GB2231375A - Vehicle brake self-adjusting arrangements - Google Patents

Abstract

A braking system comprises a first and second unidirectional binding systems. The first 12, 13, Fig. 1 and 76, 77, Fig. 8 extends the linkage between a hydraulic prime mover 10, 74 and the pads or shoes as the friction surfaces wear and the second B, Fig. 1 and 84 Fig. 8 moves the pads or shoes closer to the rotor as the friction surfaces wear. As a result the volume of the hydraulic system remains constant. An associated handbrake arrangement is also described. <IMAGE>

Description

A SEATED VEHIcTs BRAKE .9FTz ADJUSTMENT SYSTEM This invention relates to vehicle brakes that have a stator connected to a chassis, an actuator system that energises and deenergises the brake, a sacrificial friction member (hereinafter called a lining), a rotor that is connected to a wheel, and arranged such that energising the actuator system has the action of bringing the lining into contact with the rotor, the frictional torque produced reacting against the stator. The actuator system consists of a master actuator controlled by the driver, which produces high pressure fluid when it is energised (hereinafter called energising), connected to wheel actuators that use this fluid to force linings into contact with the rotor.

There are a number of brakes of the type described, on the more sophisticated brakes, various types of adjustment devices (either manually operated at servicing intervals or automatically operated throughout the life of the linings) are provided to obviate the necessity of the wheel actuator moving through a stroke equivalent to the worn part of the lining on each energisation of the brake.

An automatic adjustment device is described in European Patent Application Number 87904300.8. The wheel actuator normally consists of a hydraulically operated piston or a wedge or a lever or a cam or a cable which has a potential stroke of the possible lining wear.

Devices are included to ensure that on de-energising the actuator, the lining is positively disengaged from the rotor, the disengagement device being an energy store such as a spring or a gravity operated device. The disengagement energy may be obtained by the rotor running out of a true relationship when the brake components are strained by the motion of the vehicle. Current actuation systems use a variable quantity of fluid which is in contact with the atmosphere and may thereby absorb contaminents. To minimise dangers due to system failure, such actuatipn systems frequently connect wheel brakes in pairs so that failure of one pair of brakes will not make the remainder inoperative.

The present invention has three main objectives, firstly, to restrict the stroke of the master and wheel actuators to that necessary for taking up lining disengagement clearances, plus deflection of mechanical components, plus wear on the linings during a single stop, plus any safety factor thought appropriate (hereinafter called master/wheel actuator stroke); secondly, to permanently seal the fluid in the system; thirdly, to have independent actuator system connections to each wheel. The invention also permits a simple mechanical handbrake to be fitted to a drum or disc brake.

According to the present invention there are at least two unidirectional binding arrangements provided at the wheel; the first of which consists of a first shaft and a device which binds on the shaft such as a washer or a C clip, (hereinafter called a binder), when the brake is energised, and where the shaft and binder arrangement (hereinafter called a ratchet) is directly in the line of action that brings the linings into contact with the rotor, and where a first spring keeps the binder in unidirectional binding contact with the shaft, and has reaction axially along the shaft, and a second spring having force greater than the first spring opposes movement of the shaft through the binder due to this reaction; and, when the brake is de-energised, the binder can move relative to the shaft if the force due to the second spring is overcome.The second unidirectional binding arrangement consists of a second ratchet which does not bind when the brake is energised and is not in the direct line of action that brings the linings into contact with the rotor, and where a third spring keeps a binder in unidirectional binding contact with the second shaft, and has reaction axially along the second shaft, and a fourth spring having force greater than the third spring opposes movement of the second shaft through the binder due to this reaction, and, the binder can move relative to the second shaft if the force due to the fourth spring is overcome, and, where the second shaft is connected to the lining such that there is a limited range of movement between lining and second shaft (this limited movement is usually between .Olmm and lmm) and relates to the disengagement between lining and rotor; and when the brake is de-energised, the second ratchet permits disengagement of the lining from the rotor for the limited movement, and, if the linings are worn, the second ratchet binds and the first shaft advances through the first binder. Both first and second ratchets can only retreat the lining beyond the disengagement distance when both ratchets are manually manipulated at servicing intervals.

The master/wheel actuator stroke is small and there is no increase in total volume of the actuator system throughout the life of the linings, the actuator system can therefore be permanently sealed.

It may be necessary to give a facility for making small volume changes when permanent set of mechanical components takes place. It is convenient to make the master actuator to wheel actuator system independent for each wheel. Fluid pressures in each system may be automatically equalised by energising the master actuators in series, but energising in parallel is not precluded. Automatically adjusting handbrakes can be incorporated acting through the first binder.

In a disc brake, the caliper can be made from a single pressing of high tensile steel plate, and the efficiency of an actuation system will be high due to low caliper flexing across the rotor. The drum brakes shown are leading/trailing units, but the system could be adapted to twin leading, twin trailing, or servo designs.

The following figures have been drawn to show the principles of operation. In the interests of clarity, there are no devices to stop water ingress, or to bleed the sealed actuation systems, or supress noise, and binders are shown at exaggerated angles to shafts, as in practice, binders will have a close fitting centre hole.

The invention will now be described in greater detail with reference to the following figures which are used for the purpose of example only, and where: Figure 1 shows a cross section of a reaction disc brake of the invention.

Figure 2 shows cross section AA of figure 1.

Figure 3 shows an alternative piston/cylinder arrangement to the elastomeric tube arrangement of figures 1 and 2.

Figure 4 shows enlarged cross section BB of figure 1.

Figure 5 shows a cross section of a double sided caliper disc brake with handbrake.

Figure 6 shows the pad backing plate design of figure 5.

Figure 7 shows cross section CC of figure 5.

Figure 8 shows a side view of a drum brake with the rotor removed.

Figure 9 shows cross section DD of figure 10.

Figure 10 shows cross section EE of figure 8.

Figure 11 shows cross section FF of figure 9.

Figure 12 shows an actuation system suitable for use with the brake of figure 8.

Figure 13 shows an actuation system suitable for use with the brake of figures 1 or 5.

Figure 14 shows a master actuator suitable for use with actuator systems of figure 13.

Figure 15 shows a master actuator suitable for use with actuator systems of figure 12.

Figure 16 shows a master actuator suitable for use when the actuator system is assembled and bled when installed on the vehicle.

It will be noted that like reference numbers refer to like components throughout the specification.

Referring to figure 1 which shows a single sided or reaction caliper. Such calipers are well known, and are briefly described as follows:-vehicle mounting points 1 have mounting holes 2, and are not part of caliper bridge 3 which moves in direction X in relation to mounting points 1 as pads 5 and 6 wear. The torque created by the friction of pads 5 and 6 on rotor 4 is transmitted through backplates 7 and 8 to a further mechanical component symbolically shown as torque carrier 9 to mounting points 1.

The invention is suitable for use with all known reaction caliper designs. Pad 6 is pushed into contact with rotor 4 by energising reinforced elastomeric bag 10. The first unidirectional binding device consists of holder 11 surrounded by binder 12, which is loaded against projection 13 on bridge 3 by compression spring 14. Compression spring 15 is stronger than spring 14, reacts against washer 16 and circlip 17, and ensures that binder 12 is in contact with projection 13 when bag 10 is not energised. Bridge 3 transfers the force on lining 6 across rotor 4 to lining 5 so that resultant lateral forces on rotor 4 are zero.

Referring to figure 2, when bag 10 is not energised, holder 11 is kept in contact with backplate 8 by manually attachable compression springs 18 (which are stronger than springs 15) acting on hooks 19.

Projections 20 on holder 11 limit compression of bag 10. Torque created by friction of linings 6 on rotor 4 is taken through backplate 8 onto hypothetical torque carrier 9, and thereby to mounting points 1.

Torque carrier 9 may be in a large number of forms such as slides or pins (not shown) which pass over rotor 4. De-energisation of bag 10 and extension of spring 18 withdraws lining 6 from rotor 4.

Referring to figure 3, this shows an alternative method of using high pressure fluid by replacing bag 10 and holder 11 with piston 20 and holder 21, piston 20 is sealed with seal 22.

Referring to figure 4, the second unidirectional binding shaft 23 is a free fit in holes through plates 7 and 8, the holes may have nylon inserts 24 and 25, to inhibit sticking of shaft 23. Compression spring 26 between washer 27 which abuts on plate 8 and pin 28 normally ensures that plates 7 and 8 do not advance towards rotor 4 unless impelled by bag 10 (figure 1). The free distance between pins 28 and 29 is related to the disengagement of linings 5 and 6 from rotor 4. Binder 30 surrounds shaft 23 and is loaded against projection 31 of insert 25 by spring 32 and reacts against head 33 of shaft 23. On energisation of bag 10 (figure 1), forces in springs 18 and 26 are overcome and linings 5 and 6 move towards rotor 4, and, (if linings 5 and 6 are worn) plate 7 contacts pin 28 and moves shaft 23 relative to binder 30.Deenergisation of bag 10 permits plates 7 and 8 to retreat from rotor 4 until pin 29 is contacted and further retreat is prevented. If linings 5 and 6 have been worn, the second unidirectional binding device and springs 18 advance holder 11 through binder 12 towards rotor 4. If positive retraction of linings 5 and 6 from rotor 4 is required then spring 26 should act directly on plate 7, but this has not been shown.

Referring to figure 5, pads 34 are forced into contact with rotor 35 by bags 36. Bags 36 are hydraulically joined by a connection (not shown) that passes over rotor 35. Holders 37 are surrounded by binders 38 and are loaded against projections 40 of ring 41 by compression springs 42 which react on holder 37.

Energisation of bags 36 forces linings 34 into frictional contact with rotor 35 via holders 37, binders 38, rings 41 and plates 43. Ring 41 is located in plate 43 by semi-sheared recess 44. Compression spring 45 is stronger than spring 42 and reacts against circlip 46, ensuring that edge 47 of holder 38 is in contact with bridge 48 when bag -36 is not energised. Handbrake lever 49 pivots about pin 50 and contacts holder 37 at point 51. Cable 52 passes through bridge 48 and is retained by nipple 53 in slot 54. Outer cable 55 reacts against lever 49 when the handbrake is applied. lever 49 is returned to the neutral position by spring 56. Bridge 48 contains projections 57 which abut plates 43. Mounting points 58 are provided in bridge 48 for attachment to the vehicle chassis.

The operation of the brake is similar for energisation of bag 36 or cable 52, and only energisation of bag 36 will be described. In the reaction caliper of figure 1, the second unidirectional binder was shown at the top of the disc. Such an arrangement would not be ideally suited to the design of figure S which requires the force due to energisation of bag 36 to impinge near the centre of pressure of lining 34. Projection 40 is shown as being near the top of backing plate 43 for easy explanation, however, the best position for projection 40 is in the centre of pressure of linings 34.

Referring to figure 6, recess 44 has location 59 which corresponds to an image location on ring 41 (not shown). Edges 60 and 61 of plate 43 are not aligned in order to facilitate assembly of shaft 62 (figure 7) in slot 63.

Referring to figure 7, the second unidirectional binding device has shaft 62 which is a free fit in holes 64 and 65 through projections 66 and 67 of bridge 48. The holes 64 and 65 may have nylon inserts to inhibit sticking of shaft 62, but this is not shown. Compression spring 68 between projection 67, washer 69 and pin 70 ensures that plate 43 does not advance towards rotor 35 unless impelled by bag 36 (figure 5).- The free distance between projections 66 and 67 is related to the limited disengagement of lining 34 from rotor 35. Tightly wound coils 71 surround shaft 62 and are loaded against projection 67 by spring 68. The unidirectional effect of coils 71 is obtained by ensuring that the force required to move coils 71 relative to shaft 62 is greater than the force due to spring 68 and less than the force due to energisation of bag 36. Shaft 62 is a good fit in slot 63, and the location of ring 41 in recess 44 ensures positive retention. It is advisable to make the main diameter of shaft 62 a greater diameter than the diameter of slot 63 in order to avoid incorrect assembly. In the brake of figure 5, four of the binding arrangements shown in figure 7 would be required.

When bag 36 is energised, forces in spring 45 (figure 5) are overcome, plate 43 and lining 34 move towards rotor 35, and, if the linings are worn, coils 71 contact projection 66, the frictional forces between coils 71 and shaft 62 are overcome, and shaft 62 moves relative to coils 71. On de-energisation of bag 36, spring 68 retreats plate 43 from rotor 35 until coils 71 contact projection 67, further retreat is prevented by the inability of spring 68 to overcome the friction between coils 71 and shaft 62. If linings 34 have been worn, the second unidirectional binding device and springs 45 move binders 38 and rings 41 relative to holders 37.

Referring to figure 8, stator 72 is mounted on a vehicle chassis by mounting holes 73. Hydraulic actuator 74 can expand onto holders 75 which operate through binders 76 and projections 77 on webs 78, (hereinafter called webs 78 as a pair and web 78a or web 78b as single webs) transmitting force through platforms 79 to linings 80 that frictionally contact rotor 81 (part shown). Return springs 82 pull webs 78 and therefore linings 80 away from rotor 81. Webs 78 react on abutment 83 which is fixed to stator 72. Adjuster 84 ensures that linings 80 are maintained within a predetermined distance of rotor 81 throughout their useful life. Hold down device 85 ensures that platforms 79 are slideably in contact with stator 72. Springs 86 keep binders 76 in unidirectional binding contact with projections 77.

Bearings 87 are fixed to stator 72 and holders 75 are thereby kept in alignment with webs 78. Springs 88 return actuator 74 to a minimal position. Adjuster 84 is shown between webs 78, and is supported by pin 90 through web 78a, however, two adjusters, each between a web 78a or web 78b and stator 72 could be provided.

Referring to figure 9, the minimal position of actuator 74 is determined by stops 91 on holders 75 contacting stator abutment 92.

Handbrake lever 93 surrounds extension 94 of stator abutment 92 and is retained by circlip 95.

Referring to figure 10, cable inner 96 is the core of cable outer 97 and passes through slots (not shown) in stator projection 98 and lever 93, and is retained by lever cavity 99. Return spring 100 returns lever projections 101 on lever 93 to a non engaged position when the handbrake is de-energised.

Referring to figure 11, adjustor 84 has shaft 102 which is slotted to pass over web 78a and surrounded by binder 103. Spring 104 keeps binder 103 in unidirectional binding contact with projection 105 on web 78a, and reacts on shaft abutment 106. Shaft 102 passes through rectangular slot 107 in web 78b. Shaft 102 passes through projection 108 on web 78b and has compression spring 109 (which is stronger than spring 104) between projection 108 and abutment 110.

Referring to figures 8,9,10 and 11, the operation is as follows energisation of either actuator 74 or handbrake cable 96 moves linings 80 into contact with rotor 81 and overcomes compression spring 88 and extension springs 82. If the linings 80 are worn, shaft 102 contacts edge 107b of rectangular hole 107, and shaft 102 moves relative to binder 103. De-energisation of either actuator 74 or handbrake cable 96 results in springs 82 retracting webs 78 until edge 107a of hole 107 contacts shaft 102, and binder 103 stops further retraction.

Compression spring 88 continues to compress actuator 74 to minimal position, and, if the linings have been worn, holder 75 moves relative to binder 76. It is convenient to stop the binding of binders 76 and 103 on holders 75 and shaft 102 and allow webs 78 to revert to minimal adjustment position before attempting to remove rotor 81. Slots (not shown) are provided in stator 72 covering possible positions of binders 76 and 103 throughout the life of linings 80. Insertion of a suitable tool (not shown) between webs 78 and binders 76 and 103 will release the binding action, and springs 82 will return linings 80 to minimal position. The slots (not shown) can be stopped with grorrpnets (not shown) when not in use.

Referring to figure 12 which shows a permanently sealed system for transmitting fluid from master actuator 111 to wheel actuator 112 through bundy pipe 113, elastomeric tube 114 and bundy pipe 115; clips 116 ensure sealing. Piston 117 operating in cylinder 118 is sealed by seal 119. Wheel actuator 112 contains two holders 120 sealed by seal 121 and are shown as slotted to fit over webs 78 (figure 8). Springs 122 can be fitted to return holders 120 to a central position. If a handbrake is to be fitted, holders 120 would need an extra projection to accommodate the handbrake lever, but this has not been shown.

Referring to figure 13, master actuator 123 is a reinforced elastomeric tube 124, connected by bundy tube 125 to wheel actuator 126, shown as a blind tube, however, wheel actuator 126 could be a toroid (not shown) or a branched unit (not shown) to make it suitable for use with the double sided caliper of figure 5. Master actuator 123 is connected to cylinder 127 and a piston 128 sealed with seal 129, the piston 128 has screw thread 130 which permits modification of the volume of the sealed system if permanent set of components occurs.

Modification can also be made by using a permanent clip on an extension of tube 124, but this has not been shown. Master/wheel actuators and/or volume adjustment devices can be inter-changed between the examples shown in figures 12 and 13.

Referring to figure 14, which shows a master actuator for four wheels. Driver input at hollow 131 is from a device such as a brake pedal (not shown) or servo mechanism (not shown). Pressure on slide 132 compresses cavities 133 in tubes 134 and the capacity for sending fluid to a wheel actuator (not shown) continues until stops 135 contact stops 136. Cylinder 137 has slots 138 to allow for movement of tubes 134. Circlip 140 retains the assembly in a slightly compressed condition to allow for permanent set of elastomers. Fixing holes 141 may be positioned at any point along cylinders 137. Alternate slides 132 may be made from dielectric material and provided with live contacts 142. Failure of an actuator system results in contact between earthed slide 132 and live contact 142. Circuitry may be provided to indicate failure of the particular system.The gap between slides 132 and contacts 142 is equal to the master/wheel actuator stroke.

Referring to figure 15, pistons 143 operate in slideable cylinders 144, and are returned by compression springs 145. Cylinder 147 has slot 148 to allow for movement of cylinders 144. Pistons 143 may be made from dielectric material and live contacts can be provided at tip 149. Failure of an actuator system results in contact between earthed cylinder 144 and live contact tip 149. Circuitry may be provided to indicate failure of the particular system. Cylinders 144 have projections 146 which permit total possible movement equal to the master/wheel actuator stroke.

Referring to figure 16, which shows a master actuator where it is necessary to bleed and seal the permanently sealed master/wheel actuator systems when the braking system is installed on the vehicle.

Driver input on hollow 131 of piston 150 delivers pressurised fluid from each chamber 151. In the four chamber master actuator shown, failure of any wheel actuator results in loss of one quarter of the system, further loss is prevented by seals 152. Failure of seals 152 may result in the loss of a single system. Circlips 153 prevent collapse or recuperation of pistons 150 beyond ports 154. Total possible movement of pistons 150 is as described for figure 15.

It will be noted that all the hydraulic systems described have been capable of being permanently sealed, however, this is not a mandatory requirement, and open systems could be used.

Claims (9)

Claims:

1. A vehicle braking system of the type where during braking, a master actuator 111, 123 supplies a quantity of fluid under pressure from the brake pedal or servo mechanism mounted on a chassis to the wheels, and there is a wheel actuator 10, 36, 74 that uses the fluid to force linings 5, 6, 34, 80 into frictional contact with a rotor 4, 35, 81 and when not braking, linings 5, 6, 34, 80 retract a small distance from rotor 4, 35, 81 and characterised by:- at least two unidirectional binding systems, the first 12, 38, 76 binding and transmitting force from pressurised fluid to linings 5, 6, 34, 80, and not binding when the fluid is not pressurised; the second 30, 71, 103 not transmitting force from pressurised fluid to linings 5, 6, 34, 80 and binding and permitting linings 5, 6, 34, 80 to retract a small distance from rotor 4, 35, 81, and not binding when linings 5, 6, 34, 80 are forced into frictional contact with rotor 4, 35, 81.

2. A claim according to Claim 1 where the volume of the fluid in the actuation system is constant.

3. A claim according to Claims 1 to 2 where a mechanical handbrake 49, 93 is fitted that acts through the first 38, 76 unidirectional binding system.

4. A claim according to Claims 1 to 3 where each wheel has a separate actuation system which contains fluid that is independent of fluid in any other actuation system.

5. A claim according to Claims 1 to 4 where each actuation system consists of at least one reinforced elastomeric tube 124, 126 joined to at least one bundy pipe.

6. A claim according to Claims 1 to 4 where each actuation system consists of at least one piston 117, 120 operating in an actuator 111, 112 joined to at least one bundy pipe.

7. A claim according to Claims 1 to 6 where provision is made for adjusting the volume of each actuation system 127, 128, 129, 130 due to permanent set of components.

8. A claim according to Claims 1 to 7 where a master actuation system figures 14, 15, 16 in which independent actuation systems figures 12, 13 are arranged in such a manner that failure of any one system figures 12, 13 results in an increased brake pedal or servo mechanism travel of the available pedal travel divided by the number of independent systems.

9. A braking system substantially as described herein with reference to figures 1 to 4 and 5 to 7 and 8 to 11 and 12 and 13 and 14 and 15 and 16 of the accompanying drawings.