Claims:We claim:

1. Stiffener with constrained layer damping for all-aluminum split-type crankcase of single-cylinder engines, wherein the stiffener comprises a steel bracket having a top end moved outside and mounted in alternator mounting boss and a bottom end bolted through the crank case housing from the front side into the rear side thereof; wherein the steel bracket is fixed between two or more vibration prone regions, such as in the balancer shaft region of the crankcase housing by means of respective fasteners through the holes provided at both end thereof.

2. Stiffener as claimed in claim 1, wherein the stiffener is provided with constrained layer treatment for reducing vibrations between the regions connected thereby.

3. Stiffener as claimed in claim 2, wherein the constrained layer treatment comprises:

(i) at least one base layer;
(ii) at least one constraining layer;
(iii) at least one damping layer disposed between the base layer and the constraining layer;

wherein the damping layer is coated with a respective adhesive layer of predetermined thickness on either side thereof.

4. Stiffener as claimed in claim 2, wherein shear stresses act in the longitudinal direction of the stiffener bracket during vibrations in the regions connected thereby to shear the damping material over the whole area thereof.

5. Stiffener as claimed in anyone of the claims 1 to 4, wherein the modal frequency spacing is preferably within a preferred modal frequency band of 250 Hz.

6. Stiffener as claimed in anyone of the claims 1 to 4, wherein the vibrations on the aluminum crankcase are reduced by about 20 to 30%, preferably by about 25%.

7. Stiffener as claimed in anyone of the claims 1 to 4, wherein the point mobility at the location of mounting the stiffener on the aluminum crankcase is improved by about 20 to 30%, preferably by about 25%.

8. Stiffener as claimed in anyone of the claims 1 to 4, wherein the overall amplitudes of all frequencies are reduced by about 20 to 30%, preferably by about 25%.

9. Stiffener as claimed in anyone of the preceding claims, wherein the stiffener is made of metal, preferably steel.

10. Stiffener as claimed in anyone of the preceding claims, wherein the thickness of the damping material enclosed within the constrained damping stiffener is between 4 mm to 5 mm and the thickness of the adhesive layer is between 2.5 mm to 3.0 mm.

Dated: this 21st day of October, 2015. SANJAY KESHARWANI
APPLICANT’S PATENT AGENT , Description:FIELD OF INVENTION

The present invention relates to reducing vibrations and noise in the automotive engines, particularly in crankcase housing of the single-cylinder engines, more particularly in split-type crankcase in single cylinder engines.

BACKGROUND OF THE INVENTION

Normally, noise and vibrations are inherently generated in the automotive engines. These have a negative effect on the surroundings and customers, particularly the drivers of the vehicles. Until recently, cast iron housings were generally used for manufacturing cranks cases of the automotive engines. However, due to the higher weight of cast iron crankcases, Aluminum is more widely used nowadays for manufacturing automobile crankcases because of its light weight. Another advantage of the aluminum crankcases over cast iron crankcases is their more favourable mechanical properties. In particular, the split type of crankcases used in automobiles, tend to radiate much higher noise as compared to the cast iron housings.

DISADVANTAGES WITH THE PRIOR ART

The major disadvantage with the crankcases made of cast iron is their high weight. The crankcases made of cast iron are also quite bulky, which significantly increase the weight of engine.

The noise produced during mechanical operation and internal combustion in the automotive engines causes a serious discomfort to the customers, e.g. vehicle drivers. Even at present, for optimizing the noise produced on light-weight aluminum crankcases, substantial weight is to be added by providing more stiffness and damping to the noise and vibrations produced therein. However, this addition of weight also increases the cost as well as the fuel consumption of the vehicle, which is detrimental to their effective application in automotive crankcases, especially in low-capacity, single cylinder internal combustion engines.

Therefore, there is a long felt need for eliminating the disadvantages associated with the conventional aluminum crankcases by reducing their weight as well as by improving their noise and vibrations characteristics.

DESCRIPTION OF THE PRESENT INVENTION

The stiffener is an integral part of any crankcase for an automotive engine. The stiffener in accordance with the present invention provides damping to noise and vibrations. This stiffener is configured as a separate part, which can be fixed in the engine assembly itself. This offers freedom for assembling and thereby, a proper crankcase packaging can also be achieved.

To increase the structural stiffness and to damp vibrations produced in the split crankcases made of aluminum, the stiffener in accordance with the present invention is provided across the balancer shaft region. This facilitates in increasing stiffness of this region. This has also proved as an excellent measure for reducing the noise and vibration in overall frequency range of human hearing.

Therefore, a stiffener with additional damping capabilities is successfully used to fulfil the practical requirements for aluminum crankcase application, i.e. no additional weight needs to be added to the crankcase for optimizing the noise produced therein. This innovation has also reduced the surface vibration of the aluminum crankcases. Further optimization leads to an overall improved vehicle performance, e.g. reduces the fuel consumption substantially.

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 stiffener for the split-type aluminum crankcase for single-cylinder automotive engine for low-noise operation.

Another object of the present invention is to provide a stiffener for the split-type aluminum crank case for single-cylinder automotive engine for low-vibration operation thereof.

Yet another object of the present invention is to provide a stiffener for the split-type light-weight aluminum crank case for single-cylinder automotive engine.

A further object of the present invention is to provide a stiffener for the split-type aluminum crank case for single-cylinder automotive engine with lower production costs.

Still further object of the present invention is to provide a split-type aluminum crank case for single-cylinder automotive engine with improved sound quality parameters, such as Loudness, Articulation Index (AI) and Sharpness.

Yet further object of the present invention is to provide a stiffener for the split-type aluminum crank case for single-cylinder automotive engine, which reduces noise and vibrations in the overall frequency range of human hearing.

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.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a stiffener with constrained layer damping for all-aluminum split-type crankcase of single-cylinder engines, wherein the stiffener comprises a steel bracket having a top end moved outside and mounted in alternator mounting boss and a bottom end bolted through the crank case housing from the front side into the rear side thereof; wherein the steel bracket is fixed between two or more vibration prone regions, such as in the balancer shaft region of the crankcase housing by means of respective fasteners through the holes provided at both end thereof.

Typically, the stiffener is provided with constrained layer treatment for reducing vibrations between the regions connected thereby.

Typically, the constrained layer treatment comprises:

(i) at least one base layer;
(ii) at least one constraining layer;
(iii) at least one damping layer disposed between the base layer and the constraining layer;

wherein the damping layer is coated with a respective adhesive layer of predetermined thickness on either side thereof.

Typically, shear stresses act in the longitudinal direction of the stiffener bracket during vibrations in the regions connected thereby to shear the damping material over the whole area thereof.

Typically, the modal frequency spacing is preferably within a preferred modal frequency band of 250 Hz.

Typically, the vibrations on the aluminum crankcase are reduced by about 20 to 30%, preferably by about 25%.

Typically, the point mobility at the location of mounting the stiffener on the aluminum crankcase is improved by about 20 to 30%, preferably by about 25%.

Typically, the overall amplitudes of all frequencies are reduced by about 20 to 30%, preferably by about 25%.

Typically, the stiffener is made of metal, preferably steel.

Typically, the thickness of the damping material enclosed within the constrained damping stiffener is between 4 mm to 5 mm and the thickness of the adhesive layer is between 2.5 mm to 3.0 mm.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

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

Figure 1 schematically shows the front view of all-aluminum crankcase housing with stiffener in accordance with the present invention for damping noise and vibrations.

Figure 2 shows a front view of the engine assembly with the crankcase provided with the stiffener of Figure 1.

Figure 3 shows an enlarged front view of the engine assembly with the crankcase provided with the stiffener of Figure 1.

Figure 4 shows a further enlarged side view of the engine assembly provided with the stiffener shown in Figure 3.

Figure 5 shows a graphical representation of the comparison of the point mobility values of the starter motor in the balancer shaft region on the split type aluminum crankcase with the stiffener of the invention and the conventional split-type aluminum crankcase.

Figure 6 shows another graphical representation of the comparison of the point mobility values of the split type aluminum crankcase with the stiffener and with stiffener plus constrained layer damping (CLD) in accordance with the present invention, as well as without the stiffener of the conventional split-type aluminum crankcase.

Figure 7a shows a typical layout of the constrained layer damping in the conventional substrate.

Figure 7b shows a typical layout of the constrained layer damping in the substrate 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 schematically shows the front view of all-aluminum crankcase housing 10 fitted with the with stiffener 20 in accordance with the present invention for damping noise and vibrations by treating it with constrained layer damping material.

Figure 2 shows a front view of the engine assembly with the crankcase housing 10 of Figure 1. It has a stiffener 20 for improving damping and vibrations parameters of the engine, particularly a single-cylinder engine. The stiffener 20 is configured such that the top end 22 of the stiffener 20 is moved outside and mounted in alternator mounting boss 40. The bottom end 24 of the stiffener 20 is bolted through the crank case housing 10 from the front side into the rear side thereof (Figure 3).

Figure 3 shows an enlarged front view of the engine assembly with the crankcase housing 10 of Figure 1. It has a stiffener 20 for improving damping and vibrations characteristics of the engine. The stiffener 20 is configured such that the top end 22 of the stiffener 20 is moved beyond the level of the starter 30 and instead mounted in alternator mounting boss 40 (Figure 4). The bottom end 24 of the stiffener 20 is bolted through the crankcase housing 10 from the front side into the rear side thereof.

Figure 4 shows a further enlarged view of the engine assembly shown in Figure 3, however from the rear-side thereof. It illustrates that for avoiding fouling of the stiffener 20 with the starter 30, the length of the mounting boss 40 is sufficiently extended. In addition, the stud plus nut arrangement is provided to avoid any occurrence of the crankcase sealing issues during the removal of stiffener 20.

Figure 5 shows a graphical representation of point mobility of balancer shaft region on crankcase (10). It shows on X-axis, the frequency (Hz) and on Y-axis point mobility values in (mm/s)/N in Log scale on the LHS and amplitude on the RHS. The baseline or conventional configuration (in Red colour) indicates a sharper curve with several peaks of substantially higher values, whereas the stiffener according to the invention (in Green colour) indicates a smoother curve with comparatively lower values. Root Mean Square (RMS) values are almost halved for the stiffener (0.30) of the invention in comparison to the conventional bracket (0.62). The stiffener according to the present invention has reduced the vibration of the surface by nearly 25 % that too without adding weight as was necessary earlier for increasing the stiffness.

Therefore, the stiffener in accordance with the present invention facilitates enhances damping and thus improves the sound quality parameters like, Loudness, AI and Sharpness by increasing the area in the balancer shaft region, which in turn has proved to be an excellent measure for reducing the noise and vibrations in the overall frequency range of human hearing.

Figure 6 shows another graphical representation of the comparison of the point mobility values in the balancer shaft region on the split type aluminum crankcase with the stiffener and with stiffener plus constrained layer damping (CLD) in accordance with the present invention, as well as without the stiffener of the conventional split-type aluminum crankcase. In any conventional aluminum housing, e.g. aluminum crankcase housing, the stiffener is an integral part of the design. Therefore, two different components used for the stiffener and damping materials to achieve the desired efficiency. This leads to increased material costs and higher weight of the housing, because separate damping material also adds to the overall cost. In this figure, the red curve represents a conventional housing without stiffener, the blue curve represents the housing with stiffener only and the green curve represents the stiffener bracket along with constrained layer treatment done on the bracket in accordance with the present invention. From the graph, it is evident that adding a stiffener bracket (blue line) shifts the frequency from 1700 Hz (red curve) to 1750 Hz (blue curve), while the modal frequency spacing is slightly improved at problem zone of 2400 Hz, i.e. instead of close spacing of, e.g. 2379 Hz and 2450 Hz (red curve) for the conventional housing without stiffener bracket, now the spacing is 2300 Hz and 2550 Hz (blue curve), which is a good spacing for modal frequency of 250 Hz band. However, by adding a constrained layer damping on this stiffener bracket in accordance with the present invention (green curve); the overall amplitudes of all frequencies are reduced by approximately 25%. This is a significant improvement evident from the green curve, which tremendously helps in reducing the vibrations in the aluminum crankcase housing equipped with stiffener with constrained layer damping (CLD). Accordingly, the stiffener in accordance with the present invention is made of steel with a constrained layer damping treatment thereon. This typically configured structural steel stiffener adds stiffness to the connecting parts of the crankcase housing made of aluminum. The CLD also aids in reducing the amplitude of vibrations in a wide range frequency band, as illustrated in this figure. Therefore, this stiffener with CLD treatment is very useful for adding stiffness, in fact, for any aluminum casting and for damping vibrations in the connected regions. An important aspect of this stiffener with CLD treatment is that it has a separate part for reducing vibration, which can be used in high-end of vehicles, where higher costs are acceptable. However, this can be left out for low-end vehicles, where cost is an important criterion. Although, the flexibility achieved by CLD treatment will not be available for such low-end products, which use the conventional system of vibration reduction. It was observed during a test analysis that the point mobility at the mounting location of the stiffener bracket is also improved by 25%. The point mobility provides stiffness to the test area, and the constrained layer damping treatment in the stiffener bracket helps in reducing the overall amplitude of the frequency range.

Figure 7a shows a typical layout of the constrained layer damping in the conventional substrate 10 and a base layer or substrate 20 enclosing a layer of damping material 30 of predefined thickness disposed there between, which in turn is pre-coated on both sides with a respective adhesive layer 40.

Figure 7b shows a typical layout of the constrained layer damping in the substrate in accordance with the present invention. The constrained layer includes a constraining layer 110 and a base layer or substrate 120 enclosing the damping layer 130 therebetween, which is coated on both sides with a respective adhesive layer 140. However, opposed shear forces 150 are acting along the longitudinal direction of the stiffener for providing constrained layer damping to reduce vibrations therein by shearing the damping material over the whole area thereof. However, maximum shearing occurs substantially in the mid-area of this damping layer

TECHNICAL ADVANTAGES AND ECONOMIC SIGNIFICANCE

The stiffening and damping of the split-type aluminum crankcase in accordance with the present invention for low-capacity, single cylinder automotive engine has the following major advantages:

• Stiffener reduces the vibration and noise in the Aluminum crankcase.
• Stiffener and constrained layer damping (CLD) help to improve the sound quality parameters like, Loudness (L), Articulation Index (AI) and Sharpness (S).

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.