Compressed air generation device and method for operating same

Abstract

The invention relates to a compressed air generation device (2) with an open-loop and closed-loop control unit (28), with an electric motor (24) which can be open-loop and closed-loop controlled by the open-loop and closed-loop control unit (28), with at least one air compressor (16; 18) which can be driven by the electric motor (24), with an air inlet (8) via which ambient air (L) can be sucked into the at least one air compressor, with at least one air cooler (20; 22) which is connected to the outlet of the at least one air compressor, with at least one air dryer (40) which is connected to the outlet of the at least one air cooler, with a coolant inlet opening (12), via which a liquid coolant can be fed to the at least one air cooler and to further components of the compressed air generation device, with a coolant outlet opening (14), via which heated coolant can be discharged from the compressed air generation device (2), and with at least one temperature sensor (73, 73', 73'') which is connected to the open-loop and closed-loop control unit (28) via a data or sensor line (59). In order to determine that regeneration compressed air volume which has to be conducted through a drying agent (41) of the air dryer (40) for regeneration purposes, it is provided that the temperature sensor for measuring the coolant temperature is arranged upstream of the coolant inlet or downstream of the coolant outlet of that air cooler (22) which is arranged upstream of the air dryer as the last air cooler in the flow direction of the compressed air. The invention also relates to a method for operating such a compressed air generation device.

Description

[0001] Compressed air generating device and method for operating the same

[0002] The invention relates to a compressed air generation device, with a control and regulating device, with an electric motor that can be controlled and regulated by the control and regulating device, with at least one air compressor that can be driven by the electric motor, with an air inlet through which ambient air can be sucked into the at least one air compressor, with at least one air cooler that is connected to the outlet of the at least one air compressor, with at least one air dryer that is connected to the outlet of the at least one air cooler, with a coolant inlet opening through which a liquid coolant can be supplied to the at least one air cooler and other components of the compressed air generation device, with a coolant outlet opening through which heated coolant can be discharged from the compressed air generation device, and with at least one temperature sensor that is connected to the control and regulating device via a data or sensor line.Furthermore, the invention relates to a method for operating such a compressed air generating device.

[0003] Electrically driven compressors for generating compressed air in vehicles are already known in various embodiments and are described, for example, in DE 10 2018 139 058 A1, DE 10 2013 003 513 A1 and EP 3 516 218 B1. EP 3 331 738 B1 discloses a compressed air generating device for a vehicle with a piston compressor and two compression stages. The cylinder chambers of the two compression stages are connected to one another by a connecting line through which the compressed air generated in the first compression stage can be fed to the second compression stage. During operation of the piston compressor, the ambient air pressure in the first compression stage is increased with the aid of a backpressure building up in the subsequent connecting line. An intercooler is arranged in the connecting line between the two compression stages and serves to cool the air heated during compression in the first compression stage.This lowers the compressed air pressure in the connecting line. The intercooler thus increases the efficiency of the second compression stage. Furthermore, additional devices for processing the used air, such as additional cooling devices or air drying devices, can be arranged before or after the first compression stage. One disadvantage is that the described compressor is designed as a reciprocating piston compressor, which disadvantageously requires a lubricant. Furthermore, the design of the cooling system is not further described.

[0004] Furthermore, DE 10 2004 051 435 B3 discloses a system for generating dry compressed air, which comprises a cooled compressor for drawing in and compressing ambient air. A cooler is arranged downstream of the compressor in the direction of compressed air flow, which serves to cool the generated compressed air. The cooling effect of the cooler is achieved by means of a fan and water droplets directed onto the surface of the cooler, where they evaporate and thereby remove heat from the cooler and indirectly from the compressed air. An air dryer is arranged downstream of the cooler. This dryer contains a desiccant that removes air humidity from the compressed air, thereby lowering the dew point of this compressed air. The compressed air dried in this way has a humidity of less than 35% at the outlet of the air dryer, which should be sufficient to protect devices subsequently supplied with this compressed air from corrosion or freezing due to the formation of water ice.

[0005] Furthermore, DE 44 45 972 02 discloses a compressor system for generating dry compressed air. An air-cooled radiator serves to cool the compressed air generated by a compressor. A water separator is arranged downstream of the radiator, which removes water droplets from the compressed air that form through condensation during cooling. Since the compressed air is not yet sufficiently dry to prevent freezing at low temperatures when used in pressure medium consumers, an air dryer is arranged downstream of the water separator, in which the compressed air is further dried.

[0006] Furthermore, from the applicant's unpublished DE 10 2021 121 424.6, a compressed air generation device is known which has an electric motor that can drive two air compressors arranged in series. During operation of the compressed air generation device, ambient air is sucked in and compressed by the first air compressor. From there, the pre-compressed compressed air is fed to the second air compressor via a check valve, an intercooler, and a switching valve. In the second air compressor, the pre-compressed compressed air is further compressed and then passed on to compressed air consumers via an aftercooler or another switching valve. The intercooler and the aftercooler are cooled by a liquid coolant and serve to cool the compressed air generated by the air compressors.The liquid coolant originates, for example, from a vehicle's cooling circuit and, in the compressed air generation device, first supplies a cooling device of the electric motor, then the intercooler, and then a cooling device of the first air compressor. From there, the coolant flows to the aftercooler and then to a cooling device of the second air compressor before being returned to the vehicle's cooling circuit. An air dryer is neither shown nor described in this compressed air generation device.

[0007] Furthermore, US 2010 / 0 303 658 A1 discloses a water-cooled, oil-filled two-stage air compressor, which has a water-cooled intercooler arranged between a first air compressor and a second air compressor with respect to the air flow. The air compressed by the first air compressor is cooled by the intercooler, and the air compressed by the second air compressor is cooled by an aftercooler, whose cooling water inlet is hydraulically connected to the cooling water outlet of the intercooler.

[0008] Finally, DE 11 2015 006 955 T5 discloses a compressed air supply system for locomotives and a method for operating the same. The air drawn in and compressed by a compressor is cooled in an air cooler and then fed to a first compressed air reservoir. From this first compressed air reservoir, the compressed air flows via a check valve closing in the return flow direction to a pre-filter, which has a drainage valve. After liquid and aerosolized water has been separated from the compressed air in the pre-filter, the compressed air flows to an air dryer. A temperature sensor located at the air flow inlet of the air dryer or in its immediate vicinity is connected to a control unit via a sensor line. The temperature sensor can measure the actual temperature of the compressed air flowing into the air dryer and provide this measured value to the control unit.Based on the saturation partial pressure of water vapor at the measured actual temperature of the compressed air, the control unit can calculate a suitable purge cycle time for the drain valve and control its operation to remove the water accumulated in the pre-filter.

[0009] The drying agent in the air dryer of such compressed air generation devices must also be repeatedly freed of the moisture that has accumulated there, because if the drying agent's moisture absorption capacity is saturated, it is no longer able to function properly. To remove this moisture from the air dryer, a known method is to recirculate the dry compressed air generated by the compressed air generation device and stored in a pressure fluid reservoir back through the air dryer in a so-called regeneration process. The dry compressed air absorbs moisture from the air dryer's drying agent and transports it out into the environment surrounding the compressed air generation device.Since these regeneration processes consume dried compressed air, which in a motor vehicle is actually required for operating brake actuators and / or air spring bellows, for example, additional compressor operating times are necessary to ensure sufficient compressed air is available for the regeneration processes. However, this entails additional energy consumption, which increases the operating costs of a motor vehicle, for example, and ultimately releases environmentally harmful CO2 into the atmosphere through the generation of electrical energy for the electric motor.

[0010] Against this background, the invention is based on the object of presenting a compressed air generation device comprising a compressor, a liquid cooling system, and an air dryer, whose consumption of dried compressed air for the regeneration of a drying agent of the air dryer is reduced compared to conventional compressed air generation devices of the same type. Furthermore, the regeneration compressed air volume expected to be required for the respective regeneration of the drying agent should be determinable. Furthermore, a method for operating such a compressed air generation device is to be presented.

[0011] This object is achieved with a compressed air generating device having the features of claim 1. An independent method claim defines a method for operating such a compressed air generating device. Advantageous embodiments and further developments are recited in the respective dependent claims.

[0012] Accordingly, the invention initially relates to a compressed air generation device with a control and regulating device, with an electric motor that can be controlled and regulated by the control and regulating device, with at least one air compressor that can be driven by the electric motor, with an air inlet through which ambient air can be sucked into the at least one air compressor, with at least one air cooler that is connected to the outlet of the at least one air compressor, with at least one air dryer that is connected to the outlet of the at least one air cooler, with a coolant inlet opening through which a liquid coolant can be supplied to the at least one air cooler and other components of the compressed air generation device, with a coolant outlet opening through which heated coolant can be discharged from the compressed air generation device, and with at least one temperature sensor,which is connected to the control and regulation device via a data or sensor cable.

[0013] To achieve the object relating to the device, this compressed air generating device is further provided with the temperature sensor for measuring the coolant temperature being arranged upstream of the coolant inlet or downstream of the coolant outlet of the air cooler which is arranged as the last air cooler upstream of the air dryer in the direction of flow of the compressed air.

[0014] The invention is based on the first finding that the compressed air, after leaving the last air cooler and before reaching the air dryer, carries a certain amount of water as humidity, depending on its temperature. Therefore, if the temperature of the compressed air after leaving the last air cooler before reaching the air dryer is known, it is possible to calculate how much water the compressed air carries as humidity. If the volume flow of compressed air during the previous compressed air generation operation and the absorption capacity of the drying agent in the air dryer are also known, it is possible to calculate how large a regeneration compressed air volume is required to dry the drying agent with dry regeneration compressed air during a break in compressed air generation in a regeneration operation.

[0015] For indirect measurement of the compressed air temperature, the invention provides for the temperature sensor for measuring the coolant temperature to be arranged upstream of the coolant inlet opening of the compressed air generation device. This allows the measured values ​​of a temperature sensor located outside the installation space of the compressed air generation device to be used. If the liquid cooling system of such a compressed air generation device uses a vehicle cooling system already present on the vehicle with a temperature sensor, no additional temperature sensor needs to be arranged for the compressed air generation device, saving space and costs.

[0016] However, if the temperature sensor mentioned is integrated in the installation space of the compressed air generating device, it can be provided that it is arranged directly in front of the coolant inlet of the air cooler which is arranged as the last air cooler in front of the air dryer in the flow direction of the compressed air.

[0017] Alternatively or additionally, the temperature sensor for measuring the coolant temperature can be arranged downstream of the coolant outlet of the air cooler, which is the last air cooler in the compressed air flow direction, upstream of the air dryer. By comparing the coolant temperatures upstream and downstream of this last air cooler, it is possible to determine how much heat is extracted from the compressed air flow at this air cooler. This information can be used to regulate the pumping capacity of a coolant pump.

[0018] A second finding is that when the compressed air is particularly cold upon entering the air dryer, it carries comparatively little water in the form of humidity. Therefore, if the compressed air can be cooled as much as possible before reaching the air dryer, relatively little water will be introduced into the air dryer's desiccant. As a direct consequence, during a pause in compressed air generation during regeneration, a comparatively small volume of regeneration compressed air is required to dry the air dryer's desiccant.

[0019] In order to utilize this knowledge, the invention also provides that the air cooler which is arranged as the last air cooler in front of the air dryer in the flow direction of the compressed air is arranged in such a way that the coolant can flow through it first, as seen in the flow direction of the coolant.

[0020] Knowledge of the compressed air temperature after leaving the air cooler, which is the last one located in the compressed air stream before the air dryer, is of great importance. As explained above, the indirect determination of the compressed air temperature at this point is simpler and more cost-effective than measuring the compressed air temperature in the compressed air stream between the aforementioned air cooler and the air dryer.

[0021] According to a further specialization of the compressed air generation device, it can comprise the following: an electric motor, two air compressors that can be driven by the electric motor and operate one after the other, an air inlet through which ambient air can be sucked in by means of the first air compressor, two air coolers for cooling the compressed air, which are designed and arranged as intercoolers and aftercoolers, respectively, wherein the inlet of the intercooler is pneumatically connected to the outlet of the first air compressor, wherein the outlet of the intercooler is pneumatically connected to the inlet of the second air compressor, wherein the outlet of the second air compressor is pneumatically connected to the inlet of the aftercooler, and wherein the outlet of the aftercooler is pneumatically connected to the inlet of an air dryer, as well as a coolant inlet opening through which a liquid coolant can be supplied to the intercooler and the aftercooler,and a coolant outlet opening through which heated coolant can be discharged. In such a compressed air generating device, the invention provides that the aftercooler is arranged such that the coolant flows through it first, as seen in the flow direction of the coolant, and that at least one temperature sensor is provided, which is arranged upstream or downstream of the aftercooler to measure the temperature of the coolant.

[0022] In this compressed air generation device, the two aforementioned findings were incorporated into the design instructions. First, the placement of a temperature sensor for measuring the coolant temperature before or after the air cooler, in this case the aftercooler, which is positioned last in the compressed air flow before the air dryer. Furthermore, this compressed air generation device is designed so that the liquid coolant reaches the aftercooler first and, as far as the cooling system allows, cools the compressed air as much as possible before it reaches the air dryer.

[0023] In a departure from previously known designs, the still relatively cold liquid coolant first flows through an aftercooler, which is located directly upstream of the air dryer in the direction of compressed air flow. This cools the compressed air as much as possible, so that some of the humidity contained in the compressed air precipitates in the form of small water droplets before it reaches the air dryer. This water is then removed from the compressed air, for example, by a water separator in the aftercooler before it reaches the air dryer.A small amount of condensed water droplets can be carried along by the relatively cooled compressed air through a short compressed air line to the air dryer, where these water droplets collect in the inlet collection area and are removed during the next regeneration process with the regeneration compressed air flowing out of the air dryer. If a water separator is not present, all water droplets that condense upstream of the air dryer are carried along to the inlet collection area of ​​the air dryer. Because a comparatively large amount of moisture has already been removed from the compressed air before it reaches the air dryer's desiccant, the air dryer is subsequently required to a lesser extent to dry the compressed air.As a result, a regeneration process on the air dryer, which consumes dried compressed air, needs to be carried out less frequently, or a smaller amount of compressed air is required per regeneration process, which conserves the supply of stored dry compressed air.

[0024] According to a further development of the described compressed air generating device, it is provided that the electric motor, an inverter influencing the operation of the electric motor, the two air compressors, the intercooler, the aftercooler, the air dryer, a multi-circuit protection valve which pneumatically connects the outlet of the air dryer to at least one external compressed air reservoir and external compressed air consumers, as well as a silencer are arranged in interaction but separately with respect to one another.

[0025] Alternatively, it can be provided that the electric motor, an inverter influencing the operation of the electric motor, the two air compressors, the intercooler, the aftercooler, the air dryer, a multi-circuit protection valve which pneumatically connects the outlet of the air dryer to at least one external compressed air reservoir and external compressed air consumers, as well as a silencer are arranged in or on a common housing.

[0026] In both described design variants, the aforementioned device components are suitably connected to one another via the aforementioned electrical, pneumatic, and hydraulic connecting lines, which may be arranged in the housing. This makes the compressed air generation device extremely compact, easy to assemble during manufacture, and easy to attach to a motor vehicle, for example, a commercial vehicle.

[0027] In this context, it can further be provided that a control and regulating device is additionally arranged separately in or on the housing of the compressed air generation device, that the control and regulating device is connected via a first control line to the inverter for controlling the electric motor, that the control and regulating device is connected via a second control line to a 3 / 2-way solenoid valve which serves to open or close a regeneration line which at least indirectly pneumatically connects the compressed air reservoir and the air dryer, and that the control and regulating device is connected via a sensor line to the multi-circuit protection valve.

[0028] By additionally integrating the control and regulation unit, the 3 / 2-way solenoid valve, as well as the associated control lines and regeneration line into the housing of the compressed air generation device, the device contains additional components associated with the compressed air generation device, making the overall system even easier to handle and connect to the vehicle. Therefore, in the event of a malfunction in one of its components, such a compressed air generation device can be easily removed from a commercial vehicle as a whole and taken to a repair shop, while a new compressed air generation device can be quickly and easily installed on the vehicle. Since a compressed air generation device is a vital operational device, especially in commercial vehicles, the procedure described avoids lengthy repairs and allows the commercial vehicle to be quickly put back into operation.

[0029] To further improve the repairability of the compressed air generation device and to enable quick repairs, according to another development of the compressed air generation device, it can be provided that it is constructed from four modules, which, together with the associated pneumatic, hydraulic, and electrical lines, are arranged in or on the common housing. The electric motor, the inverter, the two air compressors, and the control and regulation unit are arranged in a compressor module. A compressed air cooling module has the intercooler and the aftercooler, and a dryer module houses the air dryer and the multi-circuit protection valve. Furthermore, a silencer module contains a silencer, which silencer contains a sound-damping material. The sound-damping material is designed such thatthat it can also absorb water droplets separated by the air dryer and, like the spray water entering the silencer, direct them to a water outlet of the silencer module. Furthermore, the silencer module is provided with at least one regeneration air outlet opening for discharging regeneration compressed air into the environment. In certain applications, the integration of this silencer module can be omitted. The compressed air generation device with the features of the invention can be designed in detail such that an outlet of the air dryer is connected via a first check valve closing towards the air dryer by means of a fifth compressed air line, that this fifth compressed air line leads via the aforementioned multi-circuit protection valve to the at least one compressed air reservoir and to compressed air consumers.that a regeneration compressed air inlet of the air dryer is connected to the outlet of a 3 / 2-way solenoid valve via a second check valve opening in the direction of the regeneration compressed air inlet, an orifice plate, and a first line branch; that the inlet of this 3 / 2-way solenoid valve is connected to the fifth compressed air line via a regeneration compressed air line; that, when the 3 / 2-way solenoid valve is actuated, dry compressed air can be supplied to the air dryer as regeneration compressed air via this 3 / 2-way solenoid valve, the first line branch, the orifice plate, and the first check valve; and that, likewise when the 3 / 2-way solenoid valve is actuated, regeneration compressed air can be supplied to the pneumatic control inlet of a 2 / 2-way switching valve, which is assigned to a regeneration air outlet of the air dryer.

[0030] A regeneration process in the air dryer is therefore initiated by the control and regulation unit and primarily controlled by the 3 / 2-way solenoid valve. The 3 / 2-way solenoid valve supplies dry regeneration compressed air to the air dryer, while simultaneously supplying a control pressure to a control pressure inlet of the pneumatic 2 / 2-way valve to open a regeneration air outlet of the air dryer. This control pressure is generated by a small portion of the regeneration compressed air that comes from the compressed air reservoir and is also supplied to the air dryer to dry the desiccant there.

[0031] Another refinement provides that the pressure-controlled 2 / 2-way switching valve is also assigned to the collection area of ​​the air dryer, whose pneumatic control input is connected to the output of the 3 / 2-way solenoid valve via a second line branch. The 2 / 2-way switching valve is designed such that it is closed when not actuated. The 2 / 2-way switching valve can also be switched from its closed position to its open position by means of regeneration compressed air supplied to the air dryer via the second line branch. When the 2 / 2-way switching valve is open, dry regeneration compressed air can be passed through the drying agent of the air dryer in a regeneration compressed air stream.After flowing through the desiccant, the regeneration compressed air can be directed into the collection area of ​​the air dryer and can entrain any condensed water that has accumulated there and remove it from the air dryer via at least one regeneration air outlet.

[0032] Furthermore, it can be provided that instead of the 3 / 2-way solenoid switching valve, two 2 / 2-way solenoid switching valves that can be controlled by the control and regulating device are present, wherein the first 2 / 2-way solenoid switching valve is arranged upstream of the orifice in the first line branch in the flow direction of regeneration compressed air, wherein the second 2 / 2-way solenoid switching valve is arranged upstream of the pressure-controlled 2 / 2-way switching valve in the second line branch, and wherein the fifth compressed air line is connected directly to the first line branch and directly to the second line branch upstream of the two 2 / 2-way solenoid switching valves in the flow direction of regeneration compressed air.

[0033] Furthermore, according to another advantageous development, the compressed air generation device has an ambient temperature sensor with which the ambient temperature can be measured. This ambient temperature sensor is also connected to the control and regulating unit via a data or sensor line. Determining and taking into account the ambient air temperature is advantageous because the moisture content of the ambient air that can be drawn in by the compressed air generation device depends on the air temperature. At a low air temperature, its water content can be lower than at a higher temperature. It must also be taken into account that the ambient air temperature influences the temperature of the compressed air reservoir and the compressed air stored therein from which a regeneration compressed air volume is drawn during regeneration operation.As a result, the ambient temperature also influences the moisture absorption capacity of the regeneration compressed air as it flows through the desiccant of the air dryer. The data or sensor cables mentioned here may be CAN bus cables.

[0034] The invention also relates to a method for operating a compressed air generating device having the features of at least one of the device claims and the above device description. According to the method, air compressed by means of the at least one air compressor is cooled in at least one air cooler. The cooled compressed air is subsequently fed to an air dryer and dried there, before being directed to compressed air consumers and / or at least one compressed air reservoir. During a regeneration operation of the compressed air generating device, in order to regenerate a drying agent arranged in the air dryer, dry compressed air is passed through the drying agent in the amount of a required regeneration compressed air volume and is then discharged into the environment.

[0035] It is provided that the regeneration compressed air volume required for the regeneration of the drying agent is calculated at least as a function of the temperature which the coolant has before and / or after flowing through the air cooler which is arranged as the last air cooler in front of the air dryer, and that the regeneration compressed air volume of dry compressed air determined in this way is then passed through the air dryer.

[0036] Since the amount of water that the compressed air carries as air humidity after passing the last air cooler to the air dryer depends on the compressed air temperature there, it may initially seem disadvantageous not to determine the regeneration compressed air volume required for regeneration operation of the compressed air generation device on the basis of a direct measurement of the temperature of the compressed air flow upstream of the air dryer.

[0037] The method presented here, however, has the advantage that no additional temperature sensor is required to obtain information about the temperature of the compressed air before reaching the air dryer and the water content in the form of humidity that this compressed air carries. As already explained above, in every motor vehicle with a liquid cooling system today, the coolant temperature after leaving its radiator is measured using a temperature sensor, and the measured values ​​are made available in the vehicle for a variety of purposes, for example via a CAN data bus. By knowing the temperature of the coolant directly after leaving the vehicle radiator or immediately before the aforementioned air cooler, the temperature of the compressed air after leaving this air cooler can be indirectly determined without the need for a separate temperature sensor.

[0038] The operation of the compressed air generation device, and in particular the supply of coolant, is then regulated to maximize the cooling effect of the last air cooler before the air dryer. This also maximizes the cooling effect of the compressed air before the air dryer, resulting in comparatively low levels of moisture that would burden the air dryer. As a result, the air dryer's desiccant needs to be regenerated less frequently or with a smaller regeneration compressed air volume.

[0039] In a further embodiment of the method, it is provided that the coolant temperature is measured in front of the coolant inlet opening of the compressed air generating device by means of a first temperature sensor, and that the regeneration compressed air volume required for drying the drying agent in the air dryer is passed through the air dryer in a controlled and / or regulated manner depending on the measured coolant temperature.

[0040] Alternatively, it can be provided that the coolant temperature is measured by means of a second temperature sensor immediately upstream of the coolant inlet of the air cooler which is arranged as the last air cooler upstream of the air dryer in the direction of flow of the compressed air, and that the regeneration compressed air volume required for drying the desiccant in the air dryer is passed through the air dryer in a controlled and / or regulated manner depending on the measured coolant temperature.

[0041] Furthermore, it can also be provided that the coolant temperature is measured by means of a third temperature sensor behind the coolant outlet of the air cooler which is arranged as the last air cooler in front of the air dryer in the direction of flow of the compressed air, and that the regeneration compressed air volume required for drying the desiccant in the air dryer is passed through the air dryer in a controlled and / or regulated manner depending on the measured coolant temperature.

[0042] A further possibility for determining an optimally sufficient regeneration compressed air volume for drying the drying agent of the air dryer provides that the temperature of an inverter provided for controlling and regulating the electric motor is measured, that the measured temperature of the inverter is used to calculate the coolant temperature in the air cooler which is arranged as the last air cooler in front of the air dryer in the direction of flow of the compressed air, and that the regeneration compressed air volume required for drying the drying agent in the air dryer is passed through the air dryer in a controlled and / or regulated manner depending on the coolant temperature thus determined.

[0043] The temperature of the inverter's electronics can be used as the temperature. This process variant eliminates the need for a temperature sensor near the coolant lines and / or the aforementioned air cooler, saving costs.

[0044] According to a further specialization of the method, the following method steps can be provided: a) Suction of ambient air by means of the first air compressor, b) Pre-compression of the sucked in ambient air in the first air compressor to a first air pressure value, c) Cooling of an intercooler with a liquid coolant, d) Cooling of the pre-compressed compressed air in the intercooler, e) Further compression of the compressed air to a second, higher pressure value by means of a second air compressor, f) Cooling of an aftercooler with the liquid coolant, wherein the aftercooler is reached hydraulically by the coolant as the first air cooler, seen in the flow direction of the coolant, g) Cooling of the compressed air further compressed in the second air compressor in the aftercooler, h) Drying of the cooled compressed air in an air dryer, i) Forwarding of the cooled and dried compressed air to compressed air consumers and / or to at least one compressed air reservoir.

[0045] These process steps make it clear that the compressed air that has left the second air compressor is cooled as it flows through the aftercooler to the extent that the freshly supplied liquid coolant allows. For this purpose, the liquid coolant is not first directed to a cooling device of the electric motor or to the intercooler in order to cool them during operation, as is the case with the compressed air generation device according to DE 10 2039 139 424.6. Instead, in the compressed air generation device presented here, the coolant is first directed to the aftercooler in order to cool this and, as a result, also the compressed air as much as possible. This makes it possible, according to the process, to cool the generated compressed air so much before it reaches the air dryer that as much moisture as possible is separated and removed from the compressed air.

[0046] In order to also cool other components of the compressed air generation device with the liquid coolant, the following further method steps are provided in addition to the method mentioned: j) passing the liquid coolant from the aftercooler to the intercooler, k) passing the liquid coolant from the intercooler to a cooling device of the electric motor, l) passing the liquid coolant from the cooling device of the electric motor to a cooling device of the second air compressor, m) passing the liquid coolant from the cooling device of the second air compressor to a cooling device of the inverter, n) passing the liquid coolant from the cooling device of the inverter to a cooling device of the first air compressor, o) passing the liquid coolant from the cooling device of the first air compressor to an external cooling device.In addition to routing the coolant, particularly first to the aftercooler, and the compressed air in the compressed air generation device, the regeneration of the air dryer's desiccant is particularly important. During this regeneration, temporarily stored dry compressed air flows through the desiccant, which has removed moisture from the supplied compressed air in previous drying processes and has now significantly reduced its drying capacity, in the opposite direction. The compressed air absorbs water from the desiccant and, laden with it, flows out of the air dryer into the environment. The frequency with which such regeneration processes must be carried out and the volume of compressed air required for these regeneration processes influence the demand for compressed air generated by the compressed air generation device during vehicle operation.Since water is already separated from the compressed air in the aftercooler during the cooling of the compressed air described above, this water reaches the inlet area of ​​the air dryer as a water film or as small droplets with the compressed air fed to the air dryer, from where it is discharged into the environment.

[0047] However, it may just as well be provided that the time interval between two regeneration processes for drying the desiccant of the air dryer is controlled and / or regulated as a function of the temperature of the coolant which the coolant has at the outlet of the external cooling device or at the inlet of the aftercooler.

[0048] Since the temperature of the coolant determines how much water has already condensed from the compressed air supplied to it at the aftercooler, a comparatively low coolant temperature results in a comparatively large amount of water being separated from the compressed air at the aftercooler, which is then discharged from there. As a result, the air dryer's desiccant is subjected to less stress, so the regeneration compressed air volume can be lower or, for example, the time interval between two regeneration processes can be longer than with a comparatively high coolant temperature.

[0049] The ambient temperature of a vehicle must also be taken into account when performing regeneration processes of the type described, because the compressed air stored in a compressed air reservoir gradually takes on the ambient temperature via the walls of the compressed air reservoir. Since the compressed air stored in this compressed air reservoir is also used to regenerate the desiccant in the air dryer, and the compressed air temperature also determines the water storage capacity of the regeneration compressed air, knowledge of the ambient temperature is important for determining the required regeneration compressed air volume.

[0050] Therefore, in the method in which previously dried and temporarily stored compressed air is passed through the air dryer as regeneration compressed air in the opposite direction for the regeneration of a drying agent arranged in the air dryer, it can be provided that the regeneration compressed air volume required for drying the drying agent is controlled and / or regulated as a function of the average ambient temperature.

[0051] This method can also provide for the time interval between two regeneration processes for drying the air dryer's desiccant to be controlled and / or regulated depending on the average ambient temperature. The average ambient temperature can be determined over a predetermined period of time.

[0052] For example, if both the ambient temperature and the coolant temperature change rapidly due to the current driving situation and / or rapidly changing ambient conditions, it can be provided that the regeneration compressed air volume required for drying the desiccant or the duration and / or frequency of the regeneration processes is controlled and regulated depending on the difference between the ambient temperature and the coolant temperature.

[0053] In the case of uncontrolled control of the regeneration of the drying agent of the air dryer, according to another development of the method for operating the compressed air generating device presented, it is provided that a maximum temperature value of the coolant to be expected during operation of the compressed air generating device is determined, that this value of the coolant temperature serves as the basis for determining a maximum regeneration compressed air volume, and that a corresponding regeneration process for the drying agent is carried out with this maximum regeneration compressed air volume.

[0054] For a better understanding of the invention, a drawing is attached to the description, the single figure of which shows a compressed air generation device incorporating the features of the invention. In this schematic drawing, pneumatic lines carrying air or compressed air are shown in solid lines. Hydraulic lines carrying a liquid coolant are shown in dashed lines, and electrical lines are shown in dotted lines.

[0055] In the exemplary embodiment illustrated here, the compressed air generating device 2 has a closed, but also openable, housing 6 in which the components of the compressed air generating device 2 are combined into modules arranged one behind the other. Thus, the compressor 4, comprising an electric motor 24 including two drive shafts 30, 32, an inverter 26, a first air compressor 16, a second air compressor 18, and a control and regulating device 28, is arranged in a compressor module 90. Behind this, in the housing 6, a compressed air cooling module 92 is arranged, which has an intercooler 20 and an aftercooler 22. These two air coolers 20, 22 serve to cool the compressed air generated by the compressor 4. For this purpose, the two air coolers 20, 22 use a liquid coolant supplied from an external cooling device 82.In the selected example, this external cooling device 82 is a cooling device of a commercial vehicle with a suitable heat exchanger (not shown here). The amount of liquid coolant passed through the coolable components of the compressed air generation device 2 per second can be adjusted by means of a controllable coolant pump, which is controllably connected to the control and regulating unit 28.

[0056] Subsequently, a dryer module 94 is provided in the housing 6, in which an air dryer 40 and, in the example shown, advantageously a multi-circuit protection valve 50 are arranged. The air dryer 40 contains a drying agent 41, with which air humidity can be removed from the compressed air fed to the air dryer 40. The drying agent 41 can release this moisture back into dry air, namely when, during a regeneration process, dry compressed air is passed through the air dryer 40 in the opposite direction. The multi-circuit protection valve 50 does not have to be a component of the dryer module 94, but its arrangement in the common housing 6 is advantageous. By means of the multi-circuit protection valve 50, it is possible to selectively release compressed air delivered by the air dryer 40 to different compressed air consumers 51, 52 and / or to a compressed air reservoir 45.It should also be mentioned that the sixth compressed air line DL6 and the seventh compressed air line DL7 leading to the compressed air consumers 51, 52 can also be connected to other compressed air reservoirs along their route. Likewise, at least one additional compressed air consumer (not shown) can be connected to the illustrated compressed air reservoir 45.

[0057] Finally, the compressed air generation device 2 has a silencer module 96, which is designed as a silencer 43 containing a sound-damping material 44. This sound-damping material 44 is capable of dampening sound emissions that arise during a regeneration process when moisture-laden compressed air is discharged from the air dryer 40. For this purpose, the silencer module 96 has a plurality of regeneration air outlet openings, of which only one regeneration air outlet opening 34 is shown, through which exhaust air AL can be discharged into the environment.In addition, the silencer module 96 or the silencer 43 has at least one water outlet opening 36 at its lowest point, through which water droplets separated from the compressed air in the air dryer 40 during normal operation and / or spray water penetrated through the regeneration air outlet opening 34 can be removed via a water separation path 80 that forms. The silencer module 96, or at least its silencer 43, can be easily replaceably mounted in or on the housing 6.

[0058] The components of the four modules 90, 92, 94, and 96 described above are connected via pneumatic, hydraulic, and electrical lines as necessary, which will be discussed separately in the description of the method for operating the compressed air generating device 2. The functionality and interaction of the components of the compressed air generating device 2 are as follows:

[0059] The operation of the compressor 4 is controlled and regulated by the aforementioned control and regulating unit 28. The control and regulating unit 28 is connected via a low-voltage line 57 to a low-voltage source (not shown in detail), to a data or sensor line 59 of an on-board data communication system, such as a CAN bus, and to at least one sensor line 54. The sensor line 54 leads to a sensor arranged on the inverter 26, for example, a temperature sensor (not shown). This sensor is also supplied with an electrical voltage via the low-voltage line 57. The inverter 26, which influences the operation of the electric machine 24, is connected via a high-voltage line 58 to the electrical voltage source (not shown separately).

[0060] To start and operate the electric motor 24 of the compressor 4, it is controlled in the desired manner by means of the control and regulating unit 28 and the inverter 26. This sets the two drive shafts 30, 32 of the electric motor 24 in rotation. The first drive shaft 30 is drivingly connected to the first air compressor 16, and the second drive shaft 32 is drivingly connected to the second air compressor 18. The two air compressors 16, 18 are known scroll compressors. The first air compressor 16 is connected to the ambient air L on the inlet side via an air inlet opening 8 in the housing 6. When the first air compressor 16 is operating, it draws in ambient air L and compresses it to compressed air with a first air pressure value.

[0061] The first air compressor 16 is pneumatically connected on the output side via a first compressed air line DL1, the intercooler 20, and then via a second compressed air line DL2 to the inlet of the second air compressor 18. The intercooler 20 cools the pre-compressed compressed air, condensing any water and removing it. In the second air compressor 18, the cooled compressed air is then further compressed to a desired second, higher air pressure value and subsequently fed to the aforementioned aftercooler 22 via a third compressed air line DL3. The compressed air is further cooled in the aftercooler 22. In the process, water condenses from the compressed air.

[0062] From the outlet of the aftercooler 22, the cooled and still residually moist compressed air flows via a fourth compressed air line DL4 to an inlet-side collection area 49 of the air dryer 40. The already condensed water also reaches this collection area 49 of the air dryer 40 in the form of entrained small droplets or as a water film. From there, the water is expelled from the air dryer 40 during a later regeneration process via the regeneration air outlet 42. As a result, the condensed water did not reach the drying agent 41 of the air dryer 40, as is also schematically illustrated in the only drawing figure with small droplets. The compressed air, partially dehydrated in this way and still residually moist, flows from the short fourth compressed air line DL4 into the drying agent 41 of the air dryer 40, flows through this drying agent 41 in a drying air stream 23, and is dried there.The desiccant 41 is capable of removing humidity from the supplied compressed air and releasing it back into dry air during a later regeneration process.

[0063] The dried compressed air then leaves the air dryer 40 via a spring-loaded first check valve 29, which blocks the air dryer 40, and then enters a fifth compressed air line DL5. This fifth compressed air line DL5 leads to the multi-circuit protection valve 50, which is at least indirectly controlled by the control and regulating device 28. For this purpose, the multi-circuit protection valve 50 is connected to the control and regulating device 28 via a sensor line 56. The dried compressed air can be directed via the multi-circuit protection valve 50, for example, through the aforementioned sixth compressed air line DL6 and a compressed air outlet opening 10 in the housing 6 to the first compressed air consumer 51 and via the aforementioned seventh compressed air line DL7 to the second compressed air consumer 52.The multi-circuit protection valve 50 can direct dried compressed air to at least one compressed air reservoir 45 via an eighth compressed air line DL8. Other compressed air consumers and / or compressed air reservoirs (not shown) can also be supplied with compressed air as needed via the compressed air reservoir 45. The compressed air stored in the compressed air reservoir 45 can also be supplied to other compressed air consumers via the multi-circuit protection valve 50 if needed, or can be returned to the fifth compressed air line DL5 for regeneration of the desiccant 41 of the air dryer 40.

[0064] When a predetermined air pressure is set at the compressed air consumers 51, 52 and in the at least one compressed air reservoir 45, and the electric motor 24 of the compressor module 90 is switched off, the moisture-saturated desiccant 41 arranged in the air dryer 40 can be regenerated, i.e., freed from the water stored there. For this purpose, the compressed air generating device 2 has a regeneration line DL5a. This regeneration line DL5a is connected via the fifth compressed air line DL5 to at least the eighth compressed air line DL8 leading to the compressed air reservoir 45, as well as to the air dryer 40. A 3 / 2-way solenoid valve 72 is arranged in the regeneration line DL5a, which can be controlled by the control and regulating unit 28 and is connected thereto via a control line 55.

[0065] When the 3 / 2-way solenoid valve 72 is not actuated, the regeneration line DL5a is closed, preventing compressed air from passing from the compressed air reservoir 45 to the air dryer 40 via the multi-circuit protection valve 50. To perform regeneration operation of the air dryer 40, the 3 / 2-way solenoid valve 72 is actuated, opening the regeneration line DL5a. This causes a portion of the dried compressed air to flow from the compressed air reservoir 45 through a first branch DL5b of the regeneration line DL5a to an orifice plate 75. There, the dried compressed air is expanded, causing it to occupy a larger volume. The compressed air then passes through a second spring-loaded check valve 76 and then enters the air dryer 40 via a regeneration compressed air inlet 70.The expanded compressed air then flows through the air dryer 40 and the desiccant 41 arranged therein in a regeneration compressed air stream 77, provided a pressure-controlled 2 / 2-way switching valve 39, which functions as a drain valve, is open at the collection area 49 of the air dryer 40. To actuate this pressure-controlled 2 / 2-way switching valve 39, another portion of the dried compressed air is routed behind the outlet of the 3 / 2-way solenoid valve 72 through a second line branch DL5c to this pressure-controlled 2 / 2-way switching valve 39. The pressure-controlled 2 / 2-way switching valve 39 is designed such that in its unactuated switching position it closes a connection from the collection area 49 of the air dryer 40 to a regeneration air outlet 42 of the air dryer 40 and opens it in the actuated switching state.Accordingly, the pressure-controlled 2 / 2-way switching valve 39 is open when the 3 / 2-way solenoid switching valve 72 has also been switched to its open position.

[0066] According to an alternative embodiment, instead of the 3 / 2-way solenoid valve 72, there are two 2 / 2-way solenoid valves that can be controlled by the control and regulating unit 28. These two 2 / 2-way solenoid valves are not shown in the drawing, but their arrangement will be easily understood by a person skilled in the art based on the following description. The first 2 / 2-way solenoid valve is arranged upstream of the orifice 75 in the first line branch DL5b, in the flow direction of the regeneration compressed air, and the second 2 / 2-way solenoid valve is arranged upstream of the pressure-controlled 2 / 2-way solenoid valve 39 in the second line branch DL5c. In addition, the fifth compressed air line DL5 is connected in the flow direction of regeneration compressed air upstream of the two 2 / 2-way solenoid valves directly to the first line branch DL5b and directly to the second line branch DL5c.

[0067] As soon as these two 2 / 2-way solenoid valves are switched to their open position, dry regeneration compressed air can be passed through the air dryer 40 into the silencer 43 in order to dry the drying agent 41, with the pressure-controlled 2 / 2-way switching valve 39 also opened.

[0068] By means of this design, the collection area 49 of the air dryer 40 can also be advantageously freed of water W accumulated there by compressed air supplied via the aftercooler 22 when the first 2 / 2-way solenoid valve is closed, the second 2 / 2-way solenoid valve is open, and the pressure-controlled 2 / 2-way switching valve 39 is thus opened. With the 2 / 2-way switching valve 39 opened under pressure control, the expanded compressed air flows through the desiccant 41 in the aforementioned regeneration compressed air stream 77 toward the silencer 43. In the process, moisture is removed from the desiccant 41. The compressed air thus enriched with moisture, as well as the previously condensed water accumulated in the collection area 49 of the air dryer 40, then leaves the air dryer 40 via its regeneration air outlet 42 and thus enters the silencer 43.

[0069] The moist exhaust air AL then flows through the sound-damping material 44 arranged in the silencer 43 via an exhaust air path 78 to the at least one regeneration air outlet opening 34 of the silencer 43 of the compressed air generation device 2. Water droplets that may have formed in the regeneration compressed air flow or that form in the sound-damping material 44 of the silencer 43 as the regeneration compressed air flow flows through it, as well as the condensed water from the collection area 49 of the air dryer 40, flow in the silencer 43 via the aforementioned water separation path 80 to the at least one water outlet opening 36 of the silencer 43. The water outlet opening 36 of the silencer 43 also serves to remove any spray water that may have penetrated into the silencer 43 via the at least one regeneration air outlet opening 34.

[0070] The regeneration process is terminated when a predetermined sufficiently large regeneration compressed air volume has flowed through the drying agent 41 of the air dryer 40 in order to be able to use it for a further air drying phase.

[0071] Of great importance for the inventive design of the compressed air generating device 2 is the flow path of the liquid coolant supplied by the external cooling device 82. This coolant is cooled to a predetermined temperature in the external cooling device 82 and supplied to the compressed air generating device 2 via a coolant supply line Kin. The cooling activity of the external cooling device 82 is controlled and regulated by a control and regulating device 28. In a preferred control of the coolant temperature, the current actual temperature of the coolant is measured with a first temperature sensor 73 at the outlet of the cooling device 82, and the coolant temperature is then regulated to a predetermined setpoint value of the coolant temperature. For this purpose, the first temperature sensor 73 is connected to the control and regulating device 28 via the data and / or sensor line 59 of the CAN bus.

[0072] The coolant passes from the external cooling device 82 through a coolant inlet opening 12 into the compressed air generation device 2 and into the compressed air cooling module 92. The coolant then flows through a first coolant line KL1 into the aftercooler 22, where it cools the compressed air generated by the compressor 4 as much as possible. Since the coolant is first fed into the aftercooler 22, the lowest temperature of the coolant within the compressed air generation device 2 can be utilized. As a result, the compressed air is comparatively cooled before it enters the air dryer 40, as a result of which some of the entrained air humidity condenses and is at least partially separated in the aftercooler 22. The condensed water is also fed into the collection area 49 of the air dryer 40 and from there discharged into the environment either directly or via the silencer 43.This process removes a lot of moisture from the compressed air before it reaches the air dryer 40. This is even more so the lower the temperature of the coolant.

[0073] As a result, the drying agent 41 of the air dryer 40 needs to be dried less frequently in regeneration processes compared to conventional compressed air generation devices, or such regeneration processes can be carried out with a smaller volume of regeneration compressed air than usual. As a result, more of the dry compressed air stored in the compressed air reservoir 45 is available for the compressed air consumers 51, 52, so that the electric motor 24 of the compressor 4 of the compressed air generation device 2 needs to be operated less frequently. As a result, when such a compressed air generation device 2 is arranged and operated in a vehicle, for example, the consumption of electrical energy is reduced, which reduces the vehicle's exhaust emissions and thus its CO emissions.The frequency of the regeneration processes or the respective required regeneration compressed air volume can therefore be lower the lower the coolant temperature at the inlet of the aftercooler 22. Therefore, it is advantageous if the control of the actuation frequency and / or the actuation duration of the 3 / 2-way solenoid valve 72 by means of the control and regulating unit 28 also takes place as a function of the coolant temperature. For this purpose, as already briefly mentioned, according to the exemplary embodiment illustrated in the single figure, a first temperature sensor 73 is arranged in the area of ​​the outlet of the external cooling device 82 or in the area at the coolant inlet opening 12, by means of which the temperature of the liquid coolant can be measured. Such a temperature sensor 73 is usually already a component of the cooling device 82.The temperature measurements thus obtained can be transmitted to the control and regulating unit 28 via the aforementioned data and / or sensor line 59. The control and regulating unit 28 then controls and regulates the regeneration of the desiccant 41 of the air dryer 40, taking into account the current coolant temperature, directly via the actuation frequency and / or duration of the 3 / 2-way solenoid valve 72 and indirectly via the pressure-controlled 2 / 2-way switching valve 39.

[0074] As the single figure shows as an alternative solution, the temperature of the coolant can also be measured at the coolant inlet of the aftercooler 22 by means of a second temperature sensor 73' and / or at the coolant outlet of the aftercooler 22 by means of a third temperature sensor 73", which are also connected to the control and regulating device 28 via the data and / or sensor line 59. The data and / or sensor line 59, which is connected to the respective temperature sensor 73', 73", can also be arranged completely within the compressed air generation device 2, unlike as shown in the single figure.

[0075] With such a control system, it should also be noted that the temperature of the coolant can fluctuate during operation of the compressed air generation device 2. This can be caused by different load conditions of the vehicle and its systems and / or by rapidly changing ambient temperatures. Since the current temperature of the coolant is measured by the first temperature sensor 73 in most vehicles anyway for the control of the aforementioned external cooling device 82, its current value is available to the control and regulating unit 28 via the aforementioned data and / or sensor line 59 of the CAN bus. Based on the current value of the coolant temperature, the control and regulating unit 28 can therefore quickly control and regulate the actuation duration of the 3 / 2-way solenoid valve 72 and thus the frequency and duration of a regeneration process on the dryer 40 at any time, depending on the temperature.

[0076] Since in most vehicles currently on the road the ambient temperature of the vehicle is also measured by means of an ambient temperature sensor 74 and displayed on a display element, the ambient temperature is also available to the control and regulating unit 28 via the data and / or sensor line 59 of the CAN bus for controlling and regulating the actuation duration of the 3 / 2-way solenoid valve 72 and thus for controlling and regulating the frequency and duration of a regeneration process on the air dryer 40.

[0077] The ambient temperature of the vehicle is also of particular importance for the control and regulation of the regeneration processes, since the compressed air, after being dried in the dryer 40, cools further to the temperature of the compressed air reservoir 45 or the compressed air consumers 51, 52, which generally have the ambient temperature. During this further cooling process, the relative humidity in the compressed air increases again. To prevent corrosion processes or even water condensing and freezing into ice due to excessive humidity in the compressed air reservoirs and compressed air consumers at low ambient temperatures compared to the coolant temperature, the degree of dryness of the compressed air must ideally also take the current ambient temperature into account.

[0078] This degree of drying can be adjusted via the volume of regeneration compressed air used during a regeneration process and / or via the frequency of regeneration processes within a given period of time. If, for example, an actually excessive volume of regeneration compressed air is used during a regeneration process, the drying agent 41 will be drier than required according to previously known practice. During a subsequent conveying process, the compressed air passed through the air dryer 40 will therefore lose more moisture than previously necessary, whereby the compressed air has a higher degree of drying upon leaving the air dryer 40. During a subsequent further cooling of the compressed air in a compressed air tank or in a compressed air consumer, the degree of drying of the compressed air is then advantageously uncritically high, so that condensation and possible ice formation do not occur there.

[0079] The control and regulating unit 28 thus controls and regulates the regeneration compressed air volume and / or the frequency of the regeneration processes depending on the coolant temperature at a constant ambient temperature, and depending on the ambient temperature at a constant coolant temperature. If both the ambient temperature and the coolant temperature change, the duration and / or frequency of the regeneration processes are controlled and regulated depending on the difference between the two temperatures.

[0080] If such a control is omitted, the volume of regeneration compressed air required for a regeneration process must also cover the worst-case scenario, i.e., the highest coolant temperature expected during operation of the compressed air generation device 2. As a result, such a regeneration process for the drying agent 41 would always be carried out with a previously determined maximum regeneration compressed air volume.

[0081] After the liquid coolant has flowed through the aftercooler 22, it reaches the aforementioned intercooler 20 via a second coolant line KL2. There, it cools the compressed air pre-compressed by the first air compressor 16. After cooling the pre-compressed compressed air in the intercooler 20, the liquid coolant is conducted via a third coolant line KL3 to a cooling device 25 of the electric motor 24. There, the coolant cools, for example, the stator of the electric motor 24.

[0082] The coolant then flows through a fourth coolant line KL4 to a cooling device 48 of the second air compressor 18 of the compressor 4, which is thereby cooled during its compression operation. The coolant then flows through a fifth coolant line KL5 to a cooling device 27 of the inverter 26 to cool the inverter. Subsequently, the coolant is conducted through a sixth coolant line KL6 to a cooling device 46 of the first air compressor 16 of the compressor 4 to cool the inverter as well. Finally, the heated coolant is conducted through a coolant outlet opening 14 from the compressor module 90 and from the housing 6 of the compressed air generation device 2 via a coolant discharge line Kout to the external cooling device 82.

[0083] Investigations have shown that the described comparatively strong cooling of the compressed air in the aftercooler 22 has no negative impact on the operation of the compressed air generation device 2. Further advantages are even apparent. This will be explained using the following example:

[0084] In this case, a compressed air generating device 2 designed according to the invention is installed in a truck, and to cool the liquid coolant mentioned, it uses the cooling system that also cools the truck's internal combustion engine. During a cold start of the internal combustion engine, i.e., starting it at a very low ambient temperature, it is advantageous with regard to the operating characteristics of a vehicle battery, low exhaust emissions from the truck, and the provision of warm air by means of an interior heater in the truck if the temperature of the internal combustion engine's cooling system is quickly increased above the ambient temperature. Because the electrically operated compressed air generating device 2 is immediately activated to generate the compressed air required for operation during the cold start of the internal combustion engine, it is cooled as much as possible by the liquid coolant.The waste heat thus extracted from the compressed air generation device 2, in particular the heat generated by the operation of the electric motor 24, the inverter 26, and the two air compressors 16, 18, then advantageously serves indirectly to relieve the load on the vehicle battery by heating the liquid coolant. During the cold start period and a short warm-up phase of the truck, temperatures at which water ice can form can also be tolerated at the aftercooler 22 and at the inlet of the air dryer 40. Since the warm-up phase is comparatively short, any water ice formed at the aftercooler 22 and at the inlet of the air dryer 40 will evaporate during the subsequent normal operating phase and be absorbed into the compressed air as air humidity. List of reference symbols (part of the description).

[0085] 2 Compressed air generation device

[0086] 4 Compressor

[0087] 6 Housing of the compressed air generation device

[0088] 8 Air intake opening

[0089] 10 Compressed air outlet opening

[0090] 12 Coolant inlet opening

[0091] 14 Coolant outlet opening

[0092] 16 First air compressor

[0093] 18 Second air compressor

[0094] 20 intercoolers, air coolers

[0095] 22 aftercoolers, air coolers

[0096] 23 Drying air flow in the air dryer

[0097] 24 electric motor

[0098] 25 Cooling device of the electric motor

[0099] 26 inverters

[0100] 27 Inverter cooling device

[0101] 28 Control and regulating device

[0102] 29 First check valve

[0103] 30 First drive shaft

[0104] 32 Second drive shaft

[0105] 34 Regeneration air outlet opening

[0106] 36 Water outlet opening of the silencer

[0107] 39 2 / 2-way switching valve, drain valve on the air dryer

[0108] 40 air dryers

[0109] 41 Desiccant in the air dryer

[0110] 42 Regeneration air outlet of the air dryer

[0111] 43 silencers

[0112] 44 Sound-absorbing material

[0113] 45 compressed air storage

[0114] 46 Cooling device of the first air compressor

[0115] 48 Cooling device of the second air compressor

[0116] 49 Air dryer collection area for water droplets 50 Multi-circuit protection valve

[0117] 51 First compressed air consumer

[0118] 52 Second compressed air consumer

[0119] 54 Sensor cable

[0120] 55 Control cable from the control and regulation unit to the 3 / 2-way

[0121] Solenoid valve

[0122] 56 Sensor cable from the control and regulation unit to the multi-circuit protection valve

[0123] 57 Low-voltage line

[0124] 58 high-voltage line

[0125] 59 Data or sensor cable, CAN bus

[0126] 70 Regeneration compressed air inlet of the air dryer

[0127] 72 3 / 2-way solenoid valve

[0128] 73 First temperature sensor (coolant measurement)

[0129] 74 Ambient temperature sensor

[0130] 75 aperture

[0131] 76 Second check valve

[0132] 77 Regeneration compressed air flow in the air dryer

[0133] 78 Exhaust air path in the silencer

[0134] 80 Water separation path in the silencer

[0135] 82 External cooling device

[0136] 90 compressor module

[0137] 92 Compressed air cooling module

[0138] 94 Dryer module

[0139] 96 silencer module

[0140] L Ambient air

[0141] AL exhaust air

[0142] Kin coolant supply line

[0143] Kout coolant discharge line

[0144] W Water

[0145] DL1 First compressed air line

[0146] DL2 Second compressed air line

[0147] DL3 Third compressed air line

[0148] DL4 Fourth compressed air line

[0149] DL5 Fifth compressed air line DL5a Regeneration compressed air line

[0150] DL5b First line branch

[0151] DL5c Second line branch

[0152] DL6 Sixth compressed air line

[0153] DL7 Seventh compressed air line

[0154] DL8 Eighth compressed air line

[0155] KL1 First coolant line

[0156] KL2 Second coolant line

[0157] KL3 Third coolant line

[0158] KL4 Fourth coolant line

[0159] KL5 Fifth coolant line

[0160] KL6 Sixth coolant line

Claims

Patent claims 1. Compressed air generating device (2), comprising a control and regulating device (28), an electric motor (24) controllable and regulated by the control and regulating device (28), at least one air compressor (16; 18) driven by the electric motor (24), an air inlet (8) through which ambient air (L) can be drawn into the at least one air compressor (16; 18), at least one air cooler (20; 22) connected to the outlet of the at least one air compressor (16; 18), at least one air dryer (40) connected to the outlet of the at least one air cooler (20; 22), and a coolant inlet opening (12) through which coolant is supplied to the at least one air cooler (20;22) and other components of the compressed air generation device (2) a liquid coolant can be supplied, with a coolant outlet opening (14) through which heated coolant can be discharged from the compressed air generation device (2), and with at least one temperature sensor (73, 73', 73") which is connected to the control and regulating device (28) via a data or sensor line (59), characterized in that the temperature sensor (73, 73', 73") for measuring the coolant temperature is arranged upstream of the coolant inlet or downstream of the coolant outlet of the air cooler (22) which is arranged as the last air cooler upstream of the air dryer (40) in the direction of compressed air flow.

2. Compressed air generating device according to claim 1, characterized in that the temperature sensor (73) for measuring the coolant temperature is arranged in front of the coolant inlet opening (12) of the compressed air generating device (2).

3. Compressed air generation device according to claim 1, characterized in that the temperature sensor (73') for measuring the coolant temperature is arranged directly in front of the coolant inlet of the air cooler (22) which is arranged as the last air cooler in front of the air dryer (40) in the direction of flow of the compressed air.

4. Compressed air generation device according to claim 1, characterized in that the temperature sensor (73") for measuring the coolant temperature is arranged as the next component following the coolant outlet of the air cooler (22) which is arranged as the last air cooler in the direction of flow of the compressed air before the air dryer (40).

5. Compressed air generation device (2) according to one of claims 1 to 4, characterized in that the air cooler (22) which is arranged as the last air cooler upstream of the air dryer (40) in the direction of flow of the compressed air is arranged in such a way that it is the first one through which the coolant can flow when viewed in the direction of flow of the coolant.

6. Compressed air generating device (2) according to any one of claims 1 to 5, comprising: an electric motor (24), two air compressors (16, 18) driven by the electric motor (24) and acting sequentially, an air inlet (8) through which ambient air (L) can be drawn in by means of the first air compressor (16), two air coolers for cooling the compressed air, which are designed and arranged as an intercooler (20) and an aftercooler (22), respectively, wherein the inlet of the intercooler (20) is pneumatically connected to the outlet of the first air compressor (16), wherein the outlet of the intercooler (20) is pneumatically connected to the inlet of the second air compressor (18), wherein the outlet of the second air compressor (18) is pneumatically connected to the inlet of the aftercooler (22), and wherein the outlet of the aftercooler (22) is pneumatically connected to the inlet of an air dryer (40). is, as well as a coolant inlet opening (12),a liquid coolant can be supplied to the intercooler (20) and the aftercooler (22) via a coolant outlet opening (14) through which heated coolant can be discharged, characterized in that the aftercooler (22) is arranged such that, viewed in the direction of flow of the coolant, it is the first part through which the coolant flows, and that at least one temperature sensor (73, 73', 73") is provided, which is arranged upstream or downstream of the aftercooler (22) for measuring the temperature of the coolant in the direction of flow.

7. Compressed air generating device according to claim 6, characterized in that the electric motor (24), an inverter (26) influencing the operation of the electric motor (24), the two air compressors (16, 18), the intercooler (20), the aftercooler (22), the air dryer (40), a multi-circuit protection valve (50) which pneumatically connects the outlet of the air dryer (40) with at least one external compressed air storage tank (45) and external compressed air consumers (51, 52), and a silencer (43) are arranged in a cooperating manner, but separately in relation to each other.

8. Compressed air generating device according to claim 6, characterized in that the electric motor (24), an inverter (26) influencing the operation of the electric motor (24), the two air compressors (16, 18), the intercooler (20), the aftercooler (22), the air dryer (40), a multi-circuit protection valve (50) which pneumatically connects the outlet of the air dryer (40) with at least one external compressed air storage tank (45) and external compressed air consumers (51, 52), and a silencer (43) are arranged in or on a common housing (6).

9. Compressed air generation device according to one of claims 7 or 8, characterized in that the control and regulating device (28) is arranged separately or in or on the housing (6), that the control and regulating device (28) is connected to the inverter (26) for controlling the electric motor (24) via a first control line (54), that the control and regulating device (28) is connected to a 3 / 2-way solenoid switching valve (72) via a second control line (55), which serves to open or close a regeneration line (DL5a) that pneumatically connects the compressed air storage tank (45) and the air dryer (40) at least indirectly, and that the control and regulating device (28) is connected to the multi-circuit protection valve (50) via a sensor line (56).

10. Compressed air generating device according to one of claims 6 to 9, characterized in that a compressor module (90), a compressed air cooling module (92), a dryer module (94) and a silencer module (96) together with associated pneumatic, hydraulic and electrical lines are arranged one behind the other in or on the housing (6), wherein the compressor module (90) powers the electric motor (24), the inverter (26), the two air compressors (16, 18) and the control and regulating device (28), wherein the compressed air cooling module (92) comprises the intercooler (20) and the aftercooler (22), wherein the dryer module (94) comprises the air dryer (40) and the multi-circuit protection valve (50), wherein the silencer module (96) comprises the silencer (43) with a sound-absorbing material (44), and wherein the silencer module (96) has at least one regeneration air outlet opening (34) for discharging regeneration compressed air into the environment.

11. Compressed air generating device according to one of claims 6 to 10, characterized in that the outlet of the air dryer (40) is connected via a first check valve (29) closing towards the air dryer (40) by means of a fifth compressed air line (DL5), that the fifth compressed air line (DL5) leads via the multi-circuit protection valve (50) to the at least one compressed air reservoir (45) and to compressed air consumers (51, 52), that a regeneration compressed air inlet (70) of the air dryer (40) is connected via a second check valve (76) opening towards the regeneration compressed air inlet (70), an orifice (75) and a first line branch (DL5b) to the outlet of the 3 / 2-way solenoid valve (72), that the inlet of this 3 / 2-way solenoid valve (72) is connected via a regeneration compressed air line (DL5a) to the fifth compressed air line (DL5). is,that when the 3 / 2-way solenoid valve (72) is actuated, dry compressed air can be supplied to the air dryer (40) via this 3 / 2-way solenoid valve (72), the first line branch (DL5b), the orifice (75) and the first check valve (76) as regeneration compressed air; that when the 3 / 2-way solenoid valve (72) is actuated, regeneration compressed air can be supplied to the pneumatic control input of a 2 / 2-way switching valve (39); and that a regeneration air outlet (42) of the air dryer (40) is assigned to the 2 / 2-way switching valve (39).

12. Compressed air generating device according to claim 11, characterized in that the air dryer (40) has a collection area (49), that the inlet of this collection area (49) is pneumatically connected to the outlet of the aftercooler (22) via the fourth compressed air line (DL4), and that the collection area (49) is designed in such a way that water condensed from the compressed air and carried along can accumulate in it and be removed from there.

13. Compressed air generating device according to claim 12, characterized in that the pressure-controlled 2 / 2-way switching valve (39) is assigned to the collecting area (49) of the air dryer (40), that the control input of the pressure-controlled 2 / 2-way switching valve (39) is connected to the output of the 3 / 2-way solenoid switching valve (72) via a second line branch (DL5c), that the 2 / 2-way switching valve (39) is closed in the unactuated state, that the 2 / 2-way switching valve (39) can be switched from its closed position to its open position by means of regeneration compressed air supplied to the air dryer (40) and via the second line branch (DL5c), that when the 2 / 2-way switching valve (39) is open, the desiccant (41) of the air dryer (40) is in a Regeneration compressed air flow (77) Regeneration compressed air can be directed,that the regeneration compressed air, after flowing through the desiccant (41), can be directed into the collection area (49) of the air dryer (40) and can carry away any accumulated condensed water, and that the regeneration compressed air can leave the air dryer (40) via a regeneration air outlet (42).

14. Compressed air generation device according to one of claims 9 to 13, characterized in that instead of the 3 / 2-way solenoid switching valve (72), two 2 / 2-way solenoid switching valves controllable by the control and regulating device (28) are provided, wherein the first 2 / 2-way solenoid switching valve is arranged upstream of the orifice (75) in the first line branch (DL5b) in the direction of flow of regeneration compressed air, wherein the second 2 / 2-way solenoid switching valve is arranged upstream of the pressure-controlled 2 / 2-way switching valve (39) in the second line branch (DL5c), and wherein the fifth compressed air line (DL5) is connected directly to the first line branch (DL5b) and directly to the second line branch (DL5c) upstream of the two 2 / 2-way solenoid switching valves in the direction of flow of regeneration compressed air.

15. Compressed air generation device according to one of claims 1 to 14, characterized in that the compressed air generation device (2) has an ambient temperature sensor (74) by means of which the ambient temperature is measurable, and that this ambient temperature sensor (74) is connected to the control and regulating device (28) via a data or sensor line (59).

16. Method for operating a compressed air generation device (2) with the features of at least one of the device claims, wherein compressed air by means of the at least one air compressor (16, 18) is cooled in at least one air cooler (20, 22), wherein this cooled compressed air is supplied to an air dryer (40) and dried there, wherein the dried compressed air is supplied to compressed air consumers (51, 52) and / or at least one compressed air storage tank (45), and wherein, for the regeneration of a desiccant (41) arranged in the air dryer (40), dry compressed air in the volume of a regeneration compressed air volume is passed through it and subsequently discharged into the environment, characterized in that the regeneration compressed air volume necessary for the regeneration of the desiccant (41) is calculated at least as a function of the temperature,which has the coolant before and / or after flowing through the air cooler (22) which is arranged as the last air cooler (22) before the air dryer (40), and that the regeneration compressed air volume determined in this way is then passed through the air dryer (40).

17. Method according to claim 16, characterized in that the coolant temperature is measured by means of a first temperature sensor (73) in front of the coolant inlet opening (12) of the compressed air generating device (2), and that the regeneration compressed air volume required for drying the desiccant (41) in the air dryer (40) is controlled and / or regulated through the air dryer (40) depending on the measured coolant temperature.

18. Method according to claim 16, characterized in that the coolant temperature is measured by means of a second temperature sensor (73') immediately before the coolant inlet of the air cooler (22) which is arranged as the last air cooler before the air dryer (40) in the direction of flow of the compressed air, and that the regeneration compressed air volume required for drying the desiccant (41) in the air dryer (40) is determined as a function of The coolant temperature is controlled and / or regulated by the air dryer (40).

19. Method according to claim 16, characterized in that the coolant temperature is measured by means of a third temperature sensor (73") downstream of the coolant outlet of the air cooler (22) which is arranged as the last air cooler upstream of the air dryer (40) in the direction of flow of the compressed air, and that the regeneration compressed air volume required for drying the desiccant (41) in the air dryer (40) is controlled and / or regulated through the air dryer (40) depending on the measured coolant temperature.

20. Method according to claim 16, characterized in that the temperature of an inverter (26) provided for controlling and regulating the electric motor (24) is measured, that the measured temperature of the inverter (26) is used to calculate the coolant temperature in the air cooler (22) which is arranged as the last air cooler (22) upstream of the air dryer (40) in the direction of flow of the compressed air, and that the regeneration compressed air volume required for drying the desiccant (41) in the air dryer (40) is controlled and / or regulated through the air dryer (40) depending on the coolant temperature determined in this way.

21. Method for operating the compressed air generating device (2) with the features of at least one of the device claims and with the features of at least one of the method claims 16 to 20, characterized by the following method steps: a) drawing in ambient air by means of the first air compressor (16), b) pre-compressing the drawn-in ambient air in the first air compressor (16) to a first air pressure value, c) cooling an intercooler (20) with a liquid coolant, d) cooling the pre-compressed compressed air in the intercooler (20), e) further compressing the compressed air to a second, higher pressure value by means of a second air compressor (18), f) cooling an aftercooler (22) with the liquid coolant, wherein the aftercooler- g) the first air cooler (22) seen in the direction of flow of the coolant is hydraulically reached by the coolant, g) cooling of the compressed air further compressed in the second air compressor (18) in the aftercooler (22), h) drying of the cooled compressed air in an air dryer (40), i) forwarding of the cooled and dried compressed air to compressed air consumers (51 , 52) and / or to at least one compressed air storage tank (45).

22. The method according to claim 21, characterized by the following further method steps: j) transferring the liquid coolant from the aftercooler (22) to the intercooler (20), k) transferring the liquid coolant from the intercooler (20) to a cooling device (25) of the electric motor (24), l) transferring the liquid coolant from the cooling device (25) of the electric motor (24) to a cooling device (48) of the second air compressor (18), m) transferring the liquid coolant from the cooling device (48) of the second air compressor (18) to a cooling device (27) of the inverter (26), n) transferring the liquid coolant from the cooling device (27) of the inverter (26) to a cooling device (46) of the first air compressor (18), o) transferring the liquid coolant from the cooling device (46) of the first air compressor (18) to an external cooling device (82).

23. Method according to one of claims 16 to 22, characterized in that the time interval between two regeneration processes for drying the desiccant (41) of the air dryer (40) is controlled and / or regulated depending on the temperature of the coolant which the coolant has at the outlet of the external cooling device (82) or at the inlet of the aftercooler (22).

24. Method according to one of claims 16 to 23, characterized in that the time interval between two regeneration processes for drying the desiccant (41) of the air dryer (40) is controlled and / or regulated depending on the ambient temperature.

25. Method according to one of claims 16 to 24, characterized in that the regeneration compressed air volume required for drying the desiccant (41) is controlled and / or regulated depending on the ambient temperature.

26. Method according to one of claims 16 to 25, characterized in that the regeneration compressed air volume required for drying the desiccant (41) or the duration and / or frequency of the regeneration processes is controlled and / or regulated as a function of the difference between the ambient temperature and the coolant temperature.

27. Method according to one of claims 16 to 26, characterized in that, in the case of an unregulated control of the regeneration of the desiccant (41 ) of the air dryer (40), a maximum temperature value of the coolant expected during the operation of the compressed air generation device (2) is determined, that this value of the coolant temperature serves as the basis for determining a maximum regeneration compressed air volume, and that a corresponding regeneration process for the desiccant (41 ) is carried out with this maximum regeneration compressed air volume.

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