JP4694704B2 - Drum brake shoe expansion device and drum brake having the shoe expansion device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a drum brake shoe expansion device for expanding a pair of brake shoes and a drum brake having the shoe expansion device, and more specifically, a crank mechanism which is the shoe expansion device is movably mounted on a stationary member. The structure relates to a sliding structure on the stationary member of the brake lever that is mounted and constitutes the crank mechanism.
[0002]
[Prior art]
As a mechanical shoe expansion device provided with a crank mechanism for expanding a pair of brake shoes, for example, a device disclosed in Japanese Patent Application Laid-Open No. 6-337027 is known. A drum brake provided with this shoe expansion device will be outlined with reference to FIGS. Note that “left” and “right” used in the description are those in FIGS. 4 and 5.
[0003]
A pair of brake shoes 12 and 13 are movably mounted by shoe hold mechanisms 14 and 15 on a back plate 11 fixed to the stationary part 10 of the vehicle body. The brake shoes 12 and 13 have their lower adjacent ends in FIG. 4 supported by the standing portion 16a of the substantially L-shaped anchor block 16, and their upper adjacent ends can be transmitted with each other by the adjuster 17. These abutment states are maintained by a pair of upper and lower shoe return springs 18, 19 connected between the brake shoes 12, 13.
[0004]
The anchor block 16 in this example has a seat portion 16b attached to the stationary portion 10 of the vehicle body with mounting bolts 20 and 21 with the back plate 11 in between, and these constitute a stationary member. However, the anchor block 16 may be fixed directly to the back plate 11 in some cases.
[0005]
The crank mechanism 22 that expands and operates one opposite side of the lower side of the brake shoes 12 and 13 in FIG. 4 includes a strut 23, a brake lever 24, and a lever pin 25. The crank mechanism 22 is disposed adjacent to the inside of the standing portion 16a of the anchor block 16 with a slight gap between the brake shoes 12 and 13.
[0006]
The strut 23 is composed of a single plate body, and is provided with a bridging portion 23a in the middle portion in the longitudinal direction in FIG. 4, and is bent into a U-shape with a lower opening except for the left contact end portion. , 23b. The opposing pieces 23b and 23b form a wide gap 23c at the middle in the longitudinal direction, and a narrow gap 23d continuous with the wide gap 23c is formed at the right end. Yes. Further, the left end portion is closely joined by welding or the like, and a shoe engagement groove 23e that is operatively engaged with the left brake shoe 12 is formed therein. However, the close contact and integration of the opposing pieces 23b, 23b at the left end are aimed at the function of preventing the opening of the mouth and the contact engagement portion from becoming loose, but are not essential elements.
[0007]
The brake lever 24 is composed of two overlapping plates, and is accommodated in the gaps 23c and 23d of the strut 23. And the right half side of both plate bodies is closely integrated by projection welding or the like, and a shoe engagement groove 24a that is operatively engaged with the right brake shoe 13 is formed therein, and A projection (base) 24b on the upper side of the shoe web 13a that forms the shoe engagement groove 24a is pivotally supported by a lever pin 25 at the right end of the strut 23. Further, the free end 24c on the left half side of both plates is separated so that a cable end 27a main body fixed to an end of an inner cable 27 constituting a brake cable 26, which will be described later, can be inserted, and a gap 24d is formed. The semicircular arc-shaped grooves 24e and 24e that can be connected to both the ears 27b and 27b of the cable end 27a are formed on the anti-traction direction side of the brake cable 26, respectively.
[0008]
The struts 23 and the brake lever 24 constituting the crank mechanism 22 have their outer end surfaces (sliding contact surfaces) 23f and 24f on the brake cable 26 pulling direction side on the heads of the mounting bolts 20 and 21, respectively. It is slidably mounted. As shown in FIG. 5, the outer end surface 24f of the brake lever 24 is formed in an arcuate surface so as to translate while rotating on the head of the right mounting bolt 21 with the lever pin 25 as a fulcrum. The contact point 24g is located on the free end 24c side from the line α parallel to the brake shaft through this axis when viewed in the axial direction of the lever pin 25. In other words, the center of the circular arc surface including the contact point 24g exists on the line β passing through this point and parallel to the brake shaft, and is located on the free end 24c side from the line α.
[0009]
The brake cable 26, which is a remote force transmission member, includes an inner cable 27, an outer casing 28, and the like. One end of the drum brake side is arranged in a direction parallel to the brake shaft, and the outer casing 28 protects the inner cable 27 from the outside air through an intermediate portion arranged along the chassis not shown. The other end is fixed to the chassis, and the other end of the inner cable 27 that is slidably fitted into the chassis is fixed to an operation lever in the vehicle compartment.
[0010]
Thus, one end of the brake cable 26 is arranged as follows. One end of a guide pipe 29 is fixed to the seat portion 16b of the anchor block 16, and the other end extends vertically through the back plate 11 and the stationary portion 10 of the vehicle body (in a direction parallel to the brake shaft). . Then, one end portion of the outer casing 28 is fixed to the outer end portion of the guide pipe 29, and one end portion of the inner cable 27 extending through the guide pipe 29 has a substantially cross shape fixed to the end portion. Both ear portions 27b and 27b of the cable end 27a are connected to the semi-circular grooves 24e and 24e of the brake lever 24, respectively.
[0011]
Next, the brake operation in the above-described configuration will be described.
Now, when the free end 24c of the brake lever 24 is pulled through the inner cable 27, the brake lever 24 rotates counterclockwise in FIG. 5 with the lever pin 25 as a fulcrum, and the right brake shoe 13 is expanded. Frictionally engage the brake drum (not shown). At the same time, the reaction force acts on the strut 23 via the lever pin 25, thereby expanding the left brake shoe 12 and frictionally engaging the brake drum. Thus, the frictional force of the primary brake shoe 12 or 13 with respect to the rotation direction of the brake drum is transmitted to the secondary brake shoe 13 or 12 via the adjuster 17, and this is supported by the anchor block 16 and applied to the braking force. Acts as a duo-servo type drum brake.
[0012]
[Problems to be solved by the invention]
The above-mentioned crank mechanism during brake operation is such that either one of the brake shoes is supported by the anchor block to generate a braking force, and both outer end surfaces of the brake lever and strut are on the head of the mounting bolt. Are pressed against each other.
And when delivering a vehicle to a remote place, it is loaded and transported on a freight car, a ship, etc. with the brakes applied as described above. When the inertia of the vehicle increases, the brake cable tension further increases, and while the crank mechanism rotates integrally with both brake shoes and brake drums, both brake shoes are supported on the anchor block alternately. Rotate in both directions. As a result, as is apparent from the structure shown in FIG. 5, after the brake lever is once pulled slightly, it rotates in both directions so as to repeat the returning operation.
[0013]
The behavior of the brake lever 24 at this time and its problems will be described based on the operation diagram shown in FIG.
That is, as the inertia force of the vehicle increases, when the brake lever 24 rotates about the axis O of the lever pin 25 in the direction in which the brake lever 24 is pulled, the contact point 24g with the mounting bolt 21 also becomes the axis O of the lever pin 25. Therefore, a new contact point 24g of the brake lever 24 is once pushed up by a height H equivalent to a distance parallel to the brake shaft to be moved downward in the figure. As a result, the brake lever 24 is lifted against the frictional force with the brake shoe 13, or must be lifted by interlocking the brake shoe 13 against the frictional force with the brake drum (not shown). Absent. Therefore, the contact point 24g of the brake lever 24 rotates under the same position on the head of the mounting bolt 21 and repeats the sliding operation while this behavior is performed under the braked state. The pressing force applied on the head of the mounting bolt 21 from the contact point 24g of the brake lever 24 is extremely large. Due to the frequent repetition of this behavior, especially when the head of the mounting bolt 21 is promoted to wear by groove or wear, smooth sliding of the brake lever 24 during normal braking operation is hindered and brake performance is deteriorated. Was sometimes invited. Further, when the head of the mounting bolt 21 is rough, an abnormal noise (sliding noise or scratching noise) is generated, which may cause discomfort to the passenger.
[0014]
In the present invention, even when the crank mechanism is repeatedly operated non-artificially with the brake applied during transportation to a remote place, the head of the mounting bolt does not wear and the durability is high. Another object of the present invention is to provide a drum brake shoe expansion device and a drum brake having the shoe expansion device that can provide stable braking performance over a long period of time. It is another object of the present invention to provide a drum brake shoe expansion device that does not cause an uncomfortable feeling to an occupant by generating an abnormal noise and a drum brake having the shoe expansion device .
[0015]
[Means for Solving the Problems]
In order to achieve the above object, in the shoe expansion device for a drum brake according to the present invention, a mechanism for sliding on a stationary member of a brake lever constituting the shoe expansion device is improved.
That is, a shoe engaging groove is formed between the sliding contact portion that slides on the stationary member of the brake lever and the pivot support portion of the brake lever, and the slide contact portion is viewed in the axial direction of the brake lever. Thus, it is formed on an arc surface centering on the pivot axis of the pivot part on a line parallel to the brake shaft through the pivot axis.
Further, the above-described brake lever may be a combined body in which two plates are stacked and integrated, or may be formed from a single plate. Further, the strut is preferably formed from a single plate.
[0016]
According to the shoe extension device for a drum brake and the drum brake having the shoe extension device configured as described above, the brake lever does not move even if the crank mechanism is operated artificially under the braked state. The contact point to the member rotates while maintaining the positional relationship as it is, or it floats away from the stationary member and does not give excessive pressing force, so that especially local friction and settling on the stationary member is greatly increased. Can improve. As a result, the brake lever slides smoothly on the stationary member during normal braking operation, so that stable braking performance can be maintained over a long period of time, and there is no noise on the sliding surface. Can be suppressed.
Further, since the brake levers and struts of the plate body can be formed by pressing, the processing is simple and suitable for mass production, and the waste can be easily removed to reduce the weight.
Further, the immovable member on which the crank mechanism is mounted may be a mounting bolt or a back plate for fixing the anchor block, and can be applied to variously formed drum brakes as will be described later.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
A shoe brake expansion device for a drum brake according to the present invention will be described below. In the description, the configuration of the drum brake is the same as that of the conventional example, and the same parts and portions are denoted by the same reference numerals and the description thereof is omitted.
[0018]
The first embodiment of the present invention will be described with reference to FIG. 1 showing the crank mechanism 22 in the axial direction of the lever pin 25 and FIG. 2 showing the operation of the crank mechanism.
However, in this example, since only the shape of one part of the brake lever 24 is different from that of the above-described conventional example, the difference will be mainly described.
Thus, the brake lever 24 in this example is braked through the axial center of the lever pin 25 when the outer end surface (sliding contact surface) 24f placed on the head of the mounting bolt 21 is viewed in the axial direction of the lever pin 25. It is formed on an arcuate surface centered at any point between the mounting bolt 21 and the lever pin 25 on a line α parallel to the axis χ (axle).
However, this figure illustrates a case where the center of the arc-shaped outer end surface 24f and the axis of the lever pin 25 are concentric. Here, the vicinity of the lever pin 25 (the pivotal support) mentioned above refers to the lever pin 25 and the vicinity of the lever pin 25, and any point between the mounting bolt 21 (non-moving member) and the vicinity of the lever pin 25 (the pivotal support). and it is intended to include any point in the line α from the mounting bolt 21 to the shaft center O.
[0019]
As a result, even if the brake lever 24 is pulled unintentionally and rotates during transportation by rail or ship under the braked state described above, as shown in the operation diagram of FIG. Since the contact point 24g slidably contacting the head of the mounting bolt 21 rotates along an arcuate locus γ centered on the axis O of the lever pin 25, the positional relationship of the mounting bolt 21 with respect to the head is determined. The pressing force does not change. Therefore, even if the brake lever 24 repeatedly rotates in both directions, the local wear and settling on the head of the mounting bolt 21 can be greatly improved, and stable braking performance during normal braking operation can be extended over a long period of time. It can be maintained, and the generation of abnormal noise (sliding noise and scratching noise) can also be suppressed. If the center of the arc-shaped outer end surface 24f of the brake lever 24 is formed closer to the mounting bolt 21 than the axis O on the line α parallel to the brake shaft through the axis O, the brake When the lever 24 rotates about the axis O, it is clear that the new contact point 24g moves in the direction of lifting from the head of the mounting bolt 21, and the above-described effect is further improved.
[0020]
Moreover, although the brake lever 24 of Example 1 mentioned above illustrated the thing which consists of the coupling body which overlap | superposed and integrated two plate bodies, it is not limited to this.
For example, a modification of the brake lever shown in FIG. 3 is composed of a single plate, and the cable end is different accordingly. Accordingly, only the brake lever 24 and the cable end 27a shown in the first embodiment will be described by replacing the 20's place with the 30's place.
That is, since the brake lever 34 is composed of a single plate body, the cable end 37a fixed to the end portion of the inner cable 37 has a hollow rectangular frame, and the hollow portion serves as a free end portion 34c of the brake lever 34. It is the structure inserted and connected to the semicircular arc-shaped groove 34e. Then, although it is clear that if the shape of the arcuate outer end surface of the brake lever 34 that slides on the immovable member is formed in the same manner as in the first embodiment described above, an equivalent effect can be obtained. Description is omitted.
[0021]
Note that the brake lever 34 in the present modification and the brake lever 24 and the strut 23 in the first embodiment described above are all formed of a plate body, and can be integrally formed by pressing, so that the processing is simple and suitable for mass production. In addition, it is possible to easily reduce waste and reduce weight.
[0022]
The above-described crank mechanism 22 according to the present invention has been described as being mounted on the heads of the mounting bolts 20 and 21 of the anchor block 16 in the duo-servo type drum brake. However, the present invention is not limited to this. For example, when the anchor block 16 has a pin-like anchor pin shape, the crank mechanism 22 may be placed directly on the back plate 11. Further, in place of the adjuster 17 in the conventional example, the function of supporting the brake shoes 12 and 13 in the same manner as the anchor block 16 and the clearance between the brake shoes 12 and 13 and a brake drum (not shown) are adjusted. An anchor member having a function is arranged and fixed on the back plate 11, and the brake lever 24 and the strut 23 of the crank mechanism 22 are brought into abutment engagement with the brake shoes 13 and 12, respectively, so-called leading The present invention can also be applied to a trailing drum brake. In this case as well, the crank mechanism 22 may be placed on the back plate 11.
[0023]
【The invention's effect】
Since the present invention is configured as described above, the following effects can be obtained.
That is, the brake lever sees the sliding contact portion that slides on the mounting bolt, which is a stationary member, in the direction of the pivot axis, passes through this axis, is on a line parallel to the brake shaft, and is pivoted from the stationary member. It is formed on a circular arc surface centered on any point between the vicinity of the branch.
Therefore, even if the brake lever operation is repeated artificially under the brake applied state, the pressing force acting on the immovable member from the brake lever can be changed or reduced. The local wear and settling on the member can be greatly improved.
As a result, the crank mechanism during normal brake operation always slides smoothly on the stationary member, so that stable braking performance can be obtained over a long period of time.
In addition, since the roughening of the sliding portion can be eliminated, it is possible to suppress the generation of abnormal noise (sliding noise or scratching noise) that gives the passenger discomfort.
In addition, if the brake lever and strut are made from a plate body, they can be integrally formed by pressing, so that the processing is simple, suitable for mass production, and can be easily reduced to reduce weight. I can .
[Brief description of the drawings]
FIG. 1 is a cross-sectional view corresponding to FIG. 5 showing a crank mechanism portion according to a first embodiment of the present invention; FIG. 2 is an operation explanatory view of the crank mechanism portion in FIG. 1; A variation is shown,
FIG. 4A is a plan view of the cable end connected, FIG. 4B is a left side view of the cable end, and FIG. 4C is a cross-sectional view taken along the line C-C in FIG. 5 is a cross-sectional view taken along the line VV in FIG. 4. FIG. 6 is a cross-sectional view taken along the line VI-VI in FIG. 5. FIG.
DESCRIPTION OF SYMBOLS 10 Car body stationary part 11 Back plate 12, 13 Brake shoe 16 Anchor block 17 Adjuster 20, 21 Fixing bolt 22 Crank mechanism 23 Strut 23a Bridge part 23b Opposing piece 23c Wide gap 23d Narrow gap 23e Shoe engagement groove 23f Outer end surface (sliding contact surface)
23g Contact 24 Brake lever 24a Shoe engaging groove 24b Projection (base)
24c Free end 24d Gap 24e Semi-circular groove 24f Outer end surface (sliding contact surface)
24g Contact 25 Lever pin (Pivot)
26 Brake cable 27a Cable end 34 Brake lever 37a Cable end

Claims (5)

A crank mechanism that expands one opposing side of the pair of brake shoes, a strut that operatively engages one end portion with the one brake shoe;
The strut is housed in a gap formed from the middle portion to the other end portion, and has a pivot portion pivotally supported on the other end portion of the strut so that it can be pivoted on the other brake shoe. A plate-like brake lever that is operatively engaged and that connects a remote force transmission member to the free end;
When the remote force transmission member is pulled in a direction parallel to the brake shaft, the brake lever rotates about the pivotal support portion with the strut, and the both slide on the non-moving member in a direction away from each other to operate the brake. In the drum brake shoe expansion device
The brake lever is formed with a sliding contact portion that slides on the stationary member, and a shoe engagement groove that presses the brake shoe at a position between the sliding contact portion and the pivot support portion,
When the sliding contact portion is viewed in the direction of the pivot axis of the brake lever, it is on a line parallel to the brake shaft through the pivot axis and centered on the pivot axis of the pivot portion. A shoe brake expansion device for a drum brake, characterized in that it is formed. Oite to claim 1, wherein the brake lever, so as to form a gap free end by superimposing two plate bodies, characterized in that it consists of a conjugate with an integrated base portion, drum brake Shoe expansion device. Oite to claim 1, wherein the brake lever, characterized in that it consists of one plate member, the shoe expanding device of a drum brake. In any one of claims 1 to 3, the struts, the facing plates is bent formed from one plate member through the bridge, over the other end from the intermediate portion of the facing plates A shoe brake expansion of a drum brake, wherein a shoe engaging groove is formed integrally with the brake lever, wherein a gap for accommodating the brake lever is formed and one end of the opposing piece is joined to engage with the one brake shoe. apparatus. A crank mechanism that expands one opposing side of the pair of brake shoes, a strut that operatively engages one end portion with the one brake shoe;
The strut is housed in a gap formed from the middle portion to the other end portion, and has a pivot portion pivotally supported on the other end portion of the strut so that it can be pivoted on the other brake shoe. A plate-like brake lever that is operatively engaged and that connects a remote force transmission member to the free end;
When the remote force transmission member is pulled in a direction parallel to the brake shaft, the brake lever rotates about the pivotal support portion with the strut, and the both slide on the non-moving member in a direction away from each other to operate the brake. In a drum brake having a shoe expansion device,
The brake lever is formed with a sliding contact portion that slides on the stationary member, and a shoe engagement groove that presses the brake shoe at a position between the sliding contact portion and the pivot support portion,
When the sliding contact portion is viewed in the direction of the pivot axis of the brake lever, it is on a line parallel to the brake shaft through the pivot axis and centered on the pivot axis of the pivot portion. Characterized by the formation,
A drum brake having a shoe expansion device.

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