JP2006144742A - Variable valve system for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a variable valve system for an internal combustion engine improving durability of the system and mountability on the engine. <P>SOLUTION: A rocker arm mechanism 20 is abutted on a first arm 21 and a second arm 22, and is provided with a third arm 23 transmitting rocking displacement of the second arm to the first arm. An axial center C3 of a support shaft of the third arm is provided on a position where first shortest distance L1 from the axial center of the support shaft to an action line of force F1 acting on an abutment point S1 on the first arm is shorter than second shortest distance L2 from the axial center of the support shaft to an action line of force F2 acting on an abutment point S2 on the second arm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a variable valve operating apparatus for an internal combustion engine capable of continuously changing the lift characteristics of intake and exhaust system valves.

This type of variable valve device can continuously change the lift characteristics (drive phase and lift amount) of the intake and exhaust valves in accordance with the operating state of the internal combustion engine. Thereby, for example, in an automobile engine, acceleration of exhaust gas purification, reduction of fuel consumption, and the like are achieved.
In addition, there are various mechanisms such as switching a plurality of cams or using gears and springs in the device, but the complexity of this device makes it difficult to mount it on the engine. Has been disclosed (for example, see Patent Document 1).
JP 2004-150301 A

  By the way, in the variable valve operating apparatus described in Patent Document 1, the intake valve receives the force from the rocker arm mechanism to open the intake passage, and closes the intake passage by a spring force biased in the valve closing direction. This spring force is transmitted as a reaction force to the rocker arm mechanism. Specifically, the spring force pushes up the end of the first arm in the valve closing direction, and the force transmitted to the first arm is transmitted to the second arm via the third arm, and finally Is transmitted to the cam.

  Here, as described in the above-mentioned Patent Document 1, in the variable valve gear that can continuously change the lift characteristics by changing the swing range of the second arm, the contact point between the second arm and the cam is changed. There is a concern that the cam load acting on this cam will become excessively large with the change. In this case, it is conceivable to increase the width of the cam. However, this requires a large space in the front-rear direction of the engine, and there is a problem that the mountability is deteriorated.

As described above, in the above conventional technique, even if the apparatus can be simplified, there are still problems in the durability and mountability of the apparatus.
The present invention has been made in view of such a problem, and an object of the present invention is to provide a variable valve operating apparatus for an internal combustion engine that can improve the durability of the apparatus and the mountability to the engine.

  In order to achieve the above object, a variable valve operating apparatus for an internal combustion engine according to claim 1 is provided with a rocker arm mechanism that opens and closes an intake valve or an exhaust valve of the internal combustion engine, and a rocker arm that is rotatably provided in the internal combustion engine. A rocker shaft having an eccentric shaft that is engaged with the mechanism, and a camshaft that is rotatably provided in the internal combustion engine and has a cam that drives the rocker arm mechanism. The rocker arm mechanism swings about the axis of the rocker shaft as a fulcrum, and the closing direction of the intake valve or exhaust valve can be changed by changing the lift characteristics of the intake valve or exhaust valve. A first arm that can drive an intake valve or an exhaust valve against a spring force biased by the second arm, a second arm that is driven by a cam and swings about the axis of the eccentric shaft; Each of the second arm and the first arm, and a third arm that transmits the swinging displacement of the second arm to the first arm. The third arm includes the first arm and the third arm. The axis of the support shaft provided between the second arm and the second arm swings around a fulcrum, and the axis of the support shaft acts from the axis of the support shaft to the point of contact with the first arm. The first shortest distance to the line is provided at a position smaller than the second shortest distance from the axis of the support shaft to the line of action of the force acting on the contact point with the second arm. It is a feature.

  According to the second aspect of the present invention, the shaft center of the support shaft is at a position opposite to the shaft center of the rocker shaft across the contact point with the first arm and the contact point with the second arm. And when the lift amount of the intake valve or the exhaust valve is maximized, the difference between the first shortest distance and the second shortest distance is minimized.

  Therefore, according to the variable valve operating apparatus for an internal combustion engine of the first aspect of the present invention, a reaction force by a spring force that urges the intake valve or the exhaust valve in the valve closing direction acts on the variable valve operating apparatus. Specifically, the reaction force acts on the contact point between the first arm and the third arm via the first arm, and subsequently, the third arm and the third arm via the third arm. It acts on the contact point with the second arm, and finally acts on the cam from this second arm.

  The moment about the support axis of the third arm is obtained by the first shortest distance determined by the force acting on the contact point with the first arm and the first shortest distance from the axis of the support shaft to the line of action of this force. And a second moment determined by a force acting on the contact point with the second arm and a second shortest distance from the axis of the support shaft to the line of action of the force, and the first moment and The second moment is balanced.

  Here, the position of the axis of the support shaft is provided at a position where the first shortest distance related to the first moment is always smaller than the second shortest distance related to the second moment. That is, in the moment balance, the force acting on the contact point with the second arm is always smaller than the force acting on the contact point with the first arm. Therefore, the cam load acting on the cam from the second arm can be suppressed, the durability of the variable valve apparatus is improved, and the reliability in terms of strength is improved.

Further, if the cam load can be reduced, the cam width can be reduced. Therefore, the space in the front-rear direction of the internal combustion engine is small, and the mountability to the engine can be improved.
According to the second aspect of the present invention, if the cam load can be suppressed even when the lift amount at which the reaction force due to the spring force is maximum is maximum, the durability of the variable valve device can be reduced. Mountability to the engine is further improved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a variable valve gear 2 for an internal combustion engine according to this embodiment. As shown in the schematic diagram of FIG. 1, the variable valve operating device 2 is disposed in a cylinder head portion of an automobile engine, drives an intake valve 4 via a rocker arm mechanism 20, and opens and closes an intake passage 6. .
Specifically, the cylinder head is provided with a camshaft 12 so as to be rotatable, and the rotation of the cam 10 having the cam nose 14 is appropriately converted into the reciprocating swing of the rocker arm mechanism 20 according to the rotation of a crankshaft (not shown). Then, a downward force is applied to the intake valve 4. Thereby, the intake valve 4 opens the intake passage 6. On the other hand, the intake valve 4 is provided with a valve closing biasing spring 8, which is biased in a direction to close the intake passage 6 and applies an upward force. This force is transmitted to the rocker arm mechanism 20 as a reaction force.

  Further, a rocker shaft 16 is rotatably provided on the cylinder head, and the rocker shaft 16 and the camshaft 12 are disposed in parallel. Further, the rocker shaft 16 is provided with an eccentric shaft 18. Specifically, as shown in FIG. 2, the axis C <b> 2 of the eccentric shaft 18 is eccentric with respect to the axis C <b> 1 of the rocker shaft 16. The eccentric shaft 18 rotates with respect to the axis C1 of the rocker shaft 16 when the rocker shaft 16 is rotated by rotating means using a motor or the like.

  A rocker arm mechanism 20 is engaged with the eccentric shaft 18. More specifically, the rocker arm mechanism 20 of the present embodiment includes a valve drive arm (first arm) 21, a characteristic adjustment arm (second arm) 22, and a displacement transmission arm (third arm) 23. As will be described later, the characteristic adjusting arm 22 is engaged with the eccentric shaft 18.

  The valve drive arm 21 has a front end portion 31 that presses the intake valve 4 and receives the spring force of the valve closing biasing spring 8. The front end portion 31 is a rear end portion located on the displacement transmission arm 23 side. 41 and the rocking | fluctuation support part 61 supported by the rocker shaft 16 so that rocking | fluctuation is possible. As a result, the valve drive arm 21 swings about the axis C1 of the rocker shaft 16 as a fulcrum, and drives the intake valve 4 against the spring force. The rear end portion 41 is provided with a contact roller 51, and this contact roller 51 is in contact with the displacement transmission arm 23. That is, the force R transmitted to the tip portion 31 is transmitted to the displacement transmission arm 23 via the contact roller 51.

  On the other hand, the characteristic adjustment arm 22 has a swing support portion 32 that is swingably supported by the eccentric shaft 18, and swings about the axis C <b> 2 of the eccentric shaft 18 as a fulcrum according to the rotation of the cam 10. . The swing support portion 32 is connected to a connection portion 42 having contact rollers 52 and 62. The contact roller 52 is in contact with the displacement transmission arm 23, and the contact roller 62 is in contact with the cam 10. Therefore, the force transmitted to the displacement transmission arm 23 is transmitted to the characteristic adjustment arm 22 through the contact roller 52 and further transmitted to the cam 10 through the contact roller 62.

When the pivoting means pivots the rocker shaft 16, the eccentric shaft 18 is displaced around the axis C <b> 1 of the rocker shaft 16. This displacement changes the rotation phase of the characteristic adjustment arm 22 with respect to the cam 10 to the retard side or the advance side. As a result, the lift characteristics (drive phase and lift amount) of the intake valve 4 are continuously changed.
As described above, the displacement transmission arm 23 is in contact with the contact roller 51 of the valve drive arm 21 and the contact roller 52 of the characteristic adjustment arm 22, respectively. 21 can be transmitted.

  Specifically, the displacement transmission arm 23 includes a conversion surface portion 43 and a non-conversion surface portion 53 that are in rolling contact with the contact roller 51, and a conversion surface portion 63 that is in contact with the contact roller 52. At the position where each contact roller 51, 52 is in contact with the conversion surface portions 43, 63, the swing displacement of the characteristic adjustment arm 22 is transmitted to the valve drive arm 21. On the other hand, in the range where the contact roller 51 is in contact with the non-conversion surface portion 53, the swinging displacement of the characteristic adjustment arm 22 is canceled even if the contact roller 52 is in contact with the conversion surface portion 63. It is not transmitted to the valve drive arm 21.

  The displacement transmission arm 23 is swingably supported by the support shaft 33. More specifically, the axis C3 of the support shaft 33 in the present embodiment is opposite to the axis C1 of the rocker shaft 16 across the contact point S1 with the valve drive arm 21 and the contact point S2 with the characteristic adjustment arm 22. The displacement transmission arm 23 swings around the axis C3 of the support shaft 33 as a fulcrum. The displacement transmitting arm 23 is subjected to a spring force in the counterclockwise direction with respect to the axis C3, in other words, the direction in which the conversion surface portion 63 is brought into contact with the contact roller 52.

  Here, as shown in FIG. 2, the force R transmitted to the tip 31 is transmitted from the valve drive arm 21 to the displacement transmission arm 23 as a force F <b> 1. This force F1 acts on a line connecting the rotation center of the contact roller 51 and the contact point S1 of the valve drive arm 21. On the other hand, this force F1 is transmitted from the displacement transmission arm 23 to the characteristic adjustment arm 22 as a force F2. This force F <b> 2 acts on a line connecting the contact point S <b> 2 with the characteristic adjustment arm 22 and the rotation center of the contact roller 52. That is, the moment balance around the support shaft 33 is calculated by multiplying the force F1 by the first moment M1 obtained by multiplying the first shortest distance L1 from the axis C3 of the support shaft 33 to the line of action of the force F1, and the force. It is obtained by the algebraic sum of F2 and the second moment M2 obtained by multiplication of the second shortest distance L2 from the axis C3 of the support shaft 33 to the line of action of the force F2.

  The axis C3 of the support shaft 33 is provided at a position where the first shortest distance L1 is smaller than the second shortest distance L2. In particular, the axial center C3 is the most retarded side, that is, even when the rotational phase of the characteristic adjustment arm 22 with respect to the cam 10 is changed to the side where the maximum lift amount of the intake valve 4 is obtained, The ratio (L1 / L2) between the first shortest distance L1 and the second shortest distance L2 is 1 when the valve lift is maximum, and the difference between the first shortest distance L1 and the second shortest distance L2 is It is provided at the minimum position. In other words, the position of the axis C3 is provided at a position where the force F2 is always smaller than the force F1.

Next, operation | movement of the variable valve apparatus 2 of this embodiment is demonstrated.
In FIG. 2, when the camshaft 12 is rotated around the counter hour hand, the characteristic adjusting arm 22 swings with respect to the axis C <b> 2 according to the cam curve of the cam 10. Specifically, the characteristic adjustment arm 22 swings around the counter hour hand as it approaches the apex of the cam nose portion 14. At the same time, the displacement transmission arm 23 swings around the hour hand with respect to the axis C3, and when the conversion surface 43 pushes up the contact roller 51, the valve drive arm 21 swings around the counter hour hand with respect to the axis C1. Therefore, the intake valve 4 moves downward and the intake passage 6 is opened.

  Here, when the rocker shaft 16 is rotated around the hour hand as viewed from the retarded side, that is, in FIG. 2, the eccentric shaft 18 rotates around the hour hand relative to the axis C <b> 1 of the rocker shaft 16. As a result, the contact point S between the contact roller 62 of the characteristic adjustment arm 22 and the cam 10 moves counterclockwise on the cam curve, and at the same time, the contact point S2 with the characteristic adjustment arm 22 rotates on the conversion surface 63. It moves in a direction away from the center C3. That is, in this case, the displacement transmission arm 23 swings around the hour hand with respect to the axis C3, and the contact point S1 is located at a point far from the non-conversion surface portion 53, so that the contact period with the non-conversion surface portion 53 is long. Shorter. As a result, the valve drive arm 21 functions to open the intake valve 4 from when the rotation angle of the cam 10 is small.

  On the other hand, when the eccentric shaft 18 rotates counterclockwise as viewed in FIG. 2, the contact point S moves on the cam curve around the hour hand, and at the same time, the contact point S2 is on the conversion surface 63. Is moved in a direction approaching the axis C3. That is, in this case, the displacement transmission arm 23 swings around the counterclockwise hand with respect to the axis C3, and the contact point S1 is located at a point close to the non-conversion surface portion 53. The period becomes longer. As a result, the valve drive arm 21 functions so as not to open the intake valve 4 even if the rotation angle of the cam 10 increases.

  As shown in FIG. 3, with respect to the uniform rotation of the cam 10, the lift amount increases as it is set to the retard side, while as the cam 10 is set to the advance side. The lift amount becomes smaller. Further, when it is set to the most advanced angle side, the lift becomes a resting state. Further, the maximum lift amount (indicated by ● in the figure) in each valve lift mode is also retarded as it is set to the retard side. Thus, in the variable valve operating apparatus 2 of the present embodiment, the lift characteristics (drive phase and lift amount) of the intake valve 4 can be continuously changed according to the rotation ratio of the rocker arm 16. When the lift characteristics require a high intake amount with a high rotation and a high load, when the low intake amount with a low rotation and a low load is required on the retard side, the activity of the exhaust gas aftertreatment device When it is desired to raise the exhaust gas temperature for the purpose of achieving the above, by changing to the advance side, the automobile engine can achieve exhaust gas purification promotion, fuel consumption reduction, and the like.

  As described above, in the present embodiment, although the spring force that urges the intake valve 4 in the valve closing direction acts as a reaction force on the variable valve apparatus 2, it is difficult to transmit this spring force to the cam 10. Pay attention. Then, the position of the axis C3 of the support shaft 33 of the displacement transmission arm 23 is set so that the first shortest distance L1 related to the first moment M1 is always smaller than the second shortest distance L2 related to the second moment M2. It has established.

  More specifically, as shown in FIG. 4, even when the lift amount fluctuates over a wide range as shown in FIG. 3, the load transmission ratio (L1 / L2: (Indicated by ● in the figure) is 1 or less. In particular, the shaft of the support shaft 33 is set so that the load transmission ratio becomes 1 at the time of maximum valve lift in the valve lift mode that is set to the most retarded angle and has the maximum lift amount. The center C3 is provided at a position where the force F2 acting on the contact point S2 with the characteristic adjusting arm 22 is always smaller than the force F1 acting on the contact point S1 with the valve drive arm 21. Therefore, it can be seen that the cam load F acting on the contact point S between the characteristic adjustment arm 22 and the cam 10 does not become excessively large.

Then, as shown in FIG. 5, in view of the cam surface pressure caused by the static load due to the spring force, this cam surface pressure (indicated by ● in the figure) is less than the shaded portion in the range where the load transmission ratio is less than 1. Is also suppressed to the lower value. That is, it turns out that the measure for lowering the cam surface pressure is not required for the variable valve operating apparatus.
As a result, according to the variable valve operating apparatus 2 of the present embodiment, the cam load F can be sufficiently suppressed even in the case of the maximum lift amount at which the force R transmitted to the tip portion 31 is maximized. The durability is further improved, and the reliability in terms of strength is greatly improved.

  Moreover, in this case, the cam width of the cam 10 can be small, and the space in the front-rear direction of the engine can be reduced, so that a compact variable valve operating device 2 can be obtained. Therefore, even an engine having a relatively short engine longitudinal dimension per cylinder, for example, an engine having a small cylinder bore and a large stroke amount even with the same displacement, can be easily mounted.

  Further, the axis C3 of the support shaft 33 in the present embodiment is provided not at the vicinity of the axis C1 of the rocker shaft 16 but at a position away from the axis C1 of the rocker shaft 16 with the contact point S1 and the contact point S2 interposed therebetween. The displacement transmission arm 23 is provided with a non-conversion surface portion 53 on the side abutting against the valve drive arm 21, whereas the non-conversion surface portion is provided on the side abutting against the characteristic adjustment arm 22. It is not done. Accordingly, the lift characteristics can be easily adjusted and the displacement transmission arm can be easily processed as compared with the case where the non-converting surface portions are provided on the abutting sides.

The description of one embodiment of the present invention is finished above, but the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, in the above-described embodiment, the variable valve gear 2 that can continuously change the lift characteristics of the intake valve 4 has been described. However, the present invention is not necessarily limited to this form. May be a variable valve operating device capable of continuously changing the above. In this case as well, it is possible to improve the durability of the apparatus and the mountability to the engine as described above.

  Further, in the above-described embodiment, the axis C3 of the support shaft 33 is opposite to the axis C1 of the rocker shaft 16 with the contact point S1 with the valve drive arm 21 and the contact point S2 with the characteristic adjustment arm 22 interposed therebetween. In the position. However, for example, by increasing the distance between the contact roller 52 and the contact roller 62, or by changing the shape of the conversion surface portion 63, the shaft center of the support shaft is as high as the shaft center of the rocker shaft. Alternatively, it may be provided at a position lower than the axis of the rocker shaft. In this case, in addition to the space in the longitudinal direction of the engine, the space in the vertical direction of the engine can be reduced.

1 is a schematic configuration diagram of a variable valve operating apparatus for an internal combustion engine according to an embodiment of the present invention. It is a figure explaining transmission of the force etc. in the variable valve apparatus of FIG. It is a figure explaining the characteristic of the lift in the variable valve apparatus of FIG. It is a figure which shows the relationship between the load transmission ratio and lift amount of the 3rd arm in the variable valve apparatus of FIG. It is a figure which shows the relationship between the cam surface pressure and the load transmission ratio of a 3rd arm in the variable valve apparatus of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 Variable valve operating apparatus 4 Intake valve 8 Valve closing bias spring 10 Cam 12 Cam shaft 16 Rocker shaft 18 Eccentric shaft 20 Rocker arm mechanism 21 Valve drive arm (first arm)
22 Characteristic adjustment arm (second arm)
23 Displacement transmission arm (third arm)
33 Support shaft

Claims (2)

A rocker arm mechanism that opens and closes an intake valve or an exhaust valve of the internal combustion engine, a rocker shaft that is rotatably provided in the internal combustion engine and includes an eccentric shaft that is engaged with the rocker arm mechanism, and a rotary shaft that rotates to the internal combustion engine. And a camshaft provided with a cam for driving the rocker arm mechanism, the position of the eccentric shaft is changed by rotation of the rocker shaft, and the lift characteristics of the intake valve or the exhaust valve are changed. A variable valve gear that can be changed,
The rocker arm mechanism swings about the axis of the rocker shaft as a fulcrum and can drive the intake valve or the exhaust valve against a spring force biased in the valve closing direction of the intake valve or the exhaust valve. A first arm, a second arm that is driven by the cam and swings about the axis of the eccentric shaft, and is in contact with the second arm and the first arm, respectively. A third arm for transmitting the swing displacement of the two arms to the first arm,
The third arm swings around the axis of a support shaft provided between the first arm and the second arm, and the axis of the support shaft is the axis of the support shaft. The first shortest distance from the center to the line of force acting on the contact point with the first arm is the line of force acting on the contact point with the second arm from the axis of the support shaft. A variable valve operating apparatus for an internal combustion engine, wherein the variable valve operating apparatus is provided at a position that is smaller than the second shortest distance.   An axis of the support shaft is provided at a position on the opposite side of the axis of the rocker shaft with respect to the contact point with the first arm and the contact point with the second arm, and the intake valve Alternatively, when the lift amount of the exhaust valve is maximized, the exhaust valve is provided at a position where a difference between the first shortest distance and the second shortest distance is minimized. The variable valve operating apparatus for an internal combustion engine.

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