JP3189594B2 - Bearing structure of camshaft in internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camshaft bearing structure for an internal combustion engine, and more particularly to a technique for preventing bearing noise.

[0002]

2. Description of the Related Art Conventionally, as shown in Japanese Patent Publication No. 55-9523 and Japanese Utility Model Laid-Open Publication No. Sho 59-16490, an overhead cam type internal combustion engine (hereinafter referred to as an engine) is provided with an intake valve and an exhaust valve. A pair of overhead camshafts for valves are provided, and a timing chain as a wrapping transmission band is wound around a cam sprocket as a cam transmission wheel fixedly mounted on each camshaft.

The receiving shafts set at a plurality of positions on the camshaft are supported by a plurality of bearings (journals).

[0004]

By the way, in such a camshaft bearing structure, generation of abnormal noise due to bearing hitting noise has conventionally been a problem. The mechanism of this abnormal noise generation will be described with reference to FIGS. The tension of the timing chain A is applied in the direction of the arrow a in FIG. 6, and the cam bearing shaft C supported by the journal B by the chain tension is applied to the cylinder head side support D of the journal B as shown by the arrow b in FIG. Depressed. At the time of valve lift, the cam bearing shaft portion C is pushed up to the cam bracket F side of the journal B as shown by an arrow c in FIG. Then, the lift reaction force is released by the seating of the valve G, whereby
The cam bearing shaft portion C is hit against the cylinder head side support portion D of the journal B by the chain tension, and the cam bearing shaft portion C hits the cylinder head side support portion D of the journal B, so that bearing noise is generated.

[0005] This phenomenon is caused by the second receiving shaft portion of the cam shaft, that is,
Occurs at the second bearing supported by the second journal adjacent to the first bearing supported by the first journal near the cam sprocket mounting position. That is, a force that bends the camshaft is applied by the chain tension applied to the cam sprocket at the front end of the camshaft.
This is because a large bending is generated in the second shaft receiving portion with the shaft receiving portion as a fulcrum.

Conventionally, in order to prevent the generation of abnormal noise due to such bearing noise, the clearance between the journal and the receiving shaft is reduced, the processing accuracy of the journal and the receiving shaft is improved, or lubrication of the journal is performed. Measures have been taken to increase the amount. However, the reduction of the clearance between the journal and the receiving shaft results in deterioration of fuel efficiency due to the seizure of the journal and increase in friction, and the improvement in processing accuracy of the receiving shaft results in increased processing cost and reduced productivity. Raise the point.

[0007] To increase the amount of oil supplied to the journal, it is necessary to increase the capacity of an oil pump for supplying oil. This increases the friction and the amount of oil supplied to the cylinder head. This increases the problem of oil treatment. In view of the above-described conventional problems, the present invention has a unique form of oil in which oil introduced into an oil hole in a camshaft is guided to an outer peripheral surface of a receiving shaft portion supported by a bearing at a predetermined position of a camshaft. An object of the present invention is to provide a groove to form an oil film, thereby obtaining a damping effect by the oil film and preventing bearing noise.

[0008]

According to the first aspect of the present invention, a cam sprocket around which a wrapping transmission band is wrapped is fixedly mounted at a tip end, and rotation of a crankshaft includes the wrapping transmission band. An internal combustion engine comprising a camshaft transmitted through a wrapping transmission band mechanism, and receiving shaft portions set at a plurality of positions of the camshaft each supported by a plurality of bearings. An oil groove along the circumferential direction is formed in substantially half the circumference of the outer peripheral surface of the receiving shaft portion, and the oil groove is formed.
In the bearing portion, an oil hole communicating with the outlet side of an oil passage formed along the central axis is formed inside the camshaft ,
The oil hole was opened in the oil groove forming surface on the outer peripheral surface of the receiving shaft portion where the oil groove was formed.

According to a second aspect of the present invention, the receiving shaft portion having the oil groove formed therein is disposed adjacent to the first bearing portion supported by the first bearing near the cam transmission wheel mounting position, and The second bearing portion is supported by the second bearing. According to a third aspect of the present invention, an oil groove is formed along the circumferential direction all around the outer peripheral surface of the receiving shaft portion adjacent to the receiving shaft portion in which the oil groove is formed, and the oil groove is formed inside the camshaft along the central axis. An oil hole communicating with the formed oil passage is opened in the oil groove forming surface of the outer peripheral surface of the receiving shaft portion in which the oil groove of the entire circumference is formed, and the receiving shaft portion in which the oil groove of the entire circumference is formed is formed. An oil supply passage provided in the bearing to be supported was opened at a position on the inner peripheral surface of the bearing corresponding to the oil groove on the entire circumference.

According to a fourth aspect of the present invention, the phase of the substantially half-circle oil groove with respect to the cam is adjusted so that most of the oil groove is located on the cylinder head side portion of the bearing when the valve operated by the cam is seated. Set.

[0011]

The transmission band (wrapping transmission band) tension applied to the cam is applied, and the transmission shaft tension pushes down the receiving shaft portion toward the cylinder head side of the bearing. At the time of valve lift, the bearing portion is pushed up to the cylinder head side of the bearing by the lift reaction force of the valve spring. When the valve is seated, the lift reaction force is released, whereby the transmission shaft tension slams the bearing shaft against the cylinder head side of the bearing, and the bearing shaft hits the cylinder head side of the bearing, thereby generating bearing noise. I do.

According to the first aspect of the present invention, an oil groove is formed along a circumferential direction on substantially a half circumference of an outer peripheral surface of a bearing portion of a bearing located at a tip end side of a camshaft, and lubricating oil is held in the oil groove. Therefore, the damping effect of the oil film of the lubricating oil held in the oil groove can effectively suppress the occurrence of bearing noise when the bearing is hit against the cylinder head side of the bearing due to the tension of the drive band. it can.

According to the second aspect of the present invention, it is possible to effectively prevent the bearing noise from being generated in the second bearing on which a large bending force acts. In the invention according to claim 3,
The oil passage length from the oil supply section to the oil groove in the receiving shaft can be shortened, and the oil supply pressure to the oil groove can be increased, so the pressure of the lubricating oil held in the oil groove can be increased. ,
A high damping effect by the oil film can be obtained.

According to the fourth aspect of the present invention, a half-circle oil groove can sufficiently provide an oil film damping action, thereby causing a problem of oil treatment in blow-by gas due to an increase in oil pump capacity and an increase in oil supply to a cylinder head. There is an advantage that it does not.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the accompanying drawings. First, the configuration of the valve opening / closing mechanism will be described with reference to FIGS. In these figures, one end of each of a rocker arm 2 operated by an intake valve cam 1 and a rocker arm 4 operated by an exhaust valve cam 3 is supported by a pivot 5, and the other end is an intake valve 6 and an exhaust valve. It is in contact with each of the seven valve shaft ends.

A pair of overhead camshafts 8, 9 for the intake valve 6 and the exhaust valve 7 are provided.
Are fixedly mounted with cam sprockets 10, 11, respectively. A timing chain 13 is wound around the pair of cam sprockets 10 and 11 and the small-diameter idler sprocket 12, and the large-diameter idler sprocket 1
A chain 15 is wound around 4 and a crank sprocket fixedly mounted on a crankshaft (not shown).

Reference numeral 16 denotes a chain tensioner. next,
The bearing structure of the camshafts 8 and 9 will be described by taking the exhaust valve camshaft 9 in FIG. 1 as an example. First to fifth receiving shaft portions 17 set at a plurality of positions (five positions) of the camshaft 9 are described. ~ 21
Are supported by first to fifth bearings (journals) 22 to 26, respectively.

Each of the journals 22 to 26 is formed by fastening a cam bracket 28 to a support portion 27a to 27e on the cylinder head 27 side with a bolt 29, respectively.
The cams 25 are formed on both sides of each of the receiving shaft portions 18 to 21 of the cam shaft 9. In such a configuration, the second receiving shaft portion located on the tip end side of the cam shaft 9, that is, the first receiving shaft portion 17 supported by the first journal 22 near the mounting position of the cam sprocket 11, Half circumference (180 degrees) of the outer peripheral surface of the second shaft receiving portion 18 supported by the journal 23
Is formed with an oil groove 30 (see FIG. 2) along the circumferential direction.

In this case, the oil groove 30 is formed to extend half a circumference at an axially intermediate position on the outer peripheral surface of the second shaft receiving portion 18. An oil passage 31 extending along the center axis of the camshaft 9 is formed inside the camshaft 9. An oil hole 32 communicating with the oil passage 31 is formed in the second receiving shaft portion 18. Is opened on the surface of the outer peripheral surface of the second bearing portion 18 where the oil groove 30 is formed (see FIG. 2).

In this case, the oil hole 32 is orthogonal to the oil passage 31, one end of which communicates with the axially intermediate portion of the oil passage 31 formed in the second shaft receiving portion 18, and the other end of which is connected to the oil passage 31. The oil groove 30 is opened at an intermediate portion in the circumferential direction. On the other hand, an oil groove 33 extending in the circumferential direction is formed on the entire outer circumference of the third shaft receiving portion 19 adjacent to the second shaft receiving portion 18.

In this case, the oil groove 33 is formed to extend over the entire circumference at an axially intermediate position on the outer peripheral surface of the third shaft receiving portion 19. An oil hole 34 communicating with the oil passage 31 is formed in the third shaft receiving portion 19, and the oil hole 34 is formed in the third shaft receiving portion 19.
An opening is formed on the outer peripheral surface on which the oil groove 33 is formed. In this case, the oil hole 34 is orthogonal to the oil passage 31, one end of which communicates with the axially intermediate portion of the oil passage 31 formed in the third shaft receiving portion 19, and the other end of which is the oil groove 33. Is opened at the intermediate portion in the circumferential direction.

An oil supply passage 35 is formed in the cylinder head side support portion 27c of the third journal 24 that supports the third receiving shaft portion 19, and the oil supply passage 35 is formed on the inner peripheral surface of the third journal 24. It is opened at a position corresponding to the oil groove 33 on the entire circumference. The oil hole 36 communicating with the oil passage 31 is the fourth hole.
The oil holes 36 are also formed on the outer peripheral surfaces of the fourth and fifth shaft receiving portions 20 and 21.

In such a configuration, the lubricating oil supplied through the oil supply passage 35 reaches the oil groove 33 on the outer peripheral surface of the third shaft receiving portion 19 from the inner peripheral surface of the third journal 24, and the oil hole 34 is formed therefrom. The oil is supplied to the oil passage 31 through the oil passage 31. The lubricating oil supplied between the inner peripheral surface of the third journal 24 and the outer peripheral surface of the third shaft receiving portion 19 lubricates the bearing portion.

The lubricating oil supplied to the oil passage 31 is
From the inner peripheral surface of the fourth journal 25 and the fourth shaft receiving portion 20
It is supplied between the outer peripheral surface and between the inner peripheral surface of the fifth journal 26 and the outer peripheral surface of the fifth shaft receiving portion 21 to lubricate these bearing portions. On the other hand, the lubricating oil supplied to the oil passage 31 is supplied from the oil hole 32 to the oil groove 30 on the outer peripheral surface of the second shaft receiving portion 18, and from the oil groove 30 to the second journal 2.
3 between the inner peripheral surface and the outer peripheral surface of the second shaft receiving portion 18;
This bearing is lubricated.

The lubricating oil is held in the oil groove 30 on the outer peripheral surface of the second shaft receiving portion 18, and an oil film is formed on the outer peripheral surface of the second shaft receiving portion 18 by the held lubricating oil. Here, the mechanism of the generation of abnormal noise due to the hitting of the bearing is as described in the section of the conventional example. The lift reaction force is released by the seating of the valve, so that the receiving shaft portion is moved toward the cylinder head side of the journal by the chain tension. The bearing is hit and the receiving shaft hits the cylinder head side of the journal, so that a bearing hitting sound is generated.

That is, the tapping sound is generated when the bulb lifts downward and sits on the bulb (during a ramp). Therefore, the phase of the oil groove 30 of the second shaft receiving portion 18 with respect to the cam 3 is adjusted such that most of the oil groove 30 is located on the cylinder head side support portion 27b of the second journal 24 when the valve 7 is seated. When the setting is made, the damping action of the oil film by the lubricating oil held in the oil groove 30 causes the second shaft receiving portion 18 to be hit against the cylinder head side support portion 27b of the second journal 24 by the chain tension. The generation of sound is suppressed.

FIG. 5A shows the position of the intake valve cam 1 (right side in the figure) when the intake valve 6 is seated, and FIG. 5B shows the position of the exhaust valve cam when the exhaust valve 7 is seated. The position of the oil groove 30 (left side in the figure) is set so that most of the oil groove 30 is located on the cylinder head side support portion of the journal when the valve is seated. According to such a configuration, the oil groove 30 is formed along the circumferential direction on a half circumference of the outer peripheral surface of the second receiving shaft portion 18 where the bearing hitting sound occurs, and the lubricating oil is held in the oil groove 30. Due to the damping effect of the oil film of the lubricating oil held in the oil groove 30, the second journal shaft 18 is moved by the chain tension to the second journal 24.
Of the bearing when the cylinder is hit against the cylinder head side support portion 27b.

In this case, it is no longer necessary to take measures such as reducing the clearance between the journal and the receiving shaft, improving the machining accuracy of the journal and the receiving shaft, or increasing the amount of lubrication to the journal as in the prior art. In addition, it is possible to prevent problems such as deterioration in fuel efficiency due to seizure of the journal and increase in friction, increase in processing cost, decrease in productivity, and problem of oil treatment in blow-by gas due to increase in the amount of oil supplied to the cylinder head.

Further, according to this configuration, since the oil groove is formed on the receiving shaft portion side, the workability of the oil groove is superior to the case where the oil groove is formed on the journal side. Further, the phase of the oil groove 30 of the second receiving shaft portion 18 with respect to the cams 1 and 3 is adjusted so that most of the oil groove 30 is located on the cylinder head side support portion of the journal when the valve generating a tapping sound is seated. , The oil groove 30 provides a sufficient damping action of the oil film only in half a circumference. In the oil grooves around the entire circumference, the amount of oil leakage is large, and the problem of oil treatment in blow-by gas due to an increase in the oil pump capacity and an increase in the amount of oil supplied to the cylinder head occurs.

Further, since the oil is supplied from the third journal 24 supporting the third receiving shaft portion 19 adjacent to the second receiving shaft portion 18 provided with the oil groove 30, the oil is supplied from the lubricating portion to the third journal 24 side. 2
The oil passage length to the oil groove 30 of the receiving shaft portion 18 can be shortened, and the oil supply pressure to the oil groove 30 can be increased, so that the pressure of the lubricating oil held in the oil groove 30 can be increased. And a high damping effect by the oil film can be obtained.

In the above-described embodiment, the cam sprocket around which the timing chain is wound is fixedly attached to the tip end, and the cam shaft is provided with the rotation of the crankshaft transmitted through a chain mechanism including the timing chain. Although an example in which the present invention is applied to an internal combustion engine has been described,
The present invention can also be applied to an internal combustion engine having a camshaft to which a belt wheel around which a timing belt is wound is fixedly mounted at a tip end thereof, and in which rotation of a crankshaft is transmitted via a belt mechanism including the timing belt. Needless to say.

[0032]

As described above, according to the first aspect of the present invention, an oil groove is formed along the circumferential direction on substantially a half of the outer peripheral surface of the receiving shaft portion of the bearing located at the tip end of the camshaft. Since the lubricating oil is held in the oil groove, the damping effect of the oil film of the lubricating oil held in the oil groove causes the bearing hitting sound when the bearing is hit against the cylinder head side of the bearing due to the transmission band tension. Can effectively suppress the occurrence of problems such as seizure of bearings, deterioration of fuel efficiency due to increase of friction, increase of processing cost, deterioration of productivity, and problem of oil treatment in blow-by gas due to increase of oil supply to cylinder head. Can be prevented and the productivity is excellent.

According to the second aspect of the present invention, the second bearing supported by the second bearing is adjacent to the first bearing shaft portion supported by the first bearing near the cam transmission wheel mounting position. Since the oil groove is formed in the shaft portion, it is possible to effectively prevent bearing hitting noise in the second bearing on which a large bending force acts. According to the third aspect of the present invention, oil is supplied from the bearing side which supports the receiving shaft portion adjacent to the receiving shaft portion provided with the oil groove. Therefore, the oil passage from the oil supply portion to the oil groove of the receiving shaft portion. Since the length can be shortened and the oil supply pressure to the oil groove can be increased, the pressure of the lubricating oil held in the oil groove can be increased, and a high damping effect by the oil film can be obtained.

According to the fourth aspect of the present invention, the phase of the oil groove of the receiving shaft portion with respect to the cam is adjusted so that most of the oil groove is located on the cylinder head side portion of the bearing when the valve generating a tapping sound is seated. Therefore, there is an advantage that the oil groove around the half circumference sufficiently provides a damping action of the oil film, and the problem of oil treatment in blow-by gas due to an increase in oil pump capacity and an increase in oil supply to the cylinder head does not occur.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing one embodiment of the invention described in claims 1 to 4;

FIG. 2 is a sectional view of a second shaft receiving portion in the embodiment.

FIG. 3 is a sectional view showing a valve opening / closing mechanism.

FIG. 4 is a sectional view showing a camshaft driving structure in the valve opening / closing mechanism of the same.

FIG. 5 is a sectional view for explaining the operation of the embodiment.

FIG. 6 is a view for explaining a conventional mechanism of bearing sound generation.

FIG. 7 is a diagram for explaining a conventional mechanism of bearing sound generation.

[Explanation of symbols]

 8, 9 Cam shaft 10, 11 Cam sprocket (cam transmission wheel) 13 Timing chain (wrapping transmission band) 17 First receiving shaft portion 18 Second receiving shaft portion 19 Third receiving shaft portion 22 First journal 23 second journal 30 oil groove 31 oil passage 32 oil hole 33 oil groove 34 oil hole 35 oil supply passage

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) F01M 1/06 F01L 1/04 F01M 9/10

Claims (4)

(57) [Claims] A cam transmission wheel on which a wrapping transmission band is wound is fixedly mounted on a tip end of the camshaft. A camshaft to which rotation of a crankshaft is transmitted via a wrapping transmission band mechanism including the wrapping transmission band is provided. In an internal combustion engine comprising a plurality of bearings each of which is provided with a receiving shaft set at a plurality of positions on the camshaft, substantially half around the outer peripheral surface of the receiving shaft located on the tip side of the camshaft.
Circumferential oil groove along the formation, in the bearing unit in which the oil groove is formed to form a oil hole to the outlet side communicates with the cam shaft inside oil passage formed along its central axis, the A bearing structure for a camshaft in an internal combustion engine , wherein an oil hole is opened in an oil groove forming surface on an outer peripheral surface of a receiving shaft portion in which the oil groove is formed. 2. The receiving shaft portion in which the oil groove is formed is supported by a second bearing adjacent to the first receiving shaft portion supported by the first bearing near the cam transmission wheel mounting position. The bearing structure for a camshaft in an internal combustion engine according to claim 1, wherein the bearing structure is a second shaft receiving portion. 3. An oil groove extending in the circumferential direction is formed along the entire circumference of the outer peripheral surface of the receiving shaft portion adjacent to the receiving shaft portion in which the oil groove is formed, and is formed inside the camshaft along the central axis thereof. Bearing that opens an oil hole communicating with the oil passage formed in the oil groove forming surface of the outer peripheral surface of the receiving shaft portion in which the oil groove of the entire circumference is formed, and supports the receiving shaft portion in which the oil groove of the entire circumference is formed. 3. A camshaft bearing structure for an internal combustion engine according to claim 1, wherein an oil supply passage provided in the internal combustion engine is opened at a position corresponding to the oil groove on the entire inner circumference of the bearing. 4. A phase of said substantially half-circle oil groove with respect to a cam,
The valve according to any one of claims 1 to 3, wherein a majority of the oil groove is located in a cylinder head side portion of the bearing when the valve operated by the cam is seated.
A camshaft bearing structure in the internal combustion engine according to any one of the first to third aspects.