US20130291817A1

US20130291817A1 - Cam follower apparatus

Info

Publication number: US20130291817A1
Application number: US13/824,718
Authority: US
Inventors: Hiroshi Noda; Satoshi Hachisuka
Original assignee: NSK Ltd
Current assignee: NSK Ltd
Priority date: 2012-01-19
Filing date: 2012-08-28
Publication date: 2013-11-07
Also published as: CN103635663A; EP2806117A1; JP2013167236A; KR20140015562A; WO2013108433A1

Abstract

Provided is a cam follower apparatus that has excellent durability, assembly characteristics and freedom of design, and together with being able to reduce the size and weight, is able to reduce the manufacturing cost. Both end sections of a support shaft 3 a are inserted into support holes 15 b, 15 c in support wall sections 12 b, 12 c, and the support shaft 3 a is supported by the support wall sections 12 b, 12 c such that relative rotation is possible. An inner ring 16, having an outer diameter D₁₆that is greater then the inner diameter d₁₅of the support holes 15 b, 15 c, is fitted around the outer circumferential surface of the middle section in the axial direction of the support shaft 9 a so as to be able to rotate together with the support shaft 9 a. Moreover, a plurality of cylindrical rollers 13 are arranged between an inner-ring raceway 17, which is formed around the outer circumferential surface of the inner ring 16, and an outer-ring raceway 18, which is formed around the inner circumferential surface of a tappet roller 8 b that is provided on the outer-diameter side of the inner ring, so as to be able to roll freely.

Description

TECHNICAL FIELD

The present invention relates to a cam follower apparatus that is assembled in a valve mechanism in the engine of an automobile and the like.

BACKGROUND ART

A cam follower apparatus such as disclosed in JP 2006-183856 (A), JP 2005-326023 (A) and the like has been widely used as a valve mechanism for transmitting the motion of a cam that is fastened to a camshaft that rotates in synchronization with the crankshaft of an engine to a valve. FIG. 12 and FIG. 13 illustrate an example of conventional construction of a cam follower apparatus as disclosed in JP 2006-183856 (A). A rocker arm 1, which is the main part of the cam follower apparatus is supported so as to be able to rotate freely by the cylinder head (not illustrated in the figure) of the engine by way of a rocker shaft 3 that is inserted into a shaft hole 2 that is formed in the middle section in the lengthwise direction thereof. Moreover, by screwing an adjustment bolt 4 into a screw hole that is formed in the base end section (left end section in FIG. 12) of the rocker arm 1, and then tightening a locking nut 5, the adjustment bolt 4 is fastened the base end section of the rocker arm 1. The base end surface (top end surface in FIG. 12) of an engine valve 6, which is an air-intake valve or exhaust valve, that is supported by the cylinder head so as to be able to move back-and-forth comes in contact with the tip-end surface (bottom surface in FIG. 12) of the adjustment bolt 4. The engine valve 6 is always forced by a return spring 7 in closed-valve direction (direction of contact with the adjustment bolt 4). Therefore, an elastic force in the clockwise direction around the rocker shaft 3 in FIG. 12 is applied to the rocker arm 1.
On the other hand, a tappet roller 8 is supported on the tip-end section (right end section in FIG. 12) of the rocker arm 1 by way of a support shaft 9 so as to be able to rotate freely, and the outer circumferential surface of the tappet roller 8 comes in contact with the outer circumferential surface of the cam 10 due to the elastic force of the return spring 7. A cam 10 is integrally formed with a camshaft 11 that rotates in conjunction with the crankshaft (not illustrated in the figure) and is supported by the cylinder head so as to be able to rotate freely. With this kind of construction, the rotation of the camshaft 11 is converted to back-and-forth rocking motion of the rocker arm 1 that is centered around the rocker shaft 2, and the engine valve 6 is caused to move back-and-forth in the axial direction by the rocker arm 1 against the elastic force or due to the elastic force of the return spring 7. This performs the opening/closing operation of the air-intake port or exhaust port that is provided at the top of the cylinder of the engine.
In this kind of valve mechanism, the portion that supports the tappet roller 8 by way of the support shaft 9 so as to be able to rotate freely with respect to the rocker arm 1 is constructed as illustrated in FIG. 13. The support arm 9 spans between a pair of support wall sections 12 that are provided on the tip-end section of the rocker arm 1 so as to be parallel with each other and separated by a space. The tappet roller 8 is supported by a radial roller (needle) bearing 14 that comprises a plurality of cylindrical rollers (needles) 13 so as to be able to rotate freely around a portion in the middle section of the support shaft 9 that is located between the inside surfaces of the support wall sections 12. Both end sections of the support shaft 9 fit inside and are supported by circular support holes 15 that are provided in the support wall sections 12 so as to be concentric with each other. In this state, by causing the outer circumferential edge sections on both ends of the support shaft 9 to plastically deform by bringing the tip-end edge of a crimping jig such as a punch in contact with a portion near both end surfaces of the support shaft 9, the support shaft 9 is firmly connected and fastened to the support holes 15. It is also possible to omit the radial roller bearing 14 and employ single-roller construction or double-roller construction that allows for relative rotation of cylindrical members between the inner circumferential surface of the tappet roller and the outer circumferential surface of the support shaft. This kind of construction is disclosed in JP 2005-326023 (A), so a detailed explanation will be omitted here.
In the case of the first example of conventional construction illustrated in FIG. 12 and FIG. 13, the middle section in the lengthwise direction of the rocker arm functions as a fulcrum, and the tappet roller 8 and adjustment bolt 4 for driving the engine valve 6 are provided on both end sections. On the other hand, as illustrated in FIG. 14 and FIG. 15, JP 2009-079569 (A) discloses construction in which a tappet roller 8 a is supported by a radial roller bearing 14 so as to be able to rotate freely around a support shaft 9 a that is fastened to the middle section in the lengthwise direction of the rocker arm 1 a. Both end section of the support shaft 9 a are fitted inside and supported by circular support holes 15 a that are provided in a pair of support wall sections 12 so as to be concentric with each other. In the case of this second example of conventional construction, in the state of being assembled in the engine, the tip-end section of a lash adjuster, which is the fulcrum, comes in contact with one surface on one end section (bottom surface on the left end section in FIG. 14 and FIG. 15) of the rocker arm 1 a, and the base end surface of the engine value comes in contact with one surface on the other end section (bottom surface of the right end section in FIG. 14 and FIG. 15).
In the case of either construction, the outer circumferential surface in the middle section of the support shaft 9 (9 a) functions as an inner-ring raceway of the radial roller bearing 14 for supporting the tappet roller 8 (8 a) so as to be able to rotate freely, so preferably this outer circumferential surface in the middle section will not be damaged. Moreover, construction in which the support shaft 9 (9 a) is press fitted into the support holes 15 (15 a) that are formed in the support wall sections 12 (12 a) is disadvantageous from the aspect of preventing damage. Therefore, in order to prevent damage to the outer circumferential surface of the middle section of the support shaft 9 (9 a), hardening of the entire support shaft 9 (9 a) is performed by immersion quenching in which the entire support shaft 9 (9 a) is heated and then immersed in oil for quenching. However, in the case of immersion quenching, the entire support shaft 9 (9 a) becomes hard, so when crimping both end section of the support shaft 9 (9 a), the tip-end section of the jig, such as a punch, that is pressed against both end surfaces of the support shaft 9 (9 a) could be damaged, and thus frequent replacement may be necessary. As a result, processing cost increases, and there is a possibility that the cost for manufacturing the cam follower apparatus will increase.
In regards to this problem, raw portions (unquenched portions) on both end sections of the support shaft 9 (9 a) are left, and hardening is performed for only the outer circumferential surface of the middle section with induction hardening. However, induction hardening itself is a cause for the processing cost to increase. Moreover, even with both end sections of the support shaft 9 (9 a) raw, the durability of the jig that is used in the work for crimping and expanding both end sections is limited, and is not connected to suppressing the processing cost, so even though induction hardening is performed, it is not completely possible to sufficiently suppress the manufacturing cost of the cam follower apparatus.
Moreover, in the cam follower apparatus having conventional construction, often, in order to maintain load capacity, a full complement roller bearing that does not have a cage is used as the radial roller bearing that is provided between the inner circumferential surface of the tappet roller 8 (8 a) and the outer circumferential surface in the middle section of the support shaft 9 (9 a). In the case of assembling a cam follower apparatus having this kind of construction, first, a roller assembly in which a plurality of cylindrical rollers are arranged is assembled in the space between the inner circumferential surface of the tappet roller 8 (8 a) and the outer circumferential surface of a shaft member (detent plug) that is located on the inner-diameter side of the tappet roller 8 (8 a).
Next, the roller assembly is placed between the inside surfaces in the width direction of the support wall sections 12 (12 a) with both end surfaces of the detent plug and the support holes 15 (15 a) in the support wall sections 12 (12 a) in an aligned state. Next, the support shaft 9 (9 a) is inserted from the outside in the axial direction of one of the support wall sections 12 (12 a) into the support hole 15 (15 a) of one support wall section 12 (12 a) of the support wall sections 12 (12 a). Then, while pressing the detent plug with the support shaft 9 (a), the support shaft 9 (9 a) is inserted until one end section thereof is inserted into the support hole 15 (15 a) in the other support wall section 12 (12 a). Furthermore, both end section of the support shaft 9 (9 a) are crimped and expanded. In this state, the support shaft 9 (9 a) is supported in a state wherein relative rotation with respect to the support wall sections 12 (12 a) is prevented. In the case of this kind of construction, the work of inserting the support shaft 9 (9 a) into the inner-diameter side of the tappet roller 8 (8 a) while pressing the detent plug is troublesome. Moreover, the number of parts for assembly and the number of assembly steps increase because of the use of the detent plug, so the cost increases.
The outer diameter of the support shaft 9 (9 a) and the inner diameter of the support holes 15 (15 a) in the support wall sections 12 (12 a) are set based on the diameter of the inscribed circle of the cylindrical rollers 13 of the radial roller bearing 14. Therefore, the freedom of design of the support shaft 9 (9 a) and the support wall sections 12 (12 a) is low. Furthermore, when the diameter of the inscribed circle of the cylindrical rollers 13 of the radial roller bearing 14 is large, it is necessary to make the overall diameter of the support shaft 9 (9 a) large in order to correspond to the diameter of the inscribed circle. Due to this, the weight thereof may be increased. In addition, the support shaft 9 (9 a) is supported in a state wherein relative rotation with respect to the support wall sections 12 (12 a) is prevented, so load zone of the support shaft 9 (9 a) is limited to a fixed range. In other words, radial loads that are applied during use are always applied (supported) in the same location of the support shaft 9 (9 a). As a result, repeated loading is applied to the portion of the support shaft 9 (9 a) where radial loading is applied, and there is a possibility of a decrease in durability. All of the related technical literature described above is incorporated into this specification by reference.

RELATED LITERATURE

Patent Literature

[Patent Literature 1] JP 2006-183856 (A)
[Patent Literature 2] JP 2005-326023 (A)
[Patent Literature 3] JP 2009-079569 (A)

SUMMARY OF THE INVENTION

Problem to be Solved by the Invention

In consideration of the problems described above, it is the object of the present invention to achieve construction of a cam follower apparatus that has excellent durability, assembly characteristics, and freedom of design, is capable of being made compact and lightweight, and is capable of reducing the manufacturing cost thereof.

Means for Solving the Problems

The cam follower apparatus of the present invention has a rocker arm, a support shaft, an inner ring member and a tappet roller. The rocker arm has a pair of support wall sections that are provided so as to be separated from each other by a space, and a pair of support holes that are formed in positions in these support wall sections that are aligned with each other, and is provided so as to face a cam that is fastened to a camshaft that rotates in synchronization with the crankshaft of an engine and oscillates and displaces according to the motion of this cam. Moreover, the support shaft, with both ends sections thereof inserted in the pair of support holes, spans between the pair of support wall sections and is supported by the support wall sections. The inner ring member has an outer diameter that is larger than the inner diameter of the support holes, and fits with an interference fit onto the middle section in the axial direction of the support shaft in a state such that relative rotation with respect to the support shaft is prevented. Furthermore, the tappet roller is arranged around the inner ring member so as to be able to rotate relative to the inner ring member.
Preferably, both end sections of the support shaft fit with a loose fit inside the pair of support holes so as to be able to rotate on the inside of the support holes. Preferably, a radial roller bearing is provided between the inner circumferential surface of the tappet roller and the outer circumferential surface of the inner ring member. In this case, it is preferable that the radial roller bearing be a full complement roller bearing that does not have a cage.
Preferably, in the case where the radial roller bearing is a full complement roller bearing, a pair of circular ring shaped washers are provided on the inside in the width direction of the pair of support wall sections so as to cover the opening sections on both ends of a bearing space of the radial roller bearing. In this case, the outer diameter of the washers is greater than the dimension in the height direction of the support wall sections.
As the construction of the cam follower apparatus of the present invention, it is possible to employ double roller construction in which the inner circumferential surface of the tappet roller comes in sliding contact with the outer circumferential surface of the inner ring member. Functionally, this case is the same as single roller construction. Alternatively, it is possible to employ triple roller construction in which a cylindrical member is located between the inner circumferential surface of the tappet roller and the outer circumferential surface of the inner ring member so as to be able to rotate relative to the tappet roller and the inner ring member. Functionally, this case is the same as double roller construction.

Effect of the Invention

With the present invention, it is possible to achieve construction of a cam follower apparatus having excellent durability, assembly characteristics and freedom of design, and that is capable of reduced size and weight as well as reduced manufacturing cost.
An improvement in durability is due to performing hardening of the entire support shaft by immersion quenching. In the present invention, it is not necessary to crimp both end sections of the support shaft, so it is possible hardening of the support shaft by immersion quenching. As a result, it is possible to maintain sufficient strength and rigidity of the entire support shaft, and to effectively prevent the support shaft from plastically deforming due to radial loading during use.
Moreover, in the case of supporting the support shaft so as to be capable of relative rotation with respect to the support wall sections, the load zone of the support shaft is not limited to a fixed range. As a result, it is possible to prevent loads from being applied to the same location of the support shaft, and thus it is possible to increase the life of the support shaft.
Furthermore, even in the case of constructing the radial bearing using a full complement roller bearing, by providing a pair of circular ring shaped washers, the inside surfaces in the width direction of the support wall sections are prevented from rubbing against the cylindrical rollers, so it is possible to increase the life of the support wall sections.
In addition, by reducing the dimension in the height direction of the support wall sections, it is possible to reduce the surface area of the portion where the inside surfaces in the width direction of the support wall sections overlap both end surfaces in the axial direction of the tappet roller in the axial direction, and it becomes easier for lubrication oil to penetrate from the outside into the internal space (bearing space) of the radial roller bearing.
Improvement of the assembly characteristics is made possible by providing the inner ring member. In other words, with a roller assembly in which an inner ring member, tappet roller and other components (for example, cylindrical rollers of a radial roller bearing) are assembled arranged between the support wall sections, it is possible to perform assembly by inserting the support shaft in order through the support hole of one support wall section, the inner circumferential surface of the inner ring member and the support hole of the other support wall section. Therefore, there is no need to assemble the support shaft by inserting and pressing out a detent plug that was located on the inside of the tappet roller as was done in the conventional construction.
Improvement of the freedom of design as well is made possible by proving the inner ring member. In other words, the outer diameter of the inner ring member can be appropriately set to correspond to the diameter of the inscribed circle of the cylindrical rollers of the radial roller bearing, and to set the inner diameter of the inner ring member to correspond with the outer diameter of the support shaft and the inner diameter of the support holes in the support wall sections.
Reduction in the size and weight is also made possible by providing the inner ring member. In other words, by changing the inner diameter of the inner ring member, it is possible to reduce the outer diameter of the support shaft, so together with being able to keep the width dimension around the support holes in the support wall sections in the radial direction of the support holes at a fixed width, it is possible to reduce the dimension in the height direction of the support wall sections. As a result, it is possible to maintain a desired rigidity, and to reduce the size and weight of the support wall sections and the entire rocker arm.
Moreover, in the case of providing a pair of circular ring shaped washers, these washers are able to prevent the cylindrical rollers of the radial roller bearing from coming out in the axial direction from the bearing space, so it is possible to further reduce the dimension in the height direction of the support wall sections.
Reduction of the manufacturing cost is possible in that there is no need to perform crimping work, it is possible to perform hardening of the support shaft by immersion quenching, and there is no need for a detent plug.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing illustrating a first example of an embodiment of the present invention, and corresponds to the section A-A in FIG. 12 and section B-B in FIG. 14.

FIG. 2 is a drawing illustrating a second example of an embodiment of the present invention, and is similar to FIG. 1.

FIG. 3 is a drawing illustrating a third example of an embodiment of the present invention, and is similar to FIG. 1.

FIG. 4 is a drawing illustrating a fourth example of an embodiment of the present invention, and is similar to FIG. 1.

FIG. 5 is a drawing as seen from the side in FIG. 4.

FIG. 6 is a drawing illustrating a fifth example of an embodiment of the present invention, and is similar to FIG. 1.

FIG. 7 is a drawing as seen from the side in FIG. 6.

FIG. 8 is a drawing illustrating a sixth example of an embodiment of the present invention, and is similar to FIG. 1.

FIG. 9 is a drawing as seen from the side in FIG. 8.

FIG. 10 is a drawing illustrating a seventh example of an embodiment of the present invention, and is similar to FIG. 1.

FIG. 11 is a drawing as seen from the side in FIG. 10.

FIG. 12 is a drawing illustrating a first example of a cam follower apparatus having conventional construction.

FIG. 13 is an enlarged cross-sectional drawing of section C-C in FIG. 12.

FIG. 14 is a side view illustrating a second example of a cam follower apparatus having conventional construction.

FIG. 15 is a drawing as seen from the top in FIG. 14.

MODES FOR CARRYING OUT THE INVENTION

First Example

FIG. 1 illustrates a first example of an embodiment of the present invention. Features of the cam follower apparatus of the present invention, including this example, are the construction of support wall sections 12 b, 12 c that support a support shaft 9 b, and providing an inner ring 16, which is an inner-ring member, between the support shaft 9 b and the tappet roller 8 b. The construction of the cam follower apparatus other than that of the features of the present invention, and the assembled state in an engine is the same as in conventional construction, including that illustrated in FIG. 12 to FIG. 15, so an explanation thereof is omitted or simplified, so that explanation below centers on the features of this example.
The cam follower apparatus of this example has a rocker arm 1 b, a support shaft 9 b, an inner ring 16, which is an inner-ring member, a tappet roller 8 a and a plurality of cylindrical rollers 13. The rocker arm 1 b has a pair of support wall sections 12 b, 12 c that are provided in a state being separated by an interval from each other, and a pair of support holes 15 b 15 c is formed in positions in these support wall sections 12 b, 12 c that are aligned with each other. In the case of the cam follower apparatus of this example, both end sections of a hollow or solid steel support shaft 9 b are inserted into support holes 15 b, 15 c in steel support wall sections 12 b, 12 c by way of a minute gap (loose fit), and by spanning between the support wall sections 12 b, 12 c, the support shaft 9 b is supported such that relative rotation with respect to the support wall sections 12 b, 12 c is possible. In other words, the outer diameter D₉of the support shaft 9 b is a little less than the inner diameter d₁₅of the support holes 15 b, 15 c (D₉<d₁₅).
In order to sufficiently maintain the strength and rigidity of the overall support shaft 9 b, the support shaft 9 b is entirely hardened by immersion quenching in which the entire support shaft 9 b is heated and immersed in quenching oil. However, in hardening by immersion quenching, the processing cost becomes high, however, it is also possible to harden the support shaft 9 b by induction hardening in which in the outer circumferential surface in the middle section is hardened and raw portion remain on both end sections of the support shaft 9 b. Moreover, by performing hardening such as quenching on inner circumferential surfaces of the support holes 15 b, 15 c, it is possible to prevent the occurrence of damage such as wear to the areas of rubbing between the inner circumferential surfaces of the support holes 15 b, 15 c and the outer circumferential surface of both end sections of the support shaft 9 b. Furthermore, it is possible to provide a ring shaped sliding bearing member between the outer circumferential surface on both end sections of the support shaft 9 b and the inner circumferential surfaces of the support holes 15 b, 15 c. On the other hand, in this example, it is also possible to employ construction that prevents rotation of the support shaft 9 b with respect to the support wall sections 12 b, 12 c by press fitting (fit using an interference fit) both end sections of the support shaft 9 b into the support holes 15 b, 15 c in the support wall sections 12 b, 12 c.
A cylindrical shaped inner ring 16 is fitted onto the outer circumferential surface of the middle section in the axial direction of the support shaft 9 b with an interference fit so as to be prevented from relative rotation with respect to the support shaft 9 b (state in which it is possible to rotate together with the support shaft 9 b). The outer diameter D₁₆of the inner ring 16 is greater than the inner diameter d₁₅of the support holes 15 b, 15 c (D₁₆>d₁₅). In this way, it is possible to prevent the support shaft 9 b from coming out in the axial direction with respect to the support wall sections 12 b, 12 c. It is also possible to provide a large-diameter section that protrudes in the radial direction around the middle section in the axial direction of the support shaft, and to have this large-diameter section function as an inner ring member.
An inner-ring raceway 17 is formed around the outer circumferential surface of the inner ring 16. Moreover, a tappet roller 8 b is arranged concentrically around (on the outer diameter side of) the inner ring 16 such that relative rotation with respect to the inner ring 16 is possible. An outer-ring raceway 18 is formed around the inner circumferential surface of the tappet roller 8 b. A radial roller bearing 14 a is formed by arranging a plurality of cylindrical rollers 13 between the inner-ring raceway 17 and the outer-ring raceway 18. In this example, the radial roller bearing 14 a is composed of a full complement roller bearing in which no cage is provided, however, it is also possible to use cylindrical rollers with a cage as the cylindrical rollers.
When assembling the cam follower apparatus of this example, first, a roller assembly 19 in which the plurality of cylindrical rollers 13 are arranged is assembled in the space (bearing space 21) between the inner circumferential surface of the tappet roller 8 b and the outer circumferential surface of the inner ring 16 that is provide on the inner-diameter side of the tappet roller 8 b. Next, the roller assembly 19 is placed between the inside surfaces in the width direction of the support wall sections 12 b, 12 c in a state where the opening sections on both end sections in the axial direction of the inner circumferential surface of the inner ring 16 and the support holes 15 b, 15 c in the support wall sections 12 b, 12 c are aligned. Then, the support shaft 9 b is inserted through the support hole 15 b in one support wall section 12 b of the support wall sections 12 b, 12 c from the outside in the width direction of that one support wall section 12 b. While pressing the inner circumferential surface of the inner ring 16, the support shaft 9 b is further pressed until one end section thereof (left end section in FIG. 1) is inserted into the support hole 15 c in the other support wall section 12 c. In this state, a minute gap is provided between the outer circumferential surface of both end sections of the support shaft 9 b and the inner circumferential surface of the support holes 15 b, 15 c in the support wall sections 12 b, 12 c. The assembly direction for assembling the support shaft 9 b can also be the opposite direction.
In the cam follower apparatus of this example, maintaining durability is achieved by performing a hardening process using immersion quenching on the entire support shaft 9 b. In other words, in the case of the cam follower apparatus of the present invention, by making the outer diameter D₁₆of the inner ring 16 greater than the inner diameter d₁₅of the support holes 15 b, 15 c in the support wall sections 12 b, 12 c, it is possible to prevent the support shaft 9 b from coming out in the axial direction with respect to the support wall sections 12 b, 12 c. Therefore, it is not necessary to crimp both end sections of the support shaft 9 b, and it is also not necessary to keep both end sections of the support shaft 9 b in the raw state (state in which hardening is not performed). Therefore, it is possible to perform hardening of the support shaft 9 b by immersion quenching, in which the entire support shaft 9 b is heated and then immersed in quenching oil. As a result, it is possible to sufficiently maintain the strength and rigidity of the entire support shaft 9 b, and to effectively prevent plastic deformation due to radial loading that the support shaft 9 b receives during use.
Moreover, in the cam follower apparatus of this example, the support shaft 9 b is supported in a state so as to be able rotate relative to the support wall sections 12 b, 12 c. Therefore, the load zone of the support shaft 9 b is not limited to a fixed range. In other words, the location on the support shaft 9 b where the radial load is applied during use is not always the same. As a result, it is possible to prevent repeated loading to the same location on the support shaft 9 b, and thus it is possible to increase the life of the support shaft 9 b.
In the cam follower apparatus of this example, improvement of the assembly characteristics is due to providing the inner ring 16. In other words, with the roller assembly 19 arranged between the support wall sections 12 b, 12 c, it is possible to assemble the support shaft 9 b by inserting the support shaft in order through the support hole 15 b in one support wall section 12 b, the inner circumferential surface of the inner ring 16 and the support hole 15 c in the other support wall section 12 c. Therefore, work to push a detent plug that is arranged on the inner-diameter side of the tappet roller 8 (8 a) (see FIG. 12 to FIG. 15) out by pressing the support shaft while inserting it thereinto as was done in the conventional construction is not necessary.
In the cam follower apparatus of this example, improvement of the freedom of design is also achieved by providing the inner ring 16. In other words, in the conventional construction, the outer diameter of the support shaft 9 (9 a) and the inner diameter of the support holes 15 (15 a) in the support wall sections 12 (12 a) are regulated by the diameter of the inscribed circle of the cylindrical rollers of the radial roller bearing 14. However, in the present invention, it is possible to appropriately set the outer diameter D₁₆of the inner ring 16 so as to correspond to the diameter of the inscribed circle of the cylindrical rollers 13 of the radial roller bearing 14 a, and to set the inner diameter d₁₆of the inner ring 16 so as to correspond to the outer diameter of the support shaft 9 b. As a result, it is possible to improve the freedom of design of the outer diameter of the support shaft 9 b, and the inner diameter of the support holes 15 b, 15 c of the support wall sections 12 b, 12 c.
As long as the support shaft 3 a and support wall sections 4 a, 4 b can be made more compact as the freedom of design improves in this way, it is possible to improve the lubrication performance of the radial roller bearing 14 a. In other words, as the diameter of the support shaft 3 a is reduced, the dimension H₁₂in the height direction of the support wall sections 12 b, 12 c can be reduced, and it is possible to reduce the area of overlapping portions with respect to the axial direction between the inside surfaces in the width direction of the support wall sections 12 b, 12 c and both end surfaces in the axial direction of the tappet roller 8 b. Therefore, it becomes easy for lubrication oil to penetrate from the outside through the portion between the inside surfaces in the width direction of the support wall sections 12 b, 12 c and both end surfaces in the axial direction of the tappet roller 8 b and enter inside the bearing space 21 where cylindrical rollers of the radial roller bearing are located.
In the cam follower apparatus of this example, reducing the size and weight are achieved by proving the inner ring 16. In other words, in order to maintain a desired rigidity of the support wall sections 12 b, 12 c, it is necessary to maintain a specified width dimension L₁₂of the support wall sections 12 b, 12 c around the support holes 15 b, 15 c with regard to the radial direction of the support holes 15 b, 15 c. In this example, by changing the inner diameter d₁₆of the inner ring 16, it is possible to reduce the outer diameter D₉of the support shaft 9 b. Therefore, it is possible to reduce the dimension H₁₂in the height direction (up-down direction in FIG. 1) of the support wall sections 12 b, 12 c, while keeping the width dimension of the support wall sections 12 b, 12 c around the support holes 15 b, 15 c with regard to the radial direction of the support holes 15 b, 15 c. As a result, it is possible to reduce the size and weight of the support wall sections 12 b, 12 c and the entire rocker arm 1 b.
Furthermore, in the construction of the cam follower apparatus of this example, crimping work is not necessary, and thus a jig such as a punch or the like for forming the crimped sections is not necessary. Moreover, the hardening process for hardening the support shaft 9 b is performed by immersion quenching, which is lower in cost than induction hardening. Furthermore, there is no need for a detent plug during assembly. As a result of these, it is possible to reduce the processing cost and parts cost, as well as it is possible to reduce the overall manufacturing cost of the cam follower apparatus.

Second Example

FIG. 2 illustrates a second example of an embodiment of the present invention. In the case of the cam follower apparatus of this example, the outer circumferential surface of the inner ring 16 a that is fitted around the outer circumferential surface of the middle section in the axial direction of the support shaft 9 b comes in sliding contact with the inner circumferential surface of the tappet roller 8 b that is provided in a state so as to be able to rotate relative to the inner ring 16 a. The shape and dimensions of the tappet roller 8 b are the same as in the first example of an embodiment.
In other words, the cam follower apparatus of this example has so-called double roller construction in which the radial roller bearing 14 a in the first example of an embodiment is omitted. However, the inner ring 16 a of the cam follower apparatus of this example is similar to the inner ring 16 of the first example of an embodiment in that the inner ring 16 a fits with an interference fit around the outer circumferential surface of the middle section in the axial direction of the support shaft 9 b in a state so as to be able to rotate together with the support shaft 9 b (prevented from relative rotation with respect to the support shaft 9 b). Therefore, from a functional aspect, the cam follower apparatus of this example functions as a so-called single-roller cam follower apparatus. The other construction, functions and effects of this example are the same as in the first example of an embodiment.

Third Example

FIG. 3 illustrates a third example of an embodiment of the present invention. In the case of the cam follower apparatus of this example, an inner-diameter side roller 20, which is a cylindrical member, is provided between the outer circumferential surface of the inner ring 16 that is fitted around the outer circumferential surface of the middle section in the axial direction of the support shaft 9 b and the inner circumferential surface of the tappet roller 8 b in a state so as to be able to rotate relative to the inner ring 16 and the tappet roller 8 b. The shape and dimensions of the tappet roller 8 b and inner ring 16 are the same as in the first example of an embodiment.
In other words, the cam follower apparatus of this example has so-called triple roller construction in which an inner-diameter side roller 20 is provided instead of the radial roller bearing 14 a of the first example of an embodiment. However, as in the first example of an embodiment, the inner ring 16 of the cam follower apparatus of this example is fitted around the outer middle section in the axial direction of the support shaft 9 b in a state such that relative rotation with respect to the support shaft 9 b is prevented (rotation with the support shaft 9 b is possible). Therefore, from a functional aspect, the cam follower apparatus of this example functions as a so-called double roller cam follower apparatus. The other construction, functions and effects of this example are the same as in the first example of an embodiment.

Fourth Example

FIG. 4 and FIG. 5 illustrate a fourth example of an embodiment of the present invention. In the case of the cam follower apparatus of this example, a pair of circular ring shaped washers 22 made using a hard metal or a synthetic resin is provided in the axial direction between the inside surfaces in the width direction of the pair of support wall sections 12 d, 12 e and both end surfaces in the axial direction of the inner ring 16. Moreover, the outer diameter D₂₂of the washers 22 is greater than the inner diameter d₈of the tappet roller 8 b (D₂₂>d₈). In other words, the washers 22 are provided in a state so as to cover the opening sections on both ends in the axial direction of the bearing space 21 where the cylindrical rollers 13 of the radial roller bearing 14 a are located. In this example, the diameter D₂₂of the washers 22 is greater than the dimension H_12din the height direction (up-down direction in FIG. 4 and FIG. 5) of the support wall sections 12 d, 12 e (D₂₂>H_12d).
With the cam follower apparatus of this example, it is possible to reduce the size and the weight more than with the construction of the first example of an embodiment. In other words, in the case of this example, with the washers 22, the opening section on both ends in the axial direction of the bearing space 21 are covered, and the cylindrical roller 13 are prevented from coming out in the axial direction from the bearing space 21. Therefore, there is no need to prevent the cylindrical rollers 13 from coming out in the axial direction by the support wall sections 12 d, 12 e. As a result, it is possible to reduce the dimension H_12din height direction of the support wall sections 12 d, 12 e, and it is possible to reduce the size and weight of the rocker arm, including the support wall sections 12 d, 12 e.
Moreover, in the case of this example, the washers 22 cover the opening sections on both ends in the axial direction of the bearing space 21. Therefore, wear due to the inside surfaces in the width direction of the support wall sections 12 d, 12 e rubbing against the rollers 13 of the radial roller bearing 14 a is prevented, and thus it is possible to increase the life of the support wall sections 12 d, 12 e. The other construction, functions and effects of this example are the same as in the first example of an embodiment.

Fifth Example

FIG. 6 and FIG. 7 illustrate a fifth example of an embodiment of the present invention. In the case of the cam follower apparatus of this example, the dimension L_16bin the axial direction of the inner ring 16 b is larger than the dimension L₁₆in the axial direction of the inner ring 16 (see FIG. 1) of the first example of an embodiment (L_16b>L₁₆). On the other hand, the shape and dimensions of the tappet roller 8 b are the same as in the first example of an embodiment. Therefore, both end sections in the axial direction of the inner ring 16 b are located further on the outside in the width direction than both end sections in the axial direction of the tappet roller 8 b.
Moreover, further on the inside in the width direction than the inside surfaces in the width direction of the support wall sections 12 d, 12 e, a pair of circular ring shaped washers 22 a are provided on both end sections in the axial direction of the outer circumferential surface of the inner ring 16 b (portions further on the outside in the width direction than both end surfaces in the axial direction of the tappet roller 8 b). The outer diameter D_22aof the washers 22 a is larger than the inner diameter d₈of the tappet roller 8 b (D_22a>d₈). Therefore, the washers 22 a are provided in a state so as to cover the opening sections on both ends in the axial direction of the bearing space 21 in which the cylindrical rollers 13 of the radial roller bearing 14 b are located.
In this example as well, the outer diameter D_22aof the washers 22 a is larger than the dimension H_12din the height direction (up-down direction in FIGS. 6 and 7) of the support wall sections 12 d, 12 e (D_22a>H_12d). The other construction, functions and effect of this example are the same as in the fourth example of an embodiment.

Sixth Example

FIG. 8 and FIG. 9 illustrate a sixth example of an embodiment of the present invention. In the case of the cam follower apparatus of this example, the dimension L_8cin the axial direction of the tappet roller 8 c is greater than the dimension L₈in the axial direction of the tappet roller 8 b in the first example of an embodiment (L_8c>L₈). On the other hand, the shape and dimensions of the inner ring 16 are the same as in the first example of an embodiment. Therefore, both end sections in the axial direction of the tappet roller 8 c are located further on the outside in the width direction than both end sections in the axial direction of the inner ring 16.
Moreover, on the inner diameter side of both end sections in the axial direction (in portions further on the outside in the width direction than both end surfaces in the axial direction of the inner ring 16) of the tappet roller 8 c, and between the inside surfaces in the width direction of the support wall sections 12 d, 12 e and the both end sections in the axial direction of the inner ring 16 with regard to the axial direction of the outer circumferential surface of the support shaft 9 b, a pair of circular ring shaped washers 22 b are provided. The outer diameter D_22bof the washers 22 b is a little less than the inner diameter d₈of the tappet roller 8 c (D_22b<d₈). In other words, the washers 22 b are provided in a state so as to cover the opening sections on both ends in the axial direction of the bearing space 21 in which the cylindrical rollers 13 of the radial roller bearing 14 are located.
In the case of this example as well, the outer diameter D_22bof the washers 22 is greater than the dimension H_12din the height direction of the support wall sections 12 d, 12 e (D_22b>H_12d). The other construction, functions and effects of this example are the same as in the fourth example of an embodiment.

Seventh Example

FIG. 10 and FIG. 11 illustrate a seventh example of an embodiment of the present invention. In the case of the cam follower apparatus of this example, the inner ring 16 b of the fifth example of an embodiment (see FIG. 6), and the tappet roller 8 c of the sixth example of an embodiment (see FIG. 8) are combined to form a radial roller bearing 14 d. In other words, in this example, the dimension L_8cin the axial direction of the tappet roller 8 c is greater than the dimension L₈in the axial direction of the tappet roller 8 b of the first example of an embodiment (L_8c>L₈), and the dimension L_16bin the axial direction of the inner ring 16 b is greater than the dimension L₁₆in the axial direction of the inner ring (see FIG. 1) of the first example of an embodiment (L16 b>L16). The dimension in the axial direction of the tappet roller and inner ring can be the same as in the first example of an embodiment, and the dimension in the axial direction of the cylindrical rollers can be less than that of the cylindrical rollers 13 of the first example of an embodiment (see FIG. 1).
Moreover, a pair of circular ring shaped washers 22 c are provided between both end sections in the axial direction of the outer circumferential surface of the inner ring 16 b and both end sections in the axial direction of the inner circumferential surface of the tappet roller 8 c. In other words, the washers 22 c are provided in a state so as to cover the opening sections on both ends in the axial direction of the bearing space 21 in which the cylindrical rollers 13 of the radial roller bearing 14 d are located. In this example, it is also possible to use a cage instead of the washers 22 c.
In this example as well, the outer diameter D_22cof the washers 22 c is greater than the dimension H_12din the height direction (up-down direction in FIGS. 10 and 11) of the support wall sections 12 d, 12 e (D_22c>H_12d). The other construction, functions and effects of this example are the same as in the fourth example of an embodiment.

EXPLANATION OR REFERENCE NUMBERS

1, 1 a, 1 b Rocker arm
2 Shaft hole
3 Rocker shaft
4 Adjustment bolt
5 Locking nut
6 Engine value
7 Return spring
8, 8 a, 8 b Tappet roller
9, 9 a, 9 b, 9 c Support shaft
10 Cam
11 Cam shaft
12, 12 a, 12 b, 12 c, 12 d, 12 e Support wall section
13 Cylindrical roller
14, 14 a, 14 b, 14 c, 14 d Radial roller bearing
15, 15 a, 15 b, 15 c, 15 d, 15 e Support hole
16, 16 a, 16 b Inner ring
17 Inner-ring raceway
18 Outer-ring raceway
19 Roller assembly
20 Inner-diameter side roller
21 Bearing space
22, 22 a, 22 b, 22 c Washer

Claims

What is claimed is:

1. A cam follower apparatus, comprising:

a rocker arm that has a pair of support wall sections that are provided so as to be separated from each other by a space, and a pair of support holes that are formed in positions in these support wall sections that are aligned with each other, and is provided so as to face a cam that is fastened to a camshaft that rotates in synchronization with the crankshaft of an engine and oscillates and displaces according to the motion of this cam;

a support shaft that, with both ends sections thereof inserted in the pair of support holes, spans between the pair of support wall sections and is supported by the support wall sections;

an inner ring member that has an outer diameter that is larger than the inner diameter of the support holes, and fits with an interference fit onto the middle section in the axial direction of the support shaft in a state such that relative rotation with respect to the support shaft is prevented; and

a tappet roller that is arranged around the inner ring member so as to be able to rotate relative to the inner ring member.

2. The cam follower apparatus according to claim 1, wherein both end sections of the support shaft fit with a loose fit into the pair of support holes so as to be able to rotate on the inside of the support holes.

3. The cam follower apparatus according to claim 1, wherein a radial roller bearing is provided between the inner circumferential surface of the tappet roller and the outer circumferential surface of the inner ring member.

4. The cam follower apparatus according to claim 3, wherein the radial roller bearing is a full complement roller bearing.

5. The cam follower apparatus according to claim 4, wherein a pair of circular ring shaped washers are provided on the inside in the width direction of the pair of support wall sections so as to cover the opening sections on both ends of a bearing space of the radial roller bearing, and have an outer diameter that is greater than the dimension in the height direction of the support wall sections.

6. The cam follower apparatus according to claim 1, wherein the inner circumferential surface of the tappet roller comes in sliding contact with the outer circumferential surface of the inner ring member.

7. The cam follower apparatus according to claim 1, wherein a cylindrical shaped member is located between the inner circumferential surface of the tappet roller and the outer circumferential surface of the inner ring member so as to be able to rotate relative to the tappet roller and the inner ring member.