Air Preparation Device of a Vehicle

Abstract

An air preparation device having an electronic control unit for supplying at least one load circuit of a vehicle with dried system air, includes an air dryer unit for drying compressed air produced by an pneumatically switchable compressor. The air dryer unit supplies the at least one load circuit with dried compressed air via at least one overflow valve. An electromagnetic regeneration valve is provided which is connected to the control unit and returns dried compressed air along a regeneration path through the air dryer unit in order to regenerate the air dryer unit. An electromagnetic compressor control valve is provided which is connected to the control unit, for switching the pneumatically switchable compressor on and off via a pneumatic switching port, on the basis of a system pressure measurement value determined by at least one pressure sensor and supplied to the electronic control unit as an input signal. For redundant pneumatic compressor activation, a pneumatically pilot-controlled further compressor control valve is provided, to which the system pressure or a pressure proportional thereto is applied at a control inlet in order to switch on the compressor by activation of the pneumatic switching port after the system pressure has dropped below a lower limit value.

Claims

1-11. (canceled)

12. An air preparation device for supplying at least one load circuit of a vehicle with dried system air, comprising: an electronic control unit; an air dryer unit for drying compressed air generated by a pneumatically switchable compressor, which air dryer unit supplies the at least one load circuit with dried compressed air; a compressor control valve which is connected to the control unit and activated electrically for switching the pneumatically switchable compressor on and off via a pneumatic switching port on the basis of a system pressure measurement value determined by at least one pressure sensor and supplied to the electronic control unit as an input signal; and a pneumatically pilot-controlled further compressor control valve for redundant pneumatic compressor activation, to which the system pressure or a pressure proportional thereto is applied at a control input in order to switch on the compressor by activation of the pneumatic switching port after the system pressure has dropped below a lower limiting value.

13. The air preparation device as claimed in claim 12, wherein in an implementation of an inverse circuit, the compressor is switched on when its pneumatic switching port is vented, and the compressor is switched off when pressure is applied to its pneumatic switching port.

14. The air preparation device as claimed in claim 12, wherein the further compressor control valve is a pneumatically pilot-controlled 2/2-way valve of NO design, which is in a blocking position as long as the system pressure has not reached a lower threshold value.

15. The air preparation device as claimed in claim 12, wherein the further compressor control valve for switching the compressor on connects the pneumatic switching port for the compressor to a bleed port.

16. The air preparation device as claimed claim 15, wherein the further compressor control valve for switching the compressor off blocks the pneumatic switching port for the compressor with respect to the bleed port.

17. The air preparation device as claimed in claim 12, wherein the switching pressure of the further compressor control valve lies below the switching pressure controlled electrically via the control unit for switching on the compressor via the electromagnetic compressor control valve, so that the electronic control is automatically given priority over the redundant pneumatic control.

18. The air preparation device as claimed in claim 12, further comprising: an electromagnetic regeneration valve which is connected to the control unit and returns dried compressed air along a regeneration path through the air dryer unit in order to regenerate the air dryer unit.

19. The air preparation device as claimed in claim 18, wherein the regeneration valve is an electromagnetic multi-way valve which is controlled in accordance with the control unit in order to change the air preparation unit over from a delivery operation to a regeneration operation.

20. The air preparation device as claimed in claim 19, further comprising: a bleed valve arranged in the regeneration path that connects a connecting line on the input side of the compressor to a bleed port if the air preparation device is in regeneration operation, wherein the bleed valve is pilot-controlled pneumatically via a connection to the pneumatic switching port of the compressor.

21. The air preparation device as claimed in claim 19, further comprising: a bleed valve arranged in the regeneration path that connects a connecting line on the input side of the compressor to a vent port if the air preparation device is in regeneration operation, wherein the bleed valve is pilot-controlled pneumatically via a connection on a working-port side to the electromagnetic regeneration valve.

22. A utility vehicle, comprising: an air preparation device as claimed in claim 12; and at least one pneumatic load circuit, to which compressed air is supplied via the air preparation device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG. 1 shows a pneumatic switching diagram for an electronic air preparation device in a first embodiment, and

[0019] FIG. 2 shows a pneumatic switching diagram for an electronic air preparation device in a second embodiment.

DETAILED DESCRIPTION OF THE DRAWINGS

[0020] According to FIG. 1, an electronic air preparation device comprises an air dryer unit 1 for drying compressed air generated by a pneumatically switchable compressor 2. The compressed air generated by the compressor 2 is fed to the input side of the electronic air preparation device via a compressor port 3. In addition, there exists a parallel external filling port 4 which, in the event of maintenance, can have compressed air generated in stationary manner applied, so that in this case the compressor 2 does not have to be operated.

[0021] The compressed air dried by the air dryer unit 1 is supplied via a check valve 5 to multiple load circuits as system pressure. In this exemplary embodiment, a service brake for the front axle of a utility vehicle, which can be connected via the load circuit port 6, a service brake for the rear axle of a utility vehicle, which can be connected via a load circuit port 7, a service brake for a trailer of the utility vehicle, which can be connected via a load circuit port 8, and a transmission port 9, an air spring port 10, a pneumatic auxiliary device port 11 and a parking brake port 12 count as load circuits.

[0022] The aforementioned ports for load circuits are secured via various respectively associated overflow valves 13a to 13f.

[0023] Besides the previously described ports for the load circuits, the electronic air preparation device also has a pneumatic switching port 14 for switching the compressor 2 on and off via its pneumatic switching input 15. The pneumatic switching port 14 is activated via an electromagnetic compressor control valve 16, which is activated by an electronic control unit 17 to switch the compressor 2 on and off. In addition, the electronic control unit 17 also serves to activate an electromagnetic regeneration valve 18 connected thereto, which returns dried compressed air along a regeneration path through the air dryer unit 1 to regenerate the air dryer unit 1.

[0024] To generate dried compressed air along a delivery path, the compressed air generated by the compressor 2 reaches the air dryer unit 1 via the compressor port 3. The air dryer unit 1 contains a drying agent, which extracts the moisture from the compressed air and introduces the dried compressed air via the check valve 5 into a system pressure line 19, from which the various load circuits are supplied with dried compressed air. Some of the load circuits are in this case pressurized via a high-pressure changeover valve.

[0025] If the compressor 2 is switched off via the pneumatic switching port 14 after reaching an upper pressure threshold value, then, in accordance with the electronic control unit 17, regeneration of the drying agent located in the air dryer unit 1 can be carried out. For this purpose, the regeneration valve 18 is activated, which is fed with dried compressed air from the pressure line 19′ carrying system pressure and, in the switched state, leads said dried air through the air dryer unit 1 counter to the conveying direction via a check valve 20, in order to dehumidify the drying agent again. The compressed air emerging from the dryer unit 1 along the further regeneration path is then led away to the atmosphere via a switched-over bleed valve 21 and a bleed port 27.

[0026] The compressor control valve 16 is assigned multiple pressure sensors 22a-22c, wherein the electronic control unit 17 measures the system pressure value respectively present after the overflow valves 13a, 13b and 13c and, in the delivery phase, when an upper threshold value is reached, activates the compressor control valve 16 to switch off the compressor 2 via the pneumatic switching port 14. For this purpose, the pneumatic switching port 14 in the changed-over position of the compressor control valve 16 has the system pressure taken from the pressure line 19′ applied thereto. To switch off the compressor 2, the pneumatic switching port 14 is vented.

[0027] A pneumatic compressor activation that is redundant relative to this electronic compressor activation also operates a pneumatically pilot-controlled compressor control valve 23. A control input 24 of the compressor control valve 23 is connected to the pressure line 19′ carrying system pressure so that, after the system pressure has dropped below a lower limiting value, the compressor 2 can be switched on by activating the pneumatic switching port 14. For this purpose, the compressor control valve 23 in the switching position illustrated connects the pneumatic switching port 14 for the compressor 2 to the atmosphere, therefore vents the same.

[0028] In this exemplary embodiment, the compressor control valve 23 is designed as a pneumatically pilot-controlled 2/2-way valve of NO design and is in the blocking position as long as the system pressure does not reach a lower threshold value. In this way, switching on the compressor 2 when there is still adequate system pressure is avoided. The switching pressure of the compressor control valve 23 lies below the switching pressure of the electromagnetic compressor control valve 16 controlled electrically via the control unit 17, so that the electronic control is automatically given priority over the redundant pneumatic control. Thus, the redundant pneumatic control functions only as a type of emergency switching-on of the compressor 2 if the sensors possibly fail according to the fault scenario outlined at the beginning.

[0029] The aforementioned bleed valve 21 arranged in the regeneration path of the air preparation device is activated via its control input 26 by a connection to the pneumatic switching port 14 of the compressor 2 by the pressure present here. If pressure is present on the pneumatic switching port 14 in order to switch off the compressor 2, then the bleed valve 21 is changed to the open switching position so that, in the regeneration phase, the moisture-laden compressed air leaving the air dryer unit 1 is led away to the atmosphere via a bleed port 27.

[0030] FIG. 2 illustrates an energy-saving pneumatic switching arrangement as distinct from the above-described exemplary embodiment, which, apart from the arrangement and wiring of the bleed valve 21′ arranged in the regeneration path, is identical to the previously described exemplary embodiment, to which complete reference is made to this extent.

[0031] The bleed valve 21′ here also connects a connecting line on the input side of the compressor 2 to the bleed port 27′ if the air preparation device is in regeneration operation. The control port 26′ of the bleed valve 21′ is, however, connected on the working-port side to the electromagnetic regeneration valve 18. Therefore, the bleed valve 21′ is actuated only when the regeneration phase has been initiated, so that compressed air is saved as opposed to the above switching variant.

[0032] The solution according to the invention is not restricted to an application in the two exemplary embodiments described above. Instead, modifications thereof which are also covered by the scope of protection of the following claims are also conceivable. Thus, for example, it is also possible that only a single load circuit of a vehicle or load circuits other than those described can be supplied with dried compressed air by the air preparation device according to the invention.

LIST OF DESIGNATIONS

[0033] 1 Air dryer unit [0034] 2 Compressor [0035] 3 Compressor port [0036] 4 External filling port [0037] 5 Check valve [0038] 6 Service brake port (front axle) [0039] 7 Service brake port (rear axle) [0040] 8 Service brake port—trailer [0041] 9 Transmission port [0042] 10 Air spring port [0043] 11 Auxiliary port [0044] 12 Parking brake port [0045] 13 Overflow valve [0046] 14 Switching port for compressor [0047] 15 Compressor control port [0048] 16 Compressor control valve [0049] 17 Electronic control unit [0050] 18 Regeneration valve [0051] 19 Pressure line carrying system pressure [0052] 20 Check valve [0053] 21 Bleed valve [0054] 22 Pressure sensor [0055] 23 Further compressor control valve [0056] 24 Control input [0057] 25 Bleed port [0058] 26 Control input [0059] 27 Bleed port