GB2442552A

GB2442552A - Disc brake with biased automatic clearance adjustment mechanism

Info

Publication number: GB2442552A
Application number: GB0716588A
Authority: GB
Inventors: Kazuyuki Matsuishi; Yoshiyuki Tanimoto
Original assignee: Nisshinbo Industries Inc; Nisshin Spinning Co Ltd
Current assignee: Nisshinbo Holdings Inc
Priority date: 2006-08-25
Filing date: 2007-08-24
Publication date: 2008-04-09
Anticipated expiration: 2027-08-24
Also published as: JP2008051257A; GB2442552B; GB0716588D0; JP4783695B2

Abstract

A disc brake device with an automatic clearance adjustment device 60 which reduces the dispersion of the brake clearance adjustment and eliminates the ineffective stroke of the lever 30 comprises thrust member 50, casing member 20, lever 30, automatic clearance adjustment device 60, and support member 40. The thrust member 50 is screw-engaging and thrusts a frictional pad 10,11. The lever 30 amplifies an external input and transfers it to the thrust member 50 via a force transferring member 34. The automatic clearance adjustment device 60 comprises an adjuster shaft 61 and a mechanism for transferring the adjuster shaft 61 rotation to an adjustment gear 51a in the thrust member 50, which automatically adjusts clearance between the frictional pad 10,11 and the rotor 1. The disc brake device further comprises a means 80 for biasing the automatic clearance adjuster while the lever 30 is on-stroking. The biasing means 80 may be between the casing member 20 and the automatic clearance adjustment device 60, and may have a C-shaped proximal portion (81, figure 9) with a pair of arms (82, figure 9) to abut the casing member 20, or a W-shaped spring member (90, figure 12) with a pair of arms (92, figure 12) to abut the thrust member 50.

Description

DISC BRAKE DEVICE WITH AN AUTOMATIC CLEARANCE ADJUSTMENT

MECHANISM

Field of the Invention

(0001] The invention relates to a disc brake device with an automatic clearance adjustment mechanism, which facilitates a stable brake clearance between a frictional pad and a rotor.

Background of the Invention

[00021 A disc brake device with an automatic clearance adjustment mechanism is known.

(0003] The automatic clearance adjustment mechanism in the disc brake device is positioned between a tappet assembly, which is slidably fitted in a piston case in an axial direction of a rotor and a lever, which thrusts the tappet assembly and functions to adjust a brake clearance between a frictional pad and the rotor as extending an entire length of the tappet assembly when the rotational amount of the lever exceeds a predetermined value.

4] International Patent Application Publication No. W099/06725 discloses a known disc brake device.

Problems to be Resolved by the Invention (0005] The known disc brake device has plural fitting portions between the piston case and the automatic clearance adjustment device, and play exists in every fitting portion. The play causes an ineffective stroke of the lever during the automatic clearance adjustment operation, which causes dispersion of the brake clearance adjusting range while the lever is on-stroke. The minimum value of the brake clearance is specified for the purpose of preventing dragging due to the over-adjustment of the brake clearance and various problems arising from the dragging. In consideration of a possible result where no brake clearance adjustment is made because of the dispersion of the adjustment due to the play of the fitting portions, the maximum value of the brake clearance is to be designed larger. Although the maximum value of the brake clearance can be set larger so as to eliminate the dragging and the various problems arising from the dragging, the larger value causes another problem of increasing an ineffective stroke of the lever while the lever is on-stroke.

6] A purpose is to resolve the above-identified problems, and an object of the invention is to provide the disc brake device with the automatic clearance adjustment mechanism, which reduces the dispersion of the brake clearance adjusting range and finally to eliminate the ineffective stroke while the lever is on-stroke. Another object of the invention is to provide the disc brake device with the automatic clearance adjustment mechanism, which can be used for conventional disc brake devices.

Summary of the Invention

7] In order to attain the above objects, the disc brake device with an automatic clearance adjustment mechanism, comprises: (a) a thrust member, which has an screw-engaging member structured by screw-engaging an external thread and an internal thread, for thrusting a frictional pad; (b) a casing member for housing said thrust member therein; (c) a lever for amplifying an external input and transferring it to said thrust member via a force transferring member; (d) an automatic clearance adjustment device including (1) an adjuster shaft which rotates with an axis parallel to a rotational axis of the rotor as a fulcrum as converting a lever rotation and (2) an intermediate mechanism which transfers the adjuster shaft rotation to an adjustment gear provided in the thrust member, for automatically adjusting a clearance between the frictional pad and the rotor as detecting over-rotation of the lever and unscrewing the screw-engaging member of the thrust member to extend an entire length thereof; and (e) a support member, in which said casing member supports said automatic clearance adjustment device via said support member; wherein said disc brake device further comprises a biasing means for biasing the automatic clearance adjustment device in a direction which the lever produces a rotational force of said adjuster shaft while said lever is on-stroking.

8] For the condition of plural fitting portions between a piston case and the automatic clearance adjustment device to be constantly same while the lever is not on-stroke, this invention has a biasing means biases the automatic clearance adjustment device in the direction to eliminate the play of the fitting portions while the lever is on-stroke, so that an ineffective stroke of the lever during the automatic clearance adjustment operation becomes shorter, and therefore the difference between the minimum value and the maximum value of the brake clearance adjusting range can be smaller.

9] The disc brake device with the automatic shoe clearance adjustment mechanism has the biasing means set between said casing member and the automatic clearance adjustment device. Also, the disc brake device with the automatic shoe clearance adjustment mechanism has the biasing means which has a C-shaped proximal portion which fits over the automatic clearance adjustment device and a pair of arms which extend in an orthogonal direction from a central portion of the proximal portion and are abuttable against a part of the casing member. Also, the disc brake device with the automatic shoe clearance adjustment mechanism has the biasing means which is a W-shaped spring member, which is comprised of a proximal portion having a curve which is allowed to abut against a part of the automatic clearance adjustment device and a pair of arms having curves which is allowed to abut against the thrust member.

Advantages of the Invention [0010] The invention has the following advantages.

(1) Because of the biasing means to bias the automatic clearance adjustment device in the direction to eliminate the play of the plural fitting portions giving influence on the automatic adjustment function of the brake clearance while the lever is on-stroke, the ineffective stroke of the lever during the automatic clearance adjustment operation and the dispersion of the brake clearance adjusting range becomes smaller, and therefore the difference between the minimum value and the maximum value of the brake clearance adjusting range can be smaller and the ineffective stroke while the lever is on-stroke can be shorter.

(2) The biasing means can simply be added to the existing structure of disc brake devices, thereby facilitating the application of the invention in existing disc brake devices.

(3) The biasing means can be a spring member in a simple shape, and therefore the cost of adding the biasing means is low and assembling the same is simple.

Preferred Embodiment of The Invention [0011] The disc brake device with the automatic clearance adjustment mechanism will be explained below.

Embodiment I [0012] The first embodiment of the invention will be explained with reference to the drawings.

3] As shown in FIGS. I and 2, a disc brake device with an automatic clearance adjustment mechanism, as main components, comprises a torque receiving member 14 which is fixed on a stationary portion of a vehicle as crossing over the periphery of a rotor 1, a caliper assembly 15 which bridges above the rotor I as crossing over the periphery of the rotor 1, pin slide mechanism sections 12, 13 which guide the caliper assembly 15 in a direction parallel to an axis of the rotor 1, an inner pad 10 and an outer pad 11 which are frictionally engageable with both side surfaces of the rotor 1.

4] The caliper assembly 15 consists of a bridge 16 and a later described operation mechanism section 17, and the two are fixed with bolts. The operation mechanism section 17, to thrust the inner pad 10, is structured as housing a brake operation mechanism and a later described adjuster assembly 60 in a housing 18. The brake operation mechanism mainly includes a later described piston assembly 19, a lever 30, and a roller 34 as a force transferring member, and further includes a sheet bearing 35 and a roller bearing 36, both to reduce the sliding resistance of the rotating members.

When using the brake operation mechanism to thrust the inner pad 10 against the rotor 1, because of a reaction force from the inner pad 10, the caliper assembly 15 regresses, and a finger portion I 6a of the bridge 16 of the caliper assembly 15 thrusts the outer pad 11 against the other surface of the rotor 1.

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The floating type disc brake device described above is widely known.

5] The piston assembly 19 will be explained with reference to FIGS. 3 and 4.

6] The piston assembly 19 mainly comprises a pair of tappet assemblies 50, 50 as a thrust member, a piston case 20 as a casing member to house the tappet assemblies 50, 50, and a later described return plate 40 as a support member.

The piston assembly 19 is fixed in the housing 18.

7] The piston case 20 is a molding having a pair of cylindrical portions 22, 22 integrally formed on one surface of a flat substrate 21, where plural installation holes 21a are formed on a circumferential surface of the substrate 21, and a bottomed socket 21 b is formed around a central portion of the substrate 21 between the pair of cylindrical portions 22 and 22. A liner 41 fits in each cylindrical portion 22 so that the tappet assembly 50 freely and smoothly slides.

8] A flat return plate 40 fits over the cylindrical portions 22, 22 at the opening ends thereof. The return plate 40 has circular openings 40a, 40a at both ends thereof, into which the cylindrical portions 22, 22 can be inserted and further has a center opening 40b around a central portion between the openings 40a and 40a through which the adjuster assembly 60 is inserted for the installation therein, and collars 42, 43 fit in the openings 40a, 4Gb respectively. (FIG. 4) [0019] The tappet assembly 50 is a Screw-engagement member where a tappet 51 which has an external thread formed on a peripheral surface of the stem is screw-engaged with a piston 53 which has an internal thread formed on an inner circumferential surface thereof.

0] One end of the tappet 51 has a large diameter portion larger than the other end of the tappet 51, and the peripheral surface of the large diameter portion has a transfer gear 51 a formed therearound while a side end surface of the large diameter portion has a flat end surface 51b which abuts against the roller 34. A bottom end of the bottomed cup-like piston 53 has a flanged piston head 53a which thrusts the inner pad 10.

1] In order to restrict free rotation of the piston 53, the cylinder portion at the inner circumference of the liner 41 inserted in the cylindrical portions 22, 22 and the stem at the periphery of the piston 53 are non-circular, "tri-lobel form". When the transfer gear 51a rotates while the cylindrical portion 22 and the liner 41 are preventing the free rotation of the piston 53, only the tappet 51 rotates1 and therefore the tappet 51 screws and unscrews relative to the piston 53, so that the entire length of the tappet assembly 50 can be adjusted.

2] Referring to FIG. 5, the lever 30, which thrusts the pair of tappet assemblies 50, 50, will be explained next. The lever 30 has a proximal portion 31 with a length sufficient to correspond to the pair of tappet assemblies 50, 50 and an arm 32 extending out from the center of the proximal portion 31 in an orthogonal direction relative to the proximal portion 31.

3] Both ends 31a and 31a of the proximal portion 31 are fan shaped, and the peripheral surfaces 31b, 31b thereof are supported by the roller bearing 36 positioned in the housing 18 to support the lever 30.

4] Each inner circumferential surface 31c of both ends 31a and 31a houses a cylindrical roller 34 therein via a partially circular sheet bearing 35. The roller 34 functions to thrust the end surface 51 b of the tappet 51.

5] An end pin 33 is projected in the proximal portion 31 at a side housing the roller 34 and between the both ends 31a and 31a. The end pin 33 engages with an adjuster shaft 61 of the adjuster assembly 60 constituting the automatic clearance adjustment mechanism.

6] A connecting hole 32a is formed at a free end of the arm 32 on the peripheral surface 31 b side to connect a rod of an air cylinder actuator, which is not in the figures. Because the lever 30 has leverage with both ends 31a and 31a as the fulcrum, an external force applied to the free end of the arm 32 is multiplied and transferred to the pair of tappet assemblies 50, 50.

7] The adjuster assembly 60 willbe explained with reference to FIGS. 3 and 6.

The adjuster assembly 60 is comprised of the adjuster shaft 61 and an intermediate member which transfers the rotation of the adjuster shaft 61 to the transfer gear 51a of the tappet 51. The intermediate member has a shaft sleeve 70 with an intermediate gear 71a to engage with the transfer gear 51a, a drive sleeve 72 rotatably fitting over the shaft sleeve 70, a spiral wrap spring 73 fitting over and extending between both sleeves 70 and 72, a clutch drive sleeve 74 fixed at a top end of the adjuster shaft 61, a multi-plate frictional clutch 75 fitting in the clutch drive sleeve 74, and a coil spring 78 biasing the frictional clutch 75.

8] The adjuster shaft 61 has a yoke 63, which is larger than the stem 62, at one end of the stem 62, and a notched groove 63a is formed at one end 65 of the yoke 63, which is engageable with the end pin 33 of the lever 30. A spline 64, which is press-fittable in the clutch drive sleeve 74, is formed near the other end of the stem 62. The other end 65 of the stem 62 is inserted in and supported at the socket 21b which is formed on the substrate 21 of the piston case 20.

9] The shaft sleeve 70 has a large diameter stem 70b, a medium diameter stem 70c and a small diameter stem 70d. The large diameter stem 70b is inserted in and supported at the opening 43 of the return plate 40. Here, the adjuster shaft 61 freely penetrates through a bore 70a of the shaft sleeve 70, and no rotational force of the adjuster shaft 61 is directly transferred to the shaft sleeve 70. Also, the intermediate gear 71a, formed in the flange 71 at one end of the shaft sleeve 70, engages with the transfer gears 51a, 51a of the pair of tappet assemblies 50 and 50 positioned at both end thereof, thereby transferring the rotational force of the shaft sleeve 70 to the tappets 51, 51.

0] An outer diameter of the drive sleeve 72, which is rotatably fitted over the small diameter stem 70d of the shaft sleeve 70, is designed same as the outer diameter of the medium diameter stem 70c of the shaft sleeve 70. The spiral wrap spring 73 is fitted over and extended between both sleeves 70 and 72, thereby causing a restricting force, when the shaft sleeve 70 rotates in a particular direction, so as to enable the transferring the torque between both sleeves 70 and 72.

1] The coil spring 78 is compressed between disc-like frictional clutch 75 of the multi-plate washers 76, 77 and the return plate 40. The coil spring 78 pre-applies a force so that the frictional clutch 75 is compressed. The frictional clutch 75 is able to transfer the rotational force between the clutch drive sleeve 74, which is fixed on the top end of the adjuster shaft 61, and the drive sleeve 72. The frictional clutch 75 functions such that the rotational force, when a rotational force larger than frictional force is applied to the frictional clutch 75, is not transferred between the clutch drive sleeve 74 and the drive sleeve 72 because the frictional clutch 75 slips. Also, a washer 79 is placed between the frictional clutch 75 and the coil spring 78 as shown in FIG. 6.

2] The disc brake device with the above-described automatic clearance adjustment mechanism has plural fitting portions which can be a cause of the ineffective stroke of the lever during the automatic clearance adjustment operation. The invention is equipped with a biasing means 80 to compulsorily bias the automatic clearance adjustment device in a direction to eliminate the play of the plural fitting portions while the lever is on-stroke.

3] In the example, the biasing means 80 is placed between the adjuster assembly 60 and the pair of cylindrical portions 22 and 22 of the piston case so as to bias the automatic clearance adjustment device in the direction to eliminate the play while the lever is on-stroke.

(0034] The biasing means 80 as shown in FIG. 9 is a spring member comprised of a C-shaped proximal portion 81 attached on the adjuster assembly 60 and the pair of arms 82 and 82 extending in an orthogonal direction of the proximal portion from the intermediate portion of the proximal portion 81.

5] Openings 81a, 81b, into which the stem 62 and the other end 65 of the adjuster shaft 61 can be inserted, are formed at both ends of the proximal portion 81. In the example, the biasing means 80 is installed on the adjuster shaft 61, which is a component of the adjuster assembly 60.

6] The pair of arms 82, 82 of the biasing means 80 are pre-curved in an extending direction from both ends of the proximal portion 81, and a pullback force in a direction of the arrow in FIG. 8 is applied to the proximal portion 81 when the biasing means 80 is positioned so that the pair of arms 82 and 82 abut against the pair of cylindrical portions 22 and 22.

7] The biasing means 80 preferably is made of spring steel; however, the material is not limited to spring steel. The biasing means 80 fits over the adjuster assembly 60, which eliminates the possibility of functionally interfering with the surrounding parts.

8] Regarding the positioning of the biasing means 80, it is important that the biasing means 80 is installed at the side to bias the adjuster assembly 60 in a rotational direction when the lever 30 compulsorily rotates the adjuster shaft 61 while the fever is on-stroke. In other words, it is satisfactory if the biasing means 80 is positioned to compulsorily bias the automatic clearance adjustment device in a direction to eliminate the play of the plural fitting portions while the lever is on-stroke.

9] In the example, as shown in FIG 8, the yoke 63 rotates clockwise white the lever is on-stroke. At this time, the adjuster shaft 61 moves downward in FIG. 8 to reduce the play. In consideration of this structure, the pair of arms 82 and 82 of the biasing means 80 abut against the pair of cylindrical portions 22 and 22 at their lower side as shown in FIG. 8.

0] Also, when the moving direction of the adjuster shaft 61 while the fever is on-stroke is opposite to the direction in the example, the pair of arms 82 and 82 of the biasing means 80 are installed on the pair of cylindrical portions 22 and 22 on their upper side in the figure.

1] Automatic clearance adjustment operation will be explained next. When the lever 30 rotates clockwise from the resting position in FIG 2 along the peripheral surfaces 31 b, 31 b supported by the roller bearings 36, the roller 34 thrusts the end surface 51 b of the tappet 51 constituting the tappet assembly 50, and the pair of tappet assemblies 50 and 50 also thrust the inner pad 10 against the rotor 1.

2] A reaction force generated at this time slides the caliper assembly 15 supported by the respective pin slide mechanism sections 12, 13. As the caliper assembly 15 slides, the finger portion 16a of the caliper assembly 15 thrusts the outer pad 11 against the rotor I to generate the brake force.

3] When the lever 30 rotates clockwise in FIG. 2, the lever 30 thrusts the pair of tappet assemblies 50 and 50, and also the end pin 33 of the lever 30 rotates clockwise in FIG. 2 to rotate the yoke 63 of the adjuster shaft 61. A brake clearance is defined by the backlash between the end pin 33 of the lever 30 and the yoke 63 (gap between the end pin 33 and the notched groove 63a between the end pin 33 of the lever 30 and the yoke 63).

4] The rotation of the adjuster shaft 61 is transferred to the clutch drive sleeve 74, the frictional clutch 75, the drive sleeve 72, the wrap spring 73, the shaft sleeve 70, and the tappet 51 in order.

5] While the lever is on-stroke, if the pads 10, 11 thrust the rotor 1, the frictional resistance at a screw-engagement portion of the tappet 51 and the piston 53, constituting the tappet assembly 50, increases, and therefore the torque to rotate the tappet 51 increases.

6] In a normal state when the amount of lining wear of the pads 10, 11 does not reach the predetermined value, the rotational force of the adjuster shaft 61 is transferred to the tappet 51; however, as stated above, because of the increased torque for the rotation of the tappet 51, the frictional clutch 75 slips at the predetermined toque pre-set with the spring force of the coil spring 78 applying to the frictional clutch 75, and therefore the shaft sleeve 70 with the intermediate gear 71a does not rotate. Hence, the tappet 51 does not rotate, and the entire length of the tappet assembly 50 does not change. Also, as releasing the brake, the spring force of the coil spring 78 applying on the return plate 40 returns the tappet assemblies 50, 50 to an initial position.

7] The automatic clearance adjustment operation when the amount of lining wear of the pads 10, 11 reaches the predetermined value will be explained next.

The rotation of the adjuster shaft 61 is transferred to the clutch drive sleeve 74 and then it is transferred to the drive sleeve 72 via the frictional clutch 75.

The spiral wrap spring 73, which is fitted over and extended between both sleeves 70 and 72, generates the restraining force to transfer the rotation of

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the drive sleeve 72 to the shaft sleeve 70. As a result, when rotating the intermediate gear 71a integrally formed in the shaft sleeve 70, the transfer gears 51 a, 51a of the pair of tappet assemblies 50 and 50 positioned at both end thereof rotate. Only the tappet 51 rotates if the transfer gear 51 a rotates, the entire length of the tappet assembly 50 is adjusted by unscrewing the piston 53 so as to compensate for the amount of lining wear of the pads 10, 11.

(0048] Also, the piston 53 with the non-circular or tri-lobal formed stem fits in the liner 41 having corresponding shape of the inner circumferential cylinder portion, and therefore the piston 53 does not rotate during the brake clearance adjustment operation. If the pads 10, 11 thrust the rotor 1, the torque to rotate the tappet 51 increases because of increasing the frictional resistance at the screw-engagement portion of the tappet assembly 50, and therefore the torque to rotate the shaft sleeve 70 with the intermediate gear 71a dramatically increases. Accordingly, the frictional clutch 75 slips, and no rotation occurs to the shaft sleeve 70 with the intermediate gear 71a.

9] When the brake is released, the lever 30 rotates in the reverse direction. As the lever 30 returns, the end pin 33 of the lever 30 engaged with the yoke 63 of the adjuster shaft 61 reverse-rotates the adjuster shaft 61.

0] The reverse rotation of the clutch drive sleeve 74, integrated with the adjuster shaft 61, releases the restraining force of the wrap spring 73 to disable the toque transfer between the drive sleeve 72 and the shaft sleeve 70. Hence, a clearance adjustment in a reverse direction does not occurs.

1] At the time when the adjuster shaft 61 completes the rotation in the reverse direction, a proper backlash between the yoke 63 of the adjuster shaft 61 and the end pin 33 of the lever 30 is set.

(0052] The invention is such that the biasing means 80, which compulsorily biases the automatic clearance adjustment device in the direction to eliminate the play white the lever is on-stroke, is positioned between the adjuster assembly and the piston case 20. Having the biasing means 80, immediately after consuming the backlash between the yoke 63 and the end pin 33, the clearance adjustment is initiated. Hence, dispersion in the brake clearance adjustment while the lever is on-stroke is removed, and the problem of the ineffective stroke of the lever can be eliminated.

Embodiment 2 [00531 FIGS. 10-12 show an example where an adjuster assembly 160 has a biasing means 90 extended between the transfer gears 51a, 51a and the intermediate gear 71a, which compulsorily biases in the direction to eliminate the play of the fitting portions while the lever is on-stroke.

4] The biasing means 90 of the example, as shown in FIG. 12, is a rounding W-shaped spring member in a band plate. The biasing means 90 has a proximal portion 91, which is formed in an intermediate curvature of the biasing means 90 and is temporarily fitted over the intermediate gear 71a, and arms 92, 92, which are continuously extending from both ends of the proximal portion 91 and are curved to temporarily fit over the transfer gears 51a, 51a.

5] An external form of a yoke 163 of an adjuster shaft 161 is preferably in a circular shape so as to temporarily fit in the proximal portion 91 of the biasing means 90.

6] The biasing means 90 can be assembled by the simple process of fitting the proximal portion 91 thereof over the peripheral surface of the yoke 163 and fitting both sides of the arms 92 and 92 resiliently over the largest dimension of the transfer gears 51a, 51a.

(0057] In the second embodiment, the biasing means 90 is positioned between the transfer gears 51a, 51a of the tappet assembly 50 and the yoke 163 of the adjuster shaft 161, and the adjuster shaft 161 is biased in the predetermined direction (direction of the arrow in the example in FIG. 10).

(0058] The second embodiment can offer the same advantages as the above-described first embodiment, and in addition the shape of the biasing means 90 is simple, thereby providing advantages of low manufacturing cost and easy assembly.

9] If it is structured to generate a clicking sound as the arm 92 of the biasing means 90 is folded inside to roll over teeth of the transfer gear 51a, the amount of adjustment can be understood by the number of clicking sound when manually adjusting the clearance by compulsorily externally rotating the transfer gear 51a, which is convenient.

Brief Description of the Drawings

0] FIG. 1 is a plan view of an example of the disc brake device with the automatic clearance adjustment mechanism; FIG. 2 is a cross section view of FIG. 1; FIG. 3 is an enlarged plan cross section view of a portion of the operation mechanism section of FIG. 1; FIG. 4 is an exploded view of the piston assembly; FIG. 5 is a perspective view of the lever; FIG 6 is an exploded view of the adjuster assembly; FIG. 7 is a bottom view showing a condition where the biasing means is being installed; FIG. 8 is a cross section view of FIG. 7; FIG. 9 is a perspective view of the biasing means; FIG. 10 is an explanatory view of the condition for the installation of the biasing means according to the second embodiment; FIG. 11 is a bottom view of the condition for the installation of the biasing means according to the second embodiment; and FIG. 12 is a perspective view of the biasing means according to the second embodiment.

Claims

1. A disc brake device with an automatic clearance adjustment mechanism, comprising: (a) a thrust member, which has an screw-engaging member structured by screw-engaging an external thread and an internal thread, for thrusting a frictional pad; (b) a casing member for housing said thrust member therein; (C) a lever for amplifying an external input and transferring it to said thrust member via a force transferring member; (d) an automatic clearance adjustment device including (1) an adjuster shaft which rotates with an axis parallel to a rotational axis of the rotor as a fulcrum as converting a lever rotation and (2) an intermediate mechanism which transfers the adjuster shaft rotation to an adjustment gear provided in the thrust member, for automatically adjusting a clearance between the frictional pad and the rotor as detecting over-rotation of the lever and unscrewing the screw-engaging member of the thrust member to extend an entire length thereof; and (e) a support member, in which said casing member supports said automatic clearance adjustment device via said support member; wherein said disc brake device further comprises a biasing means for biasing the automatic clearance adjustment device in a direction which the lever produces a rotational force of said adjuster shaft while said lever is on-stroking.

2. The disc brake device according to claim 1, wherein said biasing means is set between said casing member and said automatic clearance adjustment device.

3. The disc brake device according to claim I or claim 2, wherein said biasing means has a C-shaped proximal portion which fits over said automatic clearance adjustment device and a pair of arms which extend in an orthogonal direction from a central portion of the proximal portion and are abuttable against a part of said casing member.

4. The disc brake device according to claim I or claim 2, wherein said biasing means is a W-shaped spring member, which is comprised of a proximal portion having a curve which is allowed to abut against a part of the automatic clearance adjustment device and a pair of arms having curves which is allowed to abut against the thrust member.