JPH0141855B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic shoe gap adjustment device for a leading/trailing type drum brake (hereinafter referred to as an L/T type drum brake).

The L/T type drum brake consists of a pair of left and right bow-shaped brake shoes, an anchor placed between opposite ends on one side, a shoe expansion mechanism such as a hydraulic cylinder device placed between the opposite ends on the other side, and a shoe expansion mechanism such as a hydraulic cylinder device placed between the opposite ends of the other side. The brake shoe is equipped with a return spring that applies a contraction/closing return force to a pair of brake shoes, and the left and right brake shoes are expanded using an anchor as a fulcrum by the operation of a shoe expansion mechanism. A strut is installed to define the return position of the expansion side end of the brake shoe.

As the lining wear of the brake shoe progresses over time, the gap between the inner surface of the drum and the shoe lining during non-braking increases. For example, a shoe gap automatic adjustment device of the type that gradually expands and repositions the return position of the brake shoe as the lining wear progresses by gradually increasing the axial length of the strut was developed in Japanese Patent Publication Publication No. 49.
- Provided by Publication No. 46021.

This includes a parking lever that is pivotally supported at the expansion side end of one brake shoe, and a strut that can be axially extended between the other brake shoe.
An adjuster lever is provided which is rotated by the displacement between one of the brake shoes and the strut, which causes relative movement left and right by the parking lever when the parking brake is activated, and the adjuster lever is pivoted to the strut by increasing the amount of rotation of the adjuster lever. This system rotates a gear that has been rotated to intermittently extend its axial length. Specifically, the parking lever and adjuster lever are controlled by the same pin installed at the expanded end of one brake shoe. At the same time, an adjuster spring is provided between the one brake shoe and the adjuster lever to apply rotational force to the adjuster lever, and an adjuster spring is provided at the engagement portion of the strut with the parking lever. A pin that engages with the long hole of the adjuster lever is provided, and the adjuster lever is rotated against the adjuster spring by the movement of the strut that follows the expansion of the other brake shoe when the parking brake is activated. However, when the strut axial force is released when the parking brake is released, the adjuster lever is returned and rotated by the spring force of the adjuster spring, and rotates the gear attached to the strut by one tooth as necessary.

The present invention takes into consideration the operating principle of this type of automatic shoe gap adjustment device, and aims to stabilize and ensure the operation and adjustment amount, and to reduce costs by simplifying the structure. .

In other words, with the conventional type mentioned above, it is necessary to provide a pin in the strut (usually the socket of the strut) that engages with the long hole of the adjuster lever, but this type of machining is difficult. In addition, the rotation of the adjuster lever is based on the pin on one brake shoe and the pin on the strut. Since the amount of offset in the direction of the drum axis of the adjuster spring stretched between the adjuster lever and the adjuster lever is structurally large, the adjuster lever pawl that snaps into the peripheral teeth of the gear mounted on the strut is The impact force also has to be relatively large in proportion to the spring force of the adjuster spring that urges the return rotational force of the adjuster lever, and as a result, the gear is rotated back (in the opposite direction to the adjustment direction). Furthermore, the position of the pin on the strut that engages with the long hole of the adjuster lever, which is the rotation reference point of the adjuster lever, may be Due to the accumulation of tolerances, it is unavoidable that the strut will have some degree of play (rolling) around the axis, and therefore, when slight movement occurs, the lever of the adjuster lever, which is determined by the positional relationship between the two base points and the pawl, There is a problem in that there is a risk that the adjustment may become unstable due to a change in the ratio, and in particular, a variation in the M value with respect to the strut axis at the engagement contact point between the claw portion and the gear.

Therefore, in the present invention, the rotation of the adjuster lever based on the rotation of the parking lever is directly transmitted without going through the engagement relationship with the strut, thereby preventing the interval fluctuation between the rotation base points, and the adjuster lever, By improving the engagement relationship between the parking lever and strut, we have reduced the force of the adjuster lever pawl against the strut shaft gear, making adjustment more stable and preventing malfunctions.In addition, we have simplified the shape of the strut. This is intended to simplify manufacturing and reduce costs, and specifically includes a pair of left and right brake shoes that are expandably mounted on a bucking plate, and one opposing end of these brake shoes. An anchor disposed between the two ends, an expansion mechanism disposed between the other end, a return spring that applies a spring force to the brake shoes in the contraction/closing direction, and an expansion mechanism for one brake shoe. A parking lever is pivotally supported on the open end side by a pin, and the parking lever is installed between the parking lever and the other brake shoe, and its axial length defines the retracted/closed position of the pair of brake shoes. A strut whose axial length is extended by the rotation of the gear, and a strut which is pivoted to the one brake shoe by the pin so as to be parallel to the parking lever, and which extends in the generatrix direction of the strut to support the shaft-mounted gear. an adjuster lever having a first arm formed with a claw portion that snaps into engagement so that the strut can be rotated, and this adjuster lever rotates the shaft-mounted gear of the strut by swinging when the brake is released. In the L/T type drum brake, the adjuster lever has a bent stopper part that extends parallel to the parking lever and engages the inner side edge of the drum of the parking lever at its extending end. The second arm is provided so that the parking lever directly operates the adjuster lever, and the strut is provided between the stopper portion of the adjuster lever and the one brake shoe. An adjuster spring made of a tension spring that is approximately parallel to the axis of the lever is tensioned, and this adjuster spring applies the elastic force of the stopper part of the second arm to the side edge of the parking lever and the force of the claw part of the first arm. This is an automatic shoe clearance adjustment device for L/T type drum brakes, characterized in that the tilting force that hits the strut shaft gear is applied to the adjuster lever, and furthermore, the device is configured so that the tilting force that hits the strut shaft gear is applied to the adjuster lever. By providing a strut toe spring that biases the brake to the side, it is possible to expand the range of adjustable brake operation modes.

The present invention will be described in detail below based on embodiments shown in the drawings.

Embodiment 1 In FIGS. 1 to 3, 1 is a bucking plate, 2 and 3 are brake shoes mounted on the bucking plate 1 so as to be expandable, and these brake shoes 2 and 3 are One opposing end is engaged with the anchor 4, and the other opposing end is engaged with the hydraulic cylinder device 5. Reference numeral 6 denotes a tension spring that engages and holds one opposing end of the brake shoes 2 and 3 with the anchor 4, and 7 a return spring that applies a spring force to the pair of brake shoes 2 and 3 in the direction of contraction and closing. It is.

Reference numeral 8 denotes a strut which is arranged approximately parallel to the hydraulic cylinder device 5 on the expansion side of these brake shoes 2, 3, and the retracted/closed position of the brake shoes 2, 3 is determined by the length of its extendable axis. It is set up to do so. That is, the strut 8 is rotatably engaged with the adjuster bolt 8a, and is engaged with the inner side edge of the drum of the other brake shoe 3 so that its rotation around the axis is restricted. A socket 8c is fitted into the head of the adjuster bolt 8a so as to be rotatable around the axis, and is engaged with the inner side edge of the drum of the parking lever 9 with rotation around the axis being restricted. and a gear 8d which is pivoted on the adjuster bolt 8a and has teeth formed on its periphery for feeding rotation in one direction.The rotation of the gear 8d causes the adjuster bolt 8a to move from the adjuster nut 8b. It is provided so that it can be screwed out to extend its axial length.

9 is a parking lever, whose one end (upper end in the figure) is pivotally supported on one brake shoe 2 by a pin 10, and the other end (lower end in the figure) is connected to a parking cable (not shown) inserted from outside the drum. ) is connected to. Then, when the parking lever 9 is rotated clockwise in FIG. 1 about the pin 10 by pulling the parking cable, the strut 8 is pushed to the left side in the figure due to this rotation, and the other brake shoe 3 is At the same time, the one brake shoe 2 is pushed to the right side in the figure via the pin 10, and the pair of left and right brake shoes 2 and 3 are moved against the spring force of the return spring 7. It is expanded to the left and right and comes into contact with the inner peripheral surface of a drum (not shown) to generate a parking brake force.

Incidentally, during service braking, the left and right brake shoes 2 and 3 are expanded by the hydraulic cylinder device 5.

Reference numeral 11 designates an adjuster lever mounted on one of the brake shoes 2 parallel to the front side of the parking lever 9 so as to be able to rotate around the pin 10.
The first arm 11a extends along the generatrix direction of
and a second one extending along the parking lever 9.
The first arm 11a has a claw portion 11c that elastically engages with the peripheral teeth of the gear 8d of the strut 8. A stopper portion 11d is formed at the bent end portion and engages with the inner side edge of the drum of the parking lever 9.

Reference numeral 12 denotes an adjuster spring, which is tensioned between the tip of the second arm 11b of the adjuster lever 11 and the one brake shoe 2 so as to be substantially parallel to the axis of the strut 8. The force applies a rotational force to the adjuster lever 11 in the counterclockwise direction in FIG.
is engaged with the inner side edge of the drum of the parking lever 9, and the engagement relationship shown in the figure between the end of the adjuster spring 12 and the adjuster lever 11 causes the first arm of the adjuster lever 11 to engage with the inner side edge of the drum of the parking lever 9. 11
It is provided to apply a tilting force that causes the claw portion 11c at the tip a to snap into engagement with the gear 8d of the strut 8.

In this example, a bent portion 11e that extends around the back side of the parking lever 9 is formed at the tip of the second arm 11b of the adjuster lever 11, and a bent portion 9a that goes around the back side of the parking lever 9 is provided in correspondence with this. , these engagements prevent the adjuster lever 11 from being left unreturned when the parking brake is released.

Next, the operation of the automatic shoe gap adjustment device for the L/T type drum brake constructed as described above will be explained.

When the parking brake is applied, when the lower end of the parking lever 9 is rotated and the pair of left and right brake shoes 2 and 3 are expanded, the adjuster lever 11 engages with the pin 10 on the one brake shoe 2. The parking lever 9 is directly rotated against the spring force of the adjuster spring 12 using the contact point A and the contact point B between the inner side edge of the drum of the parking lever 9 and the stopper portion 11d as rotational reference points, and the pawl is rotated directly by the parking lever 9 against the spring force of the adjuster spring 12. The portion 11c swings upward in FIG. 1 (along the circumferential direction of the gear). At this time, since a strong axial force is acting on the strut 8, the gear 8d does not rotate due to the frictional force caused by the collision between the claw portion 11c of the adjuster lever 11 and the gear 8d.

When the parking brake is released, the pair of left and right brake shoes 2 and 3 are activated by the return spring 7.
The parking lever 9 is rotated back to the initial position via the strut 8 while retracting and closing, and the adjuster lever 11 is moved by the adjuster spring 1.
It rotates back following the parking lever 9 due to the spring force of 2. Therefore, the claw portion 11c swings back downward in FIG. 1 (along the circumferential direction of the gear).

The claw portion 11c of such an adjuster lever 11
When the brake shoe 11c swings, if the lining wear of the brake shoes 2 and 3 has progressed due to repeated braking operations, and the amount of left and right expansion and contraction has increased, the upward swing of the pawl portion 11c will occur. The strut 8 becomes larger correspondingly, passes over one of the peripheral teeth of the gear 8d of the strut 8, and engages the claw portion 11c of the next tooth, and when the parking brake is released, there is no axial force of the strut 8, so the claw portion 11c As the gear 8d swings downward, one tooth of rotation is applied to the gear 8d. As a result, the adjuster bolt 8a, which is attached to the gear 8d, is screwed out from the adjuster nut 8b by the amount of rotation described above, and the axis of the strut 8 is expanded at a corresponding pitch, so that the brake shoes 2 and 3 are expanded and repositioned in their return positions. That will happen.

Note that C in the figure indicates the claw portion 11 of the adjuster lever 11.
C shows the engagement contact point of the gear 8d of the strut 8, and D shows the contact point with the inner surface of the rim of the one brake shoe 2 that locks the return rotation of the parking lever 9.

The automatic shoe gap adjusting device of this example having the above-described configuration and operation has the following features: first, the adjuster lever 11
The rotation reference point of is the first in relation to the parking lever 9.
Since a constant positional relationship is always maintained within the plane shown in the figure, the lever ratio does not vary depending on the rotational reference point, and secondly, the strut 8 of the claw portion 11c of the adjuster lever 11 The reason is that the impact force on the gear 8d can be stabilized and reduced. That is, at the former point, the adjuster lever 11 is directly rotated by the parking lever 9, and the rotation radius of the adjuster lever 11 and the parking lever 9, which is determined by the contact points A and B, which are the rotation bases, is always Since it is constant, the lever ratio is made constant regardless of the axial movement of the strut 8,
Stable and reliable adjustment is possible, and regarding the latter point, the spring force biasing of the adjuster spring 12 at a position offset from the surface of the adjuster lever 11 A bent stopper portion 11d at the tip of the arm 11b
is engaged with the inner side edge of the drum of the parking lever 9 and is received approximately near the connecting portion of the adjuster spring 12 to the adjuster lever 11 (see FIG. 2), and is further engaged with the claw portion of the adjuster lever 11. 11c
The tilting force for impacting the gear 8d of the strut 8 is applied by the end bending engagement portion 12b of the adjuster spring 12, so that the adjuster lever 11 is moved as shown in the first drawing. Separately from the body portion 12a of the adjuster spring 12 that provides a relatively large rotational force for rotation, the bending engagement portion 12b facilitates setting the tilting force as desired, thereby shortening the axial length of the strut 8. This makes it possible to appropriately prevent the gear 8d from twisting in the direction.

In addition, in order to stably apply the tilting force to the adjuster lever 11 described above, the adjuster lever 1
In order to prevent the engagement contact point B between the inner side edge of the drum and the parking lever 9 that locks the parking lever 9 from fluctuating in the axial direction of the drum, at least one of these engagement surfaces has a curved arc shape or a curved shape in the same direction. It can be said that it is practically desirable to form it into a spherical shape.

Embodiment 2 As shown in FIGS. 4 and 5, this embodiment has a structure in which a strut tow spring 13 is further added to the structure of Embodiment 1, and common members are designated by common reference numerals. The explanation will be omitted.

As shown in the figure, the feature of this example is that a tension type strut toe spring 1 is provided between the adjuster nut 8b of the strut 8 and one of the brake shoes 2.
3 is tensioned, and the direction in which the spring force is applied to the strut 8 by the spring 13 is twisted with respect to the axis of the strut 8.

That is, the strut tow spring 13
are offset by l ₁ in a plane perpendicular to the drum axis (Fig. 4) and by l ₂ in a plane parallel to the drum axis (Fig. 5). As shown in FIG. 2, a force F in the direction of axial compression and a force H perpendicular to the axis of the strut 8 act on the strut 8, and a slight rotational force around the axis is also applied to the strut 8.

The effects of such a configuration are as follows.

First, by applying the force F in the axial compression direction to the strut 8, it is possible to reduce the impact force of the claw portion 11c of the adjuster lever 11 on the gear 8d as described above, and the shoe clearance is adjusted according to the operation mode of the brake. The purpose is to increase the operable range of automatic adjustment. That is, the above-mentioned adjustment device adjusts the claw portion 11c of the adjuster lever 11 when the parking brake is activated.
When swinging, the structure is such that the axial force of the strut 8 restricts the rotation of the gear 8d due to frictional resistance, and therefore the hydraulic cylinder device 5
As when the parking brake is activated while the so-called service brake is activated,
Strut 8 while parking lever 9 is rotating
When there is no transmission of force, there is a great possibility that the gear 8d will drag. Therefore, in this example, in addition to reducing the frictional resistance by the claw portion 11c of the adjuster lever 11, the axial force F is applied by the strut toe spring 13 to restrict the rotation of the gear 8d. There is.

In this example, a force H perpendicular to the axis of the strut 8 is applied by the offset of the strut tow spring 13, and a prying force is applied to the threaded portion of the adjuster bolt 8a and adjuster nut 8b, thereby tightening the gear. 8d is amplified, and the set spring force of the spring 13 can be reduced.

In addition, the strut tow spring 1 of this example
Another effect of the addition of the spring 13 is that the rotational force is applied to the strut 8 by the offset of the spring 13. In other words, by applying the same rotational force, the strut 8, which has some axial freedom with respect to the parking lever 9 and the other brake shoe 3, is biased in one direction around the axis and is stopped from rattling. , an adjuster lever 11 with a constant lever ratio.
By controlling rolling by deflecting the strut 8 around the axis, the M value determined by the positional relationship between the claw portion 11c and the gear 8d is stabilized, and the adjustment amount is always kept constant.

As described above, the automatic shoe gap adjustment device for L/T type drum brakes according to the present invention uses a single adjuster spring to adjust the rotational force of the adjuster lever and the force of the claw's impact on the gear, respectively. In addition to being able to optimize the strut separately, the amount of adjustment can be made constant, and the operation can be stabilized and ensured.Furthermore, the shape of the strut can be simplified, making it easier to manufacture and reducing costs. is extremely large.

[Brief explanation of drawings]

The drawings show embodiments of the present invention.
The figure is a front view of the L/T type drum brake of Example 1, FIG. 2 is a side sectional view of the same, and FIG. 3 is a bottom sectional view of the same. FIG. 4 is a partial front view of the L/T type drum brake of Example 2, and FIG. 5 is a partial bottom sectional view of the same. 1... Bucking plate, 2, 3... Brake shoe, 4... Anchor, 5... Hydraulic cylinder device, 6... Tension spring, 7... Return spring, 8... Strut, 8a... Adjuster Bolt, 8b...Adjustment nut, 8c...
Socket, 8d... Gear, 9... Parking lever, 9a... Bent part, 10... Pin, 11... Adjuster lever, 11a... First arm, 11b...
...Second arm, 11c...Claw part, 11d...Stopper part, 11e...Bending part, 12...Adjuster spring, 12a...Body part, 12b...Bending engagement part, 13...Strut Toshiyu Spring.

Claims (1)

[Scope of Claims] 1. A pair of left and right brake shoes mounted on a bucking plate so as to be expandable, and an anchor disposed between opposing ends of these brake shoes on one side;
and a return spring that applies a spring force in the retracting/closing direction to these brake shoes, and is pivoted by a pin on the expansion end side of one brake shoe. The parking lever is installed between the parking lever and the other brake shoe, and its axial length defines the contracted/closed position of the pair of brake shoes, and the axial length is extended by the rotation of the shaft-mounted gear. a strut, which is pivoted to the one brake shoe by the pin so as to be parallel to the parking lever, and extends in the generatrix direction of the strut so as to be able to rotate the shaft-mounted gear. and an adjuster lever having a first arm formed with a mating pawl, and this adjuster lever engages the shaft-mounted gear of the strut by swinging when the brake is released.
In the type drum brake, the adjuster lever extends parallel to the parking lever, and has a bent stopper portion formed at the extending end thereof to engage with the inner side edge of the drum of the parking lever. By providing a second arm, the adjuster lever is directly actuated by the parker lever, and the axis of the strut is located between the stopper portion of the adjuster lever and the one brake shoe. An adjuster spring consisting of a tension spring that is approximately parallel to the
This adjuster spring biases the adjuster lever with the force of the stopper part of the second arm hitting the side edge of the parking lever and the tilting force of the claw part of the first arm hitting the strut shaft gear. An automatic shoe gap adjustment device for L/T type drum brakes, characterized by being configured as follows. 2. A stopper portion of the second arm of the adjuster lever;
The engagement of the parking lever with the inner edge of the drum
The automatic shoe gap adjustment device for an L/T type drum brake according to claim 1, characterized in that one side is configured to be a point engagement with a spherical surface. 3. A pair of left and right brake shoes mounted on the bucking plate so as to be expandable, and an anchor disposed between opposing ends of the brake shoes on one side;
and a return spring that applies a spring force in the retracting/closing direction to these brake shoes, and is pivoted by a pin on the expansion end side of one brake shoe. The parking lever is installed between the parking lever and the other brake shoe, and its axial length defines the contracted/closed position of the pair of brake shoes, and the axial length is extended by the rotation of the shaft-mounted gear. a strut, which is pivoted to the one brake shoe by the pin so as to be parallel to the parking lever, and extends in the generatrix direction of the strut so as to be able to rotate the shaft-mounted gear. and an adjuster lever having a first arm formed with a mating pawl, and this adjuster lever engages the shaft-mounted gear of the strut by swinging when the brake is released.
In the type drum brake, the adjuster lever extends parallel to the parking lever, and has a bent stopper portion formed at the extending end thereof to engage with the inner side edge of the drum of the parking lever. By providing a second arm, the adjuster lever is directly actuated by the parking lever, and the axis of the strut is connected between the stopper portion of the adjuster lever and the one brake shoe. An adjuster spring consisting of approximately parallel tension springs is tensioned,
This adjuster spring biases the adjuster lever with the force of the stopper part of the second arm hitting the side edge of the parking lever and the tilting force of the claw part of the first arm hitting the strut shaft gear. A strut shoe spring is provided between the strut and the one brake shoe, and the strut shoe spring is stretched such that the biasing direction of the spring force is offset from the axis of the strut. Automatic shoe clearance adjustment device for L/T type drum brakes. 4 A stopper portion of the second arm of the adjuster lever,
The engagement of the parking lever with the inner edge of the drum
4. The automatic shoe gap adjustment device for an L/T type drum brake according to claim 3, characterized in that one side is configured as a point engagement with a spherical surface.