JPH0225060B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drum brake device that uses a two-trailing type during service braking and a dual-servo type during parking braking.

As a conventional drum brake device of this kind, there is the one shown in Fig.
issue). That is, 1 is a brake drum, 2 is a back plate, 3 is a front brake shoe, and 4 is a rear brake shoe.A wheel cylinder 5 is fixed to the back plate 2, and one end of the front brake shoe 3 is fixed to the back plate 2. 3a to face this wheel cylinder 5, one end 4a of the rear brake shoe 4 to face the piston 6 of the wheel cylinder 5, and the other ends 3b, 4 of these front and rear brake shoes 3, 4
A connecting member 7 is inserted between b. Then, the free end 9b of the lever 9, whose base 9a is pivoted to one brake shoe 4 via the pin 8, is connected to the cable 10 of the parking brake operating device, and the lever 9 and the other brake shoe 3 are connected to each other. A strut 11 is interposed between them. 12 and 13 are brake shoes 3 and 4
This is a return spring stretched between the two.

During service braking, when the hydraulic pressure generated in the master cylinder due to the force applied to the brake pedal acts on the wheel cylinder 5, the piston 6 pushes the upper end 4a of the rear brake shoe 4, and when moving forward, the hydraulic pressure generated in the master cylinder acts on the wheel cylinder 5. The shoe 4 is pressed against the brake drum 1 rotating in the direction , and the lower end 4b of the shoe 4 pushes the lower end 3b of the front brake shoe 3 via the connecting member 7. Since the upper end 3a of this shoe 3 faces the wheel cylinder 5 fixed to the back plate 2, when the lower end 3b is pushed outward, the upper end 3a collides with the wheel cylinder 5, and this Using the abutment point as a fulcrum, the front brake shoe 3 also supports the brake drum 1.
is pressed against the inner circumferential surface of the In this case, since the direction of rotation of the brake drum 1 (in the direction of the arrow) when the vehicle moves forward and the direction of the force transmitted to the brake shoes 3 and 4 are opposite, two-trailing occurs and the control during service braking is Power is not very high.

Furthermore, when the brake lever facing the driver's seat is operated in order to apply the parking brake, the lever 9 rotates clockwise in the figure with the pin 8 as a fulcrum via the cable 10. When the lever 9 rotates, the upper part of the front brake shoe 3 is pushed outward via the strut 11, and as a reaction, the upper part of the rear brake shoe 4 is also pushed outward, causing the respective brake drums to be pushed outward. It is pressed against the inner peripheral surface of 1. In this case, the braking action becomes very large because it acts as a dual servo type.

However, in such a drum brake device, instead of the connecting member 7, an auto adjuster is inserted between the ends 3b and 4b of the brake shoes 3 and 4, and the adjustment lever of this adjuster and the wheel Connect the cylinder 5 or a pin fixed near it with an adjusting cable,
When the parking brake is activated, the distance between the brake shoes 3, 4 and the inner peripheral surface of the brake drum 1 is adjusted by pushing apart the ends 3b, 4b of the brake shoes 3, 4 using an auto adjuster. , the following problems occur. That is, when the brake shoes 3 and 4 are expanded during parking braking and are pressed against the inner circumferential surface of the brake drum 1, and when a rotational force is applied to the brake drum 1 in this state, the ends 3a and 4 of the brake shoes 3 and 4 4
Either a moves in the vertical direction in the figure and comes into pressure contact with the wheel cylinder 5 or the piston 6,
and the other is the wheel cylinder 5 or the piston 6
move away from In this way, when the ends 3a, 4a move in the vertical direction in the figure, the amount of tension on the adjusting cable is not determined only by the distance between the brake shoes 3, 4 and the brake drum 1; The amount of movement of the ends 3a, 4a in the vertical direction also has an effect. From this, if an auto adjuster is installed between the ends 3a and 4a of the brake shoes 3 and 4, the amount of adjustment obtained by this will be There is a problem in that the amount of movement in the vertical direction in the figure also affects the accuracy and tends to be inaccurate.

The present invention was made by focusing on such conventional problems, and an anchor pin fixed to a back plate is interposed between one opposing end of the front brake shoe and the rear brake shoe. let me,
In addition, the piston of the wheel cylinder is opposed only to the rear brake shoe on the anchor pin side, and the lever that is pivotally connected to the anchor pin side of one brake shoe and interlocks with the parking brake lever, and the other brake shoe A strut is strung between the anchor pin side, and an adjuster star is strung between the other opposing ends of both brake shoes. It is an object of the present invention to solve the above-mentioned problem by letting the shoe guide the middle part and then passing the adjusting cable over it.

The present invention will be described below with reference to illustrated embodiments. FIG. 2 is a diagram showing an embodiment of the present invention.

First, to explain the configuration, 1 is a brake drum that rotates in the direction of the arrow when the vehicle moves forward, 2 is a back plate, 3 is a front brake shoe, and 4 is a rear brake shoe, which is anchored to the back plate 2. Fix pin 15, and both brake shoes 3,
Each of the mutually opposing ends 3a, 4a of 4 is
A piston 6 of a single-open wheel cylinder 5 is placed opposite the anchor pin 15 and fixed to the back plate 2 near the anchor pin 15 side of the rear brake shoe 4.
The other opposing ends 3b, 4b of both the front and rear brake shoes 3, 4 are in contact with each other via the extrusion rod 16.
An adjuster 17 is inserted between them. Ajiasuta 17
This method adjusts the distance between the brake shoes 3, 4 and the inner circumferential surface of the brake drum 2 by adjusting the distance between the end portions 3b, 4b of both brake shoes 3, 4. use something Reference numeral 18 denotes an adjustment lever rotatably attached to the front brake shoe 3, and a pawl of this lever engages with a ratchet wheel 17a of the adjuster 17. An adjustment cable 19 is stretched between the adjustment lever 18 and the anchor pin 15, and the midway portion of this adjustment cable 19 is guided to a cable guide 3c formed in the front brake shoe 3. be done. Reference numeral 19a denotes a fitting for the end of the adjusting wire 19. Also, adjust lever 1
A return spring 13 is placed between the brake shoe 8 and the rear brake shoe 4, thereby urging the adjustment lever 18 in the counterclockwise direction in the figure. The end portions 3b and 4b are biased toward each other.

Further, a lever 9 is pivotally supported on a pin 8 attached near an anchor pin 15 of the front brake shoe 3, and a cable 10 of a parking brake device is connected to its free end 9b. A strut 11 is interposed between the lever 9 and the rear brake shoe 4 at a position on the anchor pin 15 side. 11a is
This is a coil spring that elastically supports the strut 11 on the brake shoe 4. Reference numeral 20 denotes a hole formed in the back plate 2 to communicate the inside and outside of the brake drum 1, and the cable 10 passes through this hole 20. 21 is a shoe hold down spring that supports the brake shoes 3, 4 in a floating manner on the back plate 2;
4 and the anchor pin 15, return springs 12a and 12b are installed, respectively. 22, the ends 3a, 4a of the brake shoes 3, 4 are connected to the anchor pin 15.
This is a leaf spring that prevents the pin 15 from coming off in the axial direction.

Next, the action will be explained.

During service braking, when the hydraulic pressure generated in the master cylinder by the brake pedal depression force is transmitted to the wheel cylinder 5, the piston 6 pushes the upper end 4a of the rear brake shoe 4, and when moving forward, the hydraulic pressure generated in the master cylinder is transmitted to the wheel cylinder 5. Brake drum 1 rotating at
At the same time, the lower end 4b of the brake shoe 4 in the figure pushes the end 3b of the front brake shoe 3 via the adjuster 17. Then, the upper end 3a of this shoe 3
is opposed to the anchor pin 15 fixed to the back plate 2, so when the lower end 3b is pushed outward, the upper end 3a is pushed against the anchor pin 15.
The front brake shoe 3 is also pressed against the inner peripheral surface of the brake drum 1 using the anchor pin 15 as a fulcrum. Thus, in this case, when the vehicle moves forward, the direction of rotation of the brake drum 1 (in the direction of the arrow) and the direction of the force transmitted to the brake shoes 3 and 4 are opposite, resulting in two-trailing, and there is no servo effect. The braking force during braking is not very high, as shown by the solid line in Figure 3 (the broken line in the figure shows the braking force of the leading-trailing type brake). If used on the rear wheels of a vehicle that uses disc brakes without a servo effect, the braking performance of the front and rear wheels will be balanced, making it possible to maintain stability in braking distribution.

Furthermore, when the brake lever facing the driver's seat is operated in order to apply the parking brake, the lever 9 rotates clockwise about the pin 8 via the cable 10. When the lever 9 rotates, the upper part of the rear brake shoe 4 is pushed outward via the strut 11, and as a reaction, the front brake shoe 3 is pushed out via the pin 8 of the lever 9.
The upper portions of the brake drums are also pushed outward and are pressed against the inner peripheral surface of the brake drum 1, respectively. Therefore, the braking pressure during the parking brake becomes very large since it acts as a dual servo type, and therefore the parking state of the vehicle is reliably maintained.

By the way, when the brake drum 1 is rotating or about to rotate in the direction of the arrow (i.e., the forward direction of the vehicle) during parking braking, the brake shoes 3 and 4
Due to the frictional force, the brake shoe 4 moves clockwise in the figure, and the upper end 4a of the rear brake shoe 4 collides with the anchor pin 15, while the upper end 3a of the front brake shoe 3 separates from the anchor pin 15. . The distance between both 15 and 3a at this time increases in accordance with the amount of wear on the brake shoes 3 and 4.
When the amount of wear increases and the amount of movement of the brake shoes 3 and 4 increases, the cable guide 3c of the brake shoe 3 pulls the adjustment cable 19 to a large extent, causing the adjustment lever 1
8 is rotated against the bias of the return spring 13.
As a result, the claw of the adjuster lever 18 rotates the ratchet wheel 17a of the adjuster star 17, thereby extending the adjuster star 17, thereby spreading the ends 3b and 4b of the brake shoes 3 and 4, To maintain an appropriate distance between brake shoes 3, 4 and the inner circumferential surface of a brake drum 1 when the brake is not in operation. The amount of extension of the adjuster star 17 at this time is determined by the amount of wear on the brake shoes 3 and 4. Since it corresponds to the separation distance between the anchor pin 15 and the end of the brake shoe 3 and the amount of tension of the adjusting cable 19 determined by this distance, an appropriate adjusting action can always be obtained.

As described above, according to the present invention, an anchor pin fixed to a back plate is interposed between one opposing end of a front brake shoe and a rear brake shoe, and The rear brake shoe only faces the piston of the wheel cylinder, and between the lever that is pivotally connected to the anchor pin side of one brake shoe and interlocks with the parking brake lever, and the other brake shoe, Suspend the strut on the anchor pin side, then suspend the adjuster star between the other opposing ends of both brake shoes, and connect the midway part of the strut to either brake shoe between the adjuster lever of the adjuster star and the anchor pin. Because the adjuster cable was routed around the cable, when the adjuster was used to adjust the distance between the brake shoe and the brake drum, a brake shoe other than the one that guides the adjuster collided with the anchor pin, causing its movement. is regulated. For this reason, since the amount of movement of both brake shoes corresponds to the amount of wear on the brake shoes, the adjuster will extend by the amount commensurate with the amount of wear. Therefore, according to the present invention, there is an effect of optimizing the amount of adjustment by the adjuster, and since this drum brake device does not have a servo effect during service braking, it is possible to use a disc brake that does not have a servo effect for the front wheel brake. If used on the rear wheels of a vehicle, the braking force between the front and rear wheels will be well balanced and the braking performance will be stable.At the same time, when the parking brake is applied, it acts as a dual servo type, which increases the boosting effect and improves the braking performance. It also has the effect of

[Brief explanation of drawings]

Figure 1 is a front sectional view of a conventional example, Figure 2 is a front sectional view of an embodiment of the present invention, and Figure 3 is a graph showing the relationship between braking force during service braking and the coefficient of friction of the lining material. It is. 1... Brake drum, 2... Back plate, 3, 4... Brake shoe, 3a, 3b, 4
a, 4b... end, 3c... cable guide, 5
...Wheel cylinder, 6...Piston, 8...
Pin, 9...Lever, 10...Cable, 11...
...Strut, 15...Anchor pin, 17...
Asia star, 18...Asia strever, 19
...Adjustment cable.

Claims (1)

[Claims] 1 An anchor pin fixed to the back plate is interposed between one opposing end of the front brake shoe and the rear brake shoe, and the wheel cylinder is connected only to the rear brake shoe on the anchor pin side. With the pistons facing each other, a lever is pivoted to the anchor pin side of one brake shoe and interlocks with the parking brake lever, and a strut is hung on the anchor pin side between the lever and the other brake shoe. An adjuster is hung between the other opposing ends of the brake shoe, and an adjustment cable is placed between the adjuster lever and the anchor pin of the adjuster, with the middle part guided by one of the brake shoes. A drum brake device featuring: