioning groove 51 extending in an annular shape is formed. Further, as shown in FIG. 5, the slit 50 is also formed to extend in the radial direction of the shaft member 16a.

  As shown in FIG. 3, each shaft member 16 a is relatively moved in the coaxial line direction in a state of being in series in the axial direction by inserting the protrusion 49 of the shaft member 16 a into the slit 50 of the other shaft member 16 a. It is connected so that it can rotate integrally in the circumferential direction. A rocker shaft 15 is attached to the outer peripheral surface of each shaft member 16a so as to be movable relative to the shaft member 16a in the axial direction and the circumferential direction. Accordingly, the rocker shafts 15 are arranged in series in the axial direction of the shaft member 16a. A positioning hole 52 is formed in a portion of each rocker shaft 15 corresponding to the positioning groove 51 of the shaft member 16a.

  The cam cap 43 is inserted so that the positioning pin 48 is inserted into the positioning groove 51 and the positioning hole 52 in a state where the rocker shaft 15 and the shaft member 16 a are aligned so that the positioning groove 51 and the positioning hole 52 communicate with each other. Are attached to the bearing 42 with bolts 44, so that the rocker shaft 15 and the shaft member 16 a are positioned by the positioning pins 48. More specifically, the shaft members 16a are positioned in the axial direction by the positioning pins 48 with a clearance C between them. The rocker shafts 15 are also positioned in the axial direction by the positioning pins 48 with a clearance C between them. The size of the clearance C is set to a size capable of absorbing the thermal expansion of the rocker shaft 15 and the shaft member 16a.

  The lengths of the shaft member 16a and the rocker shaft 15 and the positions of the positioning pins 48, the positioning holes 52 and the positioning grooves 51 are determined when the rocker shaft 15 and the shaft member 16a are positioned by the positioning pins 48 as described above. It is determined so that the clearance C can be formed between the shaft members 16 a and between the rocker shafts 15. Further, when the control shaft 16 rotates with the shaft member 16 a positioned by the positioning pin 48, the rotation is allowed by the relative movement of the positioning pin 48 and the positioning groove 51 in the rotational direction.

Next, the internal structure of the variable valve lift mechanism 14 will be described with reference to FIGS.
FIG. 6 is a cutaway perspective view showing the inner structure of the input arm 17 and the output arm 18 in the variable valve lift mechanism 14.

  The variable valve lift mechanism 14 includes a cylindrical slider 26 disposed inside the input arm 17 and the output arm 18. The rocker shaft 15 is inserted into the slider 26, and the control shaft 16 is inserted into the rocker shaft 15. When the control shaft 16 rotates, the rotational motion is converted into linear motion of the slider 26 in the axial direction of the rocker shaft 15 by a pinion gear (not shown in FIG. 6) attached to the rocker shaft 15. On the outer wall of the slider 26, an input gear 27a having a helical spline 27 is fixed at the center in the longitudinal direction, and an output gear 29a having a helical spline 29 is fixed at both ends in the longitudinal direction.

  On the other hand, as shown in FIG. 7, an annular inner gear 28 a having a helical spline 28 is formed on the inner wall of the input arm 17, and an annular inner tooth having a helical spline 30 is formed on the inner wall of the output arm 18. A gear 30a is formed. The internal gear 28a of the input arm 17 is meshed with the input gear 27a (FIG. 6) of the slider 26, and the internal gear 30a of the output arm 18 is meshed with the output gear 29a of the slider 26 (FIG. 6). The helical splines 27 and 28 and the helical splines 29 and 30 have different inclination angles, for example, the inclination directions of the tooth traces are opposite to each other.

  When the slider 26 is displaced in the axial direction of the rocker shaft 15 based on the rotation of the control shaft 16, the swinging direction of the input arm 17 and the output arm 18 is caused by the meshing of the helical splines 27 and 29 and the helical splines 28 and 30. The relative position about is changed. Specifically, as the slider 26 is displaced in the direction of arrow L in FIG. 6, the relative positions of the input arm 17 and the output arm 18 in the swing direction are changed so as to approach each other. The relative positions are changed so as to be separated from each other as they are displaced. Through the change of the relative position of the input arm 17 and the output arm 18 in the swing direction, the maximum lift amount of the intake valve 9 and the working angle of the intake cam 11a when the output arm 18 swings due to the rotation of the intake cam 11a. Is variable.

FIG. 8 is a cross-sectional view showing the internal structure of the input arm 17, the output arm 18, the slider 26, the rocker shaft 15, and the like.
As shown in the figure, a long hole 33 extending in the axial direction of the shaft 15 is formed in the rocker shaft 15, and the rotational movement of the shaft member 16 a is carried in the long hole 33 to the axis of the rocker shaft 15 of the slider 26. A pinion gear 34 is provided for conversion into linear motion in the direction. The pinion gear 34 is provided such that its central axis extends in the radial direction of the shaft member 16a. Further, the distance from the positioning pin 48 to the pinion gear 34 is made equal for each cylinder. That is, the positions of the pinion gear 34, the positioning hole 52, and the like are determined so that the distance is equal for each cylinder. FIG. 9 is a plan view of the pinion gear 34 as viewed from above. As shown in the figure, both end portions of the center shaft 35 of the pinion gear 34 are inserted from above into recesses 36 formed in the opposing wall surfaces of the elongated holes 33, whereby the pinion gear 34 is rotated around the center axis by the recesses 36. Is rotatably supported.

  As shown in FIG. 8, a male screw 32 that meshes with the pinion gear 34 is formed at a portion corresponding to the pinion gear 34 on the outer peripheral surface of the shaft member 16 a. Therefore, when the shaft member 16a (control shaft 16) is driven to rotate, the pinion gear 34 that meshes with the male screw 32 rotates around its central axis. In addition, a gear surface 38 is formed on the inner peripheral surface of the slider 26 in the center in the longitudinal direction. The gear surface 38 includes a gear 37 that meshes with the pinion gear 34 and is aligned in the axial direction of the rocker shaft 15. The gear 37 is movable relative to the pinion gear 34 in the circumferential direction of the rocker shaft 15. When the pinion gear 34 rotates around its central axis, the gear 37 on the gear surface 38 is pushed in the axial direction of the rocker shaft 15 by the pinion gear 34, and the slider 26 is displaced in the axial direction.

  In this embodiment, when the shaft member 16a (control shaft 16) rotates forward and the pinion gear 34 rotates rightward around its central axis, the slider 26 is displaced in the direction of arrow H in the figure. Further, when the shaft member 16a rotates in the reverse direction and the pinion gear 34 rotates to the left around the central axis, the slider 26 is displaced in the direction of arrow L in the drawing. For this reason, during the forward rotation of the shaft member 16a, the relative positions of the input arm 17 and the output arm 18 in the swing direction are changed so as to be separated from each other, and the maximum lift amount of the intake valve 9 and the action of the intake cam 11a. The corner becomes large. Further, when the shaft member 16a rotates in the reverse direction, the relative positions of the input arm 17 and the output arm 18 in the swing direction are changed so as to approach each other, and the maximum lift amount of the intake valve 9 and the operating angle of the intake cam 11a. Becomes small.

  When the intake valve 9 is driven to open and close by swinging the input arm 17 and the output arm 18 by the rotation of the intake cam 11a, the slider 26 also moves the rocker shaft 15 as the input arm 17 and output arm 18 swing. It is displaced (rotated) in the circumferential direction with respect to the outer peripheral surface of. At this time, the gear 37 on the gear surface 38 of the slider 26 is slidable in the circumferential direction (direction perpendicular to the paper surface of FIG. 8) with respect to the pinion gear 34, so that the displacement of the slider 26 is not hindered. .

  Further, when the gear 37 of the slider 26 slides on the pinion gear 34 as described above, the pinion gear 34 tends to be displaced in the circumferential direction of the rocker shaft 15 due to the frictional force between the gear 37 and the pinion gear 34. If the pinion gear 34 is displaced in the circumferential direction of the rocker shaft 15 by the frictional force, the pinion gear 34 rotates around its central axis because the pinion gear 34 meshes with the male screw 32 of the shaft 16a. 26 shifts from the proper position in the axial direction of the rocker shaft 15. As a result, the relative position of the input arm 17 and the output arm 18 in the swing direction also changes, and the maximum lift amount of the intake valve 9 and the operating angle of the intake cam 11a deviate from the proper state. However, since the displacement in the circumferential direction of the pinion gear 34 due to the frictional force is regulated by the recess 36 formed in the opposing surface of the elongated hole 33, the above-described deviation of the maximum lift amount and the working angle from the proper state. Is suppressed.

  Next, the effect of adopting the structure in which the shaft member 16a (control shaft 16) is engaged with the slider 26 and the structure in which the slider 26 is moved in the axial direction of the rocker shaft 15 in this embodiment will be compared with the conventional one. However, description will be made with reference to FIGS. FIG. 10 schematically shows a conventional control shaft and the like, and FIG. 11 schematically shows the control shaft 16 and the rocker shaft 15 and the like of the present embodiment.

  Conventionally, the slider of the variable valve lift mechanism of each cylinder is engaged with one control shaft via an engaging member. The engagement position of the slider with respect to the control shaft by the engagement member for each cylinder is indicated by a black triangle in FIG. In this case, the slider engaged with the shaft via the engaging member is displaced in the axial direction by displacing the control shaft in the axial direction by the actuator. As a result, the relative positions of the input arm and the output arm in the swinging direction of each cylinder are simultaneously changed in each cylinder, and the valve characteristics such as the maximum lift amount of the intake valve and the working angle of the intake cam are simultaneously changed in each cylinder. Become.

  By the way, when the control shaft expands in the axial direction during operation of the internal combustion engine, when the shaft extends in the axial direction with reference to the end connected to the actuator as shown in FIG. The engagement position is shifted from the position indicated by the black triangle in FIG. 10A to the position indicated by the black triangle in FIG. When the slider deviates from the proper position in the axial direction due to the deviation of the engagement position from the proper position, the relative position of the input arm and the output arm in the swing direction is deviated, resulting in the valve characteristics from the proper state. The deviation is as described in the column [Problems to be solved by problems].

  The amount of deviation of the engagement position indicated by the black triangle in the figure from the appropriate position accompanying the thermal expansion becomes larger as the cylinder is farther from the end of the control shaft. More specifically, assuming that the shift amounts of the first cylinder to the fourth cylinder are respectively “z1”, “z2”, “z3”, and “z4”, the shift amounts z1 to z4 are “z1 <z2 <z3 <z4”. ”. This is because the distance to the engagement position with the end portion as the reference position increases in the order of the first cylinder, the second cylinder, the third cylinder, and the fourth cylinder. That is, assuming that the distances in the first cylinder to the fourth cylinder are “x1”, “x2”, “x3”, and “x4”, respectively, the distances have a relationship of “x1 <x2 <x3 <x4” The amount of material of the control shaft between the end and the engagement position increases in the order of cylinder, second cylinder, third cylinder, and fourth cylinder. As a result, the amount of thermal expansion in the axial direction of the control shaft at the engagement position with the end as the reference position, in other words, the shift amounts z1 to z4 are the first cylinder, the second cylinder, the third cylinder, and the fourth cylinder. It increases in order of the number cylinder.

  Thus, since the displacements z1 to z4 have a relationship of “z1 <z2 <z3 <z4”, the cylinders located farther from the end, that is, the first cylinder, the second cylinder, the third cylinder The deviation from the proper state of the valve characteristics of the intake valve becomes larger in the order of the fourth cylinder. Therefore, when thermal expansion in the axial direction occurs in the control shaft, the deviation of the valve characteristics from the appropriate state greatly varies from cylinder to cylinder. In this case, even if the shift amount in the cylinder can be eliminated by driving the control shaft in the axial direction in consideration of the shift amounts z1 to z4 of any one of the cylinders, the valve characteristics are not obtained in the other cylinders. It will deviate from the proper state, and there is a risk of deteriorating the combustion state in the same cylinder.

  On the other hand, in this embodiment, as shown in FIG. 11A, the control shaft 16 is formed by a plurality of shaft members 16a, and the male screw 32 of each shaft member 16a has a slider 26 relative to the coaxial member 16a. Are engaged with each other. At the time of thermal expansion of the control shaft 16 during operation of the internal combustion engine, each shaft member 16a extends in the axial direction with reference to the position of the positioning pin 48, and accordingly, each shaft member 16a as shown in FIG. The clearance C between them becomes small. Further, when the shaft member 16a (control shaft 16) is thermally expanded in this way, the rocker shaft 15 corresponding to each shaft member 16a is also expanded at the same thermal expansion coefficient as the shaft member 16a. As a result, each rocker shaft 15 also extends in the axial direction with reference to the position of the positioning pin 48, and accordingly, the clearance C between the rocker shafts 15 is also reduced.

  Here, the engagement position of the slider 26 by the pinion gear 34 with respect to the pinion gear 34 of the rocker shaft 15 and the pinion gear 34 in the male screw 32 of the shaft member 16a, in other words, the position of the rocker shaft 15 and the shaft member 16a. Deviation from the proper position due to thermal expansion in the axial direction. The amount of deviation at this time is equal for each cylinder. That is, the displacements Z1 to Z4 in the first cylinder to the fourth cylinder have a relationship of “Z1 = Z2 = Z3 = Z4”. This is because the distance to the pinion gear 34 with the positioning pin 48 as the reference position, in other words, the distance to the portion of the male screw 32 that engages with the pinion gear 34 with the positioning pin 48 as the reference position is made equal for each cylinder. That is, assuming that the distances in the first cylinder to the fourth cylinder are “X1”, “X2”, “X3”, and “X4”, the distances have a relationship of “X1 = X2 = X3 = X4”. For this reason, the amount of material of the rocker shaft 15 between the positioning pin 48 and the pinion gear 34 and the amount of material of the shaft member 16a between the positioning pin 48 and the portion of the male screw 32 that meshes with the pinion gear 34 are as follows. Becomes equal. As a result, the amount of thermal expansion at the position of the pinion gear 34 on the rocker shaft 15 with the positioning pin 48 as the reference position, and the heat at the portion of the shaft member 16a with the positioning pin 48 as the reference position that meshes with the pinion gear 34. The expansion amount, in other words, the shift amounts Z1 to Z4 are equal in each cylinder.

  The displacements Z1 to Z4 occur due to thermal expansion, and when the engagement position of the slider 26 by the pinion gear 34 with respect to the shaft member 16a in each cylinder deviates from the proper position in the axial direction, the slider 26 also deviates from the proper position in the axial direction. As a result, the valve characteristics of each cylinder deviate from an appropriate state. However, since the deviations Z1 to Z4 are prevented from being varied among the cylinders and the deviations Z1 to Z4 are made equal among the cylinders, the deviation from the appropriate state of the valve characteristics should be matched between the cylinders. Can do. Therefore, by rotating the control shaft 16 (shaft member 16a) so as to eliminate the deviation of the valve characteristics from the proper state in each cylinder due to the deviation amounts Z1 to Z4, the valve characteristics are appropriate in all the cylinders. State.

According to the embodiment described in detail above, the following effects can be obtained.
(1) The distances X1 to X4 from the positioning pin 48 to the pinion gear 34, in other words, the distances X1 to X4 from the positioning pin 48 to the portion where the pinion gear 34 in the male screw 32 is meshed are made equal in each cylinder. Therefore, when the rocker shaft 15 and the shaft member 16a are thermally expanded in the axial direction, the displacement amounts Z1 to Z4 of the pinion gear 34 from the proper position with the positioning pin 48 as the reference position, in other words, the male screw with the positioning pin 48 as the reference position. 32, the shift amounts Z1 to Z4 from the proper position of the meshed portion of the pinion gear 34 can be made equal in each cylinder. Therefore, the deviation from the proper state of the valve characteristics due to the deviation is equal in each cylinder, and the valve characteristics can be made appropriate in all the cylinders by rotating the control shaft 16 so as to eliminate the deviation. it can.

  (2) Since the shaft member 16a and the rocker shaft 15 are provided for each cylinder and the shaft member 16a and the rocker shaft 15 are positioned by the positioning pin 48 for each cylinder, the distances X1 to X4 can be kept small. As the distances X1 to X4 become longer, the shift amounts Z1 to Z4 become larger. Therefore, the shift amounts Z1 to Z4 can be made as small as possible by suppressing the distances X1 to X4 as described above. . Accordingly, the deviation of the valve characteristics from the appropriate state due to the deviation amounts Z1 to Z4 can be suppressed as small as possible.

  (3) When the control shaft 16 (shaft member 16 a) rotates, the pinion gear 34 that meshes with the male screw 32 of the shaft member 16 a rotates around its central axis, and the slider 26 that meshes with the pinion gear 34 further rotates the rocker shaft 15. It is pushed in the axial direction. Thus, the rotational movement of the control shaft 16 can be accurately converted into the linear movement of the slider 26 in the axial direction by the pinion gear 34.

  (4) Since the rotational motion of the control shaft 16 is converted into the linear motion of the slider 26 by the pinion gear 34, the valve lift variable mechanism 14 is driven by merely rotating the control shaft 16 by the motor 47 so that the valve characteristics can be varied. can do. Assuming that the variable valve lift mechanism is driven by driving the control shaft in the axial direction, the rotational movement of the motor 47 between the motor 47 and the control shaft is a straight line in the axial direction of the control shaft. It is necessary to provide a rotation / linear motion converting mechanism for converting into motion. An example of such a rotation / linear motion conversion mechanism is a mechanism using a ball screw. Therefore, there is a problem that the structure on the motor 47 side is complicated by the provision of such a rotation / linear motion conversion mechanism. However, if the variable valve lift mechanism 14 is driven through the rotational drive of the control shaft 16, it is only necessary to transmit the rotation of the motor 47 to the control shaft 16 as it is, and the structure on the motor 47 side described above is complicated. It is possible to avoid the occurrence of a problem of becoming.

  (5) The rocker shaft 15 to which the pinion gear 34 is attached is formed of the same material as the shaft member 16 a of the control shaft 16. Therefore, when the shaft member 16a expands in the axial direction with respect to the positioning pin 48, the rocker shaft 15 corresponding to the shaft member 16a also has the same thermal expansion coefficient as the shaft member 16a in the axial direction with respect to the positioning pin 48. Inflate. Therefore, the relative position of the male screw 32 of the shaft member 16a and the pinion gear 34 of the rocker shaft 15 is prevented from changing in the axial direction due to the thermal expansion at this time. If the relative position change described above occurs, the pinion gear 34 rotates by an amount corresponding to the change, so that the slider 26 is displaced in the axial direction and the valve characteristics are shifted. Occurrence can be suppressed.

In addition, the said embodiment can also be changed as follows, for example.
The material of the rocker shaft 15 and the material of the shaft member 16a may be different materials. In this case, during the thermal expansion of the rocker shaft 15 and the shaft member 16a, the relative position of the male screw 32 and the pinion gear 34 in the axial direction of the shaft member 16a changes due to the difference in the coefficient of thermal expansion between them. The valve characteristics are shifted by the change in position. However, such a deviation in valve characteristics occurs equally in each cylinder. Therefore, if the control shaft 16 is rotationally driven so as to eliminate the deviation, the valve characteristics of all the cylinders can be brought into an appropriate state. Even when the material of the rocker shaft 15 and the material of the shaft member 16a are different from each other, materials having similar coefficients of thermal expansion are used as much as possible, and the deviation of the valve characteristics is suppressed to be small. It is preferable.

  The engagement of the slider 26 with the control shaft 16 (shaft member 16 a) can be realized by using an engagement member 61 as shown in FIG. 12 instead of using the pinion gear 34.

  The engaging member 61 penetrates the bush 62 inserted into a groove 64 formed to extend in the circumferential direction on the inner circumferential surface of the slider 26, and penetrates the elongated hole 33 of the rocker shaft 15. And a pin 63 engaged with the male screw 32 in a state. FIG. 13 is a plan view of the engaging member 61 as viewed from the upper side of FIG. The bush 62 of the engaging member 61 and the groove 64 of the slider 26 are relatively movable in the circumferential direction of the slider 26 (vertical direction in the figure). Further, the pin 63 of the engaging member 61 and the elongated hole 33 of the rocker shaft 15 cannot be moved relative to each other in the circumferential direction, and the relative movement of the rocker shaft 15 in the axial direction (left-right direction in the drawing) is not allowed. It is possible.

  Then, when the control shaft 16 (shaft member 16a) shown in FIG. 12 is rotated, the engaging member 61 that meshes with the male screw 32 of the shaft member 16a is displaced along the elongated hole 33 in the axial direction of the shaft member 16a. In order to push the inner surface of the groove 64 at 26 in the axial direction, the slider 26 is displaced in the axial direction to change the valve characteristic. Therefore, in this case, the rotational motion of the shaft member 16a can be accurately converted into the linear motion of the slider 26 by the engaging member 61. Further, since the engaging member 61 is in a relative movable relationship with respect to the rocker shaft 15 in the axial direction, thermal expansion in the axial direction of the rocker shaft 15 does not affect the position of the engaging member 61. Therefore, it is not necessary to provide the rocker shaft 15 for each shaft member 16a. For example, it is possible to provide only one rocker shaft common to all cylinders.

  When the slider 26 swings in the circumferential direction as the input arm 17 and the output arm 18 swing, the groove 64 of the slider 26 slides against the bush 62 of the engaging member 61, The engaging member 61 also tries to swing in the circumferential direction by the frictional force. However, the swing of the engaging member 61 following the swing of the slider 26 is restricted by the inner surface of the elongated hole 33 of the rocker shaft 15.

  The distances X1 to X4 described above are not necessarily matched. Even if the distances X1 to X4 are not matched, the distances X1 to X4 can be kept small if the shaft 16a and the rocker shaft 15 are provided for each cylinder. As a result, the amount of thermal expansion in the axial direction of the shaft member 16a and the rocker shaft 15 can be suppressed to be small, and as a result, the variation between the cylinders in the proper state of the valve characteristics during thermal expansion can be suppressed to be small. . Therefore, when the control shaft 16 is rotationally driven so as to eliminate the deviation of the valve characteristic from the appropriate state in any cylinder, the combustion state is deteriorated due to the valve characteristic remaining largely deviated from the appropriate state in the other cylinders. Can be suppressed. Even when the distances X1 to X4 are not matched, it is preferable to set the distances X1 to X4 as close as possible and to suppress the variation between the cylinders from the appropriate state of the valve characteristics as much as possible.

  The rocker shaft 15 and the shaft member 16a are not necessarily provided for each cylinder. For example, one rocker shaft and shaft material are provided for every two adjacent cylinders such as two cylinders of the first cylinder and the second cylinder and two cylinders of the third cylinder and the fourth cylinder. Also good. Further, among the first cylinder to the fourth cylinder, one rocker shaft and shaft material may be provided corresponding to three consecutive cylinders, and one rocker shaft and shaft material may be provided corresponding to the remaining cylinders. . In this case, all of the distances X1 to X4 in each cylinder cannot be made to coincide with each other, but variations in the distances X1 to X4 can be suppressed to be small, and the valve characteristic at the time of thermal expansion of the rocker shaft and the shaft member can be reduced. It is possible to reduce the variation of the deviation between the cylinders.

-You may form the standing wall part 45, ie, the bearing 42, and the cam cap 43 with materials other than an aluminum alloy.
-You may form the rocker shaft 15 and the shaft material 16a with high strength materials other than a ferrous material.

The expanded sectional view which shows the structure around the cylinder head of the engine to which the variable valve apparatus of this embodiment is applied. The top view which shows the cam carrier of a cylinder head. Sectional drawing which shows the connection structure of each shaft material which forms a control shaft, and the attachment structure to the standing wall part of these shaft materials and a rocker shaft. The expansion perspective view which shows one edge part of the said shaft material. The expansion perspective view which shows the other edge part of the said shaft material. The fracture | rupture perspective view which shows the internal structure of a valve lift variable mechanism. The fracture | rupture perspective view which shows the internal structure of an input arm and an output arm. Sectional drawing which shows internal structures, such as an input arm, an output arm, a slider, and a rocker shaft. The top view which looked at the pinion gear supported by the rocker shaft from the upper direction. (A) And (b) is a schematic diagram which shows the thermal expansion about the axial direction in the conventional control shaft. (A) And (b) is a schematic diagram which shows the thermal expansion about the axial direction in the control shaft and rocker shaft of this embodiment. Sectional drawing which shows the example which implement | achieved engagement with the shaft material and the slider using another engaging member instead of the pinion gear. The top view which looked at the said engagement member periphery from the upper direction.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Cylinder head, 3 ... Cylinder block, 5 ... Piston, 6 ... Combustion chamber, 7 ... Intake passage, 8 ... Exhaust passage, 9 ... Intake valve, 10 ... Exhaust valve, 11 ... Intake camshaft, 11a DESCRIPTION OF SYMBOLS ... Intake cam, 12 ... Exhaust cam shaft, 12a ... Exhaust cam, 14 ... Valve lift variable mechanism, 15 ... Rocker shaft, 16 ... Control shaft, 16a ... Shaft material, 17 ... Input arm, 18 ... Output arm, 19 ... Roller , 20 ... Coil spring, 21 ... Rocker arm, 22 ... Rush adjuster, 23 ... Roller, 24 ... Valve spring, 26 ... Slider, 27 ... Helical spline, 27a ... Input gear, 28 ... Helical spline, 28a ... Internal gear, 29 ... helical spline, 29a ... output gear, 30 ... helical spline, 30a ... inner gear 32 ... Male screw, 33 ... Elongated hole, 34 ... Pinion gear (engagement member), 35 ... Center shaft, 36 ... Recess, 37 ... Gear, 38 ... Gear surface, 41 ... Cam carrier, 42 ... Bearing, 43 ... Cam cap , 44 ... Bolt, 45 ... Standing wall part, 46 ... Hole, 47 ... Motor, 48 ... Positioning pin, 49 ... Projection, 50 ... Slit, 51 ... Positioning groove, 52 ... Positioning hole, 61 ... Engaging member, 62 ... Bush, 63 ... pin, 64 ... groove.

Claims (5)

A slider provided for each cylinder of the internal combustion engine and used for changing the valve characteristics of the engine valve; and a control shaft engaged with the slider via an engagement member. In a variable valve operating apparatus for an internal combustion engine that drives and displaces the slider in the axial direction of the shaft to vary the valve characteristics of the engine valve of each cylinder.
The control shaft is formed by connecting a plurality of shaft members so that they can move relative to each other in the axial direction and integrally rotate in the circumferential direction, and is rotationally driven by a motor in a rotational direction around the axis. There,
The engaging member is for displacing the slider in the axial direction based on rotation of the shaft member.
The variable valve operating apparatus for an internal combustion engine, wherein the plurality of shaft members are positioned in the axial direction by a positioning pin in a state having a clearance between them.   The variable valve operating apparatus for an internal combustion engine according to claim 1, wherein the shaft member is provided for each cylinder of the internal combustion engine.   The variable valve operating apparatus for an internal combustion engine according to claim 2, wherein the distance between the positioning pin and the engaging member in the plurality of shaft members is equal between the shaft members.   4. The internal combustion engine according to claim 1, wherein the engagement member meshes with a male screw formed on an outer peripheral surface of the shaft member, and pushes the slider in the axial direction when the coaxial member rotates. Variable valve gear for engine. The variable valve operating apparatus for an internal combustion engine according to claim 4,
A plurality of pipe-like rocker shafts provided for each shaft member and rotatably supporting a coaxial material inside,
Each of the rocker shafts is formed of the same material as the shaft member, and is arranged in series in the axial direction of the shaft member and having a clearance between them.
The positioning pin performs positioning in the axial direction of the rocker shaft corresponding to a coaxial material together with the shaft material,
The engaging member is a pinion gear having a radial direction of the shaft member extending in a central axis direction, and is supported by the rocker shaft so as to be rotatable around the central axis line. A variable valve operating apparatus for an internal combustion engine, which meshes with a gear surface formed on the slider.

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