This application claims priority to Japanese Patent Application No. 2004-310713, filed Oct. 26, 2004, which application is herein expressly incorporated by reference.
The present invention relates to a double row thrust needle roller bearings used in automatic transmissions, compressors for vehicle air conditioner, continuously variable transmissions, electric brakes and the like. Although “a needle roller” is classified in Japanese Industrial Standards (JIS) as “a cylindrical roller having a diameter less than 5 mm and a ratio of length/diameter of 3˜10”, the term “needle roller”, used herein, has a broader meaning without being limited to the definition of JIS. In other word, it should be appreciated that the term “needle roller” in this specification includes both “long cylindrical roller” and “cylindrical roller” defined in JIS.
The thrust needle roller bearing includes needle rollers, a cage and bearing ring(s). It has a structure of line contact between the needle roller and the bearing ring. It has an advantage that it exhibits high loading capacity as well as high rigidity despite of its small projected area. This is a reason that it is widely used as a thrust-load supporting part in mechanical apparatus such as automatic transmissions, air compressors for vehicle air conditioners, continuously variable transmissions, electric brakes and the like. In these industrial fields, the needle roller bearing is obliged to be used under severe conditions such as lean lubrication and high rotational speeds in order to pursue a light weight and small size bearing. Accordingly, the present applicant has proposed a prior art double row thrust needle roller bearing as shown in
The double row thrust needle roller bearing 51 has a plurality of needle rollers 52. Two annular cages 53 and 54 hold the needle rollers 52 at a predetermined pitch in the circumferential direction. The cages 53 and 54 are made of cold rolled steel plate (e.g. JIS SPC etc.) by press-forming. The cages 53 and 54 are formed with a plurality of rectangular pockets 55 and 56. Each pocket has a radial (longitudinal) length longer than the length “L” of the needle roller 52. Oppositely projecting roller holding portions 55a and 56a are formed on either longitudinal edges of each pocket 55 and 56 to hold the needle rollers 52 while sandwiching them in the thickness direction.
The needle rollers 52 include radially outer needle rollers 52a and radially inner needle rollers 52b. The outer and inner rollers 52a and 52b are arranged in a double row manner within the pockets 55 and 56. The double row arrangement enables the bearing to reduce the revolution velocity difference between outer and inner portions of the needle rollers. Thus, this reduces their slippage relative to the bearing rings (not shown). Accordingly, heat generation in the contacting portions is reduced. Also, surface damages and surface peeling are prevented.
As shown in
As shown in
The two cages 53 and 54 are laid one on top of the other and united by folding the radially outermost edge of the outer flat portion 54b upward, to form a caulked portion 57, and by folding the radially innermost edge of the inner flat portion 53d downward, to form a caulked portion 58. Thus, the two cages 53 and 54 are securely united by the caulked portions 57 and 58. Thus, they should not be separated during operation of the bearing.
In a condition in which two cages 53 and 54 are securely united, the thickness “T0” of the roller holding portions 55a and 56a is larger than the thickness “T1” and “T2” of the radially outer and inner flat portions.
The double row thrust roller bearing with its two cages 53 and 54 improves flow-in/flow-out ability of lubricant and thus prevent seizure of the bearing. Also, the durability of the bearing can be improved (see Japanese Laid-open Patent Publication No. 36849/2004).
While the double row thrust needle roller bearing of the prior art has the above mentioned advantages and is suitable for the minority variety/majority lot production, it is not suitable for the majority variety/minority lot production required to satisfy a recent trend of diversification of needs. This is due to the increase cost of manufacturing due to the increase of a ratio of die manufacturing cost etc. relative to processing cost.
It is, therefore, an object of the present invention to provide a double row thrust needle roller bearing which can suppress the differential slippage of the needle rollers under severe working conditions and improve its durability without increasing the processing cost for the majority variety/minority lot production.
According to the present invention, a double row thrust needle roller bearing comprises a plurality of needle rollers arranged with at least two rows in a radial direction. An annular cage is formed with a plurality of pockets to hold the needle rollers. Each pocket is formed as a rectangular configuration with a length of its radial side longer than that of each needle roller. A length of the pocket's circumferential side is larger than the diameter of each needle roller. Each needle roller is held within each pocket of the cage by nailed portions. The portions are formed near the radially extending side walls of the pockets at either side of each needle roller along its longitudinal direction by plastically deforming the cage at a substantially middle portion of the longitudinal length of the needle roller. Thus, each nailed portion overhangs into the pocket over the needle roller.
According to the present invention, due to the double row thrust needle roller bearing having a plurality of needle rollers arranged with at least two rows in a radial direction, and an annular cage formed with a plurality of pockets to hold the needle rollers with each pocket formed as a rectangular configuration having a length of its radial side longer than that of each needle roller and a length of its circumferential side larger than the diameter of each needle roller, and each needle roller is held within each pocket of the cage by nailed portions formed near the radially extending side walls of the pockets at either side of each needle roller along its longitudinal direction by plastically deforming the cage at a substantially middle portion of the longitudinal length of the needle roller so that each nailed portion overhangs into the pocket over the needle roller, the revolution velocity difference is reduced between the radially outer and inner portions of the needle rollers. Thus, it is possible to suppress the slippage of the needle rollers against the bearing ring surface. This reduces the heat generated at the contact portions between the structural elements so that surface damage and surface peeling are prevented. Accordingly, it is possible to provide a double row thrust needle roller bearing which can suppress the differential slippage of the needle rollers under severe working conditions and improve its durability without increasing the processing cost for the majority variety/minority lot production.
Preferably, the cage may be made by cutting soft metal material. This makes it possible to easily form the nailed portions by plastically deforming the soft metal material by using a caulking tool.
In addition, one nailed portion may be formed at one longitudinal side wall of each pocket corresponding to each needle roller. The length of each nailed portion may be set at 60% or more of the length of each needle roller. Two nailed portions may be formed at each longitudinal side wall of the pocket corresponding to each needle roller symmetrically with the other two nailed portions formed at the other longitudinal side wall of each pocket. The length of each nailed portion may be set at 15% or more of the length of each needle roller. In this case, recesses formed between the nailed portions enable the lubrication oil to easily pass therethrough.
A clearance between the needle roller and the pocket in the thickness direction of the cage may be larger than that in the circumferential direction. Accordingly, the needle rollers are firmly guided by the side walls of the pockets not by the inner walls of the nailed portions. Thus, it is possible to stabilize the motion of the needle rollers and to prevent absence of an oil film at the contact portions with the pockets.
According to the present invention, the revolution velocity difference between the radially outer and inner portions of the needle rollers is reduced. Thus, it is possible to suppress the slippage of the needle rollers against the bearing ring surface. This reduces the heat generation in the contact portions between the structural elements so that surface damage and surface peeling are prevented. Accordingly, it is possible to provide a double row thrust needle roller bearing which can suppress the differential slippage of the needle rollers under severe working conditions and improve its durability without increasing the processing cost for the majority variety/minority lot production.
A double row thrust needle roller bearing comprises a plurality of needle rollers arranged with at least two rows in a radial direction. An annular cage is formed with a plurality of pockets to hold the needle roller. Each pocket is formed in a rectangular configuration with a length of its radial side longer than that of each needle roller and a length of its circumferential side larger than the diameter of each needle roller. Each needle roller is held within each pocket of the cage by nailed portions. The nailed portions are formed near radially extending side walls of the pockets at either side of each needle roller along its longitudinal direction by plastically deforming the cage at a substantially middle portion of the longitudinal length of the needle roller. Thus, each nailed portion overhangs into the pocket over the needle roller.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims, taken in conjunction with the accompanying drawings, wherein:
FIGS. 8(b) and 8(c) are plan views of modified embodiments of
FIGS. 9(b) and 9(c) are plan views of modified embodiments of
FIGS. 10(b) and 10(c) are plan views of modified embodiments of
The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.
A preferred embodiment of the present invention will be hereinafter described with reference to accompanied drawings.
The double row thrust needle roller bearing 1 includes a plurality of needle rollers 2, and a cage 3 to hold the needle rollers 2 at a predetermined pitch in the circumferential direction. The cage 3 is made by cutting soft metal materials such as copper alloy; some examples are high tensile brass casting (JIS CAC 3 etc.), aluminum/bronze casting (JIS CAC 7 etc.), aluminum, aluminum alloy, or aluminum alloy casting. The cage 3 has a plurality of pockets 4 each formed as a rectangular configuration. Each pocket 4 has a length of its longitudinal (radial) side longer than that of each needle roller 2 and a length of its circumferential side larger than the diameter of each needle roller 2. The pockets 4 may be formed by stamping other than cutting.
The needle rollers 2 comprise radially outer and inner needle rollers 2a and 2b and are arranged within pockets 4 in a double row arrangement. The revolution velocity difference between the radially outer and inner needle rollers can be reduced by the double row arrangement of the needle rollers. Thus, slippage of each needle roller against a bearing ring surface (not shown) is suppressed. Accordingly, heat generated at the contacting portions is reduced and surface damages and surface peeling are also prevented. Although it is shown that radially outer needle rollers 2a and radially inner needle rollers 2b have the same length as each other, it is possible to make the length of the radially outer needle rollers longer than that of the radially inner needle roller. This increases the load supporting capacity of the radially outer needle rollers. Also, although it is shown that the end face of each needle roller 2a and 2b has a flat configuration (so-called “F” end face), other configurations e.g. spherical configuration (so-called “A” end face) or combination of “F” and “A” end faces may be used.
As shown in
If the length of the needle rollers 2a and 2b is more than 6 mm, two nailed portions 5 are formed at each longitudinal side wall 4a of the pocket 4 corresponding to each needle roller 2. The nailed portions are symmetrically formed with the other two nailed portions 5 formed at the other longitudinal side wall of each pocket 4. Accordingly, recesses formed between the nailed portions 5 enable lubrication oil to easily pass therethrough. In this case, since the strength of the nailed portions 5 would be insufficient if the length “Lw” of the nailed portions 5 is less than 15% of the length of the needle rollers 2a and 2b, it is preferable to set the length of nailed portions 5 at 15% or more of the length “Lw” of the needle rollers 2a and 2b.
Although the length of each needle roller 2a and 2b is larger than 6 mm, two nailed portions 5 (
According to the present embodiment, the double row needle rollers 2a and 2b are adapted to be held by the nailed portions 5. The nailed portions 5 are formed by plastically deforming the cage 3, which is manufactured from soft metal material such as high tensile brass casting or aluminum alloy. Thus, each nailed portion 5 overhangs into the pocket 4 over the needle roller 2. Thus, it is possible to provide a double row thrust needle roller bearing where the nailed portions 5 can be easily formed. Accordingly, the needle rollers 2 can be held with a simple structure and can suppress the differential slippage of the needle rollers under severe working conditions to improve its durability without increasing the processing cost for the majority variety/minority lot production.
It is important that the needle rollers 2 should never sink below the surface of the cage 3. Thus, a relationship between the needle roller 2a and the pocket 4 is established so that the needle roller 2a is guided by the longitudinal side walls 4a of the pocket 4, as shown in
In order to achieve extended life of the double row thrust needle roller bearing, it is possible to suppress heat generated at the bearing portion by optimizing the pocket gap to insure oil flow and by defining the motion (degree of freedom) of the needle roller 2a. When the roller guide portion and the roller stopper portion are formed by separate portions, as in the present embodiment, the optimized value of the pocket gap is set within a range of 0.05˜0.25 mm. The term “pocket gap” means a gap between the needle roller 2a and the one roller guide portion of the cage 3. This occurs when the needle roller 2a is contacted with the other roller guide portion of the cage 3 to keep the center of the needle roller 2a corresponding to the center in the thickness (height) direction.
The double row thrust needle roller bearing 6 comprises a plurality of needle rollers 7 and a cage 8 to hold the needle rollers 7 at a predetermined pitch in the circumferential direction. Similar to the first embodiment, the cage 8 is made by cutting soft metal materials such as copper alloy. Some examples are high tensile brass casting (JIS CAC 3 etc.), aluminum/bronze casting (JIS CAC 7 etc.), aluminum, aluminum alloy, or aluminum alloy casting (JIS AC etc.). The cage 8 has a plurality of pockets 9 each formed in a rectangular configuration with a length of its longitudinal (radial) side longer than that of each needle roller 7. A length of the pocket's circumferential side is larger than the diameter of each needle roller 7. The pockets 9 include double rows arranged in the same phase in a radially outer and inner directions.
As shown in
If the length of the needle roller 7 is more than 6 mm, two nailed portions 5 are formed at each longitudinal side wall 9a of the pocket 9 corresponding to each needle roller 2. The nailed portions 5 are symmetrically formed with the other two nailed portions 5 formed at the other longitudinal side wall of each pocket 9. The length “Lw” of the nailed portions 5 is set less than 15% of the length of the needle rollers 7. Although the length of each needle roller 7 is larger than 6 mm, two nailed portions 5 (
Also according to the second embodiment, the double row needle rollers 7 are adapted to be held by the nailed portions 5. The nailed portions 5 are formed by plastically deforming the cage 8, which is manufactured from soft metal material such as high tensile brass casting or aluminum alloy. Thus, each nailed portion 5 overhangs into the pocket 9 over the needle roller 7. Thus, it does not increase the processing cost for the majority variety/minority lot production. Contrary to the first embodiment, since one needle roller 7 is held by one pocket 9 in the second embodiment, it is possible to stably hold the needle roller 7 and to prevent skewing of the needle roller 7. Accordingly, it is possible to provide a double row thrust needle roller bearing which can suppress differential slippage of the needle rollers under severe working conditions to improve its durability.
A dimensional relation between the needle roller 7 and the pocket 9 is established so that the needle roller 7 is guided by the longitudinal side walls 9a of the pocket 9 as shown in
Although the double row thrust needle roller bearing of the present invention has been described with reference to those where the double row needle rollers are arranged in the same phase with each other, it can be applied to one having various needle roller arrangements.
The double row thrust needle roller bearing shown in
Such an arrangement of the double row radially outer and inner pockets 11a and 11b not only enables an increase of strength of the cage 10 but improves the flow of lubricant.
The radially outer pockets 11a do not necessarily need to be arranged at the middle of the radially inner pockets 11b. They may be arranged as shown in
The double row thrust needle roller bearing of
A double row thrust needle roller bearing shown in
A double row thrust needle roller bearing shown in
The double row thrust needle roller bearing of
A double row thrust needle roller bearing shown in
A double row thrust needle roller bearing shown in
The double row thrust needle roller bearing of
The double row thrust needle roller bearing of
The double row thrust needle roller bearing of
This double row thrust needle roller bearing includes a plurality of needle rollers 2 and 7 and an annular cage 26 to hold the needle rollers 2 and 7 at a predetermined pitch in the circumferential direction. The cage 26 has a plurality of pockets 4. Each pocket is formed as a rectangular configuration with a length of its longitudinal (radial) side longer than the length of the double row needle rollers 2 (including radially outer and inner needle rollers 2a and 2b). A length of the pockets circumferential side is larger than the diameter of each needle roller 2. Double row pockets 9 to hold needle rollers 7 are positioned between pockets 4.
According to the double row thrust needle roller bearing of the present invention, the double row needle rollers are adapted to be held by the nailed portions. The nailed portions are formed by plastically deforming the cage of soft metal material, such as high tensile brass casting or aluminum alloy. Thus, each nailed portion overhangs into the pocket over the needle roller. Thus, it is possible to provide a double row thrust needle roller bearing where the nailed portions can be easily formed. Accordingly, the needle rollers can be held with a simple structure. Also, the bearing can suppress differential slippage of the needle rollers under severe working conditions to improve its durability without increasing the processing cost for the majority variety/minority lot production.
The double row thrust needle roller bearing of the present invention can be incorporated into apparatus such as automatic transmissions, compressors of air conditioner, continuously variable transmissions, electric brakes etc. and can be used as a double row thrust needle roller bearing to support the thrust load applied to the apparatus. The bearing is especially suitable for a double row thrust needle roller bearing of majority variety/minority lot production.
The present invention has been described with reference to the preferred embodiments. Obviously, modifications and alternations will occur to those of ordinary skill in the art upon reading and understanding the preceding detailed description. It is intended that the present invention be construed as including all such alternations and modifications insofar as they come within the scope of the appended claims or their equivalents.
Number | Date | Country | Kind |
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2004-310713 | Oct 2004 | JP | national |