JP2005214177A - Supporting device for camshaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent uneven wear, abnormal wear, and seizure in a part rotatably supporting a camshaft. <P>SOLUTION: An rolling bearing 15 is provided around a sprocket 11 transmitting engine rotation to a camshaft 7, and the camshaft 7 is retained by a cylinder head 4 via the rolling bearing 15. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a camshaft support device.

Some engines incorporate a cam mechanism in which a camshaft is rotated in a cylinder head in synchronization with a crankshaft, thereby forcibly opening and closing a supply / exhaust valve via a rocker arm.
In this cam mechanism, synchronous rotation between the crankshaft and the camshaft is performed by winding an endless chain between sprockets provided at one end of each of the shafts on the same side. For this reason, the camshaft is subjected to the largest load at the sprocket portion due to the fact that the rotational driving force is transmitted to the sprocket.

The portion that supports the camshaft rotatably in the cylinder head has a structure in which two or more journal portions provided at predetermined intervals in the axial direction of the camshaft are supported in a surface contact state by a sliding bearing. (For example, refer to Patent Documents 1 to 3, etc.). Lubricating oil is supplied to the surface contact portion (sliding contact portion) between the camshaft and each sliding bearing together with the operating portion of the rocker arm and the like by an oil pump. This oil pump operates as the engine starts.
Recently, a structure has been proposed in which the sliding bearing is replaced with a rolling bearing, and the camshaft is supported at both ends by this rolling bearing.
JP-A-6-288296 JP 2000-28281A Japanese Patent No. 2500114

As described above, the oil pump for supplying lubricating oil to the surface contact portion (sliding contact portion) between the camshaft and each sliding bearing is operated by the engine. For this reason, when starting the engine or rotating at a low speed, the lubricating oil from the oil pump may not be sufficiently distributed to the surface contact portion. When this happens, uneven wear or abnormal wear occurs in the journal portion of the camshaft or the sliding bearing of the cylinder head, and there is a risk of seizure in severe cases.
These problems can be solved by replacing the sliding bearings with rolling bearings. To that end, however, it is necessary to make the structure of the cylinder head from the beginning so that the rolling bearings can be incorporated. It is not a measure against (incorporated). In addition, it was pointed out that the cost would be increased if the camshaft was supported at both ends by a rolling bearing.

The present invention has been made in view of the above circumstances, and provides a camshaft support device capable of preventing uneven wear, abnormal wear, and seizure in a portion that rotatably supports the camshaft. Objective.
In addition, the present invention can prevent uneven wear, abnormal wear, and seizure by simply adding a new member to an existing engine in which the camshaft support portion is a sliding bearing without requiring any improvement. An object of the present invention is to provide a camshaft support device.

In order to achieve the above object, the present invention has taken the following measures.
That is, in the camshaft support device according to the present invention, the camshaft is rotatably provided in the cylinder head, and a sprocket for engine rotation transmission is detachably provided at one end of the camshaft. A rolling bearing is provided around the boss portion of the sprocket, and the rolling bearing is supported with respect to the cylinder head.
In this way, the portion of the sprocket that is most heavily loaded in the axial direction with respect to the camshaft is held by the rolling bearing, so that the lubricating oil from the oil pump is temporarily removed when the engine is started or at low speed. Even if it does not spread sufficiently, it is possible to prevent the occurrence of uneven wear, abnormal wear, and seizure in other portions that support the camshaft.

The rolling bearing may be housed in an outer lid that can be fitted and removed with respect to a through-hole provided in the peripheral wall of the cylinder head and supported by the cylinder head via the outer lid. By doing so, the structure can be simplified and the cost problem can be avoided.
Such an outer lid may have a bearing case that houses the rolling bearing and a lid plate that covers the outer surface side of the bearing case.
In this case, the bearing case is formed as an oil receiving recess that receives the lubricating oil on the side covered with the cover plate, and an oil recovery port that communicates the inside of the oil receiving recess with the inside of the cylinder head is provided. Preferred.

When the outer lid has a structure having a bearing case and a lid plate, the shape and size of the portion where the bearing case is mounted to the through hole of the cylinder head, and the lid plate with respect to the oil receiving recess of the bearing case It is preferable that the shape and size of the portion to be mounted are formed to be the same.
In this way, the camshaft support device according to the present invention can be implemented by adding new members (bearing case and rolling bearing) without any improvement to the conventional camshaft support device. .

  In the camshaft support device according to the present invention, uneven wear, abnormal wear, and seizure can be prevented at a portion where the camshaft is rotatably supported. In addition, the present invention can prevent uneven wear, abnormal wear, and seizure even with an existing engine in which the camshaft support portion is a sliding bearing, by adding a new member without any improvement. Become.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 5 show an embodiment of a camshaft support device 1 according to the present invention. The support device 1 is implemented in a cam mechanism 5 provided inside a cylinder head 4 of an engine 3 mounted on a minibike 2 or the like.
In this cam mechanism 5, a camshaft 7 is provided so as to traverse the inside of the cylinder head 4, and this camshaft 7 slides a journal portion 8 provided at two or more locations in the axial direction with a sliding bearing. 9 so that it can rotate freely. In the illustrated example, the sliding bearing 9 is provided integrally with the cylinder head 4 by forming a circular hole through the inner wall 10 provided in the shape of a partition wall inside the cylinder head 4. ing. The journal portion 8 of the camshaft 7 is provided with an oil groove 8a for guiding lubricating oil in a spiral shape.

A sprocket 11 is rotatably provided at one end of the camshaft 7, and an endless chain 12 is wound around the sprocket 11 for synchronous rotation with a crankshaft (not shown). The sprocket 11 is detachable from the camshaft 7. In the illustrated example, the bolt 13 is inserted into a bolt hole 11a (see FIG. 4) provided through the sprocket 11 in the thickness direction, and is bolted to the shaft end of the camshaft 7.
The camshaft 7 is provided with a predetermined number of cams 14 depending on the number of cylinders of the engine, the difference between 2/4 cycles, or the difference in engine type such as DOHC or OHC. A supply / exhaust valve (not shown) is forcibly opened and closed.

As is clear from FIG. 2, in the support device 1 according to the present invention, a rolling bearing 15 is mounted around a sprocket 11 provided at one end of the camshaft 7, and the camshaft 7 is slippery. The rotation is held not only through the bearing 9 but also through the rolling bearing 15. The rolling bearing 15 is held by an outer lid 21 that is fitted to a through-hole 20 provided on the peripheral wall of the cylinder head 4. The outer lid 21 has a bearing case 16 and a lid plate 21a.
The bearing case 16 is formed with a housing part 16a having a ring shape that fits the through-hole 20 on the outer peripheral surface of the rolling bearing 15 while accommodating the rolling bearing 15 therein, and is formed to be slightly larger in diameter than the housing part 16a. And a rib portion 16b that can be engaged with an outer peripheral portion of the opening of the through hole 20. The inside of the rib portion 16b has a dish-like shape, and an oil receiving recess 25 for receiving lubricating oil that oozes out from the inner and outer surfaces of the rolling bearing 15 is formed by this recess. An oil recovery port 26 communicating with the cylinder head 4 is provided inside the oil receiving recess 25.

The lid plate 21a covers the outer surface side of the bearing case 16 (the oil receiving recess 25 described above). A screw boss 22 protrudes from the back surface of the lid plate 21a, and a tip end portion of a long bolt 23 inserted into the shaft center portion of the camshaft 7 in a skewered manner from the opposite side of the cylinder head 4 is screwed to the screw boss 22. It is supposed to be combined. Thereby, the lid plate 21a is pulled toward the cylinder head 4 by the neck long bolt 23, and the bearing case 16 is pressed against the cylinder head 16 by the lid plate 21a and fixed.
In the outer lid 21, the opening shape and inner diameter of the oil receiving recess 25 in the bearing case 16 and the opening shape and inner diameter of the through-hole 20 provided in the cylinder head 4 are formed to be the same. In other words, there is an advantage that the support device 1 according to the present invention can be implemented only by adding the bearing case 16 (of course, the one containing the bearing 15) to the conventional camshaft support device.

That is, even in the conventional camshaft support device, the peripheral wall of the cylinder head 4 is usually provided with a through-hole 20 in an arrangement corresponding to the sprocket 11, and the through-hole 20 has a cover for closing it. As described above, if the oil receiving recess 25 of the bearing case 16 and the through hole 20 of the cylinder head 4 have the same opening shape and inner diameter, the lid used for the outer lid 21 is provided. The plate 21a can be a common part with the cover used in the conventional camshaft support device.
After all, the cover that covers the through hole 20 is removed from the conventional camshaft support device, and the bearing case 16 that houses the rolling bearing 15 is fitted into the through hole 20, and then the original cover is attached. Thus, the support device 1 according to the present invention can be implemented easily.

In FIG. 2, in order to facilitate understanding of the oil recovery port 26, the oil recovery port 26 is drawn on the right side in FIG. 2, but in reality, the relationship with the mounting posture of the engine 3. Therefore, it is preferable to provide the cylinder head 4 at a downward position. For example, when the cylinder head 4 has a mounting posture with an inclination Q of 10 ° with respect to the perpendicular P as shown in FIG. 3, the oil recovery port 26 is positioned on the perpendicular P as shown in FIG. It is preferable to provide as described above.
The rolling bearing 15 is, for example, a ball bearing, and an inner ring body 15 a is externally fitted around a boss portion 29 provided on the sprocket 11 without a gap, and an outer ring body 15 b is disposed inside a housing 16 a provided on the bearing case 16. It is fitted without a gap.

In the support device 1 configured as described above, the portion of the sprocket 11 that is most loaded in the axial direction of the camshaft 7 is supported by the rolling bearing 15. Therefore, even when the lubricating oil from the oil pump does not spread sufficiently, such as when the engine 3 is started or when the engine 3 rotates at a low speed, local overcontact is caused by the journal portion 8 of the camshaft 7 or the sliding bearing 9 of the cylinder head 4. This prevents the occurrence of uneven wear or abnormal wear. Of course, there is no risk of burning.
According to the embodiment, for the purpose of reducing the wear resistance of the camshaft journal portion, the cam sprocket is provided with a journal so that it can be easily attached, and the radial ball bearing is disposed on the cylinder head left side cover portion. In addition, the load on the camshaft journal when the oil circulates and the oil pressure during low rotation is reduced can be reduced, and smooth idling and torque increase during low and medium speed rotation can be realized.

By the way, this invention is not limited to the said embodiment, It can change suitably according to embodiment. For example, in the outer lid 21, the bearing case 16 and the lid plate 21a can be integrally formed.
Needless to say, the present invention can be implemented not only when retrofitting (remodeling) an existing camshaft support device but also as a device that supports the sprocket 11 with the rolling bearing 15 from the initial design stage.
Various specifications of the engine and their uses (objects to be mounted) are not limited at all.

  Further, when a ceramic bearing is used as the “rolling bearing (15)” of the present invention, weight reduction can be achieved, which is more suitable for a high speed engine. The “sprocket (11)” in the present invention is not limited to a sprocket for a chain but includes a timing gear for a timing belt.

It is an AA arrow directional view of FIG. It is the figure which expanded the principal part (around a bearing case) of FIG. 1, and crushed and showed the part. It is the side view which expanded and showed the part (around a cylinder head) in which the support apparatus based on this invention is implemented with respect to the engine mounted in the minibike of FIG. FIG. 3 is a view taken along the line B-B in FIG. 2 (a view of the inside of the bearing case with the outer lid removed). It is a side view of a minibike.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Support apparatus 4 Cylinder head 7 Cam shaft 11 Sprocket 15 Rolling bearing 16 Bearing case 20 Through port 21 Outer cover 25 Oil receiving recessed part 26 Oil recovery port

Claims (5)

  A camshaft (7) is rotatably provided in the cylinder head (4), and an engine rotation transmission sprocket (11) is detachably provided at one end of the camshaft (7). A camshaft support characterized in that a rolling bearing (15) is provided around a boss portion (29) of the sprocket (11), and the rolling bearing (15) is supported with respect to the cylinder head (4). apparatus.   The rolling bearing (15) is housed in an outer lid (21) that is detachable from a through-hole (20) provided in the peripheral wall of the cylinder head (4). The camshaft support device according to claim 1, wherein the camshaft support device is supported by the cylinder head (4).   The outer lid (21) has a bearing case (16) that houses a rolling bearing (15), and a lid plate (21a) that covers the outer surface side of the bearing case (16). The camshaft support device according to claim 2.   In the bearing case (16), the side covered with the cover plate (21a) is formed as an oil receiving recess (25) for receiving lubricating oil, and the inside of the oil receiving recess (25) and the inside of the cylinder head (4) are formed. 4. The camshaft support device according to claim 3, further comprising an oil recovery port (26) communicating therewith.   The outer lid (21) has a shape and size of a portion where the bearing case (16) is attached to the through hole (20) of the cylinder head (4), and a lid plate (21a) serving as an oil for the bearing case (16). 4. The camshaft support device according to claim 3, wherein a shape and a size of a portion to be attached to the receiving recess (25) are the same.

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