Claims:We claim:

1. A middle-split type crankcase for single-cylinder, low-capacity automotive engines, the crankcase comprises: a rear portion and a front portion connected together by means of a plurality of fasteners to form a housing for:

(i) crankshaft,

(ii) driving gear for mass balancer shaft and oil pump,

(iii) trigger wheel,

(iv) main bearing bush,

(v) front and rear oil seals,

(vi) cylinder block unit,

(vii) mass balancer shafts and its ball bearings, and

(viii) piston assembly,

wherein the rear and front portions of the crankcase when assembled together form a housing to be filled with engine oil through a filling hole provided in the front portion thereof, oil used to lubricate the components and sub-assemblies housed within the assembled crankcase and a drain hole for removing the used lubrication oil before replacing with fresh oil.

2. The crankcase as claimed in claim 1, wherein two parallel holes are bored into the front and rear portions in the assembled condition thereof and one end of the crankshaft each is adapted to be directly supported in the holes on the front and rear portions of the crankcase.

3. The crankcase as claimed in claim 1, wherein two parallel holes are bored into the front and rear portions in the assembled condition thereof and one end of the crankshaft each is adapted to be supported on the inner races of the bushes snugly pre-fitted into the holes in the front and rear portions of the crankcase.

4. The crankcase as claimed in claim 1, wherein the single-cylinder block assembly comprises a piston, a connecting rod and a piston pin and the piston secured in place on the connecting rod by means of Circlip type snap rings disposed on either sides thereof.

5. The crankcase as claimed in claim 1, wherein the flywheel assembly is disposed outside the rear portion of the crankcase and the crankshaft assembly along with gear and trigger wheel and the mass balancer shaft assembly are disposed between the front and rear portions of the crankcase.

6. The crankcase as claimed in claim 1, wherein the oil-pump assembly is mounted on a flange configured outside the front portion of the crankcase.

7. The crankcase as claimed in claim 1, wherein the crankcase acts as housing for other parts as well, such as engine mounting brackets, electronic sensors and starter motor.

8. The crankcase as claimed in claim 1, wherein the lubrication passages are provided at suitable locations to supply oil and oil-seals are installed in the holes provided on the front and rear portions of the crankcase, from which the crankshaft-ends protrude out.

9. The crankcase as claimed in claim 1, wherein a plurality of profiled ribs is configured on the internal and external surfaces of the front and rear portions of the crankcase.

10. The crankcase as claimed in claim 1, wherein cylinder block unit is mounted from the top on the Crankcase assembly by means of a plurality of fasteners.

Dated: this day of 25th August, 2015. SANJAY KESHARWANI
APPLICANT’S PATENT AGENT , Description:FIELD OF INVENTION

The present invention relates to crankcases of internal combustion engines, particularly to low-capacity automobile engines, more particularly to middle-split type crankcases for single-cylinder automobile engines.

BACKGROUND OF THE INVENTION

The crankcase acts as the crankshaft housing in a reciprocating type of internal combustion engine. It forms the largest cavity in the IC engine and is generally located below the cylinders in multi-cylinder engine and normally integrated into one or several cylinder blocks. Crankcase is generally configured as a separate part; however it is frequently made integral with the cylinder bank to form an engine block. But the area surrounding the crankshaft is generally called the crankcase. Generally, crankcase and many other structural units of an IC engine (e.g., cylinders, cylinder blocks, cylinder heads, and their integral combinations) are made of cast iron or cast aluminium by sand casting process. Usually, the crankcase has an aperture in its bottom for attaching an oil pan by means of a bolted joint with oil- seals. The crankcase as well as the casted oil pan includes reinforcing ribs cast therein and also have bosses for facilitating drilling and tapping operations for receiving fasteners e.g. screws/bolts for mounting several other engine parts. Apart from accommodating 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 motor oil or forming a rigid structure for joining the engine to the transmission, and even forming part of the vehicle frame, e.g. in some farm tractors.

DISADVANTAGES WITH THE PRIOR ART

Although, a middle-split crankcase has been used in two-wheelers/motor cycles, it has never been proposed and used for four-wheelers or other multi-axle automotive vehicles, such as light-commercial vehicles (LCVs).

The major disadvantage with the crankcases currently being used in single-cylinder LVCs is their high weight, poor Noise-Vibrations-Harshness (NVH) performance. Such crankcases are also quite bulky and therefore cost significantly high. Due to several sub-assemblies mounted on these crankcases by means of various joints using a number of fasteners, these crankcases are also prone to oil leakages. The crankcase assembly is also very complex and thus time-consuming. The serviceability of the presently available crankcases for single-cylinder LCVs is also not very satisfactory. The current engine architecture consists of crankcase, a separate oil sump, front cover, and flywheel housing. This has a large number of parts, thus requires prolonged assembly lead time. There are also many serviceability issues, leakage prone joints, gaskets and fasteners. Due to different components/sub-assemblies connected to the crankcase, the structural rigidity thereof is also not satisfactory.

Therefore, there is an existing need in low-capacity, single-cylinder, light-commercial vehicles (LCVs) for the crankcases of robust design and low manufacturing cost fully addressing the above mentioned disadvantages.

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 split-crankcase with a robust design for low-capacity automobiles.

Another object of the present invention is to provide a low-weight split-crankcase for low-capacity automobiles.

Still another object of the present invention is to provide a split-crankcase for low-capacity automobiles, which offers better NVH performance.

Yet another object of the present invention is to provide a split-crankcase for low-capacity automobiles, which offers reduced oil-leakages through joints, fasteners and seals.

A further object of the present invention is to provide a split-crankcase for low-capacity automobiles, which encloses various components and/or sub-assemblies.

Still further object of the present invention is to provide a split-crankcase for low-capacity automobiles, which encloses various components and/or sub-assemblies as housing and thus substantially increases structural rigidity thereof.

Yet another object of the present invention is to provide a split-crankcase for low-capacity automobiles, which requires substantially reduced assembly time.

Still another object of the present invention is to provide a split-crankcase for low-capacity automobiles, which facilitates improved serviceability thereof.

One more object of the present invention is to provide a split-crankcase for low-capacity automobiles, which can be manufactured at lower costs than the existing crankcases.

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 middle-split crankcase configuration proposed in accordance with the present invention is the first of its kind for the low-capacity engines for LCVs. The invention is restricted only to LCV Application with Single Cylinder Engine. Here, the oil sump is integrated into the crankcase for better structural rigidity. The front portion of the crankcase facilitates direct mounting of the oil pump assembly and front oil seal, thereby eliminating the necessity of a front cover for the engine. The rear portion of the crankcase includes an integrated flange for starter motor to avoid brackets, thereby further improving the structural rigidity of the crankcase.

The transmission housing is bolted to a flange integrated on the rear portion of the crankcase. Other features, such as piston cooling nozzle, sensor mounting arrangements, lubrication circuits and bearing housings are also provided. A plurality of ribs is also provided on the internal and external surfaces of both front and rear portions of the crankcase for reducing noise and vibrations.

The middle-split crankcase configuration encloses the following essential components/sub-assemblies:

1. Cylinder Block Unit
2. Crankshaft
3. Driving gear for mass balancer shaft and oil pump
4. Trigger wheel
5. Main bearing bush
6. Front and rear oil seals
7. Mass balancer shafts and its ball bearings
8. Piston assembly

The crankcase configuration in accordance with the present invention consists of the split type of configuration, particularly middle-split configuration, which integrates the oil sump, front cover and flywheel housing in a single unit beneficial from the point of view of reducing engine weight and thus reducing the manufacturing costs. This crankcase is also excellent from the serviceability point of view. Further, due to less number of components, this configuration obviates oil leakages prevalent in the existing crankcases. The ribbing pattern internally and externally provided on the crankcase helps in achieving better NVH characteristics and also offers a simple load transfer path.

The middle-split crankcase configuration also acts as a housing for mounting the cylinder block unit, crank train system, balancer shaft drive system, starter motor, flywheel assembly and oil pump drive arrangement. There is also a provision for the smooth flow of lubrication oil to various parts of the engine for better lubrication by cross passages provided therein. The front crankcase also includes the provision for externally mounting the oil pump assembly and dipstick assembly.

The front and rear portions of the crankcase are mounted together with the help of fasteners and liquid sealant is applied on the faces for arresting any possible oil leakages. The crankcase has parallel holes bored into its two ends in its assembled condition. The ends of the crankshaft are directly supported in these holes on the front portion and rear portion of the crankcase. Alternatively the crankshaft ends are supported in the inner races of the bushes snugly pre-fitted into these crankcase holes. In addition, this novel middle-split crankcase also hold engine oil, which is dispensed through a filling hole provided in the front crankcase.

As the engine starts running, this oil-filling hole is used to lubricate internal parts such as the connecting rod bearings, piston, and camshaft assembly. Further, lubrication passages are also provided in the crankcase to supply oil at critical various locations. Oil seals are installed in the crankcase at the locations from where the crankshaft ends protrude out, in order to prevent oil from leaking out during engine operation. This middle-split crankcase configuration also obviates a separate oil-sump to be provided as in the conventional crankcases.

The structural rigidity of the crankcase is substantially improved by providing a plurality of suitably profiled ribs on internal and external surfaces of both the front and rear portions of the crankcase. This in turn reduces the propagation of deformations due to gas or mass forces from the main bearing seats to the outer structure, thereby ensuring a low-noise crankcase and better comfort. The cylinder block unit is mounted on the middle-split crankcase with the help of a plurality of studs. Crankcase is also designed to withstand the bolt forces for transferring a minimum load to the cylinder liner bore which helps in reducing the deformation of the bore. This has a direct impact on engine oil consumption and blow-by targets.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a middle-split type crankcase for single-cylinder, low-capacity automotive engines; the crankcase comprises: a rear portion and a front portion connected together by means of a plurality of fasteners to form a housing for:

(i) crankshaft,
(ii) driving gear for mass balancer shaft and oil pump,
(iii) trigger wheel,
(iv) main bearing bush,
(v) front and rear oil seals,
(vi) cylinder block unit
(vii) mass balancer shafts and its ball bearings, and
(viii) piston assembly,

wherein the rear and front portions of the crankcase when assembled together form a housing to be filled with engine oil through a filling hole provided in the front portion thereof, the oil being used to lubricate the components and sub-assemblies housed within the assembled crankcase and a drain hole for removing the used lubrication oil before replacing with fresh oil.

Typically, two parallel holes are bored into the front and rear portions in the assembled condition thereof and one end of the crankshaft each is adapted to be directly supported in the holes on the front and rear portions of the crankcase.

Typically, two parallel holes are bored into the front and rear portions in the assembled condition thereof and one end of the crankshaft each is adapted to be supported on the inner races of the bushes snugly pre-fitted into the holes in the front and rear portions of the crankcase.

Typically, the single-cylinder block assembly comprises a piston, a connecting rod and a piston pin and the piston is adapted to be secured in place on the connecting rod by means of the Circlip type snap rings disposed on either sides thereof.

Typically, the flywheel assembly is disposed outside the rear portion of the crankcase and the crankshaft assembly along with gear and trigger wheel and the mass balancer shaft assembly are disposed between the front and rear portions of the crankcase.

Typically, the oil-pump assembly is mounted on a flange configured outside the front portion of the crankcase.

Typically, the crankcase acts as housing for other parts as well, such as engine mounting brackets, electronic sensors and starter motor.

Typically, the lubrication passages are provided therein at suitable locations to supply oil and oil-seals are installed in the holes provided on the front and rear portions of the crankcase, from which the crankshaft-ends protrude out.

Typically, a plurality of profiled ribs is configured on the internal and external surfaces of the front and rear portions of the crankcase.

Typically, cylinder block unit is mounted from top on the Crankcase assembly by means of a plurality of fasteners.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

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

Figure 1 shows an exploded perspective view of the middle-split type crankcase in accordance with the present invention manufactured for low-capacity automobiles.

Figure 2 shows an external perspective view of the rear portion of the middle-split type crankcase in accordance with the present invention.

Figure 3 shows an internal perspective view of the rear portion of the middle-split type crankcase in accordance with the present invention.

Figure 4 shows an external perspective view of the front portion of the middle-split type crankcase in accordance with the present invention.

Figure 5 shows an internal perspective view of the front portion of the middle-split type crankcase in accordance with the present invention.

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 an exploded perspective view of the middle-split type crankcase in accordance with the present invention. The crankcase is configured split at the middle by making it into two portions, i.e. a rear portion 110 and a front portion 120 which are fastened together along with various sub-assemblies and components by means of a plurality of bolts 80. The cylinder block assembly 10 is mounted from the top between the rear portion 110 and front portion 120. The cylinder block assembly 10 includes a piston, which in turn consists of a piston 22, connecting rod 24 and piston pin 26. The piston 22 is secured in place on the connecting rods by means of the Circlip type snap rings 28 disposed on both sides thereof. The flywheel assembly 30 is disposed outside the rear portion 110 of the crankcase (on RHS). The crankshaft assembly 40 with gear and trigger wheel and the mass balancer shaft assembly 50 are disposed between the front portion 120 and rear portion 110 of the crankcase. The oil-pump assembly 60 is mounted on a flange outside the front portion 120 of the crankcase. This way, all the components and sub-assemblies are compactly and conveniently disposed on the middle-split crankcase of the single cylinder internal combustion engine of the low-capacity automobile, e.g. an LCV.

Figure 2 shows an external perspective view 112 of the rear portion 110 of the middle-split type crankcase in accordance with the present invention. It includes a plurality of radially and circularly extending ribs 102 for strengthening the crankcase. The flange 108 is provided outside the front portion for bolting the transmission housing (not shown) thereon. The figure also illustrates the locations of the rear oil-seal housing 116 and main bearing bush housing 118 disposed on the bore thereof.

Figure 3 shows an internal perspective view of the rear portion 110 of the middle-split type crankcase in accordance with the present invention. A flange 106 is provided on the inner side of the rear portion 110 of the crankcase for mounting the stator motor thereon. A plurality of radially and circularly extending ribs 106 are also provided for strengthening the rear portion 110.

Figure 4 shows an external perspective view 122 of the front portion 120 of the middle-split type crankcase in accordance with the present invention. The figure illustrates the locations of the front oil-seal housing 126 and main bearing bush housing 128 disposed on the bore thereof. The flange 132 is provided outside the front portion 120 for mounting the oil-pump assembly (not shown) thereon. It also includes a plurality of radially and circularly extending ribs 134 for strengthening the crankcase.

Figure 5 shows an internal perspective view 124 of the front portion 120 of the middle-split type crankcase in accordance with the present invention. A plurality of radially and circularly extending ribs 136 are also provided for strengthening the rear portion 120.

WORKING OF THE INVENTION

1. The Invention acts as a housing to carry various engine parts specified in Figure 1. Apart from carrying the engine parts, the primary purpose of the crankcase is to enclose and support the crankshaft. The crankcase will have parallel holes bored into its two ends in assembled condition. The ends of the crankshaft will be supported by these holes on front and rear crankcase, either directly, or by bushes that have first been fitted snugly into the crankcase holes; the ends of the crankshaft will then rest against the inner races of these bushes.

2. Another important function of the crankcase is to hold engine oil. Oil is dispensed through a filling hole in the front crankcase, and as the engine runs, is used to lubricate internal parts like the connecting rod bearings, piston, and camshaft assembly. Lubrication passages are provided in the crankcase to supply oil at various locations and a drain hole for removing the used lubrication oil before replacing with fresh oil. Oil seals are installed in the crankcase where the crankshaft ends protrude through to prevent oil from leaking out during operation. In Conventional Engines, Separate part called Oil Sump is assembled which acts as a reservoir to hold oil.

3. Another Main Function of the crankcase is to provide structural rigidity for the vehicle. Ribs are provided on internal and external surfaces of both front and rear crankcase which reduces the propagation of deformations due to gas or mass forces from the main bearing seats to the outer structure is largely prevented, thus ensuring a low-noise crankcase and better comfort.

4. Further Cylinder Block Unit is mounted to the Crankcase with help of Studs. Crankcase should be designed to withstand the bolt forces so that minimum load is transferred to Cylinder Liner Bore which helps in Reduced Deformation of the Bore. This has a direct impact on engine oil consumption and blow by targets.

5. Additionally, Crankcase also acts as housing for various parts like Oil Pump, Balancer Shaft Assembly, Engine Mounting Brackets, Electronic Sensors, Starter Motor and Cylinder Block Unit.

TECHNICAL ADVANTAGES AND ECONOMIC SIGNIFICANCE

- Robust Design

- Low Engine Weight

- Better NVH characteristics

- Eliminates requirement of a separate oil-sump

- Reduces leakage prone joints and fasteners

- Reduces deformation of the cylinder liner bore

- Reduces the propagation of deformations due to gas or mass forces from the main bearing seats to the outer structure

- Reduces assembly time

- Improves serviceability

- Low-cost of manufacture

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.