JPH09280014A - Valve system cam shaft structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a valve system cam shaft structure which can improve its strength even if it is compact. SOLUTION: In a valve system cam shaft structure which is provided with a cam shaft 1 and a bolt 5 which is screwed in the cam shaft 1 in its axial direction and forms an oil passage B on a delay angle side and an oil passage A on an advance angle side of valve timing therein, an oil hole 35 is provided along its axis, a small diameter section 5c is provided at a tip of the bolt 5 in correspondence to the oil hole 35, and a space between the small diameter section 5c and an inner wall of the oil hole 35 of the cam shaft 1 is formed as the oil passage B on one side. An intermediate hole 37 is provided along an axis of the bolt 5 in the central part of the bolt 5 to form the intermediate hole 37 as the oil passage A on the other side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camshaft structure of a valve mechanism adopted in, for example, a motorcycle, and more particularly to a valve camshaft forming a part of a control hydraulic circuit of a VVT (variable valve timing mechanism). It is about structure.

[0002]

2. Description of the Related Art Generally, a valve operating structure is a structure in which the rotation of a crankshaft is transmitted to a camshaft via a belt or the like, and a cam fixed to the camshaft synchronizes the intake valve and the exhaust valve with the rotation of the crankshaft. A mechanism that opens and closes.

The variable valve timing mechanism is a mechanism that changes the timing of synchronization by changing the relative rotational angle position between the camshaft and the belt by hydraulic pressure.
This mechanism controls the opening / closing timing of the intake valve and the exhaust valve according to the load and the operating state for optimal combustion, air-fuel ratio control, exhaust gas emission, and the like.

The valve operating camshaft structure according to the present invention means the structure of the camshaft portion of the variable valve timing mechanism.

As a valve camshaft structure, which has not been published yet, the applicant of the present application previously created a structure as shown in FIG. In the figure, (A) is a cross-sectional view taken along the cam shaft, (B) is a partial cross-sectional perspective view, and (C) is X- of (A).
It is X sectional drawing.

The valve operating camshaft structure 35 shown in FIG.
A cam shaft 36 and a bolt 37 screwed in the cam shaft 36 in the axial direction thereof are provided. The bolt 37
A first oil hole 38 is provided along the axis of the cam shaft 36 on the tip end side of the cam shaft 36. The camshaft 36 around the bolt 37 is provided with a second oil hole 39 along the axis of the bolt 37. Three annular grooves 40, 41, 42 are provided around the cam shaft 36. Intermediate annular groove 41
Is communicated with the first oil hole 38 through the radial communication hole 71, and further communicates with the outer annular groove 42 through the radial communication hole 72, so as to communicate with the oil passage on the retarded side of the valve timing (arrow B). ) As. The inner annular groove 40 communicates with the second oil hole 39 through the radial communication hole 73 and is formed as a valve timing advance side oil passage (arrow A).

3 and 4 are a plan view and a side view showing the structure of a variable valve timing mechanism to which the valve operating camshaft structure 35 of FIG. 2 is applied.

In this case, the cylinder head 45 has a cam shaft 47 for opening and closing the two intake valves 46, 46.
And a camshaft 49 for opening and closing the two exhaust valves 48, 48 (FIG. 4). Both camshafts 47, 4
Pulleys 50 and 51 are coaxially mounted on the shaft 9 (see FIG. 4). Both camshafts 47 and 49 are pulleys 5
It is connected to a crankshaft (not shown) through 0 and 51 and a belt 52 that is commonly stretched around them. In this example, the valve operating camshaft structure 35 shown in FIG.
Is applied to the intake side camshaft 47.

A hydraulic control valve 53 is provided on the intake side camshaft 47 to control the hydraulic pressure supplied from an oil supply passage 55 formed in a cylinder block 54. That is, if hydraulic pressure is introduced into the advance side oil passage (arrow A) of the valve operating camshaft structure 35 via the hydraulic control valve 53, the timing of opening the intake valves 46, 46 will advance, and If it is introduced into the retard oil passage (arrow B), the timing of opening the intake valves 46, 46 will be delayed, and the valve timing control will be performed accordingly.

This will be described in more detail with reference to FIGS. FIG. 5 shows the oil flow when advancing, and FIG. 6 shows the oil flow when retarding. In each figure, (A) is a plane configuration,
(B) shows an elevation structure. The hydraulic control valve 53 is provided with an oil supply hole 56, an advance hole 57, a retard hole 58, an advance drain hole 59, and a retard drain hole 60, as shown in FIGS. 5 and 6. To be Further, the cylinder head 45 has
A first common hole 61 communicating with the advance hole 57 and also serving as an oil return hole at the time of retarding, and a second common hole 62 communicating with the retarding hole 58 and also serving as an oil return hole at the time of advancing are provided. . Further, the pulley 50 (FIG. 4) on the intake-side camshaft 47 is provided with an inner cylinder 64, a middle cylinder 65, and an outer cylinder 66 concentrically inside the case 63 (FIG. 3). The space between the cylinder 66 and the middle cylinder 65 is divided by a flange 67 of the middle cylinder 65 into an oil chamber 68 on the retard side and an oil chamber 69 on the advance side. In this case, the protrusion 80 on the inner surface of the middle cylinder 65 is fitted into the spline groove (not shown) formed in the outer surface of the inner cylinder 64 in the axial direction, and the protrusion 81 on the outer surface of the middle cylinder 65 corresponds to the inner surface of the outer cylinder 66. The structure fits in a spiral groove (not shown) formed in the axial direction.
The outer cylinder 66 has a structure integrated with the cam shaft 47. Therefore, according to the variable valve timing mechanism having the above configuration, the hydraulic pressure from the oil supply passage 55 (FIG. 4) is reduced to that in FIG.
When the oil pressure is introduced into the advance hole 57 through the oil supply hole 56 of the hydraulic control valve 53 as indicated by the black arrow, the hydraulic pressure is transmitted through the first common hole 61 of the cylinder head 45 to the valve camshaft structure. 35 is introduced into the oil chamber 69 on the advance side through the advance-side oil passage (arrow A) of 35, and the middle cylinder 65 linearly moves along the axis toward the intake valve 46 via the spline groove. The outer cylinder 66 rotates through the spiral groove. Therefore, the cam shaft 47 integrated with the outer cylinder 66 rotates in a direction that advances the valve opening timing of the intake valves 46, 46. At this time, the oil pushed out from the oil chamber 68 on the retard angle side by the movement of the middle cylinder 65 flows through the second common hole 62 of the cylinder head 45 to the oil of the hydraulic control valve 53 as shown by the white arrow in FIG. It is returned from the drain hole 59 to the outside. On the other hand, FIG.
Indicates the flow of oil for timing control to the retard side. In this case, it is introduced into the retard angle hole 58 via the oil supply hole 56 of the hydraulic control valve 53 as shown by the black arrow in FIG. This hydraulic pressure is introduced into the oil chamber 68 (FIG. 3) on the retard side through the second common hole 62 of the cylinder head 45, the oil passage on the retard side (arrow B) of the valve camshaft structure, and the middle cylinder 65. Moves linearly along the axis in a direction away from the intake valve 46 via the spline groove, and accordingly, the outer cylinder 66 rotates via the spiral groove in the direction opposite to the advance direction. Therefore, the outer cylinder 66
The cam shaft 47, which is integral with the rotary shaft, rotates in a direction that delays the opening timing of the intake valves 46, 46. At this time, the oil pushed out from the oil chamber 69 on the advance side by the movement of the middle cylinder 65 is discharged from the drain hole 60 of the hydraulic control valve 53 via the first common hole 61 as shown by the white arrow in FIG. It is released to the outside. In this way, the valve timing control is performed.

[0011]

However, in the above-mentioned conventional valve camshaft structure, an oil hole is bored in the center of the camshaft, and an oil passage or a retard angle side is further provided outside the oil hole in the center. With a structure that forms oil holes that form the side oil passages, it is difficult to improve the strength, and in order to increase the strength, the diameter must be increased,
It was also difficult to miniaturize.

Further, in order to make the diameter as small as possible, if the oil holes are formed obliquely as shown in FIG. 2, a dedicated processing machine is required, which complicates the structure and complicates the processing work.

The present invention has been made in view of the above-mentioned problems of the valve operating camshaft structure, and provides a valve operating camshaft structure capable of improving the strength even if it is downsized and easily processed. The purpose is to

[0014]

To achieve the above object, in the present invention, a camshaft and a bolt screwed in the camshaft in the axial direction thereof are provided, in which the valve timing retard side is provided. In a valve operating camshaft structure that forms an oil passage and an oil passage on the advance side, an oil hole is provided along the axis of the camshaft on the tip side of the screw part of the bolt, and the oil hole is formed corresponding to the oil hole. A small-diameter portion is provided at the tip of the bolt, and a space between the small-diameter portion and the inner wall of the oil hole of the camshaft is formed as the one oil passage. A valve operating camshaft structure, characterized in that a bore is provided along the bore, and the bore is formed as the other oil passage.

In a preferred embodiment, three annular grooves are provided on the peripheral surface of the camshaft, the first annular groove communicates with the inner hole, and the second and third annular grooves communicate with the space. It is characterized by that.

In another preferred embodiment, the camshaft is characterized in that it has radial communication holes for communicating the respective annular grooves with the oil hole and the intermediate hole, respectively.

[0017]

The oil hole having the same diameter as or smaller than the hole into which the bolt is screwed is formed at the center of the camshaft, and the bolt has a small diameter portion inserted into the oil hole at its tip. However, a middle hole is formed in the center of this small diameter part, and either the advance side oil passage or the retard side oil passage passes through the middle hole formed in this small diameter part, and the other is this small diameter part. Through the space between the outside of the section and the camshaft.

[0018]

1 is an explanatory diagram showing the basic configuration of the present invention.

A bolt 5 is screwed into the camshaft 1 in the axial direction thereof, and an oil hole 35 having a diameter substantially the same as that of the screw hole is formed along the axis of the bolt 5 at the tip end side of the screw portion 5b of the bolt 5. It An oil hole 9 having a smaller diameter than the oil hole 35 is provided on the tip side of the oil hole 35.
1 is provided. On the other hand, in the bolt 5, a small diameter portion 5c corresponding to the oil hole 35 is provided on the tip end side of the screw portion 5b. The bolt 5 including the small diameter portion 5c is provided with a through hole 37 extending through the bolt along the central axis thereof.
Three annular grooves 2, 3, 4 are provided on the circumferential surface of the camshaft 1. The first annular groove 2 communicates with a small-diameter oil hole 91 formed in the cam shaft at the tip of the bolt through a communication hole 36 in the radial direction, and further communicates with a middle hole 37 of the bolt 5. These first annular groove 2 → communication hole 36 → small diameter oil hole 91
The advance hole oil passage (arrow A) is formed by the hole 37 of the bolt. The second annular groove 3 has a radial communication hole 38.
Through the oil hole 35 on the outer periphery of the small diameter portion 5c of the bolt 5, and further through the radial communication hole 39 to the third annular groove 4. These second annular groove 3 → communication hole 38 → space between the inner wall surface of the oil hole 35 and the outer peripheral surface of the small-diameter portion 5c of the bolt 5 → communication hole 39 → the third annular groove 4 allows the oil on the retard side to be retarded. A passage (arrow B) is formed.

A sealing projection 5d is formed at the tip of the small diameter portion 5c of the bolt 5, and is pressed against the inner wall surface of the oil hole 35 of the camshaft 1 to separate the advance side passage and the retard side passage. .
In this case, a sealing material such as an O-ring may be provided on the outer peripheral surface of the protrusion 5d.

In this embodiment, as can be seen from the sectional view of FIG. 1D, an oil hole 35 is formed in the center of the camshaft 1, and a small diameter portion 5c at the tip of the bolt is formed in the oil hole. After inserting, a small hole 37 is formed at the center of the small diameter portion 5c. The middle hole 37 is used as one oil passage, and the space between the outer surface of the bolt small diameter portion 5c and the inner surface of the oil hole 35 is used as the other oil passage.

With such a structure, it is not necessary to provide an oil hole passage in the peripheral portion of the cam shaft in addition to the central oil hole of the cam shaft as in the structure shown in FIG. 2, and the strength of the cam shaft can be increased. In addition, the diameter of the shaft can be reduced, and the head portion can be downsized.

The valve camshaft structure of the above embodiment is incorporated in the variable valve timing mechanism (FIGS. 3 to 6) described above in place of the valve camshaft structure 35 (FIG. 2) described above, and valve timing control is performed. Used for.
The operation of the variable valve timing mechanism in this case is the same as that described above.

In the above embodiment, the bore 37 of the bolt 5 is used.
Is the advancing side oil passage and the space between the inner wall of the oil hole 35 of the camshaft 1 and the small-diameter portion 5c of the bolt 5 is the retarding side oil passage, but the reverse may also be true.

[0025]

As described above, in the present invention, one of the advancing side oil passage and the retarding side oil passage is provided at the center of the camshaft on the tip side of the threaded portion of the bolt. Since it is formed by the space between the inner wall of the bolt and the small diameter part of the bolt, and the other is formed by the bore of the bolt, one of the advance side oil passage and the retard side oil passage is connected to the camshaft outside the bolt. It is possible to improve the strength of the camshaft and to reduce the diameter of the camshaft to reduce the size of the cylinder head, as compared with the above-described valve camshaft structure before improvement.

Further, in the present invention, the oil hole of the cam shaft can be formed at the same time when the pilot hole of the screw hole of the bolt is formed, and in addition to the oil hole at the center of the cam shaft, the oil hole is further provided outside the oil hole. It is simpler in structure and manufacture than the above-described valve camshaft structure before improvement which needs to be disclosed.

[Brief description of drawings]

FIG. 1 is an explanatory view of a basic configuration of the present invention, (A) is a side sectional view, (B) is a cutaway perspective view, (C) is a sectional view taken along line XX of (A), and (D). ) Is a sectional view taken along line YY of FIG.

FIG. 2 is an explanatory view of the valve camshaft structure proposed previously, (A) is a side sectional view, (B) is a cutaway perspective view,
(C) is the XX sectional view taken on the line of (A) figure.

3 is a plan view of a variable valve timing mechanism to which the valve operating camshaft structure of FIG. 2 is applied.

4 is a side view of the variable valve timing mechanism of FIG.

5A and 5B are views for explaining the oil flow when the variable valve timing mechanism of FIGS. 3 and 4 is advanced, in which FIG.
(B) is a side view.

6A and 6B are views for explaining the oil flow when the variable valve timing mechanism of FIGS. 3 and 4 is retarded, in which FIG.
(B) is a side view.

[Explanation of symbols]

1: camshaft, 2, 3, 4: annular groove, 5: bolt,
5a: bolt head, 5b: screw part, 5c: small diameter part, 5d:
Sealing protrusion, 35: oil hole, 36, 38, 39: communication passage, 37: medium hole.

Claims (3)

[Claims] 1. A valve camshaft structure comprising a camshaft and a bolt screwed into the camshaft in an axial direction thereof, and forming an oil passage on the retard side and an oil passage on the advance side of the valve timing therein. In the camshaft on the tip side of the threaded portion of the bolt, an oil hole is provided along the axis,
A small-diameter portion is provided at the tip of the bolt corresponding to the oil hole, and a space between the small-diameter portion and the inner wall of the oil hole of the camshaft is formed as the one oil passage. A valve camshaft structure, characterized in that a central hole is provided in the center of the bolt along the axis thereof, and the central hole is formed as the other oil passage. 2. An annular groove is provided on the peripheral surface of the camshaft, wherein the first annular groove communicates with the inner hole and the second and third annular grooves communicate with the space. The valve operating camshaft structure according to claim 1. 3. The camshaft has a radial communication hole that communicates the first annular groove and the inner hole, and a radial communication hole that communicates the second and third annular grooves with the oil hole, respectively. The valve operating camshaft structure according to claim 2, wherein the valve operating camshaft structure has a communication hole.