MXPA96001647A - Structure of bearing support of compensaciontermica for velocida box - Google Patents

Abstract

An improved structure that supports a bearing in a hole provided in a portion of a gearbox and prevents relative rotation between them. In a preferred embodiment, the clutch housing portion of a gearbox is made of aluminum and includes an inner wall having an orifice formed therein. A circumferential groove is formed in the side wall of the hole and a compressible or elastomeric O-shaped ring is placed in the groove. The bearing is made of steel and includes an inner race, an outer race and a plurality of rolls placed between the race rings.

Description

STRUCTURE OF THERMAL COMPENSATION BEARING SUPPORT FOR SPEED BOX BACKGROUND OF THE INVENTION This invention relates in general to vehicle transmissions and in particular to an improved structure for supporting a bearing with a vehicle gearbox. In most vehicles, a transmission is provided in the drive train, between the engine and the drive wheels. As is well known, the transmission includes a box containing an input shaft, an output shaft and a plurality of gear gears, which are selectively connected between the input shaft and the output shaft. The gear gears contained within the gearbox are of variable size such that they provide a plurality of speed reduction transmission ratios, between the input shaft and the output shaft. By the proper selection of these gear gears, a desired gear reduction ratio can be obtained between the input shaft and the output shaft. As a result, the acceleration and deceleration of the vehicle can be performed in a uniform and efficient manner.

Normally, this selection of the transmission ratio is made by moving one or more control members, provided inside the gearbox. The movement of the control member causes certain of the gear gears to be connected between the input shaft and the output shaft, to provide between them the desired transmission ratio. In a manual transmission, the movement of the control member is realized by the manual effort of the driver of the vehicle, such as by means of a speed lever. In an automatic transmission, the movement of the control member is performed by a pneumatic or hydraulic actuator, in response to the predetermined operating conditions. In many heavy and medium duty manual transmissions, the gearbox is divided into two or three parts. The front portion of the gearbox is usually referred to as the clutch housing. The clutch housing is dimensioned to extend over and securely enclose a manually operable clutch connected between the vehicle engine and the input shaft of the transmission. The central portion of the gearbox is usually referred to as the main housing. The main housing contains most of the axes, gears and other components, which are used to provide a set of transmission ratios to operate the transmission. In composite transmissions (ie, those transmissions which are formed of a first set of transmission ratios provided by a main section and one or more additional sets of gear ratios provided by an auxiliary section), the gearbox may include a posterior portion. The rear portion of the gearbox is usually referred to as the auxiliary housing and contains most of the shafts, gears and other components, which are used to provide the additional group or groups of transmission ratios provided by the auxiliary section. In a typical transmission, it is usually necessary to support the ends of one or more axes for rotation. To do this, it is known to form some of the portions of the gearbox with cylindrical holes or recesses and to provide annular bearings within such holes to rotatably support the ends of the shafts. A typical annular bearing includes an inner race, an outer race and a plurality of rollers, such as cylinders or balls, placed between the raceways. The outer race is pressed into the cylindrical recess formed in the gearbox and is frictionally coupled with it to prevent any relative rotational movement. In a similar way, the inner raceway is frictionally engaged or secured in any other way to the shaft to prevent any rotational movement between them. In this way, the rollers adjust all relative rotational movement between the outer race (connected to the gearbox) and the inner race (connected to the axle). No relative rotational movement must occur between the outer race and the gearbox. Such movement can cause undesirable loosening, which could lead to premature wear or failure. In the past, the various gearbox housings have all been made of iron. Although the iron is very suitable for use in the manufacture of each of these housings, it is also a relatively heavy material. Due to increasing interests about fuel economy in vehicles, efforts have recently been made to reduce the weight of various vehicle components. As a result, it is known to use a lighter weight aluminum alloy to form the clutch housing of the gearbox, while continuing to form the main housing of the gearbox from iron. In another development, the use of aluminum alloys to form the clutch housing of the gearbox, it has been discovered that the annular bearings used to rotationally support the ends of the shafts in the aluminum clutch housing tend to lose their coupling frictional with the associated holes after the operation of the transmission. It has been determined that this loosening is caused by a differential in thermal expansion rates between aluminum alloys and steel. The aluminum alloy used to form the clutch housing expands a relatively large amount as the temperature increases. The steel used to form the outer raceways of the annular bearings, on the other hand, expands a relatively small amount as the temperature increases. Accordingly, the holes formed in the aluminum clutch housing expand radially to a significantly greater extent than the outer raceways of the annular bearings placed thereon. As a result, the side walls of the orifices expand away from the outer raceways of the bearings, when the temperature increases due to the normal use of the transmission. When this occurs, the outer raceways lose their frictional engagement with the associated holes. This loosening allows undesirable relative rotational movement, between the outer race and the clutch housing. Conventional completely iron-based transmissions do not experience this problem, because the rates of thermal expansion of the iron and steel are sufficiently similar to prevent this from happening. In aluminum housings, this problem can be contemplated by the use of an interference fit, heavy between the bearing and the hole. Unfortunately, it causes installation problems since the soft aluminum hole is easily damaged, when the steel raceway is pressed with a high interference fit. This prevents installation and may cause misalignment of the bearing. In this way, it would be advantageous to provide an improved structure for supporting a bearing in a hole provided in a portion of a gearbox and to prevent relative rotation between them, when the bearing and the gearbox are formed of materials having different Thermal expansion speeds.

BRIEF DESCRIPTION OF THE INVENTION This invention relates to an improved structure for supporting a bearing in an orifice, provided in a portion of a gearbox and to prevent relative rotation between them. In a preferred embodiment, the clutch housing portion of a gearbox is made of aluminum and includes an interior wall having a hole formed therein. A circumferential groove is formed in the side wall of the hole and a compressible or elastomeric O-shaped ring is placed in the groove. A bearing is made of steel and includes an inner race, an outer race and a plurality of rolls placed between the races. As the bearing is pressed into the hole, the O-ring is compressed completely into the slot. While both of the aluminum clutch housing and the outer race bearing steel ring remain in a relatively cold condition, the outer race will frictionally engage the inner surface of the. hole, thus avoiding any rotational movement, relative to each other. However, after the operation of the transmission, the temperatures of both the aluminum clutch housing and the steel outer race of the bearing will increase. Because aluminum expands at a higher rate per unit temperature than steel, the internal diameter defined by the hole will increase at a speed greater than the outer diameter defined by the outer race. As a result, a small space can be created between them. When this gap is created, the O-ring expands out of the groove formed in the inner surface of the holes, to maintain a frictional engagement with the outer race of the bearing. Therefore, the relative rotation between the two is avoided. This prevents premature wear and failure that can result from such rotational, relative movement. Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment when read in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a top plan view, partly in cross section of a transmission of a prior art vehicle. Figure 2 is an enlarged view of the portions of the clutch housing, the bearing and one of the secondary axes of the transmission of a prior art vehicle, illustrated in Figure 1. Figure 3 is an enlarged view, similar to Figure 2 illustrating a bearing support structure, in accordance with this invention.

Figure 4 is an enlarged view similar to the Figure 3, which illustrates in a somewhat exaggerated form, the bearing support structure of this invention, after the temperature of the vehicle transmission has increased and thermal expansion has occurred.

DETAILED DESCRIPTION OF THE PREFERRED MODALITY Now with reference to the drawings, there is illustrated in Figure 1 a transmission composed of a double secondary shaft, generally indicated at 5, which is known in the art. The illustrated transmission 5 is intended to be representative of any transmission structure of a known vehicle, either manually or automatically displaced, and only a brief generality of the structure and operation of the illustrated transmission 5 is necessary for a complete understanding of this. invention. The transmission 5 includes a box which supports and encloses its various components protectively. In the illustrated embodiment, the transmission case 5 is divided into three portions, namely, a front portion 6, a central portion 7 and a rear portion 8. The front portion 6 of the gearbox is usually referred to as the clutch housing. The clutch housing 6 is dimensioned to extend over and securely enclose a manually operable clutch assembly (not shown) which is connected between the vehicle engine and an input shaft 11 of the transmission 5. The central portion 7 of the box Speed is usually mentioned as the main accommodation. The main housing 7 contains most of the axes, gears and other components which are used to provide a set of transmission ratios to operate the transmission 5, as will be explained in the following. Finally, the rear portion 8 of the gearbox is usually referred to as the auxiliary housing. The auxiliary housing 8 contains most of the axes, gears and other components which are used to provide an additional group or groups of transmission ratios provided by the auxiliary section. The input shaft 11 is adapted to be rotatably driven, such as by a conventional diesel or internal combustion engine (not shown). As mentioned in the foregoing, the clutch assembly is connected between the vehicle engine and the input shaft 11 of the transmission 5. A first portion of the clutch assembly is connected to an output shaft of the engine. A second portion of the clutch assembly is mounted on the input shaft 11 for rotation therewith, typically by means of cooperating pins or splines. When the clutch assembly is engaged, the output shaft of the motor is connected to the input shaft 11 of the transmission 5 for rotation therewith. The input shaft 11 is supported for rotation by a bearing 12 mounted in an opening, formed through a bearing cover 13 secured to an inner wall 6a, provided in the case 6 of the gearbox clutch. The radial inner end of the inlet shaft 11 is formed to have an integral portion of a toothed gear which meshes with a plurality of radially inwardly extending teeth formed on an annular inlet drive gear. A seal 16 is provided around the input shaft 11 to prevent the lubricant contained within the transmission 5 from escaping. Within the main housing 7 of the gearbox, a first intermediate shaft 20 is rotatably supported on a pair of tapered bearings 20a and 20b. The front tapered bearing 20a is received within a hole or recess 6b formed in the inner wall 6a of the clutch housing 6. The taper, rear bearing 20b is received within a similar hole formed in the inner surface of an inner wall 7a provided on the main housing 7 of the gearbox. A plurality of gears 21, 22, 23, 24, 25 and 26 are keyed on the first secondary axis 20 for rotation therewith. The input drive gear 15 further includes a plurality of radially outwardly extending teeth which mesh with a corresponding plurality of teeth formed on the first of the gears 21 of the first gears of the secondary shaft. In this way, when the input shaft 11 is rotated, the input drive gear 15, the first secondary axis 20 and all the first gears 21 to 26 of the secondary shaft are rotated therewith. Similarly, a second intermediate shaft 30 is rotatably supported within the main housing 7 of the gearbox on a pair of tapered bearings (only the front tapered bearing 30a is illustrated). A plurality of gears 31, 32, 33, 34, 35 and 36 are keyed onto the second intermediate axis 30 for rotation therewith. The teeth extending radially outwardly of the input drive gear 15 are also meshed with a plurality of corresponding teeth, formed on the first gear 31 of the second gears of the secondary shaft. In this way, when the input shaft 11 is rotated, the driving gear 15, of input, the secondary second 30 and all the second gears 31 to 36 of the secondary shaft are also rotated therewith. The main shaft 40 is also provided within the main housing 6 of the gearbox. A plurality of annular, main axis gears 41, 42, 43 and 44 are positioned coaxially about the main axis 40. The first main shaft gear 41 engages both of the second gear 22 of the first gears of the secondary shaft and the second gear 32 of the second gears of the secondary shaft. In a similar way, the remaining gears 42, 43, 44 of the main shaft are engaged with the corresponding gears of the first gears 23, 25, 26 of the secondary shaft and the second gears 33, 35 and 36 of the secondary shaft. An annular output drive gear 45 is also positioned coaxially about the main axis 40. A plurality of cylindrical, cylindrical clutch collars 46, 47 and 48 are grooved on the main shaft 40 for rotation therewith. Each of the clutch collars 46, 47 and 48 are illustrated in Figure 1 in a neutral position or without a gear coupling. However, each of the clutch collars 46, 47 and 48 is axially movable relative to the main shaft 40, between the first and second gear coupling positions. For example, the first clutch collar 46 can be moved axially forward (to the left when looking at Figure 1) to connect the drive gear 15, input to the main shaft 40 for direct drive operation. The first clutch collar 46 can alternatively be moved axially backward (to the right when looking at Figure 1) to connect the first main shaft gear 41 to the main shaft 40 for the reduction operation of the gear. The other clutch collars 47 and 48 can be moved in a similar manner to control the operation of the transmission 5 in a known manner. As is well known, the axial movement of the clutch collars 46, 47 and 48 is performed by respective shift forks (not shown) which engage each of the clutch collars 46, 47 and 48. The shift forks are mounted on respective shift rails (not shown) for axial movement with them forwards and backwards. Typically, a column of changes containing a manually operable shift lever (not shown) is provided to select one of the shift or shift lanes for movement and to change the shift lane forward or backward as desired. It will be appreciated, however, that such selection and exchange actions may alternatively be performed by any known automated or automated manual apparatus. As mentioned in the above, the illustrated transmission 5 is a composite transmission. The components of the illustrated transmission 5 described so far constitute the main section of the transmission, which provides a predetermined number of speed reduction transmission ratios. The illustrated transmission 5 further includes a conventional auxiliary section, which is located rearwards (to the right when looking at Figure 1) of the main section and separated from it by the inner wall 7a of the main housing 7 of the housing of the transmission. The auxiliary section also provides a predetermined number of speed reduction transmission ratios in a known manner. The total number of available transmission speed reduction ratios of transmission 5 as a total, therefore, is equal to the product of the available transmission ratios of the main section and the available transmission ratios of the auxiliary section . Finally, the transmission 5 includes an output shaft 50 which is rotationally driven at a predetermined transmission ratio, relative to the input shaft 11 as long as the transmission 5 is coupled for use. Now with reference to Figure 2, a portion of the inner wall 6a of the clutch housing 6, the bearing 30a and a portion of the intermediate shaft 30 of the transmission 5 are illustrated in detail. As shown therein, the generally cylindrical bore 6b is formed in the inner wall 6a of the clutch housing 6. The bearing 30a includes an inner rolling ring 51, an outer rolling ring 52 and a plurality of rollers 53 positioned between the inner race 51 and the outer race 52. A box (not shown) can also be provided to retain the rollers 53 in suitable positions between the running ring 51, inner and outer race ring 52. In the illustrated embodiment, the bearing 30a is contemplated as a conventional tapered roller bearing assembly and the rollers 53 are referred to as cylinders. However, the bearing 30a can be contemplated as any of many similar known structures. The rolling ring 52 is pressed into the hole 6b to be frictionally engaged with it. Normally, the outside diameter of the outer race 52 of the bearing 30a is sized to be equal to the inside diameter of the hole 6b, plus or minus 0.02 mm (0.001 inch). Such a frictional coupling reliably retains the bearing 30a within the hole 6b and prevents any relative rotation occurring between the outer race 52 and the clutch housing 6. In the transmission 5 of the prior art, illustrated in Figures 1 and 2, the clutch housing 6 is formed of iron, while the outer bearing ring 52 of the bearing 30a is formed of steel. When subjected to an increasing temperature, these two materials expand at speeds that are relatively similar. Such an increase in temperature will occur as long as the transmission 5 is operated normally for a period of time. However, the frictional engagement of the outer race 52 with the inner surface of the hole 6b remains relatively constant because the two components expand at approximately the same speed. Figure 3 is similar to Figure 2, but illustrates the structure of this invention in detail. The iron clutch housing 6 of the transmission 5 of the prior art, shown in Figures 1 and 2, has been replaced by a clutch housing 6 'formed from an aluminum alloy. From now on, "aluminum" will refer to aluminum alloys and aluminum - both can be used. The clutch housing can also be formed of magnesium, magnesium alloys or other metals that have similar thermal properties. The structure of the aluminum clutch case 6 'is essentially the same as the iron clutch case 6 illustrated in Figures 1 and 2. Thus, the aluminum clutch case 6' includes an interior wall 6a ' which has a hole 6b1 formed in it. The remaining components of the transmission of this invention are identical to the conventional transmission illustrated in Figures 1 and 2 and similar reference numerals are used to indicate corresponding components. In Figure 3, a portion of the inner wall 6a 'of the clutch housing 6', modified in accordance with this invention, a bearing 60 and a portion of the secondary axis 30 of the transmission are illustrated in detail. The bearing 60 includes an inner rolling ring 61, an outer rolling ring 62 and a plurality of rollers 63 positioned between the inner rolling ring 61 and the outer rolling ring 62. A box (not shown) can also be provided to retain the rollers 63 in the proper positions between the inner race 61 and the outer race 62. In the illustrated embodiment, the bearing 60 is contemplated as a conventional tapered roller bearing assembly and the rollers 63 are referred to as cylinders. However, the bearing 60 can be contemplated as any of many similar known structures, for example ball bearings, cylindrical roller bearings or needle bearings. The outer rolling ring 62 is pressed into the hole 6b 'to be frictionally engaged with it when both of the components are in a relatively cold condition. Normally, the outside diameter of the outer race 62 of the bearing 60 is sized to be equal to the inside diameter of the hole 6b ', plus or minus 0.02 mm (0.001 inches), when both of the components are in a relatively cold condition. Such frictional engagement reliably retains the bearing 60 within the bore 6b 'and prevents any relative rotation between the outer rolling ring 62 and the clutch housing 6' from occurring while both components remain in a relatively cold condition. The case 6 'of the clutch of this invention, differs from the case 6 of the prior art clutch, in that the circumferential groove 64 is formed in the side wall of the hole 6b 'and an expandable 0-shaped ring 65 is placed in the groove 64. The groove 64 and the O-ring 65 can be located on either side along the side wall of the hole 6b ', but preferably they are located in the front half of the hole 6b1 (to the left as seen in the drawing) to allow that the bearing 60 be guided into the hole 6b 'during installation. The O-ring 65 can be formed of any compressible or elastomeric material. Preferred materials include synthetic rubber and certain plastics or other synthetic materials such as nylon. A synthetic rubber, such as Viton, is more preferred. Although the invention will be discussed in connection with an O-ring, any type of ring made of a compressible or elastomeric material can be used. For example, the radial cross section of the ring may be in the form of a square, a rectangle or a star, in addition to a circle. Also, the ring does not have to be a continuous ring around the circumference of the recess. On the contrary, it may be one or more discontinuities in the ring while the function described in the following is provided. The O-ring 65 is sized to be slightly larger in diameter than the diameter of the slot 64. During assembly, it is advantageous that the O-ring 65 be sprayed with a lubricant before being installed inside the slot 64. Then, the O-ring 65 is again sprayed with a lubricant, when the bearing 60 is pressed into the hole 6b 'to assist in the compression of the O-ring. When the outer race 62 is pressed into the orifice 6b ', the O-shaped ring 65 is completely compressed within the groove 64. While both of the case 6' of the aluminum clutch and the outer race 62 of the bearing steel 60 remain in a relatively tight condition cold, the outer rolling ring 62 will frictionally couple to the inner surface of the hole 6b ', thus avoiding any rotational movement relative to each other.

However, during normal use of the transmission, the temperatures of both the case 6 'of the aluminum clutch and the outer race 62 of the bearing 60 will increase. Because aluminum expands at a higher rate per unit temperature than steel, the inner diameter defined by the hole 6b 'will increase at a speed greater than the outer diameter defined by the outer race 62. As a result, a small space can be created between them, as illustrated in a slightly exaggerated form in Figure 4. The lack or absence of any other structure, this space would allow in any other way the relative rotation between the ring 62 to occur. of outer race and the housing 6 'of the aluminum clutch. However, when that space is created, the O-ring 65 expands outwardly from the groove 64 formed in the inner surface of the hole 6b 'to maintain a frictional engagement with the outer race 62 of the bearing 60. consequently, the relative rotation between the two is avoided. The expansion of the O-ring 65 occurs more rapidly than the thermal expansion of the aluminum of the clutch housing and the bearing steel. O-ring 65 maintains in this form the frictional coupling between the rolling ring 62 and the inner surface of the hole 6b1 of the aluminum clutch housing 6, even when the temperature of the transmission increases rapidly. This prevents premature wear and failure, which would result from such relative rotational movement. The rapid expansion of the 0-ring 65 occurs in both mechanical expansion (ie, decompression after being compressed in the groove) and thermal expansion. Preferably, the ring 65 in the form of 0 is made of a material which has a higher rate of thermal expansion than aluminum and steel and more preferably of a material such as synthetic rubber, which has a thermal expansion rate about five to seven times greater than aluminum and about ten to fifteen times greater than steel. The present invention thus avoids the relative rotation between the bearing and the hole without resorting to an interference fit with its associated disadvantages. At the same time, the expanding O-ring 65 can function as a damper between the inner surface of the hole 6b 'of the case 6' of the aluminum clutch and the outer race 62 of the bearing 60, allowing the self-centering of the bearing 60 within the hole 6 'and reducing the noise and wear that must result from misalignment.

This invention has been explained in the context of the secondary double axle composite transmission illustrated in Figure 1. However, it will be appreciated that this invention can be used in any other type of transmission or other device, in which a bearing having An outer rolling ring formed of a first material, is installed within a hole provided in a wall formed of a second material, while the second material has a thermal expansion speed which is greater than that of the first material. In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment. However, it should be understood that this invention can be practiced in any other way than that specifically explained and illustrated without departing from its spirit or scope. Having described the invention as above, property is claimed as contained in the following:

Claims (10)

1. A bearing support structure, characterized in that it comprises: a wall having a hole formed therein, the hole includes a side wall having a groove formed therein; an expandable ring placed in the slot; and a bearing including an outer race ring positioned within the hole, the outer race is formed of a first material and the side wall of the orifice is formed of a second material, which has a rate of thermal expansion which is greater than a thermal expansion velocity of the first material.

2. The bearing support structure, according to claim 1, characterized in that the orifice is generally cylindrical in shape and the bearing is generally annular in shape.

3. The bearing support structure, according to claim 1, characterized in that the ring is formed of an elastomeric material.

4. The bearing support structure, according to claim 1, characterized in that the first material is steel and the second material is selected from the group consisting of aluminum, aluminum alloys, magnesium and magnesium alloys.

5. The bearing support structure, according to claim 1, characterized in that the groove is a circumferential groove and in which the ring is an O-shaped ring.

6. The bearing support structure, according to claim 1, characterized in that the ring has a thermal expansion velocity which is greater than the thermal expansion velocity of the second material.

7. The bearing support structure, according to claim 3, characterized in that the ring is formed of synthetic rubber.

8. The bearing support structure, according to claim 1, characterized in that the wall is an inner wall of a box for a transmission and wherein the bearing rotatably supports an axis within the transmission case.

9. The bearing support structure, according to claim 1, characterized in that the groove and the ring are located in the front half of the side wall.

10. A transmission including a box, characterized in that it includes an inner wall having a hole formed therein, the hole includes a side wall having a groove formed therein, an input shaft extending inside the box, an axle outlet extending within the case, a plurality of gears contained within the case and selectively connectable between the input shaft and the output shaft to provide a plurality of transmission ratios therebetween and a bearing support structure in compliance with claim 1, placed inside the hole. SUMMARY OF THE INVENTION An improved structure that supports a bearing in a hole provided in a portion of a gearbox and prevents relative rotation between them. In a preferred embodiment, the clutch housing portion of a gearbox is made of aluminum and includes an inner wall having an orifice formed therein. A circumferential groove is formed in the side wall of the hole and a compressible or elastomeric 0-shaped ring is placed in the groove. The bearing is made of steel and includes an inner race, an outer race and a plurality of rolls placed between the raceways. As the bearing is pressed into the hole, the 0-shaped ring is compressed completely into the slot. While both of the aluminum clutch housing and the outer steel bearing race remain in a relatively cold condition, the outer race will frictionally couple the interior surface of the hole, thus preventing any relative rotational movement therebetween. Nevertheless, after the operation of the transmission, the temperatures of both of the aluminum clutch housing and the outer rolling ring, bearing steel will increase. Because aluminum expands at a higher rate per unit temperature than steel, the inner diameter defined by the orifice will increase at a rate greater than the outer diameter defined by the outer race. As a result, a small space can be created between them. When this gap is created, the O-ring expands outwardly from the groove formed in the inner surface of the hole, to maintain a frictional engagement with the outer race of the bearing. Therefore, the relative rotation between them is avoided. This prevents premature wear and failure that can result from such relative rotational movement.