JP2006336827A - Ball bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact ball bearing which is excellent in impact resistance, load resistance, and assembling characteristics and which can safely continue a ball to roll between raceway grooves of an inner race and an outer race. <P>SOLUTION: The ball bearing comprises a pair of inner races and outer races counter arranged relatively rotatably and a plurality of balls built-in freely rotatably between raceway grooves formed respectively on a counter surface of the inner race and a counter surface of the outer race and, assuming that the diameter of the virtual circle which goes through the interspace between the inner diameter of the inner race and the outer diameter of the outer race is dm, the pitch circle of the ball is PCD, the ball diameter is Da, the radial direction distance from the lowest part of the raceway groove of the inner race to the edge part of the raceway groove is Hi, and the radial direction distance from the lowest part of the raceway groove of the outer race to the edge part of the raceway groove is Ho, 1.00<(PCD/dm)≤1.05 is obtained and at least either one of Hi, Ho is Hi≥0.15Da or Ho≥0.15Da. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention provides an output shaft with a worm gear incorporated in a small electric motor for automobiles that requires low noise and high durability, such as an automobile power steering device, a window lifting device, an electric seat adjustment device, and a wiper driving device. The present invention relates to an improvement of a supporting ball bearing.

A motor device with a worm gear (hereinafter referred to as a motor device) used for a small electric motor for automobiles is provided with a worm 26 on an output shaft 20 of an electric motor 30 as shown in FIGS. 9 to 12, for example. The output is transmitted through a worm wheel 28 that meshes with the worm 26, and a plurality of bearings 22, 24, and 40 for supporting a load caused by the meshing of the worm 26 and the worm wheel 28 are output shafts 20. It is the composition arranged in. The electric motor 30 includes a rotor 32 fixed to the output shaft 20 and a stator 34 fixed to the housing 36. For example, when current is supplied to the stator 34, the stator 34 and the rotor 32 are supplied. The output shaft 20 is rotated by a magnetic interaction generated between the output shaft 20 and the output shaft 20.
In such a motor device, generally, the load generated by the meshing between the worm 26 and the worm wheel 28 is characterized in that the load in the axial direction is larger than the load in the radial direction of the output shaft 20, and the axial load. Is characterized in that its direction is reversed every time the worm 26 is rotated forward or reverse.

As a bearing configuration in such a motor device, for example, in the motor device shown in FIG. 9, three radial slide bearings 24 are arranged at the center and both ends of the output shaft 20, respectively, and two thrust slide bearings 40 are output. It arrange | positions at the both ends of the axis | shaft 20, respectively (refer patent document 1). In the motor device shown in FIG. 10, a two-row combination ball bearing 22 is disposed at the center of the output shaft 20, and two radial plain bearings 24 are disposed at both ends of the output shaft 20, respectively (Patent Literature). 2). In the motor device shown in FIG. 11, a single row deep groove ball bearing 22 is disposed at the center of the output shaft 20 and two radial plain bearings 24 are disposed at both ends of the output shaft 20 (patents). Reference 1). In the motor device shown in FIG. 12, a single row deep groove ball bearing 22 is arranged at the center of the output shaft 20, and a radial sliding bearing 24 is arranged only on the motor side of the output shaft 20 (Patent Document). 3).
In addition, each FIG. 9-12 has simplified and shown drawing attached to each literature 1-3 so that the characteristic structure of the motor apparatus shown by patent documents 1-3 may become clear.

However, the motor device as shown in FIG. 9 requires a space for disposing the thrust bearings 40 at both ends of the output shaft 20, and there is a problem that the motor device is enlarged in the axial direction. Similarly, even in the motor device as shown in FIG. 10, a space for arranging the two-row combination ball bearings 22 is required, so that the motor device is enlarged in the axial direction. Such an increase in the size of the motor device becomes a problem when, for example, the motor device is incorporated in a vehicle having no space in the axial direction.
On the other hand, in the motor device as shown in FIG. 11, only the single row deep groove ball bearings 22 are disposed, and the mounting space for the bearings can be small, so that the motor device can be downsized in the axial direction. Can do. Further, in the motor device as shown in FIG. 12, the radial sliding bearing 24 is arranged only on the motor side, so that the motor device can be further reduced in the axial direction.

  By the way, the single row deep groove ball bearings 22 used in these motor devices (FIGS. 11 and 12), for example, as shown in FIG. 8, receive a large axial load caused by the meshing of the worm 26 and the worm wheel 28. The load is applied only by the deep groove ball bearing 22. In this case, for example, when an impact load is applied to the deep groove ball bearing 22 due to an external factor such as vibration, the rolling surface of the ball 6, the raceway surface of the inner ring 2 (the raceway groove 8), and the raceway surface of the outer ring 4 (the raceway groove 10). ) And the contact ellipse of the rolling contact portion may reach a so-called ball reaching the edge in the width direction of each raceway surface. In this case, an edge load (stress concentration) is generated on the rolling surface of the ball 6 and the edge portions 8s and 10s of the raceway surfaces (track grooves 8 and 10), and an excessive surface pressure is applied to the balls 6 and thereby the ball 6 There is a possibility that the rolling surfaces of the inner ring 2 and the outer ring 4 may be scratched or indentations may be formed on the raceway surfaces (track grooves 8 and 10). If the motor device continues to be operated in such a state, abnormal noise is generated from the deep groove ball bearing 22 or the deep groove ball bearing 22 (particularly, the race groove 8 of the inner ring 2 and the race groove 10 of the outer ring 4, the rolling of the balls 6). Since the moving surface) may crack or flake early, it becomes difficult to keep the motor device operating well over a long period of time.

  Therefore, the ball 6 is prevented from riding on the edge portions 8s and 10s of the raceway grooves 8 and 10, and the impact resistance and resistance of the deep groove ball bearing 22 (in particular, the inner ring 2 and the outer ring 4 and the ball 6) are prevented. As measures to ensure loadability, for example, (1) increase the bearing size. (2) Increase the diameter of the ball 6 or increase the number of incorporation. (3) The curvature radius of the cross section of the raceway groove 8 of the inner ring 2 and the raceway groove 10 of the outer ring 4 is increased. (4) Reduce the internal clearance of the bearing. (5) Various measures such as increasing the depth of the raceway groove 8 of the inner ring 2 and the raceway groove 10 of the outer ring 4 are conceivable.

However, in the measure (1), since the mounting space for the bearing is increased, the motor device is enlarged in the axial direction and the radial direction. Further, in the measure (2), the size of the balls 6 and the number of built-in balls are limited due to restrictions on the dimensions of the bearings, and the degree of freedom in design is reduced. For this reason, depending on the size of the bearing, the desired ride resistance cannot be ensured (the ball 6 cannot be prevented from riding on the edge 8s of the raceway groove 8 of the inner ring 2 and the edge 10s of the raceway groove 10 of the outer ring 4). Yes (especially when applied to miniature ball bearings or small diameter ball bearings). Further, in the measures (3) and (4), the rolling surfaces of the balls 6 and the raceway grooves 8 of the inner ring 2 and the outer ring 4 can be used even during operation in which a large load (for example, impact load) is not applied from the outside. , 10, the pressure of the rolling contact portion increases, and for example, the contact portion may generate heat or wear due to friction, which may shorten the life of the bearing (requires early replacement of the bearing). is there. Furthermore, in the measure (5), when assembling the bearing, it becomes difficult to incorporate the ball 6 between the raceway groove 8 of the inner ring 2 and the raceway groove 10 of the outer ring 4. During the work, the rolling surfaces of the balls 6 and the raceways (the raceways 8 and 10) of the inner race 2 and the outer race 4 may be damaged.
No. 6-15491 JP-A-9-132154 Japanese Utility Model Publication No. 61-3248

  The present invention has been made to solve such problems, and its purpose is to provide impact resistance, load resistance and assembly capable of stably rolling the ball between the raceway grooves of the inner and outer rings. The object is to provide a compact ball bearing with excellent properties.

  In order to achieve such an object, a ball bearing according to the present invention includes a pair of inner and outer rings arranged opposite to each other so as to be relatively rotatable, and raceways formed on the inner ring facing surface and the outer ring facing surface, respectively. It is provided with a plurality of balls that are rotatably incorporated between the grooves. In such a configuration, the diameter of the imaginary circle passing between the inner diameter of the inner ring and the outer diameter of the outer ring is dm, the pitch diameter of the balls is PCD, the diameter of the balls is Da, and the track from the bottom of the track groove of the inner ring. When the radial distance to the edge of the groove is Hi and the radial distance from the bottom of the raceway groove of the outer ring to the edge of the raceway groove is Ho, 1.00 <(PCD / dm) ≦ 1.05 In addition, at least one of Hi and Ho is set to satisfy Hi ≧ 0.15 Da or Ho ≧ 0.15 Da. In this case, the ball bearing is a single row ball bearing in which a plurality of balls are arranged in a row along the raceway grooves.

  According to the present invention, it becomes possible to keep balls stably rolling between the raceway grooves of the inner and outer rings, and a ball bearing excellent in impact resistance, load resistance and assemblability can be made compact.

Hereinafter, a ball bearing according to an embodiment of the present invention will be described with reference to the accompanying drawings.
Since the ball bearing of this embodiment is an improvement of the above-described motor device with a worm gear (FIGS. 9 to 12), the description of the improved portion will be given below. In addition, the same code | symbol is attached | subjected on drawing and the description is abbreviate | omitted to the structure same as the motor apparatus with a worm gear of FIGS.

  As shown in FIGS. 1 and 2, in the motor device with a worm gear (hereinafter referred to as “motor device”) of the present embodiment, the output shaft 20 is rotatably supported by a single row deep groove ball bearing 22 and two radial slide bearings 24. The deep groove ball bearings 22 are arranged in a row of raceway grooves 8 formed on the inner ring 2 and the outer ring 4, which are arranged to face each other so as to be relatively rotatable, and on the facing surface 2a of the inner ring 2 and the facing surface 4a of the outer ring 4, respectively. , 10 and a plurality of balls 6 incorporated so as to roll freely. In the present embodiment, the deep groove ball bearing 22 is disposed at the center of the output shaft 20, and the two radial slide bearings 24 are disposed at both ends of the output shaft 20. The plurality of balls 6 are rotatably held one by one by the cage 12. The raceway groove 8 of the inner ring 2 and the raceway groove 10 of the outer ring 4 are each formed in a circular arc shape in cross section.

In this embodiment, the deep groove ball bearing 22 has a diameter of an imaginary circle passing through the middle between the inner diameter d of the inner ring 2 and the outer diameter D of the outer ring 4 as dm (hereinafter referred to as the center diameter dm), and the center point of each ball 6 When the diameter of the imaginary circle connecting the two is PCD (hereinafter referred to as pitch circle diameter PCD; PCD: Pitch Circle Diameter), the relationship between the center diameter dm and the pitch circle diameter PCD is 1.00 <(PCD / dm). It is set to be within a range of ≦ 1.05.
A radial distance (depth of the track groove 8) from the bottom of the track groove 8 of the inner ring 2 to the edge (shoulder) 8s of the track groove 8 is defined as Hi (hereinafter referred to as a groove depth Hi). The radial distance (depth of the raceway groove 10) from the bottom of the raceway groove 10 of the outer ring 4 to the edge (shoulder) 10s of the raceway groove 10 is defined as Ho (hereinafter referred to as the groove depth Ho). When the diameter of 6 (ball diameter) is Da (hereinafter referred to as ball diameter Da), at least one of the groove depth Hi of the raceway groove 8 of the inner ring 2 or the groove depth Ho of the raceway groove 10 of the outer ring 4 is The ball diameter Da is 15% or more (Hi ≧ 0.15 Da and Ho ≧ 0.15 Da), and the groove depth Hi of the raceway groove 8 of the inner ring 2 is greater than or equal to the groove depth Ho of the raceway groove 10 of the outer ring 4. It is set so as to increase (Hi ≧ Ho, preferably Hi> Ho).

For example, the ratio (PCD / dm) between the center diameter dm and the pitch circle diameter PCD is 1.03, and the ratio (Hi / Da) between the groove depth Hi of the raceway groove 8 of the inner ring 2 and the ball diameter Da is 0. 20 and the ratio of the groove depth Ho of the raceway groove 10 of the outer ring 4 to the ball diameter Da (Ho / Da) is 0.17, the ball bearing of this embodiment corresponding to the JIS B1513 standard (bearing inner diameter) d: φ8 (mm), bearing outer diameter D: φ22 (mm), bearing width B: 7 (mm), ball diameter Da: φ3.969 (mm)) (see FIG. 1) When the indicated x1 value and the riding load of the ball 6 are calculated, the x1 value is 0.118, and the riding load is 1900 (N). The x1 value is the ball diameter Da and the amount of interference x (the amount by which the ball 6 enters (interfers with) the raceway groove 8 or the raceway groove 10 when the ball 6 is assembled between the raceway grooves 8 and 10 of the inner ring 2 and the outer ring 4. ) (X1 = x / Da), details of which will be described later.
On the other hand, the ratio (PCD / dm) between the center diameter dm and the pitch circle diameter PCD is set to 1.00, and the ratio (Hi / Da) between the groove depth Hi of the raceway groove 8 of the inner ring 2 and the ball diameter Da. When the ratio of the groove depth Ho of the raceway groove 10 of the outer ring 4 to the ball diameter Da (Ho / Da) is 0.12, the existing ball bearing corresponding to the JIS B1513 standard (d: In φ8 (mm), D: φ22 (mm), B: 7 (mm), Da: φ3.969 (mm)), the x1 value is 0.121, and the riding load is 900 (N).

Thus, compared with the existing ball bearing in which the relationship between the center diameter dm and the pitch circle diameter PCD is PCD / dm = 1.00, the ball bearing according to the present embodiment includes the ball diameter Da and the ball integration. The number of inner rings 2 and outer rings 4 can be reduced without changing the radius of curvature of the raceway grooves 8 and 10 of the inner ring 2 and the outer ring 4 and the radial internal clearance. The raceway grooves 8 and 10 can be deepened (groove depths Hi and Ho are increased). Thereby, the load required for the ball 6 to ride on the edge portions 8s, 10s of the raceway grooves 8, 10 of the inner ring 2 and the outer ring 4 is increased (in the above-described example, the necessary ride load is increased from 900N to 1900N). Thus, the contact ellipse virtually formed in the rolling contact portion between the rolling surface of the ball 6 and the race grooves 8 and 10 of the inner ring 2 and the outer ring 4 is the edge of the race grooves 8 and 10 of the inner ring 2 and the outer ring 4. It becomes difficult to reach the portions 8s and 10s (the ball 6 can be stably rolled between the raceway grooves 8 and 10 of the inner ring 2 and the outer ring 4). For this reason, it is possible to secure the climbing resistance of the ball 6 and to make the deep groove ball bearing 22 excellent in impact resistance, load resistance and assemblability compact.
Therefore, the motor device with a worm gear using such a deep groove ball bearing 22 may generate noise from the device (for example, the deep groove ball bearing 22) without increasing the size of the device (can be downsized). Without being able to continue to operate well over a long period of time (durability can be improved).

Here, the x1 value (x1 = x / Da: ratio of the ball diameter Da and the interference amount x) indicating the assemblability of the ball bearing will be described with reference to FIGS. 13 (a) and 13 (b).
As an example of a method for assembling the ball bearing, the inner ring 2 is moved (eccentric) in the radial direction (radial direction) with respect to the outer ring 4 in the same plane, and is formed in a half-moon shape formed between the inner ring 2 and the outer ring 4. A plurality of balls 6 are inserted between the raceway groove 8 of the inner ring 2 and the raceway groove 10 of the outer ring 4 from the opening S (FIG. 13A), and the inner ring 2 and the outer ring 4 are concentric at the final stage. There is a method in which the outer ring 4 is elastically deformed by applying a force to the inner ring 2. By such a method, the number of balls to be incorporated is maximized.
In this case, the position of each ball 6 when the plurality of balls 6 are inserted from the half-moon-shaped opening S takes an arbitrary position in the opening S. The state shown in FIG. 13B is one example, and each ball 6 other than the widest position of the opening S (for example, the upper center of the opening S in FIG. 13B) is the track groove 8 of the inner ring 2. , And a part of the ball 6 arranged at the widest position (upper center) of the opening S interferes with (overlaps) only the outer ring 4 and x. .
If this amount of interference x is too large, it will be difficult for the ball bearing to incorporate the ball 6 between the raceway groove 8 of the inner ring 2 and the raceway groove 10 of the outer ring 4 (in the worst case, not all of them). There is a risk that mass production cannot be performed by the automatic assembly machine (the assembly line is likely to be stagnant). The amount of interference x is a value determined from the track diameters of the inner ring 2 and the outer ring 4, the groove depths Hi and Ho of the track grooves 8 and 10 of the inner ring 2 and the outer ring 4, the ball diameter Da, the number of balls, etc. The ratio between the interference amount x and the ball diameter Da is defined as x1 (x1 = x / Da), which is one of the indexes indicating the assemblability of the ball bearing.

In FIG. 3, the groove depth Hi of the raceway groove 8 of the inner ring 2 and the groove depth Ho of the raceway groove 10 of the outer ring 4 are the same (Hi = Ho), and the x1 value indicating the assemblability is the same as that of the conventional ball bearing. In the case of the same value (x1 = 0.25), the ratio (PCD / dm) between the center diameter dm and the pitch circle diameter PCD and the ratio (Hi /) between the ball diameter Da and the groove depth Hi (or groove depth Ho). The calculation results for the relationship with Da or Ho / Da) are shown. In FIG. 3, the horizontal axis is the ratio of the center diameter dm to the pitch circle diameter PCD (PCD / dm), and the left side of the vertical axis is the ratio of the ball diameter Da to the groove depth Hi (or groove depth Ho). (Hi / Da or Ho / Da), the right side of the vertical axis indicates the ratio x1 (x / Da) between the ball diameter Da and the interference amount x.
As is apparent from FIG. 3, the relationship between the center diameter dm and the pitch circle diameter PCD is 1.00 <(PCD / dm) ≦ 1.05, which is the technical scope of the present invention. Compared to the bearing (PCD / dm = 1.00), the groove depth Hi (or the groove depth Ho) is increased without impairing the assemblability (the race grooves 8, 10 of the inner ring 2 and the outer ring 4 are deepened). can do.

  When the ratio of the center diameter dm to the pitch circle diameter PCD (PCD / dm) exceeds 1.05, the pitch circle diameter PCD opens to the outside (the balls 6 are positioned in the direction of further contact with the outer ring 4). ). In this case, as shown in FIG. 4, depending on the ball diameter Da (usually about Da = 0.5 to 0.6H) with respect to the cross-sectional height (thickness) H of the outer ring 4, the bottom part of the raceway groove 10 of the outer ring 4 is used. The wall thickness (minimum wall thickness) No. cannot be sufficiently secured, and the outer ring 4 may be deformed or the strength may be reduced. Therefore, the relationship between PCD / dm (ratio between the center diameter and pitch circle diameter) and No / H (ratio between the cross-sectional height of the outer ring 4 and the minimum wall thickness) (value of No / H with respect to PCD / dm) is In the region above the thick line (No / H = 0.15) in FIG.

As shown in FIG. 5, if the groove depth Hi (or groove depth Ho) is excessively increased, the outer diameter surface (opposing surface 2a) of the inner ring 2 and the inner diameter surface (opposing surface 4a) of the outer ring 4 are reduced. The interval is narrowed, and the thickness Ct of the cage 12 (usually about Ct = 0.4 to 0.5 Da) cannot be secured sufficiently. For example, the cage 12 may be deformed or the strength may be reduced. In this case, if the thickness Ct of the cage 12 is to be secured, the outer diameter surface (opposing surface 2a) of the inner ring 2 and the inner diameter surface (opposing surface 4a) of the outer ring 4 interfere with (contact) the cage 12. There is a risk that.
Therefore, the relationship (PCD / dm) between PCD / dm (ratio between the center diameter and pitch circle diameter) and Hi / Da or Ho / Da (ratio between ball diameter Da and groove depth Hi or groove depth Ho). (Hi / Da or Ho / Da value) is preferably in a region below the thick line (Hi / Da = 0.25) in FIG. On the other hand, when the ratio (PCD / dm) between the center diameter dm and the pitch circle diameter PCD is 1.00 or less, the groove depth Hi (or groove depth Ho) is the same as the conventional ball bearing design. ) Cannot be secured sufficiently. In this case, the balls 6 run on the edges 8 s and 10 s of the race grooves 8 and 10 of the inner ring 2 and the outer ring 4, so that the rolling surfaces of the balls 6 are damaged, or the race surfaces of the inner ring 2 and the outer ring 4 ( An indentation or the like is generated in the raceway grooves 8 and 10), and as a result, for example, there is a possibility that abnormal noise is generated from the motor device or the durability of the motor device is deteriorated.

FIG. 6 shows the groove depth Hi (or groove depth Ho) when the groove depth Hi of the raceway groove 8 of the inner ring 2 and the groove depth Ho of the raceway groove 10 of the outer ring 4 are the same (Hi = Ho). 3 shows the result of calculation regarding the relationship between the ball 6 and the load required for the ball 6 to ride on the edge 8s of the raceway groove 8 of the inner ring 2 (or the edge 10s of the raceway groove 10 of the outer ring 4).
As apparent from FIG. 6, the groove depth Hi of the raceway groove 8 of the inner ring 2 and the groove depth Ho of the raceway groove 10 of the outer ring 4 are 15% or more of the ball diameter Da which is the technical scope of the present invention (Hi ≧ 0.15 Da, Ho ≧ 0.15 Da), the ride load of the ball 6 can be improved by about 1.2 to 1.5 times or more compared with the conventional ball bearing (12 to 14%). it can. In FIG. 6, when the groove depth Hi, Ho is 12% of the ball diameter Da (Hi / Da = 0.12, Ho / Da = 0.12), the riding load of the ball 6 is 1.0. The riding load of the ball 6 with respect to Hi / Da (or Ho / Da) is shown.

  Further, in the present embodiment, the inner ring 2 has a groove depth Hi larger than the groove depth Ho of the outer ring 4 (Hi ≧ Ho, preferably Hi> Ho). The distance between the contact ellipse with the ball 6 virtually formed in the second raceway groove 8 and the edge 8s of the raceway groove 8 of the inner ring 2, and the ball 6 virtually formed in the raceway groove 10 of the outer ring 4; The distance between the contact ellipse and the edge 10s of the raceway groove 10 of the outer ring 4 is made substantially the same. That is, in the ball bearing of the present embodiment, the raceway groove of the inner ring 2 is reduced by the convex shape of the raceway groove 8 of the inner ring 2 (the minor axis of the contact ellipse existing in the circumferential direction is reduced). The contact pressure between the ball 6 of the contact ellipse formed on the ball 8 and the raceway groove 8 is increased, and the major axis of this ellipse is larger than the major axis of the contact ellipse formed on the raceway groove 10 of the outer ring 4. Become. Thus, in the present embodiment, the groove depth Hi of the raceway groove 8 of the inner ring 2 is made larger than the groove depth Ho of the raceway groove 10 of the outer ring 4 (Hi ≧ Ho, preferably Hi> Ho). The contact ellipse with the ball 6 virtually formed in the raceway groove 8 of the inner ring 2 and the edge portion 8s of the raceway groove 8 of the inner ring 2 that is easier to ride the ball 6 than the edge portion 10s of the raceway groove 10 of the outer ring 4. Is ensured so that the load on the ball 6 is substantially uniform between the raceway groove 8 of the inner ring 2 and the raceway groove 10 of the outer ring 4.

In FIG. 7, the sum (Hi + Ho) of the groove depth Hi of the raceway groove 8 of the inner ring 2 and the groove depth Ho of the raceway groove 10 of the outer ring 4 is fixed to 38% of the ball diameter Da (Hi + Ho = 0.38 Da). In this case, the ratio (Hi / Ho) of the groove depth Hi of the raceway groove 8 of the inner ring 2 and the groove depth Ho of the raceway groove 10 of the outer ring 4, the edge 6s of the raceway groove 8 of the inner ring 2 and the ball 6 The calculation result about the relationship with the load required to ride on the edge part 10s of the raceway groove | channel 10 of the outer ring | wheel 4 is shown.
As apparent from FIG. 7, when the ratio (Hi / Ho) of the groove depth Hi of the raceway groove 8 of the inner ring 2 to the groove depth Ho of the raceway groove 10 of the outer ring 4 is about 1.2, 6 can be ensured substantially uniformly and sufficiently by the raceway groove 8 of the inner ring 2 and the raceway groove 10 of the outer ring 4. In order to maximize such an effect, the groove depth Hi of the raceway groove 8 of the inner ring 2 is set to 1.1 to 1.3 times the groove depth Ho of the raceway groove 10 of the outer ring 4. It is preferable (see the calculation result shown in FIG. 7).

  As described above, according to this embodiment, the design of the deep groove ball bearing 22 is not significantly changed (the ball diameter Da, the number of balls, the radius of curvature, the internal clearance, etc.), and the assembling property is not impaired. The ball 6 can continue to roll stably between the raceway grooves 8 and 10 of the inner ring 2 and the outer ring 4. For this reason, it is possible to secure the climbing resistance of the ball 6 and to make the deep groove ball bearing 22 excellent in impact resistance, load resistance and assemblability compact. Therefore, by using such a deep groove ball bearing 22, the motor device with a worm gear can improve the reliability of the device (quietness that does not generate abnormal noise) without increasing the size of the device, It can continue to operate well over a long period of time (durability can be improved).

In the embodiment described above, the groove depth Hi of the raceway groove 8 of the inner ring 2 and the groove depth Ho of the raceway groove 10 of the outer ring 4 are both 15% or more of the ball diameter Da (Hi ≧ 0.15 Da and Ho). However, only one of the groove depths (Hi or Ho) may be 15% or more of the ball diameter Da (Hi ≧ 0.15 Da or Ho ≧ 0.15 Da). In the embodiment described above, the groove depth Hi of the raceway groove 8 of the inner ring 2 is set to be larger than the groove depth Ho of the raceway groove 10 of the outer ring 4 (Hi> Ho). The groove depth Hi of the raceway groove 8 and the groove depth Ho of the raceway groove 10 of the outer ring 4 may be set to be the same (Hi = Ho), and the groove depth Ho of the raceway groove 10 of the outer ring 4 is You may set so that it may become larger than the groove depth Hi of the raceway groove | channel 8 of the inner ring | wheel 2 (Ho> Hi).
In the above-described embodiment, the ball bearing is described as the deep groove ball bearing 22, but the bearing type is not limited to this, and for example, the above-described effects can be achieved by applying to a miniature ball bearing or a small diameter ball bearing. Can be made.

Sectional drawing which shows the structural example of the principal part of the motor apparatus with a worm gear which concerns on this invention. Sectional drawing which shows the example of whole structure of the motor apparatus with a worm gear which concerns on this invention. The figure which shows the relationship between [pitch circle diameter PCD / center diameter dm] and [groove depth Hi, Ho] in case x1 value is the same value. The figure which shows the relationship between [pitch circle diameter PCD / center diameter dm] and [outer ring minimum wall thickness No./section height H]. The figure which shows the relationship between [pitch circle diameter PCD / center diameter dm] and [groove depth Hi (or groove depth Ho) / ball diameter Da]. The figure which shows the relationship between [groove depth Hi (or Ho) / ball diameter Da] and [ball riding load ratio]. The figure which shows the relationship between [groove depth Hi / groove depth Ho (each groove depth ratio)] and [the riding load of a ball]. Sectional drawing which shows the structural example of the principal part of the conventional motor apparatus with a worm gear. Sectional drawing which shows the example of whole structure of the conventional motor apparatus with a worm gear. Sectional drawing which shows the example of whole structure of the conventional motor apparatus with a worm gear. Sectional drawing which shows the example of whole structure of the conventional motor apparatus with a worm gear. Sectional drawing which shows the example of whole structure of the conventional motor apparatus with a worm gear. (a) And (b) is a front view for demonstrating an example of the assembly method of a ball bearing.

Explanation of symbols

2 Inner ring 4 Outer ring 6 Ball 8, 10 Track groove 8s, 10s Edge (shoulder)
d Inner ring inner diameter D Outer ring outer diameter dm Center diameter PCD Pitch circle diameter Da Ball diameter Hi, Ho Groove depth

Claims (2)

A pair of inner and outer rings disposed opposite to each other for relative rotation;
A plurality of balls that are rotatably integrated between raceway grooves formed on the opposing surface of the inner ring and the opposing surface of the outer ring,
The diameter of the imaginary circle that passes between the inner diameter of the inner ring and the outer diameter of the outer ring is dm, the pitch diameter of the ball is PCD, the diameter of the ball is Da, and from the bottom of the inner ring raceway groove to the edge of the raceway groove When the radial distance is Hi and the radial distance from the bottom of the outer raceway groove to the edge of the raceway groove is Ho, 1.00 <(PCD / dm) ≦ 1.05 and at least Hi , Ho is a ball bearing, wherein Hi ≧ 0.15 Da or Ho ≧ 0.15 Da. The ball bearing according to claim 1, wherein the ball bearing is a single row in which a plurality of balls are arranged in a row along the raceway grooves.

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