JP2009108797A - Variable valve gear - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a variable valve gear having a torsion coil spring biasing a rocker arm in a return direction, capable of lessening spring force in the maximum deformation of the torsion coil spring and advantageous to miniaturization. <P>SOLUTION: The variable valve gear 10 is for varying an working angle of a valve 12 and includes the rocker arm 18 supported for rocking motion about a control shaft 16 and rocking with rotation of a cam 14, a variable mechanism varying a rocking range of the rocker arm 18 by rotating the control shaft 16 and the torsion coil spring 32 imparting moment of force to the rocker arm 18 in a direction of bringing the rocker arm 18 close to the cam 14. The variable valve gear is constructed so that concerning a change rate of a torsion angle of the torsion coil spring 32 to the change of a cam angle, the change rate of the torsion angle on a cam angle side in which valve lift is maximized is smaller than the change rate of the torsion angle on a cam angle side in which the valve lift becomes zero. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a variable valve operating apparatus used for an internal combustion engine.

  Japanese Patent Application Publication No. 2004-521235 discloses a valve drive device 1 having a gas exchange valve 4 that can be variably adjusted. In this device, the cam lever 5 provided with the rolling part 17 is a control track 19 of the rotating lever 21 that is operated by the cam shaft 3 against the action of the return spring 20, and includes an idling stroke curve 11 and a stroke curve. 18 cooperates with a control track 19 having. The rotation start position of the rotation lever 21 corresponding to each stroke variation can be set by being controlled / adjusted using the control device 25. In addition, said code | symbol is a code | symbol in the specification of the said gazette.

Special table 2004-521235 gazette

  In the valve drive device 1 described in the above publication, the return spring 20 that urges the turning lever 21 (corresponding to the swing arm of the present invention) in the return direction is constituted by a torsion coil spring. As shown in FIG. 1, the arm of the return spring 20 is extremely long. Since the valve drive device 1 uses the return spring 20 having such a long arm, there is a problem that the overall size increases.

  In order to reduce the overall size of the variable valve operating apparatus, it is necessary to reduce the torsion coil spring that urges the swing arm in the return direction, and to install the torsion coil spring close to the variable mechanism. For that purpose, it is necessary to use a torsion coil spring having a large spring constant, that is, a torsion coil spring having a small number of turns, a small average coil diameter, and a short arm. However, if a torsion coil spring with a large spring constant is used, the variation in shape and material (individual differences) tends to increase during mass production. (Individual difference) tends to increase. And in the individual | organism | solid with a large torsion angle at the time of a maximum deformation | transformation and a spring force, the allowable stress with respect to fatigue strength cannot be satisfied, but durability falls. For this reason, there is a demand to make the design median value of the spring force at the maximum deformation as small as possible.

  However, the spring force of the torsion coil spring must overcome the moment of force due to inertia acting on the swing arm or the like and apply a larger moment of force to the swing arm in the opposite direction. Since the torsion coil spring must be designed to satisfy this requirement, it is difficult to sufficiently reduce the design median value of the spring force at the maximum deformation.

  The present invention has been made to solve the above-described problems, and in a variable valve apparatus having a torsion coil spring that urges a swing arm in a return direction, the spring at the maximum deformation of the torsion coil spring is provided. It is an object of the present invention to provide a variable valve operating device that can reduce the force and is advantageous for downsizing.

In order to achieve the above object, a first invention is a variable valve gear,
A variable valve operating device for changing a valve operating angle of an internal combustion engine by rotating a control shaft,
A swing arm supported so as to be swingable about the control shaft, interposed between a cam for driving the valve and the valve, and swinging as the cam rotates;
A variable mechanism for changing the swing range of the swing arm by rotating the control shaft;
A torsion coil spring that applies a moment of force to the swing arm in a direction to bring the swing arm closer to the cam;
With
Regarding the rate of change of the torsion angle of the torsion coil spring with respect to the change of the cam angle, the rate of change of the torsion angle on the cam angle side where the valve lift becomes maximum is the rate of change of the torsion angle on the cam angle side where the valve lift becomes zero. It is configured to be small.

The second invention is the first invention, wherein
The cam angle when the moment of force due to inertia acting on the swing arm and the member swinging along with the swing arm is at a position deviated from the cam angle when the valve lift is maximum. And

The third invention is the second invention, wherein
In the maximum operating angle state, the amount of change in the torsion angle of the torsion coil spring from the cam angle when the valve lift becomes zero to the cam angle when the moment of force due to the inertia becomes the maximum is the inertia. The amount of change in the torsion angle of the torsion coil spring is larger than the cam angle at which the moment of force due to the maximum is the cam angle at which the valve lift is maximum.

Moreover, 4th invention is 2nd or 3rd invention,
The torsion coil spring has a coil and an arm formed on one end side of the coil, and is arranged so that the center of the coil is parallel to the center of the control shaft,
The arm portion presses a spring receiving portion provided on the swing arm,
In the maximum operating angle state, the contact at the contact point between the arm and the spring receiving portion between the cam angle when the moment of force due to the inertia is maximum and the cam angle when the valve lift is maximum. An angle formed by an arm direction and a line segment connecting the contact point and the control axis center is in a range of 100 ° to 110 °.

According to a fifth invention, in any one of the first to fourth inventions,
The direction of the arm in the portion in contact with the spring receiving portion on the cam angle side where the valve lift is maximum in the maximum working angle state is bent with respect to the direction of the arm in the portion closer to the base end. It is characterized by.

  According to the first aspect of the invention, regarding the rate of change of the torsion angle of the torsion coil spring with respect to the change of the cam angle, the rate of change of the torsion angle on the cam angle side where the valve lift becomes maximum is the cam angle side where the valve lift becomes zero. It is comprised so that it may become smaller than the change rate of the twist angle in. For this reason, the moment of force generated by the torsion coil spring changes with a relatively steep slope on the cam angle side where the valve lift becomes zero, but on the cam angle side where the valve lift becomes maximum, the slope is gentle and changes. Few. Therefore, it is possible to sufficiently suppress the moment of force generated by the torsion coil spring from becoming unnecessarily large in the vicinity of the maximum valve lift cam angle. As a result, the work consumed for driving the cam can be reduced, and the thermal efficiency of the internal combustion engine can be improved. Furthermore, since the spring force at the maximum deformation of the torsion coil spring can be reduced as much as possible, the torsion coil spring can be made less fatigued, and the durability of the torsion coil spring can be improved. In addition, even if the variation in shape and material (individual differences) during mass production of torsion coil springs is relatively large, the spring force during maximum deformation of each mass-produced product is surely below the allowable stress (allowable stress relative to fatigue strength). Can be. For this reason, it is difficult to reduce variations in shape and material during mass production. Torsion coil springs with smaller and larger spring constants (small number of coil turns, small coil mean diameter, short arms, coil windings) It is possible to use a circular cross section, etc.), so that the entire variable valve operating apparatus can be designed compactly.

  According to the second aspect of the present invention, the variable motion has such a characteristic that the cam angle when the moment of force due to inertia acting on the swing member becomes maximum is shifted from the cam angle when the valve lift becomes maximum. In the valve device, the spring force at the maximum deformation of the torsion coil spring can be reduced more effectively.

  According to the third invention, the moment of force by the torsion coil spring changes with a relatively steep slope between the cam angle at which the valve lift becomes zero and the maximum inertia force cam angle, but the maximum inertia force cam Between the angle and the maximum valve lift cam angle, it is possible to show a characteristic that the inclination is gentle and the change is small. For this reason, the spring force at the maximum deformation of the torsion coil spring can be reduced more effectively.

  According to the fourth invention, under the predetermined condition, the angle formed by the direction of the arm at the contact point between the arm of the torsion coil spring and the spring receiving portion and the line segment connecting the contact point and the control axis center is determined. By setting it within the range of 100 ° to 110 °, the spring force at the maximum deformation of the torsion coil spring can be reduced more effectively.

  According to the fifth invention, even if the shape of the spring receiving portion is simple, the characteristics of the moment of force by the torsion coil spring can be adjusted appropriately, and the design of the spring receiving portion can be simplified. .

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a variable valve operating apparatus according to Embodiment 1 of the present invention. A variable valve operating apparatus 10 shown in FIG. 1 drives a valve 12 of an internal combustion engine. The valve 12 may be either an intake valve or an exhaust valve. The variable valve operating apparatus 10 includes a cam 14 provided on a cam shaft that is rotationally driven by a crankshaft of an internal combustion engine, and a control shaft 16 disposed in parallel with the camshaft. In this specification, with respect to the moving direction of the valve 12, the direction in which the lift of the valve 12 (hereinafter simply referred to as “valve lift”) increases (that is, the opening direction) is defined as the positive direction, and the direction in which the valve lift decreases (that is, Close direction) is the negative direction.

  Although not shown, the variable valve apparatus 10 has a control shaft drive mechanism that can rotate the control shaft 16 within a predetermined angle range. The configuration of the control shaft drive mechanism is not particularly limited. For example, the control shaft drive mechanism includes a worm wheel fixed to one end of the control shaft 16, a worm gear that meshes with the worm wheel, and a servo motor that rotationally drives the worm gear. be able to. In this case, the rotation position (rotation angle) of the control shaft 16 can be controlled by controlling the rotation direction and the rotation amount of the servo motor.

  Further, the variable valve operating apparatus 10 has a swing arm (swing cam arm) 18. The swing arm 18 is installed so as to swing (rotate) about the control shaft 16. A slider surface 20 is formed on the swing arm 18 on the side facing the cam 14. In this specification, regarding the rotation angle of the swing arm 18, the clockwise direction in FIG. 1 is defined as a positive direction and the counterclockwise direction is defined as a negative direction.

  An intermediate roller (intermediate member) 22 is disposed between the swing arm 18 and the cam 14. The intermediate roller 22 includes a first roller 22a and a second roller 22b having a smaller diameter than the first roller 22a. The first roller 22 a is in contact with the peripheral surface of the cam 14, and the second roller 22 b is in contact with the slider surface 20 of the swing arm 18. The first roller 22a and the second roller 22b are arranged coaxially and are rotatable independently of each other.

  The intermediate roller 22 is supported at the tip of the intermediate arm 24. A control member 26 is fixed to the control shaft 16. A base end portion of the intermediate arm 24 and the control member 26 are connected to each other via a connecting shaft 28 so as to be rotatable. As a result, the intermediate arm 24 is rotatable about the connecting shaft 28. With such a configuration, the intermediate roller 22 can be moved by rotating the control shaft 16. That is, when the control shaft 16 is rotated counterclockwise from the state shown in FIG. 1, the control member 26 is also rotated counterclockwise so that the intermediate roller 22 is pushed out by the intermediate arm 24. , Away from the control shaft 16. When the control shaft 16 is rotated clockwise from that state, the intermediate roller 22 approaches the control shaft 16.

  The slider surface 20 has a curved surface in which the distance from the center of the cam 14 gradually decreases from the distal end side of the swing arm 18 toward the center side of the control shaft 16. On the other hand, a swing cam surface 30 is formed on the swing arm 18 on the side opposite to the slider surface 20. The swing cam surface 30 is provided continuously from a non-acting surface (basic circle) formed so that the distance from the center of the control shaft 16 is constant, and from the non-acting surface, and from the center of the control shaft 16. The working surface is formed so as to gradually increase the distance.

  Such a swing arm 18 is urged counterclockwise in FIG. 1 by a torsion coil spring 32 having a function as a lost motion spring. The torsion coil spring 32 has a coil 34 and is arranged in a posture in which the center of the coil 34 is parallel to the center of the control shaft 16. An arm 36 is formed on one end side of the coil 34. A fixing portion 38 is formed on the other end side of the coil 34. The fixing part 38 is fixed to a stationary part (not shown).

  In the present embodiment, the arm 36 of the torsion coil spring 32 is formed so as to extend linearly in the tangential direction of one end of the coil 34. The arm 36 abuts on a spring receiving portion 40 formed to protrude from the rear end portion of the swing arm 18 and presses the spring receiving portion 40. Due to such a torsion coil spring 32, a moment of counterclockwise force in FIG. 1 acts on the swing arm 18. Due to this moment of force, the swing arm 18 is pressed against the second roller 22 b of the intermediate roller 22, and the first roller 22 a of the intermediate roller 22 is pressed against the cam 14.

  In the present embodiment, as shown in FIG. 1, the shape of the spring receiving portion 40 is composed of a combination of two arcs, an arc having a radius R1 and an arc having a radius R2. In the present invention, the shape of the spring receiving portion 40 is not limited to such a shape, and the number and position of arcs to be combined, the size of the radius R of each arc, or the like, or a curve other than the arc Can be used to make a suitable shape.

  The variable valve operating apparatus 10 further includes a rocker arm 42 that presses the valve shaft of the valve 12 in the lift direction. The rocker arm 42 is disposed below the swing arm 18 in FIG. The rocker arm 42 is provided with a rocker roller 44 that contacts the rocking cam surface 30. The rocker roller 44 is rotatably supported by a shaft 46 at an intermediate portion of the rocker arm 42. One end of the rocker arm 42 is in contact with the valve shaft end of the valve 12, and the other end of the rocker arm 42 is supported by a hydraulic lash adjuster 48. The valve 12 is urged in a closing direction, that is, a direction in which the rocker arm 42 is pushed up by a valve spring (not shown). The rocker roller 44 is pressed against the swing cam surface 30 of the swing arm 18 by this urging force and the hydraulic lash adjuster 48.

  In such a variable valve operating apparatus 10, when the cam 14 rotates, the cam lift of the cam 14 is transmitted to the swing arm 18 via the intermediate roller 22, so that the swing arm 18 swings. When the cam 14 is not lifted, that is, when the basic circle portion of the cam 14 is in contact with the first roller 22a, the rocker roller 44 is in contact with the non-operating surface of the swing cam surface 30. Thereby, the valve 12 is closed. When the cam 14 begins to lift and the swing arm 18 begins to rotate clockwise in FIG. 1, the contact point between the rocker roller 44 and the swing cam surface 30 (hereinafter referred to as “rocker roller contact point”) The swing cam surface 30 shifts from the non-operation surface to the operation surface. When the rocker roller contact moves to the working surface, the rocker arm 42 is pushed down and the valve 12 is opened.

  As will be described below, in this variable valve operating apparatus 10, the operating angle (and the maximum lift amount) of the valve 12 can be continuously changed by rotating the control shaft 16 and moving the intermediate roller 22. it can.

  FIG. 1 shows a state in which the intermediate roller 22 is located closest to the center of the control shaft 16. In this state, since the cam lift of the cam 14 is transmitted to the swing arm 18 at a position close to the center of the control shaft 16, the swing range (amplitude) of the swing arm 18 is increased. For this reason, the working angle of the valve 12 is increased. Further, as described above, the closer to the center of the control shaft 16, the smaller the distance between the slider surface 20 and the center of the cam 14. Therefore, the position of the swing arm 18 (hereinafter referred to as “swing start position”) when the cam 14 is not lifted is clockwise in FIG. 1 as the intermediate roller 22 approaches the center of the control shaft 16. Move to the side. For this reason, after the swing arm 18 starts swinging, the amount of rotation of the swing arm 18 required until the rocker roller contact moves to the non-operation surface, that is, until the valve 12 starts to lift, is the intermediate roller. The closer 22 is to the center of the control shaft 16, the smaller it becomes. This also increases the operating angle of the valve 12. 1 shows the maximum operating angle state in which the operating angle of the valve 12 is maximized in the variable valve apparatus 10 (FIGS. 4 and 5 described later also show the maximum operating angle state).

  On the other hand, as the intermediate roller 22 is further away from the center of the control shaft 16, the cam lift of the cam 14 is transmitted to the swing arm 18 at a position farther from the center of the control shaft 16. For this reason, the swing range (amplitude) of the swing arm 18 is reduced. Further, after the swing arm 18 starts swinging, the amount of rotation of the swing arm 18 required until the rocker roller contact moves to the non-operating surface increases as the intermediate roller 22 is farther from the center of the control shaft 16. . For this reason, the working angle of the valve 12 becomes smaller as the intermediate roller 22 is farther from the center of the control shaft 16.

  That is, in the variable valve apparatus 10, the working angle of the valve 12 decreases as the intermediate roller 22 moves toward the distal end side of the swing arm 18. Therefore, in the variable valve apparatus 10, the operating angle of the valve 12 can be continuously reduced as the rotational position of the control shaft 16 is displaced counterclockwise in FIG. The operating angle of the valve 12 can be continuously increased as the rotational position of the valve 12 is displaced clockwise in FIG.

  FIG. 2 is a diagram showing acceleration characteristics of the valve 12 when the valve 12 is opened and closed by the cam 14 rotating at a constant speed in the variable valve apparatus 10 of the present embodiment. The horizontal axis in FIG. 2 is the rotation angle of the cam 14 (hereinafter referred to as “cam angle”), and the vertical axis is the acceleration of the valve 12 (hereinafter simply referred to as “valve acceleration”) and the valve lift. The acceleration characteristics shown in FIG. 2 are those when the variable valve apparatus 10 is in the maximum operating angle state.

  In the variable valve operating apparatus 10 as shown in FIG. 1, when the cam profile of the cam 14 is designed with polynomial or polydyne, the valve acceleration is set to the minimum value (negative maximum value) as shown in FIG. The cam angle at this time may deviate (become inconsistent) from the cam angle at which the valve lift becomes maximum. That is, the valve acceleration takes a negative maximum value at the cam angle during the valve lift.

  The curve of the swing angular acceleration around the center of the control axis 16 of the swing arm 18 shows the same tendency as the curve of the valve acceleration shown in FIG. Therefore, in the variable valve apparatus 10, the cam angle when the swing angular acceleration of the swing arm 18 becomes a negative maximum value is the cam angle when the valve lift becomes maximum (hereinafter, “maximum valve lift cam angle”). Will say). That is, the swing angular acceleration of the swing arm 18 takes a negative maximum value at the cam angle during the valve lift.

  When the swing arm 18 swings, the intermediate roller 22 and the intermediate arm 24 swing with the swing arm 18. These parts that swing together are hereinafter collectively referred to as “swing parts”. When the swing component swings, a moment of force due to inertia acts on the swing component due to the swing angular acceleration and the inertial mass. On the other hand, as described above, the moment of force by the torsion coil spring 32 also acts on the swing component.

  FIG. 3 is a diagram showing the relationship between the moment of force due to the inertia of the swinging component, the moment of force due to the torsion coil spring 32, and the cam angle in the variable valve apparatus 10 of the present embodiment. In FIG. 3, the moment of force by the torsion coil spring 32 is shown as a solid line and a two-dot chain line, but the moment of force by the torsion coil spring 32 in this embodiment is the direction of the solid line. . Further, in FIG. 3, for the sake of easy understanding, the moment of force due to the inertia of the swinging component is shown inverted.

  The moment of force due to inertia acting on the swing component when the swing angular acceleration is negative (hereinafter simply referred to as “the moment of force due to the inertia of the swing component”) is greater than the moment of force due to the torsion coil spring 32. If it becomes larger, the cam 14 and the intermediate roller 22 may be separated, and the intermediate roller 22 and the swing arm 18 may be separated. Therefore, in order to prevent such a situation, it is necessary that the moment of force by the torsion coil spring 32 is always larger than the moment of force by the inertia of the swinging part. That is, as shown in FIG. 3, the curve of the moment of force due to the torsion coil spring 32 needs to be above the curve of the moment of force due to the inertia of the oscillating component at any cam angle.

  As described above, the swing angular acceleration of the swing component takes a negative maximum value at the cam angle deviated from the maximum valve lift cam angle. For this reason, as shown in FIG. 3, the moment of force due to the inertia of the swinging component becomes maximum at the cam angle deviated from the maximum valve lift cam angle.

  On the other hand, the deformation amount (torsion angle) of the torsion coil spring 32 increases as the swing arm 18 rotates clockwise in FIG. 1, that is, as the valve lift increases. For this reason, as shown in FIG. 3, at the maximum valve lift cam angle, the deformation amount of the torsion coil spring 32 is maximized, and the moment of force by the torsion coil spring 32 is also maximized.

  For this reason, in the variable valve apparatus 10, if the moment of force by the torsion coil spring 32 is made larger than the moment of force by the inertia of the swinging part over the entire cam angle, the maximum of the torsion coil spring 32 is reached. The spring force during deformation tends to increase. If the spring force at the time of maximum deformation of the torsion coil spring 32 is large, as described above, the torsion coil spring 32 is easily fatigued and it is difficult to ensure sufficient durability. There is a problem that it is difficult to use. In addition, since the cam 14 rotates against the urging force of the torsion coil spring 32, there is a problem that the work consumed to drive the cam 14 increases and the thermal efficiency of the internal combustion engine decreases.

  On the other hand, according to the variable valve apparatus 10 of the present embodiment, the spring force at the maximum deformation of the torsion coil spring 32 can be made as small as possible as described below.

  FIG. 4 is a diagram showing a state of the variable valve apparatus 10 of the present embodiment at a cam angle at which the moment of force due to the inertia of the swinging component is maximized (hereinafter referred to as “maximum inertial force cam angle”). is there. As shown in the figure, when the spring force exerted by the torsion coil spring 32 is Ps, the force Py acting on the swing arm 18 from the torsion coil spring 32 is Ps × cos α. However, α is orthogonal to the acting radius Ry of the spring force Ps (the line segment connecting the contact 50 between the arm 36 of the torsion coil spring 32 and the spring receiving portion 40 of the swing arm 18 and the center of the control shaft 16). It is a component in the direction of The moment M of the force by the torsion coil spring 32 can be obtained as the product of the force Py and the action radius Ry.

In FIG. 4, the direction of the arm 36 at the cam angle at which the valve lift is zero is indicated by a two-dot chain line. Therefore, the amount of change in the torsion angle of the torsion coil spring 32 from the cam angle at which the valve lift is zero to the maximum inertia force cam angle is represented by Δφ ₁ in FIG.

On the other hand, FIG. 5 is a diagram showing a state at the maximum valve lift cam angle (that is, a state where the nose of the cam 14 is in contact with the first roller 22a) in the variable valve apparatus 10 of the present embodiment. . In FIG. 5, the direction of the arm 36 at the maximum inertia force cam angle (that is, the direction of the arm 36 in FIG. 4) is indicated by a two-dot chain line. Therefore, the amount of change in the torsion angle of the torsion coil spring 32 from the maximum inertia force cam angle to the maximum valve lift cam angle is represented by Δφ ₂ in FIG.

As it can be seen by comparing the twist angle variation [Delta] [phi ₂ of the twist angle variation [Delta] [phi ₁ and Figure 5 in FIG. 4 described above, according to the variable valve apparatus 10, the cam angle valve lift is zero The torsion angle change amount Δφ ₂ between the maximum inertia force cam angle and the maximum valve lift cam angle can be made sufficiently smaller than the torsion angle change amount Δφ _{1 up} to the maximum inertia force cam angle.

  The relationship between the torsion angle of the torsion coil spring 32 and the cam angle in the variable valve apparatus 10 of the present embodiment as described above is as shown in FIG. That is, according to the variable valve apparatus 10, the rate of change of the torsion angle in the vicinity of the maximum valve lift cam angle with respect to the rate of change of the torsion angle of the torsion coil spring 32 with respect to the change of the cam angle (that is, the inclination of the graph of FIG. 6). Can be made smaller than the rate of change of the torsion angle in the vicinity of the cam angle at which the valve lift becomes zero.

  By making the characteristics of the rate of change of the torsional angle of the torsion coil spring 32 as shown in FIG. 6, the moment of force by the torsion coil spring 32 is from the cam angle at which the valve lift becomes zero to the maximum inertia force cam angle. 3 (A in FIG. 3) changes with a relatively steep slope, but between the maximum inertia force cam angle and the maximum valve lift cam angle (B in FIG. 3), the slope is gentle and changes. Less is. For this reason, according to the variable valve apparatus 10, it can fully suppress that the moment of the force by the torsion coil spring 32 becomes unnecessarily large in the vicinity of the maximum valve lift cam angle. As a result, the work consumed to drive the cam 14 can be reduced, and the thermal efficiency of the internal combustion engine can be improved. Furthermore, since the spring force at the time of maximum deformation of the torsion coil spring 32, that is, the spring force of the torsion coil spring 32 at the maximum valve lift cam angle can be reduced as much as possible, the torsion coil spring 32 is less likely to be fatigued. The durability of the torsion coil spring 32 can be improved. In addition, even when the torsion coil springs 32 have a relatively large variation in shape and material (individual differences) during mass production, the spring force at the time of maximum deformation of each mass-produced product is surely tolerable stress (allowable stress relative to fatigue strength). The following can be achieved. For this reason, it is difficult to reduce variations in shape and material during mass production, and the torsion coil spring 32 is smaller and has a large spring constant (the number of turns of the coil 34 is small, the average diameter of the coil 34 is small, the arm 36 is short, Since the coil 34 has a circular cross section, etc., the entire variable valve apparatus 10 can be designed in a compact manner.

  In order to make the moment of force by the torsion coil spring 32 as shown by the solid line in FIG. 3, the maximum inertia force cam angle shown in FIG. 4 to the maximum valve lift cam angle shown in FIG. The angle θ formed by the direction of the arm 36 of the torsion coil spring 32 and the line segment connecting the contact 50 between the arm 36 and the spring receiving portion 40 and the center of the control shaft 16 (that is, the action radius Ry) (FIG. 4 and FIG. 5) is preferably in the range of 100 ° to 110 °. When the angle θ between the maximum inertia force cam angle and the maximum valve lift cam angle becomes larger than 110 °, as shown by a two-dot chain line in FIG. 3, the torsion coil spring 32 at the maximum valve lift cam angle is used. It may be difficult to reduce the moment of force and spring force sufficiently. When the angle θ between the maximum inertia force cam angle and the maximum valve lift cam angle is smaller than 100 °, the angle between the arm 36 and the action radius Ry is close to 90 °. The efficiency with which the force is converted into the moment of force of the swing arm 18 may be reduced.

  Further, the change characteristic of the moment of force acting on the swing arm 18 by the torsion coil spring 32 can be adjusted by the shape of the spring receiving portion 40. In the present embodiment, as shown in FIG. 1, the shape of the spring receiving portion 40 is configured by a combination of two arcs of an arc having a radius R1 and an arc having a radius R2, and the relationship between the two radii is R1> R2. Yes. As the cam lift of the cam 14 increases (as the swinging arm 18 rotates clockwise in FIG. 1), the radius of the contact between the arm 36 and the spring receiving portion 40 increases from the arc of R1 having a larger radius. It is configured to shift to a small arc of R2. Thereby, the change characteristic of the moment of force as described above can be realized easily and reliably. In addition, the shape of the spring receiving portion 40 in the present embodiment is not limited to the shape combining two arcs, but may be a shape combining three or more arcs or a shape using a curve other than the arc. In this case, the shape of the spring receiving portion 40 is changed so that the contact point between the arm 36 and the spring receiving portion 40 shifts from a portion with a large curvature radius to a portion with a small curvature radius as the cam lift of the cam 14 increases. It is preferable to configure.

  In the first embodiment described above, the control shaft 16, the intermediate roller 22, the intermediate arm 24, the control member 26, and the control shaft drive mechanism correspond to the “variable mechanism” in the first invention.

  Further, in the present embodiment, the cam profile of the cam 14 is designed by polynomial or polydyne, and the valve acceleration has been described as taking a negative maximum value at a cam angle that deviates from the maximum valve lift cam angle. Sex is not limited to such cases. For example, even when the valve acceleration takes a negative maximum value at the maximum valve lift cam angle, the present invention can be preferably applied when the valve acceleration characteristics change in the middle of the valve lift. It is.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG. 7. The description will focus on the differences from the first embodiment described above, and the same matters will be simplified or described. Omitted. FIG. 7 is a diagram showing a variable valve operating apparatus according to the second embodiment of the present invention.

As shown in FIG. 1, the arm 36 ′ of the torsion coil spring 32 ′ in the variable valve apparatus 10 ′ of the present embodiment has a shape in which the distal end side portion 36 a is bent with respect to the proximal end side portion 36 b. Between the maximum inertia force cam angle and the maximum valve lift cam angle, the spring receiving portion 40 of the swing arm 18 contacts the tip side portion 36a of the arm 36 ′. At this time, an angle θ ₂ formed by the direction of the distal end side portion 36a and a line segment connecting the contact point 50 between the arm 36 ′ and the spring receiving portion 40 and the center of the control shaft 16 is within a range of 100 ° to 110 °. It is preferable that it exists in. Thereby, for the same reason as described in the first embodiment, the spring force at the maximum deformation of the torsion coil spring 32 ′ can be sufficiently reduced.

Further, during the period from the cam angle at which the valve lift becomes zero to the maximum inertia force cam angle, the spring receiving portion 40 of the swing arm 18 is in contact with the proximal end portion 36b of the arm 36 '. Therefore, between the cam angle at which the valve lift is zero and the maximum inertia force cam angle, the direction of the arm 36 ′, the contact point 50 between the arm 36 ′ and the spring receiving portion 40, and the center of the control shaft 16 are set. The angle θ ₁ formed with the connecting line segment can be made larger than that in the first embodiment. Therefore, according to the present embodiment, it is possible to increase the amount of change in the torsion angle of the torsion coil spring 32 ′ from the cam angle at which the valve lift becomes zero to the maximum inertia force cam angle. For this reason, in this embodiment, even if the shape of the spring receiving portion 40 is simple, the characteristics of the moment of force by the torsion coil spring 32 can be adjusted appropriately, and the design of the spring receiving portion 40 can be made. It can be simplified.

  The method for forming the bent portion as described above on the arm 36 ′ is not particularly limited, and can be formed by, for example, bending, cutting, pressing, or the like.

  Since this embodiment is the same as Embodiment 1 except for the above points, further description is omitted.

It is a figure which shows the variable valve apparatus of Embodiment 1 of this invention. It is a figure which shows the acceleration characteristic of the valve | bulb in the variable valve apparatus of Embodiment 1 of this invention. It is a figure which shows the relationship between the moment of force by the inertia of the rocking | swiveling component in the variable valve apparatus of Embodiment 1 of this invention, the moment of force by a torsion coil spring, and a cam angle. It is a figure which shows the state at the time of the cam angle from which the moment of force by the inertia of a rocking | swiveling component becomes the maximum in the variable valve apparatus of Embodiment 1 of this invention. In the variable valve operating apparatus according to the first embodiment of the present invention, the valve lift is at a maximum cam angle. It is the relationship between the twist angle of a torsion coil spring and the cam angle in the variable valve apparatus of Embodiment 1 of the present invention. It is a figure which shows the variable valve apparatus of Embodiment 2 of this invention.

Explanation of symbols

10, 10 'Variable valve gear 12 Valve 14 Cam 16 Control shaft 18 Oscillating arm 20 Slider surface 22 Intermediate roller 22a First roller 22b Second roller 24 Intermediate arm 26 Control member 28 Connecting shaft 30 Oscillating cam surfaces 32, 32 'Torsion coil spring 34 Coils 36, 36' Arm 36a Tip side portion 36b Base end side portion 38 Fixed portion 40 Spring receiving portion 42 Rocker arm 44 Rocker roller 46 Shaft 48 Hydraulic lash adjuster 50 Contact

Claims (5)

A variable valve operating device for changing a valve operating angle of an internal combustion engine by rotating a control shaft,
A swing arm supported so as to be swingable about the control shaft, interposed between a cam for driving the valve and the valve, and swinging as the cam rotates;
A variable mechanism for changing the swing range of the swing arm by rotating the control shaft;
A torsion coil spring that applies a moment of force to the swing arm in a direction to bring the swing arm closer to the cam;
With
Regarding the rate of change of the torsion angle of the torsion coil spring with respect to the change of the cam angle, the rate of change of the torsion angle on the cam angle side where the valve lift becomes maximum is the rate of change of the torsion angle on the cam angle side where the valve lift becomes zero. A variable valve operating device configured to be small.   The cam angle when the moment of force due to inertia acting on the swing arm and the member swinging along with the swing arm is at a position deviated from the cam angle when the valve lift is maximum. The variable valve operating apparatus according to claim 1.   In the maximum operating angle state, the amount of change in the torsion angle of the torsion coil spring from the cam angle when the valve lift becomes zero to the cam angle when the moment of force due to the inertia becomes the maximum is the inertia. 3. The allowable value according to claim 2, wherein the torsional angle of the torsion coil spring is larger than a change amount of the torsion coil spring between a cam angle at which the moment of force due to the maximum reaches a cam angle at which the valve lift becomes maximum. Variable valve device. The torsion coil spring has a coil and an arm formed on one end side of the coil, and is arranged so that the center of the coil is parallel to the center of the control shaft,
The arm portion presses a spring receiving portion provided on the swing arm,
In the maximum operating angle state, the contact at the contact point between the arm and the spring receiving portion between the cam angle when the moment of force due to the inertia is maximum and the cam angle when the valve lift is maximum. The variable valve operating apparatus according to claim 2 or 3, wherein an angle formed by an arm direction and a line segment connecting the contact point and the control axis center is in a range of 100 ° to 110 °.   The direction of the arm in the portion in contact with the spring receiving portion on the cam angle side where the valve lift is maximum in the maximum working angle state is bent with respect to the direction of the arm in the portion closer to the base end. The variable valve operating apparatus according to any one of claims 1 to 4, wherein:

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