GB2503794A

GB2503794A - Half Bearing and Plain Bearing

Info

Publication number: GB2503794A
Application number: GB1309162.4A
Authority: GB
Inventors: Osamu Ishigo; Motohiko Koushima
Original assignee: Daido Metal Co Ltd
Current assignee: Daido Metal Co Ltd
Priority date: 2012-05-23
Filing date: 2013-05-21
Publication date: 2014-01-08
Anticipated expiration: 2033-05-21
Also published as: DE102013209346A1; GB201309162D0; JP5801753B2; DE102013209346B4; GB2503794B; JP2013242028A

Abstract

The half bearing 31 supports a crank shaft of an internal combustion engine. The half bearing 31 includes a main cylindrical part 71 with a plurality of circumferential grooves 74 and crush reliefs 70 with a plurality of crush relief grooves 75. A groove width of the crush relief grooves 75 is the same as a groove width of the circumferential grooves 74. The plurality of crush relief grooves 75 are offset with respect to the plurality of circumferential grooves 74 in a width-wise direction of the half hearing by an amount at least exceeding 0 and less than the groove width. The half bearing may have transition regions between the main cylindrical part and the crush relief and may have an inwardly convex and/or outwardly concave portion. Two half bearings may be assembled into a cylindrical shape.

Description

HALF BEARING AND PLAIN BEARING

BACKGROUND OF THE INVENTION

(1) FIELD OF THE INVENTION

The present invention relates to a half bearing that constitutes a plain bearing for supporting a crank shaft of an internal combustion engine and to a plain beanng having a pair of half bearings.

(2) DESCRIPTION OF RELATED ART

From the past, a plain bearing constituted by a pair of half bearings has been employed as a main bearing and a connecting rod bearing. A so-called crush relief is formed in a plain bearing adjacent to mating surfaces of half bearings.

A crush relief is a wall-thickness thinner region that is formed such that a thickness of a wall in a region adjacent to a circumferential end surface of a half bearing is thinner toward the circumferential end surface. A crush relief is formed with an intention of absorbing misalignment or deformation of joint surfaces of a pair of half bearings in a state where the half beanngs are assembled (see, for example, JP-A-4-219521 and JP-A-7-139539).

Further, in some cases, a plurality of circumferential grooves that continue in a circumferential direction are formed in an inner circumferential surface of a half bearing that constitutes a plain bearing. Generally. such circumferential grooves are formed to enhance retainability of lubricating oil in the inner circumferential surface of the half bearing.

However, in recent years, an oil pump has been reduced in size in an internal combustion engine, and thus an amount of lubricating oil supplied to the inner circumferential surface ofabearing has been decreasing. Accordingly, when assembling a pair of half bearings into a cylindrical shape, if the circumferential end surfaces thereof are misaligned, the inner circumferential surfaces of the bearings come into direct contact with a surface of a shaft, and damage to the inner circumferential surfaces of the bearings is likely to occur due to the heat.

Therefore, it is an object of the present invention to provide a half bearing that is less likely to be damaged even if circumferential end surfaces are misaligned when assembling a pair of half bearings into a cylindncal shape and a plain bearing formed by assembling such half bearings into a cylindrical shape.

BRIEF SUMMARY OF THE INVENTION

In order to accomplish the above-mentioned object, a half bearing of the present invention is a half bearing that supports a crank shaft of an internal combustion engine. The half bearing includes: a main cylindrical part that is formed to indude a center portion in a circumferential direction of the half beanng, the main cylindrical part being provided with a plurality of circumferential grooves that continue in the circumferential direction of the half bearing; and crush reliefs that are formed at both circumferential ends of the half bearing such that a thickness of a wall thereof is thinner than that of the main cylindrical part, the crush reliefs being provided with a plurality of crush relief grooves that continue in the circumferential direction of the half bearing. A groove width of the crush relief grooves is the same as a groove width of the circumferential grooves. The plurality of crush relief grooves are offset with respect to the plurality of circumferential grooves in a widthwise direction of the half bearing by an amount at least exceeding 0 arid at most less than the groove width.

Here, a crank shaft is interpreted as a member that includes a joumal part, a crank pin part. and a crank arm part. Further, a plain bearing is interpreted as a bearing that encompasses a connecting rod bearing and a main bearing. Furthermore, a half bearing is interpreted as a member that has such a shape that a cylinder is divided into half, which, however, should not be interpreted as being divided strictly into half A half bearing of the present invention is a half bearing that supports a crank shaft of an internal combustion engine and that constitutes a plain bearing formed by assembling a pair of half bearings. The half bearing includes a main cylindrical part provided with circumferential grooves and crush reliefs provided with crush relief grooves. Then, a groove width of the crush relief grooves is the same as a groove width of the circumferential grooves.

The plurality of crush relief grooves are offset with respect to the plurality of circumferential grooves in a widthwise direction of the half bearing by an amount at least exceeding 0 and at most less than the groove width.

Through such a configuration, in a state where the end surfaces of the half bearings are misaligned, an oil flow that is guided by the crush relief grooves to flow in the circumferential direction is subjected to the resistance at a connection position between the crush relief and the main cylindrical part, whereby a turbulent flow is generated. Accordingly, heat generated as a circumferential end of the main cylindrical part of the beanng comes into contact with a mating shaft is conducted efficiently to the turbulent oil flow, and thus the beanng is prevented from reaching such a high temperature that causes damage thereto.

Other purposes, features, and advantages of the present invention will become clear from the following description of the examples in relation to the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

Fig. I is a sectional view of a crank shaft of an internal combustion engine, cut at ajournal part and a crank pin part; Fig. 2 is a front view of a half beanng of Example 1; Fig. 3 is a bottom view of the half bearing of Example 1; Fig. 4 is a sectional view ofaplurality of circumferential grooves that are formed in a main cylindrical part of the half bearing of Example 1; Fig. 5 is an enlarged view of an A-section shown in Fig. 2; Fig. 6 is a developed view in which the main cylindrical part in the A-section is two-dimensionally devdoped to describe specific dimensions; Fig. 7 is an internal view showing a positional relationship between circumferential grooves and crush relief grooves in a half bearing of Example 1; Fig. 8 is a sectional view showing the circumferential grooves and the crush relief grooves in the half bearing of Example 1; Fig. 9 is a front view showing a state where circumferential end surfaces of the half beanngs of Example 1 are misaligned; Fig. 10 is an operation diagram for describing an operation of the half bearing of

Example 1;

Fig. 11 is a front view of a half beanng of Example 2; Fig. 12 is an enlarged view of an A-section shown in Fig. ii; Fig. 13 is a developed view in which the main cylindrical part in the A-section is two-dimensionally developed to describe specific dimensions; Fig. 14 is an operation diagram for describing an operation of the half bearing of

Example 2;

Fig. 15 is a sectional view showing a transition region of another mode; Fig. 16 is a sectional view showing a transition region of another mode; Fig. 17 is a sectional view showing a transition region of another mode; Fig. 18 is a front view showing a state where circumferential end surfaces of the half bearings are aligned; Fig. 19 is an operation view for describing an operation of the state where the circumferential end surfaces of the half bearings are aligned; Fig. 20 is a table showing test conditions and results of an effect confirmation test; Fig. 21 is a table showing test conditions of an effect confirmation test; Fig. 22 is an internal view showing a positional relationship between circumferential grooves and crush relief grooves in an existing hail bearing; and Fig. 23 is an operation diagram for describing an operation of an existing half bearing.

DETAILED DESCRIPTTON OF THE TNVENTTON

Hereinafter, examples of the present invention will be described with reference to the drawings. Note that a crush relief is depicted in exaggeration in the drawings in order to facilitate understanding.

EXAMPLE I

(Overall Configuration of Bearing Device) As shown in Fig. I, a bearing device i of the present example includes a journal part 6 that is supported by a lower part of a cylinder block 8, a crank pin part S that is formed integrally with the journal part 6 to rotate about the journal part 6. and a connecting rod 2 that conveys a reciprocating motion from an internal combustion engine to the crank pin part 5. The hearing device 1 further includes!' a main bearing 4 that rotatably supports the journal part 6 and a connecting rod bearing 3 that rotatably supports the crank pin part 5. as a plain bearing that supports a crank shaft.

Note that although the crank shaft has a plurality of journal parts 6 and a plurality of crank pin parts 5, here, for convenience of the description, a single journal part 6 and a single crank pin partS are shown for description. In Fig. 1, a positional relationship in a depthwise direction of the paper plane is such that the journal part 6 is in the back side of the paper plane and the crank pin part S is in the front side.

The journal part 6 is axially supported by a cylinder block lower part 81 of the interna' combustion engine through the main bearing 4 that is constituted by a pair of hail bearings 41 and 42. A lubricating oil groove 41a is formed in the half bearing 41 located at an upper side in Fig. 1 along an entire length in an inner circumferential surface. Further, the journal part 6 has a lubricating oil channel 6a that penetrates in a diametrical direction, and when the journal part 6 rotates in a direction shown by an arrow X, openings at both ends of the lubricating oil channel 6a alternately communicate with the lubncating oil groove 41a.

The crank pin part S is axially supported by a large-end housing 21 of the connecting rod 2 (a rod-side large-end housing 22 and a cap-side large-end housing 23) through the connecting rod bearing 3 that is constituted by a pair of half bearings 31 and 32.

As stated above, lubricating oil discharged by an oil pump to the main bearing 4 is fed into the lubricating oil groove 41a that is formed along the inner circumferential surface of the main bearing 4 through a through-hole formed in a wall of the main bearing 4 from an oil gallery that is formed in a cylinder block wall.

Further, a first lubricating oil channel 6a is formed to penetrate the journal part 6 in the diametrical direction, and the openings at both ends of the first lubricating oil channel 6a are in communication with the lubricating oil groove 4la. Then, a second lubricating oil channel Sa that passes through a crank arm part (not shown) is formed to branch off from the first lubricating oil channel 6a in the journal part 6, and the second lubricating oil channel 5a is iii communication with a third lubricating oil channel Sb that is formed to penetrate the crank pin part 5 in the diametrical direction.

In this way, the lubricating oil passes through the first lubricating oil channel 6a, the second lubricating oil channel 5a, and the third lubricating oil channel Sb to be supplied into a space that is formed between the crank pin part S and the connecting rod bearing 3 through an end outlet of the third lubricating oil channel Sb (that is, an outlet that opens in an outer circumferential surface of the crank pin part 5).

Hereinafter, although a descnption will be given with the connecting rod beanng 3 taken as an example of the plain bearing of the present invention, even with the main bearing 4, substantially the same configurations and operational effects are obtained.

(Configuration of Half Bearing) The connecting rod bearing 3 of the present example is formed into a generally cylindrical shape by assembling a pair of half bearings 31 and 32 such that the circumferential end surfaces thereof are joined with each other (see Fig. 9). Each of the half bearings 31(32) is formed into a semicylindrical shape with a bimetal in which a bearing alloy is thinly adhered onto a steel plate, as shown in Fig. 2, and includes a main cylindrical part 71 that is formed to include a center portion in the circumferential direction, crush reliefs 70, 70 that are formed at both circumferential ends.

The main cylindrical part 71 has a semicylindrical surface that occupies a large portion of the inner circumferential surface of the half bearing 31, and this sernicylindrical surface constitutes a primary sliding surface with a mating shaft. Further, a plurality of circumferential grooves 74, ... that continue in the circumferential direction are formed in the main cylindrical part 71 of the present example, as shown in Fig. 3.

The circumferential grooves 74 are formed along the entire length, in the circumferential direction, in the inner circumferential surface of the main cylindrical part 71 of the half bearing 31, as shown in Fig. 3. Furthermore, the circumferential grooves 74 are arranged iii plurality to be parallel to one another in a widthwise direction of the half bearing 31 and are formed to span across the entire width. Accordingly, the plurality of circumferential grooves 74, ... are formed over the entire region of the inner circumferential surface (semicylindncal surface) of the main cylindrical pail 71, and thus a planar region does not exist therein.

To describe in more detail, the circumferential groove 74 is formed into a circular arc shape (a shape where a circular arc section is in the back side) having a predeteirnined groove width WG and a predetermined groove depth DO, as shown in Fig. 4. In other words, individual circumferential grooves 74 are U-shaped cut grooves and are arranged in parallel in the widthwise direction at regular intervals (WG) to generally form a saw blade shaped or shallow comb-like shaped section. Here, the groove width WG refers to a distance between peaks of adjacent crests in the widthwise direction of the half bearing 31, and the groove depth DC refers to a distance from a peak of a crest to a bottom of a trough in a direction perpendicular to the inner circumferential surface. In particular, it is preferable that the circumferential grooves 74 have the groove width WG of 0.05 mm to 0.75 mm and the groove depth DC of I Jim to 8 km.

In addition, the plurality of circumferential grooves 74 all have the same groove width WG and the same groove depth DC, and the groove width WC and the groove depth DC are constant along the circumferential direction. Thus, a pressure loss (form loss) of the lubricating oil that flows in the circumferential grooves 74 can be prevented. Note that although it is preferable that the circumferential grooves 74 are circular arc shaped or U-shaped, the circumferential groove 74 may be in any shape that can guide a flow of the lubricating oil and may be V-shaped for example.

The crush relief 70 is a wall-thickness-reduced region that is formed in a region adjacent to a circumferential end surface 72 of the half bearing 3 i (see Fig. 5) such that a thickness of the wall is thinner than that of the main cylindrical part 71. The crush relief 70 is provided with an intention of absorbing misalignment or deformation of joining surfaces (circumferential end surfaces 72) in a state where the pair of half bearings 3 i and 32 are assembled to the connecting rod 2.

Then, as shown in Figs. 3 and 5, a plurality of crush relief grooves 75, ... that continue in the circumferential direction are formed in the crush relief 70 of the present example.

The crush relief grooves 75 are formed in the inner surface of the crush relief 70 along the entire length in the circumferential direction. Furthermore, the crush relief grooves 75 are arranged in plurality to be parallel to one another in the widthwise direction of the half bearing 31 and are formed to span across the entire width, and thus a planar region does not exist therein.

To describe more specifically, the crush relief grooves 75 are formed into a circular arc shape (a shape where a circubr arc section is in the back) having a predetermined groove width and a predetermined groove depth, as in the circumferential groove 74 in the main cylindrical part 71. The groove width is the same as the groove width WO of the circumferential groove 74. The groove depth is preferably the same as the groove depth DG of the circumferential groove 74, but the groove depth does not need to be the same. The shape is preferably a circular arc shape, but may also be a V-shape.

The crush relief 70 of the present example is formed such that a depth Dl at a position of the end surface 72 is greatest, as shown in Figs. 5 and 6. Here, the depth of the crush relief 70 refers to a distance to the surface (the tops of the crests) of the crush relief 70 from the imaginary inner circumferential plane in which the inner circumferential surface of the main cylindrical part 71 is extended over the crush relief 70. Further, the crush relief 70 of the present example is formed of an outwardly convex curved surface that outwardly projects in the radial direction of the half bearing 31.

Next, with reference to Fig. 6, specific dimensions of the crush relief 70 will be described. Fig. 6 is a developed view in which the inner circumferential surface of the main cylindrical part 71 is developed to be planar (linear along the section). A length Li and the depth Dl of the crush relief 70 may be the same as those of an existing crush relief. For example. although it may vary depending on the specifications of an internal combustion engine, in a case of a bearing for a small-sized internal combustion engine for an automobile, the length Li is approximately 3 mm to 7 mm, and the depth Dl is approximately 0.01 mm to 0.05 mm.

As shown in Figs. 3 and 7, the plurality of crush relief grooves 75, ... that continue in the circuniferential direction are formed in the crush relief 70. Then, the plurality of crush relief grooves 75, ... of the present example are offset with respect to the plurality of circumferential grooves 74, ... that are formed in the main cylindrical part 71 by a half of the groove width WG in the widthwise direction and are arranged such that the troughs (concave shaped openings of the crush relief grooves) of the crush relief grooves 75 correspond to the crests (convexities formed between two adjacent circumferential grooves 74) of the circumferential grooves 74 in the connecting position of the crush relief 70 and the main cylindrical part 71 (see Fig. 8). Accordingly, the oil flow of the lubricating oil is subjected to the resistance at the connecting position of the crush relief 70 and the main cylindrical part 71.

Note that although an example where the plurality of crush relief grooves 75.

are offset with respect to the plurality of circumferential grooves 74, ... that are formed in the main cylindrical part 71 by ahaff of the groove width WG in the widthwise direction is shown in the present example, the present invention is not limited thereto. The plurality of crush relief grooves 75, ... maybe offset with respect to the plurality of circumferential grooves 74, ... that are formed in the main cylindrical part 71 by an amount in a range greater than 0 and less than the groove width WU in the widthwise direction. In other words, it is sufficient that the crush relief grooves 75 and the circumferential grooves 74 are arranged such that the positions of the respective center portions in the groove widths are offset from each other by an amount in a range at least greater than 0 and at most less than the groove width WO in the widthwise direction of the half bearing 31 at the connection position of the crush relief 70 and the main cylindrical part 71.

(Operation) Subsequently, an operation of the half bearing 31 of the present example will be described with reference to Figs. 9 and 10.

A case is considered in which the vicinity of the circumferential end of the inner circumferential surface (the main cylindrical part 71) of the half bearing 31 (32) comes into direct contact with the surface of the mating shaft in a state where the circumferential end surfaces of the pair of half bearings 31 and 32 are misaligned as shown in Fig. 9. In this state, the main cylindrical surface of the main cylindncal part 71 and the surface of the crush relief 70 are in close proximity to the surface of the mating shaft at the vicinity of one end of the half bearing 31 which is misaligned inwardly (an upper right portion and a lower left portion in Fig. 9).

When the surface of the crush relief 70 and the surface of the mating shaft are in close proximity to each other, the oil flow Fl that flows near the surface of the crush relief 70 is first formed, as shown in Fig. 10.

The oH flow F] that flows near the surface of the crush relief 70 is guided in the crush relief grooves 75. Then, the oil flow F] enters the circumferential grooves 74 from the crush relief grooves 75. At this point, the oil tiow Fl is subjected to the resistance from the crests of the circumferential grooves 74. and thus a turbulent flow is generated in a connection region Al. The lubricating oil that has been turned into a turbu'ent flow in the connection region Al changes into a laminar flow of the lubricating oil while the lubricating oil flows toward a contact region A2, and thus heat in the half bearing 31 which is generated in the contact region A2 is less likely to be conducted to the lubricating oil. However, since heat in the surface of the half bearing 31 in the vicinity of the connection region Al is conducted to the lubricating oil that has been turned into a turbulent flow in the connection region Al, a temperature gradient is generated in the surface of the half bearing 31 between the connection region Al and the contact region A2. Consequently, inside the hail bearing 31, heat in the contact region A2 is conducted to the connection region Al in order to reduce the generated temperature gradient, and thus the contact region A2 of the half bearing 31 is cooled as a result.

On the other hand, in a state where the positions of the circumferential end surfaces of the pair of half bearings 31 and 32 are aligned as shown in Fig. 18, a sufficient space is generated between the inner circumferential surface (main cylindrical part 71) of the beanng and the surface of the shaft as shown in Fig. 19. Thus, while an oil flow F2 that flows in the circumferential direction following along the surface of the rotating shaft is intensified, the oil flow El is weakened since the surface of the crush rehef 70 is sufficiently distanced from the surface of the shaft. Accordingly, a turbulent flow is less likely to be formed in the connection region A, nor is a pressure loss of the lubricating oil generated, and thus a mechanical loss in the interna' combustion engine is not increased either.

(Effect) Subsequently, the effects of the half bearing 31 and the connecting rod bearing 3 of the present example will he described.

(1) The half bearing 31 of the present example is the half bearing 31 that constitutes the connecting rod bearing 3 serving as a plain bearing for supporting a crank shaft of an internal combustion engine. The half bearing 31 includes the main cylindrical part 71 that is formed at the center of the half bearing 31 in the circumferential direction and the crush reliefs 70, 70 that are formed at both circumferential ends of the hail bearing 31 such that the thickness of the wall is thinner than that of the main cylindrical part 71.

The main cylindrical part 71 is provided with the plurality of circumferential grooves 74 that continue in the circumferential direction, and the crush relief 70 is provided with the plurality of crush relief grooves 75 that continue in the circumferential direction. The groove width of the crush relief grooves 75 is the same as the groove width of the circumferential grooves 74 formed in the main cylindrical part 71. Then, the plurality of crush relief grooves 75, ... formed in the crush relief 70 are offset with respect to the plurality of circumferential grooves 74, ... formed in the main cylindrical part 71 in the widthwise direction of the half bearing 31 by an amount at least exceeding 0 and at most less than the groove width.

In this way, as the crush relief grooves 75 are shifted (offset) with respect to the circumferential grooves 74 in the widthwise direction of the half bearing, the lubricating oil is subjected to the resistance from the crests of the circumferential grooves 74, and thus a turbulent flow is formed in the connection region Al. Then, since heat in the surface of the half bearing 31 in the vicinity of the connection region Al is conducted to the lubricating oH that has been turned into a turbulent flow in the connection region Al, a temperature gradient is generated inside the half bearing 31 between the connection region Al and the contact region A2.

Consequently, inside the half bearing 31, heat in the contact region A2 is conducted to the connection region Al in order to reduce the generated temperature gradient, and thus the contact region A2 of the half bearing 31 is cooled as a result.

Accordingly, heat generated as the circumferential end of the main cylindrical part 71 of the half bearing 31 comes into contact with the mating shaft is conducted efficiently to the lubricating oil that has been turned into a turbulent flow, and thus the half bearing 31 can be prevented from reaching such a high temperature that causes damage thereto.

Then, the connecting rod bearing 3 serving as a plain bearing of the present example includes a pair of any of the above-described half bearings 31(32) and is formed by assembling the pair of half bearings 31 and 32 into a cylindrical shape.

EXAMPLE 2

Subsequently, with reference to Figs. II to 14, a case where, unlike Example I, the half bearing 31 further includes transition regions 73, 73 between the main cylindrical part 71 and the crush reliefs 70, 70 will be described. Note that a part that is the same as or equivalent to the content described in Example 1 will be descnbed with the same reference character.

As shown in Fig. 11, the half bearing 31(32) of the present example includes: the main cylindrical part 71 that is formed to include the center portion in the circumferential direction; the crush reliefs 70, 70 that are formed at both the circumferential ends; and the transition regions 73, 73 that are formed between the main cylindrical part 71 and the crush reliefs 70, 70 such that a thickness of a wall thereof is thinner toward the crush reliefs 70, 70.

In other words, in the transition region 73, a sloped curved surface is formed so as to approach a mating shaft from the inner surface of the crush relief 70 toward the inner surface of the main cylindrical part 71.

The transition region 73 as viewed in an axial direction of the half bearing 31 is formed of an inwardly convex curved surface that inwardly projects in the radial direction of the half bearing 31. That is, a slope of the sloped curved surface of the transition region 73 with respect to the imaginary inner circumferential plane of the half bearing 31 as viewed in the axial direction of the half beanng 31 is the maximum at a position connecting to the crush relief 70 and reaches the minimum at a position connecting to the main cylindrical part 71 to smoothly connect to the main cylindrical part 71. Here, the "inwardly convex curved surface" refers to a state where concavities and convexities of the circumferential grooves 74 are present in the widthwise direction and means that an outline (envelope surface) is curved in the circumferential direction.

Note that it is sufficient that the shape of the inner surface of the transition region 73 is in such a shape that an oil flow Fl that flows near the surface of the crush relief 70 is converted into an oil flow F3 that is oriented more toward the mating shaft, as described later.

According'y, the shape of the inner surface does not need to be the inwardly convex curved suiface, and may, for example, be planar (linear along a section) (see Fig. 15), or may be an outwardly convex curved surface (outwardly convex curve along a section) (see Fig. 16). More preferably, the shape of the inner surface can be an S-shaped curved surface in which a side closer to the crush relief 70 is an outwardly convex curved surface and a side farther therefrom is an inwardly convex curved surface (see Fig. 17).

Then, as shown in Figs. 11 to 13, the plurality of circumferential grooves 74, that are formed in the main cylindrical part 71 are formed to continue into the transition region 73 as well. The circumferential grooves 74 that are formed in the transition region 73 have the same groove width WG as the circumferential grooves 74 that are formed in the main cylindrica' part 71, and the groove width WO and the groove depth are constant along the circumferential direction. Thus, a pressure loss (form loss) of the lubricating oil that flows in the circumferential grooves 74 from the transition region 73 into the main cylindrical surface can be prevented. Note that although it is preferable that the groove depth in the transition region 73 is the same as the groove depth DG in the main cylindrica' part 71, the groove can be made deeper or can be made shallower.

Then, a plurality of crush relief grooves 75, ... that continue in the circumferential direction are formed in the crush relief 70 of the present example. The crush relief grooves 75 are formed in the inner sm-face of the crush relief 70 along the entire length in the circumferential direction. Furthermore, the crush relief grooves 75 are arranged in plurality to be parallel to one another in the widthwise direction of the half bearing 31 and are formed to span across the entire width, and thus a planar region does not exist therein.

To describe more specifically, the crush relief grooves 75 are formed into a circular arc shape (a shape where a circubr arc section is in the back) having a predetermined groove width and a predetermined groove depth, as in the circumferential groove 74 in the main cylindrical part 71 and the transition region 73. The groove width is the same as the groove width WO of the circumferential groove 74. The groove depth is preferably the same as the groove depth DG of the circumferential groove 74, but the groove depth does not need to be the same. The shape is preferably a circular arc shape or a U-shape, but may also be a V-shape.

Then, the plurality of crush relief grooves 75, ... of the present example are offset with respect to the plurality of circumferential grooves 74. ... that are formed in the main cylindrical part 71 and the transition region 73 by a half of the groove width WG in the widthwise direction and are arranged such that the troughs (concave shaped openings of the crush relief grooves) of the crush relief grooves 75 correspond to the crests (convexities formed between two adjacent circumferential grooves 74) of the circumferential grooves 74 in the connecting position of the crush relief 70 and the transition region 73 (see Fig. 8). Accordingly, the oil flow of the lubricating oil is subjected to the resistance at the connecting position of the crush relief 70 and the transition region 73.

Note that although an example where the plurality of crush relief grooves 75.

are offset with respect to the plurality of circumferential grooves 74, ... that are formed in the main cylindrical part 71 and the transition region 73 by a half of the groove width WG in the widthwise direction is shown in the present example, the present invention is not limited thereto.

The plurality of crush relief grooves 75 may be offset with respect to the plurality of circumferential grooves 74, ... that are formed in the main cylindrical part 71 and the transition region 73 by an amount in a range greater than 0 and less than the groove width WG in the widthwise direction. In other words, it is sufficient that the crush relief grooves 75 and the circumferential grooves 74 are alTanged such that the positions of the respective center portions in the groove widths are offset from each other by an amount in a range at least greater than 0 and at most less than the groove width WO in the widthwise direction of the half bearing 3 i at the connection position of the crush relief 70 and the main cylindrical part 71.

The crush relief 70 of the present example is formed such that a depth Dl at a position of the end surface 72 is greater than a depth D2 at a position connecting to the transition region 73, as shown in Figs. i2 and 13. Here, the depth of the crush relief 70 refers to a distance to the surface (a peak of a crest) of the crush relief 70 from the imaginary inner circumferential plane in which the inner circumferential surface of the main cylindrical part 71 is extended over the crush relief 70.

Further, the crush relief 70 of the present example is formed of an outwardly convex curved surface that outwardly projects in the radial direction of the half bearing 31.

That is, a slope of the inner surface of the crush relief 70 with respect to the imaginary inner circuitherential plane of the half beanng 31 as viewed in the axial direction of the half bearing 31 is the maximum at a position connecting to the transition region 73 and reaches the minimum at a position of the end surface 72 to become substantially parallel to the imaginary inner circumferential plane.

Next, with reference to Fig. 13, specific dimensions of the crush relief 70 and the transition region 73 will be described. Fig. 13 is a developed view in which the inner circumferential surface of the main cylindrical part 71 is developed to be pbnar (linear along the section). A length Ll and the depth Dl of the crush relief 70 may be the same as those of an existing crush relief. For example. although it may vary depending on the specifications of an intema combustion engine, in a case of a bearing for a small-sized intemal combustion engine for an automobile, the length Ll is approximately 3 mm to 7 mm, and the depth Dl is approximately 0.01 mm to 0.05 mm.

The depth D2 of the crush rd ief 70 at a position connecting to the transition region 73 can be set to 0.005mm to 0.030 mm. If the depth D2 is within this range, an amount of oil that reaches this connecting position Al is increased, and thus the oil flow F3 (see Fig. 14) can be formed. That is, in a case where the depth D2 is less than 0.005 nim, an amount of oil that reaches the connecting position is decreased, and thus it is hard to form the oil flow P3. On the other hand, in a case where the depth D2 exceeds 0.030 mm, a space in the crush relief 70 at a widthwise end of the half bearing 31 (a space sandwiched between the inner surface of the crush relief 70 and the imaginary inner circumferential plane) is increased, and thus an amount of the lubricating oil that leaks out through both ends of the half bearings 31 in the widthwise direction of the half beanng 31 is increased.

The length L2 of the transition region 73 in the circumferential direction can be set to 1 mm to 4 mm. If the length L2 is within this range. the oil flow P3 of a predetermined flow rate is formed and coflides with an oil flow F2, which results in the formation of a turbulent flow That is, in a case where the length Ll is 0 or less than 1 mm, a step constituted by a perpendicular plane is generated between the main cylindrical surface of the main cylindrical part 71 and the inner surface of the crush relief 70. Thus, a resistance to the oil flow Fl is increased excessively, so that the lubricating oil leaks out and thus the oil flow F3 is less likely to be formed. On the other hand, in a case where the length LI exceeds 4 mm, a flow direction of the oil flow F3 approaches a flow direction of the oil flow F2, and thus even when the oil flow F3 and the oil flow P2 collide with each other, a turbulent flow is less likely to be formed.

Note that the shapes of the main cylindrical part 71, the crush relief 70, and the transition region 73 described above can be measured with a typical shape measuring instrument such as a roundness measuring instrument. That is, in a state where a bearing is assembled to a connecting rod, an engine block, or a housing similar to these, the shape of the inner surface of the bearing can be measured continuously in the circumferential direction.

(Operation) Subsequently, an operation of the half bearing 31 of the present example will be described with reference to Figs. 9, 14 to 17, A case is considered in which the vicinity of the circumferential end of the inner circumferential surface (the main cylindrical part 71) of the half bearing 31 (32) comes into direct contact with the surface of the mating shaft in a state where the circumferential end surfaces of the pair of half bearings 31 and 32 are misaligned as shown in Fig. 9. In this state, the main cylindrical surface of the main cylindncal part 71 and the surface of the crush relief 70 are in close proximity to the surface of the mating shaft at the vicinity of one end of the half bearing 31 which is misaligned inwardly (an upper right portion and a lower left portion in Fig. 9).

When the surface of the crush relief 70 and the surface of the mating shaft are in close proximity to each other, the oil flow Fl that flows near the surface of the crush relief 70 is first formed and guided in the crush relief grooves 75, as shown in Fig. 14. Then, the oil flow Fl is guided into the circumferential grooves 74 formed in the transition region 73, and thus the oil flow F3 that flows toward the main cylindrical part 71 is formed. At this point, the oil flow Fl is subjected to the resistance from the crests.' of the circumferential grooves 74, and thus a turbulent flow is generated in the connection region Al. Subsequently, the oil flow F3 collides in a collision region A3 with the oil flow F2 that flows in the circumferential direction following along the surface of the shaft, and thus the oil flows F2 and F3 are mutually disturbed to form a turbulent flow.

The lubricating oil that has been turned into a turbulent flow changes into a laminar flow of the lubricating oil while the lubricating oil flows from the connection region Al and the collision region A3 to the contact region A2, and thus heat in the half bearing 31 which is generated in the contact region A2 is less likely to be conducted to the lubricating oil.

However, since heat in the surface of the half bearing 31 in the vicinity of the connection region Al and the collision region A3 is conducted to the lubricating oil that has been turned into a turbulent flow generated in the connection region Al and the collision region A3, a temperature gradient is generated inside (near the surface of) the half bearing 31 between the connection region Al or the collision region A3 and the contact region A2. Consequently, inside the half bearing 31, heat in the contact region A2 is conducted to the connection region Al and the collision region A3 in order to reduce the generated temperature gradient, and thus the contact region A2 of the half bearing 31 is cooled as a result.

In particular, as the depth Dl at a position of the end surface of the crush relief 70 is greater than the depth D2 at a position connecting to the transition region 73, the oil flow P3 is further intensified. That is, a space between the crush rehef 70 and the surface of the mating shaft becomes gradually narrower toward the transition region 73 from the end surface 72.

According'y, the flow rate of the oil flow El that flows near the surface of the crush relief 70 increases toward the transition region 73, and thus the oil flow F3 is more likely to be formed.

On the other hand, in a state where the positions of the circumferential end surfaces of the pair of half bearings 31 and 32 are aligned as shown in Fig. 18, a sufficient space is generated between the inner circumferential surface (the main cylindrical part 71) of the bearing and the surface of the shaft, and thus while the oil flow P2 is intensified, the oil flow Fl and the oil flow F3 are weakened since the surface of the crush rehef 70 is sufficiently distanced from the surface of the shaft (see Fig. 19). Accordingly, a turbulent flow is not formed, nor is a pressure loss of the lubricating oil generated, and thus a mechanical loss in the internal combustion engine is not increased either.

Further, since the transition region 73 of the present example includes an inwardly convex curved surface, a space is generated between the collision region A3 in which the oil flow F2 and the oil flow F3 collide with each other and the contact region A2. Thus, a volume of the luhncating oil to be turned into a turbulent flow increases, and conduction of heat from the half bearing 31 is facilitated. For example, as shown in Figs. 15 and 16, in acase where the transition region 73 is formed of a planar sloped surface or an outwardly convex curved surface, a space for temporanly storing the lubricating oil that has been turned into a turbulent flow is small, and thus conduction of heat may not be facilitated.

Subsequently, with reference Fig. 17, a case where the transition region 73 includes an outwardly convex curved surface 73a at a side closer to the crush relief 70 and an inwardly convex curved surface 73b at a side farther therefrom to generally form an S-shaped curved surface will be described as another mode of the transition region 73. In a case where the transition region 73 is formed of an S-shaped curved surface as such, conduction of heat is further facilitated. To be more specific, since a space is generated between the collision region A3 and the contact region A2 by the inwardly convex curved surface 73b at the side farther from the crush relief 70 similarly to the above description, a volume of the lubricating oil to be turned into a turbulent flow increases. Further, since an intersecting angle of the oil flow F3 with respect to the oil flow P2 is increased by the outwardly convex curved surface 73a at the side closer to the crush relief 70, generation of a turbulent flow is facilitated.

(Effect) Subsequently, the effects of the half bearing 31 and the connecting rod bearing 3 of the present example will be listed and described.

(1) The half bearing 31 of the present example is the half bearing 31 that constitutes the connecting rod bearing 3 serving as a plain bearing for supporting a crank shaft of an internal combustion engine. The half bearing 31 indudes the main cylindrical part 71 that is formed at the center of the half bearing 31 in the circumferential direction and the crush reliefs 70, 70 that are formed at both circumferential ends of the half bearing 3 i such that the thickness of the wall is thinner than that of the main cylindrical part 7 i. Then, the half bearing 31 of the present example further includes the transition regions 73 that are formed adjacent to the both circumferential ends of the main cylindrical part 71 such that the thickness of the wall is gradually thinner toward the crush relief 70. The crush relief 70 is formed such that the depth Dl at a position of the circumferential end surface 72 of the half bearing 31 is greater than the depth D2 at a position connecting to the transition region 73. Further, the plurality of circumferential grooves 74, ... that continue in the circumferential direction are formed in the main cylindrical part 71, and the plurality of circumferential grooves 74, ... are formed to continue into the transition region 73 as well.

Through such a configuration, in a state where the positions of the end surfaces 72 of the half bearings 31 are offset with respect to each other, the oil flow Fl that flows near the surface of the crush relief 70 is guided in the crush relief grooves 75 while being intensified.

Then, the oil flow Fl enters the circumferential grooves 74 from the crush relief grooves 75. At this point, the oil flow Fl is subjected to the resistance from the crests of the circumferential grooves 74, and thus a turbulent flow is generated in the connection region Al. Subsequently, the oil flow P3 is guided in the circumferential grooves 74 in the transition region 73. Then, the oil flow F3 collides in the collision region A3 with the oil flow F2 that flows in the circumferential direction following along the surface of the shaft, and thus the oil flows F2 and F3 are mutually disturbed to form a turbulent flow. Formation of a turbulent flow is facilitated at two positions of the connection region Al and the collision region A3, and thus an amount of conducted heat can be further increased. Accordingly, heat generated as the circumferential end of the main cylindrical part 71 of the half bearing 31 comes into contact with the mating shaft is conducted more efficiently to the lubricating oil that has been turned into a turbulent flow, and thus the half bearing 31 can be prevented from reaching such a high temperature that causes damage thereto.

(2) Further, the transition region 73 can be formed of an inwardly convex curved surface that inwardly projects in the radial direction of the half bearing 31. Thus, a space is generated between the collision region Al in which the oil flow P2 and the oil flow P3 collide with each other and the contact region A2. Accordingly, a volume of the lubricating oil to be turned into a turbulent flow increases, and conduction of heat from the half bearing 31 is facilitated.

(3) Furthermore, the transition region 73 can also be formed of the outwardly convex curved surface 73a that outwardly projects in the radial direction at the side closer to the crush relief 70 and the inwardly convex curved surface 73b that inwardly projects in the radial direction at the side farther from the crush relief 70. In a case where the transition region 73 includes an S-shaped curved surface as such, conduction of heat is further facilitated. That is, by including the inwardly convex curved surface 73b, a volume of the lubricating oil to be turned into a turbulent flow increases, and by including the outwardly convex curved surface 73a, generation of the turbu'ent flow is facilitated.

(4) Then, the crush relief 70 may preferably be such that the depth D2 thereof at a position connecting to the transition region 73 is 0.005 mm to 0.030 mm. If the depth D2 is within this range, an amount of oH that reaches this connecting position is increased, and thus the oil flow F3 can be formed.

(5) Further, the ength L2 of the transition region 73 in the circumferential direction is preferably 1 mm to 4 mm. If the length L2 is within this range, the oil flow F3 of a predetermined flow rate is formed to collide with the oil flow P2, and thus a turbulent flow is generated.

(6) Then, the connecting rod bearing 3 serving as a plain bearing of the present example includes a pair of any of the above-described half bearings 31 and is formed by assembling the pair of half bearings 31 and 32 into a cylindrical shape.

Note that the configurations and effects aside from the above are substantially the same as those of Examples, and thus the description thereof will be omitted.

EXAMPLE 3

Subsequently, a test conducted to confirm the effects of the half bearing 31 of Examples I to 2 will be described with reference to tables in Figs. 20 and 21.

(Test Conditions) First, test conditions will be described. A test was carried out on embodied products and an existing product shown in Fig. 20. Here, an embodied product No. I and an embodied product No. 2 correspond to Example 1, in which the crush relief grooves that were shifted in phase with respect to the circumferential grooves were formed in the crush relief. An embodied product No. 3 colTesponds to Example 2 shown in Figs. 11 to i4, in which the transition region was formed of an inwardly convex curved surface. An embodied product No. 4 colTesponds to another mode of Example 2 shown in Fig. 17, in which the transition region was formed of an S-shaped continuing curved surface that included an outwardly convex curved surface and an inwardly convex curved surface, An embodied product No. 5 corresponds to another mode of Examp'e 2 shown in Fig. 16, in which the transition region was formed of an outwardly convex curved surface.

For the embodied products No. 1 to No. 5. the crush relief grooves that were shifted (offset) in phase with respect to the circumferential grooves in the widthwise direction of the half bearing were formed in the crush relief, and the amount of offset (shift value) of each embodied product is shown as the ratio of the shift value to the groove width of the circumferential groove, in the "OFFSET RATIO (%)" section of Fig. 20. The offset ratio here refers to a value that is obtained by dividing the amount of offset by the groove width and expressing the calculation result in percentage. For example, if the offset ratio is 50%, the bottom part of the crush relief groove corresponds to the top part of the circumferential groove.

The existing product had an existing crush relief, and crush relief grooves formed therein were aligned with respect to the circumferential grooves formed in the main cylindrical surface of the half bearing, in the widthwise direction of the haff bearing. Further, the transition region was not formed in the existing product.

For each of the embodied products No. I to No. 5 and the existing product, a half bearing having an outer diameter of 53 mm, an inner diameter of 50 mm, and a width of 15 mm was used, and the test was calTied out on a plain bearing in which a pair of half bearings was assembled into a cylindrical shape. Each of the crush reliefs of the embodied products No. i to No. S and the existing product was 5 mm in length from the circumferential end surface of the half bearing and 0.04 mm in depth at the circumferential end surface of the half bearing. A plurality of circumferential grooves were formed in the inner circumferential surface of the embodied products at the main cylindrical part and the transition region. The groove depth of the circumferential groove was 3 tm, and the groove width thereof was 0.1 mm, which were constant across the circumferential direction of the bearing. Further. (the plurality of) circumferential grooves were formed to span across the entire width of the bearing in the widthwise direction. A plurality of crush relief grooves were formed in the crush reliefs of the embodied products. The groove depth of the crush relief groove was 3 m, and the groove width thereof was 0.1 mm. A plurality of circumferential grooves were formed in the main cylindrical part of the existing product. The groove depth of the circumferential groove was 3 jim, and the groove width thereof was 0.1 nrni, which were constant across the circumferential direction of the bearing. Further, the plurality of circumferential grooves were formed to span across the entire width of the healing in the widthwise direction. The plurality of crush relief grooves were formed in the crush relief of the existing product. The groove depth of the crush relief grooves was 3 m, and the groove width thereof was 0.1 mm. Note that other specifications of the embodied products and the existing product were as shown in Fig. 20.

A beanng test was canied out on the embodied products No. ito No. 5 and the existing product under the conditions shown in Fig. 21. On each of the embodied products and the existing product, a hearing test was caned out in which two half bearings were paired and embedded into a bearing holding portion (not shown) of a divided type bearing housing such that the vicinity of a circumferential end of an inner circumferential surface (main cylindrical part) of the half bearing came into contact with a shaft in a state where the positions of the respective circumferential end surfaces of the pair of half bearings were misaligned (see Fig. 9).

Immediately after the bearing test was completed, a temperature of the half bearing in each embodied products was measured at the rear surface (a position of S in Fig. 9) of a circumferential end portion of the inner circumferential surface (main cylindrical part) of the half bearing which was in contact with the shaft. Measured bearing temperatures are shown in Fig.

I

(Results) Subsequently, test results will be briefly described. As shown in Fig. 20, while the existing product showed 155°C, the embodied products No. I to No. 5 showed 137°C, 142°C, 115°C, 123°C, and 135°C, respectively. ffi this way, it is found that, in any of the embodied products, because the crush relief grooves in the crush relief were shifted in phase with respect to the circumferential grooves in the inner circumferential surface (main cylindrical part) of the half bearing in the widthwise direction of the half beanng, a turbulent flow was generated and a rise in temperature of the half bearing due to coming into contact with the shaft was suppressed as compared to the existing product. In particular, it is shown that effects were greater in the embodied products No. 3 and No, 4. Further, in view of the fact that even the embodied product No. 2 produced an effect, it is found that an effect of suppressing a nse in temperature can be obtained if the offset ratio is at least 3% (the same applies to 97%). Note that individual considerations on the respective embodied products are omitted since they coincide with the description of the operations and effects described in Examples 1 to S above.

On the contrary, in the existing product, as shown in Fig. 22, crush relief grooves in a crush relief surface 170 are aligned with respect to circumferential grooves 174 in an inner circumferential surface (main cylindrical part) 171 of the half bearing, in the widthwise direction of the half bearing. Therefore, as shown in Fig. 23, the oil flow El that flows through the crush relief grooves 175 near the surface of the crush relief 170 is formed as an oil flow of the lubricating oH from the crush relief 170 toward the inner circumferential surface (main cylindrical part) 171 of the half bearing. At the end of the crush relief 170, the oil flow Fl is not disturbed when flowing into the circumferential grooves in the inner circumferential surface (main cylindncal part) 171 of the half bearing, and the lubricating oil flows toward the inner circumferential surface (main cylindrical part) 171 of the half bearing as a laminar flow. Since heat in the half bearing is tess likely to be conducted to the laminar flow of the lubricating oil, a rise in temperature of the half bearing due to coming into contact with the shaft was greatest in the existing product.

Thus far, examples of the present invention have been described in detail with reference to the drawings. However, specific configurations are not limited to these examples, and modifications in design to such a degree that does not depart from the scope of the present invention are encompassed by the present invention.

For example, the half bearing 31, 32 of the present invention may be applied to only any one of the paired half bearings 31 and 32 that constitute the plain bearing, and may be applied to both the paired half bearings 31 and 32.

Claims

CLAIMS: I. A half bearing for supporting a crank shaft of an intemal combustion engine, the half bearing comprising: a main cylindrical part including a center portion in a circumferential direction of the half bearing, the main cylindrical part being provided with a plurality of circumferential grooves extending in the circumferential direction of the half bearing; and two crush reliefs, each crush relief having a thickness arranged at each circumferential end of the half bearing, the thickness of the crush relief being thinner than that of the main cylindrical part, each crush relief having a plurality of crush relief grooves extending in the circumferential direction of the half bearing, wherein each groove width of the crush relief grooves is the same as each groove width of the circumferential grooves, and the plurality of crush relief grooves are offset with respect to the plurality of circumferential grooves in a widthwise direction of the hail bearing by an amount at least exceeding 0 and at most less than the groove width.
2. The half bearing according to claim I, further comprising two transition regions, each transition region having a thickness being positioned between the main cylindrical part and the crush relief, the thickness of the transition region is thinner toward the crush relief, wherein, when an imaginary inner circumferential plane is assumed to extend over the crush relief, the imaginary plane being coplanar with the inner circumferential surface of the main semi-cylindrical part, each crush relief has a depth from the imaginary plane at a circumferential end surface of the half bearing greater than a depth from the imaginary plane at a connecting position between each crush relief and each transition region, and the circumferential grooves in the main cylindrical part extend also in the transition region continuously.
3. The half bearing according to claim 2, wherein the transition region includes an inwardly convex curved surface projecting inwardly in a radial direction of the half bearing.
4. The half bearing according to claim 2 or 3, wherein the transition region includes an outwardly concave curved surface caving outwardly in the radial direction at a side closer to the crush relief and an inwardly convex curved surface projecting inwardly in the radial direction at a side farther from the crush relief.
5. The half bearing according to any one of claims 2 to 4, wherein a depth of the crush relief at a position connecting to the transition region is 0.005 mm to 0.030 mm.
6. The half bearing according to any one of claims 2 to 5, wherein a length of the transition region in the circumferential direction is 1 mm to 4 mm.
7. A plain bearing, comprising: a pair of the half bearings according to any one of claims I to 6. wherein the pair of half bearings are assembled into a cylindrical shape.