JP2006029262A - Internal combustion engine provided with variable valve-characteristic mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To circumvent the need to drive a variable valve-characteristic mechanism by a larger force than it needs to be. <P>SOLUTION: An engine 11 comprises a variable valve-characteristic mechanism and a spring load-changing device 70. The variable valve-characteristic mechanism has as a valve characteristic, at least either one of a maximum lift and an angle of action of an intake valve 21 which is opened by an intake cam 26 against a valve spring 25. The valve characteristic is changed in accordance with operation conditions of the engine 11. The spring load-changing device 70 changes the largest spring-load of the valve spring 25 at the time when the intake valve 21 has the maximum lift in accordance with the valve characteristic of the variable valve-characteristic device. More specifically, if the maximum lift by the variable valve characteristic device is not highest, the spring load-changing device 70 reduces the maximum spring-load less than that at the highest time. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an internal combustion engine including a valve characteristic variable device that changes a valve characteristic of an engine valve in accordance with an engine operating state.

  A general valve operating apparatus for an internal combustion engine is configured such that an intake / exhaust valve (hereinafter referred to as an engine valve) urged in a valve closing direction by a valve spring directly by a cam of a camshaft that is driven to rotate by the internal combustion engine, or A configuration is adopted in which the valve is pushed down (lifted) through a rocker arm or the like to open the valve. The main function of the valve spring is to overcome the inertia force of the engine valve and to open and close the engine valve by faithfully following the profile of the cam. This function is exhibited on condition that the maximum spring load is larger than a value required for ensuring the followability of the engine valve. The maximum spring load is the spring load when the engine valve is lifted by the maximum amount. However, if the maximum spring load is excessively larger than the required value, a large force is required to rotate the camshaft, which causes a reduction in fuel consumption. Setting the maximum spring load of the valve spring is important from the viewpoint of suppressing fuel consumption reduction while ensuring the followability of the engine valve. Therefore, a value slightly larger than the required value is set as the maximum spring load of the valve spring.

  On the other hand, for example, an internal combustion engine mounted on a vehicle is equipped with a variable valve characteristic device that varies at least one of the maximum lift amount and working angle of the engine valve (hereinafter referred to as a valve characteristic) according to the engine operating state. It has been proposed to do. In such an internal combustion engine, as the valve characteristic of the engine valve changed by the valve characteristic variable device increases, the maximum spring load required for the above-described valve spring increases. Therefore, in an internal combustion engine equipped with a variable valve characteristic device, the maximum spring load is set on the basis of the maximum range of valve characteristics.

In addition, as a prior art document concerning this invention, the following patent documents 1 are mentioned, for example. This is because the spring constant of the valve spring is adjusted step by step with the displacement by appropriately adjusting the line pitch of the valve spring so that an optimal spring load is obtained for the lift amount of the engine valve. It is intended to change. For example, the spring constant is increased in a region where the lift amount is small, the spring constant is decreased in a region where the lift amount is large, or conversely, the spring constant is decreased in a region where the lift amount is small, and the spring constant is large in a region where the lift amount is large. The constant is increased.
Japanese Patent Laid-Open No. 10-141027 (FIGS. 1 and 2)

  However, when the maximum spring load is set based on the maximum value of the valve characteristics as described above, the maximum spring load is appropriate at the maximum, but the valve characteristics changed by the valve characteristics variable device are small, medium, etc. If not, the maximum spring load will be greater than the maximum spring load required for the valve spring in its valve characteristics. As a result, the valve characteristic variable device must be driven with an unnecessarily large force to lift the engine valve, resulting in deterioration of fuel consumption.

  In Patent Document 1 described above, the spring constant of the valve spring is merely changed according to the lift amount of the engine valve, and the maximum spring load is still larger than the required value when the valve characteristic is other than the maximum. The same problem as above can occur.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an internal combustion engine including a valve characteristic varying device that does not require driving the valve characteristic varying device with a force greater than necessary. There is.

In the following, means for achieving the above object and its effects are described.
According to the first aspect of the present invention, at least one of the maximum lift amount and the operating angle of the engine valve that is opened by the cam against the valve spring is set as a valve characteristic, and the valve characteristic is changed according to the engine operating state. In an internal combustion engine equipped with a variable valve characteristic device, there is provided spring load changing means for changing a maximum spring load of the valve spring when the engine valve is lifted by a maximum amount according to the valve characteristic by the variable valve characteristic device. Yes.

  According to the above configuration, in the internal combustion engine, when the cam rotates, the engine valve is pushed down against the valve spring and opened. The function of the valve spring may cause the engine valve to follow the cam. This function is exhibited on the condition that the maximum spring load of the valve spring is larger than the value required to make the engine valve follow the cam. On the other hand, if the maximum spring load is excessively larger than this required value, a large force is required to rotate the cam. Therefore, it is desirable that the maximum spring load is set to a value slightly larger than the required value.

  Incidentally, the valve characteristic (at least one of the maximum lift amount and the working angle) of the engine valve is changed by the valve characteristic variable device. The required maximum spring load increases as the valve characteristics increase. Therefore, if the maximum spring load is constant regardless of the valve characteristics and the maximum spring load is set on the basis of the maximum valve characteristics, the value required when the valve characteristics are other than the maximum. Becomes oversized.

  In this regard, in the first aspect of the invention, the maximum spring load is changed according to the valve characteristic at that time by the variable valve characteristic device. This change makes it possible to bring the maximum spring load close to the required value corresponding to the valve characteristic at that time even when the valve characteristic is other than the maximum. As a result, it is not necessary to drive the variable valve characteristic device with a larger force than necessary, and various problems associated with driving the variable valve characteristic device with an excessive driving force, such as a reduction in fuel consumption, can be suppressed. It becomes.

  According to a second aspect of the present invention, in the first aspect of the invention, the spring load changing means may be configured such that when the valve characteristic is changed to a non-maximum time or a non-maximum value by the valve characteristic variable device, It is assumed that the maximum spring load is reduced.

  Here, the maximum spring load required for the valve spring becomes smaller as the valve characteristic of the variable valve characteristic device becomes smaller. Therefore, according to the invention described in claim 2, when the valve characteristic is changed to non-maximum or non-maximum, the maximum spring load is made smaller than the maximum value, whereby the maximum spring load is brought close to the required value. The effect of the invention according to the first aspect can be reliably obtained.

  According to a third aspect of the present invention, in the second aspect of the present invention, the spring load changing means is a non-maximum time of the valve characteristic by the valve characteristic variable device and the rotational speed of the cam is high. It is assumed that the degree of reducing the maximum spring load is smaller than when it is low.

  Here, in order to ensure the followability of the engine valve with respect to the cam, factors affecting the maximum spring load required for the valve spring include the rotational speed of the cam in addition to the lift amount of the engine valve. Generally, this maximum spring load is greater when the cam rotational speed is high than when it is low.

  In this regard, according to the third aspect of the present invention, the valve characteristic by the valve characteristic variable device is non-maximum, and the degree of reducing the maximum spring load is smaller when the rotational speed of the cam is high than when it is low. When the degree of reducing the maximum spring load is reduced in this way, the maximum spring load is increased when the rotational speed is high than when it is low, provided that the value required when the valve characteristic is maximum is not exceeded. It becomes a value suitable for the valve characteristics and the rotational speed of the cam at that time.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the spring load changing means reduces the degree of decreasing the maximum spring load as the rotational speed of the cam increases. .

  In general, the maximum spring load required for the valve spring to cause the engine valve to follow the cam increases as the cam rotational speed increases. In this regard, in the invention according to the fourth aspect, the valve characteristic by the variable valve characteristic device is non-maximum, and the higher the cam rotation speed, the smaller the degree of decreasing the maximum spring load. Due to this change in valve characteristics, the maximum spring load is increased as the cam rotation speed increases, provided that the maximum required value of the valve characteristics is not exceeded, and is more suitable for the valve characteristics and cam rotation speed at that time. Value.

  According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the valve characteristic varying device includes a control shaft that is moved in an axial direction by an actuator, and a control shaft on the control shaft. An input arm and an output arm provided so as to be able to swing, a control shaft, and a slider provided between the input arm and the output arm, wherein the slider causes the swing of the input arm by the cam. The engine valve is driven by transmitting to the output arm via the actuator, and the relative phase difference between the input arm and the output arm is changed by the displacement of the slider accompanying the axial movement of the control shaft by the actuator. The valve characteristic is changed.

  According to the above configuration, in the variable valve characteristic device, the input arm swings with the control shaft as a fulcrum as the cam rotates. This swing is transmitted to the output arm via the slider, and the output arm swings. With this swinging output arm, the corresponding engine valve is pushed down against the valve spring to open. Further, when the control shaft is driven by the actuator and moved in the axial direction, the slider is displaced along with the movement, and the relative phase difference between the input arm and the output arm is changed according to the displacement, and the valve characteristic of the engine valve is changed. Be changed. Then, as described above, the maximum spring load is changed by the spring load changing means according to the valve characteristic of the valve characteristic variable device. With this change, even when the valve characteristics are other than the maximum, the maximum spring load is brought close to the required value corresponding to the valve characteristics at that time, and the actuator of the variable valve characteristics device is driven with a force greater than necessary. You don't have to.

  According to a sixth aspect of the present invention, in the fifth aspect of the invention, the slider of the valve characteristic variable device has a direction in which the valve characteristic is reduced in the axial direction of the control shaft by at least the valve spring. When the force is applied and the spring load changing means is changed in the direction in which the valve characteristic is reduced by the valve characteristic changing device, the maximum spring load at the maximum time of the valve characteristic is not exceeded. The maximum spring load is assumed to be larger than before the change.

  According to the above configuration, in the variable valve characteristic device, a force is applied to the slider in the direction of reducing the valve characteristic in the axial direction of the control shaft by at least the valve spring. This force causes the slider to move in a direction that reduces the valve characteristics. On the other hand, when the valve characteristic is changed by the variable valve characteristic device, the maximum spring load is changed by the spring load changing means from that before the change on condition that the maximum spring load at the maximum of the valve characteristic is not exceeded. Increased. By increasing the maximum spring load in this way, the force in the above direction acting on the slider is strengthened. As a result, the moving speed of the slider is increased, and the relative phase difference between the input arm and the output arm is changed quickly. As a result, it is possible to improve the change responsiveness by increasing the change speed of the valve characteristic by the variable valve characteristic device while reducing the required driving force of the variable valve characteristic device.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
As shown in FIGS. 1 and 2, a vehicle is equipped with a vehicular multi-cylinder gasoline engine (hereinafter simply referred to as an engine) 11 as an internal combustion engine. The engine 11 includes a cylinder block 13 having a plurality of cylinders 12 and a cylinder head 14 mounted thereon. A piston 15 is accommodated in the cylinder bore 12A for each cylinder 12 so as to be able to reciprocate. Each piston 15 is connected to a crankshaft 16 (see FIG. 2) that is an output shaft via a connecting rod (not shown). The reciprocating motion of each piston 15 is converted into rotational motion by the connecting rod and then transmitted to the crankshaft 16.

  A space surrounded by the piston 15, the cylinder bore 12 </ b> A, and the cylinder head 14 is a combustion chamber 17. The cylinder head 14 is provided with an intake port 18 that forms part of the intake passage and an exhaust port 19 that forms part of the exhaust passage for each cylinder 12. The downstream end of the intake port 18 and the upstream end of the exhaust port 19 are opened at locations corresponding to the combustion chamber 17 on the lower surface of the cylinder head 14.

  The cylinder head 14 is provided with an intake valve 21 that opens and closes between the intake port 18 and the combustion chamber 17 and an exhaust valve 22 that opens and closes between the exhaust port 19 and the combustion chamber 17 as engine valves. The intake valve 21 and the exhaust valve 22 are supported by a valve guide 23 so as to be capable of reciprocating in the axial direction (substantially up and down in FIG. 1).

  Retainers 24 are attached to the upper portions of the intake and exhaust valves 21 and 22, respectively. A spring seat 20 is provided at a location corresponding to the upper portion of the valve guide 23 in the cylinder head 14. A valve spring 25 is disposed around the intake / exhaust valves 21 and 22 and between the retainer 24 and the spring seat 20. By these valve springs 25, the intake / exhaust valves 21, 22 are always urged in the valve closing direction (substantially upward in FIG. 1).

  An intake cam shaft 27 having an intake cam 26 is rotatably supported by a support wall 28 substantially above the intake valve 21 in the cylinder head 14 (see FIG. 2). Similarly, an exhaust cam shaft 31 having an exhaust cam 29 is rotatably supported substantially above the exhaust valve 22 in the cylinder head 14. The intake / exhaust camshafts 27 and 31 are drivingly connected to the crankshaft 16 by a timing chain 32, a sprocket (not shown), and the like. The rotation of the crankshaft 16 is transmitted to the intake / exhaust camshafts 27 and 31 via the timing chain 32 and the like. As the camshafts 27 and 31 rotate, the intake / exhaust valves 21 and 22 are pushed down (lifted) against the valve spring 25 to open the intake / exhaust ports 18 and 19.

  At this time, the valve spring 25 is required to overcome the inertial force of the intake / exhaust valves 21 and 22 and cause the intake / exhaust valves 21 and 22 to faithfully follow the profiles of the intake / exhaust cams 26 and 29. Is done. In order to satisfy this requirement, it is necessary that the maximum spring load is larger than a value required for ensuring the followability of the intake / exhaust valves 21 and 22. The maximum spring load is a spring load when the intake / exhaust valves 21 and 22 are lifted by the maximum amount and expanded and contracted by the maximum amount. However, if the maximum spring load is excessively larger than the required value, an unnecessarily large force is required to rotate the intake / exhaust camshafts 27 and 31, which causes a reduction in fuel consumption. From the viewpoint of suppressing the necessary driving force of the intake / exhaust cam shafts 27, 31 while ensuring the followability of the intake / exhaust valves 21, 22, setting of the maximum spring load of the valve spring 25 is important. Therefore, a value slightly larger than the required value is set as the maximum spring load of the valve spring 25.

  Here, generally, the required value of the maximum spring load increases as the lift amount of the intake / exhaust valves 21 and 22 increases and the rotational speed of the intake / exhaust cams 26 and 29 increases. Further, since the intake / exhaust camshafts 27, 31 are drivingly connected to the crankshaft 16, the rotational speed of the intake / exhaust cams 26, 29 and the rotational speed of the crankshaft 16 (engine rotational speed) correspond to each other. Yes. Therefore, for the exhaust valve 22 in which the valve characteristics such as the maximum lift amount and the working angle are constant regardless of the operating state of the engine 11, the valve spring 25 is based on the required value when the engine rotation speed becomes the maximum value that can be taken. The maximum spring load is set. Further, as will be described later, for the intake valve 21 in which the maximum lift amount and the operating angle are changed according to the engine operating state, the maximum value that the maximum lift amount and the operating angle can be taken and the maximum engine rotational speed can be taken. The maximum spring load of the valve spring 25 is set based on the required value when the value is reached.

  A fuel injection valve (not shown) that injects fuel downstream of the intake port 18 is attached to the intake passage corresponding to each cylinder 12. The injected fuel is mixed with the intake air introduced into the combustion chamber 17 through the intake passage and becomes an air-fuel mixture. Note that the fuel may be directly injected into the combustion chamber 17 from the fuel injection valve.

  A spark plug 33 is attached to the cylinder head 14 corresponding to each cylinder 12. The air-fuel mixture is ignited by electric sparks of the spark plug 33, and explodes and burns. The piston 15 is reciprocated by the high-temperature and high-pressure combustion gas generated at this time, the crankshaft 16 is rotated, and the driving force (output torque) of the engine 11 is obtained. The combustion gas is discharged to the exhaust passage through the exhaust port 19.

  As shown in FIG. 2, at the end of the engine 11 on the timing chain 32 side (the left end of FIG. 2), the relative rotation phase of the intake camshaft 27 with respect to the crankshaft 16 is adjusted, and the valve timing of the intake valve 21 is adjusted. A variable valve timing mechanism 34 for advancing or retarding (opening / closing period) is provided. Further, the engine 11 is provided with a maximum lift amount variable mechanism 35 that continuously changes the maximum lift amount and the operating angle of each intake valve 21 as a valve characteristic variable device. Here, as shown in FIG. 8, the operating angle of the intake valve 21 is an angular range for the rotation of the crankshaft 16 from the start of the intake valve 21 to the closing of the valve. The maximum lift amount of the intake valve 21 is a displacement amount when the intake valve 21 is displaced (lifted) to the lowest position. In the present embodiment, when the maximum lift amount is changed by the maximum lift amount varying mechanism 35, the operating angle is also changed accordingly. Thus, the maximum lift amount and the working angle correspond one-on-one. Therefore, when the maximum lift amount and the operating angle are changed by the maximum lift amount variable mechanism 35, it is simply expressed as “change the maximum lift amount”. The exhaust valve 22 is not provided with such a variable valve timing mechanism 34 or a maximum lift amount variable mechanism 35.

  As shown in FIG. 2, the maximum lift variable mechanism 35 includes an intermediate drive mechanism 36 for each cylinder 12, one support pipe 37 common to all the intermediate drive mechanisms 36, one control shaft 38, and One actuator 39 is provided.

  The support pipe 37 is disposed so as to extend in the arrangement direction of the cylinders 12 (the left-right direction in FIG. 2), and is fixed to the support wall portion 28 through. Note that this direction is referred to as an “axial direction” when it is not necessary to distinguish, and when it is necessary to distinguish, it is referred to as an arrow A direction or an arrow B direction. An arrow A direction is a direction approaching the timing chain 32 described above, and is a direction in which the maximum lift amount of the intake valve 21 is reduced. An arrow B direction is a direction away from the timing chain 32, and is a direction in which the maximum lift amount is increased. Due to the through-fixation, the support pipe 37 cannot move in the axial direction and cannot rotate. The control shaft 38 is inserted into the support pipe 37 and is driven to reciprocate in the axial direction by an actuator 39 made of an electric motor or the like.

  Each intermediate drive mechanism 36 is provided between the intake camshaft 27 and the intake valve 21 (see FIG. 1). As shown in FIGS. 2 and 3, each mediation drive mechanism 36 includes an input arm 41 and a pair of output arms 42 and 43 arranged on both sides in the axial direction. The input arm 41 and the output arms 42 and 43 are connected to each other at their opposite ends by fitting. The input arm 41 and the output arms 42 and 43 for each intermediate drive mechanism 36 are disposed between the support wall portions 28 and 28, and displacement in the axial direction is restricted by the support wall portions 28 and 28 (see FIG. 5).

  As shown in FIGS. 3 to 6, the input arm 41 includes a pair of support pieces 44 and 44, and a roller 45 is pivotally supported between the support pieces 44 and 44. Each of the output arms 42 and 43 includes a base circular portion 46 and a nose 47 having a cam surface 47A that curves in a concave shape.

  A power transmission slider 48 is disposed between the support pipe 37 and the input arm 41 and the output arms 42 and 43. The slider 48 is supported on the support pipe 37 so as to be rotatable and movable in the axial direction. In order to connect the slider 48 to the control shaft 38 so that power can be transmitted, a groove 49 extending in the circumferential direction is formed on the inner peripheral surface of the slider 48. The groove portion 49 communicates with the outside of the slider 48 through a through hole 51 provided in the slider 48 (see FIG. 6). In the support pipe 37, elongated holes 52 extending in the axial direction are formed at locations corresponding to the respective mediation drive mechanisms 36. The groove 49 and the long hole 52 are provided with a locking pin 53 inserted through the through-hole 51 described above, and one end thereof (the lower end in FIGS. 5 and 6) is press-fitted and fixed to the control shaft 38. Yes. A bushing 54 is fixed to the other end portion (the upper end portion in FIGS. 5 and 6) of the locking pin 53 located in the groove portion 49.

  Therefore, as described above, the support pipe 37 is fixed to the cylinder head 14 (support wall portion 28). However, as the control shaft 38 moves in the axial direction, the locking pin 53 is inserted into the long hole 52 of the support pipe 37. By moving inward, the slider 48 can be moved in the axial direction via the bush 54. Furthermore, since the slider 48 itself is locked to the locking pin 53 and the bush 54 by the groove portion 49 extending in the circumferential direction, the axial position is determined by the locking pin 53 and the bush 54. It can be rotated about the axis.

  In order to transmit power between the input arm 41 and the slider 48, a helical spline 41A is formed on the inner peripheral surface of the input arm 41. The helical spline 41A is twisted clockwise toward the output arm 42 side. Correspondingly, as shown in FIG. 4, a helical spline 48 </ b> A twisted in the same direction is formed in an intermediate portion in the axial direction of the outer peripheral surface of the slider 48, and this meshes with the helical spline 41 </ b> A of the input arm 41 described above. Are combined.

  Further, in order to transmit power between the output arms 42 and 43 and the slider 48, the inner peripheral surfaces of the output arms 42 and 43 are opposite to the helical spline 41A of the input arm 41, that is, the input arm 41. Helical splines 42B and 43C that are twisted in the counterclockwise direction as they move away from the output arm 42 are formed. Correspondingly, helical splines 48B and 48C twisted in the same direction are formed at both ends of the outer peripheral surface of the slider 48 in the axial direction, and these are meshed with the helical splines 42B and 43C of the output arms 42 and 43, respectively. ing. Thus, the helical splines 41A and 48A and the helical splines 42B, 43C, 48B and 48C are twisted in the opposite directions. For this reason, the slider 48 rotates while being displaced in the same direction in conjunction with the axial movement of the control shaft 38, thereby applying torsional forces in opposite directions to the input arm 41 and the output arms 42 and 43. The relative phase difference between the input arm 41 and the output arms 42 and 43 changes. Further, by setting the helical direction of the helical splines 41A, 42B, 43C, 48A, 48B, 48C, the relative phase difference between the input / output arms 41 to 43 is such that the slider 48 is in the direction of arrow A (the direction in which the maximum lift amount is reduced). It becomes smaller as it is displaced to.

  As shown in FIG. 1, the roller 45 of each intermediary drive mechanism 36 is in contact with the intake cam 26 of the intake camshaft 27, and a substantially downward force by the intake cam 26 is generated by the rotation of the intake camshaft 27. 45. A spring 55 is disposed between the support piece 44 and the cylinder head 14 in a compressed state, and the roller 45 is always pressed against the intake cam 26 by the spring 55. The input arm 41 swings up and down with the control shaft 38 as a fulcrum so that a substantially downward force that changes according to the cam profile of the intake cam 26 and an upward force by the spring 55 are balanced.

  On the other hand, a rocker arm 56 is disposed between the intake valve 21 and the output arms 42 and 43, and the swing of the output arms 42 and 43 is transmitted to the intake valve 21 via the rocker arm 56. That is, each rocker arm 56 is supported by an adjuster 57 at a base end portion (left end portion in FIG. 1) 56A so as to be swingable, and in contact with the intake valve 21 at a distal end portion (right end portion in FIG. 1) 56B. Yes. Then, the urging force of the valve spring 25 is applied to the distal end portion 56B of the rocker arm 56 through the intake valve 21, and the roller 58 of the rocker arm 56 is in contact with the base circular portion 46 or the nose 47 of both the output arms 42 and 43. .

  Therefore, when the intake camshaft 27 rotates, in the mediation drive mechanism 36, the input cam 41 swings up and down around the control shaft 38 by the intake cam 26. This swing is transmitted to the output arms 42 and 43 via the slider 48, and the output arms 42 and 43 swing up and down. By these swinging output arms 42 and 43, the corresponding intake valves 21 are driven and opened. As the valve is opened, air is sucked from the intake port 18 into the combustion chamber 17.

  Further, when the control shaft 38 is moved in the axial direction by the actuator 39, the relative phase difference between the input arm 41 and each of the output arms 42 and 43 is changed with respect to the swinging direction of the input / output arms 41 to 43. . With this change, the maximum lift amount of each intake valve 21 changes continuously. When the slider 48 is displaced by the maximum amount in the direction of arrow A and the relative phase difference is small, the maximum lift amount is small and the intake air amount per cylinder 12 is small. When the relative phase difference increases with the movement of the slider 48 in the arrow B direction, the maximum lift amount increases and the intake air amount increases.

  As shown in FIGS. 1 and 4, in the intermediate drive mechanism 36, a substantially downward force is applied to the roller 45 of the input arm 41 by the intake cam 26. This force is transmitted to the slider 48 through the helical splines 41A and 48A. As described above, the helical splines 41A and 48A are twisted in the clockwise direction toward the output arm 42 side. A load in the direction of arrow A acts on the slider 48 as a thrust direction force determined by the twist direction and the force from the intake cam 26.

  On the other hand, a substantially upward force is applied to the output arms 42 and 43 by the valve spring 25 via the intake valve 21, the rocker arm 56, and the like. This force is transmitted to the slider 48 through the helical splines 42B, 43C and 48B, 48C. As described above, these helical splines 42B, 43C and 48B, 48C are twisted in the opposite direction to the helical splines 41A, 48A. A load in the direction of arrow A acts on the slider 48 as a force in the thrust direction determined by these twist directions and a force (valve reaction force) from the valve spring 25.

Thus, the slider 48 tends to move in the direction of arrow A due to the load acting through the input arm 41 and the load acting through both the output arms 42 and 43.
7A and 7B show the state of the mediation drive mechanism 36 when the control shaft 38 is moved by the actuator 39 in the direction of arrow B in FIG. The slider 48 is located at the end in the arrow B direction in the movable range. At this time, the relative phase difference between the input arm 41 and the output arms 42 and 43 is maximized.

  In particular, FIG. 7A shows a state where the intake cam 26 is in contact with the roller 45 of the mediation drive mechanism 36 at the base circle portion 26A. In this state, a portion close to the nose 47 in the base circular portion 46 of both the output arms 42 and 43 is in contact with the roller 58 of the rocker arm 56. For this reason, the intake valve 21 is closed (the lift amount is “0”).

  When the intake camshaft 27 rotates, the roller 45 is pushed down by the nose 26B of the intake cam 26, and the input arm 41 swings downward. This swing is transmitted to the output arms 42 and 43 via the slider 48, and the output arms 42 and 43 swing downward. Due to these swings, the cam surface 47A of the nose 47 immediately contacts the roller 58 of the rocker arm 56, and the roller 58 is pushed using substantially the entire range of the cam surface 47A as shown in FIG. Lower. By this depression, the rocker arm 56 swings downward with the base end portion 56A as a fulcrum, the distal end portion 56B of the rocker arm 56 largely pushes down the intake valve 21, and the intake port 18 is greatly opened (opened). The maximum lift amount is maximized, and the amount of air flowing from the intake port 18 into the combustion chamber 17 is maximized.

  When the control shaft 38 is moved in the direction of arrow A in FIG. 2 by the actuator 39 from the above state, the slider 48 is displaced in the same direction while rotating in conjunction with it. The rotation of the slider 48 applies torsional forces in opposite directions to the input arm 41 and the output arms 42 and 43, and the relative phase difference between the input arm 41 and the output arms 42 and 43 changes. This relative phase difference decreases as the displacement amount of the slider 48 increases.

  When the base circle portion 26 </ b> A of the intake cam 26 contacts the roller 45 of the mediation drive mechanism 36, the contact position of the base circle portion 46 of the output arms 42 and 43 with the roller 58 of the rocker arm 56 moves away from the nose 47. For this reason, even if the output arms 42 and 43 swing, the roller 58 of the rocker arm 56 continues to contact the base circle 46 without contacting the cam surface 47A of the nose 47 for a while.

  Thereafter, the cam surface 47A pushes down the roller 58, and the rocker arm 56 is swung downward with the base end portion 56A as a fulcrum. The use range of the cam surface 47A is as much as the roller 58 is initially separated from the nose 47. Less. As a result, the rocking angle of the rocker arm 56 is reduced and the maximum lift amount is reduced. Thus, the intake valve 21 opens the intake port 18 with a maximum lift amount smaller than that at the maximum. As the intake valve 21 opens, the amount of air flowing from each intake port 18 into the combustion chamber 17 decreases according to the amount of displacement of the slider 48 in the arrow A direction.

  Thus, by adjusting the position of the slider 48 through the control shaft 38 by the actuator 39, the maximum lift amount of the intake valve 21 driven by the output arms 42 and 43 is continuously set between the lift amount patterns shown in FIG. It is possible to make adjustments.

  By the way, as described above, with respect to the valve spring 25 that urges the intake valve 21, the maximum spring load is set based on the required value when the maximum lift amount becomes maximum. However, if such a setting is made, assuming that the maximum spring load is always constant regardless of the maximum lift amount, the maximum spring load is appropriate at the maximum, but the maximum lift amount is not maximum, such as small or medium. In this case, the actual maximum spring load is larger than the value required for the valve spring 25 described above.

  Therefore, in the present embodiment, the maximum spring load of the valve spring 25 when the intake valve 21 lifts the maximum amount is changed according to the maximum lift amount by the maximum lift amount variable mechanism 35. This change is realized by the spring load changing device 70 (spring load changing means). Next, the spring load changing device 70 will be described.

  As shown in FIGS. 10 and 11, the spring seat 20 corresponding to the intake valve 21 has a circular cross section and is formed of a concave portion in a state where its own center line is aligned with the axis of the intake valve 21. A seat case 61 is incorporated in the spring seat 20. The seat case 61 includes an inner cylinder part 62 and an outer cylinder part 63 that are arranged coaxially with the intake valve 21, and a bottom part 64 that connects the lower ends of the inner cylinder part 62 and the outer cylinder part 63. ing. The inner cylinder part 62 is fitted on the valve guide 23. Stoppers 65 that protrude outward are provided at a plurality of locations at the upper end of the inner cylindrical portion 62. The outer cylinder part 63 and the bottom part 64 are fitted into the spring seat 20. A number of oil holes 66 are formed in the bottom portion 64.

  In the cylinder head 14, an oil passage 67 extending in the cylinder arrangement direction (a direction orthogonal to the paper surface in FIG. 10) is provided below the spring seat 20. The cylinder head 14 is provided with an oil hole 68 that allows the oil passage 67 and the spring seat 20 to communicate with each other.

  In each seat case 61, an upper sheet 71 and a lower sheet 72 each having an annular shape have their respective inner peripheral surfaces in contact with the inner cylindrical portion 62 and each outer peripheral surface in contact with the outer cylindrical portion 63. Contained.

  As shown in FIGS. 9 to 11, most of the upper surface of the upper seat 71 is orthogonal to the axis of the intake valve 21. On this upper surface, an annular recess 73 is provided around the intake valve 21 to receive the lower end of the valve spring 25. The lower surface of the upper sheet 71 includes a plurality of inclined surfaces 74 inclined in the circumferential direction at a predetermined angle with respect to the upper surface, and a plurality of pressure receiving surfaces 75 provided between adjacent inclined surfaces 74 and 74.

  Most of the lower surface of the lower seat 72 is orthogonal to the axis of the intake valve 21. On this lower surface, an annular groove 76 is provided at a location corresponding to the oil hole 66 of the seat case 61. The upper surface of the lower sheet 72 includes a plurality of inclined surfaces 77 inclined in the circumferential direction at a predetermined angle with respect to the lower surface, and a plurality of pressure receiving surfaces 78 provided between adjacent inclined surfaces 77, 77. Further, the lower sheet 72 is provided with an oil hole 79 penetrating from each pressure receiving surface 78 to the annular groove 76.

  In FIGS. 9A and 9B, three inclined surfaces 74 and 77 and pressure receiving surfaces 75 and 78 of the upper sheet 71 and the lower sheet 72 are illustrated, but the number is not limited to this. . However, from the viewpoint of reducing the heights of the upper sheet 71 and the lower sheet 72 to make the structure compact, the number of the inclined surfaces 74 and 77 and the pressure receiving surfaces 75 and 78 should be about “3” and “4”. desirable.

  The angle formed by the inclined surface 74 with respect to the upper surface of the upper sheet 71 and the angle formed by the inclined surface 77 with respect to the lower surface of the lower sheet 72 are 10 to 20 degrees depending on the spring load, the shape of the upper sheet 71 and the lower sheet 72, and the like. It is desirable to set within the range.

  Further, the angle formed by the inclined surface 74 with respect to the pressure receiving surface 75 in the upper sheet 71 and the angle formed by the inclined surface 77 with respect to the pressure receiving surface 78 in the lower sheet 72 are points of view to suppress stress concentration due to contact between the upper sheet 71 and the lower sheet 72. Therefore, it is desirable that both be set to an obtuse angle.

  When the upper sheet 71 and the lower sheet 72 are housed in the seat case 61, the upper sheet 71 and the lower sheet 72 can be relatively rotated with the inclined surfaces 74 and 77 in close contact with each other. As shown in FIG. 10, in a state where the pressure receiving surface 75 is in contact with the pressure receiving surface 78, the upper sheet 71 and the lower sheet 72 cannot rotate relative to the side closer to the pressure receiving surfaces 75 and 78. In this state, the upper sheet 71 is located at the lower limit position of the movable range. From this state, when the upper sheet 71 and the lower sheet 72 are rotated relative to each other while the inclined surfaces 74 and 77 are in sliding contact with each other, the upper sheet 71 rises in the seat case 61.

  At this time, a plurality (3) defined by the inner cylindrical portion 62 and the outer cylindrical portion 63 of the seat case 61, the inclined surface 74 and the pressure receiving surface 75 of the upper sheet 71, and the inclined surface 77 and the pressure receiving surface 78 of the lower seat 72 are defined. Each space functions as a hydraulic chamber 81 of the hydraulic actuator (see FIG. 11).

  When the upper sheet 71 hits the stopper 65 at the upper end of the sheet case 61, the further upward movement of the upper sheet 71 is stopped, and the relative rotation between the lower sheet 72 and the upper sheet 71 is stopped. In this state, the two inclined surfaces 74 and 77 are in contact with each other at a part of them, and do not separate completely. That is, there is a permissible limit in the relative rotation of the upper sheet 71 and the lower sheet 72, and the inclined surface 74 of the upper sheet 71 and the inclined surface 77 of the lower sheet 72 are always in contact with each other and the pressure receiving surfaces 78, 75 on the other side. Never get over.

  The oil passage 67 branches off from the main oil passage 82. In the main oil passage 82, an oil pump 83, an oil switching valve (hereinafter abbreviated as OSV) 84, and a check valve 85 are arranged. The oil pump 83 sucks the oil 80 in the oil pan 86 and discharges it to the main oil passage 82. The check valve 85 allows the oil 80 to flow from the oil pump 83 to the oil passage 67 through the main oil passage 82, and prevents the oil 80 from flowing backward in the reverse direction, that is, from the oil passage 67 side to the OSV 84 side. To do. The OSV 84 is an on-off valve that opens or shuts off the check valve 85 and the oil pump 83. A relief passage 88 including a relief valve 87 is connected to the main oil passage 82 downstream of the check valve 85. The relief passage 88 is a passage for returning the oil 80 in the main oil passage 82 to the oil pan 86, and the relief valve 87 is an on-off valve that opens or closes the relief passage 88.

The OSV 84 and the relief valve 87 are controlled by the electronic control unit 89 according to the maximum lift amount by the maximum lift amount variable mechanism 35 as follows.
<Maximum lift amount>
FIG. 11 shows a state where the maximum lift amount is maximized by the maximum lift amount variable mechanism 35. At this time, due to the oil pressure of the oil 80 in the oil pressure chamber 81, the pressure receiving surfaces 75 and 78 are separated most greatly from each other, the upper sheet 71 hits the stopper 65 of the seat case 61, and further rising is restricted. As described above, the upper seat 71 is positioned at the upper limit position of the movable range, so that the valve spring 25 is compressed most and the maximum spring load is maximized. Therefore, when the maximum lift amount is maximum, the maximum spring load required for causing the intake valve 21 to follow the intake cam 26 is large, but this requirement is satisfied. Such a state is realized by closing at least the relief valve 87 so that the oil 80 does not flow out of the hydraulic chamber 81. The OSV 84 may be closed to shut off the flow of the oil 80 into the hydraulic chamber 81, or may be opened to supply the oil 80 to the hydraulic chamber 81.

<Minimum maximum lift>
FIG. 10 shows a state when the maximum lift amount is minimized by the maximum lift amount varying mechanism 35. At this time, the OSV 84 is closed and the relief valve 87 is opened. The hydraulic pressure boosted by the oil pump 83 is not supplied to the hydraulic chambers 81 of the spring load changing devices 70 through the main oil passage 82, the oil passage 67, and the like, while the hydraulic pressure in the hydraulic chamber 81 is reduced to the relief passage 88, etc. Through the oil pan 86. The oil chamber 81 is almost free of oil 80, and the pressure receiving surface 75 of the upper sheet 71 is in contact with the pressure receiving surface 78 of the lower sheet 72. Since the upper seat 71 is positioned at the lower limit position of the movable range, the valve spring 25 is extended most and the maximum spring load is minimized. Therefore, when the maximum lift amount is minimum, the maximum spring load required for causing the intake valve 21 to follow the intake cam 26 is small, but this requirement is satisfied.

<In the middle of the maximum lift amount>
When the maximum lift amount is set to the intermediate state between the maximum and minimum values by the maximum lift amount variable mechanism 35, the pressure receiving surfaces 75 and 78 are separated from each other by the oil pressure of the oil 80 in the hydraulic chamber 81. The distance between the pressure receiving surfaces 75 and 78 is narrower than the maximum lift amount. Such a state is realized, for example, by closing both the OSV 84 and the relief valve 87 in a state where a predetermined amount of oil 80 is stored in the hydraulic chamber 81. By positioning the upper seat 71 at an intermediate position of the movable range (intermediate between the upper limit position in FIG. 11 and the lower limit position in FIG. 10), the valve spring 25 is compressed to a middle level, and the maximum spring load is between the above maximum and minimum values. It has become. Therefore, at the middle of the maximum lift amount, the maximum spring load required to cause the intake valve 21 to follow the intake cam 26 is medium, but this requirement is satisfied.

<When changing (increasing) the maximum lift amount>
When the maximum lift amount is increased from the minimum or the middle, the OSV 84 is opened by the electronic control unit 89 and the relief valve 87 is closed. The oil 80 boosted by the oil pump 83 is supplied to the hydraulic chamber 81 between the pressure receiving surface 75 of the upper seat 71 and the pressure receiving surface 78 of the lower seat 72 through the oil passage 67, the oil holes 68 and 79, the annular groove 76, and the like. Is done. As a result of this supply, a force is applied to the upper sheet 71 and the lower sheet 72 to cause the inclined surfaces 74 and 77 to rotate relative to each other while sliding each other. This relative rotation raises the upper seat 71 while separating the pressure receiving surfaces 75 and 78 from each other, compressing the valve spring 25 and increasing the maximum spring load.

  If the opening of the OSV 84 and the closing of the relief valve 87 are continued until the upper seat 71 hits the stopper 65 of the seat case 61, the further rise is stopped and the same as the maximum lift amount described above. It becomes the state of. If the OSV 84 is closed in addition to the relief valve 87 before the upper seat 71 hits the stopper 65, the maximum spring load is changed to a value larger than that before the change of the maximum spring load, although it is smaller than the maximum value. The

<When changing (decreasing) the maximum lift amount>
When the maximum lift amount is reduced from the maximum or from the middle, the electronic control unit 89 closes the OSV 84 and opens the relief valve 87. While the oil 80 boosted by the oil pump 83 is not supplied to each hydraulic chamber 81, the hydraulic chamber 81 is connected to the oil pan 86 through the relief passage 88 and the like. Here, the spring load of the valve spring 25 is applied to the upper seat 71 as a downward force. The inclined surfaces 74 and 77 of the upper sheet 71 and the lower sheet 72 are slidably in contact with each other. Therefore, the upper sheet 71 and the lower sheet 72 are relatively rotated, the upper sheet 71 is lowered, the pressure receiving surface 75 approaches the pressure receiving surface 78 of the lower sheet 72, and the oil 80 in the hydraulic chamber 81 is discharged. The oil 80 is returned to the oil pan 86 through the relief passage 88. After the upper sheet 71 reaches the lower limit position, the upper sheet 71 is held at the lower limit position unless the open / close state of the OSV 84 and the relief valve 87 is switched (see FIG. 10). As the upper seat 71 descends due to the relative rotation, the valve spring 25 extends and the maximum spring load decreases.

  If the valve closing of the OSV 84 and the opening of the relief valve 87 are continued until the pressure receiving surface 75 of the upper seat 71 contacts the pressure receiving surface 78 of the lower seat 72, the oil chamber 81 is almost free of oil 80, The upper seat 71 is positioned at the lower limit position of the movable range, and is in the same state as that at the time of the minimum maximum lift described above. When the relief valve 87 is closed in addition to the OSV 84 before the pressure receiving surface 75 contacts the pressure receiving surface 78, the maximum spring load is larger than the minimum value but smaller than that before the maximum spring load is changed. Changed to

According to the first embodiment described in detail above, the following effects can be obtained.
(1) The maximum spring load of the valve spring 25 is changed according to the maximum lift amount by the maximum lift amount variable mechanism 35. That is, the maximum spring load is maximized when the maximum lift amount is maximum, and is changed to a value smaller than the maximum when the maximum lift amount is not maximum. Therefore, the maximum spring load can be brought close to the required value corresponding to the maximum lift amount at that time. It is not necessary to drive the maximum lift amount variable mechanism 35 with a force larger than necessary, and it is possible to suppress a decrease in fuel consumption caused by driving the maximum lift amount variable mechanism 35 with an excessive force. Further, the actuator 39 can be reduced in size and cost.

(Second Embodiment)
Next, a second embodiment of the present invention will be described focusing on differences from the first embodiment.
Here, in order to ensure the followability of the intake valve 21 with respect to the intake cam 26, factors affecting the maximum spring load required for the valve spring 25 include the intake cam 21 in addition to the lift amount of the intake valve 21 described above. There are 26 rotational speeds. Generally, the required value of the maximum spring load is larger when the rotational speed of the intake cam 26 is high than when it is low. More precisely, the required value increases (in proportion) as the rotational speed of the intake cam 26 increases.

  Therefore, in the second embodiment, when the maximum lift amount by the maximum lift amount varying mechanism 35 is non-maximum, the degree of reduction in the maximum spring load is reduced as the rotational speed of the intake cam 26 is increased. In the engine 11, as described above, the rotation of the intake camshaft 27 and the rotation of the crankshaft 16 have a one-to-one correspondence. Therefore, here, the engine rotation speed is used as a substitute value for the rotation speed of the intake cam 26. Of course, the rotational speed of the intake cam 26 (intake cam shaft 27) may be used directly.

  As a scene to reduce the above degree, when the maximum lift amount is not changed such as <when the maximum lift amount is minimum> and <when the maximum lift amount is intermediate>, when the maximum lift amount is changed (increased), < For example, when the maximum lift amount is changed (when the maximum lift amount is changed (decreased)). In any scene, the open / close state of the OSV 84 and the relief valve 87 is controlled by the electronic control unit 89 so that the stop position of the upper seat 71 in the spring load changing device 70 increases as the engine rotational speed increases. When such control is performed, even if the maximum lift amount is the same, the amount of compression of the valve spring 25 by the upper seat 71 increases as the engine speed increases. The maximum spring load is increased on condition that the maximum spring load at the maximum lift amount is not exceeded, and is a value suitable for the maximum lift amount and the engine speed at that time.

Therefore, according to the second embodiment, in addition to the effect (1) described above, the following effect can be obtained.
(2) Focusing on the fact that the maximum spring load required for the valve spring 25 to cause the intake valve 21 to follow the intake cam 26 increases as the rotational speed of the intake cam 26 increases, the maximum lift variable mechanism 35 When the maximum lift amount is not maximum, the higher the engine speed, the smaller the degree to which the maximum spring load is reduced. Therefore, the maximum spring load can be made closer to the required value that changes according to the engine rotation speed.

(Third embodiment)
Next, a third embodiment of the present invention will be described focusing on differences from the first and second embodiments.

  In the maximum lift amount variable mechanism 35, as described above, the force toward the direction in which the maximum lift amount is reduced acts on the slider 48 by the intake cam 26 and the valve spring 25. Focusing on this action, in the present embodiment, the maximum lift amount is maximized when the maximum lift amount is changed by the maximum lift amount varying mechanism 35, that is, when <maximum lift amount change (decrease)>. The maximum spring load is made larger than before the change on condition that the maximum spring load at the time is not exceeded.

  Due to the increase in the maximum spring load, a force for displacing the slider 48 in the same direction is strengthened. As a result, the moving speed of the control shaft 38 and the slider 48 in the axial direction increases, and the relative phase difference between the input arm 41 and the output arms 42 and 43 is changed quickly. In this way, the change speed of the maximum lift amount by the maximum lift amount variable mechanism 35 is increased, and the response of the change is improved.

Therefore, according to the third embodiment, in addition to the effects (1) and (2) described above, the following effects can be obtained.
(3) When the maximum lift amount is changed in the direction in which the maximum lift amount is reduced by the maximum lift amount variable mechanism 35, the maximum spring load is made larger than before the change on condition that the maximum spring load at the maximum lift amount is not exceeded. I am doing so. Therefore, the responsiveness can be improved by increasing the changing speed when the maximum lift amount is reduced by the maximum lift amount variable mechanism 35.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described with reference to FIG. 12, focusing on differences from the first to third embodiments (configuration of the spring load changing device). In addition, about the member similar to 1st-3rd embodiment, a location, etc., the same code | symbol is attached | subjected and description is abbreviate | omitted.

  The spring load changing device 90 of the fourth embodiment changes the spring load by switching the spring constant, and includes an auxiliary retainer 91 between the retainer 24 at the upper end of the intake valve 21 and the spring seat 20. have. The auxiliary retainer 91 has a through hole 92 through which the intake valve 21 is inserted. Therefore, the auxiliary retainer 91 can move relative to the intake valve 21.

  The valve spring 25 is divided into a plurality (two in FIG. 12) of spring constituent bodies 93 and 94 in the length direction. The upper spring structure 93 is interposed around the intake valve 21 and between the retainer 24 and the auxiliary retainer 91. Further, the lower spring constituting body 94 is interposed around the intake valve 21 and between the auxiliary retainer 91 and the spring seat 20.

  The auxiliary retainer 91 is connected to the cylinder head 14 via a hydraulic cylinder 95. More specifically, the cylinder 95 </ b> A of the hydraulic cylinder 95 is fixed to the cylinder head 14, and the piston 95 </ b> B is fixed to the auxiliary retainer 91. In order to supply the oil 103 into the cylinder 95A, an oil pump 98, an OSV 99, and a check valve 100 are disposed in an oil passage 97 connecting the cylinder 95A and the oil pan 96.

  The oil pump 98 sucks the oil 103 in the oil pan 96 and discharges it to the oil passage 97. The check valve 100 allows the oil 103 to flow from the oil pump 98 through the oil passage 97 into the cylinder 95A, and prevents the oil 103 from flowing back in the opposite direction, that is, from the cylinder 95A side to the OSV 99 side. The OSV 99 is an on-off valve that opens or blocks between the check valve 100 and the oil pump 98.

  In addition, a relief passage 102 including a relief valve 101 is connected to the oil passage 97 on the downstream side of the check valve 100 in order to discharge the oil 103 from the cylinder 95A. The relief passage 102 is a passage for returning the oil 103 in the oil passage 97 to the oil pan 96, and the relief valve 101 is an on-off valve that opens or closes the relief passage 102.

  The OSV 99 and the relief valve 101 are controlled by the electronic control unit 89 according to the maximum lift amount by the maximum lift amount variable mechanism 35. When the maximum lift amount by the maximum lift amount varying mechanism 35 is maximum, both the OSV 99 and the relief valve 101 are closed while the oil 95 is filled in the cylinder 95A. By closing these valves, the inflow / outflow of the oil 103 to / from the cylinder 95A is blocked, and the piston 95B cannot reciprocate. As a result, the auxiliary retainer 91 becomes immovable (locked) with respect to the cylinder head 14. The distance between the spring seat 20 and the auxiliary retainer 91 is constant, and the lower spring structure 94 does not expand and contract regardless of the reciprocating motion of the intake valve 21. That is, the spring structure 94 does not function as a valve spring. Only the upper spring structure 93 functions as a valve spring. Accordingly, in this case, the substantial length of the valve spring 25 is shortened and the spring constant is increased by the amount that the lower spring structure 94 does not function, and the maximum spring load is increased accordingly.

  When the maximum lift amount is changed by the maximum lift amount variable mechanism 35 so that the maximum lift amount becomes smaller, the OSV 99 is closed and the relief valve 101 is opened. While the hydraulic pressure raised by the oil pump 98 is not supplied into the cylinder 95A, the oil 103 in the cylinder 95A is discharged to the oil pan 96 through the relief passage 102, and the piston 95B can reciprocate freely. Along with this, the auxiliary retainer 91 is movable (free) with respect to the cylinder head 14, and the expansion and contraction of the upper spring structure 93 accompanying the reciprocating movement of the intake valve 21 is performed via the auxiliary retainer 91. Transmitted to the body 94. By this transmission, in addition to the spring structure 93, the spring structure 94 expands and contracts. Thus, since both the spring structural bodies 93 and 94 function as valve springs, the substantial length of the valve spring 25 increases, the spring constant decreases, and the maximum spring load decreases.

  When the maximum lift amount is changed by the maximum lift amount variable mechanism 35 from the above state, the OSV 99 is opened and the relief valve 101 is closed. The oil 103 whose pressure has been increased by the oil pump 98 is supplied into the cylinder 95A. When both the OSV 99 and the relief valve 101 are closed with the oil 103 filled in the cylinder 95A, the inflow / outflow of the oil 103 to / from the cylinder 95A is blocked, and the piston 95B cannot reciprocate. The auxiliary retainer 91 is locked, and the lower spring structure 94 does not expand and contract. The spring constant of the valve spring 25 increases, and the maximum spring load increases.

Therefore, the fourth embodiment can provide the same effects as those of the first to third embodiments.
Note that the present invention can be embodied in another embodiment described below.
In the second embodiment, when the maximum lift amount by the maximum lift amount variable mechanism 35 is not maximum, the degree of decreasing the maximum spring load may be smaller when the engine speed is high than when it is low. For example, a rotation speed region that can be taken by the engine rotation speed may be divided into a plurality of parts, and the degree may be varied for each of the divided areas.

  -In 4th Embodiment, while dividing the valve spring 25 into three or more spring structure bodies, an auxiliary retainer is arrange | positioned between adjacent spring structure bodies. Then, each auxiliary retainer 91 may be connected to the cylinder head 14 so as not to move, or the connection may be released.

The variable valve characteristic device may change only one of the maximum lift amount and the working angle of the intake / exhaust valves 21 and 22 and change the valve characteristic.
The present invention is also applicable to an internal combustion engine provided with a valve characteristic variable device that changes the valve characteristic of the exhaust valve 22 instead of or in addition to the intake valve 21.

-You may change a spring load change apparatus into the type different from what was used in the said each embodiment.
-You may change suitably the structure of the maximum lift amount variable mechanism 35 in each said embodiment.

For example, the support pipe 37 may be omitted, and the control shaft 38 may function as the support pipe 37.
Further, the helical angles of the helical splines 42B and 48B and the helical splines 43C and 48C may be the same. In this case, the two intake valves 21 and 21 for each cylinder 12 reciprocate with the same maximum lift amount.

  Further, the helical angles of the helical splines 42B and 48B and the helical splines 43C and 48C may be different from each other. In this way, even in the same cylinder 12, the two intake valves 21 and 21 reciprocate with different maximum lift amounts. By causing air to be sucked into the combustion chamber 17 from the two intake valves 21 and 21 at different flow rates or at different timings, a swirl flow such as swirl is generated in the combustion chamber 17, thereby improving the combustibility and improving the engine 11. It becomes possible to improve the performance.

  The above-described content provides a difference in the maximum lift amount by making the torsion angles of the helical splines 42B, 48B or 43C, 48C different. Alternatively, a difference may be provided in the maximum lift amount by providing a difference in the phase position of the nose 47 of the output arms 42 and 43, or by providing a difference in the shape of the cam surface 47A of the nose 47.

  Further, the rocker arm 56 between the mediation drive mechanism 36 and the intake valve 21 may be omitted. In this case, for example, the intake valve 21 is provided with a valve lifter, and the nose 47 of the output arms 42 and 43 is brought into direct contact with the valve lifter. Then, the intake valve 21 may be pushed down via the valve lifter by swinging the output arms 42 and 43.

  Further, instead of the direct contact of the nose 47, the nose 47 may be indirectly contacted with the valve lifter via a roller. In this case, a roller may be supported by the nose 47 and the roller may be brought into rolling contact with the valve lifter, or a roller may be supported by the valve lifter and the roller may be brought into rolling contact with the nose 47.

  A variable maximum valve lift mechanism different from that used in each of the above embodiments may be used as the variable valve characteristic device.

The fragmentary sectional view of the engine upper part in a 1st embodiment which materialized the present invention. The top view which shows a cylinder head upper part. The perspective view which shows the mediation drive mechanism in the maximum lift amount variable mechanism. The side view which shows the slider etc. in a mediation drive mechanism. Sectional drawing which shows the internal structure of a mediation drive mechanism. The fragmentary sectional view which shows the relationship between the control shaft, support pipe, slider, etc. in a mediation drive mechanism. (A), (B) is a fragmentary sectional view which shows the effect | action of a mediation drive mechanism. The characteristic view which shows the valve characteristic of an intake / exhaust valve. (A) is the perspective view which looked at the upper sheet | seat used for a spring load change apparatus from diagonally downward, (B) is the perspective view which looked at the lower sheet from diagonally upward. The fragmentary sectional view explaining the effect | action of a spring load change apparatus. The fragmentary sectional view explaining the effect | action of a spring load change apparatus. The fragmentary sectional view which shows the spring load change apparatus in 4th Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Gasoline engine (internal combustion engine), 21 ... Intake valve (engine valve), 22 ... Exhaust valve (engine valve), 25 ... Valve spring, 26 ... Intake cam, 29 ... Exhaust cam, 35 ... Maximum lift amount variable mechanism ( Valve characteristic variable device), 38 ... control shaft, 39 ... actuator, 41 ... input arm, 42, 43 ... output arm, 48 ... slider, 70, 90 ... spring load changing device (spring load changing means).

Claims (6)

An internal combustion engine having a valve characteristic variable device that changes at least one of a maximum lift amount and an operating angle of an engine valve that is opened against a valve spring by a cam as a valve characteristic, and changes the valve characteristic according to an engine operating state In
There is provided a valve characteristic variable device provided with spring load changing means for changing the maximum spring load of the valve spring when the engine valve lifts the maximum amount according to the valve characteristic by the valve characteristic variable device. Internal combustion engine. 2. The variable valve characteristic device according to claim 1, wherein the spring load changing unit is configured to make the maximum spring load smaller than a maximum value when the valve characteristic is changed to non-maximum or non-maximum by the valve characteristic variable device. Internal combustion engine. The spring load changing means reduces the degree of decreasing the maximum spring load when the valve characteristic is not maximum by the valve characteristic variable device and when the cam rotation speed is high, compared to when the cam speed is low. An internal combustion engine comprising the valve characteristic variable device according to Item 2. The internal combustion engine having the valve characteristic varying device according to claim 3, wherein the spring load changing means reduces the degree of decreasing the maximum spring load as the rotational speed of the cam increases. The valve characteristic variable device is:
A control shaft that is moved in the axial direction by an actuator;
An input arm and an output arm provided on the control shaft so as to be swingable,
The control shaft and a slider provided between the input arm and the output arm are provided, and the swing of the input arm caused by the cam is transmitted to the output arm via the slider to control the engine valve. 2. The valve characteristic is changed by driving and changing a relative phase difference between the input arm and the output arm by a displacement of the slider accompanying an axial movement of the control shaft by the actuator. An internal combustion engine comprising the valve characteristic variable device according to any one of? A force in the direction of reducing the valve characteristic acts on the slider of the valve characteristic variable device with respect to the axial direction of the control shaft by at least the valve spring,
The spring load changing means changes the maximum spring load on condition that the maximum spring load at the maximum time of the valve characteristic is not exceeded when the valve characteristic is changed by the valve characteristic variable device in a direction of decreasing. An internal combustion engine comprising the variable valve characteristic device according to claim 5, which is larger than before.

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