Double caliper braking system

Abstract: A double caliper braking system of differential action, operated by a pressure circuit (11) with two parallel branches (12,13) connected to the calipers (14,15). One of said two branches is provided with a pressure regulator device (18) to cause only one of the two calipers present in the system to act up to a certain threshold value.

Description: This invention relates to a double caliper braking system, and more particularly to a braking system in which the calipers have differential action. The problem of reducing the sometimes annoying noise of braking systems is well known. The noise which arises during weak deceleration braking creates problems, particularly from the servicing aspect, in that it can lead to false estimation of the state of wear of the friction linings. This noise is substantially due to the intrinsic vibration frequencies of one or more parts of the braking system. Attempts to attenuate or eliminate it are generally made by increasing the intrinsic damping of the materials with which the system components are constructed. It should also be noted that the noise tends to manifest itself more easily the larger the discs and pads. DE-A-2 656 247 discloses a double caliper braking system positioned on a disc and connected to a pressure circuit. An object of the present invention is to solve the braking noise problem by providing a double caliper braking system with differential action. A further object is to optimize the braking system action for two very different working conditions, namely light braking for slow deceleration and sudden braking for rapid deceleration, without having to modify the friction materials. These objects are attained by a double caliper braking system according to claim 1. Preferably the pressure under which said one of said calipers acts is between zero and 25 bars. In addition said pressure circuit consists of two parallel branches each of which is connected to one of said calipers. Again according to the present invention, in that branch of said circuit which is connected to said caliper of larger dimensions there is provided a pressure subtraction device arranged to cause said caliper of smaller dimensions to act within a predetermined pressure range. In one embodiment of the intention said pressure subtraction device is a counteracting spring device. Preferably said calipers are arranged in diametrically opposite positions about said disc. The technical characteristics and further advantages will be more apparent from the following description given by way of non-limiting example with reference to tie single accompanying drawing in which: Figure 1 is a schematic view of a braking system according to the invention, and Figure 2 is a diagram showing the pressure variations in the system. In the figures the reference numeral 10 indicates overall a system according to the invention, showing a pressure circuit 11 connected by two branches 12 and 13 to a pair of brake calipers 14 and 15. A braking rim 16 of a disc 17 rotatable on a hub or the like (not shown) is located within the brake calipers 14 and 15. The calipers 14 and 15 are arranged in substantially diametrically opposite positions about the disc 17. In the branch 12 of the pressure circuit 11 there is provided a pressure subtraction device 18, which by way of example is of the counteracting spring type. The graph of Figure 2 shows the variation in the pressures of the circuit branches 12 and 13 for a spring preloading which can vary typically between zero and 25 bars. When the brake pedal is operated for slow deceleration, and the circuit pressure does not exceed the value set for the spring of the device 18, only the caliper 15 is operated, by the circuit branch 13. As the caliper 15 including all its components (pads included) is smaller than the disc 17 or the other caliper 14, noise is no longer manifested. On acting forcibly on the brake pedal, and thus for sudden braking, the pressure in the circuit 11 exceeds that of the device 18 to also allow the caliper 14 to operate. This advantageously optimizes the braking system for two very different working conditions without compromising the friction material, thus making powerful braking and low wear coupled with noiselessness simultaneously possible.

Claims: A double caliper braking system consisting essentially of a disc (17) supported by a hub and rotatable within a pair of brake calipers (14,15) connected to a pressure circuit (11) and fixed to said hub, said one (15) of said calipers (14,15) acting under a pressure in said circuit (11) which is less than the pressure under which said other (14) of said calipers acts, characterised in that one of said brake calipers is of smaller dimensions than the other and said pressure circuit (11) consists of two parallel branches (12,13) each of which is connected to one of said calipers (14,15). A system as claimed in claim 1, characterised in that the pressure under which said one (15) of said calipers acts is between zero and 25 bars. A system as claimed in claim 1, characterised in that in that said branch (12) of said circuit which is connected to said caliper (14) of larger dimensions there is provided a pressure subtraction device (18) arranged to cause said caliper (15) of smaller dimensions to act within a predetermined pressure range. A system as claimed in claim 3, characterised in that said pressure subtraction device (18) is a counteracting spring device. A system as claimed in claim 1, characterised in that said calipers (14,15) are arranged substantially in diametrically opposite positions about said disc (17).

Inventors: PONCINI GIANFRANCO, PONCINI, GIANFRANCO
Applicants: FIAT AUTO SPA, FIAT AUTO S.P.A.
Application year: 1991
Main classification: B60T11
IPC codes: B60T1, B60T11, F16D55