Bearing support structure

Abstract

A cylinder block (1) has a bearing fitting hole (2) formed so as to penetrate same, and herein, a bearing (4) is press-fitted, and a snap ring (5) is disposed. The inner circumferential surface of the bearing fitting hole (2) is divided into a bearing press-fitting circular cylindrical surface (2A) and an entrance circular cylindrical surface (2B) on the entrance side, which are intermediated by a snap ring holding groove (7). The bearing press-fitting circular cylindrical surface (2A) is set to have a diameter smaller than a reference diameter of the outer circumferential surface of the bearing (4) so that the bearing (4) is in an interference fit relationship. The entrance circular cylindrical surface (2B) is set to have a diameter larger than the reference diameter so that the bearing (4) is not in an interference fit relationship.

Description

Bearing support structure

[0001] The present invention relates to a bearing support structure in which a bearing is press-fitted into a bearing fitting hole, and a snap ring is disposed in a snap ring retaining groove formed on the inlet side of the bearing fitting hole.

[0002] In order to dispose a bearing in a bearing fitting hole preformed in a metal member, as disclosed in Patent Document 1, after the bearing is press-fitted into the bearing fitting hole, a snap ring is attached to a snap ring retaining groove provided on the inlet side of the bearing fitting hole. A configuration in which this is often adopted. The press-fitted bearing and the inner peripheral surface of the bearing fitting hole have a so-called shrink-fit relationship. Therefore, the bearing is retained at a predetermined position when it is press-fitted. However, a snap ring is added in consideration of万一の脱落を考慮してスナップリングが付加されている。

[0003] In order to obtain a press-fit, that is, a shrink-fit relationship, the diameter of the cylindrical surface of the inner periphery of the bearing fitting hole is set to be slightly smaller than the reference diameter (in other words, the design value) of the outer peripheral surface of the bearing. In the bearing press-fitting process, a bearing having a relatively large outer diameter is press-fitted from the inlet side of the bearing fitting hole, crosses the snap ring retaining groove, and advances to a predetermined bearing arrangement position.

[0004] During such a bearing press-fitting process, in a portion on the upstream side, that is, the inlet side, of the snap ring retaining groove of the bearing fitting hole, as a result of the inner peripheral surface of the bearing fitting hole coming into strong contact with the outer peripheral surface of the bearing having a relatively large diameter, the base material may be scraped and minute metal pieces may be generated. Such minute metal pieces generated on the upstream side of the snap ring retaining groove move along with the progress of the bearing press-fitting process, that is, the movement of the bearing, and are liable to adhere to the opening edge of the snap ring retaining groove whose diameter expands. Therefore, there is a possibility that a device including a bearing may be assembled with foreign matter consisting of minute metal pieces remaining in the snap ring retaining groove.

[0005] As a result, there has been a concern that foreign matter detached from the snap ring retaining groove during the operation of the device may enter the bearing and impair the function of the bearing.

[0006] Japanese Patent Application Publication No. 6-106427

[0007] This invention relates to a bearing support structure in which a bearing is press-fitted into a bearing fitting hole formed in a metal member, and a snap ring is placed in a snap ring retaining groove formed on the inlet side of the bearing fitting hole. The inner circumferential surface of the bearing fitting hole is divided, via the snap ring retaining groove, into a bearing press-fit cylindrical surface that holds the bearing and an inlet cylindrical surface that is on the inlet side of the snap ring retaining groove. The bearing press-fit cylindrical surface is set to a diameter smaller than the reference diameter of the outer circumferential surface of the bearing so that the bearing is in a tie-fit relationship, and the inlet cylindrical surface is set to a diameter larger than the reference diameter so that the bearing is not in a tie-fit relationship.

[0008] By setting the diameter of the inlet cylindrical surface, which is on the inlet side of the snap ring retaining groove, to be larger than the reference diameter, the bearing does not become a tight fit, thereby preventing the generation of minute metal fragments due to strong friction between the two. Consequently, it prevents the subsequent intrusion of foreign matter into the bearing.

[0009] Front view of a cylinder block showing an example of a metal component with bearing fitting holes. Cross-sectional view along line A-A in Figure 1. Enlarged view of the snap ring retaining groove in Figure 2.

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Figure 1 shows the front end surface of a cylinder block 1, which constitutes the main body of an engine, as an example of a metal member to which the bearing support structure of one embodiment is applied. This cylinder block 1 is a cylinder block for an in-line multi-cylinder engine equipped with a balancer shaft for vibration suppression, and is provided with a circular bearing fitting hole 2 that rotatably supports the front end of the balancer shaft, which is arranged in parallel with the crankshaft, via a bearing.

[0011] Figure 2 shows a cross-section along the line A-A in Figure 1. A cylindrical bearing fitting hole 2 is formed through the front wall 3, which forms part of the cylinder block 1. The left side of Figure 2 is the outer surface of the cylinder block 1, and the right side of Figure 2 is the space in which the weight portion of a balancer shaft (not shown) rotates. Figure 2 shows the bearing 4 and snap ring 5 installed in the bearing fitting hole 2, but since these bearings 4 and snap rings 5 ​​are not essential parts of the present invention, they are shown in a simplified manner for explanatory purposes. In one preferred embodiment, the bearing 4 is a roller bearing, but in the present invention, any type of bearing may be used. The bearing 4 is pressed into the bearing fitting hole 2 from the left side of Figure 2 using a known bearing press-fitting device, and then a general snap ring 5 is installed from the left side of the figure.

[0012] The bearing fitting hole 2 is equipped with a snap ring retaining groove 7 on the entrance side for mounting a snap ring 5. The snap ring retaining groove 7 has a rectangular cross-section and is continuous around its entire circumference.

[0013] The inner circumferential surface of the bearing fitting hole 2 is divided into a bearing press-fit cylindrical surface 2A that holds the bearing 4 via the snap ring retaining groove 7, and an inlet cylindrical surface 2B that is on the inlet side of the snap ring retaining groove 7. Both of these are cylindrical surfaces. Further towards the inlet side of the inlet cylindrical surface 2B is a guide surface 8 which is a conical surface that widens outward from the front wall 3. The guide surface 8 has the function of centering the bearing 4 when it is press-fitted.

[0014] The bearing press-fit cylindrical surface 2A is set to a diameter slightly smaller than the reference diameter (in other words, the design value) of the outer surface of the bearing 4 so that the bearing 4 is in a restrain fit. In contrast, the inlet cylindrical surface 2B is set to a diameter slightly larger than the reference diameter so that the bearing 4 is not in a restrain fit.

[0015] Figure 3 is an enlarged view of the main part of Figure 2. In a preferred embodiment, a first chamfered portion 10A is provided at the boundary between the snap ring retaining groove 7 and the bearing press-fit cylindrical surface 2A, and a second chamfered portion 10B is provided at the boundary between the snap ring retaining groove 7 and the inlet cylindrical surface 2B. The first chamfered portion 10A and the second chamfered portion 10B are symmetrical in shape and are machined simultaneously with a single tool. For example, both are subjected to linear chamfering (so-called C-chamfering) at an inclination angle of 45°. The chamfering of these two chamfered portions 10A and 10B is performed such that, with respect to the first chamfered portion 10A, for example, a chamfer is applied over a radial distance of 0.5 mm. The second chamfered portion 10B is smaller than the first chamfered portion 10A because the diameter of the inlet cylindrical surface 2B is relatively larger than the diameter of the bearing press-fit cylindrical surface 2A.

[0016] In one preferred embodiment, the diameter of the inlet cylindrical surface 2B is set to a diameter such that the second chamfered portion 10B does not disappear. In other words, regardless of the machining order, the diameter of the inlet cylindrical surface 2B is set to a range in which the second chamfered portion 10B, which is basically symmetrical to the first chamfered portion 10A, can remain. Therefore, if the radial dimension of the first chamfered portion 10A is 0.5 mm as in the above example, the difference between the diameter of the inlet cylindrical surface 2B and the diameter of the bearing press-fit cylindrical surface 2A will be less than 1.0 mm.

[0017] Furthermore, as shown in Figure 3, the snap ring retaining groove 7 has a first end face 7A and a second end face 7B, which are planes facing each other in the axial direction. For example, the first end face 7A is on the bearing press-fit cylindrical surface 2A side, and the second end face 7B is on the inlet cylindrical surface 2B side. In a preferred embodiment, the diameter of the inlet cylindrical surface 2B is set within a range in which the radial width of the first end face 7A that can contact the snap ring 5 and the radial width of the second end face 7B are kept equal to each other. In the illustrated example, since the first chamfered portion 10A and the second chamfered portion 10B are formed in a symmetrical shape, the radial width of the first end face 7A that can contact the snap ring 5 and the radial width of the second end face 7B are equal to each other.

[0018] If the diameter of the inlet cylindrical surface 2B is set such that the symmetrical second chamfered portion 10B does not remain, the radial width of the second end face 7B that can contact the snap ring 5 becomes smaller than the radial width of the first end face 7A that can contact the snap ring 5. This means that the snap ring 5 held in the snap ring holding groove 7 is more likely to fall out towards the inlet side (inlet cylindrical surface 2B side), which is undesirable.

[0019] In the bearing fitting hole 2 configuration described above, the bearing 4 is press-fitted into the bearing fitting hole 2 from the outer surface of the cylinder block 1 on the left side of Figure 2 using a bearing press-fitting device (not shown). At this time, the inlet cylindrical surface 2B, which is on the inlet side of the snap ring retaining groove 7, has a relatively larger diameter than the reference diameter of the outer surface of the bearing 4, so there is no strong contact that would generate minute metal fragments. In other words, the bearing 4 passes through the inlet cylindrical surface 2B without being in a tie fit and proceeds to the bearing press-fitting cylindrical surface 2A. Within the bearing press-fitting cylindrical surface 2A, the bearing 4 and the bearing press-fitting cylindrical surface 2A are in a tie fit relationship, and the bearing 4 is held in this predetermined position by being press-fitted to a predetermined axial position.

[0020] During the press-fitting process, the outer surface of the bearing 4 comes into strong contact with the cylindrical surface 2A of the bearing press-fitting, which may generate tiny metal fragments. However, even if tiny metal fragments are generated, these foreign objects are discharged into the large space inside the cylinder block 1 through which the bearing fitting hole 2 passes (the space in which the weight rotates), so the possibility of them entering the bearing 4 is low.

[0021] In one embodiment, the outer circumferential surface of the bearing 4 (the outer circumferential surface of the outer race) is generally made of steel, while the cylinder block 1 is made of an aluminum alloy, which has relatively lower hardness. Under these hardness differences, there is a growing concern that the metal surface of the cylinder block 1 will be scraped off during the press-fitting process, resulting in the generation of tiny metal fragments.

[0022] Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment and various modifications are possible. For example, the present invention can be broadly applied to bearing support structures in metal members other than the cylinder block 1. Also, the above dimensions are merely examples. Furthermore, the first chamfered portion 10A and the second chamfered portion 10B may be individually chamfered into, for example, different shapes.

Claims

1. A bearing support structure in which a bearing is press-fitted into a bearing fitting hole formed in a metal member, and a snap ring is placed in a snap ring retaining groove formed on the inlet side of the bearing fitting hole, wherein the inner circumferential surface of the bearing fitting hole is divided by the snap ring retaining groove into a bearing press-fit cylindrical surface that holds the bearing and an inlet cylindrical surface that is on the inlet side of the snap ring retaining groove, the bearing press-fit cylindrical surface is set to a diameter smaller than the reference diameter of the outer circumferential surface of the bearing so that the bearing is in a tie-fit relationship, and the inlet cylindrical surface is set to a diameter larger than the reference diameter so that the bearing is not in a tie-fit relationship.

2. The bearing support structure according to claim 1, wherein the snap ring retaining groove has a first chamfered portion at the boundary between the snap ring retaining groove and the bearing press-fit cylindrical surface, and the inlet cylindrical surface has a second chamfered portion at the boundary between the snap ring retaining groove and the inlet cylindrical surface, the chamfered portion having a shape symmetrical to the first chamfered portion, and the diameter of the inlet cylindrical surface is set such that the second chamfered portion does not disappear.

3. The bearing support structure according to claim 1, wherein the snap ring retaining groove has a first end face and a second end face, each consisting of a plane facing each other in the axial direction, and the diameter of the inlet cylindrical surface is set within a range such that the radial width of the first end face that can contact the snap ring and the radial width of the second end face are kept equal to each other.

4. The bearing support structure according to claim 1, wherein the metal member is made of an aluminum alloy with a lower hardness than the outer circumferential surface portion of the bearing.

5. The bearing support structure according to claim 1, wherein the above-mentioned metal member is a member that constitutes the main body of the engine.

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