IT8922096A1 - INTEGRAL MECHANICAL PARKING BRAKE WITH A HYDRAULICALLY OPERATED AUTOMOTIVE DISC BRAKE. - Google Patents

Description

The present invention relates to disc brakes and disc brake systems. Historically, in the United States, the use of disc brakes? was mainly limited to front wheel applications, a typical drum brake system being typically used on rear wheel systems. However, interest in disc brakes on the rear wheels is developing.

The use of disc brakes on the rear wheels requires an adequate and reliable mechanical parking braking system, preferably integral with the disc brake. Such an integrated system preferably includes an adjustment mechanism by which the clearance between the friction pads and the rotor or disc? maintained and automatically adjusted for wear on the friction pads.

According to the present invention,? taught a mechanical parking brake assembly integral with the disc brake mechanism and having automatic wear adjustment characteristics.

The novel adjustment mechanism includes an axial thrust screw having an axial differential pressure acting therethrough. An adjustment nut? received screw on the push screw and d? pivotally fixed to the hydraulic actuation piston so that the adjusting nut? free to rotate with respect to the thrust screw and the piston.

The hydraulic pressure acting on the thrust screw creates opposing forces, the result of which? applied to a resilient mechanical spring. Finch? the hydraulic pressure? less than a predetermined value of approximately 200 psi (14 kg / cm2) for a typical automotive braking system, the resulting hydraulic force acting on the thrust life? insufficient to overcome the given resilient spring force and the thrust screw remains stationary. When the hydraulic piston moves due to the hydraulic actuation of the brake, the adjusting nut is pulled together and rotates relative to the thrust screw thus adjusting. wear of the friction pads. As the resistance between the disc and the friction pads increases, there is a proportional increase in hydraulic pressure. When is the resulting hydraulic force acting on the thrust screw? insufficient to overcome the antagonist mechanical spring, the thrust screw in combination with the adjusting nut translates towards the piston by doing s? that the adjusting nut has to engage the piston with friction, preventing any further advancement of the adjusting nut with respect to the thrust screw, thus placing end of the regulation cycle.

Bench? the adjustment mechanism is taught in conjunction with a mechanical parking brake, it can? as well be adapted to any hydraulic disc brake mechanism.

In the drawings:

Figure 1 is a perspective view of a disc brake assembly according to the present invention;

figure 2? a cross-sectional view taken along line 2-2 of Figure 1 and illustrating the elements of the preferred embodiment;

figure 3? an exploded perspective view of the adjustment elements shown in Figure 2.

Figure 4? an isolated perspective illustration showing the rotor cam plate and the ball bearing race assembly;

figure 5? a sectional view taken along the line 5-5 of Figure 2;

figure 6? an isolated perspective view illustrating structural details of the eccentric pin lever;

figure 7? a cross-sectional view taken along line 7-7 of FIG. 5.

1 illustrates a typical floating caliper disc brake assembly 10. The caliper 11? slidably supported on 12L and 12R pliers guide assemblies. The pins 12L and 12R are fixed to the anchor plate 13 which in turn supports the inner and outer friction pad assemblies 14a and 14bf whereby the braking torque is transmitted directly to the anchor plate 13.

Figures 2 and 3 show a cross-sectional view and an exploded view of the present mechanical parking brake of the combined friction pad wear adjusting mechanism. The caliper includes a piston cylinder bore 21 and a two step cam actuator bore 22a and 22b. Positioned within the hole or chamber 21 for the hydraulic piston there? the hydraulic piston 3? forming a hydraulic seal with the piston bore or chamber 21 by the piston seal 18. The piston 30 includes a three step internal bore including an end bore. 31, a hole 32 for an adjustment nut, and a mounting access hole 33. Assembled within the piston 30 are the adjusting nut 35, the ball bearing assembly 36, the flat washer 34, the wave washer 37 and the lock ring 38.

The adjusting nut 35 and hole 32 are shown as having twenty conjugate conical surfaces, however any other group of conjugate surfaces may be employed as a result. evident following the understanding of the functional relationship between these surfaces as it will be? described below. Pu? it may be desirable, under certain operating conditions, to provide mating teeth or other means of frictional engagement on these mating or mating surfaces.

The thrust screw 40 extends axially from the cam plate 51 by screw engaging the adjusting nut 35. The threads 41 of the thrust screw and the mating threads of the adjusting nut 35 have a pitch such that the nut 35 will translate. rotatably along screw 40 in response to a given force applied to nut 35. For example, yes? a three-start thrusting thread having 10 threads per inch (2.54 cm) was found to be satisfactory. However, it can? any suitable multi-lead high helix thread can be used. A captive anti-rotation element 53 engages the slot 48 in the cam plate 51 thereby constraining rotation of the cam plate 51 and the thrust screw 40. The anti-rotation captive element 53? hydraulically sealed by means of the O-ring 29 and? held in position by the threaded plug member 55 and the spacer 28. Screwed into the thrust screw 40, axially opposite the cam plate 51; the end cap? 42 forming a hydraulic seal with the end hole? 31 by means of the O-ring 44 such that hydraulic actuation pressure acts on the internal surface area of the plug member 42 and atmospheric pressure acts on the external surface area through the atmospheric vent 26.

In the non-applied brake mode (in the rest position), the corrugated washer 37 exerts an axial force outward on the adjusting nut 35, acting through the ball bearing assembly 36, sufficient to force the adjusting nut 35 in engagement with piston 30, how? represented in figure 2.

Positioned between piston hole 21 and actuation hole 22a vi? a spring abutment plate 45 having a central opening 43 through which the thrust screw 40 extends and permits passage of hydraulic flow between the holes 21 and 21a and 22a. The spring abutment plate 45? held in position by the resilient ring 46 and the compression of the conical spring 47 between the cam plate 51 and the spring plate 45.

Within the hole 22a of the cam actuator vi? a rotating ball cam drive mechanism comprising the stationary cam plate 51, the rotating cam plate 50, the ball bearing race assembly 60 and the thrust bearing 57. The rotating cam shaft 56 extends through 11 and forms a hydraulic seal with the hole 22b by means of the 0-ring 49 and engages the lever 19 for actuating the parking brake.

The ball bearing race assembly 60 includes race 62, balls 61 and eccentric pin lever 70. The eccentric lever 70 comprises oppositely extending pins 71 and 72 fixed at ends t? opposite to a swash plate 73. How? better represented in Figures 6 and 7, the hinge pin 74? pivotally received in the notch 64 of race 62 such that pin 71 extends axially outward of race 62 and pin 72 extends within race 62. The ball bearing race assembly 60? positioned between the stationary cam plate 51 and the rotating cam plate 50 such that the track pivot pin 53 received within the pivot hole 54 of the cam plate 51 and the pins 71 and 72 of the eccentric pin lever 70 engage pin hole 58 in stationary cam plate 51 and slot 59 in rotary cam plate 50 respectively thus positioning the balls 61 adjacent their respective cam plate surfaces 52. The cam plates 51 and 50 are both provided with corresponding cam plate surfaces 52.

Mechanical Operation:

To activate the mechanical parking brake feature, the mechanical actuation lever 19? induced to rotate by the action of the brake cable 17. Thus, the rotatable cam plate 50 rotates causing axial translation of the stationary cam plate 51, which results in an axial force being applied to the thrust screw 40. When is the axial force? sufficient to compress the conical spring 47, the thrust screw 40 translates axially towards the rotor 15, thus forcing adjusting nut 35 abutting engagement with hydraulic piston 30 and urging piston 30 into abutment contact with internal friction pad assembly 14a; the reaction force acting on the pincer 11 causes the pincer to translate in an inward direction, thus stressing the outer branch 16 of the caliper in abutment contact with the assembly of outer friction pads 14b. Thus both the inner and outer friction pad assemblies 14a and 14b are induced to frictionally engage the rotor 15.

Upon release of the mechanical parking brake, the mechanical actuation lever 19? induced to return to its non-applied position, thus allowing? to the energy stored within the conical spring 47, by compressing it during the application of the mechanical brake, to cause the push screw 40, the adjusting nut 35, the piston 30 and the friction pad assembly 14a to retract.

As the rotatable cam 50 rotates relative to the stationary cam 51, the track 62 follows ball tracking 61 by the pivotal action of the swash plate 73 about the pivot pin 74. the lever 70 with eccentric pins does not fulfill any necessary purpose during the mechanical actuation of the brake, its usefulness? result? evident during the hydraulic actuation of the brake, how will it be? described below.

Hydraulic Operation:

Hydraulic fluid and hydraulic actuation pressure are supplied via the master cylinder (not shown) of the vehicle to the inlet port 24 thus pressurizing. hydraulically the combined volume of the bore or chamber 21 per piston and bore or chamber 22a and 22b of the mechanical actuator. 11 hole d? extremity 31? also pressurized by the flow of hydraulic fluid at the adjusting nut 35 through the axial passages 39 in the piston 30. When? hydraulically operated, the piston 30 is biased towards the rotor 15 so as to cause frictional engagement between the friction pad assemblies 14a and 14b and the rotor 15. When the piston 30 translates towards the rotor 15, beyond the clearance or perative between the adjusting nut 35 and the thrust screw threads 41, separation occurs between the conical portion of the adjusting nut 35 and the hole 32 due to compression of the wave washer 37. When sufficient separation occurs eliminating engagement of friction between the adjusting nut 35 and the hole 32, a condition that derives from the frictional wear of the friction pad assembly 14a, the energy stored in the corrugated washer 37, due to its compression, will apply. an outward axial force on the adjusting nut 35 acting through the ball bearing assembly 36 causing outward rotational translation of the adjusting nut 35 along the thrust screw 40 until the adjustment nut 35 is not? reported to engage in friction with the hole 32 by adjusting cos? the axial position of the hydraulic piston 30 relative to the thrust screw 40 for the wear of the friction pad assemblies 14a and 14b.

During the initiation of the hydraulic brake actuation, the cam plate 51 and the push screw 40 are fixed in place, how? shown in Figure 2, by the action of the conical spring 47 overcoming the differential hydraulic pressure acting on the cam plate 51. However, as the hydraulic actuation pressure continues to increase (generally above 200 psi or 14 kg / cm2), the resulting outward axial force acting on the cross-sectional area of the end plug member? 42 superer? the force of the conical spring 47 thus causing the cam plate 51, the thrust screw 40 and the adjusting nut to translate axially outwards thus forcing the adjusting nut 35 into firm frictional contact with the hole 32 in the piston 30 preventing outward rotational translation of the adjusting nut 35 relative to the thrust screw 40. prevents over-adjustment of the piston 30 due to bending of the caliper and compression of the friction material of the friction pad assemblies 14a and 14b.

Will you understand? what under hydraulic brake actuation like me? been described immediately above, the cam plate 51 between sler? axially outwards and will separate? from the cam plate 50. In this condition, the eccentric pin lever 70 acts to maintain the orientation of the ball bearing race assembly 60 relative to the cam plate 50 and the cam plate 51. When are the cam plates 50 and 51 separated and the cam plate 50? made to rotate towards the cam plate 51, the rotational action of the eccentric pin lever 70 'around 74 causes circumferential translation of the pivot pin 74, thus doing so. to rotate the ball bearing race assembly 60 in proportion to the angular rotation of the cam plate 50; to maintain the angular displacement of the balls 61 relative to the surface 52 of the cam plate.

Brake Maintenance:

During maintenance of the brake can? it may be necessary to push the drive piston 30 back into the chamber bore 21 to separate the friction pad assembly 14a from the rotor 15 to a sufficient degree to remove the caliper 11. There? ? obtained by disengaging the anti-rotation captive element 53 from the cam plate 51 and rotating the mechanical actuation lever 19 clockwise, thus determining? retraction of the adjustment nut 35 and thus allowing? the push back of the piston 30. The captive anti-rotation element 53? disengaged from the cam plate 51 by removing the threaded plug 55 and the spacer 58 a ci? following the replacement of the cap 55 and the hydraulic actuation of the brake; the hydraulic pressure within the hole 22a will disengage? then the captive member 53 from the cam plate 51 without opening the hydraulic system to atmosphere.

It should be borne in mind that the foregoing embodiments are those preferred by the inventor. Various changes and modifications can be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (10)

CLAIMS 1. Automatic adjustment mechanism for a caliper disc brake assembly having first and second caliper legs, said first leg defining a cylinder, a hydraulically operated piston slidably received and sealed within said cylinder, means for electrically pressurizing said cylinder. cylinder so as to cause axial displacement towards the outside of said piston with respect to said first branch of said caliper and the activation of said brake, said adjustment mechanism comprising: adjustment screw means coaxial with said piston, said adjustment screw means being axially movable with respect to said branch of the caliper and including one end connected to said first branch of the caliper and exposed to hydraulic pressure in said cylinder, and in circumventing one end opposite thread extending from said cylinder into a cavity extending axially formed in the extremity? internal of said piston and having an end surface? facing outwardly exposed to atmospheric pressure, thereby subjecting said adjusting screw means to a resulting axial outwardly directed hydraulic force proportional to the hydraulic pressure in said cylinder; nut means coaxial with and screw engaging said end? opposite thread of said adjusting screw means, said nut means being axially movable along said adjusting screw means to vary the deactivated position of said piston relative to said first branch of the calliper, thus adjusting the brake; compression spring means for exerting a predetermined outward axial force on said nut means relative to said piston; friction means interposed between said nut means and said piston means, said friction means being operable in a first condition in which the frictional engagement between said nut means and said piston? such that the axial force exerted on said nut means by said spring means? sufficient to cause rotation of said nut means to axially advance said nut means along said adjusting screw means for adjusting the brake, and a second condition in which between said nut means and said piston there is sufficient frictional engagement so that the axial force exerted on said nut means by said spring means does not rotate and advance said nut axially and do not regulate the brake; And said screw means d? regulation being sensitive to hydraulic pressure within said cylinder which is less than or equal to a quantity? predetermined to operate said friction means in said first condition after initial hydraulic activation and outward displacement of said piston, being sensitive to hydraulic pressure within said cylinder greater than said quantity. predetermined to operate said friction means in said second condition. 2. The automatic adjusting mechanism of claim 1 wherein said compression spring means is first spring means including second spring means for exerting a second axial spring force inward on said adjusting screw means relative to said first branch of the gripper, said second spring force on said adjusting screw means being greater than the resulting opposite hydraulic force on said adjusting screw means when the hydraulic pressure in said cylinder? less than or equal to this quantity? predetermined for urging said adjusting screw means in an inward direction to maintain said friction means in said first condition and permit adjustment of the brake, and wherein the resulting hydraulic force opposed on said adjusting screw means ? greater than said second spring force when the hydraulic pressure in said cylinder? higher than that quantity? predetermined for urging said adjustment screw means in an outward direction to maintain said friction means in said second condition and prevent adjustment of the brake. 3. Automatic adjustment mechanism according to claim 1, wherein the end? external of said adjusting screw means slidably and sealingly engages an end portion? external of said cavity. 4. An automatic adjusting mechanism according to claim 1 including bearing support means between said spring means and said nut means for permitting free rotation of said nut means relative to said piston. 5. An automatic adjustment mechanism according to claim 1, wherein said one end? of said adjustment screw means *? connected to said first branch of the caliper by mechanically operated cam means for mechanically biasing said adjusting screw means, said nut means and said piston in an axial outward direction to mechanically actuate the brake. 6. The automatic adjustment mechanism of claim 5 wherein said cam means is a rotating ball cam drive mechanism including a first cam plate attached to the end. of said adjusting screw means and a second opposing cam plate axially fixed relative to said first branch of the caliper, each cam plate having a multiple t? of corresponding ball ramp surfaces in opposite directions, a corresponding number of balls positioned between and received within said ball ramp surfaces whereby rotation of said first cam plate causes said balls to roll along said ball surfaces. ramp for spheres so as to cause axial separation of said cam plates of a quantity? proportional to the annular rotation of said first cam plate, track means positioned between said first and second cam plates fixing the orientation of said balls to each other, said track means including crank means communicating with said first and second cam plates whereby the rotation of said first cam plate with respect to said second cam plate causes said crank means to correspondingly position said track means in such a way that said balls roll along said ramps for balls according to a predetermined path. 7. An automatic adjustment mechanism according to claim 6 including means for preventing rotation of said first cam plate with respect to said first leg of the gripper and means for rotatably supporting said second cam plate with respect to said first leg of the gripper. 8. The automatic adjustment mechanism of claim 7 including a shaft portion secured to the inner side of said second cam plate and extending therethrough and rotatably supported within a hole formed in the end. of said first branch of the caliper, and sealing means surrounding and sealingly engaging said bore, both said first and second cam plates being positioned within said cylinder and being exposed to any hydraulic pressure therein. 9. The automatic adjustment mechanism of claim 7 wherein said means for preventing rotation of said first cam plate includes an axially extending groove formed in the outer periphery of said first cam plate, and a removable pin having a relatively fixed outer portion to said first branch of the gripper is an internal portion which extends inwards in said groove. 10. In a mechanically operated brake assembly having a rotating ball cam drive mechanism including a first cam plate and a second opposed cam plate, each cam plate having a plurality of cams. of corresponding ball ramp surfaces in opposite directions, a corresponding number of balls positioned between and received within said ball ramp surfaces whereby rotation in said first cam plate causes said balls to roll along said surfaces ramp for the balls so as to cause axial separation of said cam plates by a quantity? proportional to the angular rotation of said first cam plate, the improvement comprising track means positioned between said first and second cam plates securing the annular orientation of said balls to each other, said track means including crank means communicating with said first and second cam plates whereby the rotation of said first cam plate relative to said second cam plate causes said crank means to correspondingly position said track means in such a way that said balls roll along said ramps for spheres on a predetermined path.