Clearance self-adjusting drum brake

Abstract

The present invention relates to a clearance self-adjusting drum brake, comprising a brake base plate, brake shoes are symmetrically arranged on both sides of the front end surface of the brake base plate, a chamber is extended from the front end surface of the brake base plate located at the gap between the upper parts of the two brake shoes, and a camshaft is installed in the chamber; a cam is installed at the end of the camshaft located in the chamber, and a clearance compensation mechanism is installed on the side of the cam in cooperation, and both ends of the clearance compensation mechanism extend out of the chamber and the ends are respectively clamped with the corresponding upper parts of the brake shoes; a clearance adjustment mechanism is meshed and installed on the clearance compensation mechanism located inside the chamber, and the clearance adjustment mechanism is clamped with the camshaft; an external force drives the camshaft to rotate, and the cam at its end simultaneously applies external tension to the brake shoe through the clearance compensation mechanism to achieve braking; when the braking clearance is large, the camshaft drives the clearance compensation mechanism to be axially lengthened through the clearance adjustment mechanism, thereby reducing the braking clearance; the present invention has a compact structure and a reasonable layout, the clearance compensation mechanism directly acts on the brake shoe, has good stability, and is greatly convenient for maintenance and adjustment.

Description

Technical Field

[0001] The invention relates to the technical field of drum brakes, in particular to a clearance self-adjusting drum brake. Background Art

[0002] The commercial vehicle market has been developing and changing rapidly under the influence of relevant regulations and policies. The wheel-end brakes in the braking system mainly include drum brakes and disc brakes. The market share of disc brakes has been increasing year by year due to their unique advantages, but drum brakes still occupy a dominant position in the market. According to regulatory requirements, "brakes should have wear compensation devices" to automatically compensate for the wear of the friction pair to ensure the stability of the brake clearance; the clearance self-adjusting mechanism of the pneumatic drum brake is mainly the adjustment arm self-adjusting mechanism and the wedge self-adjusting mechanism.

[0003] The adjustment position of the self-adjusting mechanism of the adjusting arm is placed on the outside of the brake. The leading and trailing brake shoes are acted on respectively through the camshaft. The clearance adjustment effect is greatly affected by the rigid deformation of the camshaft and the symmetrical synchronous transmission of the cam, and high requirements are placed on the rigidity and symmetry accuracy of the camshaft. This clearance adjustment method is prone to cause clearance instability or the risk of deviation.

[0004] Although the wedge-type brake clearance adjustment mechanism is placed at the shoe end, its clearance adjustment position moves as the brake shoe rotates. The mechanism adjustment operation is cumbersome, and there are inconveniences in clearance adjustment, which is not convenient for subsequent market replacement and maintenance. Summary of the invention

[0005] In view of the shortcomings of the above-mentioned existing production technology, the applicant provides a clearance self-adjusting drum brake with a reasonable structure, so that the clearance self-adjusting compensation mechanism is built into the brake and directly acts on the shoe end, which has high stability and greatly facilitates subsequent maintenance and adjustment in the market.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A clearance self-adjusting drum brake comprises a brake base plate, arc-shaped brake shoes are symmetrically arranged on both sides of the front end surface of the brake base plate, a chamber is extended from the front end surface of the brake base plate at the gap between the upper parts of the two brake shoes, and a camshaft is installed in the chamber; the camshaft extends from the rear end surface of the brake base plate into the chamber, a cam is installed at the end head of the camshaft located in the chamber, a clearance compensation mechanism is installed on the side of the cam, both ends of the clearance compensation mechanism extend out of the chamber, and both ends of the clearance compensation mechanism located outside the chamber are respectively clamped with the corresponding upper parts of the brake shoes; a clearance adjustment mechanism is meshed and installed on the clearance compensation mechanism located inside the chamber, and the clearance adjustment mechanism is clamped with the camshaft.

[0008] As a further improvement of the above technical solution:

[0009] The upper parts of the two brake shoes are interconnected through a large spring, and the lower parts of the two brake shoes are interconnected through a small spring; shoe shafts are symmetrically installed on the brake bottom plate located at the gap between the lower parts of the two brake shoes, and the lower end of a single brake shoe is clamped with the corresponding shoe shaft.

[0010] The rear end face of the brake base plate is fixedly provided with a dust cover, and the flanges at the edge of the dust cover enclose the brake shoes on both sides; an air chamber bracket is installed through the dust cover from back to front, and the front end face of the air chamber bracket is fixedly provided with the brake base plate; the camshaft passes through the air chamber bracket front to back, and an adjusting arm is installed on the camshaft located outside the rear end head of the air chamber bracket; and multiple friction plates are installed on the outer arc surface of a single brake shoe.

[0011] The structure of the clearance adjustment mechanism is as follows: it comprises an upper tooth seat and a lower tooth seat which are fixedly mounted in cooperation with each other, and a rotating shaft is installed through the upper tooth seat and the lower tooth seat in sequence from top to bottom, and a transmission wheel is mounted on the rotating shaft above the upper tooth seat; a dial sleeve is mounted on the clearance of the rotating shaft above the transmission wheel, and an adjusting sleeve is mounted on the inner wall surface of the dial sleeve through a one-way bearing, the adjusting sleeve is mounted on the rotating shaft, the upper part of the adjusting sleeve passes through the dial sleeve upward, and a cover cap is clamped on the rotating shaft above the adjusting sleeve; a tooth plate group is installed between the cover cap and the adjusting sleeve; a supporting shaft is jointly installed on the circumferential wall surfaces of the upper tooth seat and the lower tooth seat, and a driven wheel is installed on the end head of the supporting shaft located inside the upper tooth seat and the lower tooth seat, and the driven wheel is meshed and matched with the bevel teeth of the transmission wheel; the outer wall surface of the dial sleeve is clamped with the camshaft, and the bevel teeth of the driven wheel pass through the bottom surface of the lower tooth seat downward, and the driven wheel located at the bottom of the lower tooth seat is meshed with the clearance compensation mechanism.

[0012] A spring is installed between the adjustment sleeve and the gear plate group. The gear plate group includes outer gear plates and inner gear plates stacked at intervals, and friction transmission is performed between adjacent inner gear plates and outer gear plates. The inner gear plates are clamped with the inner tooth grooves of the adjustment sleeve through the inner teeth, and the outer gear plates are clamped with the outer tooth grooves of the cover cap through the outer teeth. Retaining rings are respectively clamped at both ends of the rotating shaft located above the cover cap and below the lower gear seat. The top end of the rotating shaft extends backwards to the brake base plate.

[0013] The circumferential wall surface of the dial sleeve is provided with a dial hole, the circumferential wall of the camshaft is provided with a pin hole, a pin shaft is fixed in the pin hole, and the end of the pin shaft extends into the dial hole; the size of the dial hole along the circumferential direction of the dial sleeve is larger than the size of the pin shaft.

[0014] A gasket is installed between the bottom surface of the dial sleeve and the top surface of the upper gear seat; the gasket includes a superimposed flat gasket and a butterfly gasket.

[0015] The structure of the clearance compensation mechanism is as follows: it includes a limit plate fixed to the front end of the chamber, a rotating shaft is rotatably installed on the inner side of the limit plate, the axial direction of the rotating shaft is perpendicular to the axial direction of the camshaft, and synchronous wheels are respectively mounted on both ends of the rotating shaft; a single synchronous wheel is meshed with a piston cylinder, the two piston cylinders are arranged at intervals and their axial directions are located on the same straight line; the ends of the two piston cylinders facing each other are respectively clamped with piston heads via retaining springs, and the ends of the two piston cylinders facing each other are respectively threaded with screws; the opposite surfaces of the two piston heads are in contact with the cam in common, the outer ends of the two screws extend to the outside of the chamber respectively, and the two outer ends of the screws are clamped with corresponding brake shoes.

[0016] The inner side surface of the limit plate extends inward to form parallel lugs, and a through hole is formed through the two lugs. The rotating shaft passes through the two lugs through the through hole, and the two ends of the rotating shaft outside the two lugs are respectively equipped with synchronous wheels; a protrusion extends from the inner end of each lug, and a groove is formed along the axial direction on the circumferential surface of the piston head outside the piston cylinder, and the protrusion is accommodated in the groove; a convex block is extended inward along the axial direction on the inner side surfaces facing each other of the piston head, and the groove is located on the convex block.

[0017] The structure of the brake base plate is as follows: it includes a plate body, a chamber is extended forward from the upper end of the front side surface of the plate body, a main through hole is opened through the chamber front and back, a transverse hole is opened through the chamber left and right, and a side hole connected with the transverse hole is also opened in the chamber located on the side of the main through hole, and the axial direction of the side hole is parallel to the main through hole; a boss is extended forward from the lower end of the front side surface of the plate body, and axial holes are opened in parallel through the boss front and back.

[0018] The beneficial effects of the present invention are as follows:

[0019] The invention has a compact and reasonable structure and is easy to operate. The camshaft is driven to rotate by the adjusting arm, and the cam at its end simultaneously applies external tension to the brake shoe through the clearance compensation mechanism to achieve braking. When the brake clearance is large, the pin shaft in the pin hole on the side wall of the camshaft applies circumferential rotational force to the clearance adjustment mechanism, and the clearance adjustment mechanism works, and the clearance compensation mechanism meshed with it is driven by the driven wheel to work, so that the clearance compensation mechanism is axially lengthened, thereby reducing the brake clearance on the outer side surfaces of the brake shoes on both sides, and achieving self-adjustment of the brake clearance, with good stability and reliability. The clearance compensation mechanism directly acts on the brake shoe end and simultaneously applies force to the leading shoe and the trailing shoe, effectively ensuring the synchronization of the leading shoe and the trailing shoe. The rotating shaft of the clearance adjustment mechanism extends backward from the brake bottom plate, which greatly facilitates the subsequent market to adjust the brake clearance through the rotating shaft, and is easy to operate.

[0020] The present invention also includes the following advantages:

[0021] The pin in the pin hole on the side wall of the camshaft applies a circumferential external force to the dial sleeve in the clearance adjustment mechanism. The dial sleeve rotates, and drives the rotating shaft and the transmission wheel to rotate after passing through the one-way bearing, the adjustment sleeve, the gear set, and the cap. The driven wheel rotates accordingly and then drives a piston cylinder of the clearance compensation mechanism to rotate. The screw connected with the piston cylinder threadedly rotates out axially due to the circumferential limit of the corresponding brake shoe. Synchronously, the piston cylinder drives another piston cylinder to rotate synchronously after passing through the meshing synchronous wheel, the rotating shaft, and another synchronous wheel, so that the other screw is rotated out synchronously, thereby realizing synchronous compensation of the brake clearance of the brake shoes on both sides with good consistency.

[0022] The clearance adjustment mechanism and the clearance compensation mechanism are both arranged in the chamber on the upper part of the brake bottom plate, with a compact structure and reasonable layout, which helps the clearance compensation mechanism to directly act on the brake shoe end;

[0023] The cam of the camshaft reciprocates within a preset rotation range. The presence of a one-way bearing between the dial sleeve and the adjustment sleeve in the clearance adjustment mechanism helps to achieve one-way compensation. At the same time, the cam does not need to expand the reciprocating stroke due to clearance compensation, effectively ensuring the stability of braking. The clearance adjustment mechanism compensates and adjusts the braking clearance in time to ensure the stability of the braking clearance, and the overload protection and anti-damping of the clearance adjustment mechanism further ensure the working stability of the drum brake. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the structure of the present invention.

[0025] Figure 2 for Figure 1 Exploded diagram.

[0026] Figure 3 It is a schematic diagram of the installation between the camshaft and the clearance compensation mechanism and the clearance adjustment mechanism of the present invention.

[0027] Figure 4 for Figure 3 A partial enlarged view of part A in the middle.

[0028] Figure 5 It is a structural schematic diagram of the gap adjustment mechanism of the present invention.

[0029] Figure 6 It is an exploded view of the gap adjustment mechanism of the present invention (spring omitted).

[0030] Figure 7 for Figure 6 A partial enlarged view of part B in the middle.

[0031] Figure 8 It is a schematic diagram of the installation between the adjusting sleeve, the gear set and the cover cap of the present invention.

[0032] Fig. 9It is a structural schematic diagram of the gap compensation mechanism of the present invention.

[0033] Fig.10 It is an exploded view of the gap compensation mechanism of the present invention.

[0034] Fig.11 It is a schematic diagram of the installation of the limit plate and the piston head of the present invention.

[0035] Fig.12 It is a structural schematic diagram of the brake base plate of the present invention.

[0036] Among them: 1. Brake base plate; 2. Brake shoe; 3. Clearance compensation mechanism; 4. Clearance adjustment mechanism; 5. Air chamber bracket; 6. Dust cover; 7. Camshaft; 8. Adjustment arm; 9. Friction plate; 10. Large spring; 11. Small spring; 12. Shoe shaft;

[0037] 101, plate body; 102, chamber; 103, side hole; 104, main through hole; 105, transverse hole; 106, boss; 107, shaft hole;

[0038] 31. limit plate; 32. lug; 33. rotating shaft; 34. synchronous wheel; 35. screw rod; 36. piston cylinder; 37. piston head; 321. protrusion; 371. groove; 372. bump;

[0039] 401, lower gear seat; 402, upper gear seat; 403, driving wheel; 404, gasket; 405, adjustment sleeve; 406, spring; 407, adjustment sleeve; 408, gear piece group; 409, cap; 410, driven wheel; 411, rotating shaft; 412, supporting shaft; 413, retaining ring; 414, one-way bearing; 4051, adjustment hole; 4071, inner tooth groove; 4081, outer tooth piece; 4082, inner tooth piece; 4091, outer tooth groove;

[0040] 71. Cam; 72. Pin hole. DETAILED DESCRIPTION

[0041] The specific implementation of the present invention will be described below in conjunction with the accompanying drawings.

[0042] like Figure 1 , Figure 2 and Figure 3As shown, the clearance self-adjusting drum brake of this embodiment includes a brake base plate 1, arc-shaped brake shoes 2 are symmetrically arranged on both sides of the front end surface of the brake base plate 1, a chamber 102 is extended from the front end surface of the brake base plate 1 at the upper gap between the two brake shoes 2, and a camshaft 7 is installed in the chamber 102; the camshaft 7 extends from the rear end surface of the brake base plate 1 into the chamber 102, and a cam 71 is installed at the end of the camshaft 7 located in the chamber 102, and a clearance compensation mechanism 3 is installed on the side of the cam 71, and both ends of the clearance compensation mechanism 3 extend out of the chamber 102, and both ends of the clearance compensation mechanism 3 located outside the chamber 102 are respectively clamped with the corresponding upper parts of the brake shoes 2; a clearance adjustment mechanism 4 is meshingly installed on the clearance compensation mechanism 3 located inside the chamber 102, and the clearance adjustment mechanism 4 is clamped with the camshaft 7.

[0043] The camshaft 7 rotates, and the cam 71 at its end simultaneously applies external tension to the brake shoe 2 through the clearance compensation mechanism 3 to achieve braking; when the braking clearance is large, the pin shaft in the pin hole 72 on the side wall of the camshaft 7 applies circumferential rotational force to the clearance adjustment mechanism 4, and the clearance adjustment mechanism 4 works, and the clearance compensation mechanism 3 engaged with it is driven to work through the driven wheel 410, so that the clearance compensation mechanism 3 is axially lengthened, thereby reducing the braking clearance on the outer side surfaces of the brake shoes 2 on both sides, and achieving self-adjustment of the braking clearance; the clearance compensation mechanism 3 directly acts on the end of the brake shoe 2, and simultaneously applies force to the leading and following shoes, effectively ensuring the synchronization of the leading and following shoes; the clearance adjustment mechanism 4 and the clearance compensation mechanism 3 are both arranged in the chamber 102 on the upper part of the brake base plate 1, with a compact structure and a reasonable layout, which helps the clearance compensation mechanism 3 to directly act on the end of the brake shoe 2.

[0044] The upper parts of the two brake shoes 2 are interconnected by a large spring 10, and the lower parts of the two brake shoes 2 are interconnected by a small spring 11; a shoe shaft 12 is symmetrically installed on the brake base plate 1 located at the gap between the two brake shoes 2, and the lower end of a single brake shoe 2 is clamped with the corresponding shoe shaft 12; the concave annular structure of the lower end of the brake shoe 2 is clamped with the circumference of the shoe shaft 12, and the large spring 10 and the small spring 11 for return are used to realize the floating installation of the brake shoe 2 relative to the brake base plate 1, and the return spring structure is symmetrically distributed relative to the braking center, which helps the overall stability of the braking mechanism.

[0045] A dust cover 6 is fixedly installed on the rear end face of the brake base plate 1, and the flanges on the edges of the dust cover 6 enclose the brake shoes 2 on both sides; an air chamber bracket 5 is installed through the dust cover 6 from back to front, and the front end face of the air chamber bracket 5 is fixed to the brake base plate 1; the camshaft 7 passes through the air chamber bracket 5 front and back, and an adjusting arm 8 is installed on the camshaft 7 located outside the rear end head of the air chamber bracket 5; multiple friction plates 9 are installed on the outer arc surface of a single brake shoe 2.

[0046] like Figure 5 and Figure 6As shown, the structure of the gap adjustment mechanism 4 is as follows: it includes an upper tooth seat 402 and a lower tooth seat 401 which are fixedly mounted in cooperation with each other, a rotating shaft 411 is installed through the upper tooth seat 402 and the lower tooth seat 401 from top to bottom, and a transmission wheel 403 is sleeved on the rotating shaft 411 located above the upper tooth seat 402; a dial sleeve 405 is sleeved on the rotating shaft 411 located above the transmission wheel 403, and an adjustment sleeve 407 is installed on the inner wall surface of the dial sleeve 405 through a one-way bearing 414, and the adjustment sleeve 407 is sleeved on the rotating shaft 411, and the upper part of the adjustment sleeve 407 passes through the dial sleeve 405 upwards, and the adjustment sleeve 407 is located at the adjusting sleeve 40 A cover cap 409 is clamped on the rotating shaft 411 above 7; a tooth group 408 is installed between the cover cap 409 and the adjustment sleeve 407; a support shaft 412 is installed on the circumferential wall surface of the upper gear seat 402 and the lower gear seat 401, and a driven wheel 410 is installed at the end of the support shaft 412 located inside the upper gear seat 402 and the lower gear seat 401, and the driven wheel 410 is meshed with the bevel teeth of the transmission wheel 403; the outer wall surface of the adjustment sleeve 405 is clamped with the camshaft 7, and the bevel teeth of the driven wheel 410 pass downward through the bottom surface of the lower gear seat 401, and the driven wheel 410 located at the bottom of the lower gear seat 401 is meshed with the gap compensation mechanism 3.

[0047] A spring 406 is installed between the dial sleeve 405 and the tooth plate group 408. Figure 8 As shown, the tooth plate group 408 includes an outer tooth plate 4081 and an inner tooth plate 4082 which are stacked at intervals, and friction transmission is performed between adjacent inner tooth plates 4082 and outer tooth plates 4081; the compression force of the spring 406 ensures the friction transmission between the inner tooth plate 4082 and the outer tooth plate 4081 in the tooth plate group 408, which helps to realize the overload protection function inside the mechanism; the inner tooth plate 4082 is clamped with the inner tooth groove 4071 of the adjustment sleeve 407 through the inner teeth, and the outer tooth plate 4081 is clamped with the outer tooth groove 4091 of the cover cap 409 through the outer teeth; retaining rings 413 are respectively clamped at both ends of the rotating shaft 411 located above the cover cap 409 and below the lower gear seat 401; the top end of the rotating shaft 411 extends backward from the brake base plate 1.

[0048] like Figure 7 As shown, the circumferential wall surface of the adjustment sleeve 405 is provided with an adjustment hole 4051, and the circumferential wall surface of the camshaft 7 is provided with a pin hole 72. Figure 4 As shown, a pin shaft is fixed in the pin hole 72, and the end of the pin shaft extends into the adjustment hole 4051; the size of the adjustment hole 4051 along the circumferential direction of the adjustment sleeve 405 is larger than the size of the pin shaft.

[0049] The pin shaft in the pin hole 72 on the side wall of the camshaft 7 applies a circumferential external force to the adjusting sleeve 405 in the clearance adjustment mechanism 4 through the adjusting hole 4051; the cam 71 of the camshaft 7 reciprocates within a preset rotation range. Due to the presence of the one-way bearing 414 between the adjusting sleeve 405 and the adjusting sleeve 407 in the clearance adjustment mechanism 4, it helps to achieve one-way compensation. At the same time, the cam 71 does not need to expand the reciprocating stroke due to clearance compensation, thereby effectively ensuring the stability of braking.

[0050] A gasket 404 is installed between the bottom surface of the dial sleeve 405 and the top surface of the upper gear seat 402; the gasket 404 includes a stacked flat gasket and a butterfly gasket. The presence of the butterfly gasket effectively buffers the shaking of the dial sleeve 405 under external vibration, thereby ensuring the transmission of circumferential force between the dial sleeve 405 and the camshaft 7.

[0051] like Fig. 9 and Fig.10 As shown, the structure of the clearance compensation mechanism 3 is as follows: it includes a limit plate 31 fixed to the front end of the chamber 102, a rotating shaft 33 is rotatably mounted on the inner side of the limit plate 31, the axial direction of the rotating shaft 33 is perpendicular to the axial direction of the camshaft 7, and synchronous wheels 34 are respectively mounted on both ends of the rotating shaft 33; each synchronous wheel 34 is meshed with a piston cylinder 36, and the two piston cylinders 36 are arranged at intervals and their axial directions are located on the same straight line; the ends of the two piston cylinders 36 facing each other are respectively clamped with piston heads 37 through retaining springs, and the retaining springs make the piston heads 37 and the piston cylinders 36 axially moves synchronously, but the piston cylinder 36 can rotate relative to the piston head 37 under the action of force; the ends of the two piston cylinders 36 at the opposite ends are respectively threadedly equipped with screws 35; the opposite surfaces of the two piston heads 37 are in contact with the cam 71 together, and the outer ends of the two screws 35 extend to the outside of the chamber 102 respectively, and the outer ends of the two screws 35 are clamped with the corresponding brake shoes 2, and the brake shoes 2 limit the circumferential rotation of the screws 35; the outer wall surface of one of the piston cylinders 36 is meshed and assembled with the driven wheel 410 in the gap adjustment mechanism 4.

[0052] The inner side of the limit plate 31 extends inward to form parallel lugs 32, and through holes are formed through the two lugs 32. The shaft 33 passes through the two lugs 32 through the through holes. Synchronous wheels 34 are respectively mounted on both ends of the shaft 33 outside the two lugs 32. Fig.11 As shown, a protrusion 321 extends from the inner end of each single lug 32, and a groove 371 is axially opened on the circumferential surface of the piston head 37 located outside the piston cylinder 36, and the protrusion 321 is accommodated in the groove 371; a bump 372 is axially extended inwardly from the inner side surface facing the piston head 37, and the groove 371 is located on the bump 372; when the piston head 37 moves axially toward the piston cylinder 36 under the drive of the cam 71, the protrusion 321 moves axially in the opposite direction relative to the groove 371 on the piston head 37, and the cooperation between the protrusion 321 and the groove 371 limits the axial movement of the piston head 37.

[0053] like Fig.12 As shown, the structure of the brake base plate 1 is as follows: it includes a plate body 101, a chamber 102 is extended forward from the upper end of the front side of the plate body 101, a main through hole 104 is opened through the chamber 102 front and back, the camshaft 7 is accommodated in the main through hole 104, a transverse hole 105 is opened through the chamber 102 left and right, the gap compensation mechanism 3 is accommodated in the transverse hole 105, and a side hole 103 which is connected with the transverse hole 105 is also opened in the chamber 102 located on the side of the main through hole 104, the axial direction of the side hole 103 is parallel to the main through hole 104, the gap adjustment mechanism 4 is accommodated in the side hole 103, and the end of the rotating shaft 411 in the gap adjustment mechanism 4 extends out of the brake base plate 1 through the rear opening of the side hole 103; a boss 106 is extended forward from the lower end of the front side of the plate body 101, and an axial hole 107 is opened in parallel through the boss 106 front and back, and a shoe shaft 12 is installed in the axial hole 107.

[0054] The working principle of the present invention is:

[0055] The adjusting arm 8 drives the camshaft 7 to rotate, and the cam 71 at the end of the camshaft 7 simultaneously applies force to the two piston heads 37 to move axially, so that the piston cylinder 36 and the screw rod 35 move axially outward with the piston head 37, so that the outer ends of the two screw rods 35 move outward and synchronously push the corresponding brake shoes 2 outward, that is, the leading shoe and the trailing shoe move outward synchronously for braking, thereby realizing the synchronous axial movement of the coaxial screw rod 35;

[0056] When the brake clearance is large, when the camshaft 7 rotates, the pin in the pin hole 72 on its side wall applies force to the adjusting sleeve 405 in the clearance adjustment mechanism 4 through the adjusting hole 4051; the adjusting sleeve 405 rotates, and drives the adjusting sleeve 407 to rotate through the one-way bearing 414, and cooperates with the compression pressure of the spring 406 acting on the gear group 408, so that the adjusting sleeve 407 drives the gear group 408 to rotate synchronously, and the gear group 408 drives the cover cap 409 to rotate, and the cover cap 409 drives the rotating shaft 411 to rotate, so that the transmission wheel 403 rotates with the rotating shaft 411, and the driven wheel 410 meshing with the bevel teeth of the transmission wheel 403 rotates, and then the bevel teeth of the driven wheel 410 extending downward from the bottom surface of the lower gear seat 401 drive the clearance compensation mechanism 3 to work; the clearance adjustment mechanism 4 converts the circumferential force parallel to the axial direction of the adjusting sleeve 405 into a circumferential transmission of the driven wheel 410 perpendicular to the axial direction of the adjusting sleeve 405;

[0057] The rotation of the driven wheel 410 causes the piston cylinder 36 engaged with it to rotate around its own axial direction. The screw 35 threadedly connected to the piston cylinder 36 is axially rotated out relative to the piston cylinder 36 due to the circumferential limit of the corresponding brake shoe 2; synchronously, the piston cylinder 36 drives the engaged synchronous wheel 34 to rotate, and the fixed rotating shaft 33 and the other synchronous wheel 34 rotate accordingly, thereby driving the other piston cylinder 36 to rotate synchronously, so that the other screw 35 is synchronously rotated out, thereby driving the brake shoes 2 on both sides, that is, the leading shoe and the trailing shoe to move synchronously outward relative to the piston cylinder 36, thereby realizing the synchronous adjustment of the braking clearance on the outer side of the brake shoe 2.

[0058] When the circumferential external force transmitted from the camshaft 7 to the rotation of the adjustment sleeve 405 exceeds a certain value and is transmitted to the gear set 408 via the one-way bearing 414 and the adjustment sleeve 407, sliding friction will be generated between the inner gear piece 4082 and the outer gear piece 4081 in the gear set 408, so that the gear set 408 as a whole will not rotate synchronously with the adjustment sleeve 407, that is, the adjustment sleeve 407 cannot drive the cap 409 to rotate via the gear set 408, thereby playing a role of overload protection.

[0059] When the camshaft 7 rotates in the opposite direction, the circumferential force applied to the adjusting sleeve 405 by the pin shaft is reversed, and the adjusting sleeve 405 rotates in the opposite direction. Since the adjusting sleeve 405 and the adjusting sleeve 407 are transmitted via the one-way bearing 414, the adjusting sleeve 407 does not rotate with the adjusting sleeve 405 due to the presence of the one-way bearing 414, thereby ensuring the one-way self-adjustment of the clearance.

[0060] A force is applied to the top of the rotating shaft 411 from the rear end face of the brake base plate 1, causing the rotating shaft 411 to rotate, and then transmitted to the gap compensation mechanism 3 through the transmission wheel 403 and the driven wheel 410, thereby realizing the adjustment of the positive or negative braking clearance of the gap compensation mechanism 3, which greatly facilitates the maintenance or replacement operations in the aftermarket.

[0061] The invention has a compact structure and an ingenious and reasonable layout, realizes the self-adjustment of the brake clearance of the brake shoe end of the drum brake, is stable and reliable, and is convenient for adjustment and maintenance in the aftermarket.

[0062] The above description is an explanation of the present invention, not a limitation of the present invention. The scope of the present invention is defined in the claims. Any form of modification may be made within the scope of protection of the present invention.

Claims

1. A clearance self-adjusting drum brake, comprising a brake base plate (1), arc-shaped brake shoes (2) being symmetrically arranged on both sides of the front end surface of the brake base plate (1), characterized in that: A chamber (102) is extended from the front end surface of the brake base plate (1) at the upper gap between the two brake shoes (2), and a camshaft (7) is installed in the chamber (102); the camshaft (7) extends from the rear end surface of the brake base plate (1) into the chamber (102), a cam (71) is installed at the end of the camshaft (7) in the chamber (102), and a clearance compensation mechanism (3) is installed on the side of the cam (71), and the two ends of the clearance compensation mechanism (3) extend out of the chamber (102), and the two ends of the clearance compensation mechanism (3) located outside the chamber (102) are The ends are respectively clamped with the upper parts of the corresponding brake shoes (2); a clearance adjustment mechanism (4) is meshed and installed on the clearance compensation mechanism (3) located inside the chamber (102), and the clearance adjustment mechanism (4) is clamped with the camshaft (7); the upper parts of the two brake shoes (2) are interconnected by a large spring (10), and the lower parts of the two brake shoes (2) are interconnected by a small spring (11); a shoe shaft (12) is symmetrically installed on the brake bottom plate (1) located at the gap between the lower parts of the two brake shoes (2), and the lower end of a single brake shoe (2) is clamped with the corresponding shoe shaft (12); The structure of the gap adjustment mechanism (4) is as follows: it comprises an upper tooth seat (402) and a lower tooth seat (401) which are fixedly mounted in cooperation with each other; a rotating shaft (411) is installed through the upper tooth seat (402) and the lower tooth seat (401) from top to bottom; a transmission wheel (403) is sleeved on the rotating shaft (411) located above the upper tooth seat (402); a dial sleeve (405) is sleeved on the rotating shaft (411) located above the transmission wheel (403); an adjustment sleeve (407) is installed on the inner wall surface of the adjustment sleeve (405) via a one-way bearing (414); the adjustment sleeve (407) is sleeved on the rotating shaft (411); the upper part of the adjustment sleeve (407) passes through the dial sleeve (405) upwards; the rotating shaft (411) located above the adjustment sleeve (407) is sleeved on the rotating shaft (411); the upper part of the adjustment sleeve (407) passes through the adjustment sleeve (405) upwards; A cover cap (409) is clamped on the driving shaft (411); a tooth plate group (408) is installed between the cover cap (409) and the adjustment sleeve (407); a support shaft (412) is installed on the circumferential wall surface of the upper gear seat (402) and the lower gear seat (401); a driven wheel (410) is installed at the end of the support shaft (412) located inside the upper gear seat (402) and the lower gear seat (401); the driven wheel (410) is meshed with the bevel teeth of the transmission wheel (403); the outer wall surface of the adjustment sleeve (405) is clamped on the camshaft (7); the bevel teeth of the driven wheel (410) pass downward through the bottom surface of the lower gear seat (401); the driven wheel (410) located at the bottom of the lower gear seat (401) is meshed with the clearance compensation mechanism (3).

2. The clearance self-adjusting drum brake according to claim 1, characterized in that: The rear end surface of the brake base plate (1) is fixedly provided with a dust cover (6), and the flanges at the edges of the dust cover (6) enclose the brake shoes (2) on both sides; an air chamber bracket (5) is installed through the dust cover (6) from back to front, and the front end surface of the air chamber bracket (5) is fixedly provided with the brake base plate (1); the camshaft (7) passes through the air chamber bracket (5) from front to back, and an adjustment arm (8) is installed on the camshaft (7) located outside the rear end head of the air chamber bracket (5); and a plurality of friction plates (9) are installed on the outer arc surface of each brake shoe (2).

3. The clearance self-adjusting drum brake according to claim 1, characterized in that: A spring (406) is installed between the adjustment sleeve (405) and the tooth plate group (408); the tooth plate group (408) comprises an outer tooth plate (4081) and an inner tooth plate (4082) which are stacked at intervals; adjacent inner tooth plates (4082) and outer tooth plates (4081) are frictionally driven; the inner tooth plates (4082) are clamped with the inner tooth grooves (4071) of the adjustment sleeve (407) via inner teeth, and the outer tooth plates (4081) are clamped with the outer tooth grooves (4091) of the cover cap (409) via outer teeth; retaining rings (413) are respectively clamped at both ends of the rotating shaft (411) located above the cover cap (409) and below the lower gear seat (401); and the top end of the rotating shaft (411) extends backwards out of the brake base plate (1).

4. The clearance self-adjusting drum brake according to claim 1, characterized in that: The adjusting sleeve (405) is provided with an adjusting hole (4051) on its circumferential wall surface, the camshaft (7) is provided with a pin hole (72) on its circumferential wall surface, a pin shaft is fixedly installed in the pin hole (72), and the end of the pin shaft extends into the adjusting hole (4051); the dimension of the adjusting hole (4051) along the circumferential direction of the adjusting sleeve (405) is larger than the dimension of the pin shaft.

5. The clearance self-adjusting drum brake according to claim 1, characterized in that: A gasket (404) is installed between the bottom surface of the adjustment sleeve (405) and the top surface of the upper gear seat (402); the gasket (404) comprises a stacked flat gasket and a butterfly gasket.

6. The clearance self-adjusting drum brake according to claim 1, characterized in that: The structure of the clearance compensation mechanism (3) is as follows: it comprises a limit plate (31) fixed to the front end of the chamber (102); a rotating shaft (33) is rotatably mounted on the inner side surface of the limit plate (31); the axial direction of the rotating shaft (33) is perpendicular to the axial direction of the cam shaft (7); and synchronous wheels (34) are respectively mounted on both ends of the rotating shaft (33); each synchronous wheel (34) is meshedly mounted with a piston cylinder (36); the two piston cylinders (36) are arranged at intervals and their axial directions are located on the same straight line; the ends of the two piston cylinders (36) facing each other are respectively mounted with piston heads (37) via retaining springs; the ends of the two piston cylinders (36) facing each other are respectively mounted with screw rods (35) threadedly; the opposite surfaces of the two piston heads (37) are in contact with the cam (71); the outer ends of the two screw rods (35) extend to the outside of the chamber (102) respectively; and the outer ends of the two screw rods (35) are mounted with corresponding brake shoes (2).

7. The clearance self-adjusting drum brake according to claim 6, characterized in that: The inner side surface of the limit plate (31) extends inward to form lugs (32) arranged in parallel, and a through hole is formed through the two lugs (32). The rotating shaft (33) passes through the two lugs (32) through the through hole, and the two ends of the rotating shaft (33) located outside the two lugs (32) are respectively provided with synchronous wheels (34); a protrusion (321) extends from the inner end of each lug (32), and a groove (371) is formed on the circumferential surface of the piston head (37) located outside the piston cylinder (36) along the axial direction, and the protrusion (321) is accommodated in the groove (371); and a convex block (372) is extended inward along the axial direction on the inner side surface of the piston head (37) facing each other, and the groove (371) is located on the convex block (372).

8. The clearance self-adjusting drum brake according to claim 1, characterized in that: The brake base plate (1) has the following structure: it comprises a plate body (101); a chamber (102) extends forward from the upper end of the front side surface of the plate body (101); a main through hole (104) is formed through the chamber (102) from front to back; a transverse hole (105) is formed through the chamber (102) from left to right; a side hole (103) is formed in the chamber (102) located on the side of the main through hole (104) and is connected to the transverse hole (105); the axial direction of the side hole (103) is parallel to the main through hole (104); a boss (106) extends forward from the lower end of the front side surface of the plate body (101); and axial holes (107) are formed in parallel through the boss (106) from front to back.

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