WO2003081072A1

WO2003081072A1 - Improved braking device for vehicles

Info

Publication number: WO2003081072A1
Application number: PCT/IT2003/000158
Authority: WO
Inventors: Lenin Capalbo
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-03-27
Filing date: 2003-03-17
Publication date: 2003-10-02
Anticipated expiration: 2004-09-27
Also published as: AU2003219538A1; ITMI20020641A0; ITMI20020641A1

Abstract

An improved braking device (1,101) for vehicles comprises a rotary element (2,102) having a friction surface and a fixed element comprising a friction lining (3,103) having a friction surface (6) adapted to operate on the friction surface (5, 105) of the rotary element to brake the rotary movement of the rotary element with respect to the fixed element, and being characterized in that the friction surfaces of the rotary element and fixed element have, in cross-section with respect to the advancing direction of the rotary element with respect to the fixed element, a mated contour, comprising a polygonal or mixed line.

Description

IMPROVED BRAKING DEVICE FOR VEHICLES

BACKGROUND OF THE INVENTION

The present invention relates to an improved braking device, specifically designed for vehicles.

As is known, wheeled vehicles, such as cars and trucks comprise braking systems, which conventionally include disc or drum brakes.

The drum brakes, in particular, have a comparatively narrow range of applications .

Drum brakes comprise a drum element fixed to the hub of the wheel, and outside of the brake shoes, thereby providing a larger braking surface, the size being the same, and a good protection for the inner component elements, whereas the dispersion of the generated heat is made through an outer finned arrangement . The drum is usually made of cast iron, steel, aluminium (with a cast iron applied braking band) or it is molded from a steel sheet metal.

Said drum brake comprises moreover two shoes made of cast aluminium, with applied steel plug elements for bearing against the brake cam, or being made of a stamped sheet material, as electrically welded.

With respect to the forward driving rotary direction, a shoe performs a "winding" type of movement, whereas the other shoe performs an "unwinding" type of movement.

The first provide a greater pressure against the drum and, consequently, a greater braking torque; however, this can cause the shoe to auto-lock against the drum, even with the brake in an unlocked condition, merely because of the friction between the drum and the friction lining.

This auto-locking effect, which depends on the geometric conditions of the system and of the friction coefficient, is practically eliminated by arranging the shoe rotary center near the periphery of the drum.

Instead of using supporting pins, the shoes can be supported at their end portions by a simple metal detent element, having a flat bearing surface (the so-called self-centering shoes). The drum brake comprises moreover the friction linings, having a useful thickness of substantially 3 ± 6 mm, which can be consumed before the lining replacement.

The friction linings, in particular, are made of a fabric material or asbestos fibers, which are greatly compressed and impregnated with bakelite or other synthetic materials.

In particular cases, the friction linings comprise moreover embedded threads or chips made of annealed copper.

The friction linings are riveted on the shoes or are glued to said shoes by using specifically designed glueing methods.

The system is completed by one or more shoe return springs, two adjusting cams for adjusting the position of the shoes against the detent arrangement therefor, a further cam (the so-called "olive") or a hydraulic cylinder driving the shoes , against the counter-biassing force of the return spring.

The friction coefficient between the friction linings and drum substantially corresponds to 0.30 ± 0.35; usually, it changes as the operating temperature changes.

The average pressure is of 8 ± 12 kg/cm² (~ 0.8 ± 1.2 MN/m²); the contact arch of each shoe is usually of 100° ÷ 120°. The following types of drum brakes are conventionally used: a) with one winding shoe and one unwinding shoe, in which the performance is the same in the two driving direction of the vehicle; b) with two winding shoes; in this case, during the reverse driving of the vehicle, depending on the types , the two shoes can operate either as unwinding shoes or as winding shoes; c) with two shoes, a primary shoe and a secondary shoe, both operating as winding shoes both in the forward and in the reverse driving of the vehicle; this type of brake is characterized by the fact that the secondary shoe is driven by the primary shoe through a connecting rod coupling or the like; this solution, however, is at present not used in motor vehicles; d) with multiple shoes, i.e. with three or more shoes .

Considering the fact that a winding shoe has a braking efficiency which is about three times that of an unwinding shoe, the overall braking efficiency of each of the above mentioned brakes, assuming to consider as 1 that of the type a), will be: for the type b): efficiency = 1; for the type c): efficiency = 1.5 (in reverse driving = 0.5 or 1.5) ; for the type d) : efficiency = 3.

In this connection, it should be pointed out that the drum brakes must be subjected to regular adjusting operations, which are performed after a given wearing of the friction linings thereof.

One of the most common systems is that using adjusting cam elements.

The adjustment of the clearance can also be performed by an automatic type of adjustment, in which a fixed pin prevents the shoe from being moved away, in its return stroke, from the drum for a distance greater than 1 mm.

The disc brakes, on the other hand, can be of two types, i.e. of a rotary disc type and of a fixed disc type, but the latter is scarcely used.

The rotary disc brake conventionally comprises a disc element made of a special cast iron material, or other materials, or composite materials, and being fixed to the hub of the wheel and two or more sectors made of a friction material glued or riveted on metal small plates, as well as a fixed element, the so-called caliper, bridging the rotary disc.

The friction sectors, supported and guided by the caliper, are pressed, as the brake is actuated, against the two faces of the disc, with a mechanical, hydraulic or mixed type of drive. Because of the comparatively high operating pressures, the friction linings are quickly worn and, accordingly, they have a comparatively large thickness (10 ± 25 mm). Also in such a brake, it is necessary to provide adjusting devices for automatically recovering the operating clearances.

The disc brakes are the mainly used braking systems for cars and the like. Generally, in all of the above disclosed brakes, the braking efficiency depends on the surface involved in the contact between the friction lining and disc or drum surface.

Another important requirement, to provide the vehicle with good stability properties, is that of reducing as far as possible the un-sprung masses and, in the above disclosed braking systems, the disc and drum form un-sprung masses, since they are rigid with the wheels. For increasing the interaction surface between the friction linings and the disc or drum, it is necessary to increase the size of the latter, and, accordingly, its mass, provided that it is not intended to use special materials. Actually, the latter, such as carbon fibers, in addition to having very high costs for a series type of production, are not suitable for a conventional vehicle use, since they operate properly exclusively in a comparatively narrow temperature range. SUMMARY OF THE INVENTION

Thus, the aim of the present invention is to provide a braking device having a braking efficiency greater than that of conventional braking devices having like weights and size.

Within the scope of the above mentioned aim, a main object of the invention is to provide such an improved braking device which can be used on conventionally series made vehicles.

Yet another object of the present invention is to provide such a braking device which is very reliable in operation.

Yet another object of the present invention is to provide such a braking device which can be made by using existing methods, systems and materials.

According to one aspect of the present invention, the above mentioned aim and objects, as well as yet other objects, which will become more apparent hereinafter, are achieved by an improved braking device for vehicles, comprising a rotary element having a friction surface and a fixed element having a friction lining including a friction surface adapted to operate on the friction surface of the rotary element to brake the rotary movement of the rotary element, with respect to the fixed element, and being characterized in that the friction surfaces of the rotary element and fixed element have, in cross-section with respect to the advancing direction of the rotary element, relatively to the fixed element, a mating contour comprising a polygonal or mixed line. BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the present invention will become more apparent hereinafter from the following detailed disclosure of a preferred, though not exclusive, embodiment of the invention, which is illustrated, by way of an indicative, but not limitative example, in the accompanying drawings, where: Figure 1 is a cross-sectioned and partial view of a disc brake according to the invention;

Figures 2-5 are further partial cross- sectioned views illustrating different configurations of the friction lining of the braking device according to the present invention;

Figure 6 is a cross-sectioned front elevation view illustrating a disc of a braking device;

Figure 7 is a further side elevation view of the disc of the preceding figure;

Figure 8 is a further cross-sectioned front elevation view of the drum of a braking device; and

Figure 9 is a further side elevation view of a drum brake comprising the drum element of the preceding figure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the number references of the above mentioned figures , the braking device according to the invention comprise a rotary element having a friction surface and a fixed element having a friction lining including a friction surface adapted to operate on the friction surface of the rotary element to brake the rotary movement of the rotary element, with respect to the fixed element. The braking device, in particular, can comprise a disc brake, as shown in figures 1-7, or a drum brake, as shown in figures 8 and 9.

In the embodiment shown in figures 1-7, the braking device according to the present invention, which has been generally indicated by the reference number 1 , comprises a disc 2 , which is made rotatively rigid with a vehicle wheel, not shown, and on which operate one or more pairs of friction linings 3, which are driven, in a per se known manner, by a caliper 4, rigid with the vehicle chassis.

According to the invention, the friction surface 5 of the disc 2, thereon the friction lining 3 operates, has, in cross-section with respect to the circumferential rotary direction of the disc, a contour comprising a line which, differently from the conventional brakes, is not straight, but being polygonal or "mixed" .

This polygonal or mixed contour or profile is designed for mating with an analogous contour of the friction surface 6 of the corresponding friction lining 3.

Advantageously, the friction surfaces have a slotted contour of triangular, trapezoidal cross- section, including both straight and curved sides, as shown, by way of an example, in figures 2-5.

Thus, the friction surface between the fixed element and friction lining will be remarkably increased, thereby also increasing the braking efficiency.

The inclined sides of the slots will provide, at the braking starting moment, a comparatively small involved surface which will be increased exponentially as the friction lining moves toward the disc to fully contact its surface.

This will provide a very graduated braking, which will be very advantageous from the safety standpoint.

Figures 8 and 9 show a braking system 101 according to the present invention having the configuration of a drum disc. In this case, the rotary element comprises a drum element 102, having an inner friction surface 105 thereon operate a pair of friction linings 103, supported by respective shoes 104.

The operation and general construction of such a drum brake are well known and, accordingly, they will not be herein disclosed in further details.

According to the present invention, the friction surface 105 of the drum 102 has, in cross- section with respect to the circumferential rotary direction of the drum, a contour comprising a line, which is not straight, as in conventional drum brakes, but being polygonal or mixed line.

Such a polygonal contour, or mixed contour, can be mated with a like contour of the friction surface of the corresponding friction lining 103.

It has been found that the invention fully achieves the intended aim and objects. In fact, the invention provides an improved braking device, specifically adapted to be used on motor vehicles, which allows the braking and road driving of the vehicle to be greatly improved.

In practicing, the invention, the used materials, as well as the contingent size and shapes, can be any according to requirements and the status of the art.

Claims

1. An improved braking device for vehicles, comprising a rotary element having a friction surface and a fixed element having a friction lining including a friction surface adapted to operate on the friction surface of the rotary element to brake the rotary movement of the rotary element, with respect to the fixed element, and being characterized in that the friction surfaces of the rotary element and fixed element have, in cross-section with respect to the advancing direction of the rotary element, relatively to the fixed element, a mating contour comprising a polygonal or mixed line.

2. A braking device, according to Claim 1, characterized in that said braking device comprises a disc, which constitutes the rotary element, thereon operates one or more pairs of friction linings, which constitute the fixed element, said friction linings being driven by a shoe made rigid with the chassis of the vehicle.

3. A braking device, according to Claim 2, characterized in that said friction surface of said disc on which operates said respective friction lining comprises, in a cross section with respect to the circumferential rotary direction of the disc, a contour comprising a polygonal or mixed line, said polygonal or mixed contour being mated with a like contour of the friction surface of the corresponding friction lining.

4. A braking device, according to one or more of the preceding claims, characterized in that said friction surfaces have a slotted contour having a triangular, trapezoidal cross-section, with straight and/or curved sides.

5. A braking device, according to one or more of the preceding claims, characterized in that said rotary element comprises a drum having an inner friction surface thereon operate a pair of friction linings, constituting the fixed element, supported by respective supporting shoes .

6. A braking device, according to one or more of the preceding claims, characterized in that said braking device comprises one or more of the disclosed and/or illustrated characteristics.