JPS6228328B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, first and second members defining a hydraulic chamber of a wheel cylinder are arranged so as to be non-rotatable and slidable relative to each other, and the hydraulic pressure supplied to the hydraulic chamber is controlled by the hydraulic pressure supplied to the hydraulic chamber. In a hydraulically operated brake that operates a brake shoe or other brake element by the separation action of both parts, the friction of the brake element is automatically compensated to maintain a constant operating gap of the brake element, so that the brake is always maintained. The present invention relates to an automatic adjustment device that allows braking to be reliably performed by a predetermined amount of operation of a brake operator such as a 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 contact 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 and the first and a clutch body which is rotatably fitted into a clutch hole provided in the other member of the second member and cooperates with a clutch surface formed on the back wall of the clutch hole, and a clutch body which is fitted into the other member and which engages the clutch. When the clutch body receives a thrust toward the clutch surface due to the hydraulic pressure of a certain value or more in the hydraulic chamber, and when the clutch body is thrust toward the clutch surface by the return spring of the brake, the clutch body is A device has already been proposed which frictionally engages with the clutch surface when subjected to a thrust toward the clutch surface. 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 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 this automatic adjustment device, in the unlikely event that the seal member is damaged and the hydraulic fluid in the hydraulic chamber leaks to the clutch surface side of the clutch hole, it is necessary to There is a risk that the hydraulic oil will fill up and interfere with the frictional connection of the clutch body to the clutch surface.

An object of the present invention is to provide the automatic adjustment device that eliminates such inconveniences.
The present invention is characterized in that an air reservoir is provided that extends upward from the bag chamber at the back of the clutch hole.

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 left and right wheel cylinders 2,
2' and a pair of upper and lower brake shoes 3, 3' are arranged point-symmetrically around the center of the back plate 1, and a brake drum that surrounds the brake shoes 3, 3' and rotates together with the wheels is not shown. do not have.

Each of the wheel cylinders 2 and 2' has a cylinder body 4 having a cylinder hole 4a with only one end open, and a hydraulic chamber 5 that slides into the cylinder hole 4a.
The cylinder body 4 is fixed to the back plate 1 with bolts 7 and nuts 8. Engagement grooves 9 and 9' are formed in the outer ends of the cylinder body 4 and the piston 6, respectively, and the corresponding ends of the brake shoes 3 and 3' are engaged with these grooves 9 and 9'. , and return springs 10, 10' are tensioned between both brake shoes 3, 3' to maintain the above-mentioned engagement and to bias both brake shoes 3, 3' in the contraction direction. 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 left 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 left wheel cylinder 2 is transferred to the right wheel cylinder 2'. Communication pipe 1 for supplying
2 is connected.

The automatic adjustment device A of the present invention is provided in the hydraulic chambers 5 of both wheel cylinders 2 and 2', and since these have the same structure, only the automatic adjustment device A in the left 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 presses 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 inserted into a bag-shaped clutch hole 21 provided in the inner end wall of the cylinder body 4.
The clutch hole 21 is rotatably fitted into the clutch hole 21.
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 .

A clutch body 20 is located at the dead end of the clutch hole 21.
A bag chamber 24 is defined by the tip of the bag chamber 24.
The air reservoir 25 that extends further upward is the clutch body 2.
Set to 0.

In the illustrated example, an air reservoir 25' extending downward from the bag chamber 24 is further provided. In this way, even if this wheel cylinder 2 is arranged with the piston 6 facing downward like the right wheel cylinder 2', an air reservoir extending upward from the bag chamber 24 can be secured by the 25'. Therefore, there is an advantage that the structure of both wheel cylinders 2, 2' can be made common.

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, this 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 surface 20 separates from the clutch surface 22, the clutch body 20 is moved toward the clutch surface 22 by the said thrust in a helical manner relative to the non-rotatable adjusting nut 16, and re-engages with the clutch surface 22. During this time, the bag chamber 24, air reservoirs 25, 2
The air in the clutch body 20 expands and contracts as the clutch body 20 moves forward and backward, so that the air inside the clutch body 20 expands and contracts.
This does not in any way impede the engagement and disengagement of the vehicle. In this way, a self-adjusting effect takes place which compensates for the friction of the linings of the brake shoes 3, 3'.

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 must be carried out 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, suppose that the hydraulic oil in the hydraulic chamber 5 leaks into the bag chamber 24 due to damage to the seal member 23.
The air in the hydraulic chamber 4 is naturally pushed upward into the air reservoir 25 and does not flow back into the hydraulic chamber 5. Therefore, the air reservoir 25 is not filled with hydraulic oil, and the air reservoir 25 can always hold air.
When a thrust in this direction is applied, the air held in the air reservoir 25 expands and contracts, causing the clutch body 2 to
0 is engaged and disengaged from the clutch surface 22 normally.

FIG. 2 shows a second embodiment of the present invention, which includes a horizontally placed cylinder body 104 and a pair of left and right pistons 106, 10 facing each other with a hydraulic chamber 5 in between.
6', an automatic adjustment device A is constructed between both pistons 106, 106', and an air reservoir 125 is provided in the piston 106 diagonally upward from the bag chamber 24. An air reservoir 125' extending downward and an air reservoir 125'' extending horizontally from the bag chamber 24 are provided in the piston 106 and the clutch body 20, respectively. Air reservoirs 125, 125', 1 extending in the direction
25'', no matter how the wheel cylinder 102 is placed horizontally, vertically, diagonally, etc., one or two of these air pockets 125, 125', 125'' will always be directed upward. Since it can be used as a reservoir, it has a wide range of applications and is convenient.

In FIG. 2, members corresponding to those in FIG. 1 are given the same reference numbers.

As described above, according to the present invention, in the automatic adjustment device configured between the first and second members defining the hydraulic chamber of the wheel cylinder, the air reservoir extends upward from the bag chamber at the back of the clutch hole. Since we have set up
Even if the hydraulic oil in the hydraulic chamber leaks to the clutch surface due to damage to the sealing member, the air reservoir will always have enough air to enable the clutch body to engage and disengage from the clutch surface. There is no risk of interfering with the adjustment function.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional overall front view of a main part of a brake showing a first embodiment of the present invention, and FIG. 2 is a longitudinal partial front view of a main part of a brake showing a second embodiment thereof. 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, 20 ... Clutch body, 21 ... Clutch hole, 22 ... Clutch surface,
23... Seal member, 24... Bag chamber, 25... Upward air reservoir, 102... Wheel cylinder, 10
6... Piston (first member), 106'... Piston (second member), 125... Upward air reservoir, A...
...Automatic adjustment device.

Claims (1)

[Claims] 1. First and second members defining a hydraulic chamber of a wheel cylinder are disposed so as to be non-rotatable and movable relative to each other, and a brake shoe, etc. An automatic adjustment device for a hydraulically operated brake configured to actuate a brake device, the device comprising: a contact surface non-rotatably supported by one of the first and second members and provided on the one member; an adjusting nut that abuts so as to be separable from the adjusting nut; a spring that urges the adjusting nut toward the contact side with the abutting surface; an adjusting rod that is screwed onto the adjusting nut via a quick screw; a clutch body fixed to one end and rotatably fitted into a clutch hole provided in the other of the first and second members, and cooperating with a clutch surface formed on the inner wall of the clutch hole; A sealing member is fitted to the other member to isolate the clutch surface and the hydraulic chamber, and when the clutch body receives thrust toward the clutch surface due to hydraulic pressure of a certain value or more in the hydraulic chamber. and an air pocket extending upward from the bag chamber at the back of the clutch hole, in which the clutch surface is frictionally coupled to the clutch surface when the brake element is thrust toward the clutch surface by the return spring of the brake element. An automatic adjustment device for a hydraulically operated brake, characterized in that it is provided on the other member or the clutch body.