CN115076266A - Automobile drum brake and clearance calculation method thereof - Google Patents
Automobile drum brake and clearance calculation method thereof Download PDFInfo
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- CN115076266A CN115076266A CN202210630095.XA CN202210630095A CN115076266A CN 115076266 A CN115076266 A CN 115076266A CN 202210630095 A CN202210630095 A CN 202210630095A CN 115076266 A CN115076266 A CN 115076266A
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- 238000004364 calculation method Methods 0.000 title claims abstract description 11
- 230000007246 mechanism Effects 0.000 claims abstract description 14
- 230000000712 assembly Effects 0.000 claims abstract 8
- 238000000429 assembly Methods 0.000 claims abstract 8
- 238000005452 bending Methods 0.000 claims description 10
- 108700041286 delta Proteins 0.000 claims description 6
- 238000000034 method Methods 0.000 claims description 3
- 238000005299 abrasion Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
- F16D65/00—Parts or details
- F16D65/38—Slack adjusters
- F16D65/40—Slack adjusters mechanical
- F16D65/52—Slack adjusters mechanical self-acting in one direction for adjusting excessive play
- F16D65/56—Slack adjusters mechanical self-acting in one direction for adjusting excessive play with screw-thread and nut
- F16D65/561—Slack adjusters mechanical self-acting in one direction for adjusting excessive play with screw-thread and nut for mounting within the confines of a drum brake
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
- F16D65/00—Parts or details
- F16D65/14—Actuating mechanisms for brakes; Means for initiating operation at a predetermined position
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
- F16D2121/00—Type of actuator operation force
- F16D2121/02—Fluid pressure
- F16D2121/04—Fluid pressure acting on a piston-type actuator, e.g. for liquid pressure
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Abstract
The invention relates to an automobile drum brake and a clearance calculation method thereof, wherein a pair of brake shoes are arranged between a bottom plate and a brake drum, wheel cylinder assemblies are arranged at the splicing positions of the two ends of each brake shoe, the end parts of the brake shoes are respectively abutted against the end parts of pistons of the corresponding wheel cylinder assemblies, the other ends of the brake shoes can be rotatably fixed on the bottom plate, return springs are arranged on the brake shoes at the side parts of the wheel cylinder assemblies, the two ends of each return spring are respectively fixed on the corresponding brake shoes, a self-adjusting mechanism is arranged between the two brake shoes close to the wheel cylinder assemblies, the self-adjusting mechanism comprises a self-adjusting dial plate, a self-adjusting screw rod, a self-adjusting screw sleeve and a ratchet wheel, the tail end of the self-adjusting screw rod is clamped on the brake shoe at the left side, external threads are arranged on the self-adjusting screw rod outside the tail end of the screw rod, the ratchet wheel is sleeved on the self-adjusting screw rod and is in threaded fit with the self-adjusting screw rod, and the end part of the self-adjusting screw sleeve is fixed on the other brake shoe, the self-adjusting shifting plate realizes the adjustment of the clearance between the friction plate and the brake drum.
Description
Technical Field
The invention belongs to the technical field of automobile braking, and relates to an automobile drum brake and a clearance calculation method thereof.
Background
Along with the higher and higher requirement of customers on the driving comfort of automobiles, the requirement of each large host factory on the brake pedal feeling of automobiles is higher, and meanwhile, according to the requirement of national regulations, after the friction plate is worn, the gap between the friction plate and the brake drum is continuously increased, and an automobile brake must have an automatic gap adjusting mechanism and an automatic gap adjusting function, so that the gap of the friction plate from a new product to the wear limit is ensured to be within a certain range, the stroke stability of the pedal during braking is ensured, and reasonable braking time and good brake pedal feeling are obtained. An accurate automatic gap adjustment device is very important for the brake.
Disclosure of Invention
In view of the above, the present invention provides a drum brake for an automobile having a self-adjusting mechanism and a clearance calculating method thereof.
In order to achieve the purpose, the invention provides the following technical scheme:
a drum brake for car is composed of a base plate, a pair of symmetrical brake shoes between base plate and drum, two brake shoes connected together in a ring shape, friction plates for matching with drum, wheel cylinder assembly with one end connected to piston of wheel cylinder assembly, return spring with two ends fixed to relative brake shoes, self-regulating mechanism between two brake shoes, and self-regulating screw rod with tail end fixed to left brake shoe, the self-adjusting screw rod is provided with external threads outside the tail end of the screw rod, the ratchet wheel is sleeved on the self-adjusting screw rod close to the tail end of the screw rod and is in threaded fit with the self-adjusting screw rod, the end part of the self-adjusting screw sleeve is fixed on the other brake shoe after the self-adjusting screw sleeve is sleeved on the self-adjusting screw rod, the self-adjusting screw sleeve can move on the self-adjusting screw rod, the self-adjusting shifting plate is fixed on the brake shoe fixed with the self-adjusting screw rod, the ratchet wheel can be shifted, and the gap between the friction plate and the brake drum can be adjusted.
Furthermore, a U-shaped clamping groove I is formed in the tail end of the screw, and a bayonet matched with the tail end of the screw is formed in the brake shoe.
Further, the self-adjusting shifting plate comprises a clamping piece, a plate body and a shifting piece, the self-adjusting shifting plate is similar to the U-shaped shape, the plate body is equivalent to the middle part of the U-shaped shape, the clamping piece and the shifting piece are equivalent to two sides of the U-shaped shape, the plate body is fixed on the brake shoe through the mandrel, the self-adjusting shifting plate can rotate around the mandrel, the clamping piece is located on the left side of the mandrel, the shifting piece is located on the right side of the mandrel, one end of the self-adjusting tension spring is fixed on the plate body on the right side of the mandrel, the other end of the self-adjusting tension spring is fixed on the lower portion of the corresponding brake shoe, the clamping piece is clamped in a groove at the tail of the self-adjusting screw rod, and the shifting piece can shift the ratchet wheel when the friction plate is worn.
Furthermore, the plate body comprises a flat plate and a right-angle bending plate, the flat plate is used for being fixed on the brake shoe, the mandrel is fixed on the flat plate, the bending plate is located on the right side of the mandrel, the horizontal part of the bending plate extends towards the ratchet wheel, the tail end of the horizontal part of the bending plate is connected with a shifting sheet which is bent downwards, and the shifting sheet is located above the gear teeth of the ratchet wheel and close to the gear teeth.
Furthermore, the gear teeth of the ratchet wheel incline towards one side so as to be convenient for the shifting piece to shift, and after the ratchet wheel is installed, the gear teeth of the ratchet wheel face from bottom to top and from outside to inside.
A clearance calculation method for an automotive drum brake includes the steps of:
s1: defining one-side clearance between a brake friction plate and a brake drum as SCC, the inner diameter of the brake drum as D1, and the outer diameter of the friction plate as D2, then SCC is (D1-D2)/2.
S2: establishing a theoretical model, wherein during braking, a piston of a wheel cylinder assembly pushes a brake shoe to rotate around a supporting block rotation point until a friction plate eliminates a gap SCC, a horizontal gap delta 1 is generated between the brake shoe and the bottom of a clamping groove of a self-adjusting screw rod, a horizontal gap delta 2 is generated between a clamping piece of a self-adjusting shifting plate and the bottom of the clamping groove of the self-adjusting screw rod, the vertical distance between the horizontal center of the friction plate and the horizontal center of the self-adjusting screw rod is a, the vertical distance between the horizontal center of the friction plate and the center of the supporting block rotation point is b, and a geometric relationship can be used for obtaining a value of delta 1-delta 2-SCC (a + b)/b;
s3: when the friction plate is worn or the brake drum is thermally expanded, and the unilateral clearance between the friction plate and the brake drum is slightly larger than SCC, when the wheel cylinder assembly brakes, the self-adjusting shifting plate jumps from the initial position J0 to the final position J1 under the action of the self-adjusting spring force, the gear teeth of the ratchet wheel start to be shifted, the ratchet wheel rotates around the self-adjusting screw rod, after the braking is eliminated, the shifting plate shifting point of the self-adjusting shifting plate jumps from the final position J1 to the initial position J0 after the friction is worn, the initial position J 'after the friction plate is worn is braked next time, and the shifting plate point position of the shifting plate shifts the ratchet wheel by a tooth pitch P from the initial position J' after the friction plate is worn.
S4, theoretical calculation formula:
the relationship among a ratchet wheel tooth pitch P, a ratchet wheel diameter D, a ratchet wheel tooth number Z, a thread tooth pitch T, a vertical distance C between the axis of a core shaft of the self-adjusting shifting plate and the axis of the self-adjusting screw rod, and a horizontal vertical distance D between the axis of the core shaft of the self-adjusting shifting plate and the right end face of the ratchet wheel is as follows:
further, when the friction plate is not abraded, the shifting piece shifting point of the self-adjusting shifting plate jumps from the shifting piece initial position J0 to the shifting piece final position J1, just moves one ratchet wheel tooth pitch P, and the ratchet wheel cannot be shifted.
The invention has the beneficial effects that:
the automobile drum brake is additionally provided with an automatic gap adjusting mechanism, and meanwhile, the gap of the automobile drum brake can be accurately and reasonably calculated to determine whether the gap between a friction plate of the brake and a brake drum meets the specification requirement in the whole abrasion range.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the means of the instrumentalities and combinations particularly pointed out hereinafter.
Drawings
In order to make the objects, technical solutions and advantages of the present invention more clear, the present invention will be described in detail with reference to the accompanying drawings, wherein fig. 1 is a front view of the present invention;
FIG. 2 is a perspective view of the present invention;
FIG. 3 is a longitudinal cross-sectional view of the self-adjusting screw of the present invention;
FIG. 4 is a longitudinal cross-sectional view at the middle of the present invention;
FIG. 5 is a schematic view of the self-adjusting screw, the self-adjusting barrel and the ratchet wheel of the present invention;
FIG. 6 is a schematic structural view of the self-adjusting dial plate of the present invention;
FIG. 7 is a plot of some of the data on the brake shoe of the present invention;
FIG. 8 is a schematic view of the ratchet of the present invention and some data labels;
FIG. 9 is an enlarged schematic view at X in FIG. 8 and a position-marked view of the paddle;
FIG. 10 is a schematic diagram showing the minimum and maximum horizontal vertical distances d between the axis of the mandrel and the right end face of the ratchet of the automatic shifting plate according to the present invention.
Reference numerals:
1. a base plate; 2. a brake drum; 3. a brake shoe; 31. a friction plate; 32. a tension spring; 33. a mandrel; 4. a wheel cylinder assembly; 5. a support block; 51. supporting block rotation point; 6. a return spring; 7. a self-adjusting mechanism; 71. a self-adjusting dial plate; 711. a card; 712. a plate body; 7121. a bending plate; 713. a shifting sheet; 72. self-adjusting screw rods; 721. a first clamping groove; 722. a limiting bulge; 723. a second clamping groove; 73. self-adjusting thread sleeves; 74. a ratchet wheel; 75. and a tension spring is automatically adjusted.
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention in a schematic way, and the features in the following embodiments and examples may be combined with each other without conflict.
Wherein the showings are for the purpose of illustrating the invention only and not for the purpose of limiting the same, and in which there is shown by way of illustration only and not in the drawings in which there is no intention to limit the invention thereto; to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
The same or similar reference numerals in the drawings of the embodiments of the present invention correspond to the same or similar components; in the description of the present invention, it should be understood that if there is an orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "front", "rear", etc., based on the orientation or positional relationship shown in the drawings, it is only for convenience of description and simplification of description, but it is not an indication or suggestion that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes, and are not to be construed as limiting the present invention, and the specific meaning of the terms may be understood by those skilled in the art according to specific situations.
Referring to fig. 1 to 10, an automotive drum brake includes a base plate 1 and a brake drum 2 fastened on the base plate 1, a brake shoe 3 assembly is disposed between the base plate 1 and the brake drum 2, the brake shoe 3 assembly includes a pair of symmetric brake shoes 3, the brake shoes 3 are in a semi-annular structure, the two brake shoes 3 are joined into an annular shape, and a friction plate 31 for cooperating with the brake drum 2 is attached to an outer side wall of the brake shoes 3. At the splicing positions of the two ends of the brake shoe 3, one splicing position is provided with a wheel cylinder assembly 4, and the other splicing position is provided with a supporting block 5. The wheel cylinder assembly 4 is fixed on the bottom plate 1, and the wheel cylinder assembly 4 comprises a pair of pistons capable of extending outwards and providing thrust for the brake shoes 3. And return springs 6 are arranged on the inner side of the wheel cylinder assembly 4 close to the wheel cylinder assembly 4, two ends of each return spring 6 are respectively hooked on the corresponding brake shoe 3, and under the action of the tensile force of each return spring 6, the end parts of the brake shoes 3 are respectively abutted against the corresponding piston end parts.
The supporting block 5 is fixed on the bottom plate 1, the supporting block 5 plays a role in supporting the brake shoe 3, a groove clamped with the end of the supporting block 5 is formed in the end of the brake shoe 3, a tension spring 32 is arranged outside the supporting block 5, two ends of the tension spring 32 are respectively hooked on the corresponding end of the brake shoe 3, and the tension spring 32 tensions the other end of the brake shoe 3 to enable the other end to be clamped on the supporting block 5. The brake shoes 3 are rotated around the supporting block rotating points 51 on the supporting blocks 5, respectively, by the push of the pistons.
And a self-adjusting mechanism 7 is arranged between the two brake shoes 3 close to the wheel cylinder assembly 4, and the self-adjusting mechanism 7 can automatically adjust the clearance between the friction plate 31 and the brake drum 2 after the friction plate 31 is worn.
The self-adjusting mechanism 7 comprises a self-adjusting dial plate 71, a self-adjusting screw 72, a self-adjusting screw sleeve 73 and a ratchet wheel 74. The tail end of a screw rod of the self-adjusting screw rod 72 is clamped on the left brake shoe 3, a U-shaped clamping groove 721 is arranged at the tail end of the screw rod, a bayonet matched with the tail end of the screw rod is arranged on the brake shoe 3, external threads are arranged on the self-adjusting screw rod 72 outside the tail end of the screw rod, a ratchet wheel 74 is sleeved on the self-adjusting screw rod 72 close to the tail end of the screw rod, and the ratchet wheel 74 is in threaded fit with the self-adjusting screw rod 72. The self-adjusting screw sleeve 73 is sleeved on the self-adjusting screw 72, the inner hole of the self-adjusting screw sleeve 73 is unthreaded, the length of the self-adjusting screw 72 on the right side of the ratchet 74 is smaller than the length of the inner cylinder of the self-adjusting screw sleeve 73, and the self-adjusting screw sleeve 73 can reciprocate on the self-adjusting screw 72, so that an adjusting space flows out of the ratchet 74. The other end of the self-adjusting screw sleeve 73 without the hole is clamped on the other brake shoe 3. The spring body of the return spring 6 is sleeved on the self-adjusting threaded sleeve 73, a gap is reserved between the spring body of the return spring 6 and the self-adjusting threaded sleeve 73, and the spring body of the return spring 6 and the self-adjusting threaded sleeve 73 are coaxial, so that the structure is more compact. Under the action of the pulling force of the return spring 6, the self-adjusting threaded sleeve 73 is abutted against the right side of the ratchet wheel 74.
The self-adjusting shifting plate 71 is arranged on the brake shoe 3 clamped with the self-adjusting screw rod 72, the self-adjusting shifting plate 71 comprises a clamping plate 711, a plate body 712 and a shifting piece 713 which are connected into a whole, the self-adjusting shifting plate 71 is similar to a U shape, the plate body 712 is equivalent to the middle part of the U shape, and the clamping plate 711 and the shifting piece 713 are equivalent to two sides of the U shape. The plate 712 is fixed to the brake shoe 3 by the spindle 33, and the self-aligning plate 71 can rotate around the spindle 33. The tail end of the screw rod clamped into the brake shoe 3 is also provided with a second clamping groove 723 matched with the card 711, and a limiting bulge 722 is arranged between the second clamping groove 723 and the first clamping groove 721 and used for limiting the card 711.
The plate body 712 includes a flat plate and a substantially right-angled bent plate 7121, the flat plate is used for being fixed on the brake shoe 3, the mandrel 33 is fixed on the flat plate, the clamping plate 711 is connected on the flat plate on the left side of the mandrel 33, the bent plate 7121 is located on the right side of the mandrel 33, the horizontal portion of the bent plate 7121 extends towards the ratchet 74, the tail end of the horizontal portion of the bent plate 7121 is connected with a shifting piece 713 with certain radian, and the shifting piece 713 is matched with the ratchet 74 and is used for shifting the ratchet 74. The length of paddle 713 is much wider than the width of ratchet 74 in order to meet the adjustment requirements. When friction plate 31 is not worn, in the rest state, paddle 713 is located immediately above the teeth of ratchet wheel 74, close to but not in contact with the teeth of ratchet wheel 74. The teeth of the ratchet 74 are angled toward one side, and when the ratchet 74 is installed, the teeth of the ratchet 74 face from bottom to top, from outside to inside. One end of the self-adjusting tension spring 75 is hooked on the vertical plate of the bending plate 7121 of the plate body 712, and the other end of the self-adjusting tension spring 75 is hooked on the lower portion of the corresponding brake shoe 3. Under the action of the tension of the self-adjusting tension spring 75, the card 711 is always clamped at the tail of the self-adjusting screw 72.
In view of the above, the present invention is directed to accurately and reasonably calculating the clearance between the brake lining 31 and the brake drum 2 to determine whether the clearance satisfies the specification requirement in the whole wear range.
The working principle of the invention is as follows:
the invention relates to a step gap adjusting brake. In an inoperative state, under the action of the tension of the return spring 6, the upper ends of the two brake shoes 3 respectively abut against the end parts of the corresponding pistons, the lower ends of the two brake shoes 3 respectively abut against the end parts of the supporting blocks 5, the self-adjusting threaded sleeves 73 of the self-adjusting mechanisms 7 abut against the self-adjusting screw rods 72, and the clamping pieces 711 are clamped at the tail parts of the self-adjusting screw rods 72. The friction plate 31 of the brake shoe 3 assembly maintains a certain clearance with the brake drum 2. When braking, the piston pushes the brake shoe 3 assembly to rotate around the rotation point of the supporting block 5 under the action of the hydraulic pressure of the wheel cylinder assembly 4, the gap between the brake drum 2 and the friction plate 31 is eliminated, and the piston presses on the brake drum 2 to rub with the brake drum 2 to generate braking force.
When the gap between the friction plate 31 and the brake drum 2 is increased due to abrasion, a brake shoe 3 assembly is pushed by a piston, after the gap between the friction plate 31 and the brake drum 2 is eliminated, a gap is generated between a clamping piece 711 of the self-adjusting shifting plate 71 and a clamping groove 723 of the self-adjusting screw 72, the self-adjusting shifting plate 71 rotates around the mandrel 33 under the action of the tension of the self-adjusting tension spring 75, the gap is eliminated, meanwhile, the automatic shifting piece 713 shifts one tooth of the tooth part of the ratchet 74, and the ratchet 74 cannot rotate due to the fact that the self-adjusting screw 72 is clamped on the brake shoe 3, and at the moment, the ratchet 74 rotates under the shifting of the self-adjusting shifting plate 71; the rotation of the ratchet wheel 74 enables the ratchet wheel 74 to move a certain distance towards the self-adjusting screw sleeve 73, the self-adjusting screw sleeve 73 moves outwards under the pushing of the ratchet wheel 74, and therefore the distance between the two brake shoes 3 is increased, the size of the outer circle of each brake shoe 3 is increased, and the increase of the clearance between the friction plate 31 and the brake drum 2 due to abrasion of the friction plate and the brake drum is compensated.
Because the self-adjusting screw rod 72 is horizontally limited and is in a horizontal position, the self-adjusting shifting plate 71 can only shift one tooth during each braking, the compensation clearance is very small, when the high-strength braking or the continuous braking is carried out, the temperature of the brake drum 2 is excessively increased, the thermal expansion is generated, the clearance between the friction plate 31 and the brake drum 2 is increased, the self-adjusting shifting plate 71 shifts the tooth part of the ratchet wheel 74 to compensate the clearance between one tooth, and after the brake drum 2 is cooled, the inner diameter of the brake drum 2 is reduced, so that the brake locking caused by the excessive adjustment is avoided.
A clearance calculation method for an automobile drum brake comprises the following steps:
s1: when the one-side clearance between the brake disk 31 and the brake drum 2 is defined as SCC, the inner diameter of the brake drum 2 is defined as D1, and the outer diameter of the disk 31 is defined as D2, SCC is (D1-D2)/2.
S2: establishing a theoretical model: during braking, the piston of the wheel cylinder assembly 4 pushes the brake shoe 3 to rotate around the supporting block rotating point 51 until the friction plate 31 eliminates the gap SCC, and the friction plate 31 is pressed on the brake drum 2; at this time, a horizontal gap Δ 1 is generated between the brake shoe 3 and the bottom of the first clamping groove 721 of the self-adjusting screw 72, a horizontal gap Δ 2 is generated between the clamping piece 711 of the self-adjusting plate 71 and the limiting protrusion 722 of the second clamping groove 723 of the self-adjusting screw 72, a vertical distance between a horizontal center of the friction plate 31 and a horizontal center of the self-adjusting screw 72 is a, a vertical distance between a horizontal center of the friction plate 31 and a center of the supporting block rotation point 51 is b, and Δ 1 ═ Δ 2 ═ SCC (a + b)/b can be obtained according to a geometric relationship.
Under the action of the tension of the self-adjusting tension spring 75, the clamping piece 711 of the self-adjusting shifting plate 71 rotates for a certain angle and then abuts against the first clamping groove 721 of the self-adjusting screw 72, and meanwhile, the shifting point of the shifting piece 713 of the self-adjusting shifting plate 71 jumps from the initial position J0 of the shifting piece 713 to the final position J1 of the shifting piece 713 and just moves one ratchet wheel 74 pitch P; the self-adjusting mechanism 7 does not perform clearance compensation at this time. When the braking is eliminated, the clearance delta 1 between the brake shoe 3 and the self-adjusting screw rod 72 and the clearance delta 2 between the card 711 and the self-adjusting screw rod 72 are 0; the setting point of the self-setting plate 71 returns from the end position J1 to the initial position J0.
S3: when the friction plate 31 is worn or the brake drum 2 is thermally expanded, and the unilateral clearance between the friction plate 31 and the brake drum 2 is slightly larger than SCC, and the wheel cylinder assembly 4 brakes, the self-adjusting shifting plate 71 under the tensile force of the self-adjusting tension spring 75, the shifting point of the shifting piece 713 jumps from the initial position J0 to the final position J1, the gear teeth of the ratchet wheel 74 start to be shifted, the ratchet wheel 74 rotates around the self-adjusting screw rod 72, the total length of the combination of the self-adjusting screw rod 72 and the self-adjusting screw sleeve 73 is increased, the brake shoe 3 is pushed to be opened outwards, and the increased clearance after the friction plate 31 is worn is compensated. When the brake is released, the tooth-shifting point of the blade 713 of the self-adjusting plate 71 jumps from the end position J1 to the initial position J0 after wear, which is just beyond the teeth of the ratchet wheel 74. For the next braking, the plate-shifting point of the plate-shifting point 713 shifts the ratchet 74 by a pitch P from the worn initial position J'.
S4, theoretical calculation formula:
the relationship between the tooth pitch P (distance from J1 to J0) of the ratchet wheel 74, the diameter D of the ratchet wheel 74, the tooth number Z of the ratchet wheel 74, the tooth pitch T of the screw thread, the vertical distance C between the axis of the rotating shaft of the self-adjusting dial plate 71 and the axis of the self-adjusting screw 72, and the horizontal vertical distance D between the axis of the mandrel 33 of the self-adjusting dial plate 71 and the right end face of the ratchet wheel 74 is as follows:
s5, the horizontal vertical distance d between the axial center of the spindle 33 of the self-aligning plate 71 and the right end surface of the ratchet 74 increases with the wear of the friction plate 31, and the clearance SCC between the friction plate 31 and the brake drum 2 decreases.
The maximum value and the minimum value of the clearance SCC between the friction plate 31 and the brake drum 2 are calculated by the above calculation method to determine whether the clearance SCC between the friction plate 31 and the brake drum 2 is reasonable.
Finally, the above embodiments are only intended to illustrate the technical solutions of the present invention and not to limit the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions, and all of them should be covered by the claims of the present invention.
Claims (7)
1. An automotive drum brake characterized by: the brake shoe comprises a bottom plate (1) and a brake drum (2) buckled on the bottom plate (1), a pair of symmetric brake shoes (3) is arranged between the bottom plate (1) and the brake drum (2), the two brake shoes (3) are spliced into a ring, friction plates (31) matched with the brake drum (2) are attached to the outer side walls of the brake shoes (3), wheel cylinder assemblies (4) are arranged at the splicing positions of two ends of one of the brake shoes (3), the end parts of the brake shoes (3) are respectively abutted against the end parts of pistons of the corresponding wheel cylinder assemblies (4), the other ends of the brake shoes (3) can be rotatably fixed on the bottom plate (1), the pistons of the wheel cylinder assemblies (4) can push the corresponding brake shoes (3), return springs (6) are arranged on the brake shoes (3) on the side parts of the wheel cylinder assemblies (4), and two ends of the return springs (6) are respectively fixed on the corresponding brake shoes (3), a self-adjusting mechanism (7) is arranged between the two brake shoes (3) close to the wheel cylinder assembly (4), the self-adjusting mechanism (7) comprises a self-adjusting shifting plate (71) and a self-adjusting screw rod (72), the self-adjusting device comprises a self-adjusting screw sleeve (73) and a ratchet wheel (74), the tail end of a screw rod of the self-adjusting screw rod (72) is clamped on a brake shoe (3) on the left side, external threads are arranged on the self-adjusting screw rod (72) outside the tail end of the screw rod, the ratchet wheel (74) is sleeved on the self-adjusting screw rod (72) close to the tail end of the screw rod and is in threaded fit with the self-adjusting screw rod (72), the end of the self-adjusting screw sleeve (73) is fixed on the other brake shoe (3) after the self-adjusting screw rod (72) is sleeved on the self-adjusting screw rod (73), the self-adjusting screw sleeve (73) can move on the self-adjusting screw rod (72), a self-adjusting shifting plate (71) is fixed on the brake shoe (3) fixed with the self-adjusting screw rod (72) and can shift the ratchet wheel (74), and the gap between a friction plate (31) and a brake drum (2) can be adjusted.
2. An automotive drum brake according to claim 1, characterized in that: the tail end of the screw is provided with a U-shaped clamping groove I (721), and the brake shoe (3) is provided with a bayonet matched with the tail end of the screw.
3. An automotive drum brake according to claim 1, characterized in that: the self-adjusting dial plate (71) comprises a card (711) which is connected into a whole, the self-adjusting shifting plate comprises a plate body (712) and shifting pieces (713), the self-adjusting shifting plate (71) is similar to a U shape, the plate body (712) is equivalent to the middle part of the U shape, clamping pieces (711) and the shifting pieces (713) are equivalent to two sides of the U shape, the plate body (712) is fixed on a brake shoe (3) through a mandrel (33), the self-adjusting shifting plate (71) can rotate around the mandrel (33), the clamping pieces (711) are located on the left side of the mandrel (33), the shifting pieces (713) are located on the right side of the mandrel (33), one end of a self-adjusting tension spring (75) is fixed on the plate body (712) on the right side of the mandrel (33), the other end of the self-adjusting tension spring (75) is fixed on the lower part of the corresponding brake shoe (3), the clamping pieces (711) are clamped in a groove in the tail of a self-adjusting screw rod (72), and the shifting pieces (713) can shift a ratchet wheel (74) when a friction plate (31) is worn.
4. An automotive drum brake according to claim 3, characterized in that: the plate body (712) comprises a flat plate and a right-angle bending plate (7121), the flat plate is used for being fixed on the brake shoe (3), the mandrel (33) is fixed on the flat plate, the bending plate (7121) is located on the right side of the mandrel (33), the horizontal part of the bending plate (7121) extends towards the ratchet wheel (74), the tail end of the horizontal part of the bending plate (7121) is connected with a shifting piece (713) bent downwards, and the shifting piece (713) is located above the gear teeth of the ratchet wheel (74) and close to the gear teeth.
5. An automotive drum brake according to claim 4, characterized in that: the gear teeth of the ratchet wheel (74) incline towards one side to facilitate shifting of the shifting piece (713), and after the ratchet wheel (74) is installed, the gear teeth of the ratchet wheel (74) face from bottom to top and from outside to inside.
6. A method of clearance calculation for an automotive drum brake according to any one of claims 1 to 5, comprising the steps of:
s1: the single-side clearance between the brake friction plate (31) and the brake drum (2) is defined as SCC, the inner diameter of the brake drum (2) is defined as D1, the outer diameter of the friction plate (31) is defined as D2, and then SCC is (D1-D2)/2.
S2: establishing a theoretical model, wherein during braking, a piston of a wheel cylinder assembly (4) pushes a brake shoe (3) to rotate around a supporting block rotating point (51) until a friction plate (31) eliminates a gap SCC, a horizontal gap delta 1 is generated between the brake shoe (3) and the bottom of a clamping groove of a self-adjusting screw rod (72), a horizontal gap delta 2 is generated between a clamping piece (711) of a self-adjusting dial plate (71) and the bottom of the clamping groove of the self-adjusting screw rod (72), the vertical distance between the horizontal center of the friction plate (31) and the horizontal center of the self-adjusting screw rod (72) is a, the vertical distance between the horizontal center of the friction plate (31) and the center of the supporting block rotating point (51) is b, and the geometric relation can obtain that delta 1 is delta 2 SCC (a + b)/b;
s3: when the friction plate (31) is worn or the brake drum (2) is thermally expanded, and the unilateral clearance between the friction plate (31) and the brake drum (2) is slightly larger than SCC, when the wheel cylinder assembly (4) brakes, the self-adjusting shifting plate (71) jumps from the initial position J0 to the final position J1 under the action of the self-adjusting tension spring (75), the gear teeth of the ratchet wheel (74) start to be shifted, the ratchet wheel (74) rotates around the self-adjusting screw rod (72), and when the braking is eliminated, the shifting point of the shifting plate (713) of the self-adjusting shifting plate (71) jumps from the final position J1 to the worn initial position J0 to reach the worn initial position J ', and then the next braking is carried out, and the shifting point position of the shifting plate (713) shifts the ratchet wheel (74) by one tooth pitch P from the worn initial position J'.
S4, theoretical calculation formula:
the relationship among the tooth pitch P of one ratchet wheel (74), the diameter D of the ratchet wheel (74), the tooth number Z of the ratchet wheel (74), the tooth pitch T of threads, the vertical distance C between the axis of a mandrel (33) of the self-adjusting shifting plate (71) and the axis of the self-adjusting screw rod (72), and the horizontal vertical distance D between the axis of the mandrel (33) of the self-adjusting shifting plate (71) and the right end face of the ratchet wheel (74) is as follows:
7. a clearance calculating method of an automotive drum brake as claimed in claim 6, wherein: when the friction plate (31) is not worn, the tooth shifting point of the shifting piece (713) of the self-adjusting shifting plate (71) jumps from the initial position J0 of the shifting piece (713) to the final position J1 of the shifting piece (713), just one ratchet wheel (74) tooth pitch P is moved, and the ratchet wheel (74) cannot be shifted.
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| GB1402527A (en) * | 1971-11-23 | 1975-08-13 | Girling Ltd | Automatic adjuster for an internal shoe drum brake |
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| CN209990821U (en) * | 2019-04-08 | 2020-01-24 | 浙江万安科技股份有限公司 | Self-adjusting shifting piece of drum brake and drum brake |
| CN210050222U (en) * | 2019-04-12 | 2020-02-11 | 靖江市恒大汽车部件制造有限公司 | Self-adjusting crank drum brake |
| CN210661146U (en) * | 2019-10-10 | 2020-06-02 | 无锡晶华汽车制动器有限公司 | Increase formula clearance from moving ahead brake |
| CN113738796A (en) * | 2021-08-31 | 2021-12-03 | 浙江亚太机电股份有限公司 | Brake with thermosensitive plate self-adjusting mechanism assembly |
| CN217502360U (en) * | 2022-06-06 | 2022-09-27 | 南方天合底盘系统有限公司 | Automobile drum brake with self-adjusting mechanism |
-
2022
- 2022-06-06 CN CN202210630095.XA patent/CN115076266B/en active Active
Patent Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1402527A (en) * | 1971-11-23 | 1975-08-13 | Girling Ltd | Automatic adjuster for an internal shoe drum brake |
| EP0575825A1 (en) * | 1992-06-25 | 1993-12-29 | Lucas Industries Public Limited Company | Automatic adjusting device for a brake, particularly a drum brake |
| CN1196452A (en) * | 1997-04-15 | 1998-10-21 | 卢卡斯工业有限公司 | Unit for drum brake and drum brake equipped with same |
| CN209856283U (en) * | 2019-01-31 | 2019-12-27 | 浙江亚太机电股份有限公司 | Self-adjusting clearance mechanism of bidirectional double-collar shoe brake |
| CN209990821U (en) * | 2019-04-08 | 2020-01-24 | 浙江万安科技股份有限公司 | Self-adjusting shifting piece of drum brake and drum brake |
| CN210050222U (en) * | 2019-04-12 | 2020-02-11 | 靖江市恒大汽车部件制造有限公司 | Self-adjusting crank drum brake |
| CN210661146U (en) * | 2019-10-10 | 2020-06-02 | 无锡晶华汽车制动器有限公司 | Increase formula clearance from moving ahead brake |
| CN113738796A (en) * | 2021-08-31 | 2021-12-03 | 浙江亚太机电股份有限公司 | Brake with thermosensitive plate self-adjusting mechanism assembly |
| CN217502360U (en) * | 2022-06-06 | 2022-09-27 | 南方天合底盘系统有限公司 | Automobile drum brake with self-adjusting mechanism |
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| CN115076266B (en) | 2024-01-30 |
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Address after: 402760 no.9-1, Hongyu Avenue, Bishan District, Chongqing Patentee after: Chenzhi (Chongqing) Brake System Co.,Ltd. Country or region after: China Address before: 402760 No. 9-1, Hongyu Avenue, Chongqing Patentee before: CSGC TRW CHASSIS SYSTEMS CO.,LTD. Country or region before: China |