JPH08268262A - Piston stroke detector - Google Patents

Abstract

PURPOSE: To provide a piston stroke detector that is simple in a switch and its operating mechanism, straightforward in assembly as there is no need of any exterior fitting as well as to enable it at a low cost as dispensing with any complicated molds and punches, and besides, having its apparatuses made capable to be compact in size and lighter in weight. CONSTITUTION: In an air over hydraulic booster which converts any air pressure, being received by an air piston 1 installed in an air cylinder 2a, into hydraulic pressure, a conductor 3 is resileably installed in the air cylinder 2 at the terminal side of a stroke of the air piston 1, while a contact point to get closer to this conduct 3 is installed there, and a head part of the air piston 1 presses the conductor 3 at a stroke position exceeding the specified position of the air piston 1, whereby the conductor 3 and the contact point are made up so as to be conducted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston stroke detecting device, and more particularly, to a device applied to an air over hydraulic brake booster.

[0002]

2. Description of the Related Art Conventionally, an air over hydraulic brake booster has been used as a brake booster for a vehicle. An air piston is provided in the air cylinder, and the air pressure received by the air piston is converted into hydraulic pressure and output. In such a brake booster, if the wear of the brake lining is promoted or if liquid leakage occurs in the brake system, the stroke amount of the air piston also increases.

Therefore, it is conceivable to provide a device for detecting the piston stroke in the air cylinder in order to detect the abnormality of the brake system. As an example, there is one in which a detection rod is slidably provided on the inner surface of the casing on the end side of the stroke of the air piston, and a switch provided separately is operated by the movement of the detection rod (Japanese Patent Publication No. 62-22825). ). While the rod is provided with a recess, the operating end of the switch is brought into contact with this recess, and when the detection rod is pushed by the air piston, the recess is disengaged from the operating end of the switch and the switch is turned on. It is supposed to be. This switch is set to operate in accordance with the piston stroke when the clearance between the brake lining and the brake drum becomes a predetermined value or more due to wear of the brake lining.

[0004]

However, in the above-mentioned conventional device, a large number of parts are required for the switch and its operating mechanism, so that the assembly becomes complicated. Also, since the switch is externally fixed to the casing with bolts, the size of the device becomes large and the weight also increases. Furthermore, there is a problem that the processing cost is increased because a complicated mold and perforation for providing the switch and the rod on the casing are required.

The present invention has been made in view of the above matters, and it is a technical object to provide a piston stroke detection device which is simple to assemble because the switch and its operating mechanism are simple and no external attachment is required. .

Further, it is a technical object to provide a piston stroke detecting device which can be constructed at a low cost without requiring a complicated mold or perforation. Moreover, it is a technical object to provide a piston stroke detection device that can reduce the size and weight of the device.

[0007]

In order to solve the above technical problems, the present invention provides an air over hydraulic booster for converting the air pressure received by an air piston 1 installed in an air cylinder 2a into a hydraulic pressure as follows. It was configured like this.

That is, according to the first aspect of the invention, the conductor 3 is provided in the air cylinder 2a at the end of the stroke of the air piston 1 so that the conductor 3 can repel and the contact 4 brought close to the conductor 3 is provided. The head of the air piston 1 presses the conductor 3 at a stroke position beyond a predetermined position of the air piston 1 so that the conductor 3 and the contact 4 are electrically connected.

Here, the end side of the stroke means the position where the air piston is moved by the air pressure. Further, the conductor 3 can be configured by a band-shaped elastic metal plate such as brass, steel, and stainless steel. The contact point 4 can be formed by embedding a round head rivet in an insulator, in addition to a conductor plate.

In the structure of claim 2, the conductor 3 is a leaf spring curved along the peripheral surface of the head surface of the air piston 1, and one end 5 of the leaf spring is formed in the air cylinder 2.
It was fixed to the a side, and the other end 6 was positioned away from the air cylinder 2a side (floating) so that it could contact the air piston 1. The conductor 3 can be formed in an arc shape (fan shape). An insulating cap can be provided on the other end 6 side.

[0011]

The air piston 1 is moved by the air pressure, and the hydraulic system operates accordingly. At this time, in normal operation, the air piston 1 does not reach the end of the stroke, and there is a sufficient margin.

Here, if excessive wear of the brake lining of the vehicle or brake fluid leakage occurs, the air piston 1 will move beyond the above-mentioned safety stroke. Then, the head of the air piston 1 contacts the conductor 3 provided in the air cylinder 2a,
Is bent, and the conductor 3 and the contact 4 come into contact with each other.

As a result, the conductor 3 and the contact 4 are electrically connected to each other, so that an alarm lamp or the like can be appropriately turned on.
In this way, the excess stroke can be detected with a simple configuration.

Further, in the structure of claim 2, the conductor 3
Is formed into a leaf spring shape curved along the peripheral surface of the head surface of the air piston 1, so that the conductor 3 can be easily installed in the air cylinder 2a without changing the shape of the air cylinder 2a. it can. Also, the air piston 1
The excessive stroke of is absorbed by the elastic force of the conductor 3.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. In this embodiment, an air cylinder 2a integrated with a casing 2 is equipped with an air piston 1, and the air pressure received by the air piston 1 is transmitted to a hydraulic piston 10 by a rod 1a and converted into hydraulic pressure. It is applied to Rick Booster.

An air seal 1b is provided on the outer periphery of the air piston 1 to prevent air leakage. An inlet 12 connected to a reservoir (not shown) is provided at a connecting portion between the rod 1a and the hydraulic piston 10. Further, the casing 2 is provided with a breather 13 which communicates with the inside of the air cylinder 2a. The hydraulic piston 10 is internally fitted in a hydraulic cylinder 14 which is integral with the casing 2, and an outlet 15 connected to a wheel cylinder (not shown) is provided at the tip of the hydraulic cylinder 14. .

On the other hand, a partition wall 16 and an air control valve 17 fixed to the partition wall 16 are provided on the front side of the air piston 1 (on the side opposite to the casing 2). The air control valve 17 is connected to an air source (not shown) so that pressurized air can be fed into the air cylinder 2a.

A switch assembly 18 is provided on the inner surface of the air cylinder 2a on the trailing end side (casing 2 side) of the stroke of the air piston 1. A return spring 11 is inserted between the switch assembly 18 and the air piston 1.

The switch assembly 18 has a ring-shaped base 19 made of an insulating material, an arc-shaped plate spring conductor 3 attached to the base 19, and the conductor 3 formed on the base 19. Holding cover 20 that is sandwiched between
It consists of and. As shown in FIG. 3, the base 19 has a guide portion 21 formed on an inner peripheral portion thereof for guiding the return spring 11. In addition, a dowel 22 for mounting the conductor 3 on the base 19,
23 is formed.

On the other hand, the conductor 3 is provided with the dowels 22 and 23.
The mounting holes 24 and 25 corresponding to the above are provided, and the hole portion 27 for mounting the insulator 26 is provided at one end of the conductor 3. This conductor 3 is attached to the base 19.
A contact 4 is provided at a position overlapping with. That is, one end 5 of the conductor 3 is fixed to the casing 2 side of the inner surface of the air cylinder 2a, and the other end 6 of the conductor 3 is held away from the inner surface of the air cylinder 2 (floating state). . Then, below the other end 6 of the conductor 3 (see FIG.
Contact 4 is located in the middle), and in the normal state, the conductor 3 and the contact 4
And are separated from each other. An initial force is applied to the conductor 3 in a direction away from the contact 4 so that the conductor 3 does not come into contact with the contact 4 due to vibration of the air cylinder.

The contact 4 is a substantially L-shaped metal plate as shown in FIG. 3, and is integrated with the base 19 by a dowel 37. Then, the contact point 4 is pressed by a convex portion 28.
Is provided. A groove 29 is formed in the base 19 at a position where the convex portion 28 is located.

The pressing cover 20 has the dowels 22,
2 are provided with fixing holes 30 and 31 for fixing 23.
It is fastened by heat welding as shown in. Further, a taper 32 is provided on the rear surface side (base 19 side) of the pressing cover 20 at the position where the contact 4 is located.

Cords are connected to the conductor 3 and the contact 4, respectively, and the wiring is as shown in FIG. That is, the wire harness 33 is led out from the conductor 3 and the contact 4, and the warning lamp L and the power source BT are connected in series between the conductor 3 and the contact 4. A connector is preferably used for this connection.

With the above-mentioned structure, the insulator 26 faces the air piston 1 and is pressed near the maximum stroke of the air piston 1. The operation of this embodiment will be described below.

The air piston 1 is moved by the air pressure, and the hydraulic system operates accordingly. At this time, in normal operation, the air piston 1 does not reach the end of the stroke, there is a sufficient margin, and the air piston 1 does not contact the conductor 3. Then, if excessive wear of the brake lining of the vehicle or brake fluid leakage occurs, the air piston 1 will move beyond the above-mentioned safe stroke. Then, the head of the air piston 1 contacts the insulator 26 to push down the conductor 3 and bring the conductor 3 and the contact 4 into contact with each other.

As a result, the conductor 3 is electrically connected to the contact 4, so that the warning lamp L is turned on. Since the conductor 3 is an arc-shaped leaf spring, a sufficient working stroke of the air piston 1 can be obtained and reliability is also improved.

The relationship between the stroke (S) of the air piston 1 and the switch in FIGS. 1 and 2 will be described.
At the stroke S1, the air piston 1 and the insulator 2
6 comes into contact, and the switch is turned on at stroke S2.
The stroke S3 is the maximum stroke of the air piston 1, and the stroke S4 is the stroke after the switch is turned on. After the switch is turned on, the on state is maintained even if the conductor 3 is further pressed by the air piston 1.

As described above, by detecting the excessive stroke of the air piston 1, it is possible to detect the abnormality of the brake system.

[0029]

According to the present invention, a conductor is elastically provided in the air cylinder, and a contact close to the conductor is brought into contact with the conductor to operate the switch in an excessive stroke of the air piston. As configured.

Therefore, the switch and its actuating mechanism are simple and there is no need for external attachment, so that the assembly is simple. Furthermore, since complicated molds and perforations are not required,
In addition to reducing the number of parts, it can be constructed at low cost. In addition, the device can be reduced in size and weight.

Since the conductor is an arc-shaped leaf spring, it is possible to easily assemble the conductor in the air cylinder without the need to separately provide a component for imparting elastic force to the conductor.

[Brief description of drawings]

FIG. 1 is an overall sectional view showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view around a conductor taken along the line BB of FIG.

FIG. 3 is a front view of components centering on the base of the embodiment.

FIG. 4 is a front view of a conductor of the example.

FIG. 5 is a front view of the pressing cover of the embodiment.

FIG. 6 is a front view of the periphery of the conductor as seen from the direction A in FIG.

[Explanation of symbols] 1 ... Air piston 1a Rod rod 1b Air seal 2 Casing 2a Air cylinder 3 Conductor 4 Contact point 5 One end of conductor 6 Other end of conductor 10・ Hydraulic piston 11 ・ ・ Return spring 12 ・ ・ Inlet 13 ・ ・ Breazer 14 ・ ・ Hydraulic cylinder 15 ・ ・ Outlet 16 ・ ・ Differential wall 17 ・ ・ Air control valve 18 ・ ・ Switch assembly 19 ・ ・ Base 20 ・ ・Pressing cover 21 .. Guide part 22, 23 .. Dowel 24, 25 .. Mounting hole 26 .. Insulator 27 .. Hole part 28 .. Convex part 29 .. Groove 30.31 .. Fixing hole 32 .. Taper 33 .. Wire harness 37 .. Dowel BT .. Power supply L ..

Claims (2)

[Claims] 1. In an air-over-hydraulic booster for converting air pressure received by an air piston installed in an air cylinder into liquid pressure, a conductor is elastically provided in the air cylinder at the end side of the stroke of the air piston. And a contact close to the conductor is provided, and the head of the air piston presses the conductor at a stroke position beyond a predetermined position of the air piston so that the conductor and the contact are electrically connected. And piston stroke detector. 2. The conductor is in the form of a leaf spring curved along the peripheral surface of the head surface of the air piston, and has one end fixed to the air cylinder side and the other end fixed to the air cylinder side. 2. The piston stroke detection device according to claim 1, wherein the piston stroke detection device is located away from the air piston so that the air piston can come into contact with the air piston.