JPS6021569Y2 - Over-adjustment prevention device for brake operating clearance - Google Patents

Description

[Detailed description of the invention] Industrial field of application This invention relates to a device that prevents excessive adjustment (over-adjustment) in a device that automatically adjusts the operating gap between a brake shoe and a drum by operating a parking brake. For example, it is used in wheel braking devices for transport aircraft.

In conventional drum brakes for vehicles, a pair of brake shoes are spread apart and brought into sliding contact with a rotating drum, thereby suppressing rotation of the drum.

However, as this brake shoe wears, the operating gap between the brake shoe and the drum tonneau increases, so it is necessary to adjust this gap to an appropriate level.
Moreover, it is desirable that this adjustment be performed automatically.

A device that automatically adjusts the operating gap of the brake shoes is such that when a parking lever pivotally connected to one of a pair of brake shoes is rotated, both ends of the parking lever engage the parking lever and the other brake shoe, respectively. The movement of the parking lever is transmitted to the strut and the one brake shoe, which rotates the adjustment lever disposed astride between the one brake shoe and the strut, and the forward movement causes the brake to be applied. A device that automatically adjusts the shoe gap is known.

In this device, the strut is composed of a pair of strut members and a connecting member (adjustment screw) that connects the strut members, and this connecting member is equipped with a star wheel having tooth-shaped meshing parts formed on the outer periphery. is provided, and when this star wheel is rotated, the strut member screwed into the connecting member is projected by a screw action, and the entire strut is extended.

Further, the adjustment lever is pivotally connected to one of the brake shoes and is engaged with an engagement protrusion provided on the strut, and is rotated by the relative movement between the brake shoe and the strut. Due to this rotational movement, the tooth feeding portion provided on the adjustment lever engages with the meshing portion of the star wheel, thereby rotating the star wheel.

However, in this device, the amount of strut extension is
Because it is determined by the rotation angle of the parking lever,
When the rotation angle of the parking lever becomes larger than a predetermined amount, the strut is extended more than necessary, resulting in excessive adjustment of the brake shoe operating gap, so-called over-adjustment.

In other words, when the rotational force of the parking lever is strong, even after the pair of brake shoes slides against the drum, an expanding force acts on the brake shoes, and as a result, the drum etc. are elastically deformed and the parking lever is moved by that amount. As a result, the adjustment lever is rotated excessively, causing the strut to be extended transiently.

As a device to eliminate these drawbacks, the direct engagement between the adjustment lever and the engaging protrusion of the strut is eliminated to eliminate the direct dependence of movement between them, and the engaging protrusion of the strut is A spring is provided between the and adjustment lever, and when the strut and brake shoe are moved relative to each other as the parking lever rotates, the force is transmitted from the strut and the engagement protrusion through the spring. The adjustment lever rotates to rotate the star wheel, but when the brake shoe slides against the drum and the force applied in the axial direction of the strut increases, increasing the rotational resistance of the star wheel, the spring is elastically deformed. It is known to prevent the adjustment lever from rotating by allowing relative movement between the engagement protrusion of the strut and the adjustment lever, thereby avoiding excessive adjustment of the operating gap.

For example, Japanese Patent Laid-Open No. 52-18578 discloses a device similar to the above.

The operating lever 21 or the bell crank-shaped operating lever 1 in that publication corresponds to the parking lever described above.

Problems to be Solved by the Invention However, since a spring is used in the above conventional device, a gap is provided between the retaining protrusion of the strut and the adjustment lever to allow their relative movement. Must-have.

For this reason, foreign objects may get caught in the gap.
In such a case, the relative movement between the retaining protrusion of the strut and the adjustment lever is hindered, resulting in a disadvantage that a sufficient over-adjustment prevention effect cannot be obtained.

In particular, when brakes are used under harsh conditions over a long period of time, foreign matter often occurs inside the drum brake by entering from the outside or peeling off or falling off from inside the drum brake.

Means to Solve the Problems The present invention was made based on this background, and its gist is to provide a parking brake that is pivotally connected to one shoe of a drum brake and the other shoe. A strut is provided between the lever and the strut, and the strut is configured to be adjustable in length by an adjustment screw having a star wheel, and the strut is rotatably attached to the one shoe and meshes with the star wheel. an adjustment lever having a tooth feed portion and a portion of which is engaged with an engagement protrusion of the strut, and the rotational movement for expanding the shoe of the parking lever is caused by the engagement of the strut. A brake shoe of a type in which the transmission is transmitted to the adjustment lever via a protrusion, and the forward movement of the adjustment lever rotates the star wheel to extend the strut, thereby automatically adjusting the operating gap of the brake shoe. In the working gap adjustment device, normally the movement of the strut is transmitted to the adjustment lever, but when the rotational resistance of the star wheel increases and exceeds a certain value, it is elastically deformed and the strut moves against the adjustment lever. The adjustment lever and the engaging protrusion of the strut are engaged with each other while constantly sandwiching a motion transmission limiting device having a rubber portion having elastic properties that allow relative movement.

In this manner, motion is normally transmitted from the retaining protrusion of the strut to the adjustment lever via the motion transmission limiting device, so that the adjustment lever is rotated as the parking lever is rotated.

However, when the brake shoes come into contact with the drum and the rotational resistance of the star wheel increases, the elastic deformation of the motion transmission limiting device allows relative movement between the strut's engagement protrusion and the adjustment lever. The rotation of the adjustment lever is restricted and over-adjustment is prevented.

That is, the transmission of motion to the adjustment lever after the brake shoe contacts the drum is suppressed.

Here, since the above action is permitted by deformation of the motion transmission limiting device inserted between the engagement protrusion of the strut and the adjustment lever, the engagement protrusion of the strut and the adjustment lever are This prevents foreign objects from getting caught in between.

EXAMPLES Hereinafter, the present invention will be explained in more detail based on examples shown in the drawings.

1 is a backing plate, this backing plate 1
A wheel cylinder 2 and an anchor block 3 are fixed on the top, and a pair of arc-shaped brake shoes 4 and 5 are mounted between them.

The brake shoes 4 and 5 are always urged in the direction of contraction (the direction in which the pair of brake shoes approach each other) by tension springs 6 and 7.

A strut 10 is placed between two notches 4a and 5a provided at opposing positions inside the pair of brake shoes 4.
is installed to prevent the pair of brake shoes 4.5 from contracting beyond a certain level.

As shown in FIG. 2, the strut 10 is composed of first and second strut members 11, 12 and a connecting member (adjustment screw) 13 that connects them.

The first strut member 11 has a brake shoe 4 at one end.
It has a rectangular notch 11a that engages with
1b.

On the other hand, the second strut member 12 has a rectangular notch 12a that engages with the brake shoe 5 at one end, and a round hole 12b at the other end.

The second strut member 12 also has a retaining projection 21 projecting at right angles to the longitudinal direction.

The connecting member 13 is a rod-shaped body with a circular cross section, and one end has a female thread 13b and is screwed into the female thread 11b of the first strut member 11, and the other end is connected to the second strut member 12. It is fitted into the round hole 12b.

As shown in FIG. 3, a circular star wheel 15 having tooth-shaped meshing portions 14 on its circumferential surface is formed integrally with the connecting member 13 at the intermediate portion of the connecting member 13.
When the connecting member 13 is integrally rotated by the rotation of the star wheel 15, the first strut member 11 is pushed out by a screw action, and the strut 10 is expanded.

A parking lever 16 is attached to the one brake shoe 5.
and an adjustment lever 17 are pivotally connected by the same pin 18.

The parking lever 16 is connected to the second parking lever along with the brake shoe 5.
When the parking lever 16 is rotated in the brake operation direction, that is, in the counterclockwise direction in FIG. 1, the strut 10 is moved to the right in the figure. The brake shoe 4 is brought into sliding contact with the drum 19, and the other brake shoe 5 is moved due to the reaction, and the brake shoe 4 is brought into sliding contact with the drum 19.
It is designed so that it can be brought into sliding contact with 9.

The adjustment lever 17 is connected to the second strut member 1
The through hole 2 into which the locking protrusion 21 provided in the hole 2 should be loosely fitted
7, and a tooth feed portion 22 for rotating the star wheel 15 at the side end, and is constantly biased clockwise by a tension spring 23 whose one end is locked to the brake shoe 5. The tooth feed portion 22 is pressed against the meshing surface of the star wheel 15.

As shown in FIG. 3, the tooth feeding portion 22 has a rectangular cross section, and normally does not mesh with the meshing portion 14 of the star wheel, but when the amount of rotation of the adjustment lever 17 increases beyond a certain value, Its tip end surface meshes with the tooth surface of the meshing portion 14, causing the star wheel 15 to rotate.

A bushing 26 as a motion transmission limiting device consisting of a cylindrical rubber portion 24 and an outer cylinder 25 is attached to the engagement protrusion 21 of the second strut member 12. The projection 21 and the inner peripheral edge of the through hole 27 of the adjustment lever 17 are engaged with each other without any gap.

That is, the bushing 26 is always held between the engaging protrusion 21 and the adjusting lever 17.

The spring constant (elastic property) of the rubber portion 24 is such that when the rotational resistance of the star wheel 15 is small and the rotational resistance of the adjustment lever 17 is small, it hardly undergoes elastic deformation, and the tensile force in the axial direction of the strut 10 increases. The rotation resistance of the star wheel 15, that is, the adjustment lever 17
The rubber part 24 is designed to be elastically deformed when the rotational resistance increases and exceeds a certain value, and if necessary, the rubber part 24
A preload is applied to the cylinder to bring it into a preloaded state.

Therefore, although the motion of the strut 10 is normally transmitted to the adjustment lever 17, when the star wheel rotational resistance increases, the motion transmission is almost cut off.

To explain the operation of the above device having the above configuration,
When the parking lever 16 is rotated to operate the brake, the pair of brake shoes 4.degree. 5 are expanded and come into sliding contact with the drum 19, thereby suppressing the rotation of the drum 19.

At this time, the rotational force of the parking lever 16 acting on the strut 10 at the contact portion between the through hole 27 and the bush 26 is transmitted to the adjustment lever 17 via the bush 26.

The rotational force of the parking lever 16 is also transmitted via the brake shoe 5, and therefore the rotational force acts on the adjustment lever 17 in the counterclockwise direction in FIG. When the gap between the adjusting lever 17 and the tooth feeding portion 22 of the adjusting lever 17 is appropriate, the tooth feeding portion 22 of the adjusting lever 17 does not mesh with the tooth surface of the engaging portion 14 of the star wheel 15. Therefore, the rotational resistance of the adjusting lever 17 based on the rotational resistance of the star wheel 15 is Does not occur.

Therefore, the movement of the strut 10 is directly transmitted through the bushing 26 without deforming the rubber portion 24, and the adjustment lever 17 is rotated.

Next, when the brake shoes 4 and 5 wear out and the operating gap increases, the amount of movement of the brake shoes 4.5 and the strut 10, that is, the amount of rotation of the adjustment lever 17 increases, so the tooth feed portion 22 increases. star wheel 1
Since the rotation resistance of the star wheel 15 is small until the brake shoes 4 and 5 come into sliding contact with the drum, the movement of the strut 10 hardly deforms the rubber part 24 and moves the bush 26. The signal is transmitted to the adjustment lever 17 via the signal.

Then, the adjustment lever 17 rotates, rotates the star wheel 15, extends the strut 10, and adjusts the operating gap between the brake shoes 4 and 5.

At this time, in order to obtain strong braking force, press the parking lever 1.
When the brake shoes 6 are rotated with a strong force, a strong spreading force is applied to the brake shoes 4 and 5 even after they have slid into contact with the drum 19, but along with this, a thrust force is generated in the axial direction of the strut 10. As a result, the rotational resistance of the star wheel 15 increases, and along with this, the adjustment lever 1
7 rotation resistance increases.

When the rotational resistance of the adjustment lever 17 increases, the rubber portion 24 of the bushing 26 is elastically deformed, allowing relative movement between the engagement protrusion 21 of the strut 10 and the adjustment lever 17. Motion is no longer transmitted.

Therefore, even if the brake shoes 4, 5 and the strut 10 move by an amount corresponding to the elastic deformation of the drum 19 etc. based on this elastic deformation, the strut 10 is not extended any further and the brake shoes 4, 5 The operating clearance of is maintained properly.

Here, since the locking protrusion 21 of the strut 10 and the adjustment lever 17 are engaged with each other through the bushing 26 without a gap, it is easy to cause damage to the drum brake due to long-term use under harsh conditions. Foreign matter will not be caught between the retaining protrusion 21 and the adjustment lever 17 and their relative movement will not be inhibited.

In other words, the inhibition of the overadjustment prevention effect is suitably eliminated.

Furthermore, according to this embodiment, the bushing 26 is used to allow relative movement between the engagement protrusion 21 of the strut 10 and the adjustment lever 17 when the rotational resistance of the star wheel 15 increases. This has the advantage of requiring less space than the conventional case using springs.

Further, according to this embodiment, an annular groove is formed on the outer peripheral surface of the outer cylinder 25 of the bushing 26, and a part of the inner peripheral edge of the through hole 27 of the adjustment lever 17 is engaged in the groove. Since the engaging protrusion 21 and the adjusting lever 1
There is an advantage that displacement of the engagement protrusion 21 from the engagement protrusion 7 in the axial direction is prevented.

Effects of the invention As is clear from the above explanation, the brake shoe operating gap over-adjustment prevention device of the invention has the following effects:
In order to allow relative movement between the engagement protrusion of the strut and the adjustment lever when the rotational resistance of the star wheel increases, a bushing as a motion transmission limiting device is inserted between them. Compared to the case where a spring is used, it is completely eliminated that the over-adjustment prevention function is inhibited due to foreign objects being caught between the retaining protrusion and the adjustment lever.

Moreover, the required space is smaller than when using a spring, making the design easier.

[Brief explanation of drawings]

Fig. 1 is a front view of a drum brake device including the device of the present invention, Fig. 2 is a sectional view taken along ■-■ in Fig. 1, Fig. 3 is a sectional view taken along -■ in Fig. 2, and Fig. 4 is a sectional view taken along 1 and 2 are enlarged cross-sectional views showing essential parts of the adjustment lever and strut, and FIG. 5 is a cross-sectional view taken along the line -■ in FIG. 4. 4.5 Nibrake shoe 10 = Strut, 14: Engagement part, 15 Nistar wheel, 16: Parking lever, 17: Adjust lever, 21: Engagement protrusion, 22: Tooth feed part, 24: Rubber part, 25: Outer cylinder, 26: Push (
motion transmission limiter).

Claims (1)

[Claim for Utility Model Registration] A hook is provided between one shoe of a drum brake and a parking lever pivotally connected to the other shoe, and the length can be adjusted by an adjustment screw having a star wheel. an adjustment lever which is rotatably attached to the other shoe and has a gearing portion that meshes with the star wheel and is partially engaged with a retaining protrusion of the strut; a rotational movement of the parking lever for expanding the shoe is transmitted to the adjustment lever via a retaining protrusion of the strut, and the forward movement of the adjustment lever rotates the star wheel. In a brake shoe operating clearance adjusting device of the type in which the strut is extended and the operating clearance of the brake shoes is automatically adjusted, the movement of the strut is normally transmitted to the adjustment lever, but the rotation of the star wheel is A motion transmission limiting device having a rubber portion having an elastic property that elastically deforms when resistance increases and exceeds a certain value to permit relative movement of the strut engagement protrusion with respect to the adjustment lever is always held in the pinched state. The brake shoe actuation is characterized in that the adjustment lever and the engaging protrusion of the strut are engaged with each other to suppress motion transmission of the adjustment lever after the brake shoe contacts the drum. Gap over-adjustment prevention device.