JPH04121403A - Valve timing variable mechanism - Google Patents

Abstract

PURPOSE:To absorb looseness in an engaging part so as to eliminate generation of hammering noise by energizing a first piston engaged with a cam shaft and a second piston engaged with a timing pulley in mutually separating direction by means of a looseness eliminating spring, while forming only one helical gear at one position in each of both pistons. CONSTITUTION:A cylindrical first piston 22 is provided on the outer side of a cylindrical connecting shaft 12 fixed on the top end of a cam shaft 10 by a bolt 14. An inner helical spline 24 is formed on the inner wall of the piston 22 to engage with the outer helical spline 16 of the connecting shaft 12. Also, a cylindrical second piston 28 is provided on the outer side of the first piston 22. A straight spline 30 is formed on the inner wall of the piston 28 to engage with the straight spline 26 of the first piston 22. Also, a cap shaped cover 34 is provided on the outer side of the second piston 28, and an inner helical spline 36 is formed on the inner wall thereof to engage with the outer helical spline 32 of the second piston 28. And a looseness eliminating spring 46 is provided between both piston 22, 28 in an oil pressure chamber 42.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a variable valve timing mechanism that performs variable control of the opening and closing timing of an intake valve and an exhaust valve of an engine.

[Description of Prior Art] Generally speaking, in order to ensure high output and improve fuel efficiency in automobile engines, the timing of opening and closing of intake and exhaust valves is changed depending on whether the engine is running at high speed or medium to low speed. Equipped with a variable valve timing mechanism.

The variable valve timing mechanism has inner helical teeth formed on a member fixed to a timing pulley, outer helical teeth formed on a member fixed to a camshaft, and a cylindrical valve that slides in the axial direction of the camshaft using hydraulic pressure or the like. Helical teeth that mesh with the outer helical teeth are formed on the inner peripheral surface of the piston, and helical teeth that mesh with the inner helical teeth are formed on the outer peripheral surface of the piston. With the above configuration, the piston is moved in the axial direction of the camshaft using hydraulic pressure or the like depending on the operating conditions, and the relative phase angle between the timing pulley and the camshaft is changed depending on the movement position of the piston, thereby controlling the intake valve. This changes the opening/closing timing between the exhaust valve and the exhaust valve.

This variable valve timing mechanism has the disadvantage that play occurs at each of the two meshing points, and this play causes a banging sound during piston operation, or makes the timing of opening and closing the intake and exhaust valves unstable. Ta.

As a solution to this drawback, for example, JP-A-61-2
No. 79713, etc. are provided. According to this prior art, a cylindrical piston in which opposite helical teeth are formed on the inner and outer walls is cut into two pieces along a plane perpendicular to the axial direction, and the two cut pistons are attached to an elastic member. The opposing spaces (width of the cutter) are connected to each other so as to be displaceable in the axial direction. Then, the inner helical teeth of each of the two pistons are engaged with the outer helical teeth of the member fixed to the camshaft, and the outer helical teeth of each of the two pistons are engaged with the inner helical teeth of the member fixed to the timing pulley. It was designed to mesh with the

Since these two pistons are biased in the direction of repelling each other by an elastic member, the gap between the piston and the camshaft is set to zero, and the gap between the piston and the timing pulley is reduced to zero. This eliminates rattling and prevents the occurrence of hitting sounds.

[Problems to be Solved by the Invention] However, in this conventional variable valve timing mechanism, helical teeth are formed in opposite directions on the inner and outer walls of the piston, so both helical teeth must be manufactured by machining. Not only that, but the manufacturing cost also increased.

In addition, in this conventional variable valve timing mechanism, manufacturing tolerances differ between the meshing points of the helical teeth formed on the inner and outer walls of the piston, so the play between the inner and outer meshing points is not the same. It won't happen. As a result, the stroke of the elastic member to remove backlash absorbs the smaller of the backlashes, but the backlash still remains at the area where the larger backlashes engage, making it impossible to prevent the occurrence of hitting sounds. .

[Object of the Invention] The present invention has been made in view of the above points, and aims to prevent the occurrence of hammering sounds even if the play errors at the two meshing points are different, and to reduce manufacturing costs. The present invention provides a variable valve timing mechanism as described above.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides inner helical teeth formed on the inner periphery of a timing pulley, outer helical teeth formed on the outer periphery of a shaft integrally fixed to a camshaft. , a piston that is slidable in the axial direction of the camshaft, one side meshing with the inner helical teeth of the timing pulley and the other side meshing with the outer helical teeth of the shaft, and one side of the piston in the sliding direction. and a return spring that biases the piston toward the hydraulic chamber, and the piston is displaced by the hydraulic pressure to displace the phase between the timing pulley and the camshaft. In the variable valve timing mechanism, the piston is composed of two members, a cylindrical first piston and a cylindrical second piston, which are slidable in the axial direction, and the first piston has an axis attached to its outer wall. straight teeth are formed parallel to the direction, and inner helical teeth are formed on the inner wall of the second piston to mesh with the outer helical teeth of the shaft, and straight teeth are formed on the inner wall of the second piston to mesh with the straight teeth of the first piston. Also, outer helical teeth are formed on the outer wall of the timing pulley to engage with the inner helical teeth of the timing pulley, and a backlash removing spring is provided between the first piston and the second piston to urge them apart from each other. It is.

[Function] The first piston that engages with the camshaft and the second piston that engages with the timing pulley are urged apart by the backlash removing spring.

Since only one helical tooth is formed on the first piston and the second piston, the rattling spring absorbs the rattling of the first piston and the second piston at their respective meshing parts, which reduces the hitting sound. It will not occur.

The first and second pistons have meshing teeth on both the inner and outer walls, but these teeth are not helical teeth in opposite directions, so one tooth can be machined without machining both teeth. It can be made by sintering.

[Example] Next, the present invention will be explained based on the drawings.

FIG. 1 is a cross-sectional view of one embodiment of a variable valve timing mechanism according to the present invention, and FIG. 2 is an exploded perspective view of FIG. 1.

A cylindrical connection shaft 12 is fixed by a bolt 14 to the tip of a camshaft 10 for opening and closing intake valves and exhaust valves. An outer helical spline 16 is formed on the outer wall of this cylindrical connection shaft 12. When the connecting shaft 12 is fixed to the camshaft 10 with the bolt 14, the flange 18 formed on the connecting shaft 12 prevents the timing pulley 2o from moving in the axial direction of the camshaft 10. Mounted around the perimeter. However, the timing pulley 20 is not fixed to the camshaft 1o or the connection shaft 12.

A cylindrical first piston 22 is provided on the outside of the connection shaft 12.
will be provided. An inner helical spline 24 is formed on the inner wall of the first piston 22, and by meshing the inner helical spline 24 with the outer helical spline 16 of the connecting shaft 12, the first piston 22 is moved to the outer side of the connecting shaft 12. is rotatably and axially movably mounted on the A straight spline 26 is formed on the outer periphery of the first piston 22.

A cylindrical second piston 2 is disposed outside the first piston 22.
8 is provided. A straight spline 30 is formed on the inner wall of the second piston 28, and this straight spline 30 meshes with the straight spline 26 of the first piston 22. As a result, the first piston 22 and the second piston 28 can be relatively displaced in the axial direction, but the relative phase angles of both of them about the axis do not change. An outer helical spline 32 is formed on the outer periphery of the second piston 28. Here, the outer helical spline 16 of the connection shaft 12 and the outer helical spline 32 of the second piston 28 are set in opposite directions.

A cap-shaped cover 34 is provided on the outside of the second piston 28 . An inner helical spline 36 is formed on the inner wall of the cylindrical portion of the cover 34. By meshing the outer helical spline 32 of the second piston 28 with the inner helical spline 36, the second piston 28 is attached to the cover 34 so as to be rotatable and axially movable. A flange 38 that extends outward from the opening of the cap-shaped cover 34 is integrally formed with the opening of the cap-shaped cover 34.
) and the timing pulley 20 are fixed with bolts 40.

An annular space is formed by the cover 34, the timing pulley 20, and the connecting shaft 12, and this annular space is divided into a hydraulic chamber 42 and an air chamber 44 by the first piston 22 and the second piston 28. be done. The camshaft 10 and the connecting shaft 12 are connected to this hydraulic chamber 42.
Hydraulic pressure is introduced through a hydraulic pressure introduction passage 45 formed through. Inside this hydraulic chamber 42, a first piston 22 is provided.
A backlash removing spring 46 is provided between the second piston 28 and the second piston 28 . This looseness removing spring 46 functions to bias the first piston 22 and the second piston 28 in a direction away from each other. On the other hand, within the air chamber 44, a return spring 48 is provided between the first piston 22 and the cover 34 for urging the first piston 22 toward the hydraulic chamber 42.

In the present invention configured as described above, the first piston 22 and the second piston 28 are urged in mutually opposite directions by the looseness removing spring 46. Since the first piston 22 and the second piston 28 are formed with only one helical tooth meshing location, the first piston 22 is meshed with the connecting shaft 12 by the spring force of the backlash removing spring 46. The helical teeth of the first piston 22 and the second piston 28 are biased to eliminate play. No hitting sound is generated from the biting area.

Next, from the state shown in FIG. 1, when hydraulic pressure is introduced into the hydraulic chamber 42 and the pressure inside the hydraulic chamber 42 becomes high, this hydraulic pressure causes the first piston 22 to resist the return spring 48. It is moved to the air chamber 44 side (pressure side in FIG. 1). At this time, the relative positions of the first piston 22 and the second piston 28 in the axial direction change and the overall length of the backlash removing spring 46 increases, but the effect of the backlash removing spring 46 on eliminating play at the two meshing points is It remains valid. In addition, the first piston 22 and the second piston 2
8 are engaged by straight splines 26.30, so the first piston 22 and the second piston 28
The mutual phase angles around the axis do not change.

When the first piston 22 moves in the axial direction due to the action of hydraulic pressure (assuming that the second piston 28 is in a fixed position and the first piston 22 moves relative to the second piston 28), the first piston 22 Since it is engaged with the second piston 28 through the helical spline 16.24, it moves parallel to the axis without changing the phase angle with respect to the axis. When the first piston 22 moves in parallel to the axis, the phase angle of the connecting shaft 12 (fixed to the camshaft 1o) that meshes with the first piston 22 changes with respect to the axis. As a result, the relative phase angle between the camshaft 10 and the timing pulley 20 changes.

Next, when the pressure in the hydraulic chamber 42 changes from a high state to a low state, the first piston 22 moves toward the hydraulic chamber 42 and moves forward about the axis of the connecting shaft 12 that engages with the first piston 22. The connecting shaft 12 is rotated in the opposite direction to return the relative phase angle of the connecting shaft 12 to the second piston 28 to its original position.

That is, the phase angle between the camshaft 10 and the timing pulley 2° axis is returned to its original state.

In this way, the relative phase angle between the camshaft 1o and the timing pulley 20 is changed by moving the piston due to changes in the oil pressure in the hydraulic chamber 42.

In the present invention, the members having meshing teeth on both the inner wall and the outer wall are the first piston 22 and the second piston 28. These first piston 22 and second piston 2
8 both have helical splines on the -blade side, but straight splines on the other side. That is, the inner wall and the outer wall do not have helical teeth in opposite directions. As a result, the teeth on the blade side of the first piston 22 and the second piston 28 can be made by molding, and the teeth on the other side can be made by machining. As a result, in the present invention, manufacturing costs can be reduced compared to the conventional method in which teeth on both sides must be machined.

Note that, as shown in FIGS. 3 and 4, the hydraulic chamber 50 may be provided on the tip side of the camshaft 10, and the air chamber 52 may be provided on the root side of the camshaft 1o. In this case, the first piston 54 and the second piston 56 have the same configuration, although the shape is different from that of the previous embodiment. That is, the first piston 54 has an inner helical spline 62 formed on its inner wall that engages with an outer helical spline 60 of the connecting shaft 58, and a straight spline 64 formed on its outer wall. The second piston 56 has a straight spline 66 formed on its inner wall that engages with the straight spline 64, and an outer helical spline 72 that engages with the inner helical spline 70 of the cover 68 on its outer wall.

In order to introduce hydraulic pressure into the hydraulic chamber 50, a hydraulic pressure introduction passage 76 is formed between the camshaft 10 and the bolt 74.

In the hydraulic chamber 50, a backlash removing spring 46 is provided that urges the first piston 54 and the second piston 56 to move in opposite directions. Further, a return spring 48 is provided in the air chamber 52 to urge the first piston 54 toward the hydraulic chamber 50 side.

As described above, the system shown in FIGS. 3 and 4 has the same mechanism as the embodiment described above, so that the relative phase angle between the camshaft 10 and the timing pulley 20 changes depending on the change in the oil pressure in the oil pressure chamber 50. can be changed. Further, since the first piston 54 and the second piston 56 do not have helical teeth in opposite directions on the inner and outer walls, the teeth on one side can be made by molding, and the teeth on the other side can be made by machining.

[Effects of the Invention] As described above, according to the variable valve timing mechanism according to the present invention, only one helical tooth is formed on each of the two pistons, so that play in the meshing portion of each helical tooth is reduced. can be absorbed and can prevent the occurrence of hitting sounds.

Furthermore, in a member that has interlocking points on both the inner and outer walls, since it is not equipped with oppositely oriented helical teeth, it is possible to make the teeth on one side by molding, and the inner and outer teeth can be made by molding. Compared to the conventional method in which both are manufactured by processing, manufacturing costs can be reduced.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the variable valve timing mechanism according to the present invention, FIG. 2 is an exploded perspective view of FIG. 1, and FIG. 3 is another embodiment of the variable valve timing mechanism according to the present invention. FIG. 4 is an exploded perspective view of FIG. 3. 10...Camshaft, 16...Outer helical spline, 20.
...Timing pulley, 22...First piston, 24...Inner helical spline, 26.
...Straight spline, 32...Outer helical spline, 36...Inner helical spline, 42...Hydraulic chamber, 46...Backlash removal spring , 48...
・Return spring.

Claims (1)

[Claims] Inner helical teeth formed on the inner periphery of the timing pulley and outer helical teeth formed on the outer periphery of a shaft integrally fixed to the camshaft are slidable in the axial direction of the camshaft, one of which is attached to the timing pulley. a piston that meshes with the inner helical teeth of the shaft and the other side that meshes with the outer helical teeth of the shaft, a hydraulic chamber formed on one side of the piston in the sliding direction, and a return spring that biases the piston toward the hydraulic chamber side. In the variable valve timing mechanism, the piston is displaced by hydraulic pressure to displace the phase between the timing pulley and the camshaft. The first piston is composed of two members, a first piston and a cylindrical second piston, and the first piston has straight teeth parallel to the axial direction formed on its outer wall, and meshes with the outer helical teeth of the shaft on its inner wall. Inner helical teeth are formed on the second piston, and straight teeth are formed on the inner wall of the second piston to mesh with the straight teeth of the first piston, and outer helical teeth are formed on the outer wall of the second piston to mesh with the inner helical teeth of the timing pulley. A variable valve mechanism characterized by comprising a playback spring between a first piston and a second piston that urges them apart from each other.