Multi-row bearings and bearing units

Abstract

Provided are: a multi-row bearing which makes it possible to measure an axial dimension of a portion between raceway grooves with high accuracy and ease in a short time, thereby allowing processing of a portion between the raceway grooves with high dimensional accuracy; and a bearing unit provided with the multi-row bearing. In a multi-row bearing (10), an inner ring raceway groove (31a) of a one axial end part is formed between groove shoulders on both axial sides of a groove bottom, and an inner ring raceway groove (31b) of an axial intermediate part is formed between the groove bottom and one of the groove shoulders on one axial side. Further, an outer ring raceway groove (21a) of another axial end part is formed between groove shoulders on both axial sides of a groove bottom, and an outer ring raceway groove (21b) of the axial intermediate part is formed between the groove bottom and one of the groove shoulders on one axial side.

Description

[Technical Field]

[0001] The present invention relates to a multi-row bearing and bearing unit, and in particular to a multi-row bearing and bearing unit that enable the axial dimension between raceway grooves of a multi-row bearing to be measured simply and accurately, thereby enabling the raceway grooves to be machined with high precision. [Background technology]

[0002] Patent Document 1 discloses a thrust and radial bearing having multiple rows of raceway grooves in the inner and outer rings, where each raceway groove in the inner ring is formed over groove shoulders on both axial sides of the raceway groove, and each raceway groove in the outer ring is formed over groove shoulders on one axial side of the raceway groove.The inner ring is inserted into the outer ring, balls are inserted between the raceway grooves through radial holes drilled in the outer ring, and then the outer ring is moved axially to assemble.

[0003] In machining the raceway grooves of such multi-row bearings, the axial dimensions between the raceway grooves of the inner and outer rings must be consistent, so the axial dimensions between the raceway grooves are measured and adjusted to the target dimensions while machining. Therefore, measurements are usually taken multiple times during machining, so a simple, quick, and accurate measurement is required. If a simple method for measurement is not possible, the workpiece must be removed from the machining machine, measured, and then remounted on the machine for machining, which is an undesirable machining method that is extremely costly and time-consuming.

[0004] An example of a measuring tool that can perform measurements simply and in a short time is measuring tool 50 having the structure shown in Fig. 3. As will be described in detail later, measuring tool 50 is configured so that a pair of steel balls 55, 56 are engaged with raceway grooves that serve as a reference for measurement to stably hold measuring tool 50, and then probe 57 is pressed against the raceway groove to be measured to measure the axial distance between the raceway grooves. In order to stably hold measuring tool 50, it is preferable that the raceway groove that serves as the reference has raceway grooves formed on both sides of the groove bottom. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 4-262120 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the bearing of Patent Document 1, each raceway groove of the outer ring is formed only from the groove bottom to the groove shoulder on one side in the axial direction, so that the measuring tool 50 for measuring the dimension between the raceway grooves cannot be stably installed, resulting in unstable measurement values ​​and making it difficult to machine an outer ring with high dimensional accuracy between the raceway grooves.

[0007] The present invention has been made in view of the above-mentioned problems, and its object is to provide a multi-row bearing and a bearing unit equipped with the multi-row bearing in which the axial dimension between raceway grooves can be measured accurately, simply, and in a short time, thereby enabling the raceway grooves to be machined with high dimensional accuracy. [Means for solving the problem]

[0008] The above object of the present invention is achieved by the following configuration [1] relating to a multi-row bearing. [1] An inner ring having multiple inner ring raceway grooves; an outer ring having multiple rows of outer ring raceway grooves; a plurality of balls disposed between the multiple rows of inner ring raceway grooves and the multiple rows of outer ring raceway grooves; A multi-row bearing comprising: the inner ring raceway groove at one axial end is formed across groove shoulders on both axial sides of the groove bottom, the inner ring raceway groove in the axially intermediate portion is formed from the groove bottom to a groove shoulder on one side in the axial direction, the outer ring raceway groove at the other axial end is formed across groove shoulders on both axial sides of the groove bottom, A multi-row bearing, wherein the outer ring raceway groove in the axially intermediate portion is formed from the groove bottom to a groove shoulder on one axial side.

[0009] The above object of the present invention is achieved by the following configuration [2] relating to the bearing unit. [2] A ball screw mechanism; The multi-row bearing according to [1] above, A bearing unit, wherein a nut of the ball screw mechanism constitutes the inner ring. [Effects of the Invention]

[0010] According to the multi-row bearing of the present invention, the axial dimension between the raceways can be measured accurately, simply, and in a short time, thereby enabling the machining of raceway grooves for a multi-row bearing with high dimensional accuracy between the raceways and stable quality.Furthermore, a compact, inexpensive bearing unit that is equipped with this multi-row bearing and can withstand high loads can be obtained. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view showing a multi-row bearing having three rows of raceway grooves in a state before assembly. [Figure 2] FIG. 2 is a cross-sectional view showing the state after the multiple row bearing shown in FIG. 1 has been assembled. [Figure 3] Figure 3(a) is a side view of a measuring tool for measuring the axial dimension between the raceway grooves of a multi-row bearing, and Figure 3(b) is a side view showing the state in which the measuring tool is used to measure the axial dimension between the raceway grooves of a multi-row bearing. [Figure 4] FIG. 4 is a cross-sectional view showing a state before assembly of a multi-row bearing having four rows of raceway grooves. [Figure 5] FIG. 5 is a cross-sectional view showing the state after the multiple row bearing shown in FIG. 4 has been assembled. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, each embodiment of the multi-row bearing according to the present invention will be described in detail with reference to the drawings. (First embodiment)

[0013] Fig. 1 is a cross-sectional view showing a state before assembly of a multi-row bearing according to a first embodiment of the present invention, and Fig. 2 is a cross-sectional view showing a state after assembly of the multi-row bearing. In the following explanation, the left side in the drawings will be referred to as one side, and the right side will be referred to as the other side.

[0014] As shown in Figures 1 and 2, the bearing unit 100 according to the first embodiment is composed of a multi-row bearing 10 and a ball screw mechanism 40 that uses the inner ring 30 of the multi-row bearing 10 as a nut.

[0015] The multi-row bearing 10 of this embodiment comprises an outer ring 20 having three rows of outer ring raceway grooves 21a, 21b, 21c on its inner peripheral surface, an inner ring 30 having three rows of inner ring raceway grooves 31a, 31b, 31c on its outer peripheral surface, and a plurality of balls 45 arranged so as to roll freely between each of the outer ring raceway grooves 21a, 21b, 21c and each of the inner ring raceway grooves 31a, 31b, 31c.

[0016] The outer ring raceway groove 21a formed at the other axial end of the outer ring 20 is formed across groove shoulders on both axial sides. Specifically, it is formed line-symmetrically with respect to the groove bottom. Furthermore, the two outer ring raceway grooves 21b, 21c, respectively formed in the axially intermediate portion and one axial end portion of the outer ring 20, are formed from the groove bottom to the groove shoulder on one axial side (the other side). Specifically, the raceway grooves 21b, 21c are formed only on the other side of the groove bottom. That is, the outer ring raceway groove 21a has a raceway groove with a substantially semicircular cross section, and the outer ring raceway grooves 21b, 21c have raceway grooves with a substantially quarter-circular cross section formed on the other side of the outer ring 20.

[0017] Furthermore, a cylindrical surface 21e continuing from the groove bottom of the outer ring raceway groove 21b is formed between the outer ring raceway groove 21b and the outer ring raceway groove 21c. A cylindrical surface 21f continuing from the groove bottom of the outer ring raceway groove 21c is also formed on one axial side of the outer ring raceway groove 21c. The inner diameter of the groove bottom of the outer ring raceway groove 21b and the inner diameter of the cylindrical surface 21e are substantially the same, and the inner diameter of the groove bottom of the outer ring raceway groove 21c and the inner diameter of the cylindrical surface 21f are also substantially the same. Furthermore, an opening 22 penetrating radially is provided in the cylindrical surface 21e. The inner diameters of the cylindrical surfaces 21e and 21f may be different from the inner diameters of the outer ring raceway grooves 21b and 21c, as long as they do not interfere with the balls during ball installation, as described below.

[0018] The inner ring 30, which also serves as a nut for the ball screw mechanism 40 as will be described later, is a split inner ring consisting of an axially long, substantially bottomed, cylindrical inner ring body 31 having a bottomed hole 34 with a bottom 33 at the other end, and a presser cover 32. An inner ring raceway groove 31a formed at one end of the inner ring body 31 is formed across groove shoulders on both sides in the axial direction. Specifically, the inner ring raceway groove 31a is formed symmetrically with respect to the groove bottom.

[0019] Furthermore, the inner ring raceway groove 31b, which is formed in the axially intermediate portion of the inner ring 30, is formed from the groove bottom to a groove shoulder on one axial side (one side). Specifically, the raceway groove is formed only on one side of the groove bottom. On the other side of the inner ring raceway groove 31b, a cylindrical surface 31f is formed that continues from the groove bottom of the inner ring raceway groove 31b. The outer diameter of the groove bottom of the inner ring raceway groove 31b and the outer diameter of the cylindrical surface 31f are approximately the same diameter. The inner diameter of the cylindrical surface 31f may be different from the inner diameter of the inner ring raceway groove 31b, as long as it does not interfere with the balls during ball assembly, as described below.

[0020] Presser lid 32 is a component fixed to inner ring main body 31 to form inner ring raceway groove 31c, and has a raceway groove with a cross section of approximately 1 / 4 of a circle formed in an outer diameter corner on one side to become inner ring raceway groove 31c. Presser lid 32 also has a screw hole 36 through which a bolt (not shown) is inserted to screw into a female thread 35 provided in bottom 33 of inner ring main body 31 to fix presser lid 32 to inner ring main body 31.

[0021] Furthermore, although not shown in detail, a ball screw groove 41 (nut-side ball screw groove) of a ball screw mechanism 40 is formed on the inner peripheral surface of the bottomed hole 34 of the inner ring body 31, and a ball screw shaft 43 having a ball screw groove 42 (screw-shaft-side ball screw groove) formed on its outer peripheral surface is rotatably housed inside the bottomed hole 34. A plurality of balls (not shown) are arranged to roll freely between the inner ring body 31, i.e., the ball screw groove 41 of the nut, and the ball screw groove 42 of the ball screw shaft 43.

[0022] That is, the bearing unit 100 is formed by combining the ball screw mechanism 40, which is composed of an inner ring body 31 having a ball screw groove 41 on its inner surface and functioning as a nut for the ball screw mechanism 40, a ball screw shaft 43, and balls (not shown), with the multi-row bearing 10.

[0023] Next, we will explain how to assemble the outer ring 20, the inner ring 30, and the plurality of balls 45. First, as shown in Fig. 1, the outer ring 20 is placed over the inner ring 30 with the outer ring 20 slightly shifted to the other side. In this state, the opening 22 of the outer ring 20 is positioned corresponding to the inner ring raceway groove 31b.

[0024] Then, a plurality of balls 45 are loaded from one side between the inner ring raceway groove 31a and the cylindrical surface 21f of the outer ring 20. A plurality of balls 45 are loaded from the opening 22 between the inner ring raceway groove 31b and the cylindrical surface 21e. A plurality of balls 45 are then loaded from the other side into the outer ring raceway groove 21a and held down by the holding lid 32.

[0025] 2, the outer ring 20 is slid to one side together with the retaining cover 32, the retaining cover 32 is used to adjust the gaps between the balls 45 and the outer ring raceway groove 21a and the inner ring raceway groove 31c to predetermined values, and a bolt (not shown) inserted through a screw hole 36 of the retaining cover 32 is screwed into the female thread 35 to secure the retaining cover 32 to the inner ring body 31. As a result, the plurality of balls 45 are arranged rollably between the respective raceway grooves, i.e., between the inner ring raceway groove 31a and the outer ring raceway groove 21c, the inner ring raceway groove 31b and the outer ring raceway groove 21b, and the inner ring raceway groove 31c and the outer ring raceway groove 21a, and the three-row multi-row bearing 10 is assembled.

[0026] Although not shown in detail, when the inner ring 30, i.e., one of the nut and the ball screw shaft 43 (e.g., the ball screw shaft 43) is constrained from rotating while the other (e.g., the inner ring 30) is driven to rotate, the ball screw shaft 43 moves in the axial direction relative to the inner ring 30. When a load is applied to one end of the ball screw shaft 43 toward the other axial direction, a load P indicated by an arrow in the drawing acts on the ball screw shaft 43. This load P is received by the multi-row bearing 10, which has multiple rows of raceway grooves, and therefore a large load P can be supported.

[0027] To ensure smooth operation of the multi-row bearing 10 configured in this manner, it is necessary that the axial positions of the three rows of outer ring raceway grooves 21a, 21b, 21c and the three rows of inner ring raceway grooves 31a, 31b, 31c match with high precision. In other words, the machining precision of the outer ring raceway grooves 21a, 21b, 21c and the inner ring raceway grooves 31a, 31b, 31c greatly affects the performance of the multi-row bearing 10.

[0028] Because the inner ring raceway grooves 31a, 31b, and 31c are formed on the outer periphery, they are relatively easy to measure and process, but because the outer ring raceway grooves 21a, 21b, and 21c are formed on the inner periphery, they are difficult to process and require measuring and adjusting the axial dimension between the raceway grooves during processing. Therefore, the dimension between the raceway grooves must be measured multiple times during processing, and the measuring tool must be able to perform the measurement simply, quickly, and with high accuracy.

[0029] The axial dimension between the raceway grooves is measured using a dedicated measuring tool 50, as shown in Fig. 3. Hereinafter, an example of measuring the axial dimension between the raceway grooves of the outer ring 20 will be described.

[0030] 3(a), measuring tool 50 comprises fixed arm 52 fixed to support shaft 51, movable arm 53 that can swing around support shaft 51, and measuring arm 54 that is provided so as to be able to slide relative to fixed arm 52. Steel balls 55, 56 of the same size as ball 45 used in multi-row bearing 10 are attached to the tips of fixed arm 52 and movable arm 53, and a measuring element (steel ball) 57 of the same size as ball 45 used in multi-row bearing 10 is also attached to the tip of measuring arm 54.

[0031] By swinging the movable arm 53 relative to the fixed arm 52, the gap between the steel balls 55, 56 is narrowed and they are inserted into the inner diameter of the outer ring 20. Then, as shown in Figure 3(b), the steel balls 55, 56 on the fixed arm 52 and the movable arm 53 are fitted into a pair of outer ring raceway grooves 21a of the opposing outer ring 20, thereby stably holding the measuring tool 50. In other words, the outer ring raceway grooves 21a of the outer ring 20, in which raceway grooves are formed on both sides of the groove bottom, serve as reference grooves for measuring the distance between raceway grooves.

[0032] With measuring tool 50 stably held on outer ring 20, movable arm 53 is extended or retracted in the direction of the arrow to engage probe 57 with outer ring raceway groove 21b or 21c to be measured, and the axial dimension between the raceway grooves is measured from the distance traveled by measuring arm 54. In this way, outer ring raceway groove 21a, where raceway grooves are formed on both sides of the groove bottom, is used as a reference, and the axial distances to the remaining outer ring raceway grooves 21b and 21c are measured with high precision, allowing outer ring raceway grooves 21b and 21c to be machined with high precision using outer ring raceway groove 21a as a reference.

[0033] Therefore, there is no need to remove the outer ring 20 being machined from the machining device every time the axial dimension between the raceway grooves is measured, which improves work efficiency and enables the outer ring raceway grooves to be machined with high precision.

[0034] (Second embodiment) Next, a multi-row bearing 10 according to a second embodiment of the present invention will be described with reference to Figures 4 and 5. In the multi-row bearing 10 according to the second embodiment, four rows of outer ring raceway grooves 21a, 21b, 21c, and 21d are formed on the inner peripheral surface of the outer ring 20, and four rows of inner ring raceway grooves 31d, 31c, 31b, and 31a are formed on the outer peripheral surface of the inner ring 30, facing the outer ring raceway grooves 21a, 21b, 21c, and 21d.

[0035] Of the outer ring raceway grooves 21a, 21b, 21c, and 21d of the outer ring 20, the outer ring raceway grooves 21b and 21c located between the outer ring raceway grooves 21a and 21d formed at one end and the other end have cylindrical surfaces 21e that continue from the groove bottoms of the outer ring raceway grooves 21b and 21c, respectively, and these two cylindrical surfaces 21e are provided with openings 22 that penetrate radially.

[0036] In the multi-row bearing 10 according to the second embodiment, the axial dimension between the raceway grooves can also be measured accurately and in a short time using the measuring tool 50 shown in Fig. 3, with the outer ring raceway groove 21a as the reference. This allows the other outer ring raceway grooves 21b, 21c, and 21d to be machined accurately, with the outer ring raceway groove 21a as the reference.

[0037] Furthermore, the method of assembling the outer ring 20, inner ring 30, and plurality of balls 45, and further, although not shown, the fact that the inner ring 30 is used as a nut and the ball screw shaft 43 is placed inside the nut to form the ball screw mechanism 40, are also the same as those of the multi-row bearing 10 of the first embodiment. In this case, the multi-row bearing 10 of the second embodiment has four rows of raceway grooves, and can therefore support a greater load than the multi-row bearing 10 of the first embodiment.

[0038] Other parts are the same as those of the multi-row bearing 10 of the first embodiment of the present invention, so the same or corresponding reference numerals are used for the same parts, and the description thereof will be simplified or omitted.

[0039] The present invention is not limited to the above-described embodiments, and modifications and improvements are possible as appropriate.

[0040] As described above, the present specification discloses the following: (1) an inner ring having multiple inner ring raceway grooves; an outer ring having multiple rows of outer ring raceway grooves; a plurality of balls disposed between the multiple rows of inner ring raceway grooves and the multiple rows of outer ring raceway grooves; A multi-row bearing comprising: the inner ring raceway groove at one axial end is formed across groove shoulders on both axial sides of the groove bottom, the inner ring raceway groove in the axially intermediate portion is formed from the groove bottom to a groove shoulder on one side in the axial direction, the outer ring raceway groove at the other axial end is formed across groove shoulders on both axial sides of the groove bottom, A multi-row bearing, wherein the outer ring raceway groove in the axially intermediate portion is formed from the groove bottom to a groove shoulder on one axial side. This configuration makes it possible to measure the axial dimension between the raceway grooves accurately, simply, and in a short time, thereby enabling the machining of raceway grooves for multi-row bearings with high dimensional accuracy between the raceway grooves and stable quality.

[0041] (2) The multi-row bearing according to (1), wherein the cylindrical surface of the outer ring in the axially intermediate row is provided with an opening that penetrates radially. With this configuration, balls can be easily loaded into the raceway grooves in the axially intermediate portion through the opening, and the multiple-row bearing can be easily assembled.

[0042] (3) The outer ring raceway groove in the axially intermediate portion has a cylindrical surface on the opposite side of the groove shoulder with respect to the groove bottom, The multi-row bearing according to (1) or (2), wherein the inner ring raceway groove in the axially intermediate portion has a cylindrical surface on the opposite side of the groove shoulder with respect to the groove bottom. According to this configuration, by sliding the outer ring in the axial direction, the balls loaded through the opening can be sandwiched between the outer ring raceway groove and the inner ring raceway groove.

[0043] (4) The multi-row bearing according to any one of (1) to (3), wherein the inner ring raceway groove at the other axial end is formed by a divided inner ring. According to this configuration, the inner ring raceway formed at the other end of the multi-row bearing can be easily formed.

[0044] (5) a ball screw mechanism; The multi-row bearing according to any one of (1) to (4), A bearing unit, wherein a nut of the ball screw mechanism constitutes the inner ring. According to this configuration, by combining the multi-row bearing with the ball screw mechanism, it is possible to configure a bearing unit that is capable of axial movement and can support a large thrust load.

[0045] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention. Furthermore, the components of the above-described embodiments may be combined in any manner without departing from the spirit of the invention.

[0046] This application is based on a Japanese patent application (Patent Application No. 2021-062354) filed on March 31, 2021, the contents of which are incorporated by reference into this application. [Explanation of symbols]

[0047] 10 Multi-row bearing 20 outer ring 21a~21d Outer ring raceway groove 21e, 21f, 31f Cylindrical surface 22 Opening 30 Inner ring (nut of ball screw mechanism) 31a~31d Inner ring raceway groove 32 Presser lid (split inner ring) 40 Ball screw mechanism 45 Ball 100 bearing unit

Claims

1. an inner ring having multiple rows of inner ring raceway grooves; an outer ring having multiple rows of outer ring raceway grooves; a plurality of balls disposed between the multiple rows of inner ring raceway grooves and the multiple rows of outer ring raceway grooves; A multi-row bearing comprising: the inner ring raceway groove at one axial end is formed across groove shoulders on both axial sides of the groove bottom, the inner ring raceway groove in the axially intermediate portion is formed from the groove bottom to a groove shoulder on one side in the axial direction, the outer ring raceway groove at the other axial end is formed across groove shoulders on both axial sides of the groove bottom, A multi-row bearing, wherein the outer ring raceway groove in the axially intermediate portion is formed from the groove bottom to a groove shoulder on one axial side.

2. The multi-row bearing according to claim 1 , wherein an opening extending radially through the cylindrical surface of the outer ring in the axially intermediate row is provided.

3. the outer ring raceway groove in the axially intermediate portion has a cylindrical surface on the opposite side of the groove shoulder with respect to the groove bottom, 3. The multi-row bearing according to claim 1, wherein the inner ring raceway groove in the axially intermediate portion has a cylindrical surface on the opposite side of the groove bottom from the groove shoulder.

4. 4. The multi-row bearing according to claim 1, wherein the inner ring raceway groove at the other axial end is formed by a split inner ring.

5. A ball screw mechanism; The multi-row bearing according to any one of claims 1 to 4, A bearing unit, wherein a nut of the ball screw mechanism constitutes the inner ring.

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