JPS6121622Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention is characterized in that first and second members defining a hydraulic chamber of a wheel cylinder are disposed so as to be relatively non-rotatable and relatively slidable, and the hydraulic pressure supplied to the hydraulic chamber is In hydraulically operated drum brakes in which the brake shoe is actuated by the separation action of both members, the wear of the brake shoe lining is automatically compensated to maintain a constant brake shoe operating gap. The present invention relates to an automatic adjustment device that enables reliable braking by a predetermined amount of operation of a brake pedal.

As such an automatic adjustment device, the present applicant has proposed an adjustment nut that is non-rotatably supported by one of the first and second members and that abuts a contact surface provided on the one member in a separable manner; a spring that biases the adjustment nut toward the contact side with the abutment surface; an adjustment rod that is screwed into the adjustment nut via a quick screw; and an adjustment rod that is rotatably fitted into the clutch hole; The clutch body is comprised of a clutch body that cooperates with a clutch surface formed on the back wall, and a seal member that is fitted into the other member to isolate the clutch surface and the hydraulic chamber. There is already a mechanism that frictionally connects with the clutch surface when receiving a thrust toward the clutch surface due to oil pressure above a certain value and when receiving a thrust toward the clutch surface due to the return spring of the brake shoe. is suggesting. This automatic adjustment device prevents over-adjustment due to elastic deformation of each part of the brake during strong braking when the oil pressure in the hydraulic chamber increases above a predetermined value, thereby preventing the brake shoe from dragging due to over-adjustment. It also has the advantage that the device can be compactly accommodated in the hydraulic chamber and the movable parts of the device can be lubricated by the hydraulic oil in the hydraulic chamber. However, in a drum brake equipped with such an automatic adjustment device, a stepped portion is formed on the inner circumferential surface of the brake drum due to sliding friction with the brake shoe over a long period of time.
Since the brake shoe is expanded and adjusted by an automatic adjustment device to compensate for wear on its lining, for example, when the brake drum is removed axially to replace the brake shoe, the damage caused by The stepped portion and the brake shoe may interfere with each other and obstruct the release of the brake drum, which poses a problem that makes the removal work difficult.

Therefore, the present invention provides an automatic adjustment release chamber adjacent to the clutch hole, which faces the outer end surface of the clutch body, and allows a pressing operation to disengage the clutch body from the clutch surface in this automatic adjustment release chamber, This pressing operation cancels the automatic adjustment action and contracts the brake shoe, making it easy to remove the brake drum in the axial direction without being disturbed even if a step is formed on the inner circumferential surface of the brake. It is an object of the present invention to provide the above-mentioned automatic adjustment device.

Embodiments of the present invention will be described below with reference to the drawings.

First, FIG. 1 shows a first embodiment in which the present invention is applied to a two-leading shoe type drum brake for an automobile.A pair of upper and lower wheel cylinders 2,
2' and a pair of left and right brake shoes 3, 3' are arranged point-symmetrically around the center of the back plate 1, and drum brakes that surround the brake shoes 3, 3' and rotate together with the wheels are not shown. do not have.

Each of the wheel cylinders 2, 2' comprises a cylinder body 4 having a cylinder bore 4a which is open at only one end, and a hydraulic chamber 5 which slides into the cylinder bore 4a.
The cylinder body 4 is attached to the back plate 1 by a bolt 7.
The cylinder body 4 and the piston 6 are respectively formed at their outer ends with engagement grooves 9, 9', into which the brake shoes 3,
The corresponding ends of the brake shoes 3, 3' are engaged with each other, and return springs 10, 10' are stretched between the two brake shoes 3, 3' to maintain the engagement and urge the two brake shoes 3, 3' in the contracting direction. The engagement of the grooves 9, 9' with the brake shoes 3, 3' prevents the cylinder body 4 and the piston 6 from rotating relative to each other.

The upper wheel cylinder 2 has its hydraulic chamber 5.
A hydraulic pressure introduction port 11 for introducing the output hydraulic pressure of a brake master cylinder (not shown) is provided between the two wheel cylinders 2 and 2', and the hydraulic pressure introduced into the upper wheel cylinder 2 is transferred to the lower wheel cylinder 2'. Communication pipe 1 for supplying
2 are connected.

The automatic adjustment device A of the present invention is installed in the hydraulic chambers 5 of both wheel cylinders 2 and 2', and since they have the same structure, only the automatic adjustment device A in the upper wheel cylinder 2 will be described in detail below. Explain.

The inner end surface of the piston 6 has a large diameter hole 13 and a small diameter hole 1.
A stepped hole consisting of 4 is provided, and the stepped portion of the stepped hole is formed in a conical abutment surface 15. An adjustment nut 16 that abuts the contact surface 15 in a separable manner is slid into the large diameter hole 13, and the base end of a spring 17 that urges the adjustment nut 16 toward the contact surface 15 is fixed to the piston 6. The spring 17 has a function of pressing and holding the adjusting nut 16 against the contact surface 15, and also has a function of preventing rotation of the adjusting nut 16 due to frictional engagement or uneven engagement between the spring 17 and the adjusting nut 16.

An adjustment rod 18 is screwed into the center of the adjustment nut 16 through a quick screw 19 so as to pass through the adjustment nut 16, and one end thereof is received in the small diameter hole 14.
The threaded portion between the adjusting nut 16 and the adjusting rod 18 is provided with an appropriate operating gap for each brake shoe 3, 3', that is, an appropriate gap between each brake shoe 3, 3' and a brake drum (not shown). There is a play in the axial direction, and the large diameter hole 13 and the small diameter hole 14 are always in communication through this play. Therefore, the hydraulic pressure introduced into the hydraulic chamber 5 acts even on the adjustment rod 18 within the small diameter hole 14.

A clutch body 20 is integrally formed at the other end of the adjustment rod 18, and this clutch body 20 is rotatably slidably fitted into a clutch hole 21 provided in the inner end wall of the cylinder hole 4a. It faces a conical clutch surface 22 formed on the back wall of the clutch. A sealing member 23 is fitted into the clutch hole 21 to prevent the hydraulic pressure in the hydraulic chamber 5 from acting on the clutch surface 22 .

As shown in FIG. 2, the cylinder body 4 is provided with an automatic adjustment release chamber 24 adjacent to the clutch hole 21 that faces the outer end surface of the clutch body 20, and a press ball 25 is housed in the chamber 21. Ru. Further, a press bolt 26 extending perpendicularly to the adjustment rod 18 is screwed into the cylinder body 4 . The conical tip 26a of this bolt 26 is connected to the automatic adjustment release chamber 24.
, and faces the outer end surface of the clutch body 20 via the press ball 25, normally leaving the press ball 25 free. A lock nut 27 is screwed onto the bolt 26 to fix the screwed position thereof. A working window 28 is provided in the back plate 1 opposite the outer end of the bolt 26, and a blind cover 29 is usually fitted into this window 28.

Next, to explain the operation of this embodiment, in order to perform braking, if a brake master cylinder (not shown) is operated and its output oil pressure is supplied to the oil pressure chamber 5 of the upper wheel cylinder 2, the oil pressure is transferred to the communication pipe 1.
2 to the lower wheel cylinders 2', these oil pressures cause the pistons 6 of each wheel cylinder 2, 2' to move outward and expand the corresponding brake shoes 3, 3'. By pressing against the inner peripheral surface of a brake drum (not shown), it is possible to apply braking force to the brake drum and therefore to the wheels.

During this braking, the hydraulic pressure in the hydraulic chamber 5 is controlled by the adjusting nut 1.
6, it does not exert any thrust because it acts equally on both end faces of the clutch body 20.
, exerts a thrust toward the clutch surface 22 of a value equal to the cross-sectional area of the clutch body 20 multiplied by the above-mentioned oil pressure, and this thrust determines the frictional coupling force between the clutch body 20 and the clutch surface.

By the way, under normal braking conditions, the oil pressure in the hydraulic chamber 5 is relatively low, and therefore the frictional coupling force between the clutch body 20 and the clutch surface 22 is relatively small. When the piston 6 moves further outward, the adjusting nut 16 is moved to the contact surface 1 by the elastic force of the spring 17.
The clutch body 20 is moved together with the piston 6 while maintaining the state of contact with the clutch body 5, and the clutch body 20 is separated from the clutch surface 22 against the thrust through the adjusting rod 18. When the clutch body 20 separates from the clutch surface 22, the thrust causes the clutch body 20 to spirally move toward the clutch surface 22 with respect to the non-rotatable adjusting nut 16 and re-engage the clutch surface 22. During this time, the pressing ball 25 is playing between the clutch body 20 and the pressing bolt 26, and does not in any way prevent the clutch body 20 from engaging the clutch surface 22. Further, since the air in the automatic adjustment release chamber 24 expands and contracts as the clutch body 20 moves forward and backward, it does not interfere with the engagement and disengagement of the clutch body 20 with respect to the clutch surface 22 in any way. In this way, the brake shoes 3, 3'
A self-adjusting action takes place to compensate for wear of the lining.

Here, if the pressure inside the hydraulic chamber 5 is reduced in order to release the brake, the brake shoes 3, 3' will be released by the return springs 10,
The return force of the return springs 10, 10' is applied to the clutch body 20 through the piston 6, adjustment nut 16, and adjustment rod 18.
acts as a thrust toward the clutch surface 22,
As a result, the clutch body 20 is frictionally coupled to the clutch surface 22 and cannot be rotated. Therefore, relative rotation between the adjusting nut 16 and the adjusting rod 18 is also disabled, so the piston 6 and the adjusting nut 16 can only move backward by the amount of play in the threaded portion of the adjusting nut 16 and adjusting rod 18. As a result,
An appropriate gap corresponding to the above play is created between the lining of each brake shoe 3, 3' and the inner peripheral surface of the brake drum.

In addition, when strong braking is performed, the above-mentioned process will take place before the hydraulic pressure in the hydraulic chamber 5 rises to a predetermined value that causes elastic deformation in the brake shoes 3, 3', brake drum, etc. When the automatic adjustment action is performed and the oil pressure exceeds the predetermined value, the thrust due to the oil pressure of the clutch body 20 increases to maintain the clutch body 20 in a frictionally connected state with the clutch surface 22, so that the clutch body 20 and Adjustment rod 18
becomes unable to rotate. Therefore, since the adjusting nut 16, which is originally non-rotatable, is fastened on the adjusting rod 18, when the piston 6 moves further outward due to elastic deformation of the brake drum, etc., the abutment surface 15 of the piston 6 is moved away from the adjusting nut 16. I will be leaving. In this way, the automatic adjustment effect is stopped.

Next, when removing the brake driver to replace the brake shoes 3, 3' with new parts, etc.,
The blind cover 29 is removed from the working window 28 of the back plate 1, the lock nut 27 is loosened using a tool inserted through the working window 28, and the pressing bolt 26 is screwed into the automatic adjustment release chamber 24. Then, press bolt 2
The conical tip 26a of No. 6 presses the pressing ball 25 against the center of the outer end surface of the clutch body 20, thereby disengaging the clutch body 20 from the clutch surface 22. When the clutch body 20 is disengaged from the clutch surface 22, the adjusting rod 18 becomes rotatable and the adjusting nut 16
Therefore, the piston 6 and the adjusting nut 16 move backward while rotating the adjusting rod 18 due to the returning force of the return springs 10, 10' of the brake shoes 3, 3'. The brake shoes 3, 3' are thus retracted and a sufficient gap is ensured between them and the brake drum to facilitate the axial removal of the brake drum.

The present invention can also be applied to a drum brake in which a wheel cylinder is provided with a pair of pistons that operate in opposite directions, and in this case, one piston has a clutch hole 21 for the clutch body 20. is provided, and the other piston is provided with an abutment surface 15 for an adjusting nut 16.

FIG. 3 shows another embodiment of the present invention, in which the outer end surface of the clutch body 20 is formed into a conical shape, the top part 20a of which faces the automatic adjustment release chamber 24, and a back plate is provided in the automatic adjustment release chamber 24. A tool hole 30 is opened in line with the working window 28 of No. 1, and the tool hole 30 is normally closed with a plug 31. Therefore, when disengaging the clutch body 20 from the clutch surface 22, remove the blind cover 29 and the plug 31,
A suitable rod-shaped tool 3 such as a screwdriver is inserted into the automatic adjustment release chamber 24 through the work window 28 and the tool hole 30.
2 in the direction of the arrow to press the top 20a of the clutch body 20.

As described above, according to the present invention, an automatic adjustment release chamber facing the outer end surface of the clutch body is provided adjacent to the clutch hole, and a pressing operation for disengaging the clutch body from the clutch surface can be performed in this automatic adjustment release chamber. Therefore, the brake shoe can be contracted by disengaging the clutch body from the clutch surface, and even if a step is formed on the inner peripheral surface of the brake drum due to wear, the step will not interfere with the brake shoe. The brake drum can be removed in the axial direction without causing any damage, which is extremely useful in facilitating maintenance work such as replacing the brake shoe.

[Brief explanation of the drawing]

Fig. 1 is an overall longitudinal sectional front view of the main parts of a drum brake showing a first embodiment of the present invention, Fig. 2 is an enlarged sectional view taken along the - line in Fig. 1, and Fig. 3 shows a second embodiment of the present invention. , a cross-sectional view similar to FIG. 2; A... Automatic adjustment device, 2, 2'... Wheel cylinder, 3, 3'... Brake shoe, 4... Cylinder body (first member), 5... Hydraulic chamber, 6...
Piston (second member), 10, 10'... Return spring, 15... Contact surface, 16... Adjustment nut, 17
... Spring, 18 ... Adjustment rod, 19 ... Quick screw, 2
0...Clutch body, 21...Clutch hole, 22...
...Clutch surface, 23...Seal member, 24...Automatic adjustment release chamber.

Claims (1)

[Scope of utility model registration request] First and second members defining a hydraulic chamber of a wheel cylinder are disposed so as to be non-rotatable and slidable relative to each other, and a brake shoe is actuated by a separating action of the two members due to the hydraulic pressure supplied to the hydraulic chamber. The automatic adjustment device for a hydraulically operated drum brake is configured to be non-rotatably supported by one of the first and second members and to be separable from a contact surface provided on the one member. An adjustment nut that comes into contact with the adjustment nut, a spring that biases the adjustment nut toward the contact side with the abutment surface, an adjustment rod that is screwed into the adjustment nut via a quick screw, and a spring that is fixed to one end of the adjustment rod. a clutch body which is rotatably fitted into a clutch hole provided in the other member of the first and second members and cooperates with a clutch surface formed on the inner wall of the clutch hole; The clutch body is fitted with a sealing member that separates the clutch surface and the hydraulic chamber, and when the clutch body receives a thrust toward the clutch surface due to hydraulic pressure of a certain value or more in the hydraulic chamber, In the clutch body, the automatic adjustment release chamber facing the outer end surface of the clutch body is arranged adjacent to the clutch hole so as to be frictionally coupled to the clutch surface when the clutch receives thrust toward the clutch surface by a return spring of the shoe. An automatic adjustment device for a hydraulically operated drum brake, characterized in that a pressing operation for disengaging the clutch body from the clutch surface can be performed in the automatic adjustment release chamber.