DISC BRAKE DEVICE FOR VEHICLES

Abstract: Arrangement for disc brakes used on motor vehicles, comprising a tappet assembly (14), movable inside the caliper (1) and which, through an axial movement along its longitudinal axis relative to the caliper, can be changed from an active position and a passive position. A regulating device can, through a rotating movement of a tappet extension which is part of the tappet, move an end part of the tappet in an adjustment movement to compensate for changes in the tappet stroke. The tappet comprises a first tappet assembly (16) which is movable axially in the caliper (1) along its longitudinal axis (18) for braking movements, and which is rotatable along its longitudinal axis for adjustment movements. The end part (29) of the tappet (14) is carried by a tappet extension (25) which is non-rotatable relative to the caliper and which is connected to the first tappet assembly, through which rotating movement it performs an axial movement relative to the first tappet assembly.

Description: Disc brake device for vehicles TECHNICAL FIELD: The present invention relates to an arrangement for disc brakes used on motor vehicles according to the preamble of the appended claim 1. BACKGROUND OF THE INVENTION: One problem associated with one commonly used brake system for e.g. heavier vehicles is that the actuating means, which alter the brake pad units between braking and released positions, have end sections which, during certain conditions e.g. during adjustment for the gradual wear of the brake pad units, are affected by torsional forces, which can result in damage to e.g. covering boots and the like with the accompanying deterioration of their function as dirt protection sealing means. SUMMARY OF THE INVENTION: The object of the present invention is to provide an arrangement with which it is ensured that the sealing means of the actuating means can maintain their protective function during a longer time and to therewith reduce the need for service and the risk of brake failure. Said object is achieved by the arrangement according to the present invention, whose features are detailed in appended claim 1. BRIEF DESCRIPTION OF THE DRAWINGS: The invention will be described in greater detail in the following with reference to the accompanying drawings, in which Fig. 1 is a partially sectioned elevational view of a brake caliper equipped with an arrangement according to the present invention, Fig. 2 is a central cross-section of an adjustable actuating means according to the invention, whilst Fig. 3 shows a cross-section through the actuating means according to the invention along the line III-III in Fig. 2. PREFERRED EMBODIMENT: Fig. 1 shows a caliper 1 of the so-called floating type, which thus exerts a highly symmetrical force upon the portion of the brake disc 3 which projects into a recess 2 indicated with phantom lines. The brake disc is mounted in a conventional manner on a wheel hub for rotation together with the wheel of a motor vehicle, e.g. a heavier vehicle such as a truck. This symmetrical force is the effect of the caliper being slidable parallel to the rotational axle of the brake disc 3, in a conventional manner which is not shown. A brake pad unit 4, 5 is arranged on each side of the two sides 6, 7 of the brake disc, whilst actuating means, more specifically two units 8, 9, are arranged on only one side, in the shown example, for direct action against the outside surface 10 of one of the brake pad units. A brake lining 5 is arranged in a conventional manner on one side of the brake pad unit, having a friction surface 11 which is intended to be pressed against the sides of the brake disc by the actuating means 8, 9 in a braking/active position, but to return to a position in which the brake lining 11 is located at a short distance from the brake disc in a released/passive position. The caliper does not necessarily have to be of the floating type. If not, two actuating means are also arranged on the opposite side of the caliper on the outside surface of the brake pad unit 4. In the shown example, the two brake pad units 4, 5 are made as steel plates having brake linings on one side, but can also be made from friction material as one homogeneous unit. The actuating means 8, 9 are mechanical, where their linear reciprocal braking movement between braking position and passive position in the direction of arrows 12 and 13 respectively is achieved by means of the displacement of a tappet assembly 14 having a first tappet section 16 which is movable within a bore 15 in the caliper. The tappet section 16 inside the bore is situated with its longitudi¬ nal axis transversely and substantially perpendicular to the main plane 5' of the brake pad units and, thus, substantially parallel to the rotational axis 17 of the brake disc 3. The brake movement of the tappet assemblies 14 can be achieved in an already known manner using e.g. a pneumatic braking system which is commonly employed for heavier vehicles. The two actuating means 8, 9 have an adjustment arrangement whose purpose is to gradually adjust the position of the actuators as the pads and the disc wear down and can also be effectuated in a known manner. The adjustment arrangement comprises, inter alia, a separ¬ ate, not shown rotating means which can be of an already known construction, and arranged to measure the stroke of the tappet assembly 14 and, further, to activate an adjustment mechanism, incorporated in the actuating means 8, to counteract the tendency towards increased travel caused by the described wear. For this purpose, the rotating means is provided with a pinion wheel 19, which meshes with a gear wheel 20, solidly fixed on the envelope surface of the tappet section 16, to produce a rotational movement of the tappet section 16 about its longitudinal axis 18. The braking movement of the tappet assembly 14, i.e. the switch between released position and braking position for the brake disc, is achieved by applying a pressure to the pressure plate 21 in a known manner by means of a pressure means 21' (see Fig. 1), which pressure is transmitted axially to the tappet section 16 via its annular end surface 22. The pressure plate 21 is, accord- ingly, movable in the axial direction of the actuator means 8, but is rotationally fixed, i.e. is non-rotatable, using any not shown guide means. The tappet section 16 has the shape of a sleeve, having an internal thread 23 meshing with an external thread 24 of a second part of the tappet which constitutes an extension 25 of the tappet assembly 14. The threaded parts form a motion transmitting means, which will be further described below. The extension 25 is axially movable in the direction of the axis 18 in a substantially cylindrical space 26, formed in the tappet section 16, which in its rear portion is sealed by the pressure plate 21 and in its forward portion has a substan¬ tially circular opening 27 through which the extension 25 protrudes with a forward end 28. This end supports a pressure head 29, which is arranged to apply the axial pressure on to the outer surface of the brake pad units 10 and, in so doing, move this to a brake position against the brake disc 3. The extension 25 is, similar to the pressure plate 21, rotationally fixed, which in the shown example is achieved by letting the pressure plate 21 support a rod 30 which is rotationally fixed in the pressure plate by being rigidly mounted at its one end 31 in the pressure plate. The extension 25 has a central groove 32 with an open end 33 in the rear facing direction, through which the rod 30 extends into the groove 32. A non-rotatable connection between the extension 25 and the rod 30 is ensured because the rod has a cross section which is non-circular and the groove 32 has a corresponding cross section, so that the rod 30 is allowed to move axially in the groove 32, but is prevented from mutual relative rotational movement. As is apparent from Fig. 2, the rod and the groove have a hexagonal cross section, but they can have another irregu¬ lar profile, for example equipped with splines. Between the pressure head 29 and the caliper 1 there is a dirt protector in the form of an elastic boots 34 which is attached to an annular groove 35 in the caliper and to an annular groove 36 in the pressure head respectively, to provide a solid attachment and a labyrinth seal. Between the cylindrical envelop surface 37 of the first tappet section 16 and the cylindrical bore 15 in the caliper, there is a sealing member in the form of an elastic sealing ring 39, e.g. an o-ring in an annular groove 40 in the cylinder bore. Between the internal thread 23 and the opening 27 of the space 26 there is an elastic sealing member in the form of an elastic sealing ring 41, which creates a seal between the tappet assembly 14 and its extension and which seals against a suitably cylindrically shaped part 42. The sealing ring 41 is, according to the shown example, arranged in an angular groove 43 in the tappet assembly 14 close to the opening 27. The external thread 24 has an extension in the axial direction which is limited to a portion of the total length of the extension 25. Its length and placement are chosen so that, more exactly, the external thread 24 does not come in contact with the sealing ring 41, but instead so that the area around the groove 43 forms a stop for the extension 25 in its outer position. In this way it is possible to shape the area 42, which cooperates with the sealing ring 41, for maximum sealing interaction with the sealing ring 41. In the event that the boot 34 should collapse, the two sealing rings 39, 41 will protect the inside of the brake system from dirt ingress. The pressure head 29 can, in principle, be non-rotatably fixed on the forward end 28 of the extension 25, but is advantageously somewhat loosely connected to the extension, e.g. via a locking ring 44 in a groove 45 in the pressure head. The functioning of the actuator means 8, 9 and the associ¬ ated adjustment arrangement is thus the following. Activa¬ tion of the brakes is achieved by a common axial movement of all the parts of the tappet assembly 14 belonging to the actuators relative to the caliper 1 and the brake disc 3, that is the pressure plate 21, the tappet section 16, the extension 25 and the pressure head 29. The extension 25 follows the tappet assembly's 14 movement completely due to their threads meshing, in combination with the non- rotatability of the extension relative to the caliper. The gear wheel 20 also follows the axial movement and is allowed to glide relative to the pinion wheel 19, which is wider than the gear wheel and is sufficiently wide to maintain meshing between the pinion wheel 19 and the gear wheel 20 during the total stroke of tappet section 16. In a known manner, no active pull back force applied to the actuating means 8, 9 is required, but the switch to non- braking position is effected by the cessation of pressure on the pressure plate 21 in combination with the retraction of the brake pad units 4, 5 through the rotational movement of the brake disc 3 and irregularities on the brake surface. The not shown rotating means measures the axial position 18 of the actuating means 8, 9, alternatively the movement of the not shown braking mechanism which operates against the pressure plate 21, whereby when reaching a certain amount of axial displacement of the piston member 16 in the direction of the brake disc 3, the rotating means is activated to make the pinion wheel 19 turn a revolution or a part of a revolution. This rotational movement is transmitted via the gear wheel 20 to an opposite rotational movement of the tappet section 16 which is maintained in its axial position by the counter force which is applied at all time to the pressure plate 21, whereby the tappet section 16 during the adjustment movement itself, i.e. its rotational movement, is kept axially fixed. Since the pressure plate 21 is non-rotatably fixed in the caliper 1 there is a certain sliding movement permitted between the pressure plate and the end surface 22 of the tappet section 16. Owing to the fact that the extension 25 is locked with respect to rotational movement via the rod 30 and further- more is meshed with the tappet assembly 14, an axial dis¬ placement of the extension and the pressure head 29 takes place in the direction of the longitudinal axis 18. The direction of the rotational movement of the tappet section 16 and the direction of the threads of the cooperating threaded parts 23, 24 are so chosen that the rotational movement results in a forward movement of the extension 25 and the pressure head 29 towards the pad unit 5. In this manner, a regulation movement in the form of a screw movement takes place, which movement is transmitted to the pressure head 29 or the part which supports the pressure head, that is, the extension 25, in the form of an axial movement, whereby the boot 34 is not subjected to twisting forces, but only its own natural compression and expansion movement. Due to the regulation movement, it is ensured that a certain maximum stroke is not exceeded on account of wear of the pad units' 4, 5 friction layer or wear of the brake disc 3, whereby an unchanged swiftness is maintained for the brake mechanism during its entire service life. The invention is not limited to the description above nor to the examples shown on the drawings, but may be varied within the scope of the appended claims. For example, the blocking of the rotational movement of the extension 25 can be made in a different way, e.g. in the shape of one or more angled or spiral grooves in one tappet member, which grooves cooperate with projections on the other tappet member. The rotating means and the arrangement for activa¬ tion of the brake can comprise conventional parts, for which reason they are not described further.

Claims: CLAIMS 1. Arrangement for disc brakes for motor vehicles, comprising at least one brake pad unit (4, 5) carried in a caliper (1), said brake pad unit having a friction surface (11) on one side, said friction surface being adapted to face a rotatable brake disc (3), whereby, upon activation of the brake, each of said brake pad units is adapted to be moved to an active position by means of at least one actuating means (8, 9) applied on the other side of said brake pad unit, and to be retracted to a passive, retracted position, each of said actuating means (8, 9) being provided with and end portion (21) adapted to convey the movement of said actuating means to the other side of the brake pad unit, whereby said actuating means comprises a tappet assembly (14) which is movable within said caliper (1), thus effecting the brake movement between an active and passive position, respectively, of said actuating means, said actuating means further comprising an adjust- ment means adapted to axially move said end portion (21) in an adjustment movement by rotating a tappet section which forms part of the tappet assembly, in order to compensate for changes in the tappet stroke due to wear of said brake pad unit, characterized in that said tappet assembly (14) comprises a first tappet section (16) being axially movable within the caliper (1) along its longitudinal axis (18) for effecting said braking movement, and rotatable about its longitudinal axis for effecting said adjustment movement, and that said end portion (29) of the tappet assembly (14) is supported by a tappet extension (25) being held non¬ rotatably held relative to the caliper (1) by means of a rotation-locking means (30) and further being connected to the first tappet section (16) by means of a movement transferring means (23, 24), whereby a rotational movement of said first tappet section (16) causes the tappet extension (25) to perform an axial displacement relative to the first tappet section. 2. Arrangement for disc brakes according to claim 1, characterized in that said first tappet section (16) exhibits a sleeve-shape and is in a threaded engagement with the tappet extension (25) . 3. Arrangement for disc brakes according to claim 2, characterized in that said rotation-locking means consists of a rod (30) which is fixed against rotation relative to said caliper (1) and exhibits a non-circular cross-section, and a groove (32) extending axially within said tappet extension (25), said groove having a cross-section which interacts with the cross-section of said rod (30) for achieving a mutual rotation lock. 4. Arrangement for disc brakes according to claim 3, characterized in that said rod (30), at one end thereof, is non-rotationally secured to a pressure plate (21) abutting one end of said first tappet section (16), said pressure plate being non-rotationally secured to said caliper and adapted to convey a force to the tappet assembly for achieving its brake movement. 5. Arrangement for disc brakes according to claim 2, characterized in that said first tappet section (16) exhibits an internally threaded portion (23), and that the tappet extension (25) exhibits an externally threaded portion (24) which is enclosed by the first tappet section (16) during the entire adjustment movement, said first tappet section being provided with sealing means (41) for sealing against a substantially cylindrical sleeve shaped portion (42) of said tappet extension. 6. Arrangement for disc brakes according to claim 1, characterized in that said sealing means (30) is provided between said caliper (1) and said first tappet section (16) 7. Arrangement for disc brakes according to claim 5, characterized in that said externally threaded portion (24), in an outer end position of the tappet extension (25), is arranged to engage a stopping-abutment provided on a portion of the first tappet section (16). 8. Arrangement for disc brakes for motor vehicles, comprising at least one brake pad unit (4, 5) carried in a caliper (1), said brake pad unit having a friction surface (11) on one side, said friction surface being adapted to ' face a rotatable brake disc (3), whereby, upon activation of the brake, each of said brake pad units is adapted to be moved to an active position by means of at least one actuating means (8, 9) applied on the other side (10) of said brake pad unit, and to be retracted to a passive, retracted position, each of said actuating means (8, 9) being provided with an end portion (21) adapted to convey the movement of said actuating means to the other side of the brake pad unit, whereby said actuating means comprises a tappet assembly (14) which is movable within said caliper (1), thus effecting the brake movement between an active and passive position, respectively, of said actuating means, said actuating means further comprising an adjust¬ ment means adapted to axially move said end portion (21) in an adjustment movement in order to compensate for changes in the tappet stroke due to wear of said brake pad units, wherein an elastic boot (34) is attached on the outside of said caliper (1), said boot enclosing said tappet assembly (14) between said caliper and an end portion (29) of said tappet assembly, said tappet assembly comprising a first tappet section (16) being axially movable within said caliper (1) along its longitudinal axis (18) for effecting said brake movement, said end portion of the tappet assembly being supported by a tappet extension (25) adapted to perform an axial displacement relative to the first tappet section (16), characterized in that a first annular sealing means (39) is provided between said first tappet section (16) and said caliper (1), and that a second annular sealing means (41) is provided between said first tappet section (16) and said tappet extension (25).

Inventors: ANGERFORS DAN, ANGERFORS, DAN
Applicants: ANGERFORS DAN, VOLVO AB, AB VOLVO, ANGERFORS, DAN
Application year: 1996
Main classification: F16D65
IPC codes: F16D55, F16D65