JP2000314304A - Bearing structure for cam shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a mechanical loss by adopting a rolling bearing, and to reduce cost by arranging shaft support part as a member as being separate to a cam shaft. SOLUTION: A cam shaft support part 14 supported rotatably by a bearing 11 of an engine body through a rolling bearing 16 is provided between a sproket (or a pulley) 13 transmitting a rotating force to a cam shaft 10 and a front end of the cam shaft 10. The cam shaft support part 14 is a member made of a material superior in abrasion resistance and independent of the cam shaft 10, and is tighteningly fixed together with the sproket 13 to a front end of the cam shaft 10 with a mount bolt 12.

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 operating intake and exhaust valves of an internal combustion engine.
The present invention relates to an improvement in a bearing structure of a camshaft rotatably supported by a bearing portion of an engine body via a rolling bearing.

[0002]

2. Description of the Related Art Conventionally, as an example of a bearing structure for rotatably supporting a camshaft of an internal combustion engine on an engine body, a slide bearing for directly supporting the outer periphery of a journal portion of a camshaft by a bearing portion of the engine body. The structure is known.
However, in this case, since the outer periphery of the journal portion directly contacts the bearing portion, it is disadvantageous in terms of mechanical loss.

[0003] In order to reduce such mechanical loss, a bearing structure in which a cylindrical rolling bearing such as a needle bearing is interposed between a bearing portion of an engine body and a camshaft is known. For example, in a camshaft described in JP-A-8-128306, a journal portion is provided between a pair of cam portions, and a cylindrical rolling bearing is interposed between the journal portion and a bearing portion. The journal part can be divided into front and rear parts.

[0004]

However, in the structure described in this publication, the camshaft has a complicated structure in which the camshaft is divided back and forth by the journal portion, and the entire camshaft including the journal portion is connected to the rolling bearing. It is necessary to use a material having high strength to withstand contact or to set an inner lace or the like on the outer periphery of the journal portion, which leads to a complicated structure and an increase in cost.

A sprocket or pulley is attached to one end of the camshaft via a bolt or the like.
Rotational force is transmitted to the camshaft via the sprocket or pulley. Therefore, among the camshafts, there is a tendency that friction is increased in a bearing portion near a sprocket or a pulley to which a rotational force is transmitted, and it is desired to use a rolling bearing in this bearing portion.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of such conventional problems. That is, the camshaft bearing structure according to the first aspect of the present invention includes a sprocket or pulley that transmits a rotational force to a camshaft that operates an intake valve or an exhaust valve of an internal combustion engine, and one end of the camshaft on the sprocket or pulley side. And a shaft support portion rotatably supported by a bearing portion of the engine body via a rolling bearing is provided between the shaft support portion and the shaft support portion.
At least another member made of a different material from the camshaft, and is fixed to one end of the camshaft together with a sprocket or a pulley.

According to the first aspect of the present invention, the use of the rolling bearing reduces the mechanical loss, and the shaft supporting portion supported by the rolling bearing is formed separately from the camshaft. The camshaft can be made of, for example, cast iron or the like at a low cost without setting an inner race or the like, so that the cost can be reduced.

Also, since the shaft support is provided between the sprocket or pulley and one end of the camshaft,
A shaft support portion supported by the rolling bearing is disposed adjacent to a sprocket or a pulley to which rotational force is transmitted. As a result, friction of the camshaft can be effectively suppressed.

In addition, since the shaft supporting portion is fixed to one end of the camshaft together with the sprocket or the pulley, the mounting is easy, and the structure can be simplified and the number of parts can be reduced.

[0010] As the rolling bearing, a general ball bearing can be used in addition to a roller bearing such as a needle bearing.

The shaft supporting portion is fixedly fastened to one end of the camshaft together with a sprocket or a pulley by mounting bolts together with the sprocket or the pulley.

In this case, the shaft supporting portion can be fixed to the camshaft by a mounting bolt for mounting the sprocket or the pulley to the camshaft.

Alternatively, the shaft support is formed integrally with a sprocket or a pulley in advance.

In this case, it is possible to reduce the number of parts corresponding to the shaft supporting portion and to suppress the angle variation between the sprocket and the camshaft, as compared with the case where the shaft supporting portion is a separate member from the sprocket. Become.

[0015] Claim 4 which further embodies the invention of claim 3
According to the invention, the sprocket or the pulley including the shaft support is fixed to one end of the camshaft by press fitting.

In this case, mounting bolts for sprockets or pulleys become unnecessary, the number of parts can be further reduced, and the structure can be further simplified.

[0017]

As described above, according to the present invention, while employing a rolling bearing, mechanical loss can be reduced.
Since the shaft supporting portion supported by the rolling bearing is a separate member from the camshaft, the camshaft can be formed inexpensively, for example, from cast iron without setting an inner race or the like, and cost reduction can be achieved. .

Further, since the shaft supporting portion supported by the rolling bearing is disposed adjacent to the sprocket or the pulley to which the rotational force is transmitted, friction of the camshaft can be effectively suppressed.

Further, since the shaft support can be fixed to one end of the camshaft together with the sprocket or pulley,
It is easy to assemble, and the structure can be simplified and the number of parts can be reduced.

[0020]

FIG. 1 shows the structure of a bearing on the front side of an engine of a camshaft 10 according to a first embodiment of the present invention.

The camshaft 10 for operating the intake valve or the exhaust valve of the internal combustion engine is located in the front-rear direction of the engine (the left-right direction in FIG. 1).
A sprocket (or pulley) 13 is fixed to a front end (left end in FIG. 1) of the sprocket 13 by a mounting bolt 12. This camshaft 10 is used for the sprocket 1
Rotational force is transmitted from a crankshaft (not shown) via a chain (not shown) or a timing belt (not shown) wound around the motor 3, and rotates in conjunction with the engine.

In this embodiment, the sprocket 13
And a front end of the camshaft 10, a substantially cylindrical shaft support portion 14 rotatably supported by a bearing portion 11 of a cylinder head as an engine body, and an outer peripheral surface of the shaft support portion 14. And the inner peripheral surface 11 of the bearing portion 11
A cylindrical rolling bearing 16 is interposed between the inner periphery of a and a.

In this embodiment, the shaft support portion 14 is formed as a separate member from the camshaft 10 and the sprocket 13, and is fixed together with the sprocket 13 to one end of the camshaft 10 by mounting bolts 12.
The shaft support portion 14 is formed of a material having high wear resistance and high rigidity, such as chromium molybdenum steel, which can withstand contact with the rolling bearing 16. On the other hand, since the camshaft 10 does not need to have a structure that can withstand contact with the rolling bearing 16, it is formed of a relatively inexpensive material such as cast iron.

As the rolling bearing 16, a needle bearing in which a number of needles 16b are rotatably mounted on a cylindrical outer race 16a is used here. Further, as described above, since the shaft supporting portion 14 is made of a material that can withstand contact with the rolling bearing 16, the rolling bearing 1
6 can have a structure in which the inner race is omitted, and the outer periphery of the shaft support portion 14 is directly connected to the needle 16.
It is in sliding contact with b.

A front flange portion 15 for receiving the front surfaces of the bearing portion 11 and the rolling bearing 16 is formed on the shaft supporting portion 14, and a front end of the camshaft 10 receives the rear surface of the bearing portion 11 and the rolling bearing 16. A rear flange portion 10a is formed, and these support the thrust direction.

In order to prevent the shaft support portion 14 from rotating relative to the camshaft 10, a detent pin 17 is driven into the front surface of the camshaft 10;
A detent pin 17 is provided on the rear surface of the shaft support 14.
Is formed with a fitting portion 14a.

When assembling, the rolling bearing 16 is attached to the inner peripheral surface 11a of the bearing portion 11 or the outer peripheral surface of the shaft support portion 14 in advance, and the sprocket 13, the shaft support portion 14, and the camshaft 10 are assembled as shown in FIG. Bearing 1 as shown
Assemble to 1. Then, the mounting bolt 12 is inserted through the sprocket 13 and the shaft
0, and the mounting bolt 12 is tightened, so that the shaft supporting portion 14 and the sprocket 13 together with the flange portion 12a of the bolt 12 and the camshaft 1
0, and is fastened and fixed to the camshaft 10 firmly.

According to the present embodiment, the shaft supporting portion 14 rotatably supported by the rolling bearing 16 is connected to the camshaft 10 while the mechanical loss is reduced by employing the cylindrical rolling bearing 16. Because it was a separate member,
Only the shaft support portion 14 may be made of a material having high strength that can withstand contact with the rolling bearing 16, and the camshaft 10 can be formed inexpensively by using, for example, cast iron without using inner races. Can be achieved.

Further, since the shaft supporting portion 14 supported by the rolling bearing 16 is disposed adjacent to the sprocket 13 to which the rotational force is transmitted, the friction of the camshaft 10 can be effectively suppressed. Can be.
More specifically, the bearings of the camshaft 10 other than the front end shown in FIG.
Although it is difficult to adopt the bearing structure using the bearing, the friction of the bearing portion is particularly large at the front end where the tension of the chain or the timing belt acts, and the bearing structure of the present embodiment using the rolling bearing 16 in this portion. By adopting,
A sufficient friction reducing effect can be obtained.

Further, since the shaft supporting portion 14 can be fixed to one end of the camshaft 10 by using the mounting bolts 12 for mounting the sprocket 13, the assembly is easy, the number of parts is reduced, and the structure is reduced. Can be simplified.

In addition, if the camshaft 10 and the shaft support portion 14 are temporarily fixed via the detent pins 17 and co-processed before assembly, the shaft support portion 14 is formed as a separate member from the camshaft 10. Nevertheless, high coaxiality can be obtained.

FIG. 2 shows a camshaft bearing structure according to a second embodiment of the present invention. In the embodiments described below, the same components as those in the above-described embodiments are denoted by the same reference numerals, and redundant description will be omitted as appropriate.

In this embodiment, a shaft support portion 24 rotatably supported by the rolling bearing 16 and a front flange portion 25 for receiving the front surface of the bearing portion 11 and the rolling bearing 16 are provided.
The sprocket (or pulley) 23 is integrally formed on the rear surface side. A cylindrical portion 10b into which the mounting bolt 12 is screwed is formed at the front end of the camshaft 10, and a sprocket 23 including a shaft support portion 24 and a front flange portion 25 is fitted around the cylindrical portion 10b. It is configured to be.

At the time of assembly, the rolling bearing 16 is attached to the inner peripheral surface 11a of the bearing portion 11 or the outer peripheral surface of the shaft support portion 14 in advance, and then the sprocket 2 is mounted as shown in FIG.
3 and the camshaft 10 are assembled to the bearing 11, and the sprocket 23 is
May be fixed together at one end.

According to the second embodiment, the same effects as those of the first embodiment can be obtained, and the shaft support 2
4 is integrated with the sprocket 23, so that the number of parts for the shaft supporting portion is reduced as compared with the case where the shaft supporting portion is formed as a separate member from the sprocket, and the angular variation between the sprocket 23 and the camshaft 10 is reduced. It becomes possible to suppress.

FIG. 3 shows a camshaft bearing structure according to a third embodiment of the present invention. This embodiment is basically the same as the second embodiment, except that the mounting bolt 12 is not used as in the second embodiment, but the shaft supporting portion 2 is used.
4. The sprocket 23 including the front flange portion 25 is fixed to the front end of the camshaft 10 by press fitting. More specifically, mounting holes 23 formed in sprocket 23
a is a cylindrical portion 10 formed at the front end of the camshaft 10.
b.

According to this embodiment, in addition to the same effects as in the second embodiment, the number of parts for mounting bolts can be further reduced, and the structure can be further simplified. . Further, since one end of the mounting hole 23a is closed by the part 23c of the sprocket 23, it is not necessary to separately provide a plug for closing the lubricating oil passage 28 formed in the camshaft 10.

However, when the press-fit fixing is adopted as in this embodiment, the rolling bearing 16 cannot be removed after the assembly.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a camshaft bearing structure according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a camshaft bearing structure according to a second embodiment of the present invention.

FIG. 3 is a sectional view showing a bearing structure of a camshaft according to a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Camshaft 11 ... Bearing part 12 ... Mounting bolt 13 ... Sprocket 14 ... Shaft support part 16 ... Rolling bearing

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3G016 AA06 AA19 BA31 BA33 CA19 CA22 CA23 CA31 CA46 CA52 EA02 EA05 FA27 FA29 GA00 GA01 3J101 AA14 AA24 AA32 AA42 AA52 AA62 AA72 BA77 EA04 FA41 FA44 FA46 FA55 GA21

Claims (4)

[Claims] A sprocket or pulley for transmitting a rotational force to a camshaft for operating an intake valve or an exhaust valve of an internal combustion engine, and one end of the camshaft on the sprocket or pulley side via a rolling bearing. A shaft support portion rotatably supported by a bearing portion of the engine body is provided. This shaft support portion is at least another member made of a different material from the camshaft, and is fixed to one end of the camshaft together with a sprocket or a pulley. A bearing structure for a camshaft, characterized in that: 2. The camshaft bearing structure according to claim 1, wherein the shaft support portion is fixedly fastened to one end of the camshaft together with a sprocket or a pulley by a mounting bolt. 3. The camshaft bearing structure according to claim 1, wherein the shaft support portion is formed integrally with a sprocket or a pulley in advance. 4. The camshaft bearing structure according to claim 3, wherein the sprocket or the pulley including the shaft support is fixed to one end of the camshaft by press fitting.