GB2107808A - Disc brake with a pin-sliding caliper - Google Patents

Abstract

The brake has a U-shaped torque member 8 having planar portions 10, 12 on opposite sides of disc rotor 2, a caliper 26 having a first and a second pair of arm portions 62, 80 having a first and a second pair of engagement bores (64), 82 respectively; a first pair of slide pins 40, 42 are fixed to portion 10 of torque member 8 and extend therefrom axially outwardly of rotor 2 into bores (64) and a second pair of slide pins 44, 46 are fixed to the portion 12 and extend therefrom axially outwardly into bores 82. At least one 44 of the second pair of slide pins includes a sleeve 76, a bolt 70 fixed to portion 12 and inserted through the sleeve, and two separate boots 84, 86 of elastic material each of the boots having at one end a thick-walled ring section 88, 90 retained in annular grooves 92, 94. The ring sections are normally kept in contact with the outer surface of the sleeve but are elastically yieldable, upon application of a force to the caliper, in a direction perpendicular to the axis of the sleeve thereby allowing the inner surface of the mating engagement bore 82 to contact the outer surface of the sleeve. As described, all the pins have such an arrangement of sleeve and boots. <IMAGE>

Description

SPECIFICATION Disc brake with a pin-sliding caliper The present invention relates to a disc brake having a pin-sliding caliper, and more particularly to a disc brake wherein a caliper for urging friction pads against opposite sides of a disc rotor is supported by slide pins fixed to and extending from a torque receiving member such that it is slidably movable in a direction parallel to the axis of rotation of the rotor.

Most of such type of disc brakes in the art commonly use a pair of slide pins which are disposed on one side of the disc rotor. When these brakes are used for a medium or large-sized vehicle, however, they are required to have a heavy caliper and consequently slide pins which have an increased length of engagement with the caliper. Usually, the size of wheels of the vehicles is not snlarged in proportion to an increase in weight of the caliper. This fact will cause a disadvantage that the slide pins extend a considerable distance out of the wheel disc.

To overcome the above disadvantage, it has been proposed to support the slide pins by a mounting bracket so that the pins extend over the outer periphery of the disc rotor in order to slidably support the caliper. This arrangement has also a drawback that the slide pins and the adjacent members are subject to direct exposure to heat from the disc rotor thereby causing early deterioration of lubricating grease and dust sealing boots for the slide pins. Another drawback arising from the above arrangement wherein the pins extend over the periphery of the rotor, lies in the requirement for reducing an outside diameter of the rotor.

In light of the above drawbacks, the present inventors developed a disc brake which is disclosed in British patent application No.

81 18845, filed June 18, 1982, entitled "Disc Brakes with a Caliper Supported by Siide Pins".

In the disc brake disclosed in the above application, four slide pins are disposed, two on one side of the disc rotor and the other two on the other side of the same. The two slide pins disposed on the side of the reaction portion of the caliper are adapted to serve as auxiliary slide pins which aid the other slide pins on the side of the cylinder portion in supporting and guiding the caliper. Those auxiliary slide pins each include a sleeve which is covered with a dust sealing boot interposed between the outer surface of the sleeve and the inner surface of the bore through which the sleeve is inserted in a slidable manner.While an intermediate portion of the boot functions as a rubber bushing elastically yieldable in the direction perpendicular to the axis of the sleeve, the rubber bushing is not completely satisfactory in that there is a limitation in the amount of elastic deformation in the said direction because the intermediate portion of the boot, i.e., the rubber bushing is in contact with the sleeve and the mating bore over the entire length of the bushing or the bore. More specifically stated, the intermediate portion of the boot is not sufficiently deformable in the direction along the axis of the sleeve because there is no space within the bore that allows the rubber bushing to be deformed axially of the sleeve as required to permit a sufficient yield of the bushing in the direction perpendicular to the axis of the sleeve when an excessive force is applied thereto.

In the foregoing disc brake, it is almost impossible to completely avoid misalignment of the plural slide pins fixed to a torque receiving member with the mating bores formed in the caliper, which misalignment is caused by errors in the manufacture of the brake. It is also unavoidable that the slide pins are misaligned with respect to the mating bores due to elastic deformation of the torque receiving member, caliper and other parts upon brake application.

Although this misalignment will occur on a disc brake having two slide pins, a disc brake having four slide pins is more likely to suffer such a problem. Further, a misalignment between the slide pins and the mating bores may take place when the caliper frictionally contacting brake pads during brake application is moved relative to the torque receiving member together with the pads which are moved circumferentially of the rotor by a distance equal to a clearance within a pad receiving recess in the torque receiving member.

Consequently, it is required that the inside diameter of the mating bores be greater than the outside diameter of the slide pins by an amount enough to absorb the misalignment arising from the various causes mentioned above. However, the more presence of a clearance between the slide pins and the mating bores will cause the caliper to rattle while a vehicle is running. To avoid such rattling action of the caliper, an intermediate portion of a boot is interposed as a rubber bushing between the slide pins and the inner surface of the bores as disclosed in the previously identified patent application. The rubber bushing of such type, however, is not capable of providing a sufficient yielding to absorb the misalignment discussed above.

Thus, the slide pins disposed on opposite sides of the disc rotor in such type of disc brake suffers a difficulty in achieving a function of supporting and guiding the caliper and another function of permitting a relative movement between the slide pins and the caliper in a direction perpendicular to the axis of the pins.

Accordingly, it is an object of the present invention to provide a disc brake having a pinsliding caliper wherein the caliper is smoothly slidable on, and supported by, slide pins of reduced length which are located so as not to be directly exposed to heat from a disc rotor and which permit the disc rotor to have a comparatively large outside diameter.

Another object of the invention is to provide a disc brake having the above features and wherein the slide pins are adapted to absorb movements of the caliper in a direction perpendicular to the axis of the pins while maintaining a high ability of building or orientating the caliper relative to a torque member of the brake.

According to the present invention, there is provided a disc brake which comprises: (a) a rotatable disc rotor; (b) a pair of friction pads disposed on opposite sides of the disc rotor; (c) a U-shaped torque member including a first and a second planar portion receiving the pair of friction pads respectively slidably in a direction parallel to the axis of rotation of the disc rotor, and a connecting portion connecting the first and second planar portions so as to extend over the outer periphery of the disc rotor; (d) a caliper including a hydraulic cylinder portion facing one of the friction pads, a reaction portion facing the other of the friction pads, a connecting portion connecting the hydraulic cylinder and reaction portions, a first pair of arm portions disposed on the side of the hydraulic cylinder portion and having a first pair of engagement bores, and a second pair of arm portions disposed on the side of the reaction portion and having a second pair of engagement bores; (e) a first pair of slide pins spaced circumferentially of the disc rotor so as to engage the first pair of engagement bores, the first pair of slide pins extending from the first planar portion of the torque member axially outwardly of the rotor and slidably supporting the caliper at its hydraulic cylinder portion; and (f) a second pair of slide pins spaced circumferentially of the disc rotor so as to engage the second pair of engagement bores and to be concentric with the first pair of slide pins, at least one of said second pair of slide pins including a sleeve, a bolt fixed at one end thereof to the second planar portion and inserted through the sleeve, and two separate boots of elastic material covering opposite end portions of the sleeve, said boots each having at one end thereof a thick-walled ring section retained in an annular groove formed in the respective one of the second arm portions adjacent a respective open end of the mating engagement bore, said ring section normally kept in contact with the outer surface of the sleeve, and upon application of a force to the caliper, being elastically yieldable in a direction perpendicular to the axis of the sleeve thereby allowing the inner surface of the mating engagement bore to contact the outer surface of the sleeve.

A preferred form of the disc brake of the invention further comprises at least one retraction spring disposed so as to urge a pair of friction pads in a direction away from each other. This retraction spring is connected at both ends thereof to the friction pads respectively, and its central portion is kept in abutment on the bottom surface of the connecting portion of the caliper so as to urge the caliper and the friction pads in a direction away from each other, whereby the retraction spring serves as an anti-rattie spring for the friction pads and at the same time acts to bear a part of the weight of the caliper when the caliper is located at an upper position of the disc rotor.

In a disc brake constructed according to the invention as described above, the slide pins may have a reduced length of engagement with the engagement bore and thus may be shortened because they are provided on opposite sides of the disc rotor. Another advantage of the present disc brake lies in the possibility of using a disc rotor having an increased outside diameter. This advantage is attributable to the arrangement of the slide pins, i.e., they do not extend over the outer periphery of the disc rotor.

An important advantage of the disc brake of the invention resides in that the second pair of slide pins are capable of moving relative to the caliper in a direction perpendicular to the axis of the pins for absorbing a misalignment between the pins and mating bores. This advantage results from the provision of the two separate boots of elastically yieldable material. This requirement for the perpendicular yielding of a portion of the boot interposed between the sleeve and the mating bore, is not met when the slide pin uses a single boot whose intermediate portion is assigned to act as a rubber bushing.The above arrangement of the second pair of slide pins does not adversely affect the capability of the disc brake of guiding or orientating the caliper relative to the torque member because the second pair of slide pins are adapted such that the thick-wall ring sections of the boots allow the inner surface of the engagement bores to contact the outer surface of the sleeve when an excessive force is applied to the caliper.

The above and other objects, features and advantages of the present invention will become more apparent from the following description of the invention taken in connection with the accompanying drawings in which: Fig. 1 is a plan view of an embodiment of a disc brake in accordance with this invention; Fig. 2 is an elevational view of the embodiment of Fig. 1; Fig. 3 is a longitudinal cross sectional view of a slide pin in the embodiment of Figs. 1 and 2; and Fig. 4 is a longitudinal cross sectional view of another slide pin in the same embodiment.

Referring more particularly to the accompanying drawings, there will be described a preferred embodiment of the present invention.

Referring to Fig. 1 ,there are shown an inner friction pad 4 and an outer friction pad 6 which are disposed on opposite sides of a rotatable disc rotor 2 and supported by a stationary torque member of U-letter shape. The torque member includes a planar portion 10 secured to a nonrotatable member such as a knuckle or an axle column, another planar portion 12 opposite to the planar portion 10 with the disc rotor sandwiched therebetween, and a pair of connecting portions 14, 1 6 connecting both planar portions 10 and 1 2 and extending therebetween over the outer periphery of the disc rotor 2. The planar portions 10, 12 form the two arms of the U-shaped torque member 8, and the connecting portions 14, 1 6 form the base of the same member. The outer friction pad 6 is received within a padaccommodating recess 1 8 formed in the second planar portion 12, as clearly illustrated in Fig. 2, such that the pad is slidably movable in parallel to the axis of rotation of the rotor 2. The inner friction pad 4 is supported in the first planar portion 10 in the same manner as the outer friction pad 6. Thus, the first and second planar portions 10 and 12 slidably support the friction pads 4 and 6, respectively. The inner and cuter friction pads 4 and 6 are biased by a pair of U-shaped retraction or return springs 20 in a direction away from each other. As shown in Figs. 1 and 2, each of the retraction springs 20 includes arm portions engaging the pads 4, 6 at their ends, and a base portion connecting the arm portions and kept in abutment on the bottom surface of a caliper 26 referred to below.Consequently, the retraction springs 20 bias the friction pads 4,6 not only in the direction away from each other axially of the dis rotor 2, but also in the direction radially inwardly of the rotor 2 so that the pads 4, 6 are urged against the bottom surfaces of the padaccommodating recesses 18. in other words, the retraction springs 20 also act as anti-rattle springs in addition to serving as springs for returning the pads 4, 6 to their normal position. The inner and outer friction pads 4 and 6 are also provided with anti-squeal springs 22 and 24, respectively, which are disposed on the outer sides of the pads.

The caliper 26 is disposed so as to straddle the disc rotor 2 and the pads 4, 6. The caliper includes a hydraulic cylinder portion 30 facing the inner friction pad 4 and receiving a pair of pistons 28 in parallel, a reaction portion 32 facing the outer friction pad 6, and a connecting portion 34 connecting the hydraulic cylinder and reaction portion 30 and 32. The caliper 26 further includes a first and a second pair of arm portions 62 and 80: first pair 62 on the side of the hydraulic cylinder portion 30, and the second pair 80 on the side of the reaction portion 32. Upon application of a fluid pressure to the cylinder portion 30, the pair of pistons 28 are axially moved to urge the inner friction pad 4 against one side of the disc rotor 2, and by reaction, the reaction portion 32 is moved to urge the outer friction pad 6 against the other side of the disc rotor 2.To permit the above braking action, the caliper 26 are slidably supported by a first pair of slide pins 40 and 42 on the side of the hydraulic cylinder portion 30, and a second pair of slide pins 44 and 46 on the side of the reaction portion 32, such that the caliper 26 is movable along the axis of rotation of the disc rotor 2.

As illustrated in Fig. 3, the slide pin 40 comprises a bolt 48, a spring washer 50, a plain washer 52 and a sleeve 56. The bolt 48 is provided at its fixed end with an externally threaded portion 58 which is screwed into a tapped hole 60 formed in the first planar portion 10 of the torque member 8, so that the spring washer 50, plain washer 52 and sleeve 56 through which the bolt 50 is inserted in the order of description, are secured to the first planar portion 1 0. The length of the bolt 48 is adapted such that its fixed end will not project beyond the inner surface of the first planar portion 10.The sleeve 56 is partly fitted in an engagement bore 64 formed in one of the first arm portions 62 of the caliper 26 extending from the cylinder portion 30, such that there exists a slight clearance between the outside diameter of the sleeve 56 and the inside diameter of the bore 64. Opposite end portions of the sleeve 56 which are to be located outside the arm portion 62 (bore 64) are covered with separate dust sealing boots 66 and 68 respectively. One end of the boot 66, 68 engages an annular groove formed in the respective end portion of the sleeve 56. The other end of the boot 66, 68 has a ring section 67, 69 of increased wall thickness as compared with the remaining section. The thick-walled ring section which is of elastically yieldable is retained in an annular groove formed in the respective end of the arm portion 62 adjacent a respective open end of the engagement bore 64.These ring sections 67 and 69 normally act to maintain the sleeve 56 in alignment with the axis of the bore 64 while their inner surfaces are kept in contact with the outer surface of the sleeve 56, and at the same time serve as rubber bushings which are elastically yieldable in a direction perpendicular to the axis of the sleeve 56, upon application of a large force to the caliper 26, thereby allowing the inner surface of the engagement bore 64 to contact the outer surface of the sleeve 56. The other of the first pair of slide pins 42 is spaced from the slide pin 40 circumferentially of the disc rotor 2 so as to engage a similar engagement bore formed in the other of the first pair of arm portions 62. The slide pin 42 is constructed in the same manner as the slide pin 40 described above.

Similarly to the slide pin 40, the slide pin 44 which is one of the second pair of slide pins, comprises a bolt 70, a spring washer 72, a plain washer 74 and a sleeve 76. The slide pin 44 is disposed so that it is concentric with the slide pin 40. As s whole, the slide pin 44 is designed to be smaller in size that the slide pin 40, i.e., the diameter and length of the bolt 70 and sleeve 76 are smaller than those of the bolt 48 and sleeve 56 discussed above in association with the slide pin 40. It is also noted that the length of the bolt 70 is selected such that the fixed end screwed into a tapped hole 78 will not project beyond the inner surface of the second planar portion 12, as is the case with the slide pin 40.The sleeve 76 is partly fitted in an engagement bore 82 formed in one of the first pair of arm portions 80 of the caliper 26 extending from the reaction portion 32, such that there exists between the outside diameter of the sleeve 76 and the inside diameter of the bore 82 a clearance which is greater than that of the first pair of slide pins 40, 42 on the side of the hydraulic cylinder portion 30. Put in other words, the first pair of slide pins 40 and 42 serve as main slide pins which chiefly guide, or control orientation of, the caliper 26 while the slide pin 44 serves an an auxiliary slide pin which aids the slide pin 40 in supporting the caliper 26.This arrangement enables the caliper 26 to smoothly slide on the slide pins 40 and 44 even in the presence of some errors in concentricity therebetween, and/or between the engagement bores 64 and 82, whereby the tapped holes 60 and 78, and the bores 64 and 82 may have comparatively loose dimensional tolerances.

Similarly to the sleeve 56 of the slide pins 40, 42, opposite end portions of the sleeve 76 which are to be located outside the arm portion 80 are covered with separate dust sealing boots 84 and 86 of elastic material, respectively, which boots each has an integral ring section 88, 90 of increased wall thickness as compared with the remaining section. This thick-walied ring section 88, 90 acts as a rubber bushing interposed between the arm portion 80 and the slide pin 44.

The ring sections 88 and 90 are retained in annular grooves 92 and 94 respectively formed in the respective ends of the arm portion 80 adjacent the open ends of the bore 82. As previously indicated in connection with boots 66 and 68, the inner surfaces of the ring sections 88 and 90 are normally kept in contact with the outer surfaces of the sleeve 76. Upon application of a large force to the caliper 26, however, the ring sections 88 and 90 are elastically deformable in a direction perpendicular to the axis of the sleeve 76. In this connection, it is noted that the ring sections 88 and 90 are spaced along the sleeve 76 so that there exists an annular space therebetween. The slide pin 46 also disposed on the side of the reaction portion 32 of the caliper 26 is spaced from the slide pin 44 such that the pin 46 is concentric with the slide pin 42 on the opposite side.The slide pin 46 has the same construction as the slide pin 44 shown in Fig. 4, and serve as another auxiliary slide pin.

The disc rotor 2 is rotated in a direction indicated by arrow A in Fig. 2. The connecting portion 16 of the torque member 8 from which a given point of the outer periphery of the disc rotor 2 moves away from the torque member 8 during every rotation of the rotor 2, has a stopper section 96 which is formed so as to face one end surface of the connecting portion 34 of the caliper 26 with a slight air gap therebetween. Upon brake application, the said one surface of the connecting portion 34 will abut on the stopper section 96 which in turn supports the connecting portion 34 thereby preventing the caliper 26 from rotating circumferentially of the disc rotor 2.

In the disc brake of the invention described above, the first and second pairs of slide pins 40, 42, 44 and 46 are all disposed outwardly of the torque member 8 axially of the rotor 2, and thus located away from the rotor 2 whose temperature will be elevated during repeated brake applications, that is, the pins are less likely to be affected by heat transferred from the rotor 2, whereby otherwise possible damage to the boots 66, 68, 84 and 86 and early deterioration of the lubricating grease for the pins due to the heat transfer are effectively avoided.

A very important aspect of the disc brake of the invention resides in the arrangement of the boots 84 and 86 which are spaced axially of the sleeve 76 so that their thick-walled ring sections 88 and 90 retained in the bore 82 in spaced relation with each other are adapted to act as the rubber bushings as previously described. These ring sections contribute to giving the auxiliary slide pins 44 and 46 improved characteristics of aiding the main slide pins 40 and 42 in supporting and guilding the caliper on one hand and permitting, on the other hand, a movement of the caliper in a direction perpendicular to the axis of the pins for increased sliding smoothness thereof.

In the present disc brake, it is also noted that the disc rotor 2 may have an increased outside diameter because the slide pins do not extend over the outer periphery of the rotor, and that the slide pins may be made shorter because the two pairs of slide pins are provided, one pair on one side of the disc rotor and the other pair on the other side.

In addition to the foregoing advantages, the present disc brake has a further advantage that it allows an easy replacement of the friction pads.

More particularly stated, the slide pins 40 and 44 are disposed concentrically with each other.

Consequently, the caliper 26 is rotatable about the slide pins 40 and 44 after removal of the bolts of the slide pins 42 and 46, whereby the pads 4 and 6 may be easily removed from the planar portions 10 and 12.

While there is provided a comparatively large clearance between the slide pin 44, 46 and the engagement bore 82 in the arm portion 80 in order than the slide pins 44 and 46 serve as auxiliary slide pins as discussed above, it is possible that the slide pins 44 and 46 be made smaller in diameter and thus lower in rigidity rather than providing a large clearance for enabling the pins 44 and 46 to act as the auxiliary pins.Although the above embodiment uses the two main slide pins 40 and 42 disposed on the side of the hydraulic cylinder portion 30, it is possible, for example, that the slide pin 42 be adapted to be an auxiliary pin by means of providing a large clearance between the slide pin 42 and the arm portion 62 than the clearance between the slide pin 40 and the arm portion 62 thereby reducing the caliper guiding capability of the slide pin 42 as compared with that of the slide pin 40.

It is appreciated that at least one of the four pins is provided with a sintered metal bushing impregnated with oil which is interposed between the arm portion and the sleeve and between the ends of the boots such that there is left a clearance between the inner surface of the bushing and the outer surface of the sleeve as previously described.

It is understood that other modifications and changes of the disc brake of the invention may be made to those skilled in the art without departing from the scope of the appended claims.

Claims (9)

1. A disc brake which comprises: a rotatable disc rotor; a pair of friction pads disposed on opposite sides of the disc rotor; a U-shaped torque member including a first and a second planar portion receiving said pair of friction pads, respectively, slidably in a direction parallel to an axis of rotation of said disc rotor, and a connecting portion connecting said first and second planar portions so as to extend over the outer periphery of said disc rotor:: a caliper including a hydraulic cylinder portion facing one of said friction pads, a reaction portion facing the other of said friction pads, a connecting portion connecting said hydraulic cylinder portion and said reaction portion, a first pair of arm portions disposed on the side of said hydraulic cylinder portion and having a first pair of engagement bores, and a second pair of arm portions disposed on the side of said reaction portion and having a second pair of engagement bores; a first pair of slide pins spaced circumferentially of the disc rotor so as to engage said first pair of engagement bores, said first pair of slide pins extending from said first planar portion of said torque member axially outwardly of the rotor and slidably supporting said caliper at said hydraulic cylinder portion; and a second pair of slide pins spaced circumferentially of the disc rotor so as to engage said second pair engagement bores and to be concentric with said first pair of slide pins, at least one of said second pair of slide pins including a sleeve, a bolt fixed at one end thereof to said second planar portion and inserted through said sleeve, and two separate boots of elastic material covering opposite end portions of said sleeve, said boots each having at one end thereof a thickwalled ring section retained in an annular groove formed in the respective one of said second arm portions adjacent a respective open end of the mating engagement bore, said ring section normally kept in contact with the outer surface of said sleeve and, upon application of a force to the caliper, being elastically yieldable in a direction perpendicular to the axis of said sleeve thereby allowing the inner surface of the mating engagement bore to contact the outer surface of the sleeve.

2. A disc brake as recited in claim 1, wherein both of said second pair of slide pins each include said sleeve, said bolt and said two separate boots.

3. A disc brake as recited in claim 1, wherein the other end of each of said two separate boots is retained in an annular groove formed in the respective end of said sleeve.

4. A disc brake as recited in claim 1, which further comprises a retraction spring of U-letter shape biasing said pair of friction pads in a direction away from each other axially of said disc rotor, said retraction spring including arm portions engaging at ends thereof said friction pads, and a base portion connecting said arm portions and kept in abutment on the bottom surface of said connecting portion of said caliper such that said retraction spring urges said friction pads radially inwardly of said disc rotor so as to act also as an anti-rattle spring for said friction pads.

5. A disc brake as recited in claim 4, wherein said retraction spring is provided in pair.

6. A disc brake as recited in claim 1, wherein said first pair of slide pins are longer than said second pair of slide pins.

7. A disc brake as recited in claim 6, wherein a clearance between said first pair of slide pins and said first pair of engagement bores is smaller than that between said second pair of slide pins and said second pair of engagement bores.

8. A disc brake as recited in claim 6, wherein both of said second pair of slide pins each include said sleeve, said bolt and said two separate boots.

9. A disc brake substantially as hereinbefore described with reference to any of the Figures of the accompanying drawings.