JPS6224117Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a dual-servo type drum brake, and more particularly to a dual-servo type drum brake that can prevent the occurrence of impact noise during braking.

One type of automobile drum brake is a dual servo type (hereinafter referred to as D/S type) drum brake, which can obtain a large braking force with a small pedal effort.
This D/S type drum brake connects one end of a pair of brake shoes, which are disposed opposite to the inner circumferential surface of a rotating brake drum, with a movable connecting member, and is supported by an anchor, and the other is pushed apart by an actuator so that it slides into contact with the inner circumferential surface of the brake drum to perform a braking action. In this D/S type brake drum, the output of one brake shoe directly becomes the input of the other brake shoe via the connecting member, so that a large amount of force can be generated with a relatively small operating force due to the so-called self-servo action. However, on the other hand, the braking performance is unstable and it is easy to make a striking noise when braking. One of the pistons is configured to function as an anchor, but at the beginning of braking, the two pistons simultaneously push and spread their respective shoes, and when this shoe comes into sliding contact with the inner surface of the rotating drum, the primary shoe is The output of the cylinder directly becomes the input to the secondary cylinder via the connecting member and pressurizes it, causing the piston on the secondary side to be pushed back and collide with the body of the wheel cylinder, producing a striking sound, which causes the driver to feel anxious and It may cause discomfort.

As a way to eliminate this impact sound, Jikosho 11
The one described in Publication No.-12713 is known. This applies to one end of a pair of brake shoes in a dual-servo type drum brake in which the gap between one end of the pair of brake shoes is opened not by a wheel cylinder but by a purely mechanical expansion mechanism. An unbalanced spring is installed between the and anchor pin. In this drum brake, when the expansion mechanism operates to widen the gap between the ends of the pair of brake shoes, the brake shoe on the side that is biased toward the anchor pin by the unbalanced spring initially Instead of moving, only the brake shoe on the opposite side moves and comes into sliding contact with the inner surface of the drum, and the output of that brake shoe is transmitted to the brake shoe on the side that is kept in contact with the anchor pin. Since the brake shoe will be further attached to the anchor pin,
The above-mentioned impact sound is no longer generated.

However, in this drum brake, one end of the unbalance spring is hooked to an anchor pin, and the other end is hooked to a through hole formed in the shoe web. It would be easy to adopt this configuration if the drum brake was a simple one with only a purely mechanical expansion mechanism, but as mentioned above, it would be easy to adopt this configuration if the drum brake is equipped with a wheel cylinder operated by hydraulic pressure. In a drum brake, it is difficult to arrange an unbalanced spring in this manner. In particular, drum brakes in recent years have many things built into them outside the wheel cylinder, such as a purely mechanical expansion mechanism for the parking brake and an adjustment mechanism to counteract the increase in brake clearance due to wear of the brake shoe lining. This makes it even more difficult to secure a space for the unbalanced spring.

Furthermore, when one end of the unbalanced spring is engaged with a through hole formed in the shewweb, parts of the unbalanced spring other than the hooked part of the shewweb are likely to come into contact with the shewweb, and when the drum brake is activated or vibrations occur. At times, the contact portion may move relative to the shew web, causing abnormal noise or wear and tear on the contact portion, which may cause breakage.

This problem can be solved by attaching a latching member to the shew web that hooks one end of the unbalanced spring at a position away from the shew web, but this creates another problem in that the structure becomes complicated and the cost increases. .

With this background in mind, the present invention was developed with the aim of obtaining a drum brake that can easily avoid contact between the unbalanced spring and the shew web, and that does not have a complicated structure. be.

In order to achieve the above object, the present invention has a wheel cylinder fixed to a bucking plate with both ends opened, and a pair of pistons fitted into the wheel cylinder from both sides so as to be fitable to a certain depth. Each of the pair of pistons has one end portion facing each other of an integral brake shoe movably held by the bucking plate,
The brake shoes are brought into contact with each other by a shoe return spring stretched between the brake shoes, and one end of the brake shoes is placed between one of the ends of the brake shoes and a latching member fixed to the bucking plate. In a dual servo type drum brake in which an unbalanced spring biasing toward the wheel cylinder side is installed, and the other ends of the brake shoes are connected to each other by a movable connecting member, the shoe return spring is arranged in a U-shape as a whole and parallel to the bucking plate, and is engaged with the brake shoe at a pair of mounting legs formed by bending both ends of the U-shape toward the brake shoe. At the same time, one end of the unbalanced spring is hooked to one of a pair of mounting legs of the U spring, and one end of the unbalanced spring is attached to one of the mounting legs along the longitudinal direction of the mounting leg. A movement prevention means is provided to prevent movement in the direction.

In a drum brake configured as described above, the biasing force of the unbalanced spring is applied to the U spring, and the biasing force applied to the brake shoe by one mounting leg of the U spring is It is larger than the biasing force applied to the brake shoe. Therefore, as in the case where one end of the unbalanced spring is directly hooked onto the web of the brake shoe, it is possible to prevent the occurrence of impact noise at the initial stage of braking.

Moreover, since the mounting leg of the U-spring is used as a latching member for latching one end of the unbalanced spring, there is no need to provide a dedicated latching member, and an increase in cost can be avoided.

In addition, the mounting leg is provided with a movement prevention means that prevents one end of the unbalance spring from moving in the longitudinal direction of the mounting leg, so the unbalance spring is stabilized at a certain distance from the show web. As a result, contact between the unbalance spring and the shew web is avoided, and the effect of eliminating the possibility of abnormal noise or breakage of the unbalance spring due to such contact can be obtained.

Hereinafter, one embodiment of the present invention will be described in detail based on the drawings.

In the dual-servo type drum brake 2 shown in FIG. 1, what is indicated by a chain double-dashed line is a brake drum that rotates together with the wheels of the vehicle. The brake drum 4 is a cylindrical member with a bottom, but is removed here and only its position is shown. Further, reference numeral 6 in the figure represents a bucking plate, which is fixed to a non-rotating member such as an axle tube while facing the opening of the brake drum 4.

A pair of half-moon shaped brake shoes 8L, 8R are slidably held on the bucking plate 6 under a constant pressing force by shoe hold down springs 10L, 10R. The brake shoes 8L and 8R have arc-shaped shoe webs 12L and 12R, respectively, and rims 14L and 14 fixed at right angles to the outer edges of the shoe webs.
R and a lining 16 fixed to the outer surface of the rim.
It consists of L and 16R.

The lower ends of both brake shoes (in FIG. 1) are connected in contact with each other by a connecting rod 20 including an adjusting wheel 18, and this connecting rod 20 is fixed to the bucking plate 6. It is held slidably in the axial direction by a cylindrical body 22 . On the other hand, two pistons 24L and 24R are fitted into a wheel cylinder 26 fixed between the upper ends of both brake shoes so that they can be fitted to a certain depth, and brake shoes 8L and 8R are brought into contact with these, respectively. It is being Further, near the lower ends of the shew webs 12L and 12R, a spring 28 is stretched to bias the shew webs toward each other, and near their upper ends, as the parking lever 29 rotates, the shew webs 12L and 12R A strut 30 is provided to extend the distance between the upper ends of 12R.

A U spring 32 as a shoe return spring is arranged parallel to the bucking plate 6 between the brake shoes 8L and 8R.
As shown in FIG. 2, each end of the U spring 32 is bent in a direction perpendicular to the plane containing the U spring to form a mounting leg 34. Recesses 36 (see FIG. 3) formed in the shew web are respectively engaged with cutouts 38L and 38R of the shew web. And in the middle part of the U spring there is a Sheuweb 12
It is held by a holding member 40 fixed to L.

When the rotational direction of the brake drum 4 is in the direction of arrow A when the vehicle is moving forward, there is a brake shoe 8L between the brake shoe (secondary shoe) 8L on the left side of FIG. 1 and the bucking plate 6.
A tension coil spring 42 as an unbalanced spring that urges the wheel cylinder 26 toward the wheel cylinder 26 side.
is installed. That is, the U spring 3
As shown in FIGS. 3 and 5, a locking groove 4 is formed on the outer circumferential surface of the left mounting leg 34L of 2 by coining process, approximately perpendicular to the longitudinal direction of the mounting leg 34L.
4 is formed, and one end of the spring 42 is latched in this latching groove 44, while a latching groove 4 shown in FIG.
A pin 50 (latching member) having a diameter of 8 is erected in parallel to the mounting leg portion 34L, and this
The other end of the spring 42 is hooked to. Therefore, the brake shoe 8L (secondary shoe) is biased toward the piston 24L more than the brake shoe 8R (primary shoe) by the elastic force of the spring 42.

Next, the action of the drum brake 2 of this embodiment will be described in the case where the brake drum 4 rotates clockwise (in the direction of arrow A) when the vehicle moves forward.

When brake oil is supplied into the wheel cylinder 26, the pistons 24L and 24R move to the brake shoe 8.
Apply outward pressing force to L and 8R, respectively. At this time, both pistons 24L and 24R are always receiving the same inward force due to the elastic force of the U spring 32, but only the piston 24L is receiving the elastic force of the tension coil spring 42. Both pistons 24L, 24
The pushing force acting on R is in an unbalanced state. Therefore, even if the piston 24R (primary side) is pushed out by the supply of brake oil, the piston 24L (secondary side) does not move, and the flange portion of the piston 24L remains in close contact with the end surface of the wheel cylinder 26. is maintained.

Brake shoe 8R by piston 24R
When the (primary shoe) is pushed out, the lining 16R is brought into sliding contact with the inner peripheral surface of the brake drum 4, generating a frictional force, and as a result, the brake shoe 8R is rotated in the direction of arrow A. Then, the output of the brake shoe 8R directly becomes the input to the brake shoe 8L via the connecting rod 20, so that the brake shoe 8L (secondary shoe) is also inside the brake drum 4 in the same way as the brake shoe 8R. It is brought into sliding contact with the circumferential surface and rotated in the direction of arrow A by frictional force. As a result, the piston 24L is
However, as mentioned above, since the piston 24L remains in close contact with the wheel cylinder 26 from the beginning, the impact sound of the piston 24L hitting the wheel cylinder 26 is generated as in the conventional case. There is no fear.

The above explanation has been made regarding the case where the brake is used as a service brake. However, when the brake is used as a parking brake, the parking lever 29 and the strut 30 are used to control the brake shoes 8L and 8.
The only difference is that R is expanded, and the other operations are the same as when used as a service brake.

In this embodiment, the hook portions at both ends of the tension coil spring 42 as an unbalanced spring are respectively connected to the locking groove 44 formed in the mounting leg portion 34L of the U spring 32 and the hook portion fixed to the backing plate 6. Pin 50 as a hanging member
Since the drum brake 2 is latched to the latching groove 48 formed in the latching groove 48, even if the drum brake 2 vibrates, it will not move from the mounting position, and the shew web 12
There is no risk of contact with surrounding members such as L and strut 30, producing abnormal noise, or damage due to wear.

Additionally, although an example in which a tension coil spring 42 is provided as an unbalanced spring has been shown, the present invention is not limited to this in any way, and other types such as a V spring 52 as shown in FIG. It is also possible to use the spring as an unbalanced spring.

In addition, it goes without saying that the present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art without departing from the spirit thereof.

[Brief explanation of the drawing]

FIG. 1 is a front view of an embodiment of the present invention,
2 is a cross-sectional view of FIG. 1, FIG. 3 is an enlarged rear view of the mounting leg 34L, FIG. 4 is an enlarged view of part B (head of pin 50) in FIG. 2, and FIG. 3 is a cross-sectional view of FIG. 3, and FIG. 6 is a front view of main parts showing another embodiment of the present invention. 2...Drum brake, 6...Bucking plate, 8L, 8R...Brake shoe, 20...
Connection rod (connection member), 24L, 24R...Piston, 26...Wheel cylinder, 32...U
Spring (Show return spring), 34
L, 34R...Mounting leg, 42...Tension coil spring (unbalanced spring), 44...
Latching groove, 50...Pin (latching member), 52...V
Spring (unbalanced spring).

Claims (1)

[Utility Model Registration Claims] (1) A dual-servo drum brake in which a wheel cylinder fixed to a backing plate has both ends open, a pair of pistons are fitted into the wheel cylinder from both sides so as to be able to insert to a certain depth, one end of an integrated brake shoe movably held by the backing plate facing each other is brought into contact with each of the pair of pistons by a shoe return spring stretched between the brake shoes, and an unbalanced spring is attached between one of the one ends and a hook member fixed to the backing plate for biasing the one end toward the wheel cylinder, and the other ends of the brake shoes are connected to each other by a movable connecting member, A duo-servo type drum brake in which the shoe return spring is U-shaped as a whole and arranged parallel to the backing plate, both ends of the U-shape being bent toward the brake shoe to form a pair of mounting legs that engage with the brake shoe, one end of the unbalanced spring is hooked to one of the pair of mounting legs of the U-spring, and one of the mounting legs is provided with a movement prevention means for preventing one end of the unbalanced spring from moving in the longitudinal direction of the mounting legs. (2) A duo-servo type drum brake as described in claim 1 of the utility model registration, in which the movement prevention means is a hook groove formed on the outer circumferential surface of the mounting leg of the U-spring at a substantially right angle to the longitudinal direction of the mounting leg, and in which one end of the unbalanced spring is hooked.