JPS6221785Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention is a two-leading shoe type drum brake device, in particular, a pair of upper and lower wheel cylinders and a pair of left and right brake shoes are placed on the inner surface of a back plate fixed to the vehicle body, and the center of the back plate is attached to the inner surface of the back plate. The wheel cylinders are arranged point-symmetrically around the circumference, and each wheel cylinder has a cylinder body having a cylinder hole having an opening at one end and an anchor existing at the end opposite to the opening, and a cylinder body that is slidably engaged with the cylinder hole and has a cylinder body having a cylinder hole having an opening at one end and an anchor existing at the end opposite to the opening. and a piston defining a hydraulic chamber in the cylinder hole, one end of each brake shoe engages with the piston of one of the wheel cylinders, and the other end engages with the anchor of the other wheel cylinder. The present invention relates to an improvement in a brake shoe equipped with a pair of automatic adjustment devices for preventing relative rotation between the cylinder body and the piston, and expanding and adjusting the brake shoe to compensate for wear of its lining.

In this type of drum brake device, a step is formed on the inner circumferential surface of the brake drum over a long period of time due to sliding friction with the brake shoe, and the brake shoe automatically Since the adjustment device expands and adjusts the brake shoe, for example, when the brake drum is removed in the axial direction to replace the brake shoe, the stepped portion formed on the inner circumferential surface of the brake drum and the brake shoe interfere with each other. This poses a problem in that it may obstruct the release of the brake drum, making it difficult to remove the brake drum.

Conventionally, as shown in Japanese Utility Model Application Publication No. 56-60831, an abutment piece was interposed between the strut of the automatic adjustment device and the parking brake lever, and the abutment piece was Once removed, the brake shoe is further retracted from its normal non-operating position, sufficiently widening the gap between the brake shoe and the brake drum, and even if there is a step formed on the inner circumferential surface of the brake drum due to wear, it will not get in the way. It is known that the brake drum can be easily removed in the axial direction without being damaged.

By the way, the above-mentioned means for contracting the brake shoe to facilitate detachment of the brake drum can only be applied to a type of drum brake equipped with a parking brake lever, and its scope of application is limited. .

In general, in drum brake systems, when strong braking is performed, elastic deformation occurs in each part of the brake, but this elastic deformation appears to cause wear on the lining of the brake shoe, and when the automatic adjustment device responds to this, over-adjustment occurs. (over-adjustment) occurs. As a result, when the brake is released, there is no operating clearance for the brake shoe, resulting in an inconvenient dragging phenomenon. Conventionally, various automatic adjustment devices equipped with over-adjustment prevention functions have been proposed to eliminate such inconveniences, but since they are installed outside the hydraulic chamber of the wheel cylinder,
There are drawbacks that prevent the drum brake device from becoming more compact.

Therefore, the present invention has a wide range of applicability, allows the brake shoe to be easily retracted from the normal non-operating position, regardless of the presence or absence of a parking brake lever, and has an automatic adjustment function that prevents over-adjustment. To provide the drum brake device described above, in which the device is provided in each wheel cylinder to achieve compactness, and the retracting means is attached by a component of an automatic adjustment device to simplify the mounting structure of the retracting means. The purpose is to

In order to achieve the above object, the present invention provides that each automatic adjustment device includes an adjustment nut that is located in the hydraulic chamber, is non-rotatably supported by the piston, and abuts on the contact surface of the piston in a separable manner; a spring that biases the nut toward the contact side with the contact surface; an adjustment rod that is screwed into the adjustment nut via a quick screw;
a clutch body fixed to one end of the adjustment rod and rotatably fitted into a bag-shaped clutch hole communicating with the hydraulic chamber and cooperating with a clutch surface formed on a back wall of the clutch hole; a sealing member fitted into the hole to isolate the clutch surface and the hydraulic chamber; a ventilation hole opening on the outer surface of the anchor to communicate the air chamber at the back of the clutch hole with the atmosphere; a screw plug that is screwed into the air hole and removed from the outside; a frictional connection with the clutch surface when receiving thrust toward the clutch surface by a return spring, and a spacer piece is interposed at the abutting portion between each anchor and each brake shoe so as to be removable from the outside; The present invention is characterized in that a mounting piece integral with the spacing piece is attached to the outer surface of the anchor using the screw plug.

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

First, in FIG. 1, 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, respectively. The brake drums surrounding the brake shoes 3, 3' and rotating together with the wheels are not shown.

Each of the wheel cylinders 2 and 2' includes a cylinder body 4 having a cylinder hole 4a having an opening at one end, and a piston 6 that slides into the cylinder hole 4a to define a hydraulic chamber 5. However, the cylinder body 4 is fixed to the back plate 1 with bolts 7. Cylinder hole 4a of cylinder body 4
An anchor 8 is integrally formed at the end opposite to the opening, and engagement grooves 9, 9' are formed at the outer ends of the anchor 8 and the piston 6, respectively. Corresponding ends of the brake shoes 3, 3' are engaged with these grooves 9, 9', and both brake shoes 3,
Return springs 10, 10' are tensioned between the brake shoes 3' and 3' to maintain the engagement and bias both brake shoes 3 and 3' in the direction of contraction. The engagement between the grooves 9, 9' and the brake shoes 3, 3' prevents relative rotation between the cylinder body 4 and the piston 6.

The upper wheel cylinder 2 is provided with a hydraulic pressure introduction port 11 for introducing the output hydraulic pressure of a brake master cylinder (not shown) into its hydraulic chamber 5.
Further, a communication pipe 12 is connected between both wheel cylinders 2, 2' for supplying the hydraulic pressure introduced into the upper wheel cylinder 2 to the lower wheel cylinder 2'.

Since automatic adjustment devices A are provided in both wheel cylinders 2, 2' and have the same structure, only the automatic adjustment device A in the upper wheel cylinder 2 will be described in detail below. A stepped hole consisting of a large diameter hole 13 and a small diameter hole 14 facing the hydraulic chamber 5 is provided on the inner end surface of the piston 6, and the stepped portion of the stepped hole is formed into a conical contact 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 presses the adjustment nut 16 toward the contact surface 15 is attached to the piston 6.
is fixed to. The spring 17 is attached to the adjusting nut 16
In addition to having the function of pressing and holding against the contact surface 15,
The spring 17 and the adjusting nut 16 also have a rotation preventing function due to the frictional engagement or the uneven engagement with the adjusting nut 16.

An adjustment rod 18 is screwed into the center of the adjustment nut 16 via a quick screw 19 so as to pass through it.
One end thereof is received in the small diameter hole 14. At the threaded joint between the adjustment nut 16 and the adjustment rod 18, there is a shaft that corresponds to the appropriate operating clearance of each brake shoe 3, 3', that is, the appropriate clearance between each brake shoe 3, 3' and a brake drum (not shown). There is a play in the 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 rotatable into a bag-shaped clutch hole 21 provided in the inner end wall of the cylinder hole 4a and communicating with the hydraulic chamber 5. 2, and faces a conical clutch surface 22 formed on the back wall of the clutch hole 21. Clutch hole 21
A sealing member 23 for preventing the hydraulic pressure in the hydraulic chamber 5 from acting on the clutch surface 22 is fitted therein.

An air chamber 24 is defined at the back of the clutch hole 21 by the tip of the clutch body 20, and a ventilation hole 25 that communicates this air chamber 24 with the atmosphere opens on the outer surface of the anchor 8. It is closed by a screw plug 26. The screw plug 26 is equipped with a locking nut 27. Therefore, when assembling automatic adjustment device A,
By removing the screw plug 26 and opening the air chamber 24 to the atmosphere, the clutch body 20 can be easily fitted into the clutch hole 21 without being resisted by the air within the air chamber 24.

A spacing piece 28 made of a steel plate is interposed between the anchor 9 and the corresponding brake shoe 3, 3', and in order to define the interposed position, the anchor 8
A positioning protrusion 29 with which the tip of the spacing piece 28 engages is provided on the bottom surface of the engagement groove 9 . The thickness of the spacer piece 28 is set to be larger than the maximum allowable depth of a step formed on the inner peripheral surface of the brake drum due to wear. The spacing piece 28 integrally includes a mounting piece 28 a bent so as to overlap the outer surface of the anchor 9 . This mounting piece 28a is provided with a mounting hole 30 and a tool hole 31, and the mounting piece 28a is mounted on the anchor 9 by passing the screw plug 26 through the mounting hole 30 and tightening the lock nut 27. On the other hand, a screw plug 26, a lock nut 27, and a mounting piece 2 are attached to the end wall plate of the brake drum (not shown).
A work window 32 is provided that allows operation of the device 8a from the outside.

Next, to explain the operation of this embodiment, in order to perform braking, a brake master cylinder (not shown) is operated, and its output oil pressure is transferred to the upper wheel cylinder 2.
If the hydraulic pressure is supplied to the hydraulic chamber 5 of
Since the oil pressure is also supplied to the lower wheel cylinders 2' through the hydraulic pressure, the pistons 6 of each wheel cylinder 2, 2' move outward and expand the corresponding brake shoes 3, 3'. It is brought into pressure contact with the inner circumferential surface of a brake drum (not shown) 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 air in the air chamber 24 expands and contracts as the clutch body 20 moves forward and backward, so that 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 2 through the piston 6, adjustment nut 16 and adjustment rod 18.
0 acts as a thrust toward the clutch surface 22, thereby causing the clutch body 20 to move toward the clutch surface 22.
Frictional coupling occurs, making rotation impossible. Therefore,
Since relative rotation between the adjusting nut 16 and the adjusting rod 18 is also impossible, the piston 6 and the adjusting nut 16 are
The stroke can only be retreated by the amount of play between the threaded part of the adjusting nut 16 and the adjusting rod 18, and as a result, there is a gap between the lining of each brake shoe 3, 3' and the inner peripheral surface of the brake drum. An appropriate gap is created that corresponds to the play.

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 1
8 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 action is stopped and over-adjustment is prevented.

Next, when removing the brake drum for replacing brake shoes 3, 3' with new parts, etc.,
The work window 32 provided on the brake drum is attached to the mounting piece 28
Rotate the brake drum so that it is in a position opposite to a, insert a suitable tool through the working window 32, loosen the lock nut 27, remove the screw plug 26, and then hook the tool into the tool hole 31 to remove the spacing piece 28. Pull it out from between the anchor 9 and the brake shoes 3, 3'.
Then, each brake shoe 3, 3' is connected to the spacer piece 28.
Since the brake drum contracts by an amount equivalent to the thickness of the brake drum, a sufficient gap is secured between these and the brake drum to facilitate the axial removal of the brake drum.

The pulled out spacing piece 28 is attached to the brake shoe 3,
Needless to say, when 3' is removed, it is fixed again to the anchor 9.

As described above, according to the present invention, an automatic adjustment device is configured between the cylinder body and the piston that define the hydraulic chamber of the wheel cylinder, and when the oil pressure in the hydraulic chamber exceeds a predetermined value, the adjustment function of the automatic adjustment device is activated. Since the brake is stopped, it is possible to avoid over-adjustment of the automatic adjustment device due to elastic deformation of various parts of the brake during strong braking that increases the oil pressure in the hydraulic chamber above a predetermined value, and the dragging phenomenon caused by over-adjustment can be avoided. can be prevented. Furthermore, since the automatic adjustment device is provided inside the wheel cylinder, it does not interfere with brake components outside the wheel cylinder, contributing to the compactness of the drum brake device, and the movable part of the automatic adjustment device Since it is constantly lubricated by the hydraulic oil in the hydraulic chamber, the automatic adjustment device can always operate smoothly and accurately without any special lubrication measures.

Furthermore, the air chamber at the back of the clutch hole is communicated with the atmosphere through a ventilation hole, and a screw plug is screwed into the ventilation hole, so that by removing the screw plug during assembly, the clutch can be inserted into the bag-shaped clutch hole. The clutch body can be easily inserted, and by attaching a screw plug after assembly, it is possible to reliably prevent dust from entering the clutch hole and ensure normal operation of the clutch body.

In addition, a spacer piece that can be removed from the outside is interposed at the contact part between the anchor and the brake shoe, and the screw plug that attaches the mounting piece of the spacer piece to the anchor is removed from the outside, so simply remove the screw plug. By simply pulling out the spacing piece, the brake shoe can be retracted from its normal non-operating position and the gap between the brake shoe and the brake drum can be widened, thereby eliminating the step caused by wear on the inner circumferential surface of the brake drum. Even if the brake drum is formed, the brake drum can be easily removed in the axial direction without causing interference between the stepped portion and the brake shoe.

Furthermore, the spacing piece can be installed regardless of whether or not there is a parking brake lever, and has a wide range of applications.

Furthermore, the spacing piece also has the function of protecting the contact surface of the anchor with the brake shoe from abrasion, so that a reinforcing plate that is generally cast into the end face of the anchor is not required.

Furthermore, when attaching the spacing pieces, there is no need for a dedicated mounting means for the spacing pieces, so the mounting structure for the spacing pieces can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional overall front view of essential parts of a drum brake device showing one embodiment of the present invention, FIG. 2 is a sectional view taken along the line -- in FIG. 1, and FIG. 3 is a perspective view of a spacing piece. A... Automatic adjustment device, 1... Back plate,
2, 2'... Wheel cylinder, 3, 3'... Brake shoe, 4... Cylinder body, 4a... Cylinder hole, 5... Hydraulic chamber, 6... Piston, 8...
Anchor, 10, 10'... Return spring, 15... Contact surface, 16... Adjustment nut, 17... Spring, 18
... Adjustment rod, 19 ... Quick screw, 20 ... Clutch body, 21 ... Clutch hole, 22 ... Clutch surface,
23... Seal member, 24... Air chamber, 25...
Ventilation hole, 26...Screw plug, 27...Lock nut, 28...Spacer piece, 28a...Mounting piece, 30...
Mounting hole, 31...tool hole, 32...work window.

Claims (1)

[Scope of utility model registration request] A pair of upper and lower wheel cylinders and a pair of left and right brake shoes are arranged point-symmetrically around the center of the back plate on the inner surface of a back plate that is fixed to the vehicle body, and each wheel cylinder is a cylinder having an opening at one end. Each brake shoe has a cylinder body having a hole and an anchor located at an end opposite to the opening, and a piston that is slidably engaged with the cylinder hole to define a hydraulic chamber within the cylinder hole. One end engages with the piston of one of the wheel cylinders, and the other end engages with the anchor of the other wheel cylinder to prevent relative rotation between the cylinder body and the piston, and the brake shoe In a two-leading shoe type drum brake device equipped with a pair of automatic adjustment devices that expand and adjust to compensate for wear of the lining, each automatic adjustment device is located within the hydraulic chamber and is non-rotatably supported by the piston. an adjustment nut that contacts the contact surface of the piston in a separable manner; a spring that biases the adjustment nut toward the contact side with the contact surface; and a spring that is screwed into the adjustment nut via a quick screw. an adjusting rod, and a clutch body that is fixed to one end of the adjusting rod and is rotatably fitted into a bag-shaped clutch hole communicating with the hydraulic chamber, and cooperates with a clutch surface formed on the back wall of the clutch hole. a sealing member fitted into the clutch hole to isolate the clutch surface and the hydraulic chamber; and a vent opening on the outer surface of the anchor to communicate the air chamber at the back of the clutch hole with the atmosphere. and a screw plug that is screwed into the vent hole and removed from the outside, 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, A spacing piece is provided at the abutting portion between each anchor and each brake shoe so as to be removable from the outside so as to be frictionally coupled to the clutch surface when the brake shoe receives thrust toward the clutch surface by the return spring of the brake shoe. A two-leading shoe type drum brake device, characterized in that a mounting piece integrated with the spacing piece is attached to the outer surface of the anchor by the screw plug.