Claims:We claim:

1. Internal combustion engine crankcase housing configured with profiled undercut recesses for providing stress relief between the side walls from the main bearing walls, wherein the undercut recess is formed between the main bearing housing and main bearing cap of the crankcase.

2. Crankcase housing as claimed in claim 1, wherein the base of the undercut recess is configured substantially curved in the region around the interfacial plane between the main bearing walls and side walls.

3. Crankcase housing as claimed in claim 2, wherein the diameter of the semicircular base is substantially equal to the bolts for clamping the main bearing cap on the main bearing housing of the crankcase.

4. Crankcase housing as claimed in claim 2, wherein the peak point of the undercut recess is above the first thread engagement point in the main bearing housing by a height of at least one-third the diameter of the clamping bolt.

5. Crankcase housing as claimed in claim 2, wherein the material rib thickness between the clamping bolt and the nearest undercut recess wall is at least equal to approximately three-fourth the clamping bolt diameter, preferably maximum equal to the clamping bolt diameter.

6. Crankcase housing as claimed in claim 2, wherein the material rib thickness of the outer side walls of the crankcase is equal to the clamping bolt diameter.

7. Crankcase housing as claimed in claim 2, wherein the inner side of recess disposed adjacent the clamping bolt side is configured extending substantially parallel to the bolt and ending at the interfacial plane between the main bearing walls and the side walls.

8. Crankcase housing as claimed in claim 2, wherein the outer side of the recess base is configured tapering towards the inner side wall of the crankcase.

9. Crankcase housing as claimed in claim 2, wherein the material rib thickness above the peak point of the undercut recess base is at least equal to the clamping bolt diameter.

10. Crankcase housing as claimed in claim 2, wherein the material rib width of the undercut recess base of the crankcase is at least equal three times the clamping bolt radius.


Dated: this 29th day of October, 2015. SANJAY KESHARWANI
APPLICANT’S PATENT AGENT , Description:FIELD OF INVENTION

The present invention relates to a bearing wall structure, particularly to a main bearing wall structure for a crankcase, and more particularly to a main bearing wall structure for a deep-skirt crankcase of a heavy-duty diesel engine.

BACKGROUND OF THE INVENTION

The crankcase is the largest main structure of a diesel IC engine which houses the cylinders. It is the backbone of any diesel engine. The crankcase also acts as the crankshaft housing in a reciprocating type of internal combustion engine. It forms the largest cavity in the diesel IC engine, which is generally located below the cylinders in multi-cylinder diesel engine. It is normally integrated into one or several cylinder blocks.

Apart from housing and thus protecting the crankshaft and connecting rods from foreign objects, the crankcase also caters many other functions in different IC engines, for example - hermetically (may be pressurized as well) or almost hermetically storing the engine oil or forming a rigid structure for joining the engine to the transmission, and also forming a part of the vehicle frame, e.g. in some farm tractors.

Crankcase consists of two distinct sections:

• Top section which encloses the cylinders and cooling jackets and

• Bottom section which is called “Main Bearing Wall” and houses the crankshaft and the bearings thereof.

The crankcase and main bearing caps support the bearing journals and crankshaft and also maintain the alignment of the axis of rotation of the bearing journals housed on different main bearing walls. Main bearing caps of a crankcase are separate parts, which are assembled on the crankcase by means of a plurality of bolts as shown in Figure 4 to 6.

DISADVANTAGES WITH THE PRIOR ART

Generally, the main bearing walls and bearing caps of the crankcase are subjected to severe rotary and reciprocating inertia forces from the crank-train and due to heavy internal combustion loads.

In the existing configuration of the crankcase assembly for diesel IC engines, the main bearing journal and side walls of the crankcase are connected by means of a stiff rib and bulk material is used in the proximity of an interface plane B - B. This construction leads to undesirable load paths to side walls.

Moreover, while assembling the main bearing cap, the crankcase region connecting the side walls to this interface is also subjected to stresses. Therefore, the combustion forces are transferred through the crankshaft and crankshaft tends to bend. This leads to lateral bending of the main bearing walls, which generates still higher stresses that are fluctuating in nature and thus lead to a shorter fatigue life of the crankcase.

Therefore, there is a long felt need for eliminating the disadvantages associated with the conventional crankcase configuration for diesel engine.

OBJECTS OF THE INVENTION

Some of the objects of the present invention - satisfied by at least one embodiment of the present invention - are as follows:

An object of the present invention is to provide a light-weight crankcase for diesel engine.

Another object of the present invention is to provide a crankcase for diesel engine, which reduces in stresses between main bearing walls and side walls.

Still another object of the present invention is to provide a crankcase for diesel engine, which reduces stresses without the customary weight addition.

Yet another object of the present invention is to provide a crankcase for diesel engine, which reduces fluctuating high stresses.

A further object of the present invention is to provide a crankcase for diesel engine, which increases the fatigue life of the crankshaft.

Still further object of the present invention is to provide a crankcase for diesel engine, which avoids undesirable load paths to the side wall of the crankcase.

These and other objects and advantages of the present invention will become more apparent from the following description when read with the accompanying figures of drawing, which are, however, not intended to limit the scope of the present invention in any way.

DESCRIPTION OF THE PRESENT INVENTION

The present invention concerns a heavy-duty diesel engine crankcase configuration, e.g. a 120 HP engine developed by main bearing walls durability simulation by analyzing the fatigue safety factor thereof. The invention proposes to divert the main bearing gas load path on the crankcase to the main bearing bolt boss rib, which is connected to the top section of the crankcase. This configuration significantly reduces the stress developed in this region and therefore, acts as a stress reliever.

In particular, the undercut recess/relief configured in accordance with the present invention is located above the first engaging thread of the main bearing bolt subjected to lower stresses, and thus, it can divert loads along the entire bolt length as well as helps in decoupling the side walls from the main bearing walls. Therefore, there is a considerable reduction in stresses in the region between the main bearing walls and side walls at the interface plane B-B of the main bearing cap. Furthermore, by removing the bulk material connection, the crankcase mass is also substantially reduced, so the imminent weight addition required for strengthening the existing designs of the crankcase is also avoided.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided internal combustion engine crankcase housing configured with profiled undercut recesses for providing stress relief between the side walls and the main bearing walls, wherein the undercut recess is formed between the main bearing walls and the side walls of the crankcase.

Typically, the base of the undercut recess is configured substantially curved in the region around the interfacial plane between the main bearing housing and main bearing cap.

Typically, the diameter of the semicircular base is substantially equal to the bolts for clamping the main bearing cap on the main bearing housing of the crankcase.

Typically, the peak point of the undercut recess is above the first thread engagement point in the main bearing housing by a height of at least one-third the diameter of the clamping bolt.

Typically, the material rib thickness between the clamping bolt and the nearest undercut recess wall is at least equal to approximately three-fourth the clamping bolt diameter, preferably maximum equal to the clamping bolt diameter.

Typically, the material rib thickness of the outer side walls of the crankcase is equal to the clamping bolt diameter.

Typically, the inner side of recess disposed adjacent the clamping bolt side is configured extending substantially parallel to the bolt and ending at the interfacial plane between the main bearing walls and the side walls.

Typically, the outer side of the recess base is configured tapering towards the inner side wall of the crankcase.

Typically, the material rib thickness above the peak point of the undercut recess base is at least equal to the clamping bolt diameter.

Typically, the material rib width of the undercut recess base of the crankcase is at least equal three times the clamping bolt radius.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The present invention will be briefly described with reference to the accompanying drawings, which include:

Figure 1 shows isometric view of a 4-cylinder automobile engine crankcase.

Figure 2 shows the top view of the engine shown in Figure 1 representing a section line A – A cutting the crankcase of the engine along the Y axis.

Figure 3 shows a cross-sectional view of the conventional deep-skirt crank case sectioned along section line A – A depicting the stress concentration, which is also shown inset in an enlarged view.

Figure 4 shows another sectional view of the deep-skirt crankcase of Figure 3, i.e. the area around the assembly of the main bearing journal and bearing cap.

Figure 5 shows yet another sectional view of the deep-skirt crankcase of Figure 3, particularly the region around the main bearing walls and the side walls of the crankcase.

Figure 6 shows a conventional configuration of the deep-skirt crank case having a top section TS enclosing cylinders and cooling jackets (not shown) and a bottom section BS or main bearing walls to house crankshaft and the bearings thereof.

Figure 7 shows the conventional deep-skirt crank case of Figure 6 indicating various important areas thereof.

Figure 8 shows the crankcase configured in accordance with the present invention with an undercut recess for facilitating stress relief.

Figure 9 shows the undercut recess pf Figure 8 shown in an enlarged view depicting different important features thereof.

Figure 10 shows another view of the deep-skirt crankcase, wherein the bulk material connection between the main bearing walls and side walls is removed for configuring an undercut recess or relief in accordance with the present invention.

Figure 11 shows the constructional details of the typical embodiment of the undercut recess shown in Figure 10.

Figure 12 shows the uncut undercut recess cut along section line X – X for representing further details in Figure 14.

Figure 13 shows the rib thickness “t” or the minimum material available above the recess peak point should also be at most equal to the bolt diameter d.

Figure 14 shows the plan view of the undercut recess along section line X – X as shown in Figure 12.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS

In the following, different embodiments of the present invention will be described in more details with reference to the accompanying drawings without limiting the scope and ambit of the present invention in any way.

Figure 1 shows isometric view of a 4-cylinder automobile engine crankcase 10, 100 including a top section for enclosing the cylinders and cooling jackets and a bottom section or main bearing walls for housing the crankshaft and the bearings thereof (not shown). The crankcase and main bearing caps support the bearing journals and crankshaft and also maintain the alignment of the axis of rotation of the bearing journals housed on different main bearing walls.

Figure 2 shows the top view of the engine crankcase 10, 100 of Figure 1 for an automotive internal combustion (IC) engine. It includes 4-cylinders, C1, C2, C3 and C4. The crankcase is sectioned along a section line A – A in Y axis. The crankcase 10 or 100 accommodates all the major engine components.

Figure 3 shows a cross-sectional view of the conventional deep-skirt crank case sectioned along section line A – A depicting the stress concentration by means of fatigue safety factor colored contoured plots for one of the main bearing walls of the crank case viewing from engine front side. Here, the crankcase is configured without any undercut recess. The acceptance criterion for fatigue safety factor is 1.00. The area with maximum stress concentration is particularly shown in an inset enlarged view, wherein the value of fatigue safety factor 0.47 corresponds to the mean stress (MS) 98 MPa and stress amplitude (SA) 125 MPa. The stress concentration adjacent the bulk material connection 16 varies in different locations, e.g. colored profiles elucidate that the extreme stress concentration occurring in region 16 is substantially higher than in other areas.

Figure 4 shows another sectional view of the deep-skirt crankcase of Figure 3, i.e. the area around the assembly of the main bearing journal 12 and the bearing cap 18. The bearing cap 18 is tightened on the main bearing journal 12 by means of a plurality of bolts 20 having threads starting at 24 in the journal 12. The bulk material connects the main bearing journal 12 the side walls 14 with the help of stiff rib 16. This region around the interfacial plane A-A is subjected to undue stresses during the assembly of the main bearing cap 18 on the crankcase 10. Because, walls around the main bearing journal 12 and bearing cap 18 are subjected to rotary and reciprocating inertia forces from crank-train and heavy combustion loads. Further, on starting the operation of the internal combustion engine, the combustion forces are also transferred through the crankshaft, which causes bending thereof. This in turn leads to a lateral bending of the main bearing walls, thus generating still higher fluctuating stresses, which substantially lowers the fatigue life of the crankcase.

Figure 5 shows yet another sectional view of the deep-skirt crankcase of Figure 3; particularly the region around the sectioned main bearing journal and the side walls of the crankcase is marked by the rectangle in red dashed lines.

Figure 6 shows a conventional configuration of the deep-skirt crank case having a top section TS for enclosing cylinder and cooling jackets (not shown) and a bottom section BS or main bearing walls to house crankshaft and the bearing cap bolted on the crankcase by means of a plurality of bolts. The crankcase 10 and main bearing cap 18 support the main bearing journal 12 and crankshaft (not shown). The main bearing journal 12 and side walls 14 of crank case 10 is connected with stiff rib 16 and bulk material near interface plane A-A. This construction leads to undesirable load path to side walls. While assembling the main bearing cap 18, the region of the crankcase 10 connecting from the side walls 14 to this interface plane A-A is subjected to excessive stresses. The combustion forces are also transferred through the crankshaft (not shown) and therefore, the crankshaft bends. This leads to lateral bending of the main bearing walls, which generates still higher stresses, which are fluctuating in nature and ultimately lead to lower fatigue life of the crankcase.

Figure 7 shows a front side view of the conventional deep-skirt crank case of Figure 6 for representing the stress concentration therein during the durability simulation by means of analyzing the fatigue factor of safety. The extreme stress concentration occurs in the region 16 of the bulk material connection. However, other areas 61 and 62 with higher stress concentrations are encircled in red. The colour coding of stress concentrations clearly indicates the important regions of the crankcase, where undesirable load path should be avoided. A section 65 through main bearing journal 12 is also shown inset. It provides the contour plot of the stress concentration along the oil gallery.

Figure 8 shows an embodiment of the deep-skirt crankcase 100 configured in accordance with the present invention, which is provided with an undercut for facilitating stress relief. Here, the major departure from the conventional crankcase configurations shown in Figures 3 to 7 is in the removal of the bulk material connection between the main bearing journal 112 and side walls 114 by providing an undercut recess or relief 126. This construction facilitate an effective stress relief by eliminating any undesirable load paths being formed around the interfacial plane A-A between the main bearing journal 112 and side walls 114, as was discussed above with reference to Figures 3 to 7 of the conventional crankcase 10. Moreover, the position of this Undercut recess /or relief 126 on crank case is configured such that the side walls 114 are decoupled from the main bearing journal 112. So, the undercut recess 126 diverts most of the load along the lengths of the bolts 120.

Figure 9 shows the undercut recess of Figure 8 in an enlarged view depicting different important features thereof. It also shows the stress concentration in the region adjacent the bulk material connection 126 in crankcase 100 of Figure 8. The colour coding of the scalar values of the stress concentration indicates that the highest concentration occurs in the region 1261, where the required factor of safety is now greater than or equal to 1.00. The region of stiff rib and bulk material connection provided with the undercut recess 1261 is now exposed to very mild stress concentration, where the required factor of safety is greater than or equal to 1.00. The region 1261 has a factor of safety equal to 1.00 with 7 MPa as mean stress (sM) and 74 MPa as stress amplitude (sA). The blue colour coded region has a factor of safety in the range of 2.04 to 2.20; while the grey colour coded regions have a factor of safety of the order of 10.00.

Figure 10 shows another view of the deep-skirt crankcase, wherein the bulk material connection between the main bearing walls and side walls is removed for configuring an undercut recess or relief in accordance with the present invention. This is a unique and very critical construction for the wall structure of the main bearing journal. It also reduces the bulk mass and achieves lower stresses during the diesel engine operation. For achieving this, it is ensured that the undercut relief 126 is configured slightly above the first engaging thread 124 of the main bearing bolts 120. Therefore, even on starting the engine, the combustion forces transferred through the crankshaft do not cause lateral bending thereof. This in turn substantially enhances the fatigue life of the crankcase.

Figure 11 shows the constructional details of an embodiment of the undercut recess shown in Figure 10. The undercut recess 126 is configured with diameter d (also the bolt diameter) and the peak point thereof being on the top side, i.e. in the region of the interfacial plane B - B between the main bearing journal 112 and side walls 114 (Figure 11). In a typical configuration of the undercut recess 126, the peak point is configured at least one-third the diameter (d/3) above the first thread engagement point 124 of the internal threads (length of thread engagement being L) provided for tightening the main bearing caps 118 on the main bearing journal 112 (Figure 8). The red portion 122 shows the regions on the main bearing housing and the bearing cap with no internal threading. Further, the minimum thickness of the material between the bolt thread crests and the recess is in the range of 0.7 times diameter (0.7d) to diameter d.

Figure 12 shows the uncut undercut recess cut along section line X – X for representing further details in Figure 14.

Figure 13 shows the rib thickness “t” or the minimum material available above the recess peak point should also be at most equal to the bolt diameter d.

Figure 14 shows the plan view of the undercut recess along section line X – X as shown in Figure 12. The rib height h should be at least 3 times the recess radius R or 1.5 times the bolt diameter d.

WORKING OF THE INVENTION:

With the recess according to the present invention, it is possible suitably configure the crank case based on the durability simulation by analyzing the fatigue factors of safety (SF) at different location in the vicinity of the bulk material connection between the side walls and the main bearing walls.

Therefore, there is a considerable reduction in stresses in the region between the main bearing walls and side walls at the interface plane B-B of the main bearing cap. Moreover, by removing the bulk material connection between these regions, the crankcase mass is substantially reduced, This undercut recess also divert loads along the entire bolt length and readily decouples the side walls from the main bearing walls.

Although, the invention is disclosed and explained in terms of the undercut recesses for automotive engine crankcase, the idea underlying the present invention can be used in any similar construction, where the loads/stresses developed are to be reduced.

For example, where lateral bending of such components/subassemblies generating higher fluctuating stresses, which lead to a shorter fatigue life thereof are diverted to other regions for avoiding an imminent failure of such component/subassembly in the mechanical system.

TECHNICAL ADVANTAGES OF THE PRESENT INVENTION

The undercut recess for stress relief in deep skirt crankcase for internal combustion engines configured in accordance with the present invention has the following advantages:

• Reduces in stresses in the region between main bearing walls and side walls at interface plane of main bearing cap.

• Removes bulk material connection to reduce mass of the crankcase.

• No need for weight addition in the crankcase to reduce stresses.

Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, shall be understood to implies including a described element, integer or method step, or group of elements, integers or method steps, however, does not imply excluding any other element, integer or step, or group of elements, integers or method steps.

The use of the expression “a”, “at least” or “at least one” shall imply using one or more elements or ingredients or quantities, as used in the embodiment of the disclosure in order to achieve one or more of the intended objects or results of the present invention.

The exemplary embodiments described in this specification are intended merely to provide an understanding of various manners in which this embodiment may be used and to further enable the skilled person in the relevant art to practice this invention.

Although, only the preferred embodiments have been described herein, the skilled person in the art would readily recognize to apply these embodiments with any modification possible within the spirit and scope of the present invention as described in this specification.

Therefore, innumerable changes, variations, modifications, alterations may be made and/or integrations in terms of materials and method used may be devised to configure, manufacture and assemble various constituents, components, subassemblies and assemblies according to their size, shapes, orientations and interrelationships.

The description provided herein is purely by way of example and illustration. The various features and advantageous details are explained with reference to this non-limiting embodiment in the above description in accordance with the present invention. The descriptions of well-known components and manufacturing and processing techniques are consciously omitted in this specification, so as not to unnecessarily obscure the specification.

While considerable emphasis has been placed on the specific features of the preferred embodiment described here, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiments without departing from the principles of the invention. These and other changes in the preferred embodiment of the invention will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.