Disc brake assembly having shared torque-receiving components

Abstract: In one embodiment, a disc brake assembly (100) for use with a rotor (20) includes a parking disc brake (40) and a pair of service disc brakes (30). The parking disc brake (40) is provided between the two service disc brakes (30), and the parking and service disc brakes (30, 40) are adapted to be mounted in a circumferential direction along the rotor (20). At least one component part of at least one service disc brake (30) is used as a torque-receiving part of the parking disc brake (40). In one embodiment, the torque-receiving part is a caliper (31, 32).

Description: Technical Field The present invention relates to a disc brake assembly for use with a rotor and suitable for a vehicle, such as an automobile or a commercial verhicle. More specifically, the present invention relates to improvements of a disc brake assembly having two types of brakes, i.e. a service disc brake and a parking disc brake. Background of the Invention Figs. 12 and 13 disclose a disc brake assembly in accordance with the prior art. This type of conventional disc brake assembly comprises two fixed-caliper service disc brakes 11 and a mechanical floating-caliper parking disc brake 12 mounted between the two fixed-caliper service disc brakes 11. The parking disc brake 12 and the service disc brakes 11 are peripherally distributed along a disc rotor 10 with equal intervals. Calipers 11a of the respective service disc brakes 11 are fixed by two installation bolts 14 on a mounting bracket 13 which is a stationary part of the vehicle. The parking disc brake 12 includes a carrier 12b that supports a parking brake caliper 12a that is fixed on the mounting bracket 13 by second installation bolts 15. The service disc brakes 11 include a pair of frictional pads (not shown in the diagram) that are adapted to be pressed against the side surfaces of the rotor 10 by a fluid pressure operation mechanism built in the service disc brakes 11, thereby causing a braking effect. The parking disc brake 12 includes a pair of friction pads 12c, 12d that are adapted to be pressed against the side surfaces of the rotor 10 by a mechanical operation mechanism built in the parking disc brake 12, thereby causing a brake effect. The above-described disc brake has several disadvantages. For example, the parking disc brake 12 has the carrier 12b as a component. Thus, both the carrier 12b and the second installation bolts 15 that fix the carrier 12b on the mounting bracket 13 require higher material costs, working costs, and surface treatment costs. Also, because the parking disc brake 12 needs to be larger in the circumferential direction of the rotor 10 for the carrier 12b, the size of the parking disc brake 12 is increased. Since the disc brake needs to be somewhat larger, it has disadvantages with respect to the weight and the manufacturing cost as well as the fuel consumption of the vehicle. The document US-A-3 321 049 discloses a mechanical floating head brake of the type which is self-energizing. The brake shoes are anchored to a stationary part by means of angularly disposed converging links so that a movement of the brake shoes during application of the brakes, while the vehicle is moving in a forward direction, will cause a wedging movement of the brake shoes toward the brake disc, thus resulting in an effective self-energizing action. For this purpose, bridging members are provided as a link mechanism in order to transmit the frictional force. The document GB-A-1 490 795 discloses a disc brake, wherein a brake saddle is provided as a carrier on which two pairs of hydraulically operated piston-cylinder units as well as a mechanical parking brake device 5, between the piston-cylinder units, are provided. Hence, all units are mounted on one and the same brake saddle. The integrated arrangement of the brake saddle with the mechanical disc brake and the hydraulic disc brakes at both sides results in the coverage of a large frictional surface of the disc rotor. Summary of the Invention The present invention is intended to improve the above-mentioned aspects. For this purpose, the invention provides a small, but highly efficient device which can be produced at relatively low cost. According to the invention, a disc brake assembly is disclosed, comprising: two hydraulic type disc brakes for a service brake that are adapted to independently be mounted in a circumferential direction along a disc rotor and operable to activate a braking effect by pressing against opposite sides of the disc rotor; and a mechanical floating-caliper type disc brake for a parking brake, the mechanical floating-caliper type parking disc brake being provided between the two hydraulic type disc brakes, wherein at least one component part of each of the two hydraulic type service disc brakes are used as the only torque-receiving parts of the mechanical floating-caliper type parking disc brake, and wherein the mechanical floating-caliper type parking disc brake has no extra torque-receiving part. In one specific embodiment of the invention, the hydraulic type service disc brake is of a fixed-caliper type. In particular, the torque-receiving part can be provided as a caliper. In another specific embodiment of the invention, the hydraulic type service disc brake is of a floating-caliper type. According to a further development of the disc brake assembly according to the invention, the torque-receiving part is a carrier. According to a further development of the disc brake assembly according to the invention, a tightening part is provided adapted to install the mechanical floating-caliper type parking disc brake on a stationary part and is shared to also fix at least one hydraulic type service disc brake on the stationary part. According to a specific embodiment of the invention, the mechanical floating-caliper type parking disc brake comprises a spring chamber operating mechanism. According to a further development of the disc brake assembly according to the invention, the service disc brakes are offset above a first horizontal line passing through the center of a rotor and are placed approximately symmetrically with respect to a second vertical line passing through the center of the rotor. Brief Description of the Drawings Fig. 1 is a front view of a first embodiment of a disc brake assembly in accordance with the invention. Fig. 2 is a plan view of the disc brake assembly of Fig. 1 as viewed in the direction of an arrow II in Fig. 1. Fig. 3 is a plan view of the disc brake assembly of Fig. 1 as viewed in the direction of an arrow III in Fig. 1. Fig. 4 is a cross-sectional view of the disc brake assembly of Fig. 1 taken along a line IV-IV in Fig. 3. Fig. 5 is a corss-sectional view of the disc brake assembly of Fig. 1 taken along a line V-V in Fig. 1. Fig. 6 is a cross-sectional view of the disc brake assembly of Fig. 1 taken along a line VI-VI in Fig. 1. Fig. 7 is a cross-sectional view of the disc brake assembly of Fig. 1 taken along a line VII-VII in Fig. 1. Fig. 8 is a front view of another embodiment of a disc brake assembly in accordance with the invention. Fig. 9 is a plan view of the disc brake assembly of Fig. 8 as viewed in the direction of an arrow IX in Fig. 8. Fig. 10 is a cross-sectional view of the disc brake assembly of Figs. 8 and 9 taken along a line X-X in Fig. 9. Fig. 11 is a cross-sectional view of the disc brake assembly of Figs. 8 and 9 taken along a line XI-XI in Fig. 8. Fig. 12 is a front view of a disc brake assembly in accordance with the prior art. Fig. 13 is a cross-sectional view of the disc brake assembly of Fig. 12 taken along a line XIII-XIII in Fig. 12. Detailed Description of the Invention The present invention is directed toward disc brake systems, in particular for use in vehicles. Specific details of various embodiments of the invention are set forth in the following description and in Figs. 1 to 11 attached thereto in order to facilitate a thorough understanding of such embodiments. In one embodiment according to the invention shown in Figs. 1 and 2 of the drawings, a disc brake assembly 100 includes two hydraulic service disc brakes 30 circumferentially distributed along a rotor 20, and a mechanical parking disc brake 40 provided between the service disc brakes 30. The service disc brake 30 and the parking disc brake 40 are designed so that a part of one of the service disc brakes 30 may have a double function and also work as a torque-receiving part of the parking disc brake 40, and an installation bolt for the parking disc brake 40 may also serve as the installation bolt for one of the service disc brakes 30. The two service disc brakes 30 shown in Figs. 1 and 2 of the drawings are of the fixed-caliper hydraulic type. These service disc brakes 30 apply braking by pressing against opposite sides of the rotor 20. The service disc brakes 30 are offset above a horizontal line passing through the center of the rotor 20 of Fig. 1 and are placed approximately symmetrically with respect to a vertical line passing through the center of the rotor 20. Fig. 3 illustrates a plan view, and Fig. 4 illustrates a partial cross-sectional view of the service disc brake 30. In this embodiment, the service disc brake 30 includes an inner caliper 31 having an inner piston 31a therein, and an outer caliper 32 having an outer piston 32a therein, wherein the inner piston 31a and the outer piston 32a are slidably provided along the sides of the rotor 20. The inner and outer calipers 31 and 32 have portions that cover the periphery of the rotor 20 and are integrated by bolts 35 (see Fig. 1) along the butt joints of both calipers 31 and 32. An inner pad 31b and an outer pad 32b face inner and outer surfaces of the rotor 20, respectively, and are slidably supported by a pair of pins 33 disposed between the inner and outer calipers 31 and 32. The end surfaces of both the inner and outer pads 31b and 32b are also slidably mounted on rails (not shown) of the calipers 31 and 32. A first antirattle spring 34 extends between each of the inner and outer pads 31b and 32b and the pins 33. In order to apply braking, the inner and outer pistons 31a and 32a are projected to press both the inner and outer pads 31b and 32b against the side surfaces of the rotor 20 by a fluid pressure created, for example, by stepping on a brake pedal. As shown in Fig. 1, a first end of the inner caliper 31 opposite from the parking disc brake 40 is attached to a mounting bracket 50 (i.e. a stationary part of the vehicle), by an installation bolt 51. Fig. 5 illustrates a cross-sectional view of the installation bolt 51, which is similar to a conventional device. A second end of the inner caliper 31 situated proximate to the parking disc brake 40, and a guide bush 53 are mounted on the mounting bracket 50 by a guide bolt 52 (see Fig. 1). The parking disc brake 40 has a parking brake caliper 41 that slidably engages the guide bush 53, as best seen in Fig. 6. As shown in Fig. 6, a screw 52a formed only on a top end of the guide bolt 52 is screwed into the mounting bracket 50, and the guide bush 53 covers a shaft 52b of the guide bolt 52. The parking brake caliper 41 is slidably supported along the longitudinal direction of the guide bolt 52 via the guide bush 53. An inner dust boot 55 extends between the parking brake caliper 41 and the inner caliper 31, and an outer dust boot 54 extends between the parking brake caliper 41 and the guide bush 53. The inner and outer dust boots 54 and 55 prevent any objects or particles from interfering with the sliding portion of the parking brake caliper 41 of the parking disc brake 40. The guide bolts 52 serve at least two functions. First, the guide bolts 52 install both adjacent portions of the parking disc brake 40 and the service disc brakes 30, and second they support the parking disc brake 40 under the floating condition, as described more fully below. As shown in Figs. 1 and 2 of the drawings, the parking disc brake 40 is a mechanical type disc brake that is adapted to press against the rotor 20 from opposite sides of the rotor 20 and is provided on an upper part of the vertical line passing through the center of the rotor 20. In this embodiment, the need for an extra torque-receiving part (such as the carrier 12b in the above-explained conventional technology) only for the parking disc brake 40 is eliminated by using the component parts of the two service disc brakes 30 as a torque-receiving part of the parking disc brake 40. As described above, the mechanical parking disc brake 40 comprises the parking brake caliper 41, the caliper 41 being slidably supported on the guide bush 53 in the axial direction of the rotor 20, the guide bush 53 covering the guide bolt 52. The parking disc brake 40 also includes inner and outer parking brake pads 42a and 42b provided on inner and outer rails 31c and 32c of the inner and outer calipers 31 and 32, respectively, of the service disc brakes 30 explained above, and a mechanical operating mechanism 200 adapted to directly press the inner parking brake pad 42a. The mechanical operating mechanism 200 is explained with reference to Fig. 7 of the drawings. A sleeve 43 is forcefully fitted in a cylinder 41a of the parking brake caliper 41. An adjustment nut 44 is slidably inserted in the sleeve 43, and a tappet 45 is screwed into the adjustment nut 44 to press against the inner parking brake pad 42a. A return spring 66 is compressed between the parking brake caliper 41 and the adjustment nut 44 and applies a spring force to continuously abut a washer 46 installed with the adjustment nut 44 against a roller 65 engaged with a recess of an eccentric cam 62a of an operating lever 62. First adjustment teeth 44a provided on the adjustment nut 44 engage second adjustment teeth 47a provided on a circumferential surface of a large diameter portion of an adjustment shaft 47 provided parallel to the adjustment nut 44. The adjustment nut 44 is rotated by operating the adjustment shaft 47 externally from the parking brake caliper 41 to manually adjust the amount of the exposed post-screwed portion of the tappet 45 relative to the adjustment nut 44. A spring chamber assembly 60 is fastened to the parking brake caliper 41 and comprises a built-in spring (not shown in the diagram) and a push rod 61 adapted to exert a stroke by the spring force of the built-in spring, wherein the pressing force of the push rod 61 is transmitted as the pressure force of the tappet 45 via the operating lever 62 etc.. The operating lever 62 comprises the eccentric cam 62a, a pair of linkages 62b integrally extendable from both sides in the axial direction of the eccentric cam 62a, and a receiving part 62c abutting against the push rod 61, wherein the receiving part 62c is a pin bridging between the facing linkages 62b, both ends of which are fixed to the facing linkages 62b. A second antirattle spring 48 is provided between the parking brake caliper 41 and the inner and outer parking brake pads 42a and 42b to prevent any rattling of the parking brake pads 42a and 42b. A needle bearing 63 and a sheet bearing 64 are engaged with the operating lever 62 to provide a smooth rotation of the operating lever 62. A fixed anchor 67 supports the needle bearing 63. A plate 68 is inserted between a flange of the adjustment nut 44 and a return spring 66 and has a low friction layer that does not transmit any torsion force from the return spring 66 to the adjustment nut 44. A dust boot 69 extends between the tappet 45 and the sleeve 43. Hence, the mechanical operating mechanism 200 is similar to the conventional device. In this embodiment of the invention, the end surfaces, when viewed in the circumferential direction of the rotor 20, of both the inner and outer parking pads 42a and 42b of the parking disc brake 40 are slidably attached in the axial direction of the rotor 20 to the adjacent end surfaces of the service disc brakes 30, namely the inner and outer rails 31c and 32c formed at the inner caliper 31 and the outer caliper 32. Thus, the braking torque of the parking disc brake 40 is supported by the services disc brakes 30, in other words the component parts of the service disc brakes 30 are used as the torquereceiving parts of the parking disc brake 40. The braking operation of the disc brake as a parking disc brake 40 is explained next. The parking brake is operated to eject air in the spring chamber assembly 60. As best seen in Fig. 7, the push rod 61 is projected by the spring force of a built-in spring (not shown) and the receiving part 62c of the operating lever 62 is pressed in the direction of the rotor 20. Accordingly, the eccentric cam 62a integrated with each linkage 62b rotates counter-clockwise in Fig. 7. The eccentric cam 62a presses the washer 46 in the direction of the rotor 20 via the roller 65. The pressure force is transmitted to the tappet 45 via the adjustment nut 44, and the tappet 45 presses the inner parking brake pad 42a into contact with the rotor 20. By a reaction force, the parking brake caliper 41 moves backward in the opposite direction of the tappet 45, causing the reaction part 41b of the parking brake caliper 41 to press the outer parking brake pad 42b in the direction of the rotor 20. Thus, the inner and outer parking brake pads 42a and 42b press against the rotor 20 in opposite directions to effectuate braking. Figs. 8 to 11 illustrate another embodiment of a disc brake assembly 300 having two hydraulic, floating-caliper type service disc brakes 130. In the following description, components which are similar or identical to the components of the above-described embodiments are designated with the same numbers, and the explanation of such components is not repeated. Each floating-caliper type service disc brake 130 comprises a carrier 70 fixed to the mounting bracket 50, the installation bolts 51, and the guide bolts 52. A floating caliper 131 having a reaction part 131c is slidably supported by first and second guiding means 71 and 72, respectively, and is thereby fixed to the carrier 70. Inner and outer pads 31b and 32b are slidably provided on a rail 70b (see Fig. 8) of the carrier 70, the rail 70b extending in the axial direction of the rotor 20. In this embodiment, the guide bolts 52 are shared to fix both the guide bush 53, see Fig. 11, on which the parking brake caliper 41 slides, and the carriers 70 comprise the floating-caliper type service disc brakes 130. Furthermore, an end surface of the inner and outer parking brake pads 42a and 42b (the inner parking brake pad 42a is shown in Fig. 8) of the parking disc brake 40 is provided on the respective rails 70a of the carriers 70, and the braking torque of the parking disc brake 40 is received by the carriers 70. With respect to the braking operation of the floating-caliper type service disc brakes 130, the braking effect is caused by the inner pad 31b being pressed against the rotor 20 by the piston 31a built in the inner side of the floating caliper 131, and the outer pad 32b being pressed against the rotor 20 by the reaction part 131c of the floating caliper 131. As described above, the input portion of the floating-caliper type parking disc brake 40 is not limited to the spring chamber type. For instance, a cable may be used to pull the receiving part 62c of the operating lever 62. Furthermore, the mechanical operating portion of the parking disc brake 40 is not limited to the type having the eccentric cam 62a. For example, a leverage type, a ball and ramp type, a wedge type etc. may be used as a mechanical operating portion. In brief, the system only requires a mechanical floating-caliper type disc brake. In the above-described embodiments, the guide bushes 53, on which the parking brake caliper 41 of the parking disc brake 40 slides, and the service disc brakes 30 are both fixed on the mounting brackets 50 by the common guide bolts 52. The installation bolts 51 are not shared. In this way, the braking torque of the parking disc brake 40 is received by the component parts of the service disc brakes 30. Furthermore, in the embodiment of the invention having floating-caliper type service disc brakes 130, the input part of the floating-caliper type service disc brakes 130 is not limited to the type in which the hydraulic pressure is directly supplied. The input source may be a hydraulic pressure, but the floating-type service disc brake 130 may be of the type in which a hydraulic pressure is indirectly supplied such as, for example, via a mechanical mechanism, e.g. an air-chamber type disc brake. As is evident from the above-described embodiments, this invention has several advantages over the prior art. For example, the component parts of the hydraulic type service disc brake are provided in a line to use the torque-receiving parts of the mechanical type parking disc brake. Thus, the stationary part, i.e. the mounting bracket, may be designed smaller, which reduces the weight and the cost of the disc brake assembly. Furthermore, a carrier of the parking disc brake is not necessary which also reduces weight and enables the device to be designed smaller. In addition, since the weight is lower, the fuel consumption rate of the vehicle is improved. Another feature of the invention is that the installation fastener part of the guide bush where the caliper of the parking disc brake slides, and the installation fastener part for the service disc brake, may be shared. This advantageously reduces the number of component parts, and thus the cost, weight and assembly process. Another advantage is that either the fixed-caliper type or the floating-caliper type may be used for the service disc brake, which provides more flexibility. It is readily apparent that the above-described invention has the advantage of wide commercial utility. It should be understood that although specific embodiments of the invention have been described herein for purposes of illustration, the specific form of the invention described above is intended to be representative only, and that various modifications within the scope of these teachings may be made without deviating from the scope of the invention, as will be apparent to those skilled in the art.

Claims: A disc brake assembly, comprising: two hydraulic type disc brakes (30, 130) for a service brake that are adapted to independently be mounted in a circumferential direction along a disc rotor (20) and operable to activate a braking effect by pressing against opposite sides of the disc rotor (20); and a mechanical floating-caliper type disc brake (40) for a parking brake, the mechanical floating-caliper type parking disc brake (40) being provided between the two hydraulic type disc brakes (30, 130), wherein at least one component part (31, 32, 70) of each of the two hydraulic type service disc brakes (30, 130) are used as the only torque-receiving parts of the mechanical floating-caliper type parking disc brake (40), and wherein the mechanical floating-caliper type parking disc brake (40) has no extra torque-receiving part. The assembly according to claim 1, wherein the hydraulic type service disc brake (30) is of a fixed-caliper type. The assembly according to claim 1 or 2, wherein the torque-receiving part is a caliper (31, 32). The assembly according to claim 1, wherein the hydraulic type service disc brake (130) is of a floating-caliper type. The assembly according to claim 1 or 4, wherein the torque-receiving part is a carrier (70). The assembly according to any of claims 1 to 5, wherein a tightening part (50, 52) is provided adapted to install the mechanical floating-caliper type parking disc brake (40) on a stationary part and is shared to also fix at least one hydraulic type service disc brake (30, 130) on the stationary part. The assembly according to any of claims 1 to 6, wherein the mechanical floating-caliper type parking disc brake (40) comprises a spring chamber operating mechanism (60). The assembly according to any of claims 1 to 7, wherein the service disc brakes (30, 130) are offset above a first horizontal line passing through the center of a rotor (20) and are placed approximately symmetrically with respect to a second vertical line passing through the center of the rotor (20).

Inventors: MATSUISHI KAZUYUKI, MATSUISHI, KAZUYUKI, Matsuishi, Kazuyuki c/o Nisshinbo Ind. Inc. Nagoya
Applicants: NISSHIN SPINNING, NISSHINBO INDUSTRIES INC.
Application year: 1999
Main classification: F16D55
IPC codes: F16D55, F16D65, B60T1