Step Selective Area Cylinder Roughening (PTWA)

Abstract

An engine block includes at least one cylinder bore. The at least one cylinder bore includes a first cylindrical portion, a second cylindrical portion, and a transition portion. The first cylindrical portion has a diameter greater than the second cylindrical portion. The transition portion extends from the first cylindrical portion to the second cylindrical portion. Each of the first cylindrical portion, the second cylindrical portion, and the transition portion defines a rough surface.

Description

Technical Field

[0001] The present disclosure relates to a cylinder bore of an engine block, and more particularly to a cylindrical surface of a cylinder bore of an engine block. Background Art

[0002] The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

[0003] An automotive engine block includes a number of cylinder bores. The inner surface of each cylinder bore is machined so that the surface is suitable for automotive applications, for example, exhibiting suitable wear resistance and strength. The machining process may include roughening the inner surface, then applying a metal coating to the rough surface, and then honing the metal coating to obtain a finished inner surface.

[0004] Various surface roughening techniques are known in the art, but have one or more drawbacks or disadvantages. For example, the metal coating may not be applied uniformly to the roughened surface, resulting in cracks during subsequent honing.

[0005] The present disclosure addresses these problems associated with rough cylinder surfaces, as well as other problems associated with machining and finishing cylinder surfaces. Summary of the invention

[0006] In one form, an engine block having at least one cylinder bore is provided, the engine block comprising a first cylindrical portion, a second cylindrical portion, and a transition portion. The first cylindrical portion has a diameter greater than the second cylindrical portion. The transition portion extends from the first cylindrical portion to the second cylindrical portion. Each of the first cylindrical portion, the second cylindrical portion, and the transition portion defines a rough surface.

[0007] In another form, the transition portion may define a tapered configuration and may include a plurality of peaks defining a variable inner diameter and at least one annular groove.The annular groove may define an undercut.

[0008] In yet another form, the transition portion may define at least one step relative to the first cylindrical portion and the second cylindrical portion. In yet another form, the transition portion may define a first step relative to the first cylindrical portion and a second step relative to the second cylindrical portion. The first cylindrical portion is recessed from the first step by a first depth, and the second step is recessed from the second cylindrical portion by a second depth. The second depth is greater than the first depth. The first step and the second step may have different widths along the axial direction of the cylinder bore.

[0009] In yet another form, the first cylindrical portion and the second cylindrical portion each define a plurality of annular grooves. The annular grooves of the first cylindrical portion each define an undercut. The plurality of grooves of the second cylindrical portion each define a rectangular cross-section. The second cylindrical portion includes two discontinuous axial portions. The first cylindrical portion extends between the two discontinuous axial portions.

[0010] In yet another form, the engine bore further includes a flared end portion. The second cylindrical portion is disposed between the flared end portion and the transition portion. The flared end portion has an inner diameter greater than an inner diameter of the second cylindrical portion. The cylinder bore defines a travel region in which a piston travels and a non-travel region outside the travel range of the piston. The first cylindrical portion is disposed in the travel region, and the second cylindrical portion and the transition portion are disposed in the non-travel region.

[0011] Further applicability will become apparent from the description provided herein.It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The present disclosure will be more fully understood from the detailed description and accompanying drawings, in which:

[0013] Figure 1 is a top view of an exemplary engine block of an internal combustion engine;

[0014] Figure 2 It is along Figure 1 An individual cross-sectional view of the cylinder bore taken along line 2-2;

[0015] Figure 3 depicts a pre-drilling step in which the unmachined inner surface of a cylinder bore is bored to a certain diameter;

[0016] Figure 4 An interpolating step is shown wherein an unmachined cylinder bore inner surface is machined to form a first cylindrical portion having a rough surface including a recess and a plurality of annular grooves;

[0017] Figure 5 depicts a deforming step wherein flat peaks between adjacent annular grooves in the first cylindrical portion are deformed to obtain deformed peaks;

[0018] Figure 6 depicts a second interpolation step wherein the second cylindrical portion and the transition portion are machined to form a roughened surface having a plurality of annular grooves;

[0019] Figure 7 Depicted Figure 6 an enlarged view of part C;

[0020] Figure 8 Depicted Figure 6 an enlarged view of a portion D of;

[0021] Fig. 9 Depicted Figure 6 an enlarged view of part E;

[0022] Fig.10 Describes the second form of the present disclosure Figure 6 an enlarged view of part F;

[0023] Fig.11 is a cross-sectional view of a cylinder bore constructed in accordance with a third form of the present disclosure; and

[0024] Fig.12 yes Fig.11 An enlarged view of portion G.

[0025] Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. DETAILED DESCRIPTION

[0026] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.

[0027] An automotive engine block includes a plurality of cylinder bores, each having an inner surface that exhibits suitable wear resistance and strength for automotive applications. The machining process may include roughening the pre-drilled inner surface to form a rough surface, then applying a metal coating to the rough surface, then honing the metal coating to obtain a finished inner surface having desired strength and wear resistance. Alternatively, a lining material having desired strength and wear resistance properties may be applied to the unfinished inner surface of the engine bore.

[0028] Various forms disclosed herein provide a profile of the roughened surface of the cylinder bore to enhance the adhesion and bonding of subsequently applied metal coatings (e.g., thermal spray coatings). As a result, the finished inner surface can have enhanced strength and wear resistance. In addition, the present disclosure enhances the cylinder bore surface profile and process disclosed in U.S. Pat. No. 9,382,868, which is incorporated herein by reference in its entirety.

[0029] refer to Figure 1 and Figure 2, an exemplary engine block 10 of an internal combustion engine includes a plurality of cylinder bores 12, each having an inner surface 14 extending between opposite ends 16. The inner surface 14 may be formed of a metal such as, but not limited to, aluminum, magnesium, or iron, or alloys thereof, or steel. Aluminum or magnesium alloys may be utilized due to their light weight compared to steel or iron in order to reduce engine size and weight, thereby improving engine power output and fuel economy. A metal coating (not shown) is applied to the inner surface 14 of each cylinder bore 12 to improve the strength and wear resistance of the cylinder bore 12. The inner surface 14 includes a rough surface that is roughened and finished to enhance the adhesion and bonding of the metal coating applied thereon.

[0030] Each cylinder bore 12 includes a first cylindrical portion 20 in the middle of the cylinder bore 12, a second cylindrical portion 22 at the opposite end 16 of the cylinder bore 12, and a transition portion 24 between the first cylindrical portion 20 and the second cylindrical portion 22. The second cylindrical portion 22 includes two discontinuous axial portions at the opposite end 16 of the cylinder bore 12. The first cylindrical portion 20 extends between the two discontinuous axial portions 22. The transition portion 24 also includes two discontinuous axial portions extending from the first cylindrical portion 20 to corresponding discontinuous axial portions of the second cylindrical portion 22. Each of the first portion 20, the second portion 22, and the transition portion 24 includes a rough surface.

[0031] Figure 3 A pre-drilling step is depicted wherein an unmachined cylinder bore is formed in the engine block 10. The unmachined cylinder bore includes a pre-drilled surface 26 having an inner diameter that is smaller than the inner diameter of the inner surface 14.

[0032] refer to Figure 4 , the surface 26 of the unmachined cylinder bore is machined to form the first cylindrical portion 20, the second cylindrical portion 22, and the transition portion 24, each of which has a rough surface. Figure 4 A first interpolation step is depicted in which the pre-drilled inner surface 26 is machined using a cutting tool to form a first cylindrical portion 20 having a roughened surface defined by a pocket 28 and a plurality of annular grooves 30. The pocket 28 is recessed from the second cylindrical portion 22 and the transition portion 24.

[0033] The cylinder bore 12 defines a travel region in which the piston travels in the cylinder bore 12 and a non-travel region outside the axial travel distance of the piston. The first cylindrical portion 20 is disposed in the travel region, while the second cylindrical portion 22 and the transition portion 24 are disposed in the non-travel region. The length of the first cylindrical portion 20 corresponds to the distance traveled by the piston in the cylinder bore 12. The two discontinuous axial portions of the second portion 22 and the transition portion 24 at the opposite ends 16 of the cylinder bore 12 may have the same or different lengths.

[0034] exist Figure 4 In the embodiment of the present invention, for the sake of clarity, the annular groove 30 is only shown in the enlarged portion A. It should be understood that the annular groove 30 can be formed along the entire length of the recess 28. Flat peaks are formed between adjacent grooves 30.

[0035] refer to Figure 5 In the deformation step, the flat peaks between adjacent grooves 30 are deformed by sliding the tool to obtain deformed peaks 32. Each peak 32 includes a pair of undercuts 34, such as Figure 5 The number of deformation peaks 32 shown in enlarged portion B is merely exemplary, and deformation peaks 30 may be formed along the entire length of the pocket 28 and thus along the entire length of the travel area.

[0036] refer to Figure 6 and Figure 7 In the second interpolation step, the pre-drilled surface 26 is further machined using a cutting tool to form a second cylindrical portion 22 at the opposite end 16. The second cylindrical portion 22 has a rough surface defined by a plurality of annular grooves 36. Figure 7 The annular grooves 36 are clearly shown in the enlarged portion C of the embodiment. Flat peaks 38 extend between the annular grooves 32. It will be appreciated that the number of annular grooves 36 shown in the enlarged portion C is merely exemplary. The annular grooves 36 may define a uniformly sized square wave shape or any other shape. The flat peaks 38 of the second cylindrical portion 22 may or may not be deformed like those in the first cylindrical portion 20.

[0037] refer to Figure 8 , the pre-drilled surface 26 may be further machined to form a transition portion 24 between the first cylindrical portion 20 and the second cylindrical portion 22. The transition portion 24 may be formed by machining the area of ​​the pre-drilled surface 26 between the first cylindrical portion 20 and the second cylindrical portion 22 into a plurality of steps (such as a first step 41 and a second step 43), and then by forming one or more annular grooves 42 in each step 41, 43, thereby defining a rough surface in the transition portion 24.

[0038] The transition portion 24 is provided to avoid the acute angle between the first cylindrical portion 20 and the second cylindrical portion 22. The inner diameter of the transition portion 24 is larger than the inner diameter of the second cylindrical portion 22 and smaller than the inner diameter of the first cylindrical portion 20. The first cylindrical portion 20 may be recessed from the first step 41 by a depth d1, and the second step 43 of the transition portion 24 may be recessed from the second cylindrical portion 22 by a depth d2, wherein d1 is larger than d2. In other words, the transition portion 24 is recessed deeper from the second cylindrical portion 22 than the first cylindrical portion 20 is recessed from the transition portion 24.

[0039] The transition portion 24 includes a plurality of annular grooves 42 and peaks 44 between adjacent annular grooves 42. The peaks 44 are deformed to form undercuts 46. The peaks 38 between the annular grooves 36 in the second cylindrical portion 22 may or may not be deformed to form undercuts. The transition portion 24 defines a generally conical configuration, and the plurality of peaks 44 are gradually recessed from adjacent peaks 44. Thus, the plurality of peaks 44 between the grooves 42 have a variable inner diameter.

[0040] refer to Fig. 9 After the pre-drilled surface 26 is machined to form the first portion 20 , the second portion 22 , and the transition portion 24 having rough surfaces, the thermal spray coating 50 is applied to the rough surfaces of the first portion 20 , the second portion 22 , and the transition portion 24 .

[0041] The second cylindrical portion 22 is arranged in the non-travel area. It is not necessary to form a rough surface in the second cylindrical portion 22 and apply a metal coating 50 thereon. However, during the entire spraying process, a torch for metal spraying is usually retained. If the pre-drilled surface in the non-travel area (i.e., the second cylindrical portion 22 and the transition portion 24) is not roughened, the spray metal may be accidentally sprayed on these parts and may not adhere, thereby causing delamination. This delamination may fall into the cylinder bore during honing and be sandwiched between the honing stone and the hole wall, resulting in unacceptable scratches. The delamination may also fall into the crankcase, which then needs to be removed. Therefore, the second cylindrical portion 22 and the transition portion 24 are also roughened by forming annular grooves to promote the adhesion of the thermal spray metal layer and alleviate the contamination of the expected spraying surface and the crankcase. During the subsequent honing operation, the lightly sprayed non-annular travel area can be easily removed.

[0042] refer to Fig.10 , partially showing the inner surface of the cylinder bore constructed according to the second form of the present disclosure, and the structure of the inner surface is similar to Figures 4 to 9 Therefore, like elements are indicated by like reference numerals, and detailed description is omitted herein for clarity.

[0043] More specifically, the cylinder bore 50 includes a first cylindrical portion 20 in the middle of the cylinder bore 50, a second cylindrical portion 22 disposed at a longitudinal end of the cylinder bore 50, and a transition portion 52 extending from the first cylindrical portion 20 to the second cylindrical portion 22. The transition portion 52 includes a first step 54 adjacent to the first cylindrical portion 20, a second step 56, and a tapered surface 58 adjacent to the second cylindrical portion 20. The second step 56 is disposed between the first step 56 and the tapered surface 58. The first step 54 and the second step 56 each define one or more annular grooves 60 and flat peaks 62 between adjacent grooves 60. The flat peaks 62 are deformed to form undercuts 64.

[0044] The first cylindrical portion 20 is recessed from the first step 54 by a first depth d1. The second step 56 is recessed from the second cylindrical portion 22 by a second depth d2. The second depth d2 is greater than the first depth d1. In other words, the second step 56 is recessed from the second cylindrical portion 22 more deeply than the first cylindrical portion 20 is recessed from the first step 54. No annular groove is formed in the tapered surface 54 provided between the second cylindrical portion 22 and the second step 56. Although the transition portion 52 is Fig.10 5. As shown in FIG. 5 as including two steps, it should be understood that any number of steps, including one step, may be formed in the transition portion 52 without departing from the scope of the present disclosure.

[0045] refer to Fig.11 , partially showing a cylinder bore 70 constructed according to a third form and having an inner surface 72 similar in structure to that of the cylinder bore 70 except for the transition portion, the second cylindrical portion and the provision of a flared end. Figures 4 to 9 The inner surface shown in .

[0046] refer to Fig.12 , the cylinder bore 70 includes a first cylindrical portion 20, a second cylindrical portion 74, a transition portion 76, and a flared end portion 78. The first cylindrical portion 20 is recessed from the transition portion 76, so the inner diameter of the first cylindrical portion 20 is greater than the inner diameter of the transition portion 76. The first cylindrical portion 20 includes a plurality of annular grooves 80. It should be understood that although Fig.12Only a few grooves 80 are shown in the first cylindrical portion 20, but the grooves 80 are arranged along the entire length of the first cylindrical portion 20. The flat peaks between adjacent grooves 80 may or may not be deformed to form undercuts. The second cylindrical portion 74 protrudes from the transition portion 76, so the inner diameter of the second cylindrical portion is smaller than the inner diameter of the transition portion 76. The second cylindrical portion 74 does not include any grooves. The second cylindrical portion 74 is arranged between the flared end portion 78 and the transition portion 76. The flared end portion 78 defines a tapered surface and has an inner diameter larger than the inner diameter of the second cylindrical portion 74.

[0047] The cylinder bore of the present application constructed according to the teachings of the present disclosure provides a transition portion between the first cylindrical portion (in the travel area of ​​the cylinder bore) and the second cylindrical portion (in the non-travel area of ​​the cylinder bore) to avoid the acute angle between the travel area and the non-travel area of ​​the cylinder bore. The transition portion 24, 52, 74 may include one or more steps and one or more annular grooves in each of the steps. Alternatively, the transition portion may have a generally conical configuration, and the peaks between adjacent grooves are gradually recessed from adjacent peaks, thereby providing a smooth transition from the first cylindrical portion having a larger inner diameter to the second cylindrical portion 22, 74 having a smaller inner diameter. Such a transition portion 24, 52, 74 can reduce the number and size of voids generated in the region due to spray metal particles rebounding between the angled surfaces between the first cylindrical portion 20 and the second cylindrical portion 22. These voids may expose the inner surface of the cylinder bore 12 during honing, thereby causing delamination of the metal coating. Any number of steps or continuously variable surfaces may be provided in the transition portion to reduce voids created in the metal coating that is subsequently applied to the inner surface of the cylinder bore 12 .

[0048] It should be noted that the present disclosure is not limited to the forms described and illustrated. Various modifications have been described, and more are part of what is known to those skilled in the art. These and other modifications and any substitutes made by technical equivalents may be added to the specification and the accompanying drawings without departing from the scope of protection of the present disclosure and this patent.

Claims

1. An engine block having at least one cylinder bore, comprising: The first cylindrical portion, a second cylindrical portion having a smaller diameter than the first cylindrical portion; as well as a transition portion extending from the first cylindrical portion to the second cylindrical portion, wherein each of the first cylindrical portion, the second cylindrical portion, and the transition portion defines a rough surface; wherein the transition portion defines at least one step relative to the first cylindrical portion and the second cylindrical portion; The transition portion defines a first step relative to the first cylindrical portion and a second step relative to the second cylindrical portion, the first cylindrical portion is recessed by a first depth from the first step, the second step is recessed by a second depth from the second cylindrical portion, and the second depth is greater than the first depth.

2. The engine block of claim 1, wherein the transition portion defines a tapered configuration.

3. The engine block of claim 2, wherein the transition portion, wherein a plurality of peaks of the transition portion define a variable inner diameter. 4 . The engine block of claim 1 , wherein the first step portion and the second step portion have different widths along an axial direction of the cylinder bore.

5. The engine block of claim 1, wherein the transition portion defines at least one annular groove.

6. The engine block of claim 5, wherein the at least one annular groove defines an undercut.

7. The engine block of claim 6, wherein the transition portion includes a plurality of flat peaks adjacent the at least one groove.

8. The engine block of claim 1, wherein the first cylindrical portion and the second cylindrical portion each define a plurality of annular grooves.

9. The engine block of claim 8, wherein the plurality of annular grooves of the first cylindrical portion each define an undercut.

10. The engine block of claim 8, wherein the plurality of grooves of the second cylindrical portion each define a rectangular cross-section.

11. The engine block of claim 1 wherein said second cylindrical portion comprises two discontinuous axial portions and said first cylindrical portion extends therebetween.

12. The engine block of claim 1, wherein the at least one cylinder bore further comprises a flared end, wherein the second cylindrical portion is disposed between the flared end and the transition portion, the flared end having an inner diameter greater than an inner diameter of the second cylindrical portion.

13. The engine block of claim 1, wherein the cylinder bore defines a travel region in which a piston travels and a non-travel region outside a travel range of the piston, wherein the first cylindrical portion is disposed in the travel region, and the second cylindrical portion and the transition portion are disposed in the non-travel region.

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