JP2007077940A - Variable valve train - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a variable valve train simply constructed with a less number of components to produce stable valve property. <P>SOLUTION: The variable valve train 1 comprises a rotary cam 4 provided on a cam shaft 2, an input roller 16 to be displaced in contact with the rotary cam 4, a rocker arm 6 for driving a valve 5, a transmission arm 19 for transmitting the power of the rotary cam 4 to the rocker arm 6, a variable arm 15 contacting the transmission arm 19, and an actuator 13 for driving the variable arm 15. The transmission arm 19 is connected at its base end to the input roller 16. On the front end side of the transmission arm 19, there are provided a drive part 22 contacting the rocker arm 6 and a cam surface 21 which a rotary contactor 20 of the rocker arm 15 contacts. With the turn of the variable arm 15, an initial contact position between the cam surface 21 and the rotary contactor 20 is changed. A lift portion of the cam surface 21 is formed closer to the base end side of the transmission arm 19 than a base portion. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a variable valve mechanism that controls valve characteristics in accordance with the operating state of an internal combustion engine.

  2. Description of the Related Art Conventionally, a variable valve mechanism that uses a link to control the lift amount, working angle, and opening / closing timing of a valve is known. For example, the variable valve mechanism 100 of Patent Document 1 shown in FIG. 11 includes a camshaft 101 that is rotated by a crankshaft of an internal combustion engine. A rotating cam 102 is fixed on the camshaft 101 so as to be integrally rotatable, and a drive arm 104 that drives a valve 110 via a valve lifter (valve member) 103 is supported so as to be relatively rotatable.

A swing arm 106 is supported via a variable cam 107 on a control shaft 105 parallel to the camshaft 101. The input end of the swing arm 106 is connected to the rotary cam 102 via a ring-shaped link 108, and the output end of the swing arm 106 is connected to the drive arm 104 via a rod-shaped link 109. The control shaft 105 is driven by an actuator, and the swing arm 106 is displaced by the eccentric rotation of the variable cam 107, so that the initial position of the drive arm 104 with respect to the rotating cam 102 is changed.
JP-A-11-324625

  However, according to the conventional variable valve mechanism 100, in order to transmit the power of the rotating cam 102 to the valve lifter 103, the two links 108 and 109 and the two arms 104 and 106 are required. For this reason, the number of parts of the variable valve mechanism 100 is increased, which not only complicates the configuration, but also causes a problem that valve characteristics become unstable due to an assembly error.

  An object of the present invention is to solve the above-mentioned problems and to provide a variable valve mechanism that can obtain stable valve characteristics with a simple configuration with a small number of parts.

  In order to solve the above problems, a variable valve mechanism of the present invention includes a rotating cam provided on a camshaft, an input member that contacts and displaces the rotating cam, a valve operating member that drives a valve, It consists of a transmission arm that transmits the power of the rotating cam to the valve member, a variable arm having a contact portion that contacts the transmission arm, and an actuator that drives the variable arm, and connects the base end of the transmission arm to the input member, Provided on the distal end side of the transmission arm is a drive unit that drives the valve member and a cam surface that contacts the contact portion of the variable arm, and changes the initial contact position between the cam surface and the contact portion as the variable arm moves. It is characterized by that.

Here, the following structure is employable regarding a rotation cam.
(1) The rotating cam is provided with an equal radius portion that keeps the valve lift amount at zero within a predetermined angle range, and a nose portion that increases the valve lift amount at the remaining angle range.
(2) Use an eccentric cam whose center is offset from the axis of the camshaft.

Regarding the input member, the following configuration can be adopted.
(3) The input member is supported on the tip of the swing arm, and the base end of the swing arm is swingably supported by an axis parallel to the camshaft.
(4) A support member is fixed to the housing of the variable valve mechanism, and a guide surface for guiding the input member is provided on the support member.
(5) Use a rotating body for the input member.

Regarding the valve operating member, the following configuration can be adopted.
(6) Use a rocker arm that swings with the base end as a fulcrum for the valve member.
(7) Use a swing arm that swings around the intermediate portion as a fulcrum for the valve member.
(8) A valve lifter that can move linearly in the axial direction of the valve is used as the valve operating member.

The following configuration can be adopted for the transmission arm.
(9) Provided on the cam surface of the transmission arm are a base portion that keeps the momentum of the valve member zero, and a lift portion that gradually increases the momentum of the valve member, and the lift portion is closer to the base end side of the transmission arm than the base portion To form.
(10) The tip of the transmission arm is inserted between the valve member and the contact portion of the variable arm.
(11) The cam surface of the transmission arm is formed upward, and the drive portion of the transmission arm is provided downward.

The following configuration can be adopted as the variable arm driving method.
(12) The variable arm and the swing arm are supported on a common support shaft so as to be relatively rotatable. A control shaft different from the support shaft is connected to an actuator, and the variable arm is driven by the actuator via the control shaft. To do.
(13) A control cam is provided on the control shaft, and a swinging body that swings following the cam surface of the control cam is provided on the variable arm.
(14) A variable arm and a swing arm are supported on a common control shaft so as to be relatively rotatable, the control shaft is connected to an actuator, and the variable arm is driven by the actuator via the control shaft.

  According to the variable valve mechanism of the present invention, the base end of the transmission arm is connected to the input member that contacts the rotating cam, and the drive unit that drives the valve member on the distal end side of the transmission arm is engaged with the variable arm. Because the cam surface is provided, the power transmission path from the rotating cam to the valve operating member can be easily configured with very few parts, and it is possible to reduce the assembly error and stabilize the valve characteristics. Play. In addition, when the cam surface lift is formed closer to the base end of the transmission arm than the base, the arm ratio of the transmission arm is greater during high-speed rotation than during low-speed rotation. Output valve characteristics are obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the variable valve mechanism 1 of this embodiment drives a rotating cam 4 provided on a camshaft 2, an input roller 16 that contacts and displaces the rotating cam 4, and a valve 5. The rocker arm 6, a transmission arm 19 that transmits the power of the rotating cam 4 to the rocker arm 6, a variable arm 15 that includes a rotary contact 20 that contacts the transmission arm 19, and an actuator 13 that drives the variable arm 15. Yes.

  The proximal end of the transmission arm 19 is connected to the input roller 16, and a drive unit 22 that contacts the rocker arm 6 and a cam surface 21 that contacts the rotary contact 20 of the variable arm 15 are provided on the distal end side of the transmission arm 19. As the variable arm 15 moves, the initial contact position between the cam surface 21 and the rotary contact 20 is changed. As shown in FIG. 2, the cam surface 21 includes a base portion 21a that keeps the rocking amount of the rocker arm 6 at zero, and a lift portion 21b that gradually increases the rocking amount of the rocker arm 6. The lift portion 21b is transmitted more than the base portion 21a. It is formed on the base end side of the arm 19.

  1 to 6 show Embodiment 1 of the present invention. The variable valve mechanism 1 is used in an intake system of an automobile gasoline engine. However, the same mechanism can be applied to the exhaust system of a gasoline engine. As shown in FIGS. 1 to 3, the camshaft 2 of the variable valve mechanism 1 is provided above the cylinder head 3 and is rotated by a crankshaft (not shown) of the engine. A rotating cam 4 is fixed on the camshaft 2, and a rocker arm 6 that opens and closes a valve (intake valve) 5 is disposed below the camshaft 2.

  The rotating cam 4 is provided with an equal radius portion 4a that keeps the lift amount of the valve 5 at zero within a predetermined angle range and a nose portion 4b that increases the valve lift amount at the remaining angle range. The rocker arm 6 is supported by a pivot 7 on the base end side so as to be swingable up and down, has a pressing portion 8 that presses the upper end of the valve 5 at the tip, and a base roller 9 that receives the power of the rotating cam 4 in the middle. Yes. The variable valve mechanism 1 according to the first embodiment is configured such that one rotary cam 4 drives two rocker arms 6 to open and close two valves 5 per cylinder.

  Above the rocker arm 6, a control shaft 10 and a support shaft 11 are both provided in parallel with the camshaft 2. A control cam 12 whose center is deviated from the axis of the control shaft 10 is fixed on the control shaft 10. One end of the control shaft 10 is connected to a hydraulic or electric actuator 13, and the actuator 13 is controlled by a control device (not shown) according to the operating state of the engine. On the support shaft 11, one swing arm 14 and two variable arms 15 are supported so as to be relatively rotatable. An input roller 16 that contacts the rotating cam 4 is supported by a roller shaft 17 at the tip of the swing arm 14, and is displaced up and down according to the cam shape of the rotating cam 4.

  Two transmission arms 19 for transmitting the power of the rotating cam 4 to the rocker arm 6 are disposed on both sides of the swing arm 14. The transmission arm 19 is formed in a bowl shape, the base end is rotatably connected to both ends of the roller shaft 17, and the tip is inserted between the base roller 9 of the rocker arm 6 and the rotary contact 20 of the variable arm 15. Yes. On the distal end side of the transmission arm 19, an upward cam surface 21 with which the rotary contact 20 engages and a downward drive portion 22 that contacts the base roller 9 and drives the rocker arm 6 are provided. The cam surface 21 includes a base portion 21a that keeps the rocking amount of the rocker arm 6 at zero, and a lift portion 21b that gradually increases the rocking amount of the rocker arm 6. The lift portion 21b is closer to the base end side of the transmission arm 19 than the base portion 21a. Is formed.

  Then, the variable arm 15 is rotated by the actuator 13 via the control shaft 10 and the control cam 12, and the initial contact position between the rotary contact 20 and the cam surface 21 is changed as the variable arm 15 rotates. It has become. The variable arm 15 includes a recess 23 (see FIG. 3B) on the surface facing the control cam 12, and a shim 24 that contacts the cam surface (outer peripheral surface) of the control cam 12 is perpendicular to the axis of the control shaft 10. It is supported so as to be swingable around a specific axis. The drive portion 22 of the transmission arm 19 and the base portion 21 a of the cam surface 21 are both included in a cylindrical surface centered on the axis of the support shaft 11. FIG. 1 and FIG. 3A exemplify a configuration in which two transmission arms 19 are assembled to one swing arm 14, but the two transmission arms 19 are separated into two swing arms 14. It is also possible to assemble to.

  Next, the operation of the variable valve mechanism 1 will be described with reference to FIGS. FIG. 4 shows a state where the valve 5 is opened and closed with a minimum lift amount when the gasoline engine rotates at a low speed. At this time, as shown in FIG. 4A, the rotary contact 20 of the variable arm 15 is in contact with the start end side of the base portion 21a on the cam surface 21 of the transmission arm 19 (P is the initial contact position). Show). When the camshaft 2 is driven in this state, the cam portion of the base portion 21a swings during the period in which the constant radius portion 4a of the rotating cam 4 is engaged with the input roller 16 of the swing arm 14. The arm 14, the transmission arm 19 and the rocker arm 6 are stationary, and the valve 5 is held in the closed position.

  As shown in FIG. 4B, when the apex of the nose portion 4b of the rotating cam 4 is engaged with the input roller 16, the swing arm 14 swings downward, and the transmission arm 19 is displaced leftward. The lift part 21 b of the surface 21 contacts the rotary contact 20, and the drive part 22 pushes down the rocker arm 6 via the base roller 9. However, since the initial contact position P is set at the start end side of the base portion 21a, the operating range of the lift portion 21b is limited, and the rocker arm 6 swings at the minimum angle. Therefore, as shown by the curve (A) in FIG. 6, both the valve lift amount and the operating angle are minimized, and the opening timing of the intake valve 5 is controlled late and the closing timing is controlled early. The curve (e) in FIG. 6 shows the lift amount and operating angle of the exhaust valve.

  FIG. 5 shows a state where the valve 5 is opened and closed with the maximum lift amount when the gasoline engine rotates at high speed. Here, as shown in FIG. 5A, the variable arm 15 is rotated around the axis of the support shaft 11 by the control cam 12, and the initial contact position P between the rotary contact 20 and the cam surface 21 is the base portion 21a. The end has been changed. At this time, since the drive portion 22 and the base portion 21a of the transmission arm 19 are included in the cylindrical surface concentric with the support shaft 11, the initial phase of the rocker arm 6 does not change as the variable arm 15 rotates. . Therefore, during the period in which the equiradius 4a of the rotating cam 4 is engaged with the input roller 16, the swing arm 14, the transmission arm 19, and the rocker arm 6 are stationary, and the valve 5 is held in the closed position.

  As shown in FIG. 5B, when the apex of the nose portion 4b is engaged with the input roller 16, the transmission arm 19 is greatly displaced to the left, the lift portion 21b comes into contact with the rotary contact 20, and the drive portion 22 is engaged. Pushes down the rocker arm 6 via the base roller 9. At this time, since the initial contact position P is changed to the terminal end side of the base portion 21a, the operating range of the lift portion 21b is expanded and the rocker arm 6 swings at the maximum angle. For this reason, as shown by the curve (b) in FIG. 6, both the valve lift amount and the operating angle are maximized, and the opening timing of the intake valve 5 is controlled earlier and the closing timing is controlled later. Therefore, by changing the initial contact position P between the rotary contact 20 and the cam surface 21 by the variable arm 15, the valve characteristic is controlled to an arbitrary intermediate value as shown by the curves (c) and (d) in FIG. can do.

According to the variable valve mechanism 1 of the first embodiment, the following operations and effects can be obtained.
(1) Since the base end of the transmission arm 19 is connected to the input roller 16 that contacts the rotating cam 4, and the cam surface 21 and the drive unit 22 are provided on the distal end side of the transmitting arm 19, the rotating cam 4 moves to the rocker arm 6. The power transmission path can be easily configured with two parts of the input roller 16 and the transmission arm 19.
(2) Since the lift portion 21b of the cam surface 21 is formed closer to the base end side of the transmission arm 19 than the base portion 21a, the arm ratio of the transmission arm 19 becomes larger at high speed rotation than at low speed rotation of the engine. (L1 / L2 in FIG. 4b <L3 / L4 in FIG. 5b). As a result, in the valve characteristics during high speed rotation (curve b in FIG. 6), the valve lift amount / working angle value is increased from the conventional value (curve f), and the valve is operated during a relatively long valve opening period (working angle width). 5 can be opened wide to obtain high output valve characteristics suitable for high speed operation.

(3) Since the swing arm 14 and the variable arm 15 are supported on the support shaft 11 so as to be relatively rotatable, the power of the control cam 12 is not transmitted to the swing arm 14. For this reason, the initial contact position P between the rotary contact 20 and the cam surface 21 can be accurately changed while the swing arm 14 and the transmission arm 19 are stationary.
(4) When the camshaft 2 rotates, the power of the rotating cam 4 acts on the support shaft 11 via the swing arm 14, but the control shaft 10 that is the drive shaft of the variable arm 15 is provided separately from the support shaft 11. Therefore, power transmission from the rotary cam 4 to the control shaft 10 is interrupted, and the variable arm 15 can be driven by the small and low output actuator 13.
(5) Since the control cam 12 is in contact with the shim 24 on the variable arm 15, the swinging of the shim 24 absorbs the dimensional error and assembly error of the drive system member, and rotates the variable arm 15 at an accurate angle. To stabilize the valve characteristics.

  7 to 9 show a second embodiment of the present invention. In the variable valve mechanism 31, the support shaft 11 and the control cam 12 are omitted from the valve mechanism 1 of the first embodiment, and the swing arm 14 and the variable arm 15 are supported on the control shaft 10 so as to be relatively rotatable. ing. In other words, the swing arm 14 is swingably supported on the control shaft 10, and the variable arm 15 is coupled to the control shaft 10 by the key 32 so as to be integrally rotatable. The control shaft 10 is connected to an actuator (not shown), and the variable arm 15 is rotated around the swing axis of the swing arm 14 via the control shaft 10 by the actuator. Other configurations are the same as those of the first embodiment.

  Therefore, the variable valve mechanism 31 of the second embodiment also operates in the same manner as the valve mechanism 1 of the first embodiment, and exhibits the same actions and effects. In addition, since the support shaft 11 and the control cam 12 are omitted, there is an advantage that the number of parts of the entire mechanism can be further reduced. FIG. 8 shows an operation when the valve lift amount is minimized, and FIG. 9 shows an operation when the valve lift amount is maximized.

  FIG. 10 shows a third embodiment of the present invention. The variable valve mechanism 41 is different from the variable valve mechanisms 1 and 31 of the first and second embodiments in the support structure of the variable arm 42 and the transmission arm 43. The variable arm 42 includes a ring portion 44 that is fitted on the control cam 12 on the control shaft 10 at the base end, and a rotary contact 46 that contacts the cam surface 45 of the transmission arm 43 and a guide ring 47 at the distal end. The rotary contact 46 is configured to move substantially horizontally between the camshaft 4 and the control shaft 10 as the control cam 12 rotates eccentrically. The transmission arm 43 has a base end coupled to the roller shaft 17 of the input roller 16, and an upward cam surface 45 with which the rotary contact 46 comes into contact with the distal end side, and a downward drive unit that engages with the base roller 9 of the rocker arm 6. 48 is provided.

  The cam surface 45 includes a base portion 45a that keeps the rocking amount of the rocker arm 6 at zero, and a lift portion 45b that gradually increases the rocking amount of the rocker arm 6, and the lift portion 45b is closer to the base end side of the transmission arm 43 than the base portion 45a. Is formed. The input roller 16 is supported by a support member 49 instead of the swing arm 14 of the first and second embodiments, and the support member 49 is fixed to a housing (not shown) of the variable valve mechanism 41. The support member 49 is provided with a first guide surface 51 that engages with the guide ring 50 on the roller shaft 17 and a second guide surface 52 that engages with the guide ring 47 on the variable arm 42. And the guide surfaces 51 and 52, the base part 45a of the cam surface 45, and the drive part 48 are formed so that it may be contained in the cylindrical surface of a different radius which each made the axis line correspond.

  According to the variable valve mechanism 41, the input roller 16 is supported by the support member 49 fixed to the housing, and therefore one movable part (the swing arm 14 of the first and second embodiments) is omitted from the variable valve mechanism 41. There are advantages you can do. Further, since the second guide surface 52 of the support member 49 guides the rotary contact 46 between the support member 49 and the cam surface 45, a part of the power of the rotary cam 4 is released from the support member 49 to the housing side, and is transferred to the control shaft 10. There is also an advantage that a small and low output hydraulic or electric device can be used for an actuator (not shown) by reducing the applied load. Other actions and effects are the same as those of the first embodiment.

It is a perspective view of the variable valve mechanism which shows Example 1 of this invention. FIG. 2 is a cross-sectional view of the variable valve mechanism according to the first embodiment when viewed from the left in FIG. 1. It is sectional drawing which shows the assembly structure of a rocking | swiveling arm, a variable arm, a transmission arm, and a rocker arm in the variable valve mechanism of Example 1. It is a mechanism figure which shows an effect | action when the valve lift amount is minimized in the variable valve mechanism of Embodiment 1. It is a mechanism figure which shows an effect | action when maximizing valve lift amount in the variable valve mechanism of Example 1. FIG. It is a characteristic view which shows the relationship between a valve lift amount and a working angle. It is sectional drawing of the variable valve mechanism which shows Example 2 of this invention. It is a mechanism figure which shows an effect | action when the valve lift amount is minimized in the variable valve mechanism of Example 2. It is a mechanism figure which shows an effect | action when maximizing valve lift amount in the variable valve mechanism of Example 2. FIG. It is sectional drawing of the variable valve mechanism which shows Example 3 of this invention. It is sectional drawing which shows the conventional variable valve mechanism.

Explanation of symbols

1 Variable valve mechanism (Example 1)
2 Camshaft 4 Rotating Cam 5 Valve 6 Rocker Arm 10 Control Shaft 11 Support Shaft 13 Actuator 14 Swing Arm 15 Variable Arm 16 Input Roller 15 Cam Surface 19 Transmission Arm 20 Rotating Contact 21 Cam Surface 21a Base Portion 21b Lift Portion 22 Drive Portion 31 Variable valve mechanism (Example 2)
41 Variable valve mechanism (Example 3)
42 variable arm 43 transmission arm 45 cam surface 45a base part 45b lift part 46 rotary contactor 48 drive part 49 support member

Claims (2)

  A rotating cam provided on the camshaft, an input member that contacts and displaces the rotating cam, a valve operating member that drives the valve, a transmission arm that transmits the power of the rotating cam to the valve operating member, and a contact with the transmission arm A variable arm provided with a contact portion and an actuator that drives the variable arm, the base end of the transmission arm is connected to the input member, and the drive unit that drives the valve member on the distal end side of the transmission arm, and the variable arm The variable valve mechanism is provided with a cam surface that comes into contact with the contact portion, and changes an initial contact position between the cam surface and the contact portion as the variable arm moves.   The cam surface includes a base portion that keeps the momentum of the valve member to zero, and a lift portion that gradually increases the momentum of the valve member, and the lift portion is formed closer to the base end side of the transmission arm than the base portion. The variable valve mechanism according to 1.

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