WO2000021771A1

WO2000021771A1 - Wet multiple-disk brake with service and parking control for vehicles

Info

Publication number: WO2000021771A1
Application number: PCT/EP1999/000128
Authority: WO
Inventors: Renato Brevini; Oddino Grasselli
Original assignee: Brevini Riduttori S.P.A.
Priority date: 1998-10-09
Filing date: 1999-01-12
Publication date: 2000-04-20
Also published as: IT1303953B1; ITBO980568A1; ITBO980568A0

Abstract

A multiple-disk brake for vehicles, comprising: a hub (8), which is rigidly coupled to the chassis (1) of a vehicle; a wheel supporting spindle (84), which is rotatably supported in the hub; a reduction unit, which connects the spindle to a driving shaft (5) which is coaxial to the rotation axis of the spindle, the reduction unit comprising an element (66) which is rotationally and coaxially coupled to the spindle; a pack of disks (62, 63) being compressible by means of a disk pusher plate (48) which is actuated by a lever (23); being accommodated in a chamber formed by a cover (3) interposed between the hub (8) and the chassis (1), the lever (23) being articulated to the cover (3) and having a fork-like configuration in which a hydraulic piston (171) jack and a mechanical traction element (16) act at the end of an arm (24), the lever (23) having two prongs (25, 26) between which the driving shaft (5) lies, the prongs (25, 26) acting on the disk pusher plate (48) at two points which lie on a line which intersects the rotation axis (A) at right angles, the lever (23) being articulated to the cover (3) by means of a spherical joint (27).

Description

WET MULTIPLE-DISK BRAKE WITH SERVICE AND PARKING CONTROL FOR VEHICLES Technical Field

The present invention relates to a multiple-disk brake for vehicles, particularly to a multiple-disk parking and service brake for tire-fitted vehicles. Background Art

Multiple-disk brakes for vehicles are already commercially available. Disclosure of the Invention

With respect to conventional brakes, the aim of the present invention is to provide a multiple-disk brake which allows to improve braking performance and particularly to achieve uniform distribution of the braking pressure on the plates so as to ensure high efficiency and uniform wear of the brake.

Within the scope of this aim, an object of the present invention is to provide a brake which is structurally simple and therefore quite inexpensive to manufacture and assemble.

Another object of the present invention is to provide a multiple-disk brake which can be inspected easily and has a particularly effective cooling system which is capable of ensuring optimum operating conditions also in heavy-duty conditions.

This aim, these objects and others which will become apparent hereinafter are achieved, by a multiple-disk brake for vehicles, comprising: a hub, which is rigidly coupled to the chassis of a vehicle; a wheel supporting drum or spindle, which is rotatably supported in said hub; a reduction unit which connects said spindle to a driving shaft which is coaxial to the rotation axis of said spindle, said reduction unit comprising an element which is rotationally and coaxially coupled to said spindle; a pack of laminar friction disks, which is composed of a first plurality of disks, which are rotationally rigidly coupled to said element and axially movable thereon, and of a second plurality of disks, which are rotationally rigidly coupled to said hub and axially movable thereon, said pack of disks being compressible by means of a disk pusher plate which is actuated by a lever; characterized in that a cover is associated with said hub, is interposed between said hub and said chassis and forms a chamber into which said driving shaft protrudes through an opening of said cover, said actuation lever being accommodated in said chamber, being articulated to said cover and having a fork-like configuration in which a hydraulic jack and a mechanical traction element act at the end of an arm, said lever having two prongs between which said driving shaft lies, said prongs acting on said disk pusher plate at two points which lie on a line which intersects said rotation axis at right angles, said lever being articulated to said cover by means of a spherical joint. Brief Description of the Drawings

Further characteristics and advantages of the present invention will become apparent from the following detailed description of a preferred embodiment thereof, illustrated by way of non-limitative example in the accompanying drawings, wherein:

Figure 1 is a longitudinal sectional view of the hub of a vehicle wheel provided with the brake according to the invention;

Figure 2 is an enlarged-scale longitudinal sectional view of a portion of the hub related to the region where the brake is located;

Figure 3 is a front view of the cover;

Figure 4 is a front view of the disk pusher plate;

Figure 5 is a front view of the lever for actuating the disk pusher plate; Figure 6 is a sectional view, taken along the plane VI-VI of Figure 5;

Figure 7 is a sectional view, taken along the plane VII-VII of Figure 5;

Figures 8 and 9 are views of the actuation lever of the disk pusher plate in two operating conditions. Ways of carrying out the Invention

With reference to the above figures, the reference numeral 1 designates the chassis of a vehicle, for example of an electric truck, provided with driving wheels driven by electric motors. circular opening 2 is formed in the chassis 1, and a cover 3 is centered therein; said cover constitutes the shield for closing an electric motor 4, the output shaft 5 of which is supported, by means of bearings 6, so that it can rotate about the axis A in the cover 3. The cover 3 has a cambered shape provided, on the convex surface, with fins 7 which are meant to dissipate the heat generated by the brake.

A hub 8 is centered in the cover 3 and is constituted by a sort of drum which is coaxial to the shaft 5 and is provided with a peripheral flange 9 through which fixing bolts 10 are driven; said bolts engage the chassis 1 and fix the drum so that it cantilevers out from the chassis.

Additional bolts 11 are driven through the peripheral region of the cover 3, engage in the flange 9 and firmly join the cover 3 to the hub 8. The reference numeral 12 designates bolts which pass through the flange 9 and the peripheral region of the cover 3 in order to engage in the frame of the electric motor 4 and fix it to the hub 8. The cover 3 has a peripheral expansion 3a in which a sleeve 13 is provided whose axis is parallel to the axis A; the sleeve 13 hermetically accommodates a cylindrical bar 14 which is provided with an external threaded portion on which a nut 15 is screwed. A length of steel cable 16 is fastened to one end of the bar 14 and ends with a hemispherical head 17. A traction element (not shown) is fastened to the other end of the bar 14 in order to actuate the brake, as will become apparent hereinafter. The nut 15, by abutting against the edge of the sleeve 13, acts as an axial stop element for the bar 14.

A hole 18 is formed in the expansion 3a of the cover 3 and is closed by a plug 19, through which the brake lubrication oil is topped up. The region of the cover 3 in which the seat for the bearing 6 is formed is larger, and a recess 20 is formed therein on the opposite side with respect to the electric motor 4 and proximate to the shaft 5; a stem 21 is inserted in the recess 20 and has a hemispherical head 22. A brake actuation lever 23 is pivoted on the hemispherical head 22. As shown in Figures 5-7, the lever 23 is substantially Y-shaped, with an arm 24 which lies radially with respect to the shaft 5 and with a fork which is composed of two prongs 25 and 26 between which the shaft 5 lies.

The hemispherical head 22 of the stem 21 is articulately engaged in a spherical cavity 27 which lies at the bifurcation of the prongs 25 and 26 between two holes 28 and 29 which have internal collars 30 and 31 on the side facing the cover 3.

Spherical seats 30a, 31a are formed in the collars 30 and 31 for the oscillation of elements for retaining the lever 23. Each one of said elements comprises a ring 32 (see Figure 2) whose outer surface is spherical and complementary to the spherical seats of the collars 30 and 31. The centers of the spherical seats of the collars 30 and 31 lie on a straight line B which is perpendicular to the centerline plane P (see Figure 5) of the lever 23 and passes through the center of the spherical head 22 of the pivot 21 and through the axis A.

Threaded pins 33 are driven through the rings 32 and are screwed in threaded holes formed in the cover 3 proximate to the shaft 5.

A nut 34 is screwed onto each portion of the threaded pins 33 that protrudes into the holes 28 and 29 and acts as an abutment for a respective spring 35 which is interposed between said nut and the ring 32.

A through hole 36 is formed at the end of the arm 24 and is axially aligned with the sleeve 13; said through hole 36 leads to the center of a hollow 37 which is shaped like a spherical dome in which the concavity is directed toward the sleeve 13. A circular plate 38 is retained in the hollow 37 and is shaped complementarily thereto. The circular plate 38 is retained in the hollow 37 by a spring 39 which is interposed between the circular plate 38 and the bottom of a recess 40 formed in the expansion 3a of the cover 3 coaxially to the sleeve 13.

The hole 36 is crossed by the length of cable 16 and has, on the side directed toward the flange, a spherical seat 41 in which the head 17, which is fixed to the end of the length 16, rests.

Two raised portions 42 and 43 are formed at the ends of the prongs 25 and 26, on the side directed toward the cover. In inactive conditions, the two raised portions 42 and 43, due to the thrust applied by the spring 39 and by additional springs 58 described hereinafter, rest on two flat regions 44 and 45 formed on the internal surface of the cover 3 in points which are diametrically opposite with respect to the shaft 5, thus setting the stroke limit of the lever 23. The prongs 25, 26 have, on the opposite side with respect to the cover 3 and opposite the raised portions 42 and 43, two raised portions 46 and 47 whose cylindrical surfaces are coaxial with respect to an axis which is perpendicular to the centerline plane P of the lever 23.

A disk pusher plate 48 rests on the raised portions 46 and 47 and is accommodated in a seat 49 of the hub 8. The plate 48 has a substantially circular contour and is strengthened by four ridges 56a, 56b, 57a, 57b, which are divided by a diametrical region 50 which is centrally provided with an opening 51 for the passage of the shaft 5. The contour of the plate 48 is interrupted by three lobes 52 which are angularly equidistant at 120° to each other. Each lobe 52 protrudes externally from the circumference of the plate, and two machining cutouts 53 and 54 are formed to the sides of each lobe. The seat 49 has a contour which is complementary to the contour of the plate 48, with cutouts 55 for receiving the lobes 52, so as to form a rotation-preventing coupling between the plate 48 and the hub 8.

The plate 48 is kept rested against the raised portions 46 and 47 by means of a set of three springs 58 which are accommodated in holes 59 of the hub and act against the lobes 52. The regions where the raised portions 46 and 47 make contact with the plate 48 are constituted by flat regions 60 and 61 which are formed laterally on the four flat regions 56a, 56b, 57a, 57b to the sides of the opening 51, and the length of the prongs 25, 26 of the lever 23 is such that the raised portions 46, 47 form, together with the flat regions 60 and 61, contact points which lie along a line C which is perpendicular to the centerline plane P and substantially intersects the axis A of the shaft 3.

The seat 49 accommodates a pack of laminar disks, which is composed of a first plurality of stationary disks or lamellae 62 and by a second plurality of disks or lamellae 63 which are interposed between the stationary disks 62 and are turned by the shaft 5 by means of an epicyclic gear system which is generally designated by the reference numeral 64. The disks 62 have an external contour which is substantially identical to that of the plate 48, but have peripheral teeth which engage cutouts which are equidistant from the cutouts 55, so that once they have been inserted in the seat 49 they are rotationally coupled to the hub 8 but are able to move axially.

The disks 63 instead have a circular external contour and an internal set of teeth by means of which they are rotationally coupled to the external set of teeth 65 of an element 66 of the epicyclic gear system 64 which is known as spider.

The disks 62, 63 comprise adjacent annular portions which are interposed between the bottom 67 of the seat 49 and an annular surface 68 of the disk pusher plate. In this manner, when the lever 23 is made to oscillate about the fulcrum constituted by the spherical head 22, the thrust applied to the plate 48 causes the packing of the disks 62, 63 and a braking effect of the spider 66.

The actuation of the lever 23 is performed not only mechanically by means of the traction element that is connected to the bar 14 but also hydraulically. For this purpose, in the flange 9 of the drum 8 there is provided an enlarged region 69 in which a cylindrical chamber 70 is formed whose axis is parallel to the axis A and which is open toward the end of the arm 24 of the lever 23. The chamber 70 is connected to a source of pressurized oil, and a piston 71 can slide hermetically therein; a shank 72 of said piston rests on a flat region 73 of the arm 24 that lies below the hole 36. The epicyclic gear system 64 is of a conventional type and comprises a pinion 74 which is keyed to the output shaft 5 and meshes with a set of three planetary gears 75 which can rotate about pivots 76 which are fixed to the spider 65 and are parallel to the axis A. The planetary gears 75 mesh with a ring gear 77 which is formed inside the hub proximate to the seat 49.

The spider 65 is rotatably supported about the pinion 74 by a bearing 78, and a gear 79 with internal teeth is rigidly coupled thereto on the opposite side with respect to the disk pusher plate 48.

A toothed sprocket 80 (see Figure 1) is rotationally rigidly coupled to the gear 79, and a second set of three planetary gears 81 meshes with it; said planetary gears also mesh with a second ring gear 82 which is formed inside the drum 8 adjacent to the ring gear 77. The planetary gears 81 can rotate about tangs 83 which are parallel to the axis A of a spindle 84 which is supported so that it can rotate in the hub 8 by means of conical-roller bearings 85. The spindle 84 is in practice shaped like a cup with a cylindrical wall 86 which is closed by an end wall 87. The cylindrical wall 86 is provided with a flange 88 for mounting a wheel, only the rim 89 of which has been shown schematically in the drawing. A seat 90 is formed, coaxially to the axis A, in the end wall 87 of the spindle from which the shanks 83 protrude toward the spider 65, and a ring 91 for the axial positioning of the sprocket 80 is driven therein.

The bearings 85 are locked against a collar 92 of the spindle 84, which acts as a shoulder, by means of a ring 93. An annular gasket 94 hermetically engages the collar 92 and closes toward the outside the chamber delimited by the hub 8, by the cover 3 and by the spindle 84. In the drawings, said chamber is generally designated by the reference numeral 95. The oil for lubricating the rotating parts is introduced in the chamber 95 through the plug 19. A plug 96 is provided on the hub 8 to discharge the oil.

The operation of the mechanism according to the invention is fully evident from the above description. When the vehicle is not braked, the springs 39 and 58 keep the lever 23 so that the prongs 25, 26 rest on the flat regions 44, 45 of the cover 3, while the springs 58 keep the disk pusher plate 48 spaced from the disks 62 and 63. In these conditions, the rotation of the driving shaft 5 is transmitted freely to the spindle 84 according to the transmission ratio set by the gear system 64.

In operating conditions, braking occurs by feeding pressurized oil into the chamber 70, so as to actuate the piston 72 against the lever 23, which accordingly performs an oscillation about the head 22. The oscillation of the lever 23 causes an axial thrust on the disk pusher plate 48 which, by mutually packing the disks 62 and 63, generates a braking effect on the spider 66 and ultimately on the spindle 84. It should be noted that during hydraulic braking the traction element 16 does not hinder the movement of the lever 23 (see Figure 8).

The same effect is achieved when the vehicle is parked, when instead of acting on the lever 23 with the piston 72 the traction element 16 is actuated. In this case too, the oscillation of the lever 23 is not hindered by the piston 72 (see Figure 9).

It is evident that the invention perfectly achieves the intended aim and objects. In particular, it should be observed that the spherical fulcrum 22 of the lever 23 and the location of the points of contact of the prongs 25, 26 on the diameter of the plate 48 ensure a balanced thrust on the disk pusher plate 48 and therefore a uniform distribution of the pressure on the disks 62, 63 which is suitable to avoid uneven wear of the brake. Advantageously, the outer fins 7 of the cover 3 are struck by the air stream generated by the fan of the electric motor 4. In this manner, by virtue of the considerable heat exchange surface of the cover, it is possible to keep the temperature of the lubricating oil below critical values even in heavy-duty conditions.

The disclosures in Italian Patent Application No. BO98A000568 from which this application claims priority are incorporated herein by reference.

Claims

1. A multiple-disk brake for vehicles, comprising: a hub, which is rigidly coupled to the chassis of a vehicle; a wheel supporting spindle, which is rotatably supported in said hub; a reduction unit which connects said spindle to a driving shaft which is coaxial to the rotation axis of said spindle, said reduction unit comprising an element which is rotationally and coaxially coupled to said spindle; a pack of laminar friction disks, which is composed of a first plurality of disks, which are rotationally rigidly coupled to said element and axially movable thereon, and of a second plurality of disks, which are rotationally rigidly coupled to said hub and axially movable thereon, said pack of disks being compressible by means of a disk pusher plate which is actuated by a lever; characterized in that a cover is associated with said hub, is interposed between said hub and said chassis and forms a chamber into which said driving shaft protrudes through an opening of said cover, said actuation lever being accommodated in said chamber, being articulated to said cover and having a fork-like configuration in which a hydraulic jack and a mechanical traction element act at the end of an arm, said lever having two prongs between which said driving shaft lies, said prongs acting on said disk pusher plate at two points which lie on a line which intersects said rotation axis at right angles, said lever being articulated to said cover by means of a spherical joint.

2. The brake according to claim 1, characterized in that said spherical fulcrum is constituted by a stem which is fixed in a seat of said cover and has a hemispherical head which is articulately engaged in a complementary hemispherical cavity formed in said lever at the bifurcation of said prongs.

3. The brake according to claim 2, characterized in that two respective holes are formed to the sides of said hemispherical cavity and are internally provided with respective collars which form spherical seats for the oscillation of lever retention elements, each one of said lever retention elements comprising a ring whose outer surface has a spherical configuration which is complementary to that of said spherical seat of the corresponding collar and is engaged therein, said spherical seats of said collars having a center which lies on a straight line perpendicular to the centerline plane of said lever and substantially passing through the center of said spherical head, threaded pins being driven through said rings and being screwed into the cover, a nut being engaged on each one of said pins and acting as an abutment for a respective spring which is interposed between said nut and the respective ring.

4. The brake according to claim 3, characterized in that at the ends of the prongs of said lever, on the side directed toward the cover, two raised portions are formed which, when the lever is inactive, are suitable to abut against two flat regions formed on the internal surface of the cover, said prongs having, in diametrically opposite regions with respect to said driving shaft and on the opposite side with respect to said raised portions, two raised portions whose cylindrical surfaces are coaxial along an axis which is perpendicular to the centerline plane of said lever, said disk pusher plate having regions of contact for said raised portions of said prongs which are constituted by a pair of flat regions adapted to make contact with said raised portions at points of contact arranged along a line which is perpendicular to the centerline plane of said lever.

5. The brake according to claim 4, characterized in that at the end of the arm of said lever there is provided a hole which leads into the center of a spherical hollow whose concavity is directed toward said cover, a circular plate being arranged in said hollow and being shaped like a spherical dome which is complementary to the shape of said hollow, said plate being kept engaged in said hollow by a spring which is interposed between said plate and said cover, said traction element being engaged in said hole.

6. The brake according to claim 5, characterized in that a sleeve is formed on said cover and is axially aligned with said hole, said sleeve hermetically accommodating a cylindrical bar which is provided with a threaded portion which protrudes outside said sleeve and on which a nut for abutment on said sleeve is screwed, a length of steel cable being fastened to one end of the bar, said cable ending with a spherical head which engages a comple entarily shaped seat of said hole of said lever, a traction element for actuating the brake in the parking position being attached to the other end of the bar.

7. The brake according to one or more of the preceding claims, characterized in that an enlarged region is formed in said spindle and a cylindrical chamber is formed therein, said chamber being connected to a source of pressurized oil, a piston being slideable hermetically in said chamber, one end of said piston resting on a flat region of the arm of said lever.