JPS628440Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a drum brake used in vehicles such as automobiles, and particularly relates to a drum brake equipped with a parking brake mechanism.

Drum brakes used in vehicles such as automobiles generally include a drum that is integrally connected to an axle, a bucking plate that is fixed to a fixed member of the vehicle, and a drum brake that is fixed to the bucking plate and whose fluid pressure is controlled. a wheel cylinder that is extendable and retractable; and a second position provided within the drum, connected to the wheel cylinder at one end, pivoted to a bucking plate at the other end, and abutting the drum from the first position by the wheel cylinder. The wheel includes a pair of brake shoes that perform a braking action by being pivoted toward the wheel, and a brake pedal that controls fluid pressure in the wheel cylinder. One such drum brake is equipped with a parking brake mechanism configured to temporarily cause the drum brake to function as a parking brake by maintaining the hydraulic pressure in the hydraulic line of the service brake at a high pressure at which the brake is activated. drum brakes are known.

However, in conventional drum brakes equipped with such a parking brake mechanism, when the drum brake is used as a parking brake, the hydraulic pressure in the hydraulic line is maintained at a high pressure in the brake operating state. Each member must be constructed with extremely liquid-tight materials, and if the oil pressure in the hydraulic line is maintained at high pressure for a long time, there is a risk that the oil pressure will drop due to hydraulic oil leaks, etc. Therefore, the reliability of a drum brake equipped with such a parking brake mechanism is inferior to that of a mechanical parking brake. Furthermore, in the drum brake equipped with the conventional parking brake mechanism as described above, the hydraulic line for the drum brake as a service brake and the hydraulic line for operating the parking brake mechanism are shared, so the hydraulic line for operating the parking brake mechanism is shared. There is a problem in that the drum brake and the parking brake mechanism cannot be operated or deactivated independently of each other.

In view of the above-mentioned problems with conventional drum brakes equipped with a parking brake mechanism, the present invention is a drum brake equipped with a parking brake mechanism, which does not depend on the hydraulic pressure of the hydraulic line of the drum brake used as a regular brake. First, it is an object of the present invention to provide an improved drum brake that can be used as a highly reliable parking brake for a long period of time.

This purpose, according to the present invention, includes a drum integrally connected to the axle, a bucking plate fixed to a fixed member of the vehicle, and a drum that is fixed to the bucking plate and expands and contracts by controlling fluid pressure. a second wheel cylinder provided within the drum, connected to the wheel cylinder at one end, pivoted to the bucking plate at the other end, and abutting the drum from a first position by the wheel cylinder; a pair of brake shoes that perform a braking action by being pivoted to the position;
a brake pedal that controls the fluid pressure of the wheel cylinder; and a pair of levers that are pivoted at one end at an intermediate portion between the one end and the other end of each of the brake shoes, and that extend along the axis thereof. a lever having an elongated hole that extends along the length of the lever and whose width linearly increases toward the other end; and a cone that is commonly inserted through the elongated holes of the pair of levers and is movable reciprocally along its axis. and means for controlling the axial position of the cone relative to the pair of levers,
This is achieved by a drum brake configured to hold the pair of brake shoes in the second position by driving the cone axially into engagement with the elongated hole.

According to the drum brake according to the present invention, the pair of brake shoes can be held in the second position by driving the cone in the axial direction and engaging the elongated hole of the pair of levers. Therefore, once the brake pedal is depressed to extend the wheel cylinder and pivot the pair of brake shoes to the second position, the cone is driven in its axial direction to engage the elongated hole in the lever. According to
Since the pair of brake shoes can be mechanically held in the second position regardless of the hydraulic pressure in the hydraulic line connected to the wheel cylinder, this brake system is compared to a drum brake equipped with a conventional parking brake mechanism. It is possible to reliably perform the function as a parking brake for a long time.

In one embodiment of the present invention, the main part of the means for controlling the axial position of the cone relative to the pair of levers is incorporated into the brake pedal, so that the parking brake mechanism of the drum brake can be operated with only one foot. The cone can be easily manipulated without requiring extra space for providing means for controlling the axial position of the cone.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a longitudinal sectional view showing one embodiment of a drum brake according to the present invention configured as a leading trailing (LT) brake, and FIG.
FIG. 3 is an enlarged partial cross-sectional view taken along line - in the figure, and FIG. 3 is a side view showing a brake pedal provided in the vehicle interior.

In these figures, reference numeral 1 designates a drum that is integrally connected to the axle 2 and rotates together with the axle 2 about its axis 3. One side of the drum 1 (the rear side in FIG. 1) is connected to a fixed member of the vehicle by a connecting member not shown in the figure, and an axle 2 is inserted into the center with a loose fit. A disc-shaped backing plate 5 having holes 4 is provided.

The wheel cylinder 6 is attached to the bucking plate 5.
is fixed, and the wheel cylinder 6 is configured such that the length between the tips of two piston rods 7 and 8, which are provided facing each other, expands and contracts by controlling the internal hydraulic pressure. Also, a pair of brake shoes 9 and 10 are provided on the bucking plate 5 within the drum 1. The brake shoes 9 and 10 are arcuate, and brake linings 11 and 12 are integrally fixed to their radially outer surfaces, respectively. The brake shoes 9 and 10 also connect the piston rod 7 of the wheel cylinder 6 at one end 13 and 14, respectively.
and 8, and is pivotally supported at the other ends 15 and 16 to the bucking plate 5 via anchor pins 17.

Furthermore, the brake shoes 9 and 10 are pivotally biased about the anchor pin 17 towards the first position shown in FIG. 1 away from the drum 1 by two return springs 18 and 19, and Return spring 1 due to expansion of cylinder 6
The brake linings 11 and 12 are driven against the spring forces of the drums 8 and 19 to the second position where they come into contact with and frictionally engage with the inner peripheral surface of the drum 1, thereby performing a braking action. There is. The inside of the wheel cylinder 6 is driven by a brake tube (not shown) to a brake pedal 21 provided inside the vehicle via a proportioning valve, a master cylinder, a vacuum servo, and a link 20 (also not shown). As a result, the depression input applied to the brake pedal 21 is converted into hydraulic pressure by the vacuum servo and the master cylinder, and the hydraulic pressure is guided into the inside of the wheel cylinder 6. One end 13 and 1 of brake shoes 9 and 10
4 and the other ends 15 and 16, a pair of levers 26 and 27 are pivotally mounted at one end 22 and 23 by pivots 24 and 25, respectively.
The levers 26 and 27 respectively have elongated holes 30 and 31 extending along their axes and increasing linearly in width towards the other ends 28 and 29. Conical bodies 3 are provided in the elongated holes 30 and 31 of the levers 26 and 27 so as to be able to reciprocate along the axis 31a.
2 are inserted in common.

The large diameter end 33 of the cone 32 is connected to the levers 26 and 2.
7 has a diameter larger than the maximum width of the elongated holes 30 and 31, and its small diameter end 34 is fixed to the bucking plate 5 so that the levers 26 and 27 are driven to the right as viewed in FIG. It extends into the cap 35 through a hole 36 in the cap 35 which prevents this from occurring. Further, at the small diameter end 34 of the cone 32, there is a means 37 for controlling the relative position of the cone in the direction of the axis 31a with respect to the pair of levers 26 and 27.
(See Figure 3) One end 3 of the inner cable 38
It is connected to 9. In the illustrated embodiment, a ball 40 having a diameter larger than the diameter of the through hole formed in the small diameter end 34 is fixed to one end of the inner cable 38, and the ball 40 is attached to the axis 31 of the cone 32.
The axis 3 is located in the large diameter hole 41a provided along the axis a.
It is arranged so as to be able to reciprocate along 1a. A compression coil spring 43 is interposed between the small diameter end 34 of the conical body 32 and the bucking plate 5 via spring seats 41 and 42, respectively, so that the conical body 32 can be rotated as shown in FIG. It is biased to the left.

means 3 for controlling the relative position of the cone 32 with respect to the pair of levers 26 and 27 in the direction of the axis 31a;
In this embodiment, the main part of 7 is incorporated into the brake pedal 21, as shown in detail in FIG. The brake pedal 21 consists of a pedal lever 45 which is pivotally supported at one end by a pivot shaft 44 to the vehicle body (not shown), and a pedal 47 which is pivotally supported by a pivot shaft 46 at the other end of the pedal lever 45. A tread portion 49 covered with a rubber cover 48 is integrally provided at one end of the pedal 47 and is operated by the driver's foot.
The other end 51 of the inner cable 38, which is connected to the cone body 32 at one end 39, is pivotally attached to the other end 50. The pedal 47 also has ratchet teeth 52 along an arc line extending around the center line of the pivot shaft 46.
are provided, and a ratchet pawl 53 engages with the ratchet tooth 52 in a non-returning manner. The ratchet pawl 53 is always biased by a compression coil spring (not shown) in a direction in which it engages with the ratchet tooth 52 in a non-returning manner, and the inner cable 5
4 is connected to an operation knob 56 provided on an instrument panel 55, and the operation knob 56
3, the position of engagement with the ratchet tooth 52 shown in FIG.
and a position where the engagement is released.

In operation, when the drum brake is used as a service brake, the brake pedal 21
3, the pedal 47 is depressed, the pedal lever 45 is pivoted clockwise in FIG. The stepping force is converted into hydraulic pressure by the vacuum servo and the master cylinder, which are not connected to each other, and the increased hydraulic pressure is guided into the wheel cylinder 6, which drives the piston rods 7 and 8 away from each other, thereby driving the brake shoe 9. and 10 is anchor pin 1
7 and thereby pivot the respective brake linings 11 and 12 away from each other.
By being pressed against the drum 1, a braking force is applied to an axle (not shown).

Conversely, when the brake pedal 21 is released from the pedal 47, the hydraulic pressure in the wheel cylinder 6 is reduced and the brake shoes 9 and 10 are pivoted toward each other around the anchor pin 17, thereby causing each The frictional engagement of the brake linings 11 and 12 with the drum 1 is released.

Further, when the drum brake according to the illustrated embodiment is used as a parking brake, the brake shoes 9 and 10 are moved to the anchor pin 17 by first depressing the pedal 47 of the brake pedal 21, as in the case where it is used as a service brake described above. The brake linings 11 and 12 are thereby brought into frictional engagement with the drum 1, and in this state, the upper part of the tread surface 49 of the pedal 47 is depressed to pivot the pedal 47 on the pivot 46.
around the cone body 32 in the counterclockwise direction as shown in the figure, through the inner cable 38.
to the right as viewed in FIG. 2, causing the cones 32 to engage the elongated holes 30, 31 of the levers 26 and 27, thereby causing the brake shoes 9 and 10 to be moved so that the respective brake linings 11 and 12 are in contact with the drums. 1 and held in a state of frictional engagement.

Conversely, when releasing the operation of the drum brake used as a parking brake, use the operation knob 5 provided on the instrument panel 55.
Just pull 6. That is, by pulling the operation knob 56, the non-return engagement between the ratchet pawl 53 and the ratchet teeth 52 is released, and the spring force of the compression coil spring 43 causes the pedal 47 to move through the inner cable 38 as shown in FIG. Rotated clockwise, the cone 32 is driven to the left in FIG. 2, causing the brake shoes 9 and 10 to approach each other around the anchor pin 17 due to the spring force of the return springs 18 and 19. the respective brake linings 11 and 12
The frictional engagement with the drum 1 is released.

Although the present invention has been described above in detail with respect to specific embodiments, the present invention is not limited to such embodiments, and it is understood that various embodiments are possible within the scope of the present invention. It will be clear to those skilled in the art.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing one embodiment of a drum brake according to the present invention configured as a leading trailing (LT) brake, and FIG.
FIG. 3 is an enlarged partial cross-sectional view taken along line - in the figure, and FIG. 3 is a side view showing a brake pedal provided in the vehicle interior. 1...Drum, 2...Axle, 3...Axle line, 4...
... Hole, 5 ... Bucking plate, 6 ... Wheel cylinder, 7, 8 ... Piston rod, 9, 1
0... Brake shoe, 11, 12... Brake lining, 13, 14... One end, 15, 16...
...Other end, 17... Anchor pin, 18, 19...
Return spring, 20... Link, 21...
Brake pedal, 22, 23...one end, 24, 2
5... Pivot, 26, 27... Lever, 28, 29
...Other end, 30, 31...Elongated hole, 31a...
Axis line, 32... Cone, 33... Large diameter end, 34
...Small diameter end, 35...cap, 36...hole,
37...Means for controlling the axial position of the cone;
38...Inner cable, 39...One end, 40
...Ball, 41a...Hole, 41, 42...Spring seat,
43...Compression coil spring, 44...Pivot, 45...
... Pedal lever, 46 ... Pivot, 47 ... Pedal, 48 ... Rubber cover, 49 ... Tread section, 5
0, 51...Other end, 52...Ratchet tooth, 53
...Ratchet claw, 54...Inner cable,
55...Instrument panel, 56...Operation knob.

Claims (1)

[Scope of utility model registration request] A drum integrally connected to an axle, a bucking plate fixed to a fixed member of the vehicle, a wheel cylinder fixed to the bucking plate and expanded and contracted by controlling fluid pressure, and a wheel cylinder provided in the drum. is connected to the wheel cylinder at one end and pivoted to the bucking plate at the other end, and is pivoted by the wheel cylinder from a first position to a second position abutting the drum, thereby providing a brake. a pair of brake shoes that act, a brake pedal that controls fluid pressure in the wheel cylinder, and one end of which is pivotally supported at an intermediate portion between the one end and the other end of each of the brake shoes. a pair of levers, each lever having an elongated hole extending along its axis and linearly increasing in width toward the other end; a cone that is reciprocally movable, and means for controlling the axial position of the cone with respect to the pair of levers, the cone being driven in the axial direction to engage the elongated hole. A drum brake configured to maintain the pair of brake shoes in the second position.