Title of Invention

TELESCOPIC CALIPER ASSEMBLY FOR AUTOMOTIVE BRAKING SYSTEM

Abstract

ABSTRACT TELESCOPIC CAUPER FOR AUTOMOTIVE BRAKING SYSTEM A compact Telescopic Caliper Assembly can substantially increase the brake output torque for a given hydraulic input pressure or reduce the required pipeline pressure to realize the design rated brake torque, it is a caliper within a caliper with pistons of different diameters positioned within the caliper housing. Upon actuating the caliper assembly, both the pistons move forward pushing the inboard friction pad towards the rotor and the reaction force causes the static reaction chamber to supplement the outer caliper-housing slide, thereby pushing the outboard friction pad towards the rotor. As two pistons, one within the other, act simultaneously, increase of clamp load is obtained proportional to the inner piston diameter. Increase of brake output torque for a given hydraulic input pressure or reduction in pipeline pressure to realize the design rated brake torque is realized proportional to the area of the inner piston.

Full Text

TELESCOPIC CALIPER ASSEMBLY FOR AUTOMOTIVE BRAKING SYSTEM FIELD OF INVENTION: This invention in general pertains to automobile technoiogy. More particularly this invention pertains to automotive braking system, in particular, this invention relates to the design of a new caliper assembly for automotive braking purposes. At the outset of the description, which follows, it Is to be understood that the ensuing description only Illustrates a particular form of this invention. However, such particular form is only an exemplary embodiment, and without intending to imply any limitation on the scope of this invention, PRIOR ART: It is to be noted that the prior art description gives detailed information of the technology, method, process and system known in the art, it explains the deficiency in the related art and the object of the invention being to overcome or surmount the problem associated with the prior art. This forms the essential feature and the object of the invention. With continues improvement in engine technology, better roads, increasing cruising speeds and stringent statutory/regulatory requirements, there is a inherent need to develop safer braking systems to meet this requirement. Also, to cater to the increasing vehicle weights, increasing speeds and to offer improved braking performance, hydraulic caliper assemblies have increased in size from Φ24 to Φ60 to date. Besides increase in piston diameter, other designs such as the Multiple piston and Opposed piston calipers are in existence today catering for the passenger cars and utility vehicle front brake applications. Attempts to provide a good braking system resulted in providing better friction material and bigger braking systems. Consequences to the above proposal are addressing brake squeal, high fade, high pad wear and bigger actuation systems respectively. Along with the increased cost associated with the above proposals, packaging bigger brakes within the available wheel size has always been a problem. The scope for amplifying the output brake torque is attempted either by increasing the piston diameter or by the use of multiple pistons. Any increase in piston diameter or other designs such as multiple piston calipers necessitated bigger wheel size thereby making packaging a constraint. Besides the above, in the unlikely event of any primary or secondary circuit failure, braking is available only on one front brake and the diagonally opposite rear brake in the case of a X-split system. Braking in such a situation can lead to pulling of vehicle and ineffective brake performance. As such for novelty of the invention, the published information in USA and European patents have been accessed and a list of sample cited patent documents given below cover the following patent specifications: US 6478, 125,1, PCT/EP97/05821, US 6520,299,1, US 6481,544,1, PCT/EP97/05288, PCT/JP97/03507, US 6,511,135.1, PCT/EP97/03269, PCT/EP96, 03319, PCT/EP97/05622, EP 0826 115A1, EP M0847506 Al, -PCT/DE97/02794, PCT/FR98/00809, EP0847 504 Al, PCT/EP98/00118, WO 98/57073, WO 98/29671, WO 98/32988, EP 0874957 A2. On perusal of the cited documents with respect to our invention, it has been found prima-facle that our invention is unique and distinct from the cited inventions. This invention, therefore, proposes a caliper assembly for automotive applications, which has various objectives such as to furnish a greater braking force, than normally possible, to handle higher speeds, larger sizes and greater vehicle weights, without any abnormal change in the dimensions or weight associated with the normal, known caliper assembly. Further objects and advantages of the invention will become apparent from consideration of the drawings and the ensuing description. The foregoing description of outlined rather broadly preferred an alternative feature of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that forms the subject of claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing and modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should realize such equivalent conception do not depart from the spirit and scope of the invention in its broadest form. SUMMARY OF ZNVENTION: The inventors have made great effort to provide a system, which meets the requirement of the industry and overcome the problem associated in the prior art. To achieve the above object according to first aspect and feature of the present invention, a system is provided by which annular area inside the piston is utilized so has to enhance the utility of the caliper assembly for automotive braking system. According to second aspect and feature of the invention in addition to the first feature of the invention, comprises the utilization of annular area by employing additional cylinder (static reaction chamber) and piston arrangement and connected in such way to the existing housing in order to increase the brake torque output for a given pipe line pressure compared to identical caliper design. Further objects of the invention will be dear from the ensuing description. BRIEF DESCRXPTION OF DRAWINGS: The accompanying drawings are intended to provide for the understanding of invention, incorporating in and constitute a part of invention. The drawings illustrate an embodiment of invention and together with the description Illustrate principle of invention. The drawings are given by way of non-limitative example to explain the nature of the invention. For complete understanding of the invention, reference is now made to the following description taken in conjunction with the accompanying drawings. This invention will now be described in further detail with reference to the accompanying drawings which are illustrated in: Figure 1 : shows elevation of the known caliper assembly Figure 2 : shows an embodiment of the proposed caliper assembly, by way of example and not by way of limitation, of the scope of this invention Figure 3 : shows a schematic sketch of the additional feed port and bleed port Figure 4 : shows a schematic sketch of the piston with the relief spaced around the circumference and of a predetermined length Figure 5 : shows a schematic sketch of the static reaction chamber with the lugs of predetermined length and spaced around the circumference; a schematic sketch showing the inner piston Figure 6 : shows a 3D model of the caliper housing assembly Figure 7 : shows a 3D model of the cut-section of the caliper housing assembly Figure 8 : shows a 3D mode! of the exploded view of the caliper housing assembly Figure 9 : shows a graph giving the input-output relationship of the conventional design and the Telescopic design during dynamometer test at 25 kph equivalent vehicle speeds. Figure 10 : shows a graph giving the input-output relationship of the conventional design and the Telescopic design during dynamometer test at 50 kph equivalent vehicle speed. Figure 11 : shows a graph giving the input-output relationship of the conventional design and the Telescopic design during dynamometer test at 75 kph equivalent vehicle speed. Figure 12 : shows a schematic sketch of the 'H'-split braking system with telescopic caliper assembly. Figure 13 : shows a schematic sketch of the 'X'-split braking system with telescopic caliper assembly. DETAILED DESCRIPTION OF PREFERRED EMBODIMENT OF THE IVENTION: Figure-1 illustrates the Single Piston Caliper now in use: The Single Piston caliper uses a clamping action to produce friction between the rotor (10) and the friction pads mounted in the caliper attached to the suspension members. The housing (1) comprises of a cylinder (2), piston (3) and a groove (4) to house the sealing ring (5) for the rollback. Inside the housing, the piston pushes the inboard friction pad (6) against the rotor (10) due to the pressure generated in the master cylinder assembly (7). Due to the reartion force generated by the above action, the housing slides in the carrier (8) holes pushing the outboard friction pad (9) against the rotor (10), thereby generating output brake torque and bringing the vehicle to a halt. The clamp load generated is equivalent to the fluid pressure multiplied by the effective area of the piston. Figures 2 & 3 illustrate the Telescopic Caliper of the invention; The Telescopic caliper according to the invention comprises of a cafiper-rn-caffper with the new design feature explained below on a component basis. It is known In the art that the conventional caliper assembly arrangement has a cylinder and piston arrangement wherein the annular area inside the piston is not utilized for any functional purpose. The salient feature of the invention is to utilize this annular area of the piston whereby the output from the caliper assembly can be enhanced. The invention envisages utilization of the annular area by employing an additional cylinder (static reaction chamber) & piston arrangement and connected in such a way to the existing housing to increase the brake torque output. A static reartion chamber positioned by means of lugs Integrated to the caliper housing and a piston, housed within the above chamber held by means of a sealing ring are all positioned within the annular area of the existing piston. In order to Incorporate this Idea of space utilization in the existing caliper assembly, a structural modification has to be effected in caliper housing, outer piston and static reaction chamber, the change details described are as follows: The design of Caliper Housing (15) is iilustrated in the figure 2 and 3 of the drawings. The housing length is modified in order to take care of the increased length of the outer piston (16), this is necessitated in order to house the additional static reaction chamber (19) and inner piston (20); additional feed port (17) and bleed port (18) are provided to feed the pressurized fluid and to remove air from the caliper assembly respectively from the static reaction chamber (19); a boss (24) is provided at the outer piston (16) entry to integrate the caliper housing (15) and the static reaction chamber (19). The design of outer piston (16) is illustrated in fig. 4 of the drawings. The piston length is increased to house the static reaction chamber (19); a relief (22) to a predetermined length provided at spaced intervals at appropriate angles around the circumference to allow the feed port (17) from the caliper housing (15) to pass freely and provide pressurized fluid to the static reaction chamber (19). The design of static reaction chamber (19) is illustrated in fig. 5 of the drawings. The chamber, static in nature, is designed with lugs (23) of predetermined length provided at spaced intervals around the circumference; the lugs (23) are connected to the boss (24) in the caliper housing (15) to transfer the additional reaction force obtained from the grounding of the inner piston (20) & inboard friction pad (6) with the rotor (10). A sealing ring groove (21) Is also provided inside the static reaction chamber (19) for the rollback action of the inner piston (20) of ΦB. The Telescopic Caliper assembly comprises of a caliper housing (15) which houses the outer piston (16) of diameter (it.A). The said piston will function as described above. A static reaction chamber (19), integrated to the caliper housing (15), which acts as a stationary member is housed within the outer piston (16), As the static reaction chamber (19) is pressurized along with the caliper housing (15), the inner piston (20) pushes the inboard friction pad (6) creating an additional clamp load thereby supplementing the clamp load generated by the outer piston (16). The reaction force obtained because of the damp load from the two pistons when pressed against a rotor (ID) wilt cause the caliper-housing to slide thus generating a substantially higher output brake torque compared to the conventional design. Additional feed port (17) and bleed port (18) are provided for the static reaction chamber (19) with a sealing ring groove (21) provided In the inner diameter of the static reaction chamber (19) to cater for rollback of the inner piston (20). The feed port (17) and bleed port (18) pass through the caliper housing (15) to allow for bleeding and to feed the pressurised fluid from the master cylinder assembly (7). Fig. 6,7 and 8 are the 3D models of the invented caliper assembly indicating assembly of various parts constituting the invented caliper assembly. Figure 6 gives a pictorial view of the caliper housing assembly wherein the assembly of the outer piston, static reaction chamber and the inner piston are shown. The position of the static reaction chamber is designed for mistake-proofing during assembly as shown. Figure 7 gives the cut section of the caliper housing wherein the assembly of outer piston, static reaction chamber and the inner piston is seen with the path for fluid flow clearly shown inside the housing. Figure 8 gives the exploded view of the caliper housing with the constituents shown in the manner of assembly. SALIENT FEATURES OF THE TELESCOPIC CALIPER ASSEMBLY: 1) The telescopic caliper assembly for automotive braking system has a outer piston housed inside the cylinder housing, the static reaction chamber housed Inside the annular area of the outer piston, the inner diameter of the static reaction chamber has a seating ring groove for the inner piston, the inner piston assembled inside the static chamber, the feed port and bleed port for the inner piston pass though the caliper housing, the carrier fixed onto the housing through the sliding pins with the help of guide pin bolts, the inboard & outboard friction pads are assembled onto the carrier in their respective positions and housing assembled. 2) Compared to a identical design, the telescopic caliper assembly gives increased braking torque for a given pipe line pressure or needs substantially reduced pipe line pressure to realize the design rated brake torque. 3) In the telescopic design, the primary circuit can be connected to the outer pistons ΦA and the secondary circuit be connected to the inner piston ΦB and to the rear brakes. In the event of the primary circuit failure, braking action is available from all the four wheels viz., as the outer pistons go out of action, the inner pistons of the telescopic caliper and rear brakes together being connected to the secondary circuit will generate the required braking to meet regulatory requirements. In the event of the secondary circuit failure, braking action is available from the outer piston of the front telescopic caliper assembly thereby meeting the regulatory requirements. Similar benefits as obtained with 'X'-split can apparently be extended to vehicles with "H'-split braking systems too. To validate the Telescopic Caliper design, a prototype sample of size TC57+C38 was developed for the test purpose. A conventional C57 caliper assembly was also taken up for testing to compare the differences in brake torque output. The overall size of the brake assembly, carrier design and the friction pad area, friction pad grade and the test inertia for the conventional and the Telescopic design are maintained identical for the dynamometer test. Inertia dynamometer test was carried out on the conventional design and also on the Telescopic design and the Input-output relationships are compared. In-house dynamometer test was carried out at vehicle equivalent speeds of 25, 50 and 75 kph. Hydraulic pressures of 20 bar to 80 bar in steps of 10 bar is applied to the caliper assembly at each of the above speeds and at an initial braking temperature of lOOC. The input hydraulic pressure and the output brake torque at each speed / pressure level is recorded and presented in Figure-9,10 & 11. For the conventional design, the graph indicating the input pressure and the output brake torque is shown with a square legend. For the same test conditions, the output obtained with the novel design is shown with a triangle legend. An average increase of about 40% in brake torque with the telescopic design for the same pressure input is observed from the test results. The Increase in output agrees with the theoretical prediction and the marginal difference is attributed to the friction material sensitivity to speed, pressure and temperature. The increase in brake torque with the telescopic design for the above test parameters Is clearly ascribed to the newly developed concept as explained in the detailed description of preferred embodiment of the invention. The output brake torque obtained in the Telescopic design is substantially higher as seen in Figure-9,10 & 11. where ΦA and ΦB are the diameters of the outer & inner pistons respectively. This increase in effective piston area is achieved without increasing the external dimensions of the existing design. Hence, the necessity for increasing the radial dimensions of the housing and bigger wheel size is not obligatory. If a single piston, twin piston or an opposed piston caliper were to be designed for an effective piston area of YT, the caliper assembly would invariably be heavier and radially bigger in external dimensions to deliver the same brake output torque. Generally, when brakes are proposed for heavier applications, the brake size (diameter) has to be increased to cater to the higher brake torque. However, in view of this newly developed caliper assembly, as the external dimensions are retained, compactness in packaging can easily be addressed. In the case of the 'X'-Split configuration on vehicles with conventional callpere, when the primary and secondary circuits are connected to the Front-Left/Rear-Right (FLRR) and Front-Right/Rear-Left (FR/RL) brakes respectively, failure of one circuit will lead to braking only on either of the diagonal brakes. This can result in poor braking or pulling of vehicle. In the telescopic design, referring to figure 11, the primary circuit can be connected to the outer pistons ΦA and the secondary circuit be connected to the inner piston ΦB and to the rear brakes. In the event of the primary circuit failure, braking action is available from all the four wheels viz., as the outer pistons go out of action, the inner pistons of the telescopic caliper and rear brakes together being connected to the secondary circuit will generate the required braking. In the event of the secondary circuit failure, braking action is available from the outer piston of the front telescopic caliper assembly thereby meeting the regulatory requirements. Similar benefits as obtained with 'H'-split can apparently be extended to vehicles with 'X'-split braking systems too as shown in fjgure-12. While the above description contains many specificities, these should not be construed as limitations in the scope of the invention, but rather as an exemplification of one preferred embodiment thereof. The terms and expressions in this specification are of description and not of limitation, since there is no intention to exclude any equivalents of the features illustrated and described, but it is understood that various other embodiments of this invention is possible, without departing from the scope and ambit thereof. For example, the invention "Telescopic Caliper" design needs lower pressure for the existing brake torque output and hence optimization of housing wall thickness Is possible. Also, the same design can well be extended to air operated caliper assemblies to enhance the brake torque output for a given input air pressure. Thus the reader will see that the invention "Telescopic Caliper" delivers brake torque substantially higher than the existing caliper assembly, without the necessity of Increasing the caliper size or the wheel size, which results in material savings, cost savings and compactness in packaging. Accordingly, the scope of the invention should be determined not by the embodiments illustrated, but by the appended claims and their legal equivalents. Various nomenclature used in the specification are listed below: Abbreviations A - Outer Piston Diameter -JJB - Inner Piston Diameter TC - Telescopic Caliper TC57+38 - Telescopic Caliper with 57mm as the outer piston diameter and 38mm as inner piston diameter CΦA - Caliper with piston diameter A CΦB - Caliper with piston diameter B Yc - Effective Area of the conventional Caliper YT - Effective Area of the Telescopic Caliper ADVANTAGES OF THE INVENTIONS: 1) The telescopic design extended onto a conventional caliper assembly gives increased braking torque for a given pipe line pressure or needs substantially reduced pipe line pressure to realize the design rated brake torque. 2) The telescopic design gives an improved pressure distribution between the friction pad and the rotor as compared to the conventional design and hence even wear of friction material is envisaged. 3) The telescopic design can be extended to any type/form of caliper assemblies currently in existence. 4) The telescopic caliper design provides braking on all the four wheels in the event of one circuit failed condition on a vehicle with 'H'-spllt configuration. The same can be extended to vehicles with 'X'-split configuration too. 5) For equivalent design consideration, the telescopic caliper design / assembly Is compact in terms of packaging. 6) The telescopic caliper provides better stiffness compared to an equivalent design. CLAIMS 1. A telescopic caliper assembly for automotive braking system comprises a concept of caliper-in-caliper technology so as to achieve increased braking torque. 2. A telescopic caliper assembly for automotive braking system comprises features incorporated in the annular area of the conventional piston whereby output of the caliper assembly is enhanced. 3. A telescopic caliper assembly for automotive braking system wherein the invention envisages utilization of annular area by employing an additional cylinder (static reaction chamber) and piston arrangement being connected in such a way to the existing housing, the said static reaction chamber and the piston being housed in the existing housing and held by means of sealing ring within the annular area of the existing piston. 4. A telescopic caliper assembly for automotive braking system, wherein the outer piston is housed inside the cylinder housing; the static reaction chamber is then housed inside the annular area of the outer piston; the inner diameter of the static reaction chamber will have the sealing ring groove for the inner piston; the inner piston assembled inside the static chamber; the feed port and bleed port for the inner piston will pass though the caliper housing; the carrier fixed onto the housing through the sliding pins with the help of guide pin bolts; the inboard & outboard friction pads assembled onto the carrier in their respective positions and housing assembled, 5. A telescopic caliper assembly, as claimed in claim-3, wherein higher brake torque output is achieved without increasing the radial dimensions of the caliper housing, wherein compactness in packaging is achieved, 6. A telescopic caliper assembly, as claimed in any of the claims 3 to 5, in the case of one circuit failed condition, systems of both 'X'- split and 'H'-split, any of the primary or secondary circuit connected to the inner piston and the other circuit connected to the outer piston will make the front caliper assembly and the rear brakes to continue to operate thereby avoiding ineffective braking or pulling of vehicle. 7. A telescopic caliper assembly, as claimed in claim 3, can also be extended to air operated caliper assemblies. 8. A telescopic caliper assembly, as claimed in claims 1 to 3, gives an improved pressure distribution between the friction pad and the rotor. 9. A telescopic caliper assembly, as claimed in claim 3, give reduction in pipe line pressure to realize the design rated brake torque; this realization being proportionate to area of the inner piston. 10. A telescopic caliper ssembly, as claimed in claim 3, will have better stiffness compared to design built to deliver similar output. 11. A telescopic caliper assembly for automotive braking system as substantially described herein with reference to the accompanying drawings.

Documents:

0418-mas-2002 abstract-duplicate.pdf

0418-mas-2002 abstract.jpg

0418-mas-2002 abstract.pdf

0418-mas-2002 claims-duplicate.pdf

0418-mas-2002 claims.pdf

0418-mas-2002 correspondence-others.pdf

0418-mas-2002 correspondence-po.pdf

0418-mas-2002 description (complete)-duplicate.pdf

0418-mas-2002 description (complete).pdf

0418-mas-2002 drawings-duplicate.pdf

0418-mas-2002 drawings.pdf

0418-mas-2002 form-1.pdf

0418-mas-2002 form-19.pdf