WO2005028904A1

WO2005028904A1 - A disk brake

Info

Publication number: WO2005028904A1
Application number: PCT/SE2004/001373
Authority: WO
Inventors: Lars Severinsson
Original assignee: Haldex Brake Products Ab
Priority date: 2003-09-25
Filing date: 2004-09-24
Publication date: 2005-03-31
Also published as: SE0401481D0; DE112004001795T5; SE527182C2; SE0401481L

Abstract

A disc brake with self-servo-effect, comprises a brake yoke (15) placed astraddle of a non-axially movable brake disc (1), brake pads (2, 3) in the brake yoke at either side of the brake disc, and means (7-14) for providing a brake application force - by bringing one of the brake pads into contact with the brake disc - and for controlling the application force and hence the self-servo effect. Mechanical means (34; 42, 43; 54; 55, 56) are provided for concurrently and positively controlling the application of the brake pads (2, 3) at both sides of the brake disc (1).

Description

A DISC BRAKE

Technical Field The present invention relates to a disc brake with self-servo effect, comprising: a brake yoke placed astraddle of a non-axially movable brake disc, brake pads in the brake yoke at either side of the brake disc, and means for providing a brake application force - by bringing one of the brake pads into contact with the brake disc - and for controlling the application force and hence the self-servo effect. Background of the Invention It is well known in the art that a self-servo effect for a disc brake on a vehicle may be obtained by applying a brake pad against the rotating brake disc, where the brake pad is tangentially movable in relation to the brake disc over inclined ramp means or the like. The basic problem with such designs was earlier the relatively poor controllability, but actuation by electric motors with modern electronics and with sensors has generally solved this problem. Actuation by other means, such as electro-hydraulic means, is also possible. A disc brake with self-servo effect as defined above is disclosed in WO 03/071150 from the same applicant as in the present case. In this design the brake application - following the movement in the tangential direction of the ramp plate upon engagement with the brake disc of the brake pad associated with the ramp plate - will occur in that the rollers roll up their ramps in the ramp plate and the ramp bridge, respectively, so that the distance between these two members increases and the brake pads at the two sides of the brake disc are applied thereon. However, there is nothing in the design to positively govern or control the application at both sides, and accordingly irrelevant factors may govern the distribution of the brake effort and wear of the respective brake pads, which of course can be unsatisfactory. The main object of the invention is to remove the above and other shortcomings of the known design. The Invention This is according to the invention attained by mechanical means for concurrently and positively controlling the application of the brake pads at both sides of the brake disc. In a practical design a movable ramp plate is connected to a front brake pad for engagement with a brake disc attached to its shaft. Further, a ramp bridge is floatingly arranged in relation to the brake disc, and means for imparting a control movement on the ramp plate are provided. There are application members between the ramp plate and the ramp bridge for increasing the mutual axial distance between these two members at a relative movement in the tangential direction of the brake disc. A brake yoke is force-transmittingly connected to the ramp bridge and extends to the opposite or rear side of the brake disc, where it is provided with a rear brake pad for braking engagement with the brake disc. In this practical design the application members are mechanically guided for movements substantially parallel to the brake disc. In this way the respective axial movements of the ramp plate and the ramp bridge will be controlled and thus the application at both sides of the brake disc. The application members may be rollers movable in ramps in surfaces facing each other of the ramp plate and the ramp bridge . In a first embodiment, which may be regarded as a principle solution, the rollers are guided by planes, which are axially fixed in relation to the brake disc, whereas in a second embodiment, which is a more practical solution, they are guided by notches in a fixed housing for the disc brake . Each roller may in a practical design have a shaft, which at each end is provided with a rotatable journal ring engaging the planes or the notches, respectively. In order to synchronize the movements of the two rollers a connecting rod, roller cage or the like may connect the shafts of two rollers. The planes or notches are normally parallel to the brake disc but may have specific shapes to provide desired characteristics for the brake. Especially, the notches can be arcuate in order to compensate for the greater elasticity in the force transmitting path to the opposite or rear side of the brake disc . The ramps may have different inclination angles in order to provide desired characteristics for the brake. In a third embodiment of the invention substantially rectangular application members are arranged in correspondingly shaped recesses in the ramp plate and the ramp bridge, respectively, and have shafts guided by planes, which are fixed in relation to the brake disc. In a fourth embodiment of the invention the rollers are pivotally connected to link rods, that at their opposite ends are connected to supports, which are fixed in relation to the brake disc. Brief Description of the Drawings The invention will be described in further detail below under reference to the accompanying drawings, in which Figs 1 and 2 are schematical top views, partly in section, of a first and a second embodiment, respectively, and Figs 3 and 4 are detail views of relevant portions of a third and fourth embodiment, respectively, of a disc brake according to the invention. Detailed Description of Preferrred Embodiments In a vehicle chassis, a disc brake shown in a first embodiment in Fig 1 is placed astraddle of a rotatable brake disc 1, which is to be brakingly engaged by a front brake pad 2 and a rear brake pad 3. These brake pads 2 and 3 are attached to a front and a rear brake pad holder 4 and 5, respectively. The rear brake pad holder 5 is attached to a brake yoke 15 to be described. The brake pads may alternatively lack separate pad holders. It will appear that in both embodiments of the invention the disc brake is floatingly attached in the vehicle chassis, which means that the brake disc 1 is fixed on its shaft. By adjustable distance means 6 to be described below the front brake pad holder 4 is attached to a ramp plate 7. The ramp plate 7 is in turn connected to a ramp bridge 8 by means of application members in the form of rollers 9 between -ramps 7 ' and 8 ' on the ramp plate 7 and the ramp bridge 8, respectively. The arrangement of the rollers 9 will be further described below. The rollers 9 are preferably arranged in a common roller cage (not shown) for obtaining full control and a completely synchronous movement of the rollers 9 (irrespective of their actual number) . The need for a roller cage is especially relevant, if the ramps 7' and 8' are curved for obtaining certain brake characteristics. The ramps 7 ' and 8 ' are exposed to high forces and much wear and can therefore be constructed as inserts of harder and higher quality material. The ramp bridge 8 is floatingly attached in the vehicle chassis and is guided for axial movements (in the axial direction of the brake disc 1) by guide pins 8A, which are fixed in relation to the vehicle chassis. The ramp bridge 8 is provided with means for creating a control movement and for maintaining a certain predetermined slack between on one hand the brake disc 1 and on the other hand the brake pads 2 and 3. An electric motor 10 on the ramp bridge 8 can rotate a motor shaft 11 in either direction. (The unit called "electric motor" also preferably contains a gear box for reducing the rotational speed from the motor as well as a parking and safety brake arrangement.) A bevel gear 12 arranged on the motor shaft 11 is in driving gear engagement with a bevel gear disc 13 rotationally supported by the ramp bridge 8. Eccentrically connected to the bevel gear disc 13 is a crank rod 14 pivotally connected to the ramp plate 7. By turning the bevel gear disc 13 in either direction by means of the bevel gear 12 from the motor 10, the position of the ramp plate 7 in relation to the ramp bridge 8 can be set. When a friction engagement between on one hand the brake pad 2 (and brake pad 3, as will be described) and on the 'other hand the brake disc 1 has been established (over the distance means 6 between the ramp plate 7 and the brake pad holder 4), an application force amplification will be accomplished by the rollers 9 climbing their ramps 7' and 9' in response to a tangential movement of the ramp plate 7 caused by the friction engagement with the brake disc 1. The application force may be accurately controlled by rotating the motor 10 in either direction. With the exception of a slack adjusting function to be described, the rear brake pad holder 5 with its rear brake pad 3 is fixedly connected to the ramp bridge 8 by means of a brake yoke 15. Axial guiding of the brake yoke 15 and reaction force handling from the braking may be accomplished by guide elements 16, fixed in the vehicle chassis. The guide elements 16 have axial surfaces for handling reaction forces from the brake pad holder 5. Each guide element 16 has an axial guide pin 16' cooperating with a hole in the brake yoke 15 for axial guiding of the latter. Throughout this specification, the term "axial" refers to the axial direction of the brake disc 1. The slack adjusting arrangement for the two brake pads 2 and 3 will now be described. The entire arrangement is driven by the electric motor 10 over a drive belt 20, a drive chain or the like via a gear transmission 21 from the motor shaft 11, an electromagnetic clutch 22 and a drive sprocket 23 in driving engagement with the drive belt 20.

The electromagnetic clutch 22 is only engaged, when a slack adjustment is desired. The drive belt 20 may be replaced by a gear train. The drive belt 20 drives two adjustment sleeves 24, which are rotatably arranged in the ramp bridge 8 and are intended for the slack adjustment of the front brake pad 2, and two adjustment nuts 25, which also are rotatably arranged in the ramp bridge 8 but are intended for the slack adjustment of the rear brake pad 3. An adjustment rod 26 has end means 26' in form engagement with one of the adjustment sleeves 24 and with . one of two first adjustment screws 27, each in thread engagement with a bore in the ramp plate 7. The connection by the rod 26 means that the adjustment movement may be transmitted in spite of relative movements between the ramp plate 7 and the ramp bridge 8. The first adjustment screw 27 is rotatably connected to a socket 28 non-rotatably attached to the brake pad holder 4 in such a way that the transmission of tangential forces is secured. The first adjustment screw 27 and the socket 28 together form the distance means 6 with a length adjusted after the wear of the front brake pad 2. Each end of the brake yoke 15 is formed as a second adjustment screw 29 in thread engagement with the adjustment nut 25. The thread directions of the adjustment screws 27 and 29 are such that the distance between the two brake block holders 4 and 5 is decreased at a rotation of the electric control motor 10 for compensating for the wear of the brake pads 2 and 3 at braking. Such a slack adjusting rotation may be separate from a rotation for controlling the application of the brake. A force sensing means 30 of any suitable kind is arranged between the adjustment nut 25 and the ramp bridge 8 in the bottom of the bore provided therein for the nut 25. Such a force sensing means 30 can transmit signals indicative of the axial brake force; such signals can be used for feed-back at braking for controlling the electric control motor 10. A protective bellows 31 of rubber or the like is arranged between the ramp bridge 8 and the brake yoke 15 around each second adjustment screw 29 for preventing the intrusion of moist, dirt and the like. Further, at the side facing the brake pad holder 4 the interior of the disc brake mechanism is protected against the instrusion of moist, dirt and the like in the following way. The ramp bridge 8 has a circumferential wall or sidewall 8' extending towards the brake pad holder 4. In its opening, which has a considerably larger length (in the plane of the drawing) than width (transversely thereto) a lid 32 is attached. The lid 32 is provided with generally circular openings, in which outer peripheries of bellows 33 of rubber or the like are attached, whereas the inner peripheries thereof are attached to the sockets 28. These generally circular bellows will without problems allow lateral and axial movements of the first adjustment screws 27 and the sockets 28. In view of the fact that the disc brake is of the floating type and slack adjusting is performed at both sides of the brake disc 1, a good control over the wear of the two brake pads 2 and 3 and over the distribution of the brake forces to the two sides of the brake disc 1 is obtained. However, an improved control can according to the invention be obtained by guiding the rollers 9 substantially in the plane of the brake disc 1 (or perpendicularly to the axial direction of the disc brake) in relation to the brake disc 1 (or the vehicle chassis) . Practically, this guiding may be performed in the following way in the first embodiment according to Fig 1. Each roller 9 has a shaft 9A, on which a journal ring 9B (preferably at each end of the roller 9) is rotatably journalled. This journal ring 9B is arranged between two planes 34, which are fixed in relation to the disc 1 or the vehicle chassis and are substantially parallel with the disc 1 or thus perpendicular to the axial direction of the disc 1. It should be noted that different practical designs for the journalling of the rollers 9 are possible within the scope of the appended claims. Alternatively, the planes 34 may be substituted by curved surfaces, if special characteristics are desired, for example a compensation for the greater elasticity in the transmission to the rear side of the brake via the brake yoke 15. A second embodiment of a disc brake according to the invention is shown in Fig 2. This second embodiment has great similarities with the first embodiment according to Fig 1. The description of the second embodiment will be limited to those portions where there are differences in relation to the first embodiment, and for the sake of clarity Fig 2 is only provided with a minimum number of reference numerals. The disc brake according to the second embodiment is still of the floating type and is intended for cooperation with a brake disc 1 which is fixed on its shaft. However, here the brake is provided with a brake housing 40, which is fixed in relation to the vehicle chassis and the brake disc 1 and in which the ramp bridge 80 is axially guided. For that purpose the ramp bridge 80 can be provided with slide surfaces 41, and here force-sensing means (not shown) for supplying signals indicative of the tangential brake force may be arranged. As the electric motor 10 here is arranged in the brake housing 40 and the bevel gear 12 shall engage the bevel gear disc 13 on the ramp bridge 80, which is somewhat axially movable in relation to the housing 40, means for allowing axial movements between the motor 10 and the bevel gear 12 shall be provided. The lid 32 with its bellows 33 is in this second embodiment attached in a housing flange 40', and the bellows 31 around each leg of the brake yoke 15 is attached also to the brake housing 40. As in the first embodiment, each roller 9 has a shaft 9A with a journal ring 9B. This journal ring 9B is guided substantially parallel with the disc 1 by a longitudinal notch 42 in the housing 40. For obtaining an even better simultaneous control over the two rollers 9, they are mutually connected over their shafts 9A by means of a connecting rod 43. In order to compensate for the greater elasticity in the force transmitting path to the rear brake pad 3 than to the front brake pad 2, it would be possible to make the notches 42 somewhat arcuate with their ends further away from the disc 1 than their respective central part ("banana-shape"). Other shapes may be envisaged for obtaining other characteristics. Another way of obtaining specific characteristics for the brake would be to adopt varying inclination angles for the ramps 7' and 8'. A third embodiment is shown in Fig 3. With the exception of the portions to be described, it may have the same design as the first embodiment of Fig 1, and reference is accordingly made to the description thereof above. The

^■ 5 ramp plate 7 and the ramp bridge 8 may be recognized in Fig 3. In the first embodiment according to Fig 1 the ramp plate 7 and the ramp bridge 8 may be pressed apart by means of rollers 9 in ramps 7' and 8'. In the present embodiment

10 the roller and ramp arrangement is replaced by generally rectangular application members 50, preferably with rounded corners, being arranged in correspondingly shaped recesses 7" and 8" in the ramp plate 7 and the ramp bridge 8, . respectively. These recesses may in their corners be

15 provided with low friction material 51. One such arrangement is shown, but similar to the embodiment of Fig 1 two or more arrangements may be provided. Each applicatio'n member 50 is provided with a central shaft 52, on which a journal ring 53 (preferably at each

20 end of the application member 50) is rotatably journalled. As in the embodiment of Fig 1, the journal ring 53 is arranged between two planes 54, which are fixed in relation to the brake disc or the vehicle chassis and are substantially parallel with the disc or thus perpendicular

25 to the axial direction of the disc. If there is a mutual transverse movement between the ramp plate 7 and the ramp bridge 8, the application member 50 will tilt around its shaft 52, as is illustrated in Fig 3, which means that the ramp plate 7 and the ramp bridge 8

30 will be pressed apart the same distance for both members, as the shaft 52 is guided and controlled by the planes 54. The same effect as with the embodiment of Fig 1 is thus obtained. A fourth embodiment is shown in Fig 4, where only

35 portions relevant for a proper understanding are illustrated; reference in all other respects is made to the description of Fig 1. One of the at least two arrangements with a roller 9 and ramps 7 ' and 8 ' in the ramp plate 7 and the ramp bridge 8, respectively, is shown. The roller 9 is provided with a shaft 9A. Instead of being guided by planes 34 as in the Fig 1 embodiment, the roller 9 in the Fig 4 embodiment is guided by a link rod 55 pivotally connected at one of its ends to the roller shaft 9A and at its other end to a support 56 fixed in relation to the brake disc or the vehicle chassis. Modifications are possible within the scope of the appended claims .

Claims

CLAIMS 1. A disc brake with self-servo-effect, comprising a brake yoke (15) placed astraddle of a non-axially movable brake disc (1), brake pads (2, 3) in the brake yoke at either side of the brake disc, and means (7-14)' for providing a brake application force - by bringing one of the brake pads into contact with the brake disc - and for controlling the application force and hence the self-servo effect, c h a r a c t e r i z e d by mechanical means (34; 42, 43; 54; 55, 56) for concurrently and positively controlling the application of the brake pads (2, 3) at both sides of the brake disc (1) .

2. A disc brake according to claim 1, comprising: a movable ramp plate (7) connected to a front brake pad (2) for engagement with a brake disc (1) attached to its shaft, a ramp bridge (8; 80), floatingly arranged in relation to the brake disc (1) , means (10-14) for imparting a control movement on the ramp plate (7) , application members (9; 50) between the ramp plate (7) and the ramp bridge (8; 80) for increasing the mutual axial distance between these two members at a relative movement in the tangential direction of the brake disc, and a brake yoke (15), force-transmittingly connected to the ramp bridge (8; 80) and extending to the opposite or rear side of the brake disc (1) , where it is provided with a rear brake pad (3) for braking engagement with the brake disc, wherein the application members (9; 50) are mechanically guided for movements substantially parallel to the brake disc (1) .

3. A disc brake according to claim 2, wherein the application members are rollers (9) movable in ramps (7', 8') in surfaces facing each other of the ramp plate (7) and the ramp bridge (8) .

4. A disc brake according to claim 3, wherein the rollers (9) are guided by planes (34), which are axially fixed in relation to the brake disc (1) .

5. A disc brake according to claim 3, wherein the rollers (9) are guided by notches (42) in a fixed housing (40) for the disc brake.

6. A disc brake according to claims 4 or 5, wherein each roller (9) has a shaft (9A), which at each end is provided with a rotatable journal ring (9B) engaging the planes (34) or the notches (42), respectively.

7. A disc brake according to claim 6, wherein a connecting rod (43) , roller cage or the like connects the shafts (9A) of two rollers (9) .

8. A disc brake according to claim 4 or 5, wherein the planes (34) or notches (42) are shaped to provide desired characteristics for the brake.

9. A disc brake according to claim 8, wherein the notches (42) are arcuate in order to compensate for the greater elasticity in the force transmitting path to the opposite or rear side of the brake disc (1) .

10. A disc brake according to claim 2, wherein the ramps (7', 8') have different inclination angles in order to provide desired characteristics for the brake.

11. A disc brake according to claim 2, wherein substantially rectangular application members (50) are arranged in correspondingly shaped recesses (7", 8") in the ramp plate (7) and the ramp bridge (8), respectively, and have shafts (52) guided by planes (54), which are fixed in relation to the brake disc (1) .

12. A disc brake according to claim 3, wherein the rollers (9) are pivotally connected to link rods (55) , that at their opposite ends are connected to supports (56), which are fixed in relation to the brake disc (1) .