JPH0143176B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic adjustment device equipped with a ratchet mechanism for always maintaining a constant gap between a brake drum and a brake shoe.

Conventionally known devices of this kind have independent means for sensing the linear movement of the adjusting nut, that is, the amount of movement of the shoe corresponding to wear of the lining, and means for converting this into rotational movement. In most cases, by rotating the adjusting nut, the adjusting bolt that supports one end of the shoe is automatically unscrewed in accordance with the wear of the lining. However, with this method, the force structure is complicated and space constraints are large, and the number of parts increases, which increases the number of malfunctions due to wear and sticking of various parts, and requires precision parts. There were problems such as high machining accuracy required and high costs. There is also a known system in which the means for sensing the amount of shoe movement corresponding to the wear of the lining and the means for converting this into a rotational movement are implemented in a single component; Since they are spaced apart in a direction perpendicular to the axial direction of the member, there is a large space restriction, and furthermore, when an excessive load is applied to the rotating member, the elastic deformation of the member itself is sufficient to prevent escape. This means that the design of the means is extremely difficult, and there are problems such as over-adjustment due to variations in manufacturing tolerances, or incorrect adjustment due to backtracking of the rotating member.

The present invention solves this problem, and one embodiment thereof will be described in detail below with reference to the drawings. Figures 1 and 2 show a two-leading (2L) type drum brake with automatic adjustment, and 1 is a brake drum that rotates together with the wheels (not shown). Reference numeral 2 indicates a back plate fixed to the vehicle body side, 3a and 3b indicate a pair of opposing brake shoes movably mounted on the back plate 2, and 4
A and 4b are linings attached to the outer periphery of each shoe. Reference numerals 5a and 5b are wheel cylinders with one end open, which are fastened to the back plate 2 with bolts or the like, and their construction will be explained in detail with reference to FIG. One side of an adjustment nut 7 is rotatably and slidably fitted into a bottomed opening hole 6a provided in one side of the body 6 of the cylinder 5a, and normally the rear end surface 7a abuts against the bottom surface 6b of the opening hole 6a. are doing. A flange 7b is formed on the adjusting nut 7 on the side protruding from the opening hole 6a of the body 6 at a distance from one end edge 6c of the body 6, and the periphery of the flange 7b has a serrated shape as shown in FIG. Adjustment teeth 7c are carved.

The configuration described above is not limited to this, and for example, a flange having an outer diameter larger than the diameter of the opening hole 6a that abuts one end edge 6c of the body 6 may be formed on the adjustment nut 7, and the rear end surface 7a of the adjustment nut 7 and the opening hole may be formed. Bottom surface 6b of 6a
A space may be provided between the two. Reference numeral 8 denotes an adjustment bolt, and one end of the shoe 3a is fitted into a groove 8b provided in the head 8a, and a threaded portion 8c is screwed into the internal thread 7d of the adjustment nut 7. A groove 6d is provided at the other end of the body 6, into which one end of the shoe 3b is fitted. A liquid chamber 9 communicates with a master cylinder (not shown) through a passage 10. A piston cup 11 is fitted into an annular groove formed in the adjusting nut 7 to prevent liquid from leaking from the outer periphery of the adjusting nut 7. 12 is a dust boot with opening hole 6a
In order to prevent muddy water, dust, etc. from entering the inside, the adjustment nut 7 and the body 6 are fitted into respective annular grooves provided therein. Reference numeral 13 denotes an adjustment lever that is inclined with respect to the rectilinear direction of the adjustment nut 7 in FIG. Claw portion 13a
The tip portion 1 extends from the top and is bent at a substantially right angle.
A spherical projection 13c is provided on the flange 3b, and the tip of the projection 13c abuts against the front end surface 7e of the flange 7b. On the other hand, the other side of the adjustment lever 13 has a long hole 13d.
is drilled in the body 6, and is rotatable about a pin 14 implanted in the body 6, and is fixed with a washer 15 and an E-ring 16 with some play in the axial direction. Reference numeral 17 denotes an adjustment spring stretched between a locking hole 13e drilled on one side of the adjustment lever 13 and a pin 18 implanted near the axis of the opening hole 6a of the body 6, and its coil portion is attached to the middle part of the adjustment lever 13. The hook 17a, which is housed in a rectangular hole 13f formed in the coil section and hooked onto the pin 18, is eccentric from the center of the coil section toward the body 6, as shown in FIG. Therefore, the long hole 13d of the constant adjustment lever 13 is a rectangular hole 1.
In addition, the spherical protrusion 13c on one side is urged in the direction of pushing back the adjustment nut 7 so that the 3f side abuts against the pin 14 (see wheel cylinder 5b in FIG. 1), and the claw portion 13a engages the adjustment tooth 7c. It is given a biasing force so as to match. 19a,1
Reference numeral 9b denotes a shoe return spring that draws the shoes 3a, 3b inward, and ring members 20a, 20b for preventing resonance are wound around the outer periphery of the coil. At one end of the ring members 20a, 20b, a shoe 3a,
A slit fitted into a portion of 3b is provided, and the rotation of the slit is regulated and the spring 1
The movement in the length direction of 9a, 19b is between the slit bottom and the inner end surface of the shoe in one direction, and the ring member 2 in the other direction.
It is regulated by the end faces 0a and 20b and the inner end face of the shoe.

Reference numerals 21a and 21b are holding mechanisms that lightly press and hold the shoes 3a and 3b against the back plate 2. Brake operation with the above configuration will be explained. When pressurized fluid is fed from a master cylinder (not shown) to the fluid chamber 9 of the wheel cylinder 5a, the adjustment nut 7, adjustment bolt 8, brake shoe 3a, etc. are almost integrated to release the shoe return spring 19.
a, 19b, etc., moves to the left in FIG. 2, presses the lining 4a against the rotating brake drum 1, and brakes it. At this time, since the adjustment lever 13 is preliminarily applied with tension in the direction of pulling back the adjustment nut 7, it rotates counterclockwise in FIG. 1 about the pin 14 as a fulcrum. That is, the actual effective length of the adjustment lever 13 is between the long hole 13d and the pin 1.
4 and the tip of the spherical protrusion 13c and the contact portion of the front end surface 7e of the flange 7b of the adjusting nut 7, in other words, the straight line length L of both the contact portions parallel to the plane of the drawing 1 is determined. Therefore, the adjustment lever 13 rotates counterclockwise to absorb the distance increase corresponding to the advance of the adjustment nut 7. Therefore, when the lining 4a is now worn and the amount of rotation of the claw portion 13a is larger than the pitch p of the adjustment teeth shown in FIG. 3, the adjustment teeth 7c are rotated in the α direction. The adjusting bolt 8 is prevented from rotating because one end of the shoe 3a is fitted into the groove 8b, and the adjusting bolt 8 is screwed out to the left in FIG. This is to adjust the gap 4a to an appropriate value. When the lining 4a starts to come into contact with the brake drum 1 during brake operation, the reaction force acts on the adjustment bolt 8 and the adjustment nut 7 stops rotating, but the adjustment lever 13 resists the adjustment spring 17. Since the elongated hole 13d can move along the pin 14, damage to parts is prevented and the brake drum 1
Even if such deformation occurs and the adjusting nut 7 advances further, the adjusting operation is not performed, and so-called over-adjustment can be prevented.

Next, when the brake is released, the shoe 3a etc. are moved to the adjustment lever 1 by the shoe return springs 19a, 19b.
3 are returned to substantially the state before operation by the adjustment spring 17. At this time, the shoe return springs 19a, 19
The rotational frictional force of the adjusting nut 7, which is the sum of the frictional force of the threaded portion of the internal thread 7d caused by b and the frictional force due to the piston cup 11, is the frictional force due to the pressing force of the claw portion 13a, and the contact point between the spherical projection 13c and the flange 7b. If the rotational frictional force is set to be larger than the rotational frictional force including the frictional force with Between the spherical protrusion 13c and the flange 7b, there is a corrosion-resistant material such as polytetra-fluoro-ethylene material,
Moreover, if an intervening material with a low coefficient of friction is used, long-term reliability will be further improved.

In the above, only the shoe 3a side has been explained, but the structure and operation of the shoe 3b side will be explained because the wheel cylinder 5a etc. are arranged in exactly the same way as shown in FIG. 1 with the wheel cylinder 5a rotated 180 degrees. omitted. Figures 5 and 6 show that the collision part for sensing the amount of shoe movement corresponding to the wear of the lining does not collide with the adjustment nut, so as not to generate rotational friction force in the direction of the adjustment nut slipping back. In this embodiment, the same reference numerals as in FIGS. 1 and 2 indicate corresponding parts. That is, the adjustment bolt 8 that supports one end of the shoe 3a and the adjustment nut 7 that screws the bolt 8 are connected to the bottomed hole 30 of the piston 30.
a, and the rear end surface 7a abuts against the bottom surface 30b of the bottomed hole 30a. The adjustment nut 7 protruding from the bottomed hole 30a has a flange 7.
b is formed, and serrated adjustment teeth 7c are carved on the periphery thereof. The inner threaded hole 7d of the adjustment nut 7 is a through hole in consideration of workability so that cutting debris does not accumulate therein, but it may be a hole with a bottom. One side of the piston 30 is smoothly fitted into the bottomed opening hole 6a of the body 6, and the rear end surface 30c normally abuts against the bottom surface 6b. Further, a flange 30d is formed on the side of the piston 30 protruding from the opening hole 6a at a distance from one end edge 6c of the body 6. Furthermore, a key groove 30e parallel to the axial direction is provided in the intermediate portion of the piston 30 fitted into the opening hole 6a, and the tip of a stud 31 implanted in the body 6 is fitted into the key groove 30e. , so piston 3
0 is allowed to move forward and backward, but rotation is restricted. On one side of the adjustment lever 13, the claw portion 13a' of the folded portion bent into a substantially U shape engages with the adjustment tooth 7c of the adjustment nut 7, and the R-shaped tip portion 13c' engages with the flange 30d of the piston 30. It is always in contact with the front end surface 30f of. Adjustment lever 1
3 and the structure of the adjustment spring 17 are the same as in the previous embodiment.

Therefore, the automatic adjustment operation according to this embodiment is omitted as in the previous embodiment, but as is clear from the above structure, when the brake is released, the R-shaped tip 13c' of the adjustment spring 17 comes into contact with the flange 30d. Since the rotational frictional force between the surfaces is not transmitted to the adjusting nut 7, there is a method that can reliably prevent the adjusting nut 7 from slipping back.

Further, the present adjustment device is not limited to the above two embodiments, but, for example, as shown in FIG. It can also be applied to a leading-trailing (LT) type brake in which the lower wheel cylinder 5b serves as a fixed anchor member.
Furthermore, it is clear that the invention can also be applied to dual-to-leading (D2L) type brakes. still,
In the above-described embodiment, the adjustment operation is performed when the brake is applied, but FIGS. 7 and 8 schematically show the adjustment operation performed when the brake is released.

Numeral 7c is an adjustment tooth carved on the periphery of the flange 7b of the adjustment nut 7, and has a sawtooth shape in the opposite direction to the adjustment tooth shown in FIG. One side of the adjustment lever 13, which is inclined in the advancing direction of the adjustment nut 7, that is, in the direction of arrow A, is provided with a slit or the like.
The claw part 13a of one part is engaged with the adjustment tooth 7c, and the other part is bent at a substantially right angle and has a spherical protrusion 13c provided at the tip part 13b.
The tip thereof is in contact with the front end surface 31a of the insert material 31 made of polytetrafluoroethylene material or the like. On the other hand, the other side of the adjustment lever 13 is formed in a fork shape,
On the other hand, the inner surface of the elongated notched hole 13d abuts against the pin 14. The position of the adjustment lever 13 at all times is maintained by a locking hole 13e formed on one side of the adjustment lever 13 and an adjustment spring 17 stretched between a fixed member. When the adjusting nut 7 moves forward in the direction of arrow A, the adjusting lever 13 moves between the tip of the spherical protrusion 13c and the front end surface 3 of the insert 31.
The contact surface with 1a slides relatively, and the adjustment lever 13 rotates counterclockwise. If the lining is now worn and the amount of rotation of the pawl 13a of the adjustment lever 13 is greater than one pitch of the adjustment tooth 7c, the pawl 13a engages with the next new adjustment tooth 7c. Next, when the brake is released, tension in the direction of the arrow β is applied to the adjustment lever 13 by the adjustment spring 17, so the adjustment nut 7 is turned and the adjustment bolt supporting one end of the shoe is unscrewed. This is to adjust the gap between the brake drum and the lining to an appropriate value.

The present invention has the following many effects due to the above-described configuration.

It is compact because it has a means for sensing the amount of movement of the shoe corresponding to the wear of the lining and a means for converting this into rotational movement in a single part, and can be installed in extremely close positions.
Therefore, it is advantageous in terms of space and can also be applied to small brakes.

As described above, since the structure is simple, it is possible to reduce the causes of malfunction and is inexpensive.

When an excessive load is applied to the adjustment nut 7, the shock absorber (adjustment spring 17) acts, thereby preventing damage to parts and over-adjustment.

When assembling the brake drum, the outer diameter of the brake shoe is made small in advance to facilitate assembly work. Therefore, the initial gap between the drum and the shoe during brake inspection and maintenance is considerably larger than the usual gap. Even if the brakes are activated under such conditions, it is easy to design a brake system that can sufficiently absorb the movement without damaging the components, and that can also reliably return to its original normal state.

[Brief explanation of drawings]

FIG. 1 is a plan view of a drum brake showing an embodiment of the device of the present invention, FIG. 2 is a sectional view taken from FIG. 1, FIG. 3 is a sectional view taken from FIG. 2, and FIG. 4 is a sectional view taken from FIG. FIG. 5 is a partial plan view showing another embodiment according to the present invention, FIG. 6 is a cross-sectional view taken from FIG. 5, and FIG. 7 is a schematic plan view showing still another embodiment according to the present invention. , FIG. 8 is a left side view showing a portion of FIG. 7. 1... Brake drum, 3a, 3b... Brake shoe, 4a, 4b... Lining, 5a, 5
b...Wheel cylinder, 6...Body, 6a
... Opening hole, 7 ... Adjustment nut, 7b ... Flange, 7c ... Adjustment tooth, 7e ... Front end surface, 8 ... Adjustment bolt, 13 ... Adjustment lever, 13a, 13
a'...Claw part, 13c...Spherical projection, 13c'...R
17...adjustment spring, 30...piston, 31...intervening material.

Claims (1)

[Claims] 1. In a drum brake having at least one adjustment device consisting of an adjustment bolt for always maintaining a constant gap between the brake drum and the brake shoe and an adjustment nut into which the bolt is screwed, One side of the adjustment lever, which is arranged at an angle, engages adjustment teeth carved on the periphery of the flange of the adjustment nut, and when the brake is applied, a part of one side of the adjustment lever is always aligned in the straight direction of the adjustment teeth and The adjustment lever is brought into contact with the front end surface of the flange having the adjustment teeth so as to follow the rotation direction, and a pretension is always applied so that the other side of the adjustment lever hits the fixed member, and an excessive force is applied to the adjustment teeth. An automatic adjustment device for a drum brake, characterized in that it is equipped with a spring means that also acts as a buffer when a load is applied.