TAPPET ROLLER BEARING
A tappet roller bearing 10 includes a support shaft 20 to be supported on a locker arm 4, and first and second rollers 11 and 12 which can be respectively supported rotatably on the periphery of the support shaft 20 and are arranged together in the axial direction of the support shaft 20. The first roller 11 constitutes a plain bearing, and the second roller 12 constitutes a full type roller bearing or a plain bearing. Due to this, the tappet roller bearing 10 can extend its life, can enhance its assembling efficiency and can reduce its manufacturing cost.
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The present invention relates to a tappet roller bearing and, specifically, the invention relates to a tappet roller bearing to be mounted into a cam follow apparatus which is used in the variable valve mechanism of an engine.
BACKGROUND ARTIn recent years, there has been increasing an engine employing a variable valve mechanism which changes the opening and closing timing of one or both of a suction valve or an exhaust valve according to the changes of the rotation speed of the engine. Such variable valve mechanism is generally constituted of a cam follower apparatus including a locker arm for a high speed cam and a locker arm for a low speed cam. Also, in order to make compact the structure of an engine in the axial direction thereof and to reduce the number of parts of the engine to thereby reduce the cost of the engine, there is also proposed a cam follower apparatus which includes a lock arm for high speed and low speed cams and also which, in operation, slides these cams in the axial direction thereof to thereby switch the high speed and low speed cams over to each other.
The cam follower apparatus includes a locker arm which is disposed opposed to a cam fixed to a cam shaft rotatable in synchronization with the crankshaft of the engine and has a roller to receive the movement of the cam (see, for example, the patent reference 1 to 3). According to a cam follower apparatus disclosed in the patent reference 1, in the intermediate portion of a locker arm, there is provided a support shaft and, on this support shaft, there are rotatably supported multiple tappet rollers which can be contacted with the cam fixed to the cam shaft. According to a cam follower apparatus which is disclosed in the patent reference 2 and is mounted on the end portion of a locker arm, there are included: a shaft the two end portions of which are respectively supported on a pair of support plates and also which is used to constitute an inner race; three outer races respectively interposed between the pair of support plates; and, multiple rollers respectively interposed between the shaft and three outer races and each having a length extending over the whole of the three outer races. Also, according to a cam follower apparatus which is disclosed in the patent reference 3 and is mounted on the end portion of a locker arm, there are included: a shaft the two end portions of which are respectively supported on a pair of support plates and also which is used to constitute an inner race; two outer races respectively interposed between the pair of support plates; and, multiple rollers respectively interposed between the shaft and two outer races and each having a length extending over the whole of the two outer races.
Further, according to a roller bearing disclosed in the patent reference 4, there are included: a shaft the two end portions of which are respectively supported on a pair of support plates and also which is used to constitute an inner race; an outer race interposed between the pair of support plates through a washer; and, multiple rollers respectively interposed between the shaft and outer race and arranged in two lines in the axial direction of the roller bearing through a spacer.
RELATED ART REFERENCE Patent ReferencePatent Reference 1: U.S. Pat. No. 6,532,920 Specification
Patent Reference 2: German Patent Application No. 102006018512 Specification
Patent Reference 3: Japanese Patent Publication No. 2009-293392
Patent Reference 4: U.S. Pat. No. 3,674,325 Specification
SUMMARY OF THE INVENTION Problem that the Invention is to SolveHere, according to the cam follower apparatus disclosed in the patent reference 1, since the rollers are separated from each other by the side walls of the locker arm, there is raised a problem that the space of the locker arm in the axial direction thereof is large. Also, in the patent reference 2 or 3, since, for each of the rollers of the locker arm, there are disposed two or three outer races in such a manner that the they straddle over the roller, there is a possibility that an edge load can occur in the end portions of the respective outer races. Further, in the roller bearing disclosed in the patent reference 4, the washer is interposed between the outer race and the side wall of the locker arm, and the spacer is interposed between the two lines of rollers. This complicates the assembling operation of the roller bearing and also increases the space thereof in the axial direction.
The present invention aims at solving the problems found in the above prior art technology. Thus, it is an object of the invention to provide a tappet roller bearing which can extend its life, can enhance its assembling efficiency and can reduce its manufacturing cost. Also, it is another object of the invention to provide a tappet roller bearing which, for use in a cam follower apparatus for sliding high speed and low speed cams in the axial direction thereof to thereby switch them over to each other, can extend its life, can enhance its rotation performance and its assembling efficiency, and can reduce its manufacturing cost.
Means for Solving the ProblemThe above objects of the invention can be attained by the following structures.
(1) A tappet roller bearing, including:
a support shaft to be fixed to a locker arm for receiving the movement of a cam to be supported on the cam shaft of an engine; and
first and second rollers respectively supported rotatably on the periphery of the support shaft and arranged in the axial direction of the support shaft, wherein:
the first roller constitutes a plain bearing; and
the second roller constitutes a full type roller bearing or a plain bearing.
(2) The tappet roller bearing according to article (1), wherein:
the cam includes a high speed cam and a low speed cam respectively disposed on the cam shaft slidably in the axial direction of the cam shaft;
the first roller constituting the plain bearing is contacted with the high speed cam; and
the second roller constituting the full type roller bearing is contacted with the low speed cam.
(3) The tappet roller bearing according to article (1) or (2), wherein:
the cam includes a high speed cam and a low speed cam respectively disposed on the cam shaft slidably in the axial direction of the cam shaft;
the outer peripheral surface of the first roller to be contacted with the high speed cam is formed by barrel working to be carried out after polish finishing; and
the outer peripheral surface of the second roller to be contacted with the low speed cam is formed by polish finishing without being barrel worked.
(4) The tappet roller bearing according to any one of articles (1) to (3), wherein
the outer peripheral surfaces of the first and second rollers are not crowning worked but have a uniform diameter in the axial direction thereof.
(5) The tappet roller bearing according to anyone of articles (1) to (4), wherein
at least one of the first and second rollers is structured so that an axial direction end face has a convex shape.
(6) The tappet roller bearing according to article (5), wherein:
at least one of the first and second rollers, the axial direction end face of which is formed to have the convex shape, constitutes a double roller; and
the inner roller of the double roller is structured so that an axial direction end face has a convex shape.
(7) The tappet roller bearing according to article (5), wherein:
the second roller constitutes a full type roller bearing; and
the multiple rollers of the roller bearing, together with the second roller, are structured so that respective axial direction end faces have a convex shape.
(8) The tappet roller bearing according to any one of articles (1) to (7), wherein:
the support shaft is formed to have a staged shape including first and second shaft portions different from each other in the outside diameter dimension thereof;
the first roller is disposed on the periphery of the first shaft portion; and
the second roller is disposed on the periphery of the second shaft portion.
(9) The tappet roller bearing according to any one of articles (1) to (8), wherein
the first and second rollers are different from each other in the axial direction width thereof.
(10) The tappet roller bearing according to any one of articles (1) to (9), wherein
the first and second rollers are different from each other in the roller diameter thereof.
(11) The tappet roller bearing according to any one of articles (1) to (10), further comprising
a third roller rotatably supported on the periphery of the support shaft and arranged together with the first and second rollers in the axial direction of the support shaft.
(12) The tappet roller bearing according to any one of articles (1) to (10), further comprising
a third roller rotatably supported on the periphery of the support shaft and arranged together with the first and second rollers in the axial direction of the support shaft, wherein
in a case that the second roller constitutes a roller bearing, the third roller is situated on the opposite side to the second roller with respect to the first roller.
(13) The tappet roller bearing according to article (11) or (12), wherein
the outer peripheral surface of at least one of the first to third rollers is crowning worked.
ADVANTAGE OF THE INVENTIONAccording to a tappet roller bearing of the invention, in the first and second rollers which are respectively supported rotatably on the periphery of the support shaft and are arranged together in the axial direction of the support shaft, the first roller constitutes a plain bearing, while the second roller 12 constitutes a full type roller bearing or a plain bearing. Thanks to this structure, the present tappet roller bearing can extend its life, can enhance its assembling efficiency, and can reduce its manufacturing cost.
Also, according to the invention, in the cam follower apparatus which slides the high speed and low speed cams in the axial direction thereof to thereby switch these cams over to each other, the first roller constituting the plain bearing can be contacted with the high speed cam, while the second roller constituting the full type roller bearing can be contacted with the low speed cam. Thanks to this structure, the present cam follower apparatus can extend its life, can enhance its rotation performance and its assembling efficiency, and can reduce its manufacturing cost.
Now, description will be given below specifically of a tappet roller bearing according to the respective embodiments of the invention with reference to the drawings.
First EmbodimentFirstly, description will be given below of a cam follower apparatus 1 with reference to
Also, with the base end portion (in
On the other hand, in the leading end portion (in
The tappet roller bearing 10 according to the present embodiment, as shown in
The support shaft 20 is constituted of a steel-made hollow or solid shaft member and, when the two end portions of the support shaft 20 are caulked into the shaft holes 9a formed in the paired support wall portions 9, the support shaft 20 can be fixed to the support wall portions 9.
Here, the first roller 11, with which the high speed cam 3a can be contacted, constitutes a single roller serving as a plain bearing which can be slidingly contacted with the outer peripheral surface of the support shaft 20. Also, the second roller 12, with which the low speed cam 3b can be contacted, constitutes the outer race of a roller bearing including multiple rollers 13 which are interposed in a full type roller manner between the roller bearing and support shaft 20.
The first and second rollers 11 and 12 are substantially equal to each other in the outside diameter dimension thereof. The first and second rollers 11 and 12 may be made of metal such as bearing steel or carbon steel, provided that the metal can secure necessary hardness through the heat treatment thereof. And, they may be constituted of the same material or may be constituted of different materials. For example, by using materials which are different in the carbon contents thereof, they may be prevented from biting into each other.
The respective outer peripheral surfaces of the first and second rollers 11 and 12 have been crowning worked, which can prevent an excessive surface pressure due to an edge load from acting on the rolling contact portions of the rollers with the cams 3a and 3b and also which makes it possible for the rollers to deal with the inclination of the cams 3a, 3b and tappet roller bearing 10.
The crowning may include any of full crowning, partial crowning, logarithmic arc crowning and composite arc crowning. Also, the radius of curvature of the crowning may be different between the first and second rollers 11 and 12. Preferably, the radius of curvature of the first roller 11 to be contacted by the high speed cam 3a may be set smaller than the radius of curvature of the second roller 12 to be contacted by the low speed cam 3b, and large crowning may be carried out on the first roller 11 with which the high speed cam 3a can be contacted.
The allowable surface pressure of the respective cams 3a and 3b is up to 2 GPa or so, while the allowable surface pressure of the tappet roller bearing 10 is set higher than the allowable surface pressure of the respective cams 3a and 3b. In the case that the surface pressure of these members 3a and 3b exceeds the allowable surface pressure, there occurs a peeling phenomenon in these members. Therefore, the crowning working is carried out on the outer peripheral surfaces of the cams 3a and 3b in order to prevent their respective contact surface pressures from exceeding their respective allowable surface pressures.
However, when there is little possibility that misalignment can occur, the crowning working can be omitted. In this case, the outer peripheral surfaces of the first and second rollers 11 and 12 respectively have a uniform diameter in the axial direction thereof.
Also, the second roller 12 to be contacted by the low speed cam 3b, after it is polish finished, may not receive additional surface working such as barrel working. On the other hand, on the first roller 11 to be contacted by the high speed cam 3a, there are carried out not only polish finishing but also additional surface working such as barrel working.
Here, in
In the cam follower apparatus 1 structured in the above-mentioned manner, the outer peripheral surface of the first or second roller 11 or 12 is contacted with the outer peripheral surface of the high speed cam 3a or low speed cam 3b due to the energizing force of the valve spring 8. In this state, the rotation of the cam shaft 2 is converted to the reciprocating oscillatory motion of the locker arm 4 about the locker shaft 5, and the engine valve 7 is moved or reciprocated in the axial direction thereof against the energizing force of the valve spring 8 or due to the energizing force of the valve spring 8, while the lift amount of the engine valve 7 is variable. Thanks to this, a suction port or an exhaust port to be formed in a cylinder head (not shown) can be opened and closed.
Also, in the tappet roller bearing 10, since the first roller 11 is used as a plain bearing and the second roller 12 is used a roller bearing, there is eliminated the need to provide a washer, which is necessary when the two rollers are respectively constituted of roller bearings, for prevention of mutual interference between the two rollers in the axial direction thereof. Therefore, the tappet roller bearing 10 is enhanced in the assembling efficiency thereof and also can reduce the manufacturing cost thereof.
Further, a plain bearing has a problem that it has such sufficient durability as can neglect the need to consider the life of the bearing but it provides large frictional resistance in the low speed rotation area. However, in the high speed rotation area, the frictional resistance of the plain bearing is low and is substantially equal to that of a roller bearing.
Therefore, in the tappet roller bearing 10, the second roller 12 for contact with the low speed cam 3b is constituted of a roller bearing to thereby be able to reduce the frictional resistance in the low speed rotation time, while the first roller 11 for contact with the high speed cam 3a is constituted of a plain bearing to thereby be able to eliminate a possibility that a high load in the high speed rotation time can have an influence on the life of the bearing.
Accordingly, since the first and second rollers 11 and 12 are structured as in the present embodiment according to the high speed cam 3a and low speed cam 3b, the enhanced rotation performance (dynamic torque) due to the reduced frictional resistance and the increased life of the bearing can be attained at the same time.
Now,
Also,
For example, as shown in
Also, the tappet roller bearing 10, as shown in
Specifically, as shown in
On the other hand, as shown in
Next, description will be given below of a tappet roller bearing according to a second embodiment of the invention with reference to
In a tappet roller bearing according to the present embodiment, the axial direction two end faces of at least first and second rollers 11, 11a and 12, 12a are formed to have a convex shape. Owing to this, bearings, which are respectively constituted of the first and second rollers 11, 11a, 12, 12a, can be prevented from moving together, thereby being able to reduce sliding torque which can be generated between the mutually opposing end faces of the rollers. Also, there can also be reduced sliding torque which can be generated between the first and second rollers 11, 11a, 12, 12a and a pair of support wall portions 9 of a locker arm respectively disposed opposed to the first and second rollers on the outside in the axial direction of the support shaft 20. Further, supply of a lubricant to the support shaft 20 can be facilitated and thus the support shaft 20 can be prevented against abrasion and seizure.
The above structure according to the present embodiment can be applied to an arbitrary tappet roller bearing 10 according to the first embodiment. That is, for example, similarly to
Also, in a tappet roller bearing 10 as well which is shown in
Further,
Also, although, in
However, as shown in
Also, the structure according to the present embodiment, similarly to
Next, description will be given below of a tappet roller bearing according to a third embodiment of the invention with reference to
According to the present embodiment, there is provided a structure which can prevent a tappet roller bearing 10 against wrong assembly when it is assembled. In the previously described embodiments, it is difficult to judge from the outside which of the first and second rollers 11, 11a, 12, 12a, 12b is a roller to be contacted with the high speed cam or low speed cam. Therefore, in the case that the first and second rollers are different from each other only in the crowning shape thereof, it is difficult to judge visually which one of the rollers is the roller to be contacted. Also, in the case that the first and second rollers 11, 11a, 12, 12a, 12b are different from each other in the surface treatment thereof, even when they respectively constitute the same bearing composing elements, it is necessary to judge whether they are to be contacted with the high speed or low speed cam, which makes it necessary to take measures against wrong assembly.
Therefore, in the case that a tappet roller bearing 10 shown in
Here, since a load to be applied to the second roller 12 from the low speed cam 3b is smaller than a load to be applied thereto from the high speed cam 3a, stress involved with the support shaft 20 is also low and an oil film may be formed small. In view of this, the second roller 12 to be contacted with the low speed cam 3b is disposed on the periphery of the second shaft portion 20b having a smaller diameter than the first shaft portion 20a.
Also, the outside diameter dimensions of the first and second rollers 11 and 12 are set equal to each other. Therefore, the sum of the diameter direction dimension (thickness) of the second roller 12 and the diameter direction dimension (roller diameter) of multiple rollers 13 can be set larger than the diameter direction dimension (thickness) of the first roller 11. Here, in this case, preferably, the thickness of the second roller 12 may be set larger than the roller diameter.
Specifically, the tappet roller bearing 10 shown in
Also, according to a modification of the present embodiment, as shown in
Also, as shown in
Further, according to a further modification of the present embodiment, the tappet roller bearing may also be structured such that the first and second rollers 11 and 12 are formed different from each other in the roller diameter thereof, whereby the wrong assembly of the tappet roller bearing can be prevented visually. For example, as shown in
Also, as shown in
Also, according to the present embodiment, there can also be employed a structure in which both bearings are constituted of plain bearings and, there can also be employed in a structure which includes such first to third rollers as shown in
Here, the invention is not limited to the above-mentioned embodiments but it can be changed properly without departing from the subject matter of the invention.
In the above embodiments, there is illustrated an example in which the tappet roller bearing 10 is mounted on the leading end portion of the locker arm 4. However, as shown in
Here, the invention is based on the Japanese Patent Application (Patent Application No. 2010-055650) filed on Mar. 12, 2010 and the Japanese Patent Application (Patent Application No. 2011-006244) filed on Jan. 14, 2011 and thus the contents thereof are incorporated herein for reference.
MODE FOR IMPLEMENTING THE INVENTION
- 1: Cam follower apparatus
- 2: Cam shaft
- 3a, 3b: Cam
- 4, 40: Locker arm
- 9: Support wall portion
- 10: Tappet roller bearing
- 11: First roller (plain bearing)
- 11a: First roller (plain bearing, outer roller)
- 12: Second roller (outer race of roller bearing)
- 12a: Second roller (plain bearing)
- 12b: Second roller (plain bearing, outer roller)
- 16: Third roller (plain bearing)
- 16a: Third roller (plain bearing, outer roller)
- 16b: Third roller (outer race of roller bearing)
- 20: Support shaft
Claims
1. A tappet roller bearing, comprising:
- a support shaft to be fixed to a locker arm for receiving the movement of a cam to be supported on the cam shaft of an engine; and
- first and second rollers respectively supported rotatably on the periphery of the support shaft and arranged in the axial direction of the support shaft, wherein:
- the first roller constitutes a plain bearing; and
- the second roller constitutes a full type roller bearing or a plain bearing.
2. The tappet roller bearing according to claim 1, wherein:
- the cam includes a high speed cam and a low speed cam respectively disposed on the cam shaft slidably in the axial direction of the cam shaft;
- the first roller constituting the plain bearing is contacted with the high speed cam; and
- the second roller constituting the full type roller bearing is contacted with the low speed cam.
3. The tappet roller bearing according to claim 1, wherein:
- the cam includes a high speed cam and a low speed cam respectively disposed on the cam shaft slidably in the axial direction of the cam shaft;
- the outer peripheral surface of the first roller to be contacted with the high speed cam is formed by barrel working to be carried out after polish finishing; and
- the outer peripheral surface of the second roller to be contacted with the low speed cam is formed by polish finishing without being barrel worked.
4. The tappet roller bearing according to claim 1, wherein
- the outer peripheral surfaces of the first and second rollers are not crowning worked but have a uniform diameter in the axial direction thereof.
5. The tappet roller bearing according claim 1, wherein
- at least one of the first and second rollers is structured so that an axial direction end face has a convex shape.
6. The tappet roller bearing according to claim 5, wherein:
- at least one of the first and second rollers, the axial direction end face of which is formed to have the convex shape, constitutes a double roller; and
- the inner roller of the double roller is structured so that an axial direction end face has a convex shape.
7. The tappet roller bearing according to claim 5, wherein:
- the second roller constitutes a full type roller bearing; and
- the multiple rollers of the roller bearing, together with the second roller, are structured so that respective axial direction end faces have a convex shape.
8. The tappet roller bearing according to claim 1, wherein:
- the support shaft is formed to have a staged shape including first and second shaft portions different from each other in the outside diameter dimension thereof;
- the first roller is disposed on the periphery of the first shaft portion; and
- the second roller is disposed on the periphery of the second shaft portion.
9. The tappet roller bearing according to claim 1, wherein
- the first and second rollers are different from each other in the axial direction width thereof
10. The tappet roller bearing according to claim 1, wherein
- the first and second rollers are different from each other in the roller diameter thereof
11. The tappet roller bearing according to claim 1, further comprising
- a third roller rotatably supported on the periphery of the support shaft and arranged together with the first and second rollers in the axial direction of the support shaft.
12. The tappet roller bearing according to claim 1, further comprising
- a third roller rotatably supported on the periphery of the support shaft and arranged together with the first and second rollers in the axial direction of the support shaft, wherein
- in a case that the second roller constitutes a roller bearing, the third roller is situated on the opposite side to the second roller with respect to the first roller.
13. The tappet roller bearing according to claim 11, wherein the outer peripheral surface of at least one of the first to third rollers is crowning worked.
Type: Application
Filed: Jan 18, 2011
Publication Date: Dec 20, 2012
Applicant: NSK LTD. (Tokyo)
Inventors: Tomohiro Kudo (Gunma), Satoshi Hachisuka (Gunma)
Application Number: 13/060,206
International Classification: F01L 1/14 (20060101);