JP4325525B2 - Variable valve mechanism - Google Patents

Description

  The present invention relates to a variable valve mechanism having an operating angle variable mechanism for opening and closing valves such as an intake valve and an exhaust valve of an internal combustion engine and changing an operating angle of a cam related to opening of the valve. It is.

  A general valve mechanism of an internal combustion engine employs a configuration in which an engine valve urged in a valve closing direction by a valve spring is opened directly by a camshaft cam or via a rocker arm or the like. ing.

  On the other hand, in recent years, a valve operating mechanism (variable valve operating mechanism) provided with a variable working angle mechanism has been proposed. The operating angle variable mechanism is a mechanism that can change the operating angle of the cam related to the opening of the engine valve in accordance with the operating state of the internal combustion engine.

  As one form of the said variable valve mechanism, what was described in patent document 1, for example is mentioned. As shown in FIGS. 15 and 16, the variable operating angle mechanism of the variable valve mechanism includes a support pipe 81, a control shaft 82, an input arm 83, a pair of output arms 84 and 85, and a slider 86.

  The support pipe 81 is fixed to the cylinder head, and the control shaft 82 is inserted into the support pipe 81 so as to reciprocate. The input arm 83 and the output arms 84 and 85 are provided on the support pipe 81 so as to be swingable. The input arm 83 is provided with a cam input portion 87, and the pressing force of the cam 89 accompanying the rotation of the cam shaft 88 is transmitted to the input arm 83 through the cam input portion 87. Each of the output arms 84 and 85 includes a base circle portion 91 and a nose 92. The slider 86 is interposed between the support pipe 81 and the input / output arms 83 to 85, and is engaged with the input / output arms 83 to 85 by helical splines. A rocker arm 94 is disposed between the output arms 84 and 85 and the engine valve 93, and a roller 95 of the rocker arm 94 is in contact with the output arms 84 and 85.

  According to the operating angle variable mechanism 97 having the above-described configuration, when the cam input portion 87 is pushed down by the cam 89 and the input arm 83 is swung downward, the rocking motion is output via the slider 86 to the output arms 84 and 85. The output arms 84 and 85 are swung downward. At this time, the locations where the output arms 84 and 85 are in contact with the roller 95 (the base circular portion 91 and the nose 92) change with the swing. When the output arms 84 and 85 are in contact with the roller 95 at the base circle 91, even if the output arms 84 and 85 swing, the rocker arm 94 does not swing and the engine valve 93 does not open. On the other hand, when the output arms 84 and 85 are in contact with the roller 95 at the nose 92, the rocker arm 94 also swings as the output arms 84 and 85 swing, and the engine valve 93 resists the valve spring 96. To open the valve. The engine valve 93 is greatly opened as the contact point of the roller 95 with the nose 92 approaches the tip of the nose 92.

  When the control shaft 82 is moved in the axial direction, the slider 86 is displaced in the same direction in conjunction with the movement. The relative phase difference between the input / output arms 83 to 85 is changed by the rotation of the slider 86 accompanying this displacement. With this change, the section of the base circle 91 and the nose 92 of the output arms 84 and 85 in contact with the roller 95 changes. The portion occupied by the base circle portion 91 in this section is short when the relative phase difference is large, and becomes longer as the relative phase difference is smaller. As described above, when the roller 95 is in contact with the base circle portion 91, the engine valve 93 is not opened. Further, as the section of the nose 92 relating to contact with the roller 95 becomes shorter, the amount of movement (lift amount) of the engine valve 93 decreases. Therefore, when the relative phase difference is large, the valve opening period (working angle) is large, and as the relative phase difference is small, the valve opening period (working angle) is small.

  In the operating angle variable mechanism 97, when the roller 95 is in contact with the nose 92, the cam input portion 87 is rotated clockwise in FIG. A rotational biasing force is applied to rotate in the direction. The input / output arms 83 to 85 are biased by this rotational biasing force, and the cam input portion 87 is pressed against the cam 89. On the other hand, when the roller 95 is in contact with the base circle portion 91, the rotational biasing force due to the compression reaction force of the valve spring 96 is very small. When this rotational biasing force is less than the minimum rotational biasing force necessary for pressing the cam input portion 87 against the cam 89 (hereinafter referred to as a required value), the cam input portion 87 is moved from the cam 89. There is a risk of leaving.

  In the variable operating angle mechanism 97, an inertial force is generated as the input / output arms 83 to 85 swing. When the cam input part 87 changes from descending to ascending, the cam input part 87 continues to descend due to the inertial force. The cam input portion 87 tends to move away from the cam 89, and the pressing force of the cam input portion 87 against the cam 89 due to the rotational biasing force is weakened.

  Therefore, a lost motion device 98 is provided in the variable valve mechanism to cope with the above-described problems. The device 98 is provided with a lost motion spring 99 in a compressed state that urges the input arm 83 in the opposite direction (clockwise direction in FIG. 16) to the swinging direction of the input arm 83 when the cam 89 is pushed down. Has been. With this arrangement, the rotation biasing force by the lost motion device 98 acts on the input arm 83 in addition to the rotation biasing force caused by the compression reaction force of the valve spring 96. Therefore, even if the operating angle is small as described above and the rotational biasing force due to the compression reaction force of the valve spring is less than the required value, the shortage is compensated by the rotational biasing force by the lost motion device 98. be able to. And the cam input part 87 is pressed against the cam 89, and the malfunction which the cam input part 87 leaves | separates from the cam 89 can be suppressed.

  Incidentally, the rotational urging force due to the compression reaction force of the valve spring 96 becomes smaller as the operating angle becomes smaller. This is because, as the operating angle decreases, the portion occupied by the base circular portion 91 becomes longer in the contact section between the output arms 84 and 85 and the roller 95. On the other hand, the spring constant of the lost motion spring 99 is constant. Therefore, when the cam input portion 87 is surely pressed against the cam 89 regardless of the operating angle, the required value is insufficient on the basis of a small operating angle at which the rotational urging force due to the compression reaction force of the valve spring 96 becomes small. The rotational urging force by the lost motion device 98 necessary to compensate for the minute is set.

Further, the inertial force generated by the swinging of the input / output arms 83 to 85 is small when the rotational speed of the cam 89 (camshaft 88) is low, but increases as the rotational speed increases. On the other hand, as described above, the spring constant of the lost motion spring 99 is constant. Therefore, if the cam input portion 87 is surely pressed against the cam 89 regardless of the rotational speed of the cam 89, it is necessary to make up for the shortage with respect to the above required value on the basis of the high rotational speed at which the inertial force increases. The rotational urging force by the lost motion device 98 is set.
JP 2001-263015 A

  However, if the rotational biasing force by the lost motion device 98 is set based on the small operating angle as described above, the rotational biasing force due to the compression reaction force of the valve spring 96 and the lost motion device 98 at the non-small operating angle. The sum total with the rotational urging force due to is over the required value. As a result, the cam input portion 87 is pressed against the cam 89 with a force greater than necessary, and the lost motion device 98 is pressed against the input arm 83. Accordingly, the friction generated at the contact portion between the cam input portion 87 and the cam 89 and the friction generated at the contact portion between the input arm 83 and the lost motion device 98 become unnecessarily large.

  Further, if the rotational biasing force by the lost motion device 98 is set based on the high rotational speed of the cam 89, the inertia force accompanying the swinging of the input / output arms 83 to 85 is small at the non-high rotational speed, and the cam input section 87. The degree of weakening the pressing force against the cam 89 is reduced. For this reason, the sum of both rotational urging forces by the valve spring 96 and the like and the lost motion device 98 becomes larger than the required value. In this case as well, the cam input portion 87 is pressed against the cam 89 and the lost motion device 98 is pressed against the input arm 83 with an unnecessarily large force, and the friction becomes unnecessarily large.

  The present invention has been made in view of such circumstances, and the object thereof is to reduce the friction as compared with the case where the rotational urging force by the lost motion device is made constant while the cam input portion is reliably pressed against the cam. It is an object of the present invention to provide a variable valve mechanism that can perform this.

In the following, means for achieving the above object and its effects are described.
According to the first aspect of the present invention, the rotation of the cam is transmitted to the input arm through the cam input unit to swing the input arm, and the output arm that swings in conjunction with the input arm resists the valve spring. Then, the valve is opened, and the relative phase difference in the swing direction of the input arm and the output arm is changed, so that the working angle of the cam related to the valve opening is changed to the maximum lift amount of the valve. And an operating angle variable mechanism that changes together, and a lost motion device that urges the input arm to rotate in the same direction as the direction in which the rotation urging force by the valve spring acts in order to press the cam input portion against the cam. A variable valve mechanism provided with an area defined by an operating angle of the cam, wherein the loss is larger in a region where the operating angle is large than in a small region. The biasing force changing means for reducing the rotational bias is provided by the motion device.

According to the above configuration, in the variable valve mechanism, the rotation of the cam is transmitted to the input arm through the cam input portion by the operating angle variable mechanism, and the input arm swings. The output arm swings in conjunction with the swing, and the valve is opened against the valve spring by the swing. Further, when the relative phase difference in the swing direction of the input arm and the output arm is changed, the working angle of the cam related to the valve opening is changed together with the maximum lift amount of the valve .

In the variable valve mechanism, a rotational urging force is applied to the output arm to rotate the cam input portion in the direction of approaching the cam due to the compression reaction force of the valve spring. This rotational biasing force is also transmitted to the input arm. Further, the lost motion device applies a rotation biasing force that biases the input arm in the same direction as the direction in which the rotation biasing force by the valve spring acts on the operating angle variable mechanism. The direction in which both rotational urging forces by these valve springs and the lost motion device act is the same. Accordingly, the input arm is biased by the both-rotation biasing force, and the cam input portion is pressed against the cam.

  On the other hand, when the input / output arm swings, friction is generated at a contact portion between the cam input portion and the cam and a contact portion between the operating angle variable mechanism and the lost motion device. This friction increases as the sum of the rotational urging forces increases. Therefore, from the viewpoint of preventing the cam input portion from separating from the cam and minimizing the friction as much as possible, the total of the rotational urging forces is the minimum rotational urging force required to press the cam input portion against the cam. It is desirable to be close to (hereinafter referred to as a required value).

By the way, the rotational biasing force by the valve spring or the like becomes smaller as the operating angle becomes smaller with the maximum lift amount of the valve, and the pressing force of the cam input portion against the cam decreases. Therefore, even in a situation where the pressing force is small, if an attempt is made to make the sum of both rotational urging forces close to the above required value, if the rotational urging force by the lost motion device is made constant, the rotational urging force is expressed as an operating angle. This is set based on a small area. However, in a region other than the above, the total sum of both rotational urging forces is larger than the required value. As a result, the cam input portion is pressed against the cam with a force greater than necessary, and the lost motion device is pressed against the operating angle variable mechanism.

  On the other hand, in the first aspect of the present invention, with respect to the region defined by the cam working angle by the biasing force changing means, the rotational biasing force by the lost motion device is larger in the region having the same working angle than in the small region. Is reduced. Therefore, by changing the rotational biasing force, the total sum of both rotational biasing forces can be set to a value close to the required value regardless of whether the operating angle is large or small. As a result, regardless of the operating angle of the cam, the cam input portion can be pressed against the cam so as not to leave the cam. Further, the friction can be reduced as compared with the case where the rotational biasing force by the lost motion device is constant.

  The invention according to claim 2 is a variable valve mechanism having a working angle variable mechanism and a lost motion device similar to those of the invention according to claim 1, wherein the region defined by the rotational speed of the cam is An urging force changing means for reducing the rotational urging force by the lost motion device is provided in the low rotation speed region than in the high region.

According to the above configuration, in the variable valve mechanism, the valve is opened by the operating angle variable mechanism and the operating angle of the cam is changed together with the maximum lift amount of the valve in the same manner as in the first aspect of the invention. The Further, a rotational urging force by a valve spring or the like acts on the input arm through the output arm, and a rotational urging force by the lost motion device acts on the operating angle variable mechanism.

  In the variable operating angle mechanism, an inertial force is generated as the input / output arm swings. When the cam input unit turns from descending to ascending as the input / output arm swings, the cam input unit tends to continue descending due to the inertial force. The cam input portion tends to move away from the cam, and the pressing force of the cam input portion against the cam is weakened.

  Further, as the input / output arm swings, friction occurs at the contact portion between the cam input portion and the cam and the contact portion between the operating angle variable mechanism and the lost motion device. This friction increases as the sum of the rotational biasing forces increases.

  Therefore, from the viewpoint of reducing the friction as much as possible while keeping the cam input portion away from the cam, the total rotational biasing force is the minimum value of the rotational biasing force (required value) required to press the cam input portion against the cam. ) Is desirable.

  By the way, as the rotational speed of the cam increases, the inertial force increases, and the degree of weakening the pressing force of the cam input portion against the cam increases. This situation of increasing magnitude occurs when the cam rotates at high speed. Even in such a situation, if the total rotational urging force is set to a value close to the above-mentioned required value, the rotational urging force by the lost motion device is constant, and the rotational urging force is based on the region where the cam rotation speed is high. Will be set. However, in a region other than the above, the total rotational urging force becomes larger than the required value. As a result, the cam input portion is pressed against the cam with a force greater than necessary, and the lost motion device is pressed against the operating angle variable mechanism.

  On the other hand, in the invention according to claim 2, the biasing force change means causes the rotation biasing force by the lost motion device to be higher than the higher region in the region where the rotational speed is low in the region defined by the rotational speed of the cam. Is reduced. Therefore, by changing this rotational biasing force, the decrease in the pressing force due to the inertial force is appropriately compensated for in both the high and low rotational speeds of the cam, and the sum of both rotational biasing forces is a value close to the required value. It becomes possible to. As a result, regardless of the rotational speed of the cam, the cam input portion can be pressed against the cam so as not to leave the cam. Further, the friction can be reduced as compared with the case where the rotational biasing force by the lost motion device is constant.

  According to a third aspect of the present invention, there is provided a variable valve mechanism having a working angle variable mechanism and a lost motion device similar to those of the first aspect of the invention, which are defined by a working angle and a rotational speed of the cam. For the region, at least in the region where the working angle is large and the rotational speed is low, an urging force changing means for reducing the rotational urging force by the lost motion device is provided compared to the region where the working angle is small and the rotational speed is high. ing.

According to the above configuration, in the variable valve mechanism, the valve is opened by the operating angle variable mechanism and the operating angle of the cam is changed together with the maximum lift amount of the valve in the same manner as in the first aspect of the invention. The Further, a rotational urging force by a valve spring or the like acts on the input arm through the output arm, and a rotational urging force by the lost motion device acts on the operating angle variable mechanism.

  In the variable operating angle mechanism, an inertial force is generated as the input / output arm swings. When the cam input unit turns from descending to ascending as the input / output arm swings, the cam input unit tends to continue descending due to the inertial force. The cam input portion tends to move away from the cam, and the pressing force of the cam input portion against the cam is weakened.

  Further, as the input / output arm swings, friction occurs at the contact portion between the cam input portion and the cam and the contact portion between the operating angle variable mechanism and the lost motion device. This friction increases as the sum of the rotational biasing forces increases.

  Therefore, from the viewpoint of reducing the friction as much as possible while keeping the cam input portion away from the cam, the total rotational biasing force is the minimum value of the rotational biasing force (required value) required to press the cam input portion against the cam. ) Is desirable.

  By the way, the rotational urging force by the valve spring or the like becomes smaller as the operating angle becomes smaller, and the pressing force of the cam input portion against the cam decreases. Further, as the cam rotation speed increases, the inertial force generated with the swing of the input / output arm increases, and the degree of weakening the pressing force of the cam input portion against the cam increases.

  Therefore, if the cam rotates at a high speed when the operating angle is small, the pressing force of the cam input portion against the cam becomes very small. Therefore, even in such a situation, if the total rotational urging force is set to a value close to the above required value, if the rotational urging force by the lost motion device is made constant, the rotational urging force is reduced with a small cam operating angle and rotation. The high speed area is set as a reference. However, in a region other than the above, the total rotational urging force becomes larger than the required value. As a result, the cam input portion is pressed against the cam with a force greater than necessary, and the lost motion device is pressed against the operating angle variable mechanism.

  On the other hand, in the invention according to the third aspect, with respect to the region defined by the cam working angle and the rotational speed by the biasing force changing means, the working angle is at least in the region where the working angle is large and the rotational speed is low. The rotational urging force by the lost motion device is made smaller than the region where the rotation speed is small. Therefore, by changing this rotational biasing force, the total rotational biasing force can be made close to the required value even in a region where the operating angle is large and the rotational speed is low, or in a region where the operating angle is small and the rotational speed is high. It becomes possible. As a result, the cam input portion can be pressed against the cam so as not to be separated from the cam regardless of the operating angle of the cam or the rotational speed of the cam. Further, the friction can be reduced as compared with the case where the rotational biasing force by the lost motion device is constant.

The working angle variable mechanism in the invention described in any one of claims 1 to 3 is, for example, according to the invention described in claim 4, rotatable between the cam and the valve and in the axial direction. And a slider that is engaged with each of the input arm and the output arm by a helical spline, and the input arm and the output arm are rotated by rotation of the slider in the axial direction. It is possible to adopt one that changes the relative phase difference of the output arm and changes the operating angle of the cam together with the maximum lift amount of the valve .

  According to this type of operating angle variable mechanism, since the input arm and the output arm are meshed with the slider by the helical spline, when the input arm is swung by the cam, the swing is caused via the slider. It is transmitted to the output arm. By this transmission, the output arm swings and the valve is driven to open and close.

In addition to the basic operation described above, when the slider is displaced in the axial direction, the input arm and the output arm are twisted by the rotation of the slider accompanying the displacement, and the relative phase difference between them is changed to change the cam working angle. Is changed with the maximum lift amount of the valve .

  Further, according to the invention described in claim 5, as the output arm in the invention described in any one of claims 1 to 4, a base circle portion and a nose protruding from the outer peripheral surface of the base circle portion are provided. Further, between the output arm and the valve, the oscillation of the output arm is not transmitted to the valve when contacting the base circle, and the output arm when contacting the nose. A transmission mechanism may be provided for transmitting the oscillation of the motor to the valve.

  According to the above configuration, when the input / output arm is swung as the cam rotates, the section (base circle and nose) in contact with the transmission mechanism in the output arm changes as the cam swings. When the nose contacts the transmission mechanism in this contact section, the swing of the output arm is transmitted to the valve via the transmission mechanism. By this transmission, the valve is lifted and opened. Further, when the base circle portion contacts the transmission mechanism in the contact section, even if the output arm swings, the swing is not transmitted to the valve via the transmission mechanism, and the valve does not lift.

  And the part which a base circle part and a nose each occupy in the said contact area changes according to the relative phase difference of an input / output arm. For example, when the relative phase difference is small, the portion occupied by the base circle in the contact section (the portion not related to valve opening) becomes longer, and the portion occupied by the nose (the portion related to valve opening) becomes shorter, The period during which the valve lifts (opening period) is shortened. On the other hand, when the relative phase difference is large, the portion occupied by the base circle portion in the contact section becomes shorter, the portion occupied by the nose becomes longer, and the period during which the valve lifts (valve opening period) becomes longer.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 1, a multi-cylinder gasoline engine (hereinafter simply referred to as an engine) 11 as an internal combustion engine is mounted on the vehicle. The engine 11 includes a cylinder block 13 having a plurality of cylinders 12 and a cylinder head 14 disposed on the upper side of the cylinder block 13. A piston 15 is accommodated in each cylinder 12 so as to be able to reciprocate. Each piston 15 is connected to a crankshaft 16 that is an output shaft via a connecting rod (not shown). Therefore, when each piston 15 reciprocates, the movement is converted into a rotational movement by the connecting rod and then transmitted to the crankshaft 16. In FIG. 1, the crankshaft 16 is shown rotated by 90 degrees with respect to other members such as the cylinder block 13.

  A space above the piston 15 in each cylinder 12 is a combustion chamber 17. Each combustion chamber 17 is connected to an intake port 18 that forms a part of the intake passage, and air outside the engine 11 passes through the intake passage and is taken into the combustion chamber 17. The combustion chamber 17 is connected to an exhaust port 19 that forms a part of the exhaust passage, and combustion gas generated in the combustion chamber 17 is discharged to the outside of the engine 11 through the exhaust passage.

  The cylinder head 14 is provided with an intake valve 21 for opening and closing the intake port 18 and an exhaust valve 22 for opening and closing the exhaust port 19 for each cylinder 12 as an engine valve. In the present embodiment, a pair of these intake / exhaust valves 21 and 22 are provided per cylinder. The same type of valves 21 and 21 (or 22, 22) are arranged side by side in the cylinder arrangement direction (in FIG. 1, the direction orthogonal to the paper surface). The intake / exhaust valves 21 and 22 are all urged by a valve spring 23 in a direction in which the intake / exhaust ports 18 and 19 are closed (valve closing direction, substantially upward in FIG. 1). An intake cam shaft 25 having an intake cam 24 is rotatably supported substantially above the intake valve 21 in the cylinder head 14. Similarly, an exhaust camshaft 28 having an exhaust cam 27 is rotatably supported substantially above the exhaust valve 22 in the cylinder head 14.

  The intake / exhaust camshafts 25 and 28 are drivingly connected to the crankshaft 16 by a timing chain, a sprocket (not shown) or the like. The rotation of the crankshaft 16 is transmitted to the intake / exhaust camshafts 25 and 28 via a timing chain or the like. The intake / exhaust valves 24, 27 are pushed down against the valve spring 23 by the rotation of the intake / exhaust cams 24, 27. By this depression, the intake / exhaust ports 18, 19 are opened (opened state).

  A fuel injection valve 29 is attached to the cylinder head 14 corresponding to each cylinder 12. The fuel injected from the fuel injection valve 29 is mixed with the intake air passing through the intake port 18 and becomes an air-fuel mixture. Note that fuel may be directly injected from the fuel injection valve 29 to the combustion chamber 17 without going through the intake port 18.

  A spark plug 31 is attached to the cylinder head 14 corresponding to each cylinder 12. The air-fuel mixture is ignited by spark discharge of the spark plug 31, 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 engine 11 is provided with a variable valve timing mechanism 32 and a variable operating angle mechanism 33 as variable valve mechanisms that change the valve characteristics of the intake valve 21.
The variable valve timing mechanism 32 continuously changes the valve timing of the intake valve 21 with respect to the crank angle (the rotation angle of the crankshaft 16) by changing the relative rotation phase of the intake camshaft 25 with respect to the crankshaft 16. Mechanism. The valve timing of the intake valve 21 can be expressed by, for example, a valve opening timing IVO and a valve closing timing IVC of the intake valve 21 as shown in FIG. The valve timing is advanced or retarded in a state where the valve opening period of the intake valve 21 (the period from the valve opening timing IVO to the valve closing timing IVC) is kept constant. Note that EVO and EVC in FIG. 2 are the opening timing and closing timing of the exhaust valve 22, respectively.

  On the other hand, the operating angle variable mechanism 33 is a mechanism for continuously changing the operating angle θ of the intake cam 24. Here, as shown in FIG. 3, the operating angle θ is an angle range from the valve opening timing IVO to the valve closing timing IVC of the intake valve 21 with respect to the rotation of the intake cam 24 (expressed by the crank angle in FIG. 3). In the present embodiment, the maximum lift amount of the intake valve 21 is continuously changed by the operating angle variable mechanism 33 in addition to the operating angle θ. The maximum lift amount is a movement amount of the intake valve 21 when the intake valve 21 is moved (lifted) to the lowest position when the intake valve 21 is opened. The operating angle θ and the maximum lift amount are changed in synchronization with each other by the operating angle variable mechanism 33. For example, the maximum lift amount decreases as the operating angle θ decreases. As the operating angle θ decreases, the valve opening timing IVO and the valve closing timing IVC of the intake valve 21 approach each other, the valve opening period becomes shorter, and the amount of intake air per cylinder 12 decreases.

  As shown in FIG. 4, the operating angle variable mechanism 33 includes a mediating drive mechanism 34 for each cylinder 12, and also includes a support pipe 35, a control shaft 36, and an actuator 37. The support pipe 35 is disposed so as to extend in the arrangement direction of the cylinders 12 (substantially left-right direction in FIG. 4), and is fixed to the support wall portion 26 (see FIG. 6) of the cylinder head 14. Note that this direction is referred to as an “axial direction” when it is not necessary to distinguish, and an arrow X direction or an arrow Y direction when it is necessary to distinguish. The arrow X direction is a direction in which the operating angle θ of the intake cam 24 is decreased, and the arrow Y direction is a direction in which the operating angle θ is increased. Due to the fixing, the support pipe 35 cannot move in the axial direction and cannot rotate. The control shaft 36 is inserted into the support pipe 35. The actuator 37 includes an electric motor and a conversion mechanism that converts the rotation of the electric motor into a linear motion and transmits the linear motion to the control shaft 36. The control shaft 36 is reciprocated in the axial direction by transmission of this linear motion.

  Each intermediate drive mechanism 34 is provided between the intake cam 24 for each cylinder 12 and the upper end of the intake valve 21 (see FIG. 1). As shown in FIGS. 4 to 6, each mediation drive mechanism 34 includes an input arm 38 and a pair of output arms 39 and 40 disposed on both sides in the axial direction. The input / output arms 38 to 40 for each intermediate drive mechanism 34 are arranged between the support wall portions 26 and 26, and displacement in the axial direction is restricted by the support wall portions 26 and 26 (see FIG. 6). .

  The input arm 38 includes a cam input unit. The cam input unit includes a pair of support pieces 41, 41 provided on the outer peripheral surface of the input arm 38, and a roller 42 that is pivotally supported between the support pieces 41, 41. Then, the rotation of the intake cam 24 is transmitted (input) to the input arm 38 through the roller 42 and both support pieces 41 and 41. Further, on the outer peripheral surface of the input arm 38, an auxiliary rotation input portion 56 having a protruding shape is provided at a location different from the support pieces 41, 41 so as to be able to swing integrally with the input arm 38 (see FIG. 1). ). Further, each output arm 39, 40 includes a base circle portion 43 and a nose 44 protruding from the outer peripheral surface of the base circle portion 43. The nose 44 has a cam surface 44A that is curved in a concave shape.

  A power transmission slider 45 is arranged between the support pipe 35 and the input / output arms 38 to 40. The slider 45 is supported on the support pipe 35 so as to be rotatable and axially displaceable. In order to connect the slider 45 outside the support pipe 35 to the control shaft 36 in the support pipe 35 so that power can be transmitted, a circumferential groove 46 extending in the circumferential direction is formed on the inner wall of the slider 45. The circumferential groove 46 communicates with the outside of the slider 45 through a through hole 47 provided in the slider 45 (see FIG. 7). In the support pipe 35, a long hole 48 extending in the axial direction is formed between the adjacent support wall portions 26 and 26. A locking pin 49 inserted through the above-described through hole 47 is arranged at a location where the circumferential groove 46 and the long hole 48 intersect, and an inner end portion thereof (a lower end portion in FIGS. 6 and 7) is a control shaft 36. It is press-fitted into. Further, the bush 51 is locked to the outer end portion (the upper end portion in FIGS. 6 and 7) of the locking pin 49 located in the circumferential groove 46.

  Therefore, as described above, the support pipe 35 is fixed to the cylinder head 14 (support wall portion 26), but the locking pin 49 moves in the long hole 48 as the control shaft 36 moves in the axial direction. Thus, the slider 45 can be displaced in the axial direction via the bush 51. Further, since the slider 45 itself is engaged with the locking pin 49 and the bush 51 by the circumferential groove 46 extending in the circumferential direction, the axial position is determined by the locking pin 49 and the bush 51. However, it can rotate about the axis.

  In order to transmit power between the input arm 38 and the slider 45, a helical spline 38A that is twisted clockwise toward the output arm 39 side is formed on the inner peripheral surface of the input arm 38. Correspondingly, as shown in FIG. 5, a helical spline 45 </ b> A twisted in the same direction is formed at an intermediate portion of the outer peripheral surface of the slider 45 in the axial direction, and meshed with the helical spline 38 </ b> A described above.

  Further, in order to transmit power between the output arms 39, 40 and the slider 45, the inner peripheral surfaces of the output arms 39, 40 are opposite to the helical spline 38A of the input arm 38, that is, the input arm 38. Helical splines 39B and 40C that are twisted in the counterclockwise direction as they move away from the output arm 39 are formed. Correspondingly, helical splines 45B and 45C twisted in the same direction are formed at both ends in the axial direction of the outer peripheral surface of the slider 45, and these mesh with the helical splines 39B and 40C described above. Thus, the helical splines 38A and 45A and the helical splines 39B, 40C, 45B and 45C are twisted in the opposite directions. For this reason, the slider 45 rotates while displacing in the same direction in conjunction with the axial movement of the control shaft 36, thereby applying torsional forces in opposite directions to the input arm 38 and the output arms 39, 40. As a result, the relative phase difference between the input arm 38 and the output arms 39 and 40 changes. Further, by setting the helical direction of the helical splines (38A, 39B, 40C) and (45A, 45B, 45C), the relative phase difference between the input / output arms 38 to 40 is determined by the slider 45 in the direction indicated by the arrow X (operation angle θ). It becomes smaller as it is displaced in the direction of decreasing).

  As shown in FIG. 9, the swing of the output arms 39, 40 is transmitted to the intake valve 21 between the intake valves 21 for each cylinder 12 and the corresponding output arms 39, 40, or the transmission thereof. A transmission mechanism 50 is provided for shutting off.

  Each transmission mechanism 50 includes a rocker arm 52 having a roller 54 and a hydraulic lash adjuster 53. The rocker arm 52 is swingably disposed between the output arms 39 and 40 and the upper end portion of the intake valve 21. The lash adjuster 53 is attached to the cylinder head 14 in the vicinity of the upper end portion of the intake valve 21. The lash adjuster 53 has a structure in which the plunger in the body slides up and down by the compression reaction force and hydraulic pressure of the plunger spring. One end (right side in FIG. 9) of the rocker arm 52 is in contact with the upper end of the intake valve 21, and the other end (on the left in FIG. 9) is in contact with the plunger of the lash adjuster 53. . By these contacts, the compression reaction force of the valve spring 23 is transmitted to one end 52B of the rocker arm 52 via the intake valve 21, and the push-up force of the lash adjuster 53 is transmitted to the other end of the rocker arm 52. 52A. The rocker arm 52 is pushed up by both transmissions, and the roller 54 is in contact with the base circular portion 43 or the nose 44 of the output arms 39 and 40.

  Therefore, when the intake camshaft 25 rotates, in the mediation drive mechanism 34, the roller 42 rolls while contacting the intake cam 24, whereby the input arm 38 swings up and down with the control shaft 36 as a fulcrum. This swing is transmitted to both output arms 39 and 40 via the slider 45, and the output arms 39 and 40 swing vertically.

  At this time, the locations where the output arms 39 and 40 come into contact with the roller 54 of the rocker arm 52 (the base circular portion 43 and the nose 44) change with the downward swing. When the output arms 39 and 40 are in contact with the roller 54 at the base circle 43 (see FIG. 8), even if the output arms 39 and 40 swing, the rocker arm 52 does not swing and the intake valve 21 does not swing. Do not lift. That is, the swing of the output arms 39 and 40 is not transmitted to the intake valve 21. On the other hand, when the output arms 39 and 40 are in contact with the roller 54 at the nose 44 (see FIG. 9), the rocker arm 52 is also swung as the output arms 39 and 40 are swung, and the intake valve 21 is swung. Lifts against the valve spring 23 and opens. That is, the swing of the output arms 39 and 40 is transmitted to the intake valve 21. As the contact point of the roller 54 with the nose 44 approaches the tip of the nose 44, the intake valve 21 is lifted greatly.

  Further, when the control shaft 36 is moved in the axial direction by the actuator 37, the slider 45 is displaced in the axial direction while being rotated, and the input arm 38 and each of the swing directions of the input / output arms 38 to 40 are changed. The relative phase difference with the output arms 39 and 40 is changed. With this change, in the base circle part 43 and the nose 44, the section in contact with the roller 54 changes. In this contact section, the portion occupied by the base circle portion 43 (the portion not related to the opening of the intake valve 21) is short when the relative phase difference is large, and becomes longer as the relative phase difference becomes smaller. In the contact section, a portion occupied by the nose 44 (portion related to opening of the intake valve 21) is short when the relative phase difference is small, and becomes longer as the relative phase difference is larger. As this portion becomes longer, the operating angle θ of the intake cam 24 and the maximum lift amount of the intake valve 21 increase.

  In this way, the control shaft 36 is moved in the axial direction by the actuator 37, and the relative phase difference between the input / output arms 38 to 40 is changed by the displacement of the slider 45 accompanying the movement. As described above, the operating angle θ of the intake cam 24 and the maximum lift amount of the intake valve 21 can be continuously changed.

  In the operating angle variable mechanism 33, when the roller 54 is in contact with the nose 44, as shown in FIG. 9, the output arm 39 is placed on the nose 44 due to the compression reaction force of the valve spring 23 and the pushing force of the lash adjuster 53. , 40 acts to rotate counterclockwise in FIG. 9. In order to distinguish the rotational biasing force due to the compression reaction force of the valve spring 23 and the push-up force of the lash adjuster 53 from the rotational biasing force due to the lost motion device 55 described later, hereinafter, “rotation biasing by the valve spring 23 etc. "Power". The direction in which this rotational urging force acts is the same as the direction in which the roller 42 of the cam input unit approaches the intake cam 24. Further, the swing of the output arms 39 and 40 is transmitted to the input arm 38 through the slider 45. Therefore, the roller 42 is pressed against the intake cam 24 by the rotational urging force. On the other hand, as shown in FIG. 8, when the roller 54 is in contact with the base circle 43, the rotational urging force by the valve spring 23 or the like becomes very small. If this rotational biasing force is less than the minimum rotational biasing force required to press the roller 42 against the intake cam 24 (hereinafter referred to as a required value), the roller 42 may be separated from the intake cam 24. .

  In order to cope with this problem, a lost motion device 55 is provided in the variable valve mechanism. The lost motion device 55 includes a spring accommodating chamber 57, a loss trifter 62, and a lost motion spring 63. The spring accommodating chamber 57 is provided in the vicinity of the movable range of the auxiliary rotation input portion 56 that accompanies the swinging of the input arm 38. The loss lifter 62 is accommodated in the spring accommodating chamber 57 so as to be able to appear and retract, and is in contact with the auxiliary rotation input portion 56. The lost motion spring 63 is disposed in a compressed state in the spring accommodating chamber 57. The lost motion spring 63 urges the loss lifter 62 to protrude from the spring accommodating chamber 57, that is, in the direction opposite to the swinging direction of the input arm 38 due to the depression of the intake cam 24 (counterclockwise direction in FIG. 8). . This direction is the same as the direction in which the rotational biasing force by the above-described valve spring 23 or the like acts. Therefore, the rotation urging force by the lost motion device 55 acts on the input arm 38 in addition to the rotation urging force by the valve spring 23 and the like. When the total sum of the rotational urging forces exceeds the required value, the roller 42 is reliably pressed against the intake cam 24.

  Therefore, as described above, even when the operating angle θ is small and the rotational biasing force by the valve spring 23 or the like is less than the required value, the shortage is compensated by the rotational biasing force by the lost motion device 55. It is possible to press the roller 42 against the intake cam 24 and suppress the problem that the roller 42 is separated from the intake cam 24. In the following description, the rotation biasing force by the lost motion device 55 refers to the rotation biasing force by the lost motion spring 63.

  On the other hand, when the input / output arms 38 to 40 are swung, the contact portion between the roller 42 of the cam input portion and the intake cam 24, the contact portion between the auxiliary rotation input portion 56 and the lost motion device 55, more specifically, the loss lifter 62. Friction occurs. These frictions increase as the sum of the rotational urging forces increases. Therefore, from the viewpoint of preventing the roller 42 from separating from the intake cam 24 and minimizing the friction as much as possible, it is desirable that the total sum of both rotational urging forces is a value close to the above required value.

  As described above, the portion occupied by the base circle 43 in the contact section between the roller 54 and the output arms 39 and 40 becomes longer as the operating angle θ decreases. When the output arms 39 and 40 come into contact with the roller 54 at the base circle 43, the rotational biasing force by the valve spring 23 or the like is very small. Therefore, the phenomenon that the roller 42 is separated from the intake cam 24 becomes a problem particularly when the operating angle θ is small.

  On the other hand, if the rotational urging force by the lost motion device 55 is constant regardless of the operating angle θ, the rotational urging force by the valve spring 96 or the like and the lost motion device at the non-small operating angle as described in the background art. The sum total of the rotational urging force by 98 is larger than the required value. The roller 42 is pressed against the intake cam 24 with a force larger than necessary, and the loss trifter 62 is pressed against the auxiliary rotation input unit 56, so that the friction becomes unnecessarily large. This is because the rotational urging force by the lost motion device 55 necessary to make up for the shortage with respect to the required value is set on the basis of the small operating angle.

  Therefore, in the present embodiment, the above problem is addressed by providing means (biasing force changing means) for changing the rotational biasing force by the lost motion device 55 according to the operating angle θ of the intake cam 24. I have to.

  Specifically, a hydraulic chamber 58 is provided continuously to the spring accommodating chamber 57 on the opposite side (the upper side in FIG. 8) of the auxiliary rotation input unit 56 with the spring accommodating chamber 57 interposed therebetween. A piston 61 is slidably accommodated in the hydraulic chamber 58, and the end (upper end in FIG. 8) of the lost motion spring 63 opposite to the loss lifter 62 is in contact with the piston 61. In the hydraulic chamber 58, oil 59 is stored in a space on the side opposite to the loss trifter 62 with the piston 61 as a boundary.

  The rotational biasing force by the lost motion spring 63 changes according to the position of the piston 61 in the hydraulic chamber 58. Further, the position of the piston 61 changes according to the hydraulic pressure of the hydraulic oil in the hydraulic chamber 58. In order to supply and discharge the oil 59 to and from the hydraulic chamber 58 for the purpose of adjusting the hydraulic pressure, a supply / discharge passage 64 is connected to the hydraulic chamber 58. The supply / discharge passage 64 is connected to an oil pan 68 of the engine 11 via an oil switching valve (OSV) 65 that is an electromagnetically driven flow path switching valve, a supply passage 66 and an oil pump 69. The supply / discharge passage 64 is connected to the oil pan 68 via the OSV 65 and the discharge passage 67.

  The OSV 65 is switched by a biasing force of a coil spring and an electromagnetic solenoid that work in opposite directions to change the connection state between the supply passage 66 and the discharge passage 67 with respect to the supply / discharge passage 64. The drive control of the OSV 65 is performed by controlling energization to the electromagnetic solenoid through the electronic control unit 71.

  The OSV 65 causes the supply / discharge passage 64 and the discharge passage 67 to communicate with each other when the electromagnetic solenoid is demagnetized. In this case, part of the oil 59 in the hydraulic chamber 58 is returned to the oil pan 68 through the supply / discharge passage 64, the OSV 65, and the discharge passage 67. As a result, the hydraulic pressure in the hydraulic chamber 58 decreases, and the piston 61 moves away from the spring accommodating chamber 57. The lost motion spring 63 extends to reduce the urging force against the auxiliary rotation input unit 56, that is, the rotation urging force by the lost motion device 55. On the contrary, when the electromagnetic solenoid is excited, the supply / discharge passage 64 and the supply passage 66 are communicated with each other. In this case, the oil 59 in the oil pan 68 is sent out to the hydraulic chamber 58 by the oil pump 69. As a result, the hydraulic pressure in the hydraulic chamber 58 rises and the piston 61 approaches the spring accommodating chamber 57. The lost motion spring 63 is contracted, and the rotational urging force by the lost motion device 55 is increased.

  In order to control the energization mode (excitation / demagnetization) of the electromagnetic solenoid, the engine 11 is provided with a stroke sensor 72 in addition to the electronic control unit 71. The stroke sensor 72 detects the amount of movement of the control shaft 36 from the reference position in the operating angle variable mechanism 33. As described above, the slider 45 is displaced while rotating as the control shaft 36 moves, and the input / output arms 38 to 40 are relatively rotated to change the operating angle θ. Therefore, the operating angle θ of the intake cam 24 can be calculated based on the amount of movement of the control shaft 36 from the reference position.

  From this, the electronic control unit 71 calculates the operating angle θ of the intake cam 24 corresponding to the movement amount based on the movement amount detected by the stroke sensor 72. Then, the electronic control unit 71 excites or demagnetizes the electromagnetic solenoid of the OSV 65 based on the operating angle θ. For example, as shown in FIG. 12, the electronic control unit 71 excites the electromagnetic solenoid when the operating angle θ is equal to or smaller than a predetermined value θ1. The predetermined value θ1 is an intermediate value within a range that the working angle θ can take. Further, the electronic control device 71 demagnetizes the electromagnetic solenoid when the operating angle θ is larger than the predetermined value θ1. In this way, the electronic control unit 71 performs a process of changing the rotation biasing force by the lost motion device 55 according to the operating angle θ (biasing force changing process).

Next, the operation and effect of the variable valve mechanism of the first embodiment configured as described above will be described.
8 and 9 show the state of the mediation drive mechanism 34 when the control shaft 36 is largely moved in the direction of the arrow X in FIG. At this time, the relative phase difference between the input arm 38 and the output arms 39 and 40 is small, and the operating angle θ of the intake cam 24 is smaller than the predetermined value θ1.

  In particular, FIG. 8 shows a state in which the intake cam 24 is in contact with the roller 42 of the cam input portion in the base circle portion 24A. Both output arms 39, 40 are in contact with the roller 54 of the rocker arm 52 at a portion of the base circle 43 that is relatively distant from the nose 44. Thus, in a state where the roller 54 is in contact with the base circle portion 43, the intake valve 21 is not lifted and is closed.

  When the intake camshaft 25 rotates, the roller 42 is pushed down by the nose 24B of the intake cam 24, and the input arm 38 swings downward. This swing is transmitted to the output arms 39 and 40 via the slider 45, and the output arms 39 and 40 swing downward. Even if the output arms 39 and 40 swing, the roller 54 continues to contact the base circle 43 without contacting the cam surface 44A of the nose 44 for a while. Therefore, the intake valve 21 does not lift and keeps closing.

  As shown in FIG. 9, when the intake camshaft 25 further rotates and the input / output arms 38 to 40 further swing, the contact position of the output arms 39 and 40 with the roller 54 is changed from the base circle 43 to the nose 44. Move on. The roller 54 is pushed down by the nose 44, and the rocker arm 52 swings downward with the end 52A as a fulcrum. With this swing, the intake valve 21 is lifted by the end 52B of the rocker arm 52, and the intake valve 21 is opened.

  The rocking angle of the rocker arm 52 increases as the location of the cam surface 44A of the nose 44 in contact with the roller 54 moves from the root of the nose 44 to the tip. However, since the portion occupied by the cam surface 44A is short in the contact section of the output arms 39, 40 with the roller 54, the rocker arm 52 does not swing so much. Therefore, the intake valve 21 opens the intake port 18 with a small operating angle θ. As the intake valve 21 opens, the amount of air flowing from the intake port 18 into the combustion chamber 17 is small.

  In the above situation, since the operating angle θ is smaller than the predetermined value θ1, the electronic control unit 71 excites the electromagnetic solenoid of the OSV 65. By this excitation, oil 59 is supplied into the hydraulic chamber 58, and the hydraulic pressure in the hydraulic chamber 58 increases. The piston 15 is moved to a position close to the spring accommodating chamber 57 in the movable range. The lost motion spring 63 is compressed, and the rotational biasing force against the auxiliary rotation input unit 56 is increased. In response to this increased rotational biasing force, the input arm 38 is biased in the direction opposite to the swinging direction of the input arm 38 due to the depression of the intake cam 24 (counterclockwise direction in FIG. 8).

  Accordingly, when the operating angle θ is small, the portion occupied by the base circle 43 in the contact section of the output arms 39, 40 with the roller 54 is long, and the rotational urging force by the valve spring 23 or the like becomes very small and the above required value ( The minimum rotational biasing force necessary to press the roller 42 against the intake cam 24 is not satisfied. However, the deficiency with respect to the required value of the rotational urging force by the valve spring 23 or the like is compensated by the rotational urging force by the lost motion device 55, and the sum of both rotational urging forces becomes a value close to the required value. Therefore, the roller 42 of the cam input portion is pressed against the intake cam 24 with an appropriate strength so as not to be separated from the intake cam 24, and the contact portion between the both 42 and 24, the contact between the auxiliary rotation input portion 56 and the loss trifter 62. The friction generated in the part is reduced.

  By the way, when the control shaft 36 is moved in the direction indicated by the arrow Y in FIG. 4 by the actuator 37 from the above state, the slider 45 is displaced in the same direction while rotating in conjunction therewith. As the slider 45 rotates, torsional forces in opposite directions are applied to the input arm 38 and the output arms 39, 40, and the relative relationship between the input arm 38 and the output arms 39, 40 is shown in FIGS. The phase difference increases. This relative phase difference increases as the displacement amount of the slider 45 in the arrow Y direction increases.

  As shown in FIG. 10, when the base circle portion 24A of the intake cam 24 contacts the roller 42 of the cam input portion, the base circle portion 43 of the output arms 39, 40 contacts the roller 54 of the rocker arm 52. Approaches nose 44. For this reason, when the output arms 39, 40 swing, the contact point of the output arms 39, 40 with the roller 54 moves from the base circle 43 to the cam surface 44A of the nose 44 from a relatively early time. The portion occupied by the cam surface 44A becomes longer in the contact section of the output arms 39, 40 with the roller 54. Therefore, as the output arms 39 and 40 swing, the cam surface 44A immediately contacts the roller 54, and the roller 54 is pushed down using substantially the entire range of the cam surface 44A as shown in FIG. By this depression, the rocker arm 52 swings downward with the end 52A as a fulcrum, the end 52B of the rocker arm 52 lifts the intake valve 21 greatly, and opens the intake valve 21 greatly. Both the operating angle θ and the maximum lift amount increase, and the amount of air flowing from the intake port 18 into the combustion chamber 17 increases.

  As described above, when the operating angle θ is large, the portion occupied by the nose 44 is long in the contact section between the input arm 38 and the roller 54. When the roller 54 is in contact with the nose 44, a rotational biasing force by the valve spring 23 or the like acts.

  Under this situation, when the auxiliary rotation input unit 56 is biased by the lost motion device 55 with a large rotational biasing force, for example, with the same rotational biasing force as that at the small working angle described above, the rotational biasing force and the valve spring The sum of the rotational urging force by 23 and the like is larger than the required value. As a result, the friction generated at the contact portion between the roller 42 and the intake cam 24 and the friction generated at the contact portion between the auxiliary rotation input portion 56 and the loss trifter 62 increase.

  However, as described above, when the operating angle θ is larger than the predetermined value θ1, the electronic control unit 71 demagnetizes the electromagnetic solenoid of the OSV 65. Due to this demagnetization, the oil 59 is discharged from the hydraulic chamber 58, the hydraulic pressure in the hydraulic chamber 58 is reduced, and the piston 15 is moved to the place farthest from the spring accommodating chamber 57 in the movable range. The lost motion spring 63 is extended to reduce the rotational biasing force on the auxiliary rotation input unit 56. The sum of both rotational urging forces by the valve spring 23 and the like and the lost motion device 55 is close to the required value. Therefore, as in the case where the operating angle θ is equal to or less than the predetermined value θ1, the roller 42 of the cam input portion is pressed against the intake cam 24 with an appropriate strength. As a result, the friction generated at the contact portion between the roller 42 and the intake cam 24 and at the contact portion between the auxiliary rotation input portion 56 and the loss lifter 62 is reduced.

According to the embodiment described in detail above, the following effects can be obtained.
(1) When the operating angle θ of the intake cam 24 is equal to or smaller than the predetermined value θ1, the rotational urging force by the lost motion device 55 is increased by exciting the electromagnetic solenoid of the OSV 65. Therefore, under the above situation with respect to the operating angle θ, the rotational urging force by the valve spring 23 or the like becomes small and does not satisfy the required value. However, the shortage with respect to the required value is compensated by the increase in the rotational urging force, and the valve spring 23 It is possible to make both rotational urging forces by the equal and lost motion device 55 close to a required value.

  (2) When the operating angle θ of the intake cam 24 is larger than the predetermined value θ1, the rotational urging force by the lost motion device 55 is reduced by demagnetizing the electromagnetic solenoid of the OSV 65. Therefore, under the above-described situation with respect to the operating angle θ, the rotational urging force by the valve spring 23 or the like increases, but the total of both rotational urging forces can be made close to the required value due to the decrease in the rotational urging force. .

  (3) As in the above (1) and (2), by changing the rotational biasing force by the lost motion device 55 according to the operating angle θ of the intake cam 24, whether the operating angle θ is large or small, The total sum of the two biasing forces can be set to a value close to the required value. Therefore, regardless of the magnitude of the operating angle θ of the intake cam 24, the roller 42 of the cam input portion can be pressed against the intake cam 24 so as not to be separated from the intake cam 24. Further, the friction can be reduced as compared with the case where the rotational biasing force by the lost motion device 55 is constant.

(Second Embodiment)
Next, a second embodiment embodying the present invention will be described.
In the second embodiment, as the biasing force changing process performed by the electronic control unit 71, the energization mode (demagnetization / excitation) of the electromagnetic solenoid of the OSV 65 is switched according to the rotation speed of the intake cam 24 instead of the operating angle θ. The rotation urging force by the lost motion device 55 is changed. In this respect, the second embodiment is different from the first embodiment.

  Here, the intake camshaft 25 is drivingly connected to the crankshaft 16 by a timing chain, a sprocket or the like as described above, and rotates in conjunction with the crankshaft 16. The rotational speed of the intake camshaft 25 and the rotational speed of the crankshaft 16 (engine rotational speed NE) are in a corresponding relationship. On the other hand, as indicated by a two-dot chain line in FIG. 1, the engine 11 is pulsed every time the crankshaft 16 rotates by a certain angle in order to detect the rotation angle (crank angle) of the crankshaft 16 and the engine rotation speed. A crank angle sensor 73 for generating the above signal is originally provided. Therefore, here, the signal of the existing crank angle sensor 73 described above is used, and the engine rotational speed NE calculated based on the signal is used as the value corresponding to the rotational speed of the intake camshaft 25.

  The electronic control unit 71 excites or demagnetizes the electromagnetic solenoid of the OSV 65 based on the engine speed NE. For example, as shown in FIG. 13, the electronic control unit 71 excites the electromagnetic solenoid when the engine rotational speed NE is higher than a predetermined value NE1. The predetermined value NE1 is an intermediate value within a range that the engine speed NE can take. Further, the electronic control device 71 demagnetizes the electromagnetic solenoid when the engine rotational speed NE is equal to or less than the predetermined value NE1. By changing the energization mode for the electromagnetic solenoid, the rotational urging force by the lost motion device 55 is made smaller in the region where the rotational speed of the intake cam 24 is low than in the region where the intake cam 24 is low. The reason for this is as follows.

  In the working angle variable mechanism 33, an inertial force is generated as the input / output arms 38 to 40 swing. When the roller 42 of the cam input portion starts to rise from the lowering by the intake cam 24, the roller 42 tends to continue to lower due to the inertia force. The roller 42 tends to move away from the intake cam 24, and the pressing force of the roller 42 against the intake cam 24 is weakened. This inertial force is small when the rotational speed of the intake cam 24 (intake camshaft 25) is low, but increases as the rotational speed increases. Therefore, when the intake cam 24 is at a high rotational speed, the degree to which the pressing force of the roller 42 against the intake cam 24 is weakened becomes large. Therefore, the phenomenon that the roller 42 is separated from the intake cam 24 becomes a problem particularly when the rotational speed of the intake cam 24 is high.

  Even in such a situation, if the total rotational urging force is set to a value close to the required value (the minimum value of the rotational urging force necessary for pressing the roller 42 against the intake cam 24), the rotational urging force by the lost motion device 55 is obtained. Is constant, the rotational urging force is set based on a region where the rotational speed of the intake cam 24 is high. However, in a region other than the above, for example, a region where the rotational speed is low, the total rotational biasing force is greater than the required value. As a result, the roller 42 is pressed against the intake cam 24 with a force greater than necessary, and the loss lifter 62 is pressed against the auxiliary rotation input unit 56. Therefore, as described above, the rotational urging force by the lost motion device 55 is changed according to the rotational speed of the intake cam 24.

  According to the second embodiment, when the engine speed NE is higher than the predetermined value NE1, the electronic control device 71 excites the electromagnetic solenoid of the OSV 65. By this excitation, the oil 59 is supplied to the hydraulic chamber 58, the hydraulic pressure in the hydraulic chamber 58 rises, and the piston 15 is moved to a location closest to the spring accommodating chamber 57 in the movable range. The lost motion spring 63 is compressed, and the rotational biasing force against the auxiliary rotation input unit 56 is increased.

  Therefore, when the engine speed NE is high, the inertial force accompanying the swinging of the input / output arms 38 to 40 increases, and the degree of weakening the pressing force of the roller 42 against the intake cam 24 increases. However, as the rotational urging force by the lost motion device 55 increases, the sum of both rotational urging forces by the valve spring 23 and the lost motion device 55 becomes a value close to the required value. Therefore, the roller 42 of the cam input portion is pressed against the intake cam 24 with an appropriate strength so as not to be separated from the intake cam 24, and the contact portion between the both 42 and 24, the contact between the auxiliary rotation input portion 56 and the loss trifter 62. The friction generated in the part is reduced.

  When the engine speed NE is equal to or lower than the predetermined value NE1, the electronic control unit 71 demagnetizes the electromagnetic solenoid of the OSV 65. Due to this demagnetization, the oil 59 is discharged from the hydraulic chamber 58, the hydraulic pressure in the hydraulic chamber 58 is reduced, and the piston 15 is moved to the place farthest from the spring accommodating chamber 57 in the movable range. The lost motion spring 63 is extended to reduce the rotational biasing force against the auxiliary rotation input unit 56.

  Therefore, when the engine speed NE is low, the inertial force accompanying the swinging of the input / output arms 38 to 40 is reduced, and the degree of weakening the pressing force of the roller 42 against the intake cam 24 is reduced. However, due to the decrease in the rotational urging force by the lost motion device 55, the sum of both the rotational urging forces by the valve spring 23 and the lost motion device 55 becomes a value close to the required value. Therefore, similarly to the case where the engine rotational speed NE is higher than the predetermined value NE1, the roller 42 of the cam input portion is pressed against the intake cam 24 with an appropriate strength. As a result, the friction generated at the contact portion between the roller 42 and the intake cam 24 and at the contact portion between the auxiliary rotation input portion 56 and the loss lifter 62 is reduced.

Therefore, according to the second embodiment, the following effects can be obtained.
(4) When the engine rotational speed NE is higher than the predetermined value NE1, the rotational urging force by the lost motion device 55 is increased by exciting the electromagnetic solenoid of the OSV 65. Therefore, under the above-described situation with respect to the engine rotational speed NE, the inertial force accompanying the swinging of the input / output arms 38 to 40 increases, and the degree to which the pressing force of the roller 42 against the intake cam 24 is weakened increases. By increasing the urging force, the sum of the rotational urging forces by the valve spring 23 and the like and the lost motion device 55 can be made close to the required value.

  (5) When the engine rotational speed NE is equal to or lower than the predetermined value NE1, the rotational urging force by the lost motion device 55 is reduced by demagnetizing the electromagnetic solenoid of the OSV 65. Therefore, under the above-described situation with respect to the engine rotational speed NE, the inertial force accompanying the swinging of the input / output arms 38 to 40 is reduced, and the degree of weakening the pressing force of the roller 42 against the intake cam 24 is reduced. By reducing the urging force, the total rotational urging force by the valve spring 23 and the lost motion device 55 can be made close to the required value.

  (6) As in (4) and (5) above, by changing the rotational biasing force by the lost motion device 55 according to the engine rotational speed NE (rotational speed of the intake cam 24), even in a high rotational speed region. Even in a low region, the total sum of both rotational urging forces can be made close to the required value. Therefore, regardless of the rotational speed of the intake cam 24, the roller 42 of the cam input portion can be pressed against the intake cam 24 so as not to leave the intake cam 24. Further, the friction can be reduced as compared with the case where the rotational biasing force by the lost motion device 55 is constant.

(Third embodiment)
Next, a third embodiment embodying the present invention will be described.
In the third embodiment, as an urging force change process performed by the electronic control unit 71, an energization mode (demagnetization / excitation) to the electromagnetic solenoid of the OSV 65 based on the operating angle θ and the rotational speed (engine rotational speed NE) of the intake cam 24. Is changed so that the rotation urging force by the lost motion device 55 is changed. In this respect, the third embodiment is different from the first and second embodiments.

  For example, as shown in FIG. 14, the electronic control unit 71 has an operating angle θ that is less than or equal to a predetermined value θ2 and an engine rotational speed NE that is less than the predetermined value NE2 in a region defined by the operating angle θ and the engine rotational speed NE. If it is in the higher region Z2, the electromagnetic solenoid is excited. When the operating angle θ and the engine rotational speed NE are in a region (region Z1) other than the region Z2, that is, when the operating angle θ is in a region greater than the predetermined value θ2, and the engine rotational speed NE is equal to or less than the predetermined value NE2. If it is in the region, the electromagnetic solenoid is demagnetized. This region Z2 includes a region where the operating angle θ is larger than the predetermined value θ2 and the engine speed NE is equal to or less than the predetermined value NE2.

  The predetermined value θ2 is an intermediate value within the range that the working angle θ can take, and may be the same value as the predetermined value θ1 in the first embodiment, or may be a different value. Similarly, the predetermined value NE2 is an intermediate value within the range that the engine speed NE can take, and may be the same value as the predetermined value NE1 in the second embodiment or a different value. The reason why the rotational urging force by the lost motion device 55 is changed as described above is as follows.

  In the operating angle variable mechanism 33, as described above, the rotational urging force of the valve spring 23 or the like acts on the input arm 38. The rotational urging force decreases as the operating angle θ decreases, and the roller 42 acts on the intake cam 24. The pressing force decreases. In the working angle variable mechanism 33, the inertial force generated as the input / output arms 38 to 40 swing is small when the rotational speed of the intake cam 24 is low, but increases as the rotational speed increases. The higher the rotational speed of the intake cam 24, the greater the extent to which the pressing force of the roller 42 against the intake cam 24 is weakened. Therefore, if the intake cam 24 rotates at a high speed when the operating angle θ is small, the originally small pressing force is further weakened by the large inertia force. As a result, the pressing force becomes very small.

  Even in such a situation, if the sum of the rotational urging forces of the valve spring 23 and the like and the lost motion device 55 is set to a value close to the required value, the rotational urging force of the lost motion device 55 is assumed to be constant. Is set based on a region (region Z2) in which the operating angle θ is small and the rotational speed of the intake cam 24 is high. The required value is the minimum value of the rotational urging force necessary to press the roller 42 against the intake cam 24, as in the first and second embodiments. However, in a region other than the above (region Z1), the total rotational biasing force is larger than the required value. As a result, the roller 42 is pressed against the intake cam 24 with a force greater than necessary, and the loss lifter 62 is pressed against the auxiliary rotation input unit 56. Therefore, as described above, the rotational urging force by the lost motion device 55 is changed according to the operating angle θ and the rotational speed of the intake cam 24.

  According to the third embodiment, when the operating angle θ and the engine rotational speed NE belong to the region Z2, the electronic control unit 71 excites the electromagnetic solenoid of the OSV 65. By this excitation, the oil 59 is supplied to the hydraulic chamber 58, the hydraulic pressure in the hydraulic chamber 58 rises, and the piston 15 is moved to a location closest to the spring accommodating chamber 57 in the movable range. The lost motion spring 63 is compressed, and the rotational biasing force against the auxiliary rotation input unit 56 is increased. With this rotational biasing force, the input arm 38 is biased in the direction opposite to the swinging direction of the input arm 38 due to the depression of the intake cam 24.

  Therefore, in the region Z2, as described above, the pressing force of the roller 42 against the intake cam 24 becomes very small. However, the increase of the rotational biasing force by the lost motion device 55 compensates for the shortage of the rotational biasing force with respect to the required value, and the sum of both rotational biasing forces by the valve spring 23 and the lost motion device 55 becomes the required value. Close value. Therefore, the roller 42 of the cam input portion is pressed against the intake cam 24 with such a strength that it does not separate from the intake cam 24, and at the contact portion between the both 42, 24 and the contact portion between the auxiliary rotation input portion 56 and the loss trifter 62. The generated friction is reduced.

  On the other hand, when the operating angle θ and the engine rotational speed NE belong to the region Z1, the electronic control unit 71 demagnetizes the electromagnetic solenoid of the OSV 65. Due to this demagnetization, the oil 59 is discharged from the hydraulic chamber 58, the hydraulic pressure in the hydraulic chamber 58 is reduced, and the piston 15 is moved to the place farthest from the spring accommodating chamber 57 in the movable range. The lost motion spring 63 is extended to reduce the rotational biasing force against the auxiliary rotation input unit 56.

  Therefore, in the region Z1, the pressing force of the roller 42 against the intake cam 24 is not as small as that in the region Z2. However, due to the decrease in the rotational urging force by the lost motion device 55, the sum of both the rotational urging forces by the valve spring 23 and the lost motion device 55 becomes a value close to the required value. Therefore, in the area Z1, as in the area Z2, the roller 42 of the cam input portion is pressed against the intake cam 24 with an appropriate strength. As a result, the friction generated at the contact portion between the roller 42 and the intake cam 24 and at the contact portion between the auxiliary rotation input portion 56 and the loss lifter 62 is reduced.

According to the third embodiment, the following effects can be obtained.
(7) When the operating angle θ and the engine rotational speed NE belong to the region Z2, the rotational urging force by the lost motion device 55 is increased by exciting the electromagnetic solenoid of the OSV 65. For this reason, in the region Z2, the pressing force of the roller 42 against the intake cam 24 becomes very small. However, due to the increase of the rotational urging force, the sum of the rotational urging forces of the valve spring 23 and the lost motion device 55 becomes the required value. It can be close.

  (8) When the operating angle θ and the engine rotational speed NE belong to the region Z1, the rotational urging force of the lost motion device 55 is reduced by demagnetizing the electromagnetic solenoid of the OSV 65. Therefore, in the region Z1, the pressing force of the roller 42 against the intake cam 24 is larger than that in the region Z2. However, due to the decrease in the rotational urging force, the sum of the rotational urging forces by the valve spring 23 and the lost motion device 55 is required. The value can be close to the value.

  (9) As in (7) and (8) above, the rotational biasing force by the lost motion device 55 is changed according to the operating angle θ and the rotational speed of the intake cam 24, so that the rotation is applied in both the region Z1 and the region Z2. The total sum of power can be made close to the required value. Therefore, regardless of the magnitude of the operating angle θ of the intake cam 24 and the rotational speed of the intake cam 24, the roller 42 of the cam input portion may be pressed against the intake cam 24 so as not to leave the intake cam 24. it can. Further, the friction can be reduced as compared with the case where the rotational biasing force by the lost motion device 55 is constant.

Note that the present invention can be embodied in another embodiment described below.
In the first embodiment, three or more rotational urging forces by the lost motion device 55 may be set, and these rotational urging forces may be switched according to the operating angle θ of the intake cam 24. In this case, in the region defined by the operating angle θ, the rotational biasing force by the lost motion device 55 is made smaller in the region where the operating angle θ is large than in the small region.

In addition, as indicated by a two-dot chain line in FIG. 12, the setting may be made such that the rotational urging force by the lost motion device 55 decreases as the operating angle θ increases.
In the second embodiment, three or more rotational urging forces by the lost motion device 55 may be set, and these rotational urging forces may be switched according to the engine rotational speed NE. In this case, in the region defined by the engine rotational speed NE, the rotational urging force by the lost motion device 55 is made smaller in the region where the engine rotational speed NE is low than in the region where the engine rotational speed NE is high.

Further, as indicated by a two-dot chain line in FIG. 13, the setting may be made such that the rotational urging force by the lost motion device 55 becomes smaller as the engine rotational speed NE becomes lower.
In FIG. 14, the region Z <b> 1 in which the rotational urging force by the lost motion device 55 is reduced may be set to a region different from the third embodiment. However, in this setting, at least a region where the operating angle θ is large and the engine rotational speed NE is low (for example, a region indicated by a two-dot chain line in FIG. 14) is included in the region Z1.

  In the second and third embodiments, the rotational urging force by the lost motion device 55 is changed based on the rotational speed of the intake / exhaust cam shafts 25, 28 or the intake / exhaust cams 24, 27 instead of the engine rotational speed NE. You may make it do.

The auxiliary rotation input unit 56 may be provided in the output arms 39 and 40 instead of the input arm 38.
The cam input unit may be any unit that can transmit the rotation of the intake cam 24 to the input arm 38. Therefore, the form of the cam input portion is not limited to the one composed of the support piece 41 and the roller 42, and can be appropriately changed within a range that satisfies the above conditions.

In the operating angle variable mechanism 33, the control shaft 36 may be displaced in the axial direction using an actuator 37 of a type different from that of the electric motor.
A working angle variable mechanism 33 may be provided between the exhaust camshaft 28 and the exhaust valve 22, and the working angle of the exhaust cam 27 may be variable instead of or in addition to the intake cam 24.

-You may change suitably the structure of the working angle variable mechanism 33 in the said embodiment.
For example, the support pipe 35 may be omitted, and the control shaft 36 may also function as the support pipe 35. Further, the helical angles of the helical splines 39B and 45B and the helical splines 40C and 45C may be the same or different.

  The present invention is not limited to an internal combustion engine, and can be widely applied to those having a variable valve mechanism having a variable operating angle mechanism and a lost motion device.

1 is a partial cross-sectional view of an engine to which a variable valve mechanism is applied according to a first embodiment that embodies the present invention. The characteristic view which shows the change aspect of the valve timing by a valve timing variable mechanism in the relationship between a crank angle and a lift amount. The characteristic view which shows the change aspect of the working angle and the maximum lift amount by a working angle variable mechanism. The perspective view which shows a mediation drive 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. The fragmentary sectional view which shows a variable valve mechanism when an operating angle is made small. The fragmentary sectional view which shows a variable valve mechanism when an input / output arm is rock | fluctuated from the state of FIG. The fragmentary sectional view which shows a variable valve mechanism when an operating angle is enlarged. The fragmentary sectional view which shows a variable valve mechanism when an input / output arm is rock | fluctuated from the state of FIG. The characteristic view explaining the relationship between a working angle and the rotation urging | biasing force by a lost motion apparatus. The characteristic view explaining the relationship between an engine rotational speed and the rotational urging | biasing force by a lost motion apparatus about 2nd Embodiment of this invention. The characteristic view explaining the relationship between engine rotation speed, a working angle, and the rotation urging | biasing force by a lost motion apparatus about 3rd Embodiment of this invention. The fragmentary perspective view which abbreviate | omits and shows the upper half part of an input / output arm about the variable valve mechanism in background art. The fragmentary sectional view which shows schematic structure of the variable valve mechanism in background art.

Explanation of symbols

  21 ... Intake valve, 23 ... Valve spring, 24 ... Intake cam, 33 ... Working angle variable mechanism, 38 ... Input arm, 38A, 39B, 40C, 45A, 45B, 45C ... Helical spline, 39, 40 ... Output arm, 41 ... support piece (constituting part of cam input part), 42 ... roller (constituting part of cam input part), 43 ... base circle part, 44 ... nose, 45 ... slider, 50 ... transmission mechanism, 55 ... lost Motion device, θ ... working angle, Z1, Z2 ... area.

Claims (5)

The rotation of the cam is transmitted to the input arm through the cam input section to swing the input arm, and the valve is opened against the valve spring by the output arm that swings in conjunction with the input arm. A working angle variable mechanism for changing a working angle of the cam related to the valve opening together with a maximum lift amount of the valve by changing a relative phase difference in the swing direction of the input arm and the output arm;
A variable valve mechanism comprising a lost motion device that urges the input arm to rotate in the same direction as the direction in which the rotation urging force acts by the valve spring to press the cam input portion against the cam.
A variable valve operating system characterized in that an urging force changing means for reducing a rotational urging force by the lost motion device is provided in a region defined by the cam operating angle in a region having a large operating angle than in a small region. mechanism. The rotation of the cam is transmitted to the input arm through the cam input section to swing the input arm, and the valve is opened against the valve spring by the output arm that swings in conjunction with the input arm. A working angle variable mechanism for changing a working angle of the cam related to the valve opening together with a maximum lift amount of the valve by changing a relative phase difference in the swing direction of the input arm and the output arm;
A variable valve mechanism comprising a lost motion device that urges the input arm to rotate in the same direction as the direction in which the rotation urging force acts by the valve spring to press the cam input portion against the cam.
A variable valve operating system comprising an urging force changing means for reducing a rotational urging force by the lost motion device in a region defined by the rotational speed of the cam in a region where the rotational speed is low compared to a region where the rotational speed is low. mechanism. The rotation of the cam is transmitted to the input arm through the cam input section to swing the input arm, and the valve is opened against the valve spring by the output arm that swings in conjunction with the input arm. A working angle variable mechanism for changing a working angle of the cam related to the valve opening together with a maximum lift amount of the valve by changing a relative phase difference in the swing direction of the input arm and the output arm;
A variable valve mechanism comprising a lost motion device that urges the input arm to rotate in the same direction as the direction in which the rotation urging force acts by the valve spring to press the cam input portion against the cam.
Regarding the region defined by the working angle and the rotational speed of the cam, at least in the region where the working angle is large and the rotational speed is low, the lost motion device is smaller than the region where the working angle is small and the rotational speed is high. A variable valve mechanism comprising a biasing force changing means for reducing the rotational biasing force due to. The operating angle variable mechanism includes a slider provided between the cam and the valve so as to be rotatable and axially displaceable, and meshed with the input arm and the output arm by helical splines, respectively. ,
2. The relative phase difference between the input arm and the output arm is changed by the rotation accompanying the displacement of the slider in the axial direction, and the working angle of the cam is changed together with the maximum lift amount of the valve. The variable valve mechanism as described in any one of -3. The output arm includes a base circle and a nose protruding from the outer peripheral surface of the base circle,
Between the output arm and the valve, the swing of the output arm is not transmitted to the valve when contacting the base circle, and the swing of the output arm is not transmitted to the valve when contacting the nose. The variable valve mechanism according to any one of claims 1 to 4, wherein a transmission mechanism for transmission is provided.

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