JP2002523286A - Air dryer - Google Patents

Abstract

(57) [Summary] An air dryer (13) for a vehicle brake system (14), wherein an inlet (16) connected to an intermittent pressure source (11) and an outlet connected to a vehicle brake system (14). (23) and two independent air drying chambers (19, 20) connected between the inlet and the outlet, connecting one of the chambers between the inlet and the outlet, and connecting the other of the chambers so that they can be regenerated. Control means (17, 18, 39) functioning to perform alternately. An air dryer wherein the control means includes a timer (39) for changing the chamber after a predetermined time, and the operation of the timer (39) is stopped when the pressure source is stopped during use.

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to air dryers, and more particularly to double or twin air dryers for vehicle brake systems.

[0002] Vehicles with air brake systems, typically heavy commercial vehicles and buses, require dry air for safe and effective operation of system components. Therefore, an air dryer is provided immediately downstream of a general air compressor.

[0003] A typical air dryer has a desiccant chamber through which pressurized air travels to a brake system. Periodic drying of the desiccant is achieved by flowing a certain amount of dry air from the system through the desiccant and into the atmosphere. Of course, such drying or regeneration must be performed when the compressor is off.
Such dry air for regeneration is supplied from a system volume, for example a pneumatic tank.

If the brake system is used repeatedly at short intervals, for example, in a city bus system, there is little time available for regeneration. In order to solve this problem, a double chamber or twin air dryer system is provided so that each drying chamber can alternately use a system controlled by a timer or the like.

[0005] However, many factors affect the need for regeneration, including the volume of air used in the brake system and the relative humidity of the incoming air. One problem with double or twin air dryers is that the timer alternates between the drying chambers regardless of the compressor operating conditions. In these situations, the compressor and one of the drying chambers may become locked in phase, one of the drying chambers saturating and the other drying chamber may be used little or no.

[0006] To minimize the possibility of saturation, some existing systems rely on drying of both chambers when the compressor is off, regardless of previous drying conditions and / or time. Regenerate the agent, which will result in inefficient waste of dry air.

According to the present invention, there is provided an air dryer for a vehicle brake system, comprising an inlet connected to an intermittent pressure source, an outlet connected to the brake system, and an air dryer connected between the inlet and the outlet. Two independent air drying chambers and a control operative to alternately connect one of the chambers between an inlet and an outlet and connect the other of the chambers to the atmosphere to allow it to dry. Means, the control means including a timer for changing the chamber after a predetermined time, wherein the operation of the timer is stopped when the pressure source is stopped during use. ing.

[0008] Such an apparatus can effectively use each drying chamber and effectively dry an inactive air dryer.

Preferably, the pressure source is an engine-driven compressor whose operation is turned on and off by a governor signal, and the absence of the governor signal causes the timer to:
It is preferably activated via an electronic controller. Since drying is only required during the operation of the compressor, regeneration air can be supplied directly from the compressor rather than from the system volume. In this way, unnecessary consumption of system volume is avoided, and when the brake system is not functioning, for example, when driving continuously on a highway or when the engine is stationary with the engine running. There is no need to operate the compressor. In a preferred embodiment, the governor signal is a fluid pressure signal and the timer is deactivated by a piston operated actuator directly in response to said signal. Preferably, the actuator is elastically biased to activate the timer.

[0010] Preferably, the dryer is responsive to the timer to connect an electrically actuated pilot downstream of the dryer to a respective control valve operative to connect a pressure source to a respective air drying chamber. Including valve.

In a preferred embodiment, the control valve is elastically biased such that each air drying chamber is connected to a pressure source. Preferably, the control valves are also operable to connect each drying chamber to the atmosphere.

[0012] In a preferred embodiment, the downstream side of the drying chamber is connected via a fluid restriction.
Preferably, the downstream side of the drying chamber is connected to the outlet via a respective check valve.

In another embodiment, the air dryer control means can be operative to connect both air drying chambers in parallel between the inlet and the outlet. Such a mode of operation may be particularly useful where large volumes of dry air are needed immediately. The control means can be configured to prevent both drying chambers from saturating, so that the air dryer can return to the alternating operating cycle.

[0014] Other features of the present invention will become apparent from the following description of a preferred embodiment, given by way of example only, in the accompanying drawings, which schematically show, in part, a portion of a vehicle airbrake system.

The drawing receives the air indicated by arrow 12 and pressurizes the air into an air dryer 13.
1 shows an engine-driven compressor 11 for use in a vehicle airbrake system 14. When necessary, a governor pressure signal 15, described below, turns on the compressor.

The air dryer 13 includes an inlet 16 from which air is supplied to respective control valves 17,
18 to drying chambers 19, 20 and from there via check valves 21, 22 to outlet 23
Flows to The air dryer is connected via a fluid restriction 24 immediately downstream thereof.

The control valves 17, 18 are identical, each having two flow states. The first state is represented by the valve 17, the air dryer 19 is connected to the atmosphere, and the connection from the inlet 16 is closed. The second state is represented by a valve 18 and the inlet 16 is connected to an air dryer 20.
20.).

The control valves 17, 18 are biased to a second state by respective springs 25, and the first is determined by the presence or absence of fluid pressure acting against the springs via respective pilot valves 26, 27. It can be moved to the state.

The pilot valves 26 and 27 control the supply of pressurized air to the control valves 17 and 18,
Pressurized air is supplied from connections on the downstream side of the respective check valves 21 and 22. The pilot valves 26, 27 are identical and are movable between the two states by respective electric solenoids 28. In the open state, represented by valve 26, pressurized air is supplied to control valve 17, which presses spring 25 to open chamber 19 to atmosphere. In the closed state represented by the pilot valve 27, the supply of pressurized air is shut off and the signal line leading to the control valve 18 is connected to the discharge.

A governor pressure tube 31 supplies pressurized air to a governor valve 32. Although this tube 31 is shown connected to outlet 23, it is appropriate to provide some suitable tapping of system pressure.

The governor valve 32 determines whether to turn on the compressor and has two positions. As shown, the valve is biased to the right by a return spring 33 to shut off the supply of pressurized air from port 23 and to discharge governor pressure signal 15. In this state, the operation of the compressor is on, and pressurized air is supplied through the drying chamber 20.

When system requirements are met, such as by one or more pressure switches indicating that the pressure in the system 14 is at a desired level, the governor valve is connected to the compressor by a means (not shown) connecting the pressure line 31 to the compressor. It moves to the left, thus giving a positive pressure signal 15 to turn off the compressor. The governor valve can be moved, for example, by the action of system pressure against the spring 33 and a suitable snap-action spool valve.

The timer actuator 34 has a piston 35 that moves against a return spring 36 by the pressure signal 15. A power supply 37 supplies power to a timer 39 via a switch 38, the output of the timer being connected to a respective energisation line 40,
It is connected to one of the solenoids 28 via 41.

As shown, switch 38 is closed by piston 35 under the action of return spring 36 and the absence of governor pressure signal 15 indicates that the compressor is on due to system demands. ing. In this state, the timer is operating, and the drying chamber 19 is being regenerated by the throttle airflow from the downstream of the drying chamber 20 as shown in the figure.

When a predetermined time elapses while the compressor is on, the timer causes the pilot valve 26 to move to the closed state and the pilot valve 27 to move to the open state. As a result, the control valves 17 and 18 are switched, and the air is dried by the drying chamber 19, so that the drying chamber 20 can be regenerated.

When the operation of the compressor is turned off by the governor pressure signal 15, the piston 3
5 moves to the left in the drawing and opens the switch 38, which causes the timer 39
Operation is stopped. In this way, the possibility of in-phase locking of the compressor and one of the drying chambers is minimized, so that saturation of one of the air drying chambers is avoided.

The circuit diagram shown is schematic, and by appropriately combining the components thereof, a compact air dryer device can be provided. In particular, common components associated with each drying chamber can be incorporated into a fixture for a removable desiccant canister. Preferably, the canister fittings are identical, except that a structure that includes a governor valve and / or a timer mechanism can prevent one of the fittings from being used. Alternatively, the control devices may be housed individually.

[Brief description of the drawings]

FIG.

[Procedural Amendment] Submission of translation of Article 34 Amendment of the Patent Cooperation Treaty

[Submission date] July 10, 2000 (2000.7.10)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction contents]

Preferably, the dryer includes a pilot valve that electrically functions to connect pressurized air downstream of the dryer to a respective control valve in response to the timer.
Only, the control valves operate to connect a pressure source to each air drying chamber.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction contents]

The control valves 17, 18 are identical, each having two flow states. The first state is represented by the valve 17, the air dryer 19 is connected to the atmosphere, and the connection from the inlet 16 is closed. The second state is represented by valve 18 and inlet 16 is air
It is connected to the dryer 20.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction contents]

The control valves 17, 18 are biased to a second state by respective springs 25, and a fluid acting against the springs via respective pilot valves 26, 27.
The first state can be moved by pressure .

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction contents]

When the operation of the compressor is turned off by the governor pressure signal 15, the piston 3
5 moves to the right in the drawing and opens the switch 38, which causes the timer 39
Is stopped. In this way, the possibility of synchronized phase locking of the compressor and one of the drying chambers is minimized, so that saturation of one of the air drying chambers is avoided.

[Procedural Amendment] Submission of translation of Article 34 Amendment of the Patent Cooperation Treaty

[Submission date] October 11, 2000 (2000.10.11)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

Claims (10)

[Claims] 1. An air dryer for a vehicle brake system, comprising an inlet connected to an intermittent pressure source, an outlet connected to a brake system, and two independent air dryers connected between the inlet and the outlet. And a control means operative to connect one of the chambers between the inlet and the outlet and alternately connect the other of the chambers to the atmosphere to allow it to dry. An air dryer wherein the control means includes a timer for changing the chamber after a predetermined time, the timer being stopped when the pressure source is stopped during use. 2. The pressure source is turned on and off (o) by a governor signal.
2. The air dryer of claim 1 wherein the timer is started when the governor signal is absent and the timer is started. 3. The air dryer according to claim 2, further comprising a piston-operated actuator that stops the timer in response to the governor signal. 4. The air dryer according to claim 3, wherein the actuator is elastically biased so that the timer is started. 5. An air-operated pilot valve and a control valve, the pilot valve connecting the pressurized air downstream of the dryer in response to the timer and connecting the pressure source to a respective air drying chamber. An air dryer according to any one of the preceding claims, which is connected to a respective control valve operative for the air dryer. 6. The air air dryer according to claim 5, wherein the control valve is elastically biased so that each air drying chamber is connected to the pressure source. 7. The air dryer of claim 6, wherein the control valves are operable to connect each drying chamber to the atmosphere. 8. An air dryer according to claim 1, wherein the downstream side of the drying chamber is connected via a fluid restriction. 9. The air dryer according to claim 1, wherein a downstream side of the drying chamber is connected to the outlet via a respective check valve. 10. An air dryer substantially as hereinbefore described with reference to the accompanying drawings.