JP2596078Y2 - Camshaft bearing device - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a bearing device for supporting a camshaft, which is used for operating a valve of an internal combustion engine or driving a plunger of a fuel injection pump.

[0002]

2. Description of the Related Art In recent years, the number of cylinders and the number of cylinder bores have been increasing with the increase in engine output. Therefore, the total length of camshafts for driving the intake and exhaust valves of each cylinder has been long. Tend to be. Further, in the case of a diesel engine, the number of plungers of an in-line fuel injection pump used for fuel supply increases as the number of cylinders increases, so that the overall length of the cam shaft for driving the plunger tends to increase.

As described above, when the overall length of the camshaft becomes longer,
With only two bearings provided at both ends of the camshaft, the load capacity is insufficient, and it becomes difficult to sufficiently secure the durability of the bearings at both ends. Therefore, in addition to these bearings, another bearing is used. Need to be provided in the middle part of Therefore, when three or more bearings are used to support the camshaft, FIG.
In the example, as illustrated as a cam shaft 12 that is supported by the cylinder head 11, on both sides and an intermediate portion of the cam shaft 12,
In general, ball bearings 13a to 13c having a sufficient load capacity to absorb rotational sliding resistance and bending vibration of the camshaft are provided and supported.

[0004]

However, in this case, a ball bearing 13 provided at an intermediate portion of the camshaft 12 is required.
b cannot be mounted unless the inner diameter B of each cam 14 is larger than the maximum outer diameter A of each cam 14.
It is understood that the cam shaft 12 cannot be assembled unless the inner diameter F of the mount portion 11a of the cylinder head 11 on the side where the ball bearing 13 is inserted is larger than the outer diameter E of the ball bearing 13b.

Accordingly, the ball bearings 13a to 13c
The width G of the housing space of the cylinder head 11 for housing the camshaft 12 to which the camshaft 12 is attached is determined by the inner diameter F of the mount portion 11a, and it is necessary to secure an unnecessarily large housing space. There is a problem that the size of the head and, consequently, the size of the cylinder block is increased, resulting in an increase in the size and weight of the entire engine.

[0006] In view of the above problems, the present invention provides a camshaft bearing device which can reduce the maximum outer diameter of a camshaft including a bearing as much as possible, thereby contributing to downsizing and lightening of an engine. It is intended to do so. Also, the present invention
It is an object of the present invention to provide the above-described bearing device without impairing the durability of a journal portion of a camshaft and related parts that come into contact with the cam.

[0007]

According to the present invention, there is provided a camshaft bearing device according to the present invention, wherein a camshaft is formed in a through hole formed in a wall of a housing space for housing a camshaft formed in a support. A camshaft bearing device inserted and disposed in the axial direction, wherein both sides of the camshaft are supported by ball bearings , and journal portions between these ball bearings are fixed.
It is received by chromatography color bearings, a structure which is characterized by comprising the roller bearing on the support for supporting the camshaft.

[0008] Then, the inner diameter of the roller bearing (B), the maximum outer diameter (A) greater than the cam of the cam shaft, and said provided on both sides of the cam shaft Borubea
It is characterized in that it is formed smaller than the outer diameter (C) of at least one of the rings .

In addition, a high-hardness annular member is provided on the peripheral surface of the journal portion that slides on the roller bearing . Since this bearing device can be used for a device that supports various camshafts, such as a camshaft for operating a valve of an internal combustion engine and a camshaft for driving a plunger of a fuel injection pump, An engine body such as a cylinder head or a cylinder block, a fuel injection pump body, or the like can be applied.

It is preferable to use a material such as a ceramic having high hardness as the annular member, but the present invention is not limited to this.

[0011]

The camshaft bearing device of the present invention has the above-described structure. By providing roller bearings, which are bearings other than ball bearings provided on both sides of the camshaft , on the support side, the camshaft itself is provided. Since it is not necessary to provide three or more bearing members, the maximum outer diameter of the camshaft including the bearing can be reduced as much as possible.

Further, since a high hardness annular member is provided on the peripheral surface of the journal portion of the cam shaft which is supported by the roller bearing , the journal portion is worn due to bending vibration of the cam shaft itself. Can be prevented.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In the first embodiment of the camshaft bearing device according to the present invention, as shown in FIG. 1, one end of the camshaft 12 is provided with a timing gear to which the rotational motion of the crankshaft is transmitted via a timing belt. Further, on both sides of the camshaft 12, first bearing members (ball bearings) 13a and 13c fixed by press-fitting are provided.

The ball bearings 13a, 13
Between c, cams for driving the intake valve for opening and closing the intake valve of each cylinder and for driving the exhaust valve for opening and closing the exhaust valve.
14, and a journal portion 12 supported by a second bearing member (roller bearing) 15 press-fitted into the cylinder head 11.
a is located. The intermediate portion of the camshaft 12 is not provided with a bearing member such as a ball bearing, but is simply formed as a journal portion 12a having an outer diameter B larger than the maximum outer diameter A of each cam 14, and this journal portion 12a is formed. The roller bearing 15 to be supported is attached to the cylinder head 11 side.

Since the camshaft bearing device of the first embodiment is constructed as described above, when the rotational movement of the crankshaft is transmitted to the timing gear, the ball bearings 13a and 13c on both sides and the intermediate portion are provided. The camshaft 12 which is supported by the roller bearing 15 rotates smoothly with almost no rotational sliding resistance. Also, with this configuration, the inner diameter C of the mount portion 11a of the cylinder head 11 on the side where the cam shaft 12 is inserted is set.
The diameter of the mounting portion 11 can be made relatively small as necessary to insert the journal portion 12a.
The width D of the accommodation space of the camshaft 12 defined by the inner diameter C of a can be reduced as much as possible.

Therefore, the space for housing the camshaft 12 can be reduced as much as possible, and the size and weight of the engine can be reduced. In the second embodiment of the camshaft bearing device according to the present invention, as shown in FIGS. 2 and 3, a case where a camshaft 2 for a valve train is supported on a support (cylinder head) 1 is shown. Is shown.

At one end of the camshaft 2 is provided a timing gear 6 to which the rotational movement of the crankshaft is transmitted via a timing belt. Further, both sides of the camshaft 2 are press-fitted. A fixed first bearing member (ball bearing) 3 is provided. Further, between these ball bearings 3, cams 4a for driving the intake valves for opening and closing the intake valves of the respective cylinders, cams 4b for driving the exhaust valves for opening and closing the exhaust valves, and the cylinder head 1 are press-fitted. A journal portion 2a supported by a second bearing member (roller bearing) 5 is disposed.

Further, in the second embodiment, an annular member 7 made of high hardness ceramic whose outer peripheral surface is formed as a mirror-like sliding surface at the time of manufacturing is pressed into the peripheral surface of the journal portion 2a. In the outer peripheral surface of the annular member 7,
It is configured to be in sliding contact with the roller bearing 5. Since the camshaft bearing device of the second embodiment is configured as described above, when the rotational motion of the crankshaft is transmitted to the timing gear 6, the ball bearings 3 on both sides and the roller bearing 5 on the intermediate portion are transmitted. The camshaft 2 which is rotatably supported smoothly rotates with almost no rotational sliding resistance.

Further, due to the subtle torsional vibration generated in the camshaft 2, a stress is generated in the journal portion 2a supported by the roller bearing 5 so as to promote the wear of this portion. Since the high-hardness annular member 7 is provided on the 2a as described above, it is practically hardly worn, and the stress released to both sides of the camshaft 2 is absorbed by the ball bearing 3.

That is, the camshaft 12 of the first embodiment shown in FIG.
Camshaft absorbed by ball bearing 13b in the middle of
The roller bearing 15 cannot absorb the bending vibration of the bearing 12, and the journal 12a on the camshaft 12 itself is subjected to the stress, so that the journal 12a is liable to wear. Can be prevented. In addition, in order to improve the wear resistance of the camshaft 12 itself, a material having high hardness is used as a base material of the gum shaft 12, or the hardness of the camshaft 12 itself is improved by induction hardening or the like. A problem that occurs when using such means as increasing the hardness, that is, due to the increase in hardness, the workability of the cam profile during cutting is significantly deteriorated, the productivity is reduced, and the durability of the cutting tool is also reduced. In addition, it is possible to prevent various problems such as an increase in machining cost and an increase in the hardness of the sliding surface of the cam 14 and an increase in wear of related parts such as tappets that come into contact with the cam 14.

Therefore, according to the camshaft bearing device of the present embodiment, the maximum outer diameter C of the entire camshafts 12 and 2 including the bearing members can be reduced as much as possible. 11, 1 and this cylinder head 11, 1
It is possible to reduce the size of the cylinder block in which the engine is assembled, and to reduce the size and weight of the entire engine.

[0022]

The camshaft bearing device of the present invention is a camshaft in which a camshaft is inserted from the axial direction into a through hole opened in a wall of a housing space for housing the camshaft formed on a support. of a bearing device, the pivotally supported on both sides of the cam shaft with ball bearings <br/>, receives the journal portion between these ball bearings with roller bearings, the roller
Since the bearing is provided on the support for supporting the camshaft, the following effects can be obtained.

Ball bearings provided on both sides of the cam shaft
By providing roller bearings other than bearings on the support side, there is no need to provide three or more bearing members on the camshaft itself, so the maximum outer diameter of the camshaft including the bearings is made as small as possible. Therefore, it is possible to contribute to reduction in size and weight of the engine. By forming the inner diameter B of the roller bearing larger than the maximum outer diameter A of the cam of the camshaft and smaller than the outer diameter C of at least one of the ball bearings provided on both sides of the camshaft. The camshaft can be easily inserted into the accommodation space of the camshaft.

Further, since a high-hardness annular member is provided on the peripheral surface of the journal portion of the camshaft which is supported by the roller bearing , the journal portion is worn by bending vibration of the camshaft itself. Can be prevented.

[Brief description of the drawings]

FIG. 1 is a plan view of a part of a camshaft bearing device according to a first embodiment of the present invention;

FIG. 2 is a cross-sectional plan view of a part of a camshaft bearing device according to a second embodiment of the present invention.

FIG. 3 is an enlarged view of a main part of FIG. 1;

FIG. 4 is a plan view showing a cross section of a part of a conventional camshaft bearing device.

[Explanation of symbols]

 1,11 Support (cylinder head) 2,12 Camshaft 2a, 12a Journal 3,13a, 13c First bearing member (ball bearing) 5,15 Second bearing member (roller bearing) 7 Ring member

──────────────────────────────────────────────────続 き Continuation of the front page (56) References Japanese Utility Model Sho 60-34504 (JP, U) Japanese Utility Model Sho 61-58601 (JP, U) Japanese Utility Model Sho 57-123905 (JP, U) Field (Int.Cl. ⁶ , DB name) F01L 1/04

Claims (3)

(57) [Scope of request for utility model registration] 1. A camshaft bearing device in which a camshaft is inserted in a through-hole opened in a wall of an accommodation space for accommodating a camshaft formed in a support member from an axial direction. both sides as well as pivotally supported by ball bearings, these baud
The journal portion between the bearings receiving a roller bearing, the bearing apparatus of the camshaft, characterized by comprising the roller bearing on the support for supporting the camshaft. 2. An inner diameter (B) of the roller bearing.
Is larger than the maximum outer diameter (A) of the cam of the cam shaft,
The camshaft bearing device according to claim 1 , wherein the outer diameter (C) of at least one of the ball bearings provided on both sides of the camshaft is smaller than the outer diameter (C). 3. The camshaft bearing device according to claim 1 , wherein a high-hardness annular member is provided on a peripheral surface of said journal portion which slides on said roller bearing .