JP2021025498A - Valve gear of internal combustion engine - Google Patents

Abstract

To provide a valve gear of an internal combustion engine having a plurality of cam lobs having different cam shapes in which smooth and accurate switching of cam lobes can be achieved.SOLUTION: A valve gear (1) of an internal combustion engine includes a cam (20) provided with a plurality of cam lobes (21, 22)of different cam shapes arranged in an axial direction of a cam shaft (17), and being integral with the cam shaft in a rotating direction and movable in an axial direction, and switch means (23, 30) for axially moving the cam relative to the cam shaft, and opens and closes a valve (10) connected to a driven portion (16b) kept into contact with the cam lobs, by rotation of the cam. In the cam, the shapes of the adjacent cam lobes are substantially the same as each other in a prescribed phase range (Q1) at a valve lift start side including a valve lift start point (Lx), in a valve lift region (EL) for opening and closing the valve, and a terminal point (T2) of the axial movement of the cam by the switch means, is determined within the prescribed phase range.SELECTED DRAWING: Figure 4

Description

The present invention relates to a valve gear of an internal combustion engine.

A valve gear provided in an internal combustion engine such as a vehicle engine has a cam for opening and closing an intake valve and an exhaust valve (hereinafter referred to as a valve). In recent years, in order to improve the performance of an internal combustion engine, a variable valve mechanism that changes the valve lift amount and opening / closing timing by a cam has been widely used.

It is known that a variable valve mechanism has a structure in which a plurality of camlobs having different cam shapes are provided on a camshaft, and these camlobs are moved in the axial direction of the camshaft to switch camlobs used for driving a valve. ..

For example, in the variable valve lift mechanism of Patent Document 1, a concave groove-shaped stroke curve is formed on the peripheral surface of a cam having a plurality of cam trajectories having different shapes, and the cam is supported so as to be movable in the axial direction of the cam shaft. There is. An operation member having an operation pin extending in the radial direction of the cam shaft is provided, and the protrusion amount of the operation pin can be changed to engage or disengage from the stroke curve.

The stroke curve in the variable valve lift mechanism of Patent Document 1 includes a region inclined with respect to the rotation direction of the cam. When the operating pin is not engaged in the stroke curve, the cam is held in place on the camshaft and the selected cam trajectory is brought into contact with the rollers of the rocker arm to operate the valve. When the operation pin is projected and engaged with the stroke curve, the operation pin presses the stroke curve in response to the rotation of the cam, and the cam moves in the axial direction based on the shape of the stroke curve. As a result, the cam trajectory that comes into contact with the roller of the rocker arm is switched. It is equipped with a plurality of stroke curves having different inclination directions with respect to the rotation direction of the cam and a plurality of operation pins corresponding to the curves, and the cam can be moved in the forward and reverse directions in the axial direction.

Japanese Patent No. 3980699

In the variable valve lift mechanism of Patent Document 1, it is necessary to consider the possibility that the cam vibrates when the cam shaft rotates at high speed, which increases the load on the operation pin and the stroke curve. In order to realize stable switching operation of the cam trajectory, measures such as suppressing the engine speed to reduce the rotation speed of the camshaft and increasing the size of the operation pin to increase the strength are assumed.

However, fluctuating the engine speed for switching the cam trajectory affects the complexity of engine control and the stability of engine output. In addition, increasing the size of the operation pin leads to an increase in the size of the cam and its peripheral structure, which hinders the increase in engine speed.

In the variable valve lift mechanism of Patent Document 1, adjacent cam trajectories have the same shape in the base circle region (circular portion having the smallest diameter that does not cause balf lift), and the cam trajectories are in a state where the roller of the rocker arm is in contact with the base circle region. To switch. However, since only the base circle region that closes the balkh is used, it is necessary to rapidly move the cam in the axial direction at a limited rotation angle of the cam in order to obtain a predetermined amount of axial movement. Then, the acceleration when the cam moves becomes large, and it is difficult to perform a smooth and highly accurate switching operation.

The present invention has been made in view of the above points, and an object of the present invention is to realize smooth and highly accurate cam lob switching in a valve gear of an internal combustion engine having a plurality of cam lobs having different cam shapes.

In the present invention, a plurality of cam lobs, each having a different cam shape, are provided side by side in the axial direction of the cam shaft, and a cam that can move in the axial direction integrally with the cam shaft in the rotational direction and the cam as a cam shaft. A valve gear of an internal combustion engine that includes a switching means for moving in the axial direction and opens and closes a valve connected to a driven portion that abuts on the cam lob by rotating the cam. The cam opens and closes the valve. In the valve lift region to be operated, the shapes of adjacent camlobs are substantially matched in a predetermined phase range on the valve lift start side including the valve lift start point, and within this predetermined phase range, the axial direction of the cam by the switching means. The feature is that the end point of the movement is set.

In the valve gear of an internal combustion engine as described above, the cams are adjacent to each other in a predetermined phase range on the valve lift end side including the valve lift end point in the valve lift region for opening and closing the valve. It is characterized in that the shapes of the cam lobs are substantially matched, and the starting point of the axial movement of the cam by the switching means is set within this predetermined phase range.

According to the present invention, in a valve gear of an internal combustion engine having a plurality of cam lobs having different cam shapes, a part of the phase range on the start side and the end side of the valve lift region of the cam is used for the axial movement of the cam. Therefore, smooth and highly accurate cam lob switching can be realized.

It is a perspective view of the valve gear of this embodiment. It is a side view of the valve gear which made a part view in cross section. It is the figure which developed the switching guide part of a cam in a plane. It is a graph which shows the relationship between the valve operation and the cam lob switching operation by the valve gear of this embodiment. It is a graph which shows the relationship between the valve operation by the valve operation device of the modified example, and the cam lob switching operation.

Hereinafter, the present embodiment will be described with reference to the accompanying drawings. The valve gear 1 shown in FIG. 1 is built in an internal combustion engine such as a vehicle engine. Since the overall structure of the internal combustion engine is well known, it will be briefly described by omitting the illustration.

In an internal combustion engine equipped with a valve gear 1, a piston is slidably arranged in a cylinder, and the piston is reciprocated by combustion of a mixture of fuel (gasoline, etc.) and air to rotate a crankshaft. Output. An intake port and an exhaust port are connected to the combustion chamber of the cylinder, and outside air for generating an air-fuel mixture flows in through the intake port, and exhaust gas after combustion is discharged to the outside through the exhaust port. An intake valve that can be opened and closed is provided at the connection portion of the intake port to the combustion chamber, and an exhaust valve that can be opened and closed is provided at the connection portion of the exhaust port to the combustion chamber. The intake valve is opened when the outside air is taken in, and the exhaust valve is opened when the exhaust gas is discharged.

As shown in FIG. 1, the valve gear 1 of the present embodiment opens and closes the intake valve 10. The present invention is not limited to this embodiment, and may be applied to a valve gear that opens and closes an exhaust valve. The intake valve 10 has a valve face 12 at the lower end of the valve stem 11, and is supported so as to be able to advance and retreat in the direction in which the valve stem 11 extends via a valve guide (not shown). A valve spring 15 is arranged between a retainer 13 provided near the upper end of the valve stem 11 and a spring seat 14 fixed inside the internal combustion engine. The valve spring 15 urges the intake valve 10 so that the valve face 12 closes between the intake port and the combustion chamber.

A rocker arm 16 that can swing around the shaft 16a is provided in the vicinity of the intake valve 10. The arm portion 16b of the rocker arm 16 is in contact with the upper end of the valve stem 11. The intake valve 10 moves forward and backward in response to the swing of the rocker arm 16.

As shown in FIG. 1, the valve gear 1 has a cam 20 supported on a camshaft 17. In the following description, the direction in which the camshaft 17 extends is defined as the axial direction. The axial direction of the camshaft 17 is parallel to the direction in which the shaft 16a of the rocker arm 16 extends. When the crankshaft (not shown) rotates, power is transmitted by a mechanism (not shown) via a chain or belt to rotate the valve stem 11. The camshaft 17 makes one revolution while the crankshaft makes two revolutions.

The camshaft 17 is inserted into a hole formed in the cam 20 that penetrates in the axial direction. The camshaft 17 is provided with a guide key 17a projecting in the outer diameter direction, and a guide groove 20a extending in the axial direction is formed inside the cam 20. By engaging the guide key 17a and the guide groove 20a, the cam 20 is integrally supported with respect to the cam shaft 17 in the rotational direction and is movably supported in the axial direction. The structure for connecting the camshaft 17 and the cam 20 may be other than the guide key 17a and the guide groove 20a, and for example, an involute spline or the like can be used. When the internal combustion engine is operated and power is transmitted from the crankshaft, the camshaft 17 and the cam 20 rotate in the direction of arrow F in FIGS. 1 to 3. The rotation direction of the cam 20 is defined as the traveling direction F.

The cam 20 has a first cam lob 21 and a second cam lob 22 that are adjacent to each other in the axial direction. A cam surface is formed on the peripheral surfaces of the first cam lob 21 and the second cam lob 22, and the cam surface of the first cam lob 21 and the cam surface of the second cam lob 22 change according to the change in the axial position of the cam 20. Alternatively, it abuts on the arm portion 16b of the rocker arm 16 from above. That is, the first cam lob 21 or the second cam lob 22 and the valve stem 11 are in a relationship of sandwiching the arm portion 16b from above and below (see FIG. 2).

In the present embodiment, two intake valves 10 are provided in one cylinder, and the cam 20 is provided with two first cam lobs 21 and two second cam lobs 22 per cylinder correspondingly. However, the number of valves and cam lobs in the present invention is not limited to this.

Although not shown, a locking mechanism for determining the position of the cam 20 in the axial direction is provided between the cam shaft 17 and the cam 20. The locking mechanism holds the cam 20 at a position where the first cam lob 21 abuts on the arm portion 16b of the rocker arm 16 and a position where the second cam lob 22 abuts on the arm portion 16b of the rocker arm 16. For example, a sphere that can move in the radial direction of the cam shaft 17, an urging member that urges the sphere in the radial direction of the cam shaft 17, and two locations formed on the inner surface of the cam 20 at different axial positions. A locking mechanism can be configured by the recesses of the above. By engaging the spherical body that receives the urging force by the urging member with the recess, resistance is added to the movement of the cam 20 in the axial direction, and the cam 20 is held at one of the above two positions.

The valve gear 1 has a switching means for moving the cam 20 in the axial direction. The switching means includes a switching guide unit 23 provided on the cam 20 and an actuator 30 provided in the vicinity of the switching guide unit 23.

The switching guide portion 23 is a cylindrical structure provided at a position different from that of the first cam lob 21 and the second cam lob 22 in the axial direction, and the two guide grooves 24 and the guide groove 25 are provided on the outer surface thereof. have. The guide groove 24 and the guide groove 25 are arranged side by side in the axial direction. FIG. 3 shows a state in which the switching guide unit 23 is expanded in a plane. The guide groove 24 has a first region 24A and a second region 24B formed along the circumferential direction of the cam 20, and a relay portion 24C connecting the first region 24A and the second region 24B. The first region 24A and the second region 24B are offset in the axial direction, and the relay portion 24C has a curved shape having an inclination with respect to the circumferential direction and the axial direction of the cam 20.

The guide groove 25 has a shape symmetrical with respect to the guide groove 24 in the axial direction. That is, the guide groove 25 has a first region 25A and a second region 25B formed along the circumferential direction of the cam 20, and a relay portion 25C connecting the first region 25A and the second region 25B. .. The first region 25A and the second region 25B are offset in the axial direction, and the relay portion 25C has a curved shape having an inclination with respect to the circumferential direction and the axial direction of the cam 20. The inclination of the relay unit 25C is opposite to the inclination of the relay unit 24C.

The actuator 30 has two control pins 32 and a control pin 33 at the lower part of the main body 31. The control pin 32 and the control pin 33 are arranged side by side in the axial direction and extend in the radial direction of the cam 20 (see FIG. 2). The actuator 30 can move the control pin 32 and the control pin 33 individually to a position where the actuator 30 protrudes from the main body 31 and a position where the actuator 30 is pulled toward the main body 31. The means for moving the control pin 32 and the control pin 33 back and forth in the actuator 30 can be hydraulic, electric, or the like.

The control pin 32 is provided at a position corresponding to the guide groove 24, and the control pin 33 is provided at a position corresponding to the guide groove 25. When the control pin 32 and the control pin 33 are pulled toward the main body 31 side, they are separated from the guide groove 24 and the guide groove 25. When the control pin 32 or the control pin 33 protrudes and engages with the guide groove 24 or the guide groove 25, an axial force based on the shape of the guide groove 24 or the guide groove 25 is applied according to the rotation of the cam 20. When the moving force in the axial direction exceeds the holding force of the locking mechanism described above, the cam 20 moves in the axial direction with respect to the cam shaft 17.

More specifically, in a state where the second cam lob 22 is in contact with the arm portion 16b, the first region 24A of the guide groove 24 is in the axial position corresponding to the control pin 32. When the control pin 32 is projected here, the control pin 32 is inserted into the first region 24A. When the phases of the control pin 32 and the first region 24A in the rotation direction are different, the control pin 32 comes into contact with the outer peripheral surface of the switching guide portion 23, and the phase in the rotation direction is changed by the rotation of the cam 20 in the traveling direction F. At the coincident stage, the control pin 32 is inserted into the first region 24A.

When the cam 20 rotates in the traveling direction F with the control pin 32 inserted in the first region 24A of the guide groove 24, the guide groove 24 slides with respect to the control pin 32 and the control pin 32 is moved to the relay portion 24C. Enter (switching start T1 shown in FIG. 3). Then, the wall surface of the relay unit 24C is pressed by the control pin 32 to generate a moving force in the axial direction, and the cam 20 moves in the axial direction in the direction of the arrows S1 of FIGS. 1 and 3. When the control pin 32 reaches the second region 24B, the force for pressing in the axial direction is released (switching end T2 shown in FIG. 3). As a result, the cam 20 is in the axial position where the first cam lob 21 is brought into contact with the arm portion 16b.

In a state where the first cam lob 21 is in contact with the arm portion 16b, the first region 25A of the guide groove 25 is in the axial position corresponding to the control pin 33. When the control pin 33 is projected here, the control pin 33 is inserted into the first region 25A. When the phases of the control pin 33 and the first region 25A in the rotation direction are different, the control pin 33 comes into contact with the outer peripheral surface of the switching guide portion 23, and the phases in the rotation direction match due to the rotation of the cam 20 in the traveling direction F. At the stage, the control pin 33 is inserted into the first region 25A.

When the cam 20 rotates in the traveling direction F with the control pin 33 inserted in the first region 25A of the guide groove 25, the guide groove 25 slides with respect to the control pin 33 and the control pin 33 is moved to the relay portion 25C. Enter (switching start T1 shown in FIG. 3). Then, the wall surface of the relay unit 25C is pressed by the control pin 33 to generate a moving force in the axial direction, and the cam 20 moves in the axial direction in the direction of the arrow S2 in FIGS. 1 and 3. When the control pin 33 reaches the second region 25B, the force for pressing in the axial direction is released (switching end T2 shown in FIG. 3). As a result, the cam 20 is in the axial position where the second cam lob 22 is brought into contact with the arm portion 16b.

By reversing the inclination directions of the relay unit 24C and the relay unit 25C in this way, the cam 20 is slid in the forward and reverse directions in the switching section T from the switching start T1 to the switching end T2 in the rotation direction of the cam 20. , The cam lobs 21 and 22 to be used can be switched. The control pin 32 and the control pin 33 are pulled from the protruding state toward the main body 31 side, and the switching of the cam lob by the movement of the cam 20 is completed.

The first cam lob 21 and the second cam lob 22 have different cam shapes (trajectories on the cam surface). As shown in FIG. 2, the maximum outer diameter of the first cam lob 21 is larger than the maximum outer diameter of the second cam lob 22, and the pressure amount of the first cam lob 21 against the intake valve 10 is larger than that of the second cam lob 22. FIG. 4 shows the opening / closing control of the intake valve 10 by the first cam lob 21 and the second cam lob 22 having different shapes. The horizontal axis of FIG. 4 is the rotation angle of the crankshaft, and the vertical axis is the valve lift amount (opening) of the intake valve 10. As can be seen from the figure, the valve lift amount by the first cam lob 21 is larger than the valve lift amount by the second cam lob 22.

The valve gear 1 described above operates as follows. When the cam 20 rotates with the intake valve 10 closed and the cam surface of the first cam lob 21 or the second cam lob 22 presses the arm portion 16b, which is the actuated portion, downward, the rocker arm 16 presses the arm portion 16b. It swings in the lowering direction, and the arm portion 16b pushes the valve stem 11 against the urging force of the valve spring 15. As a result, the valve lift operation is performed. By the valve lift operation, the valve face 12 opens to the combustion chamber side to communicate the intake port and the combustion chamber. When the rotation position of the cam 20 changes and the pressing of the arm portion 16b by the cam surface of the first cam lob 21 or the second cam lob 22 is released, the valve stem 11 is moved upward by the urging force of the valve spring 15. The intake valve 10 is closed (the valve face 12 closes between the intake port and the combustion chamber).

By driving the actuator 30 and projecting the control pin 32, the operation of the intake valve 10 is controlled by using the first cam lob 21, and by projecting the control pin 33, intake is performed by using the second cam lob 22. The operation of the valve 10 is controlled. By switching to the cam lobs 21 and 22 having different cam shapes and making the valve lift amount of the intake valve 10 variable in this way, it is possible to improve the performance of the internal combustion engine.

By the way, the valve lift amount of the valve gear 1 is switched by the engagement of the control pin 32 and the guide groove 24 (relay portion 24C) or the engagement of the control pin 33 and the guide groove 25 (relay portion 25C). It is performed by generating a moving force (component force) in the axial direction from the rotation of. Therefore, it is required that the power conversion between the actuator 30 and the switching guide unit 23 is smoothly performed while suppressing the load as much as possible. In particular, when the camshaft 17 rotates at high speed, the cam 20 vibrates, and the impact of the contact of the control pin 32 and the control pin 33 with the wall surface of the relay unit 24C and the relay unit 25C becomes strong. Therefore, the control pin of the actuator 30 The load on the 32 and the control pin 33 tends to be large. Further, when the camshaft 17 rotates at high speed, the acceleration when the cam 20 moves in the axial direction tends to increase, and it becomes difficult to secure the accuracy of the cam lob switching operation. The valve gear 1 of the present embodiment suppresses the load on the control pin 32 and the control pin 33, has a compact and highly durable structure, and realizes smooth and high cam lob switching with high operation accuracy. The details will be described below.

As shown in FIG. 2, the cam shapes of the first cam lob 21 and the second cam lob 22 are roughly divided into fixed diameter portions 21A and 22A, lift operation portions 21B and 22B, and lift release portions 21C and 22C. Includes. The fixed diameter portions 21A and 22A are portions where the radius from the rotation center of the cam 20 is uniform and the radius from the rotation center is the smallest. The lift operating portions 21B and 22B have a shape in which the amount of protrusion toward the outer diameter side increases as the fixed diameter portions 21A and 22A proceed in the traveling direction F of the cam 20. The lift release portions 21C and 22C have a shape that reduces the amount of protrusion toward the outer diameter side as the lift operating portions 21B and 22B proceed in the traveling direction F of the cam 20.

When the first cam lob 21 and the second cam lob 22 have their fixed diameter portions 21A and 22A facing (contacting) the arm portion 16b, the valve lift amount is zero and the intake valve 10 is closed. This state is the valve closing region NL shown in FIG. The fixed diameter portion 21A and the fixed diameter portion 22A have the same forming range in the rotation direction of the cam 20, and the valve closing region NL by the first cam lob 21 and the valve closing region NL by the second cam lob 22 coincide with each other. Further, the radius of the fixed diameter portion 21A and the radius of the fixed diameter portion 22A from the rotation center of the cam 20 are the same. That is, the fixed diameter portion 21A and the fixed diameter portion 22A have the same shape.

When the lift operation portions 21B and 22B come into contact with the arm portion 16b as the cam 20 rotates in the traveling direction F, the lift operation of the intake valve 10 is started (valve lift start point Lx in FIG. 4). In the first cam lob 21, the maximum valve lift amount Ly1 is reached when the end of the lift operating portion 21B (the boundary portion with the lift releasing portion 21C) comes into contact with the arm portion 16b. In the second cam lob 22, the maximum valve lift amount Ly2 is reached when the end of the lift operating portion 22B (the boundary portion with the lift releasing portion 22C) comes into contact with the arm portion 16b. The timing at which the maximum valve lift amount Ly1 is reached by the first cam lob 21 (rotation angle of the crankshaft) and the timing at which the maximum valve lift amount Ly2 is reached by the second cam lob 22 (rotation angle of the crankshaft) are different.

Further, when the cam 20 rotates in the traveling direction F and the objects that come into contact with the arm portions 16b are the lift release portions 21C and 22C, the pressure on the arm portions 16b is released and the lift amount of the intake valve 10 gradually decreases. .. In both the first cam lob 21 and the second cam lob 22, the valve lift end point Lz is the time when the ends of the lift release portions 21C and 22C (the boundary portions with the constant diameter portions 21A and 22A) come into contact with the arm portions 16b. , The valve lift amount returns to zero (the intake valve 10 closes). The valve lift end point Lz of the first cam lob 21 and the valve lift end point Lz of the second cam lob 22 coincide with each other.

From the valve lift start point Lx to the valve lift end point Lz is the valve lift region EL in which the intake valve 10 is opened and closed by the first cam lob 21 and the second cam lob 22. As described above, the first cam lob 21 and the second cam lob 22 have the same shape of the fixed diameter portion 21A and the fixed diameter portion 22A corresponding to the valve closing region NL, but they are also in the valve lift region EL. It has a part where the cam shapes match. The cam-shaped matching portion of the first cam lob 21 and the second cam lob 22 is a matching region Q1 which is a predetermined phase range on the valve lift start side including the valve lift start point Lx. The coincidence region Q1 is included in the lift operation portions 21B and 22B of the first cam lob 21 and the second cam lob 22 starting from the valve lift start point Lx.

When switching the cam lob to be used by moving the cam 20 in the axial direction, if there is a step between the first cam lob 21 and the second cam lob 22, this step hits the side portion of the arm portion 16b and the movement is restricted. It may be stressed or stressed by a collision. Therefore, in order to realize smooth operation, it is required to move the cam 20 in the axial direction in a state where the arm portion 16b is in contact with the region where the cam shapes of the first cam lob 21 and the second cam lob 22 match. .. Here, in the valve gear 1 of the present embodiment, in addition to the fixed diameter portion 21A and the fixed diameter portion 22A corresponding to the valve closing region NL, the valve lift region EL continuous with the fixed diameter portion 21A and the fixed diameter portion 22A. The cam shapes of the first cam lob 21 and the second cam lob 22 also match in the matching region Q1. Therefore, the rotation angle of the cam 20 capable of performing the cam lob switching operation is larger than that in the case where only the valve closing region NL is set as the cam lob switching range.

The switching section T from the switching start T1 to the switching end T2 in the switching guide portions 23 (guide grooves 24 and 25) described above is shown in FIG. 4 in correspondence with the timing of the valve lift operation by the cam 20. As can be seen from the figure, when the valve lift end point Lz is reached, the cam shapes of the first cam lob 21 and the second cam lob 22 that abut on the arm portion 16b come to match between the fixed diameter portion 21A and the fixed diameter portion 22A. The configurations of the relay portions 24C and 25C of the guide grooves 24 and 25 are set so that the switching operation is started at the same timing. Then, a part of the switching section T on the final end side overlaps with the valve lift region EL (overlap range T3). In the overlapping range T3 between the switching section T and the valve lift area EL, the cam shapes of the lift operating portions 21B and 22B of the first cam lob 21 and the second cam lob 22 coincide with each other following the fixed diameter portion 21A and the fixed diameter portion 22A. It is included in the matching area Q1. Therefore, even in the overlapping range T3, the cam 20 can be moved in the axial direction, and the target with which the arm portion 16b abuts can be smoothly shifted from the first cam lob 21 to the second cam lob 22.

When the rotation angle of the cam 20 that can be used for the cam lob switching operation is large as in the present embodiment, the amount of axial movement of the cam 20 per unit rotation angle can be suppressed to be small. That is, the degree of inclination of the relay portions 24C and 25C of the guide grooves 24 and 25 with respect to the rotation direction can be made gentle, and the time required for the cam 20 to move in the axial direction can be lengthened. As a result, the cam 20 is moved in an excessive axial direction due to the inertia of the cam 20 as compared with the case where the control pin 32 and the control pin 33 are brought into contact with the guide surface having a steep inclination with respect to the rotation direction to move the cam 20 rapidly in a short time. Sliding is less likely to occur, and accurate cam lob switching operation can be performed even in a situation where the cam shaft 17 rotates at high speed.

The end point of the axial movement of the cam 20 (switching end T2) is set in the latter half of the matching region Q1 where the cam shapes of the lift operation portions 21B and 22B of the first cam lob 21 and the second cam lob 22 match. Has been done. In this way, by using the portion where the cam shapes of the first cam lob 21 and the second cam lob 22 match each other for as long as possible, the time required for the cam lob switching operation can be further increased, and the above-mentioned effect can be enhanced. Can be done.

Further, the momentary load received by the control pins 32 and 33 inserted into the guide grooves 24 and 25 from the wall surfaces of the guide grooves 24 and 25 can be reduced, and the wear between the control pins 32 and 33 and the switching guide portion 23 is suppressed. , The durability of the mechanism is improved. As a result, the thickness of the switching guide portion 23 and the like can be suppressed to reduce the size and weight of the cam 20, and the internal combustion engine can be rotated at a high speed.

Further, in the valve lift region EL, the camshaft 17 and the arm portion are formed by the force of the first cam lob 21 and the second cam lob 22 pushing down the arm portion 16b and the force of the valve spring 15 pushing up the intake valve 10 (valve stem 11). A holding force K (see FIG. 2) that sandwiches a part of the first cam lob 21 and the second cam lob 22 acts between 16b. By setting the end point of the axial movement of the cam 20 (switching end T2) under the state where the holding force K is working, a damper effect that reduces vibration and excessive sliding of the cam 20 can be obtained. As a result, the operating accuracy from the cam 20 to the intake valve 10 is improved.

As described above, the cam 20 of the valve gear 1 of the present embodiment has a predetermined phase range on the valve lift start side including the valve lift start point Lx in the valve lift region EL that opens and closes the intake valve 10. In the matching region Q1), the shapes of the adjacent first cam lob 21 and the second cam lob 22 are substantially matched. Then, the end point of the axial movement of the cam 20 (switching end T2) is set in the matching region Q1. As a result, it has become possible to smoothly switch the cam lobs with high operating accuracy in a compact and lightweight configuration while corresponding to the high rotation speed of the cam shaft 17 and the cam 20.

In the above-described embodiment, the cam shapes of the first cam lob 21 and the second cam lob 22 are formed in the matching region Q1 which is a predetermined phase range on the valve lift start side including the valve lift start point Lx in the valve lift region EL. Matching. On the other hand, as in the modified example shown in FIG. 5, it is also possible to match the cam shapes of the first cam lob 21 and the second cam lob 22 on the valve lift end side of the valve lift region EL.

As shown in FIG. 5, the portion of the valve lift region EL where the cam shapes of the first cam lob 21 and the second cam lob 22 match each other is a predetermined phase range on the valve lift end side including the valve lift end point Lz. It is the coincidence area Q11. The matching area Q11 is included in the lift release portions 21C and 22C of the first cam lob 21 and the second cam lob 22.

In the modified example of FIG. 5, the cam lob switching operation is performed at the timing when the arm portion 16b of the rocker arm 16 comes into contact with the coincident region Q11 of the first cam lob 21 and the second cam lob 22 before reaching the valve lift end point Lz. The configuration of the relay portions 24C and 25C of the guide grooves 24 and 25 is set so that is started (switching start T11). That is, a part of the start side of the switching section T overlaps with the valve lift area EL (overlap range T13). The overlapping range T13 between the switching section T and the valve lift area EL is included in the matching area Q11 in which the cam shapes of the lift release portions 21C and 22C of the first cam lob 21 and the second cam lob 22 match. Therefore, the arm portion 16b is hit by starting the movement of the cam 20 in the axial direction from the overlapping range T13 in front of the fixed diameter portion 21A and the fixed diameter portion 22A to secure a long time required for the movement of the cam 20. The object in contact can be smoothly and accurately transferred from the first cam lob 21 to the second cam lob 22.

The start point of the axial movement of the cam 20 (switching start T11) is set in the first half of the matching region Q11 where the cam shapes of the lift release portions 21C and 22C of the first cam lob 21 and the second cam lob 22 match. Has been done. In this way, by using the portion where the cam shapes of the first cam lob 21 and the second cam lob 22 match each other for as long as possible, the time required for the cam lob switching operation can be further increased, and the above-mentioned effect can be enhanced. Can be done.

Further, when the control pins 32 and 33 enter the guide grooves 24 and 25, the collision and wear of the control pins 32 and 33 with respect to the wall surfaces of the guide grooves 24 and 25 are reduced, and the control pins 32 and 33 and the switching guide unit 23 are reduced. It can be miniaturized. As a result, the cam 20 can be made smaller and lighter to cope with higher rotation of the internal combustion engine.

Further, as described above, in the valve lift region EL, a holding force K (see FIG. 2) that sandwiches a part of the first cam lob 21 and the second cam lob 22 acts. By setting the start point (switching start T11) of the axial movement of the cam 20 under the state in which the holding force K is working, a damper effect that reduces the vibration of the cam 20 can be obtained. As a result, the collision energy when the control pins 32 and 33 are inserted into the guide grooves 24 and 25 is attenuated, the control pins 32 and 33 can easily enter the guide grooves 24 and 25, and the operation from the cam 20 to the intake valve 10 is performed. Accuracy is improved.

In the example of FIG. 4, a matching region Q1 in which the cam shapes of the first cam lob 21 and the second cam lob 22 match is set on the valve lift start side of the valve lift region EL, and in the example of FIG. 5, the valve lift region EL A matching region Q11 in which the cam shapes of the first cam lob 21 and the second cam lob 22 match is set on the valve lift end side. As in these examples, the cam shape matching area may be provided only on one of the valve lift start side and the valve lift end side, but the cam shape matching area may be provided on both the valve lift start side and the valve lift end side. It is also possible to provide it.

The present invention is not limited to the above-described embodiment or modification, and can be modified in various ways. In the above-described embodiment and modification, the configuration, control, and the like shown in the accompanying drawings are not limited to this, and can be appropriately changed within the range in which the effects of the present invention are exhibited. In addition, it can be appropriately modified and implemented as long as it does not deviate from the scope of the object of the present invention.

For example, in the above-described embodiment or modification, the switching means for moving the cam 20 in the axial direction is the start point (switching start T1, T11) or the end point of the axial movement of the cam 20 depending on the groove shape of the guide grooves 24 and 25. (Switching end T2, T12) is set. Unlike this, it is also possible to set the start point and the end point of the axial movement of the cam 20 by the operation of the actuator 30 by the control.

Although the above-described embodiment and modification are applied to the operation control of the intake valve 10, the present invention can also be applied to the valve gear that operates the exhaust valve.

The above-described embodiment and modification are applied to a variable valve lift mechanism that changes the lift amount of the valve by switching the cam lob, but if the mechanism switches the cam lob by axial movement of the cam, the valve can be switched by switching the cam lob. It can also be applied to a variable valve timing mechanism that changes the operation timing.

The internal combustion engine provided with the valve gear of the present invention is not limited to the engine for vehicles. Regardless of the application, it can be applied to all internal combustion engines having the same configuration.

As described above, the present invention has an effect that smooth and highly accurate switching of cam lobs can be realized in a valve gear of an internal combustion engine having a plurality of cam lobs having different cam shapes, and in particular, the valve gear. It is useful for internal combustion engines that require smaller size and lighter weight and higher rotation drive system.

1: Valve gear 10: Intake valve 15: Valve spring 16: Rocker arm 16b: Arm part (operated part)
17: Camshaft 20: Cam 21: First cam lob 21A: Fixed diameter part 21B: Lift operating part 21C: Lift releasing part 22: Second cam lob 22A: Fixed diameter part 22B: Lift operating part 22C: Lift releasing part 23: Switching Guide section (switching means)
24, 25: Guide grooves 24A, 25A: First area 24B, 25B: Second area 24C, 26C: Relay unit 30: Actuator (switching means)
32, 33: Control pin (control member)
EL: Valve lift area Lx: Valve lift start point Lz: Valve lift end point NL: Valve closing area Q1, Q11: Matching area T: Switching section T1, T11: Switching start T2, T12: Switching end T3, T13: Overlapping range

Claims (5)

A plurality of cam lobs, each having a different cam shape, are provided side by side in the axial direction of the cam shaft, and a cam that can move in the axial direction integrally with the cam shaft in the rotational direction.
A switching means for moving the cam in the axial direction with respect to the camshaft, and
A valve gear of an internal combustion engine that opens and closes a valve connected to a driven portion that comes into contact with the cam lob by rotating the cam.
The cam substantially matches the shapes of adjacent cam lobs in a predetermined phase range on the valve lift start side including the valve lift start point in the valve lift region for opening and closing the valve.
A valve gear for an internal combustion engine, characterized in that the end point of the axial movement of the cam by the switching means is set within the predetermined phase range. The valve gear for an internal combustion engine according to claim 1, wherein the cam sets the end point of the axial movement of the cam in a portion later than the middle of the predetermined phase range. A plurality of cam lobs, each having a different cam shape, are provided side by side in the axial direction of the cam shaft, and a cam that can move in the axial direction integrally with the cam shaft in the rotational direction.
A switching means for moving the cam in the axial direction with respect to the camshaft, and
A valve gear of an internal combustion engine that opens and closes a valve connected to a driven portion that comes into contact with the cam lob by rotating the cam.
The cam substantially matches the shapes of adjacent cam lobs in a predetermined phase range on the valve lift end side including the valve lift end point in the valve lift region for opening and closing the valve.
A valve gear of an internal combustion engine, characterized in that a start point of the axial movement of the cam by the switching means is set within the predetermined phase range. The valve gear of an internal combustion engine according to claim 3, wherein the cam sets a start point of the axial movement of the cam in a portion in the first half of the middle of the predetermined phase range. The switching means includes a guide groove formed on the peripheral surface of the cam and a control member capable of being inserted into and detached from the guide groove.
The method according to any one of claims 1 to 4, wherein the control member abuts on the wall surface of the guide groove and generates a force for moving the cam in the axial direction from the rotation of the cam. Valve gear for internal combustion engines.

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