JP4697011B2 - Variable valve mechanism - Google Patents

Description

  The present invention relates to a variable valve mechanism that varies a valve opening characteristic of a valve provided in a cylinder of an internal combustion engine.

  A variable valve timing mechanism (hereinafter referred to as a VVT mechanism) that can continuously change the valve timing (opening phase) of an intake valve or an exhaust valve of an internal combustion engine has been widely put into practical use. This VVT mechanism can continuously advance or retard the valve timing by providing a rotation mechanism using hydraulic pressure between the timing gear and the camshaft and changing the phase of the camshaft.

  Further, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2003-239712, a variable valve mechanism capable of continuously changing a valve lift amount and a working angle (valve opening period) has been developed. Some have been put into practical use. If this variable valve mechanism is applied to an intake valve of a spark ignition internal combustion engine, a so-called non-throttle operation in which the intake air amount is controlled without using the throttle valve becomes possible. According to the non-throttle operation, the pumping loss can be greatly reduced, so that the fuel efficiency can be improved.

JP 2003-239712 A JP 2002-371816 A JP 2004-108302 A Japanese Patent Laid-Open No. 7-63023

  In a conventional variable valve mechanism in which the lift amount is continuously variable, the valve timing is uniquely determined according to the lift amount. That is, the lift amount and the valve timing cannot be changed independently, and only the valve timing cannot be freely changed.

  However, in order to improve output and reduce exhaust emissions, it is necessary to change not only the lift amount but also the valve timing with a high degree of freedom according to the operating state. For this reason, in the past, when a variable valve mechanism that makes the lift amount continuously variable is mounted, a VVT mechanism that makes the valve timing variable is further mounted. As a result of mounting these two types of variable mechanisms, there have been problems such as a complicated and large structure, an increased number of parts, and an increased manufacturing cost.

  The present invention has been made to solve the above-described problems, and provides a variable valve mechanism that can change both the lift amount and the valve timing with a high degree of freedom with a simple structure. With the goal.

In order to achieve the above object, a first aspect of the present invention is a variable valve mechanism that is interposed between a valve provided in a cylinder of an internal combustion engine and a cam that drives the valve, and makes the valve opening characteristics variable. Because
An input unit for inputting a pressing force for opening the valve;
A swing arm having a pressing surface for pressing the input unit and swinging with rotation of the cam;
An intermediate member interposed between the cam and the swing arm and transmitting the pressing force of the cam to the swing arm;
An intermediate arm that supports the intermediate member and swings as the cam rotates;
A first variable mechanism that makes the swing center position of the intermediate arm variable;
A second variable mechanism that makes the swing center position of the swing arm variable independently of the swing center position of the intermediate arm;
It is characterized by providing.

The second invention is the first invention, wherein
The first variable mechanism has a first control shaft whose rotational position is controlled,
The intermediate arm is rotatably connected to the first control shaft such that a portion eccentric from the center of the first control shaft is a swing center.
The second variable mechanism is provided coaxially with the first control shaft, and has a second control shaft whose rotational position is controlled independently of the first control shaft,
The swing arm is pivotally connected to the second control shaft so that a position eccentric from the center of the second control shaft is a swing center.

The third invention is the first or second invention, wherein
When the swing center position of the swing arm is moved by the second variable mechanism, a contact point between the input unit and the pressing surface relatively moves on the pressing surface.

According to a fourth invention, in any one of the first to third inventions,
The swing arm has a pressed surface pressed against the intermediate member,
Among the changes in the lift amount and the valve timing associated with the movement of the swing arm position of the intermediate arm, the change in the lift amount is obtained by canceling the movement of the swing arm position of the swing arm. The shape of the pressing surface and the pressed surface is set.

  According to the first aspect, the swing center position of the intermediate arm and the swing center position of the swing arm can be independently changed. When the swing center position of the intermediate arm is moved, the intermediate member moves between the cam and the swing arm, so that both the lift amount and the valve timing change. When the swing center position of the swing arm is moved, the lift amount can be amplified or reduced. The variable valve mechanism according to the first aspect of the invention can be varied depending on the combination of the movement direction and movement amount of the swing center position of the intermediate arm and the movement direction and movement amount of the swing center position of the swing arm. The state can be taken. For this reason, both the lift amount and the valve timing can be made variable with a high degree of freedom.

  According to the second invention, the first variable mechanism and the second variable mechanism can be realized with a simple structure. Further, by arranging the first control shaft and the second control shaft coaxially, space can be saved and the size can be reduced.

  According to the third invention, the contact point between the input portion and the pressing surface relatively moves on the pressing surface with the movement of the swing center position of the swing arm. For this reason, a desired variable characteristic can be provided according to the shape of the pressing surface.

  According to the fourth aspect of the invention, it is possible to make the lift amount uniform by canceling the change in the lift amount among the changes in the lift amount and the valve timing accompanying the movement of the swing center position of the intermediate arm. That is, according to the fourth aspect of the invention, the valve timing can be made continuously variable while keeping the lift amount substantially constant. This eliminates the need for a so-called VVT mechanism that changes the phase of the camshaft, thereby simplifying the structure, reducing the size and weight, reducing the number of parts, and reducing the manufacturing cost.

Embodiment 1 FIG.
FIG. 1 is a side view showing a variable valve mechanism according to Embodiment 1 of the present invention. A variable valve mechanism 10 shown in FIG. 1 opens and closes a valve 12. The valve 12 is an intake valve or an exhaust valve of the internal combustion engine. The valve 12 is biased by a valve spring 14 in the valve closing direction (upward in the figure).

  The variable valve mechanism 10 has a rocker arm 16. One end of the rocker arm 16 is in contact with the end of the valve stem 18 of the valve 12. The other end of the rocker arm 16 is a fulcrum 20 supported by a cylinder head (not shown). The rocker arm 16 swings around the fulcrum 20. A rocker roller 22 is installed at the center of the rocker arm 16 so as to be smoothly rotatable. The fulcrum 20 may be supported via a hydraulic lash adjuster (not shown).

  The variable valve mechanism 10 transmits the pressing force of the cam 24 to the rocker roller 22. When the rocker roller 22 is pressed, the rocker arm 16 presses the valve stem 18 and the valve 12 is opened. The cam 24 rotates in the clockwise direction in the drawing in synchronization with the crankshaft of the internal combustion engine at half the speed of the crankshaft.

  An intermediate member 26 and a swing arm 28 are interposed between the cam 24 and the rocker roller 22. The pressing force of the cam 24 is transmitted to the rocker roller 22 via the intermediate member 26 and the swing arm 28. The swing arm 28 is formed with a curved pressing surface 30 that contacts and presses the rocker roller 22, and a curved pressed surface 32 that is pressed by the intermediate member 26. The base end portion of the swing arm 28 is rotatably connected to the second control shaft 38.

  The intermediate member 26 is a columnar member. The intermediate member 26 is fixed to the distal end portion of the intermediate arm 34. A base end portion of the intermediate arm 34 is connected to the first control shaft 36 so as to be rotatable. The intermediate member 26 may be provided with a rotatable roller at a portion that contacts the cam 24 or a portion that contacts the pressed surface 32.

  FIG. 2 is a perspective view showing the swing arm 28, the intermediate member 26, and the intermediate arm 34. As shown in FIG. 2, a pin hole 42 for inserting a pin 40 described later is formed at the proximal end portion of the intermediate arm 34. In the illustrated configuration, the intermediate member 26 is supported by two intermediate arms 34. Further, a pin hole 46 for inserting a pin 44 described later is formed at the base end portion of the swing arm 28.

  In the present embodiment, two valves 12 are installed side by side as intake valves or exhaust valves for each cylinder, and the two valves 12 are driven by a common cam 24. Further, the swing arm 28 is provided separately for the two valves 12. On the other hand, the intermediate member 26 shown in FIG. 2 is obtained by integrating the intermediate members 26 for the two valves 12. That is, the upper part and the lower part in FIG. 2 of the intermediate member 26 are in contact with separate swing arms 28, and the central part of the intermediate member 26 is in contact with the cam 24.

  FIG. 3 is a view showing the first control shaft 36 and the second control shaft 38 with the swing arm 28 and the intermediate arm 34 removed. As shown in FIG. 3, the second control shaft 38 is hollow, and the first control shaft 36 is coaxially inserted through the hollow portion. The first control shaft 36 is provided with a protruding portion 48 that protrudes in the radial direction. The protrusion 48 protrudes outside from an opening 50 formed in the second control shaft 38. A pin 40 is installed near the tip of the protrusion 48. By inserting the pin 40 into the pin hole 42 of the intermediate arm 34, the intermediate arm 34 is connected to the first control shaft 36. The intermediate arm 34 can rotate around the pin 40.

  The second control shaft 38 is also provided with a protruding portion 52 that protrudes in the radial direction. A pin 44 is installed near the tip of the protruding portion 52. When the pin 44 is inserted into the pin hole 46 of the swing arm 28, the swing arm 28 is connected to the second control shaft 38. The swing arm 28 can rotate around the pin 44.

  FIG. 3 shows portions of the first control shaft 36 and the second control shaft 38 corresponding to the two valves 12 of one cylinder. In this portion, two sets of projecting portions 52 corresponding to the two valves 12 are provided, and the swing arm 28 is connected to each set of projecting portions 52. A protrusion 48 of the first control shaft 36 is located between the two sets of protrusions 52. An intermediate arm 34 shown in FIG. 2 that supports the intermediate member 26 shared by the two valves 12 is connected to the protrusion 48.

  The first control shaft 36 and the second control shaft 38 can independently control their rotational positions. Each of the first control shaft 36 and the second control shaft 38 is provided with a drive mechanism (not shown) that enables such control of the rotational position. As the drive mechanism, for example, an electric motor as a drive source and a worm gear as a transmission mechanism can be used.

  As shown in FIG. 1, the position of the pin 40, which is the swing center of the intermediate arm 34, is at a position that is eccentric from the center of the first control shaft 36. Therefore, by changing the rotational position of the first control shaft 36, the swing center position of the intermediate arm 34 can be moved. By moving the swing center position of the intermediate arm 34, the position of the intermediate member 26 can be moved (see FIGS. 4 and 5).

  Further, the position of the pin 44 which is the swing center of the swing arm 28 is at a position eccentric from the center of the second control shaft 38. Therefore, by changing the rotational position of the second control shaft 38, the swing center position of the swing arm 28 can be moved. When the swing center position of the swing arm 28 is moved, the contact point between the rocker roller 22 and the pressing surface 30 relatively moves on the pressing surface 30 (see FIGS. 4 and 5).

  As described above, in the variable valve mechanism 1, not only the swing center position of the intermediate arm 34 is variable, but also the swing center position of the swing arm 28 is variable. Thus, the variable valve mechanism 1 can change not only the lift amount of the valve 12 but also the valve timing (valve opening phase) with a high degree of freedom.

  That is, in the conventional variable valve mechanism in which the lift amount is continuously variable, the valve timing cannot be changed while the lift amount is kept constant. On the other hand, in the variable valve mechanism 1 of the present embodiment, the valve timing can be changed while the lift amount is kept constant, as will be described below.

  In the state shown in FIG. 1, the rocker roller 22 is in contact with the approximate center of the pressing surface 30, and the intermediate member 26 is in contact with the approximate center of the pressed surface 32. The center of the cam 24, the center of the intermediate member 26, and the center of the rocker roller 22 are located on a substantially straight line in a side view. As a result, in this state, the displacement caused by the cam nose 54 of the cam 24 is transmitted to the rocker roller 22 almost as it is, so that the lift amount substantially the same as the height of the cam nose 54 is obtained. Such a state shown in FIG. 1 is hereinafter referred to as a “phase neutral / normal lift state”.

  Assuming that only the swing center position of the intermediate arm 34 is displaced counterclockwise in the drawing without moving the swing center position of the swing arm 28 from the phase neutral / normal lift state of FIG. 26 moves in the direction opposite to the rotation direction of the cam 24 and comes into contact with the cam crest 54 at an early timing. That is, the valve timing is advanced. Further, in this case, the contact point between the intermediate member 26 and the pressed surface 32 is farther from the swing center of the swing arm 28 than in the state shown in FIG. For this reason, the amplitude of the swing arm 28 is reduced, and as a result, the lift amount is reduced. Such a state is hereinafter referred to as a “phase advance angle / small lift state”.

  When the swing center position of the swing arm 28 is displaced clockwise in the drawing from the phase advance angle / small lift state, the state shown in FIG. 4 is obtained. In this state, the valve timing is advanced as in the phase advance angle / small lift state. Further, the rocker roller 22 is in contact with the tip side from the center of the swing arm 28. The distance between the pressing surface 30 and the pressed surface 32 increases in the portion closer to the distal end than the center of the swing arm 28 toward the distal end.

  When the cam crest 54 presses the swing arm 28 via the intermediate member 26 in the state shown in FIG. 4, the contact point P between the rocker roller 22 and the pressing surface 30 moves further toward the distal end of the swing arm 28. That is, in the process in which the valve 12 is lifted, the contact point P moves in the direction in which the distance between the pressing surface 30 and the pressed surface 32 increases. For this reason, the rocker roller 22 is displaced larger than the height of the cam crest 54. That is, in this state, the lift amount of the valve 12 is amplified more than in the phase advance angle / small lift state, and becomes almost the same lift amount as in the phase neutral / normal lift state of FIG. Such a state shown in FIG. 4 is referred to as a “phase advance angle / normal lift state”.

  On the other hand, if it is assumed that only the swing center position of the intermediate arm 34 is displaced in the clockwise direction in the drawing without moving the swing center position of the swing arm 28 from the phase neutral / normal lift state of FIG. The member 26 moves in the same direction as the rotation direction of the cam 24 and comes into contact with the cam crest 54 at a late timing. That is, the valve timing is retarded. In this case, the contact point between the intermediate member 26 and the pressed surface 32 is closer to the swing center of the swing arm 28 than in the state shown in FIG. For this reason, the amplitude of the swing arm 28 is increased, and as a result, the lift amount is increased. Such a state is hereinafter referred to as a “phase retardation / large lift state”.

  When the swing center position of the swing arm 28 is displaced counterclockwise in the figure from the phase retardation / high lift state, the state shown in FIG. 5 is obtained. In this state, the valve timing is retarded in the same manner as in the phase retardation / high lift state. Further, the rocker roller 22 is in contact with the base end side from the center of the swing arm 28. In the portion closer to the proximal end than the center of the swing arm 28, the distance between the pressing surface 30 and the pressed surface 32 becomes smaller toward the distal end side.

  When the cam crest 54 presses the swing arm 28 via the intermediate member 26 in the state shown in FIG. 5, the contact point P between the rocker roller 22 and the pressing surface 30 moves in the distal direction of the swing arm 28. That is, in the process in which the valve 12 is lifted, the contact point P moves in a direction in which the distance between the pressing surface 30 and the pressed surface 32 becomes smaller. For this reason, the rocker roller 22 is displaced smaller than the height of the cam crest 54. That is, in this state, the lift amount of the valve 12 is reduced more than that in the phase retardation / large lift state, and becomes substantially the same lift amount as in the phase neutral / normal lift state in FIG. Such a state shown in FIG. 5 is referred to as a “phase retardation / normal lift state”.

  As described above, according to the variable valve mechanism 1, the phase retardation / normal lift state shown in FIG. 5 is changed to the phase advance / normal lift state shown in FIG. 4 through the phase neutral / normal lift state shown in FIG. In the meantime, the valve timing can be continuously changed while keeping the lift amount constant. That is, according to the variable valve mechanism 1, only the valve timing of the valve opening characteristics of the valve 12 can be made variable. For this reason, it is not necessary to separately provide a so-called VVT mechanism for changing the phase of the camshaft. Therefore, it is possible to simplify the structure, reduce the size and weight, reduce the number of parts, and reduce the manufacturing cost.

  In addition to the five states described above, the variable valve mechanism 1 includes the movement direction and movement amount of the swing center position of the intermediate arm 34, and the movement direction and movement amount of the swing center position of the swing arm 28. Depending on how they are combined, various states can be taken. As a result, the lift amount and the valve timing can be made variable with a high degree of freedom.

  In the above-described first embodiment, the configuration in which the swing arm 28 indirectly presses the valve 12 via the rocker arm 16 has been described. However, in the present invention, there is no rocker arm 16 and the swing arm 28 presses the valve 12. It is good also as a structure which presses directly. In the present invention, the first control shaft 36 and the second control shaft 38 may not be coaxial.

  In the first embodiment described above, the rocker roller 22 is the “input section” in the first invention, and the first control shaft 36, the protruding section 48, and the pin 40 are the “first section” in the first invention. The second control shaft 38, the protruding portion 52, and the pin 44 correspond to the “second variable mechanism” in the first aspect of the invention.

It is a side view which shows the variable valve mechanism (phase neutral and normal lift state) of Embodiment 1 of this invention. It is a perspective view which shows a rocking | fluctuating arm, an intermediate member, and an intermediate arm. It is a figure which shows the 1st control axis and the 2nd control axis in the state where the swing arm and the intermediate arm were removed. It is a side view which shows the variable valve mechanism (phase advance angle and normal lift state) of Embodiment 1 of this invention. It is a side view which shows the variable valve mechanism (phase retardation / normal lift state) of Embodiment 1 of this invention.

Explanation of symbols

10 variable valve mechanism 12 valve 14 valve spring 16 rocker arm 20 fulcrum 22 rocker roller 24 cam 26 intermediate member 28 swinging arm 30 pressing surface 32 pressed surface 34 intermediate arm 36 first control shaft 38 second control shafts 40 and 44 Pin 54 cam mountain

Claims (4)

A variable valve mechanism that is interposed between a valve provided in a cylinder of an internal combustion engine and a cam that drives the valve, and varies a valve opening characteristic of the valve;
An input unit for inputting a pressing force for opening the valve;
A swing arm having a pressing surface for pressing the input unit and swinging with rotation of the cam;
An intermediate member interposed between the cam and the swing arm and transmitting the pressing force of the cam to the swing arm;
An intermediate arm that supports the intermediate member and swings as the cam rotates;
A first variable mechanism that makes the swing center position of the intermediate arm variable;
A second variable mechanism that makes the swing center position of the swing arm variable independently of the swing center position of the intermediate arm;
A variable valve mechanism comprising: The first variable mechanism has a first control shaft whose rotational position is controlled,
The intermediate arm is rotatably connected to the first control shaft such that a portion eccentric from the center of the first control shaft is a swing center.
The second variable mechanism is provided coaxially with the first control shaft, and has a second control shaft whose rotational position is controlled independently of the first control shaft,
The said rocking | fluctuation arm is rotatably connected with the said 2nd control shaft so that the location eccentric from the center of the said 2nd control shaft may become a rocking | fluctuation center. Variable valve mechanism.   The contact point between the input portion and the pressing surface relatively moves on the pressing surface when the swinging center position of the swinging arm is moved by the second variable mechanism. 3. The variable valve mechanism according to 1 or 2. The swing arm has a pressed surface pressed against the intermediate member,
Among the changes in the lift amount and the valve timing associated with the movement of the swing arm position of the intermediate arm, the change in the lift amount is obtained by canceling the movement of the swing arm position of the swing arm. The variable valve mechanism according to any one of claims 1 to 3, wherein shapes of the pressing surface and the pressed surface are set.

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