JPS6337536Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a wheel brake cylinder used in a drum brake mechanism of an automobile, and in particular to a wheel brake cylinder that has the function of always maintaining a constant clearance between a brake drum and a brake shoe, that is, a shoe clearance. This relates to brake cylinders.

Various configurations of conventional wheel brake cylinders of this kind are known, but the one shown in Figures 1 and 2, described in Utility Model Publication No. 50-7424, is one with a simple and compact configuration. There is.
In Figures 1 and 2, 1 is a bucking plate;
2 is a cylinder body, and 3 is a hydraulically operated piston. During braking, this piston 3 slides to the right in FIGS. 1 and 2 due to the hydraulic pressure in the hydraulic pressure chamber 4, and the piston 3
The end of the brake shoe 7 is pushed through the adjustment nut 5 rotatably supported by the adjustment nut 5 and the adjustment bolt 6 screwed into the adjustment nut 5, and the lining 7a of the brake shoe 7 is moved inside the brake drum 8. Press against the surrounding surface. A connecting plate 9, whose one end is interposed between the piston 3 and the ratchet wheel portion 5a of the adjusting nut 5, moves integrally with the piston 3. The cylinder body 2 is formed of a leaf spring material and is connected to the cylinder body 2 by a pivot 10.
The adjustment lever 11 is pivotally connected to the connecting plate 9 so that a tension coil spring 12 tensioned between the adjusting lever 11 and the connecting plate 9 brings the pin 13 fixed to the adjusting lever 11 into contact with the other end contact portion of the connecting plate 9. Therefore, as the piston 3 moves to the right, it rotates counterclockwise in FIG. The pawl 11a of the adjustment lever 11 is engaged with the teeth of the ratchet wheel portion 4a by an elastic force based on a predetermined deflection between the pawl 11a and the pivot shaft 10, and the tension coil spring 12
is accommodated in the window 9a of the connecting plate 9 so as not to apply any force in the vertical direction in FIG. 2 to the pawl 11a of the adjustment lever 11.

During braking, if the shoe clearance a between the lining 7a of the brake shoe 7 and the inner circumferential surface of the brake drum 8 is greater than the set value, the amount of counterclockwise rotation of the adjustment lever 11 in FIG. 1 exceeds the predetermined amount; The adjustment nut 5 is rotated by the engagement of the pawl 11a of the adjustment lever 11 with the teeth of the ratchet wheel portion 5a, and the amount of protrusion of the adjustment bolt 6 relative to the piston 3 is increased, and the shoe clearance a is decreased.
adjusted. When releasing the brake, brake shoe 7
is removed from the brake drum 8 by the return spring 14, the piston 3, adjustment nut 5, adjustment bolt 6, and connecting plate 9 return together, and the adjustment lever 11 rotates clockwise in FIG. At this time, the pawl 11a is attached to the ratchet wheel portion 5.
The tooth surface of a slides.

However, in the conventional device as described above, when the piston 3 moves in the right direction where the shoe clearance a is automatically adjusted, the tension coil spring 12 only performs the function of simply connecting the connecting plate 9 and the adjustment lever 11. Although it has the advantage that it does not adversely affect brake performance because it does not inhibit the rightward movement of piston 3,
Due to the dimensional tolerances of the piston 3, adjustment nut 5, connection plate 9, and adjustment lever 11, the contact position between the pin 13 and the connection plate 9 varies in the left-right direction in FIG. This is doubled and appears as a variation in the position of the claw 11a in the vertical direction in FIG. The pressure contact force between the adjusting nut 5 and the tooth surface of the ratchet wheel portion 5a varies greatly, and this pressure contact force may be too small, which may cause the adjustment lever 11 to rotate idly during braking, or the pressure contact force may be excessive. Therefore, there is a problem that the adjusting nut 5 may be rotated in the opposite direction when the brake is released.

The purpose of this invention is to reduce the pressure contact force between the pawl of the adjustment lever and the teeth of the ratchet wheel of the adjustment nut on each component compared to the conventional system, without increasing the number of parts compared to the conventional system described above. The object is to eliminate the above-mentioned drawbacks by making it less susceptible to the influence of dimensional tolerances.

In order to achieve this objective, the present invention forms the adjustment lever with a rigid body, and the contact portion of the connecting plate and the adjustment lever is set so that the contact area of the tension coil spring is aligned with the line of action of the tension coil spring. The force causes the adjustment lever to be offset so that a moment is applied that presses the pawl against the teeth of the ratchet wheel portion using the contact point as a fulcrum.

With this configuration, the pressure contact force between the claw of the adjustment lever and the teeth of the ratchet wheel portion is determined by the tension of the tension coil spring, the offset amount of the contact point with respect to the line of force of the tension coil spring, and the offset amount of the contact point with respect to the line of action of the tension coil spring. Because it is determined by the distance to the nail,
It is more stable than the conventional one and therefore eliminates the above-mentioned drawbacks.

In conventional systems in which the adjustment lever is made of a leaf spring material, the rotational resistance of the adjustment nut during braking causes flexure in the portion between the pawl of the adjustment lever and the pivot joint. However, in the present invention, since the adjustment lever is a rigid body and hardly causes the above-mentioned deflection, there is an advantage that accurate adjustment of the user clearance can be expected. .

In addition, the tension coil spring has the function of connecting the connecting plate and the adjustment lever, and the function of pressing the claw of the adjustment lever against the teeth of the ratchet wheel with a predetermined pressing force, thereby controlling the movement of the piston when the brake is applied. There is also the advantage that it does not adversely affect braking performance because it does not interfere.

An embodiment of the present invention will be described below with reference to the drawings. Figure 3 shows a 2-leading drum brake mechanism, where 30 is a bucking plate, 31
and 32 are brake shoes, 33 and 34 are brake shoe return springs, 35 and 36 are wheel brake cylinders, and 37 is a brake drum. Wheel brake cylinders 35 and 3
6 are the same, and the wheel brake cylinder 36 will be explained below.

3 to 7, the cylinder body 40 is fixedly attached to the bucking plate 30 and engages with the lower end of the brake shoe 32 through a groove 40a formed at its right end. A piston 42 is slidably fitted into a left-end open cylinder hole 41 of the cylinder body 40.
A hydraulic chamber 43 is formed therein. A shaft portion 45a of an adjustment nut 45 is rotatably fitted into the center hole 44 of the piston 42. The adjusting nut 45 has a ratchet wheel portion 45b that rotates integrally with the shaft portion 45a outside the cylinder body. An adjustment bolt 46 screwed into the adjustment nut 45 has a groove 46a that engages with the lower end of the brake shoe 31.

A rigid adjustment lever 4 is mounted on the cylinder body 40.
7 is pivotally connected by a pivot 48 which is a stepped screw. The first arm portion 47a of the adjustment lever 47 is provided with a pawl 47b that engages with the teeth 45c of the ratchet wheel portion 45b of the adjustment nut 45, and the second arm portion 47c is provided with a spring hook portion 47.
d and a bent portion 47e. A connecting plate 49 having a fork-shaped contact portion 49a at one end so as to sandwich the bent portion 47e is fixed to the piston 42 at the other end. Adjustment lever 47
A tension coil spring 50 is stretched between the spring hanging portion 47d of the connecting lever 49 and the spring hanging portion 49b of the connecting lever 49. As clearly shown in FIG. 7, the line of action A-A of the tension coil spring 50 passes above the contact point between the bent portion 47e of the adjustment lever 47 and the contact portion 49a of the connecting plate 49. Therefore, the tension coil spring 50 acts to bring the bent portion 47e into contact with the abutment portion 49a, and at the same time applies a moment to the adjustment lever 47 to press the pawl 47c against the teeth 45c of the ratchet wheel portion 45b. There is. This moment is F·l (F is the force of the tension coil spring 50).

Next, the action will be explained. During braking, the piston 42 slides to the left in FIGS. 3 and 5 due to the hydraulic pressure supplied from the brake master cylinder (not shown) to the hydraulic pressure chamber 43, and the brake is applied via the adjusting nut 45 and adjusting bolt 46. Push the lower end of the brake shoe 31 in FIG. 3 to the left, and
is pressed against the inner peripheral surface of the brake drum 37 to perform a braking action. At this time, since the connecting plate 49 moves together with the piston 42, the adjusting lever 47 rotates clockwise about the pivot shaft 48 in FIGS. 3 and 4. At this time, if the shoe clearance a between the inner circumferential surface of the brake drum 37 and the lining 31a of the brake shoe 31 is larger than the set value, the piston 42 will slide beyond the set amount, and the adjustment lever 47 will be moved to the set value. Rotate beyond the amount. The rotation of the adjustment lever 47 engages the ratchet wheel portion 4 with the pawl 47c.
5b is rotated, the amount of protrusion of the adjustment bolt 46 screwed into the adjustment nut 45 from the piston 42 increases, and the brake shoe 31
is brought closer to the inner periphery of the brake drum 37, and the shoe clearance a is adjusted to decrease.

Next, when the brake is released, as the hydraulic pressure in the hydraulic chamber 43 decreases, the brake shoe return spring 3
The brake shoe 31 is separated from the inner circumferential surface of the brake drum 37 by the forces of 3 and 34, and the piston 42, adjustment nut 45, adjustment bolt 46, and connecting plate 47 are moved to the right in FIGS. 3, 4, and 5. movement, the adjustment lever 47 rotates counterclockwise around the pivot 48 in FIGS. 3 and 4, the pawl 47c of the adjustment lever 47 slides against the teeth 45c of the ratchet wheel portion 45b, and the pawl 47c rotates against the ratchet wheel portion 45b. engages with the next tooth 45c. The return position of the adjustment lever 47 is between the bent portion 47e of the adjustment lever 47 and the connecting plate 49.
is defined by the contact with the contact portion 49a.

By repeating the above action, the shoe clearance a is adjusted to the set value regardless of the wear of the lining 31a.

During braking, the piston 3 moves further due to the deformation of the brake drum 37 after the shoe clearance a disappears, but when the shoe clearance a disappears, the piston 3 is adjusted by the force transmitted from the piston 42 to the brake shoe 31. The frictional force between the threaded portion of the nut 45 and the adjustment bolt 46 becomes strong, and the adjustment nut 4
5 becomes unable to rotate, and the tension coil spring 5
0 is extended, the adjustment nut 50 is not rotated and over-adjustment is prevented.

In the embodiment described above, the cylinder body 4
Although the cylinder body 40 is fixedly attached to the bucking plate 30 in this embodiment, when the cylinder body 40 is used in a leading/trailing type, the cylinder body 40 may be slidably attached to the bucking plate 30.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the conventional one, Fig. 2 is a sectional view taken along the - line in Fig. 1, Fig. 3 is a diagram showing an embodiment of the present invention, and Fig. 4 shows the main parts of Fig. 3. 5 is a cross-sectional view taken along the line -- in FIG. 4, FIG. 6 is a left side view of FIG. 4, and FIG. 7 is a cross-sectional view taken along the line -- in FIG. 4. 30...Backing plate, 31, 32...
Brake shoe, 35, 36...Wheel brake cylinder, 40...Cylinder body, 2...Piston, 45...Adjustment nut, 46...Adjustment bolt, 47...Adjustment lever, 49...Connection plate, 50
...Tension coil spring.

Claims (1)

[Scope of utility model registration request] A cylinder body attached to the bucking plate, a hydraulically operated piston slidably inserted into the cylinder body, a shaft rotatably fitted into the center hole of the piston, and a shaft outside the cylinder. an adjusting nut having a ratchet wheel portion that rotates integrally with the end portion of the brake shoe; an adjusting bolt that is threadedly engaged with the adjusting nut and is engaged so as not to rotate relative to the end portion of the brake shoe; an adjustment lever which is rotatably rotatable in the circumferential direction of the same axis and tiltable in the axial direction and has a pawl that engages with the teeth of the ratchet wheel portion; a connecting plate having a contact portion capable of contacting the lever; and a tension coil spring stretched between the connecting plate and the adjustment lever so as to bring the contact portion of the connecting plate into contact with the adjustment lever. In the wheel brake cylinder, the adjustment lever is formed of a rigid body, and the contact portion of the connecting plate and the adjustment lever is arranged so that the tension coil spring is in contact with the tension coil spring. A wheel brake cylinder configured to be offset so that a moment is applied to the adjustment lever to press the pawl against the teeth of the ratchet wheel portion using the contact point as a fulcrum.