JPS5821944Y2 - Wedge device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a brake actuating device that uses a wedge to actuate a plunger via a roller.

In so-called wedge brakes, the input to the wedge is increased and transmitted to the plunger, which increases the input to the brake shoes and improves the braking force. There is a disadvantage that the stroke of the wedge increases significantly relative to the stroke.

On the other hand, the maximum stroke that a wedge can take is limited by, for example, the gap between the wedge tip and the wedge, the space inside the brake device, the amount of oil in the operating source such as a cylinder, and its maximum stroke, etc. I can't.

For this reason, the wedge angle is set appropriately while taking into account effectiveness, stroke, efficiency, etc., but as the gap between the drum and lining increases as the brake is used, the stroke of the plunger also increases. The stroke will be increased by cotα times (α is the wedge angle, usually 10 to 20 degrees, therefore 2.7 to 5.7 times).

In this case, the brake is usually equipped with an adjuster, which is used to adjust the gap between the drum and the brake shoe, but in the case of wedge brakes, the adjustment work is extremely expensive compared to other types of brakes. If not done frequently and properly, the tip of the wedge may become
・The stroke of the wedge reaches the above limit value in a short period of time, such as hitting the wedge! cormorant.

In this case, no matter how much the input to the wedge is increased, the braking force cannot be increased.

This phenomenon occurs suddenly and unexpectedly when the driver is using the vehicle, especially in vehicles with air brakes where the pedal stroke is not proportional to the gap between the drum and the brake shoes, so it is difficult to stop the vehicle safely. It is extremely dangerous.

On the other hand, if the wedge angle is set as large as possible within a certain range, the increase in wedge stroke can be suppressed to a smaller extent as the gap between the drum and brake shoes increases, but at the same time, the effectiveness of the brake can also be reduced. Hope to become 1
It's not right.

To solve this problem, methods have been proposed in the past, such as electrically detecting the stroke of the wedge or brake shoe, or visually inspecting the wedge movement from the outside, but these methods are complicated in structure and expensive. Therefore, the current situation is that it has not been put into practical use.

In order to solve this problem, the present invention increases the wedge angle of the wedge corresponding to the gap when the gap between the drum and the lining exceeds a predetermined value that can be safely allowed. By making the ratio of the stroke thicker than during the normal stroke and allowing some leeway in the stroke, it is possible to prevent the above-mentioned drastic reduction in braking force, stop the vehicle safely, and increase the braking force to an extent greater than the normal stroke. This makes the driver aware of the necessity of adjusting the gap between the drum and the brake shoes.

To explain one embodiment of the present invention with reference to the drawings, reference numeral 1 denotes a back plate to which a housing 3 is fixed with bolts 2, and brake shoes 5 are biased with springs 6 and slidable on the heads 4 and 4'. It is movably abutted.

The brake shoe 5 has two webs 5a, and the narrow side surface 4ak of the head 4 is held between the webs 5a, thereby stably holding the head 4 against movement in the axle direction.

Reference numeral 18 denotes an adjuster, which includes a bolt 20 that abuts against a pin 19 fixed to a hole in the two webs 5a, a nut 21 that screws into the bolt 20, and a sleeve 22 that accommodates the nut 21.
, the bottom surface of the sleeve 22 abuts the head 4',
When the lining becomes worn, the bolt 20 is screwed out by rotating the nut 21, thereby correcting the brake outer diameter.

The housing 3 has a hole 3a, and a plunger 7 is slidably fitted into the hole 3a, with one end of the plunger 7 having a small diameter 7.
a and insert it into the hole 4a of the head 4.

A groove 4b is provided near the head 4 of the plunger 7, and a seal 8 is fitted into the groove 4b to prevent foreign matter from entering the sliding surface between the housing 3 and the plunger 7 from the outside.

A groove 7b is provided at the other end of the plunger 7, a roller 9 is accommodated in the groove Ib, and a pin 10 is inserted into the hole 7c of the plunger 7.
Support it by inserting it into the

2. Place the wedge 11 in contact with the outer peripheral surface 9a of the roller 9.
The wedge 11 is inserted between two rollers 9, and the inclined surfaces 11a from the tip to the vicinity of the distal end on both sides of the wedge 11 are made the normal wedge angle a, and the wedge angle of the inclined surface 11b near the distal end of the wedge 11 is made the normal wedge angle a. Make it larger than the wedge angle a.

b is 45° > b > a, which is usually enough to ensure effectiveness as an emergency brake, that is, b:2
It is desirable to set it to a.

The side surface of the wedge 11 is directly guided by the extension of the groove 7b of the plunger 7 with a small gap.

The wedge 11 has a shaft portion 12, and a spring 14 is attached to this shaft portion 12 with a retaining ring 13.
The wedge 11 is pulled in so that the bottom 11c of the housing 3 collides with the washer 15 inserted into the hole 3b of the housing 3.

Further, the housing 3 is provided with an internal thread 3c, and after the washer 15 is fitted, the threaded portion 16a of the pneumatic or hydraulic actuator 16 is fully screwed in and fixed.

Now, when the actuator 16 is actuated, the shaft portion 12 of the wedge 11 is pushed up against the spring 14, and as a result, the inclined surface 11a of the wedge 11 is pushed forward between the rollers 9, and the force is applied via the rollers 9 and the pin 10. is transformed in the orthogonal direction,
The plunger 7 moves outward and spreads out the brake shoes 5 via the head 4, and the brake shoes 5 are pressed against the drum 17 to generate braking force.

In this case, if the gap between the drum 17 and the brake shoe 5 is within a predetermined value that can be safely allowed, the wedge 1
1 has a length A determined so that it engages with the roller 9 within the range of the inclined surface 11a having an appropriate wedge angle a, and the maximum stroke of the plunger 7 in this range is Ata.
It is rla.

Next, when the gap between the drum 17 and the brake shoe 5 becomes larger than the predetermined value due to wear of the lining, the roller 9 moves to the inclined surface 1 near the end with a wedge angle b (b>a).
1b, and further pushes up the plunger 7 by Btanb as the maximum value.

On the other hand, in a conventional wedge, the wedge angle is constant, so if this angle is a, the maximum stroke of the plunger at this time is (A+B) tan a.

Therefore, the difference in plunger stroke of 70 between the wedge of the present invention and the conventional wedge is (A tan a + B tan b ) - (A + B
) tan aB (tan b - tan a)>
0, and the stroke of the plunger 7 increases by this amount.

That is, in the present invention, if the gap between the drum 17 and the brake shoe 5 is within a safely allowable value, proper effectiveness can be obtained on the inclined surface 11a with a moderate wedge angle a, and the drum 17 If the gap between the drum 17 and the brake shoe 5 exceeds a preset allowable value, the inclined surface 11b having a large wedge angle will reduce the gap between the drum 17 and the brake shoe 5.
Since the stroke of the wedge 11 can be made smaller, it is possible to increase the above-mentioned allowable value at the point where the upper surface 11d of the wedge 11 butts against the abutment surface 3d of the housing 3, compared to, for example, the case where only the wedge angle a is used. It is possible and safe.

Furthermore, when the roller 9 is pressed by the inclined surface 11b near the end of the wedge 11, the braking force is 1 compared to when the roller 9 is pushed by the inclined surface 11a.
b becomes smaller.

Therefore, the braking force is reduced to some extent, and the driver needs to increase the pedal force in order to obtain the same deceleration, and can easily sense the need for brake maintenance.

Furthermore, the present invention can be easily applied to a pull-type wedge actuating device and similar effects can be obtained.

As described above, the present invention can ensure the required braking effect when the gap between the drum 17 and the brake shoe 5 is within the permissible value, and when the gap between the brake shoe 5 and the drum 17 exceeds the permissible value. In such a case, the stroke of the plunger 70 is made larger by the inclined surface 11b near the end of the wedge 11 to provide an allowance for the gap, thereby preventing a sudden drop in braking force, and reducing the braking force to a certain extent compared to normal times, thereby making it easier for the driver to This has a great effect in stopping the vehicle safely, such as by sensing the need to adjust the gap between the brake shoe 5 and the drum 17.

[Brief explanation of the drawing]

Fig. 1 is a front view of a brake showing an embodiment of the present invention;
The figure is a cross-sectional view of the main parts of the device of the present invention, and Figure 3 is
4 is a sectional view taken along the X-line, and FIG. 4 is a sectional view taken along the Y--Y line in FIG. 1. 1... Back plate, 3... Housing, 4... Head, 5... Brake shoe, 7... Plunger, 9... ...Roller, 10...Pin, 11...Wedge, 11a, 11b...Slope of wedge,
14... Spring, 15... Washer, 16... Actuator, 17... Drum.

Claims (1)

[Scope of utility model registration request] A pin 1 is attached to each of the opposing parts of the two opposing plungers 7.
In a brake actuating device in which a roller 9 is rotatably attached through a roller 9 and a wedge 11 is movably provided between the two rollers 9, the inclined surface 11a from the tip of the wedge 11 to the tip near the end is normal. Let the wedge angle a be,
The rotation surface of the roller 9 is used when the gap between the brake shoe 5 and the drum 17 is within a predetermined value that can be safely allowed, and the wedge angle of the inclined surface 11b near the end of the wedge 11 is used as the normal wedge angle a. A wedging device characterized in that the gap is made larger than the above, and serves as a transfer surface of the roller 9 when the gap exceeds the predetermined value.