JP2006291819A - Variable valve train for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inhibit the maximum lift amount of an engine valve relative to the axial displacement of a slider, and the operating angle change mode of an intake cam resulting from the thermal expansion of shims, from being in inadequate conditions. <P>SOLUTION: The axial positions of arms 17, 18 have a great influence on the maximum lift amount of the intake valve relative to the axial displacement and the operating angle change mode of the intake cam. The shim 46 and a shim 50 are therefore provided between a rising wall portion 45 and the arm 18 and between the arms 17, 18, respectively. The shims 46, 50 are properly replaced with those which are different in axial thickness. The axial positions of the arms 17, 18 are thereby adjusted into adequate positions to correct the maximum lift amount and the operating angle change mode. These shims 46, 50 are formed of ceramic which has almost no thermal expansion. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

  In an internal combustion engine such as an automobile engine, a variable valve that makes the maximum lift amount of an engine valve and the operating angle of a cam that drives the valve variable so that optimum intake characteristics can be obtained over the entire engine operating range. A mechanism that includes a mechanism and drives the mechanism in accordance with the engine operating state has been proposed (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 fitted on the outer peripheral surface of the shaft that becomes the swing center of the arms. This slider is in a state of penetrating the input arm and the output arm, and these arms are connected to the slider by gears having different inclination directions of the teeth. When the slider is moved in the axial direction, the relative position of the input arm and the swing arm in the swinging direction is changed by the action of the gear, and the maximum lift amount and the operating angle are changed.

In the variable valve mechanism, the shaft is supported by a plurality of standing wall portions arranged in parallel with the cylinder head, and the input arm and the output arm are disposed between the standing wall portions. The maximum lift amount of the engine valve and the operating angle of the intake cam are greatly affected by the axial positions of the input arm and output arm. Therefore, if the arms are not properly positioned in the axial direction, the maximum lift with respect to the axial displacement of the slider will be described. The change mode of the amount and the working angle is in an inappropriate state. For this reason, by providing a shim between the arm and the standing wall part and between each arm and appropriately replacing the shim with a different axial thickness, the maximum lift amount with respect to the directional displacement of the slider and The axial position of each arm is adjusted to an appropriate position so that the change of the operating angle is in an appropriate state.
JP 2001-263015 A

  By the way, the shim is often formed using an iron-based material from the viewpoint of ease of processing and strength, and due to the use of such a material, thermal expansion during engine operation is inevitable. The thermal expansion in the axial direction of the shim increases as the axial thickness of the shim increases. Therefore, as a result of adjusting the position of each arm in the axial direction by the shim, when the axial thickness of each shim between the arm and the standing wall portion and between each arm is different, The thermal expansion in the axial direction during engine operation differs greatly for each shim.

  Here, regarding the thermal expansion in the axial direction of each shim, assuming that there is no variation for each shim and that each thermal expansion is uniform, the axial position of each arm and the relative position between the arms due to the thermal expansion. The effect of is minimal. However, as described above, when variation occurs in the thermal expansion in the axial direction for each shim, the influence of the thermal expansion on the axial position of each arm and the relative position between the arms cannot be ignored. That is, as the variation in the thermal expansion increases, the deviation of the axial position of each arm from the proper state increases, and the deviation of the relative position between the arms from the proper state also increases. As a result, the change mode of the maximum lift amount and the operating angle with respect to the displacement in the axial direction of the slider is in an inappropriate state.

  The present invention has been made in view of such circumstances, and its purpose is to change the maximum lift amount of the engine valve and the working angle of the intake cam with respect to the axial displacement of the slider due to the thermal expansion of the shim. It is an object of the present invention to provide a variable valve mechanism for an internal combustion engine that can suppress an inappropriate state.

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, an input arm which is pushed by a rotating cam and swings around an axis, and swings around the axis based on the swing of the input arm. An output arm that lifts the engine valve; and a slider that is connected to the input arm and the output arm via gears having different inclination directions of the tooth traces and that can reciprocate in the axial direction. In the variable valve mechanism of the internal combustion engine in which the arm is positioned in the axial direction according to the axial thickness of the shim provided between the standing wall portion supporting the shaft and between the arms, The gist is that the shim is made of ceramic.

  In the variable valve mechanism, the axial positions of the input arm and output arm greatly affect the maximum lift amount of the engine valve and the operating angle of the intake cam. For this reason, the above-mentioned maximum lift amount and action with respect to the axial displacement of the slider can be obtained by appropriately replacing the shims provided between the arms and the standing wall and between the arms with ones having different axial thicknesses. The axial position of each arm is adjusted to an appropriate position so that the angle change mode is in an appropriate state. As a result of such adjustment, the axial thickness of each shim is different. If each of the shims is formed of an iron-based material or the like, the thermal expansion in the axial direction of each shim during engine operation differs greatly for each shim. Then, due to the variation in the thermal expansion of each shim, the axial position of each arm and the relative position between the arms deviate from the proper positions, and the maximum lift amount and the operating angle change mode with respect to the axial displacement of the slider. Is in an incorrect state. However, according to the above-described configuration, since the shim is formed of a ceramic having almost no thermal expansion, the above-described variation in thermal expansion for each shim does not occur. Therefore, due to the variation in thermal expansion for each shim, the axial position of each arm and the relative position between the arms deviate from the proper positions, and the maximum lift and working angle change with respect to the axial displacement of the slider. It can suppress that a mode becomes an improper state.

Hereinafter, an embodiment in which the present invention is embodied in a variable valve mechanism of a multi-cylinder engine for an automobile will be described with reference to FIGS.
FIG. 1 is an enlarged sectional view showing a structure around a cylinder head 2 of a predetermined cylinder in 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 communicated and blocked by the opening / closing operation of the intake valve 9, and the exhaust passage 8 and the combustion chamber 6 are communicated and blocked by the opening / closing operation of the exhaust valve 10. Become. 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 are rotated 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 shaft 11 and the exhaust cam shaft 12 of the intake cam 11a and the exhaust cam 12a.

  Further, the engine 1 is provided with a variable valve mechanism that varies the valve characteristics of the engine valves such as the intake valve 9 and the exhaust valve 10. As one of such variable valve mechanisms, a lift amount variable mechanism 14 is provided between the intake cam 11a and the intake valve 9 to vary the maximum lift amount of the valve 9 and the operating angle of the intake cam 11a. . Through the driving of the variable lift amount mechanism 14, for example, the maximum lift amount and the operating angle are controlled to be larger 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 lift amount variable mechanism 14 will be described.
The variable lift amount mechanism 14 includes a rocker shaft 15 and a control shaft 16 that extend in parallel with the intake camshaft 11, an input arm 17 that is pushed by the rotating intake cam 11a and swings about the rocker shaft 15, and this input. An output arm 18 that swings about the rocker shaft 15 based on the swing of the arm 17 is provided. The input arm 17 is rotatably attached to a roller 19 and is biased toward the intake cam 11a by a 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 the output arm 18 swings, and the intake valve 9 is lifted through the rocker arm 21.

  One end of the rocker arm 21 is supported by the lash adjuster 22, and the other end 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 one end and the other end 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 lift amount mechanism 14, the maximum lift amount of the intake valve 9 and the action of the intake cam 11a on 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 corner 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.

  Here, a structure for changing the relative position in the swing direction of the input arm 17 and the output arm 18 in the lift amount varying mechanism 14 will be described in detail with reference to FIGS.

  FIG. 2 is a cutaway perspective view showing the internal structure of the variable lift amount mechanism 14, specifically the internal structure of the input arm 17 and the output arm 18 attached to the rocker shaft 15. As shown in the figure, the rocker shaft 15 passes through the input arm 17 and the output arm 18. Further, a cylindrical slider 26 is fitted into a portion corresponding to the input arm 17 and the output arm 18 on the outer peripheral surface of the rocker shaft 15. On the outer wall of the slider 26, an input gear 27a having a helical spline 27 is provided at the longitudinal center, and an output gear 29a having a helical spline 29 is provided at both longitudinal ends.

  On the other hand, as shown in FIG. 3, 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. 2) of the slider 26, and the internal gear 30a of the output arm 18 is meshed with the output gear 29a (FIG. 2) of the slider 26. 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.

  The rocker shaft 15 is formed in a cylindrical shape, and a control shaft 16 connected to the slider 26 by a pin is inserted inside the rocker shaft 15. When the control shaft 16 is moved in the axial direction together with the slider 26, the relative positions of the input arm 17 and the output arm 18 in the swinging direction are changed by the meshing of the helical splines 27, 29 and the helical splines 28, 30. The

  Specifically, as the control shaft 16 is displaced in the arrow L 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 control shaft 16 is displaced in the arrow H direction. The relative positions are changed so as to be separated from each other as the distance is increased. 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. The displacement in the axial direction of the control shaft 16 as described above is realized by, for example, drive control of an actuator using an electric motor.

  Next, a structure for mounting the input arm 17, the output arm 18, the slider 26, the rocker shaft 15, the control shaft 16 and the like in the lift amount variable mechanism 14 to the cylinder head 2, and a structure for connecting the slider 26 and the control shaft 16. Will be described with reference to FIG.

  As shown in the figure, the rocker shaft 15 and the control shaft 16 pass through the standing wall 45 of the cylinder head 2 and through the arms 17 and 18 sandwiched between the two standing walls 45. Yes. Of the arms 17 and 18, the input arm 17 is sandwiched between two output arms 18. The input arm 17 is positioned corresponding to the intake cam 11a (see FIG. 1), and the two output arms 18 are positioned corresponding to the two intake valves 9 (see FIG. 1). A slider 26 fitted to the rocker shaft 15 is positioned inside each arm 17, 18. An input gear 27 a and an output gear 29 a of the slider 26, and an internal gear 28 a and an output arm of the input arm 17. The 18 internal gears 30a mesh with each other.

  A pin 51 for connecting the shaft 16 and the slider 26 is inserted in the control shaft 16 in the radial direction. Further, at a position corresponding to the pin 51 on the rocker shaft 15, an elongated hole 33 extending in the axial direction and through which the pin 51 passes is formed. Further, a groove 34 is formed at a position corresponding to the pin 51 on the inner peripheral surface of the slider 26 so as to extend in the circumferential direction (a direction orthogonal to the paper surface in the drawing) and into which the tip of the pin 51 is inserted. A bush 35 is provided at the tip of the pin 51 located in the groove 34.

  The axial movement of the control shaft 16 is allowed through movement of the pin 51 along the elongated hole 33. When the pin 51 moves along the elongated hole 33 as the control shaft 16 moves in the axial direction, the bush 35 is pressed against the inner surface of the groove 34, and the slider 26 moves in the axial direction of the control shaft 16. Further, when the input arm 17 and the output arm 18 swing, the slider 26 is displaced (rotated) in the circumferential direction with respect to the outer peripheral surface of the rocker shaft 15. Allowed by grooves 34 that move relative to each other.

Next, a structure for adjusting the axial positions of the input arm 17 and the output arm 18 will be described.
The axial positions of the input arm 17 and the output arm 18 have a great influence on the change of the maximum lift amount and the operating angle with respect to the axial displacement of the slider 26. For this reason, a shim 46 is provided between the standing wall portion 45 and the output arm 18, and a shim 50 is provided between the arms 17, 18. The shims 46, 50 are appropriately changed to those having different axial thicknesses. By exchanging, the axial positions of the input arm 17 and the output arm 18 are adjusted to appropriate positions so that the above-described change modes of the maximum lift amount and the operating angle are appropriate. By performing such position adjustment, the axial thickness of each of the shims 46 and 50 is different for each shim.

  By the way, if an iron-based material is used as a material for forming the shims 46 and 50, the shim 46 during engine operation is used when the axial thickness of the shims 46 and 50 is different for each shim as described above. , 50 in the axial direction is greatly different for each shim. As described above, when the thermal expansion in the axial direction of each of the shims 46 and 50 varies, the deviation from the appropriate state of the axial positions of the arms 17 and 18 increases as the variation increases. Is as described in the column “Problems to be solved”. As a result, the change mode of the maximum lift amount of the intake valve 9 and the operating angle of the intake cam 11a with respect to the axial displacement of the slider 26 is in an inappropriate state.

  Therefore, in the present embodiment, the shims 46 and 50 are formed of ceramic that has almost no thermal expansion. As a result, the variation in thermal expansion of each of the shims 46 and 50 does not occur, and the axial positions of the arms 17 and 18 and the relative positions of the arms 17 and 18 are the proper positions due to the variations. Therefore, it is possible to suppress the change of the maximum lift amount and the operating angle from being in an inappropriate state.

According to the embodiment described in detail above, the following effects can be obtained.
(1) By forming the shims 46 and 50 of ceramic, thermal expansion in the axial direction of each of the shims 46 and 50 can be avoided. For this reason, it is possible to prevent the axial positions of the arms 17 and 18 from deviating from the proper positions due to the variation of the thermal expansion for each shim, and thus the maximum lift amount with respect to the axial displacement of the slider 26. In addition, it is possible to suppress the state of change of the working angle from being in an inappropriate state.

  (2) The lift amount variable mechanism 14 is provided for each cylinder of the engine 1, and the two output arms 18 are swung based on the swing of the one input arm 17, whereby the two intakes of each cylinder are swung. The valve 9 is configured to open and close. For this reason, when the variation of the thermal expansion in the axial direction of each of the shims 46 and 50 increases, the deviation of the relative positions of the arms 17 and 18 from the appropriate state also increases, and the two output arms 18 in the input arm 17 differ from each other. The distance between them will be different. As a result, the change in the maximum lift amount of the intake valve 9 and the operating angle of the intake cam 11a with respect to the axial displacement of the slider 26 differs between the two intake valves 9 in one cylinder, and combustion in the same cylinder The problem of affecting the state arises. However, by forming the shims 46 and 50 of ceramic, thermal expansion in the axial direction of each of the shims 46 and 50 can be avoided, and the above-described problem can be suppressed.

  (3) In the multi-cylinder engine 1, the lift amount variable mechanism 14 is provided for each cylinder, and the axial positions of the arms 17 and 18 are adjusted by the shims 46 and 50 for each cylinder. For this reason, if the shims 46 and 50 are formed using an iron-based material or the like, the variation mode of the maximum lift amount and the working angle is inappropriate due to variations in thermal expansion of the shims 46 and 50. When the engine is in a different state, the deviation of the change mode from the appropriate state is different for each cylinder. As a result, there is a possibility that the combustion state between the cylinders varies. However, such problems can be suppressed by forming the shims 46 and 50 from ceramic.

  (4) Since the input arm 17 and the output arm 18 are usually formed using a ferrous material in terms of ease of processing and strength, if the shims 46 and 50 are formed of a ferrous material, the arm 17 and 18 and shims 46 and 50 are made of the same material. In such a case, when the arms 17 and 18 and the shims 46 and 50 slide in the circumferential direction in a thermally expanded state, the friction tends to increase at their contact surfaces and wear tends to proceed. However, when the shims 46 and 50 are formed of ceramic, the arms 17 and 18 and the shims 46 and 50 are formed of different materials, and the above-described problems can be suppressed.

In addition, the said embodiment can also be changed as follows, for example.
The present invention may be applied to an engine provided with only one intake valve 9 for each cylinder or an engine provided with three intake valves.

  The present invention may be applied to a single cylinder engine. Even in this case, the same effects as in the above (1) and (3) can be obtained.

The expanded sectional view which shows the structure around the cylinder head of the engine to which the variable valve mechanism of this embodiment was applied. The fracture | rupture perspective view which shows the internal structure of a lift amount variable mechanism. The broken perspective view which shows the internal structure of an input arm and an output arm. Sectional drawing which shows the attachment structure to the cylinder head of a slider, an input arm, and an output arm.

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 ... Lift amount variable mechanism, 15 ... Rocker shaft, 16 ... Control shaft, 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 ... internal gear, 33 ... long hole, 3 ... groove, 35 ... bush, 45 ... vertical wall portion, 46 ... Sim, 50 ... Sim, 51 ... pin.

Claims (1)

An input arm that is pushed by a rotating cam and swings about an axis, an output arm that swings about the axis based on the swing of the input arm and lifts the engine valve, the input arm, and the output The sliders are connected to the arms via gears having different inclination directions of the tooth traces and are reciprocally movable in the axial direction, and between the arms and the standing wall portion supporting the shaft, and between the arms. In the variable valve mechanism of the internal combustion engine in which the arm is positioned in the axial direction according to the axial thickness of the shim provided between
The variable valve mechanism for an internal combustion engine, wherein the shim is made of ceramic.

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