GB2133580A

GB2133580A - Improvements in or relating to compressed-air systems of vehicles

Info

Publication number: GB2133580A
Application number: GB08327358A
Authority: GB
Inventors: Siegfried Beck; Ingolf Grauel; Griesheim Alexander Von; Gunther Henzler; Egbert Muller
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1982-10-13
Filing date: 1983-10-13
Publication date: 1984-07-25
Also published as: SE454162B; FR2534538A1; FR2534538B1; SE8304968L; SE8304968D0; GB8327358D0; DE3307327A1; GB2133580B

Abstract

In a compressed-air brake system for vehicles, a compressor 11 is switched on when overrun and/or braking of the vehicle is detected by a sensor 20. The sensor 20 acts upon a control device (21) and renders the compressor operative when overrun or braking has been detected, and renders it inoperative upon termination of the overrun or braking. There may be a time delay before the compressor is halted. As shown the sensor 20 responds to thrust reversal in the region of the vehicle gear box 18. A pressure controller 15 is between the compressor and a reservoir 13 acts upon the control device 21 and, when air pressure drops below a predetermined cut-off pressure. The compressor can be rendered operative by means of the sensor 20 only when the pressure controller 15 has also responded. <IMAGE>

Description

SPECIFICATION Improvements in or Relating to Compressed-Air Systems of Vehicles The present invention relates to compressed-air systems of vehicles.

One form of compressed-air system of vehicles, particularly a compressed-air brake system, comprises an air compressor for feeding a compressedair reservoir and a device for controlling the delivery of the air compressor. In one compressed-air brake system of this kind (as disclosed in German Offenlegungsschrift 2 911 085) a clutch has an associated device to which compressed air from the compressor can be admitted for the purpose of disengaging the clutch when a maximum operating pressure is reached.

According to the present invention there is provided a compressed-air system of vehicles, comprising an air compressor for feeding a compressed-air reservoir and a device controlling the delivery of the volumetric output of the air compressor, in which the volumetric output ofthe air compressor is switchable on and off in dependence upon overrun and/or braking operation of the vehicle.

A system embodying the present invention can provide intermittent generation of compressed air during operation ofthe vehicle in a very simple manner and in an inexpensive manner.

Compressed air can be delivered when, for example, the vehicle is travelling downhill or is travelling under braking conditions, that is to say, during a state in which energy from overrun operation is available without cost and does not have to be derived from, for example, the energy produced by the drive engine of the vehicle.

Furthermore, it is advantageous that a system embodying the present invention can also be used in systems whose pressure level has to be controlled by regulation by pressure regulator, governor or by so-called dead space regulation. So-called dead space regulation is regulation of the output of the compressor by adjusting the dead space of the compressor, e.g. by connecting the dead space within the compressor proper to a further chamber of relatively large size so that air simply flows into and out of this chamber and no air is delivered at the pump outlet.

Preferably the system includes at least one sensor which detects and responds to overrun and/or braking operation of the vehicle, and an electronic control device upon which the sensor acts and which is associated with the device controlling the volumetric output and switches on the latter when overrun operation or braking operation is detected and switches it off upon or after termination of overrun operation or braking operation.

Preferably the control device has a time delay ele ment by which the duration of operation of the volumetric output control initiated by means of the control device is prolonged beyond the duration of the overrun operation or braking operation. This can contribute to a reduction in wear on the clutch.

Preferably a pressure monitor is disposed in a pressure line leading to the reservoir and also acts on the control device and enables the volumetric output control to be put into operation by way of the control device when air pressure drops below a predetermined cut-off pressure and to be rendered inoperative when the cut-off pressure is reached. By the combined actions of the sensor and the pressure monitor the volumetric output control can be put into operation by means of the sensor during overrun and/or braking operation only when, as a result of the air pressure having dropped below the cut-off pressure, the pressure monitor applies to the control device a signal for putting the volumetric output control into operation.

The invention will be further described by way of example with reference to the accompanying drawing which is a diagrammatic side elevation of parts of a compressed-air brake system of a vehicle according to one embodiment of the present invention.

A compressed-air brake system 10, shown in the drawing, of a vehicle has an air compressor 1 1 which, by way of a pressure line 12, feeds a compressed-air reservoir 13 to which elements (not further illustrated) of the compressed-air brake system 10 of the vehicle are connected by way of an operating line 14.

A pressure monitor 15 is incorporated in the pressure line 12.

The aircompressor 11 is driven bythe drive engine 16 of the vehicle, The drive is effected by means of a secondary transmission 17 which is operatively connected to the vehicle gear box 18 connected to the output of the drive engine 16. An engageable and disengageable clutch 19 (indicated only diagrammatically) is included in this secondary transmission 17 to the air compressor 11. This clutch can provide socalled intermittent regulation.

Other suitable types of regulation are regulation by pressure regulator, regulation by governor, or socalle dead space regulation. When any such other type of regulation is used, it is necessary for the air compressor 11 to be driven directly by the drive engine 16 without a clutch.

In the case of intermittent regulation, the clutch 19 is engageable and disengageable in dependence upon overrun operation and/or braking operation of the vehicle. For this purpose, the compressed-air brake system 10 has at least one sensor 20 which is also illustrated only diagrammatically and which is constructed such that it can detect overrun and/or braking operation of the vehicle and responds upon commencement of this operation and also upon termination of the operation, possibly also with a predetermined time delay.

Furthermore, a preferably electronic control device 21 (only indicated diagrammatically) is provided and is associated with the clutch 19 and is connected thereto by way of a control line 22. On the one hand, the pressure controller 15 is connected to the control device 21 by way of a control line 23 and, on the other hand, the sensor 20 is connected to the control device 21 by way of a control line 24. When overrun operation or braking operation is detected, the sensor 20 can act upon the control device 21 by way of the control line 24, whereupon the clutch is actuated by the control device 21 byway ofthe control line 22 and is engaged.Termination of overrun operation or brak ing operation is also detected by the sensor 20 which transmits a corresponding signal by way of the control line 24 to the control device 21 which then in turn causes disengagement of the clutch 19 by way of the control line 22. The clutch can be disengaged substantially simultaneously with the detected termination ofthe overrun operation or braking operation or, alternatively, a, for example, adjustable period of time thereafter. The latter arrangement can substantially reduce or minimize wear on the clutch 19.

The sensor 20 responds to thrust reversal which arises upon transition to overrun operation and/or braking operation in the region ofthe drive engine 16.

In the illustrated embodiment, the sensor 20 is disposed at the output of the gear box 18 of the drive engine 16, namely where a cardan shaft 25 is con nected. The sensor 20 thereby responds to the chang- ing pressure on the flanks of the gear wheels of the vehicle gear box 18 caused by slack during overrun operation or braking operation.

The control device 21 has a, for example, adjustable time delay device 26 (indicated only diagrammatically) by which the period of engagement of the clutch 19, engaged by means of the control device 21 by way ofthe control line 22, is prolonged beyond the duration of overrun operation or braking operation.

The pressure monitor 15 mounted in the pressure line 12 operates during normal operation and also during overrun operation and braking operation. The pressure monitor 15 responds as soon as an adjustable cut-offpressure within the pressure line 12 drops by a predetermined amount. The control device 21 is then acted upon by way of the control line 23 and then, irrespective of whether normal operation or overrun operation or braking operation prevails, engages the clutch 19 by way of the control line 22, so that the air compressor 11 is driven and is operative for the purpose of generating compressed air up to the level of the cut-off pressure.The signals coming from the pressure monitor 15 on the one hand, and from the sensor 20 on the other hand, can be processed or combined in the control device 21 such that, when overrun operation and/or braking operation has been detected by the sensor 20, the clutch is engageable by the control device 21 by way of the control line 22 only when the pressure monitor 15 has also responded and has applied a corresponding signal to the control device 21 by way of the control line 23. Namely, it is only then that there is any point in using the energy, available virtually without cost as a result of thrust reversal during overrun operation and/or braking operation, for driving the air compressor 11 which, of course, basically only has to be switched on when the pressure in the compressed-air reservoir 13 and in the pressure line 12 is lower than the desired pressure.

In the other kinds of regulation for observing the pressure level, such as pressure regulator regulation, governor regulation or so-called dead space regulation, corresponding regulating elements respondng to overrun operation /or braking operation control between the air flow delivery is on-load or no-load, the air flow being delivered into the atmosphere in a pressure-less manner during no-load in the case of regulation by a pressure regulator, while the air compressor does not deliver an air flow during governor regulation and dead space regulation. The inlet or outlet valves of the air compressor are influenced in the case of governor regulation, and, in the case of so-called dead space regulation, an additional volume or space is connected to, or isolated from, the working chamber of the air compressor.

In another embodiment (not illustrated),the sensor 20 is an instantaneous direction sensor and is associated with the cardan shaft 25 ofthe drive engine 16. In this design, the sensor responds when the direction of torque in the gear train changes.

Alternatively, the sensor can be a sensor ofthe kind which responds to changing pressure conditions in the region of the fuel supply of the drive engine 16, such as changing pressure conditions in the air intake pipe of the carburettor.

Alternatively, ifthe sensor is onlyto respond during braking operation, it can be, for example, an electrical switch which is subjected directly or alternatively, indirectly to the actuation of the pedal of the vehicle brake.

Claims

1. A compressed-air system of vehicles, particularly a compressed-air brake system, comprising an air compressor for feeding a compressed-air reservoir and a device controlling the delivery of the volumetric output of the air compressor, in which the volumetric output ofthe air compressor is switchable on and off in dependence upon overrun and/or braking operation of the vehicle.

2. A compressed-air system as claimed in claim 1, including at least one sensor which detects and responds to overrun and/or braking operation of the vehicle, and an electronic control device which is acted upon by the sensor and is associated with the device controlling the volumetric output and switches on the latter when overrun operation or braking operation is detected and switches it off upon or after termination of overrun operation or braking operation.

3. A compressed-air system as claimed in claim 2, in which the at least one sensor responds to thrust reversal upon transition to overrun operation and/or braking operation.

4. A compressed-air system as claimed in claim 2 or 3, in which the at least one sensor is disposed on the gear box of the vehicle drive engine.

5. Acompressed-airsystem as claimed in claim 2, 3 or4, in which the at least one sensor responds to the pressure, varying during overrun operation or braking operation, on the flanks of gear box gear wheels.

6. A compressed-air system as claimed in claim 2 or 3, in which the at least one sensor is an instantaneous direction sensor and is associated with an output cardan shaft of the drive engine.

7. A compressed-air system as claimed in any of claims 2 to 6, in which the control device has an adjustable time delay element by which the duration of operation of the volumetric output control initiated by means of the control device is prolonged beyond the duration of the overrun operation or braking operation.

8. A compressed-air system as claimed in any of claims 2to7, in which a pressure monitor is disposed in a pressure line leading to the reservoir and also acts on the control device and enables the volumetric output control to be put into operation by way of the control device when air pressure drops below a predetermined cut-off pressure and to be rendered inoperative when the cut-off pressure is reached.

9. A compressed-air system as claimed in any of claims 2 to 8, in which the volumetric output control can be put into operation by means of the sensor during overrun operation and/or braking operation only when, as a result of the air pressure having dropped below the cut-off pressure, the pressure monitor applies to the control device a signal for putting the volumetric output control into operation.

10. Acompressed-airsystem as claimed in any of claims 1 to 9, in which the volumetric output control is achieved by means of an engageable and disengageable clutch which is adapted to put the air compressor into or out of operation.

11. A compressed-air system as claimed in any of claims 1 to 9, in which thevolumetric output control is achieved by means of a pressure regulator which conducts the volumetric output into the compressed-air system or into the atmosphere.

12. Acompressed-airsystem as claimed in any of claims 1 to 9, in which the volumetric output control is achieved by means of a governor which acts upon the valves of the air compressor to put the volumetric output into operation or to cut it off.

13. A compressed-air system as claimed in any of claims 1 to 9, in which the volumetric output control is achieved by an actuating valve which influences the dead space of the air compressor and which acts upon the delivery by the air compressorto renderthe volumetric flow operative or inoperative.

14. A compressed-air system of vehicles, constructed and arranged and adapted to operate substantially as hereinbefore particularly described with reference to and as illustrated in the accompanying drawing.