SCREW COMPRESSOR FOR A COMMERCIAL VEHICLE

Description

[0001] The present invention relates to a screw compressor for a commercial vehicle.

[0002] Screw compressors for commercial vehicles are already known from the state of the art. Such screw compressors are used to provide the necessary compressed air for, for example, the commercial vehicle's braking system.

[0003] In this context, oil-filled compressors, especially screw compressors, are particularly well known, where the task of regulating the oil temperature is important. This is usually achieved by having an external oil cooler connected to the oil-filled compressor and the oil circuit via a thermostatic valve. The oil cooler is a heat exchanger with two separate circuits, the first for the hot fluid, i.e., the compressor oil, and the second for the cooling fluid. The cooling fluid can be, for example, air, a mixture of water with antifreeze, or another oil.

[0004] This oil cooler must then be connected to the compressor oil circuit via pipes or hoses and the oil circuit must be protected against leaks.

[0005] This external volume must also be filled with oil, increasing the total oil volume. This increases the system inertia. Furthermore, the oil cooler must be mechanically housed and secured, either through surrounding brackets or through a separate bracket, which requires additional mounting hardware and installation space.

[0006] A screw compressor with integrated oil cooling is already known from US 4,780,061.

[0007] From DE 10 2014 004 726 A1 a separation device for a screw compressor is known, which comprises a pre-separation device, a fine separation device and an oil filter device.

[0008] From JP 2002-115690 an oil cooling system for a screw compressor is also known, which is a screw compressor for a vacuum pump.

[0009] DE 10 2011 014 961 A1 also discloses a screw compressor system with a compact and flexible modular design. The base housing with a cover contains a screw compressor block, an oil separator tank, an oil supply duct for a temperature regulator, and an air intake duct. A further modular component is a multifunctional block, which combines a fine separator, an oil return line, a minimum pressure valve with clean air outlet, an oil temperature regulator, an oil filter, and connections for a sensor.

[0010] From DE 133 154 A1, a screw compressor system is known in which a pressure vessel is detachably fastened to a connecting flange by connecting elements on a compressor housing containing a screw rotor in such a way that the air volume flow is guided from the compressor housing to the pressure vessel via this connecting flange and into the compressed air, which is largely free of oil, is returned via the connecting flange to the compressor housing.

[0011] Furthermore, DE 37 17 493 A1 discloses a screw compressor system arranged in a compact housing, which has an oil cooler on the electric motor of the screw compressor.

[0012] It is the object of the present invention to advantageously further develop a screw compressor for a commercial vehicle of the type mentioned at the outset, in particular in such a way that it has a simpler construction and the thermal inertia of the overall system can be reduced.

[0013] This object is achieved according to the invention by a screw compressor having the features of claim 1. According to this, it is provided that a screw compressor for a commercial vehicle is provided with a housing, wherein the housing is filled with oil, wherein the screw compressor further comprises at least a pair of compressor screws (also called compressor rotors) which are mounted in the housing and serve to compress the fluid, in particular air, supplied to the screw compressor, wherein in the assembled state of the screw compressor a heat exchanger is placed and mounted directly on the housing, by means of which heat exchanger the temperature of the oil contained in the housing can be regulated.

[0014] The invention is based on the basic idea that by directly placing the heat exchanger on the housing, the total required volume and also the dead volume of oil can be reduced. In particular, by directly placing the heat exchanger on the housing of the screw compressor, no long connection paths from the screw compressor housing into the heat exchanger are required. Instead, the oil can be fed directly from the screw compressor into the heat exchanger. The required oil volume is thus kept comparatively low. The thermal inertia of the system is reduced. In other words, the dead volume is reduced, or the volume that must be filled with oil in order to fill the lines between the housing interior and the heat exchanger with oil and enable oil circulation.In addition, this significantly reduces the risk of leaks because the required cables need to be avoided outside the housing or at least provided with a shorter length.

[0015] In comparison to the screw compressors known so far, the oil is brought up to operating temperature quickly, especially during the start-up phase, when the oil initially does not flow through the heat exchanger / cooler at all, controlled by the thermostat, and thus quickly reaches operating temperature.

[0016] Furthermore, the housing can be provided with an annular shoulder to accommodate the heat exchanger. This annular shoulder allows for easy and correct positioning of the heat exchanger on the housing. Furthermore, the annular shoulder also allows for simple and reliable sealing in both axial and radial directions.

[0017] In addition, two ring bosses can be provided in the housing, which can be used to attach the heat exchanger to the screw compressor housing. The double ring boss can improve the sealing effect, as it can, for example, enable a type of labyrinth seal. It can also be provided to use the space between the walls of the ring bosses as a fluid line between the housing and the heat exchanger.

[0018] In particular, the ring shoulders can be designed concentrically. This facilitates positioning of the heat exchanger on the housing. Furthermore, a concentric arrangement of the ring shoulders is also beneficial with regard to the sealing effect required to properly seal the heat exchanger at the interface to the housing.

[0019] Furthermore, the housing can be provided with a receptacle for a screw for fastening the heat exchanger. This allows for easy attachment of the heat exchanger to the housing using a screw.

[0020] In particular, it is conceivable that the screw receptacle is located inside the two ring attachments. This allows the heat exchanger to be centered over the two ring attachments and secured using the screw located inside the two ring attachments in essentially one simple step.

[0021] The screw used to secure the heat exchanger can be a hollow screw. This hollow screw allows oil to be fed into the heat exchanger or returned from the heat exchanger to the screw compressor housing.

[0022] In particular, it can be provided that the hollow screw serves as a fluid channel for the oil led to the heat exchanger or the oil led from the heat exchanger back into the housing.

[0023] It is conceivable that the heat exchanger is air-cooled.

[0024] The heat exchanger can be water-cooled. For example, the cooling water can be mixed with antifreeze, such as methylene glycol or the like.

[0025] Furthermore, a thermostat and a control and / or regulation device are provided, by means of which the temperature of the oil in the housing can be monitored and adjusted to a setpoint. This makes it possible to use the heat exchanger only when necessary. This makes it possible, for example, to reach operating temperature more quickly when starting up the screw compressor.

[0026] Further details and advantages of the invention will now be explained in more detail with reference to an embodiment shown in the drawings.

[0027] They show: Fig. 1 is a schematic sectional view of a screw compressor according to the invention; Fig. 2 is a perspective view of a screw compressor; Fig. 3 is a further perspective view of a screw compressor according to Fig. 2 ; and Fig. 4 a schematic, perspective sectional view through the heat exchanger and part of the housing of the screw compressor according to Fig. 2 .

[0028] Fig. 1 shows a schematic sectional view of a screw compressor 10 in the sense of an embodiment of the present invention.

[0029] The screw compressor 10 has a mounting flange 12 for mechanically fastening the screw compressor 10 to an electric motor not shown in detail here.

[0030] However, the input shaft 14 is shown, via which the torque from the electric motor is transmitted to one of the two screws 16 and 18, namely screw 16.

[0031] The screw 18 meshes with the screw 16 and is driven by it.

[0032] The screw compressor 10 has a housing 20 in which the essential components of the screw compressor 10 are accommodated.

[0033] The housing 20 is filled with oil 22.

[0034] On the air inlet side, an inlet nozzle 24 is provided on the housing 20 of the screw compressor 10. The inlet nozzle 24 is designed such that an air filter 26 is arranged thereon. Furthermore, an air inlet 28 is provided radially on the air inlet nozzle 24.

[0035] In the area between the inlet nozzle 24 and the point where the inlet nozzle 24 attaches to the housing 20, a spring-loaded valve insert 30 is provided, here designed as an axial seal.

[0036] This valve insert 30 serves as a check valve.

[0037] Downstream of the valve insert 30, an air supply channel 32 is provided which supplies the air to the two screws 16, 18.

[0038] An air outlet pipe 34 with a riser 36 is provided on the output side of the two screws 16, 18.

[0039] In the area of ​​the end of the riser pipe 36, a temperature sensor 38 is provided, by means of which the oil temperature can be monitored.

[0040] A holder 40 for an air de-oiling element 42 is also provided in the air outlet area.

[0041] The holder 40 for the air de-oiling element has, in the mounted state, in the area facing the ground (as in Fig. 1 shown) the air de-oiling element 42.

[0042] Furthermore, a corresponding filter screen or known filter and oil separation devices 44, which are not specified in detail, are provided inside the air de-oiling element 42.

[0043] In the central upper area, based on the assembled and ready-to-use state (i.e. as in Fig. 1 shown), the holder for the air-oil separator 40 has an air outlet opening 46 leading to a check valve 48 and a minimum pressure valve 50. The check valve 48 and the minimum pressure valve 50 can also be formed in a common, combined valve.

[0044] The air outlet 51 is provided downstream of the check valve 48.

[0045] The air outlet 51 is usually connected to correspondingly known compressed air consumers.

[0046] In order to return the oil 22 located in the air-oil separator 42 and separated back into the housing 20, a riser line 52 is provided which has a filter and check valve 54 at the outlet of the holder 40 for the air-oil separator 42 when it passes into the housing 20.

[0047] Downstream of the filter and check valve 54, a nozzle 56 is provided in a housing bore. The oil return line 58 leads back to approximately the middle area of ​​the screw 16 or the screw 18 to supply it with oil 22 again.

[0048] An oil drain plug 59 is provided in the bottom area of ​​the housing 20 when assembled. A corresponding oil drain opening can be opened via the oil drain plug 59, through which the oil 22 can be drained.

[0049] The lower portion of the housing 20 also contains the boss 60, to which the oil filter 62 is attached. The oil 22 is initially directed to a thermostat valve 66 via an oil filter inlet channel 64 located in the housing 20.

[0050] Instead of the thermostatic valve 66, a control and / or regulating device can be provided by means of which the oil temperature of the oil 22 located in the housing 20 can be monitored and adjusted to a desired value.

[0051] Downstream of the thermostat valve 66 is the oil inlet of the oil filter 62, which, via a central return line 68, returns the oil 22 back to the screw 18 or to the screw 16, but also to the oil-lubricated bearing 70 of the shaft 14. Also provided in the area of ​​the bearing 70 is a nozzle 72, which is provided in the housing 20 in conjunction with the return line 68.

[0052] The cooler 74 is connected to the attachment 60, as described below in the Fig. 2 bis 4 is explained in more detail.

[0053] In the upper area of ​​the housing 20 (relative to the assembled state) there is a safety valve 76, through which excessive pressure in the housing 20 can be reduced.

[0054] Upstream of the minimum pressure valve 50 is a bypass line 78 leading to a relief valve 80. Air can be returned to the area of ​​the air inlet 28 via this relief valve 80, which is controlled by a connection to the air supply 32. A vent valve (not shown in detail) and also a nozzle (reducing the diameter of the supply line) can be provided in this area.

[0055] In addition, an oil level sensor 82 can be provided in the outer wall of the housing 20, approximately at the level of the line 34. This oil level sensor 82 can, for example, be an optical sensor and be designed and configured such that, based on the sensor signal, it can be detected whether the oil level is above the oil level sensor 82 during operation or whether the oil level sensor 82 is exposed and the oil level has therefore dropped accordingly.

[0056] In connection with this monitoring, an alarm unit can also be provided which issues or forwards a corresponding error message or warning message to the user of the system.

[0057] The function of the Fig. 1 The screw compressor 10 shown is as follows: Air is supplied via the air inlet 28 and passes through the check valve 30 to the screws 16, 18, where the air is compressed. The compressed air-oil mixture, which rises with a compression factor of between 5 and 16 after the screws 16 and 18 through the outlet line 34 via the riser pipe 36, is blown directly onto the temperature sensor 38.

[0058] The air, which still partially carries oil particles, is then guided via the holder 40 into the air de-oiling element 42 and, if the corresponding minimum pressure is reached, reaches the air outlet line 51.

[0059] The oil 22 in the housing 20 is kept at operating temperature via the oil filter 62 and, if necessary, via the heat exchanger 74.

[0060] If no cooling is required, the heat exchanger 74 is not used and is not switched on.

[0061] The corresponding activation is controlled by thermostat valve 68. After purification in the oil filter 64, oil is supplied via line 68 to screw 18 or screw 16, as well as to bearing 72. The screw 16 or screw 18 is supplied with oil 22 via return line 52, 58, where the purification of the oil 22 takes place in the air / oil separator 42.

[0062] The screws 16 and 18 of the screw compressor 10 are driven by the electric motor (not shown in detail), which transmits its torque via the shaft 14 to the screw 16, which in turn meshes with the shaft 18.

[0063] The relief valve 80 (not shown in detail) ensures that the high pressure that exists in the operating state, for example, on the output side of the screws 16, 18, cannot be trapped in the area of ​​the supply line 32, but rather that, particularly when the compressor starts up, a low inlet pressure, particularly atmospheric pressure, always exists in the area of ​​the supply line 32. Otherwise, when the compressor starts up, a very high pressure would initially develop on the output side of the screws 16 and 18, which would overload the drive motor.

[0064] In Fig. 2 The heat exchanger 74 is now shown in perspective view, which is placed directly on the housing 20.

[0065] In the assembled state, the heat exchanger 74 is placed and mounted directly on the housing 20, whereby the temperature of the oil 22 contained in the housing 20 can be regulated by means of the heat exchanger 74.

[0066] How to continue in Fig. 3 As shown, a double concentric radial projection 60 with an outer ring 60a and an inner ring 60b is provided for fastening the heat exchanger 74.

[0067] Inside the radial shoulder 60b, a receptacle 90 is provided, which serves to screw in a hollow screw 92.

[0068] The hollow screw 92 serves on the one hand to fix the oil cooler 74, but on the other hand, as can be seen from Fig. 4 shown, for returning the oil 22 passed through the oil cooler 74 and cooled back into the housing 20 through the hollow screw inner channel 92a. The area 98 between the concentric ring shoulders 60a and 60b is used to supply oil 22 to the oil cooler 74.

[0069] The oil cooler 74 is designed as a water-cooled heat exchanger (in particular, water-cooled with the addition of antifreeze). In another embodiment, an air-cooled heat exchanger can also be used.

[0070] The coolant is supplied via connections 94, 96 (see Fig. 2 and 4 ).

[0071] As in Fig. 4 As shown, the heat exchanger structure is designed as a lamellar structure or as a well-known and proven multi-plate structure. LIST OF REFERENCE SYMBOLS

[0072] 10 Screw compressor 12 Mounting flange 14 Input shaft 16 Screws 18 Screws 20 Housing 22 Oil 24 Inlet connection 26 Air filter 28 Air inlet 30 Valve insert 32 Air supply duct 34 Air outlet pipe 36 Riser pipe 38 Temperature sensor 40 Holder for an air separator 42 Air separator 44 Filter screen or known filter or oil separator devices 46 Air outlet opening 48 Check valve 50 Minimum pressure valve 51 Air outlet 52 Riser pipe 54 Filter and check valve 56 Nozzle 58 Oil return line 59 Oil drain plug 60 Extension 60a Outer ring 60b Inner ring 62 Oil filter 64 Oil filter inlet duct 66Thermostat valve 68Return line 70Bearing 72Nozzle 74Cooler, heat exchanger 76Safety valve 78Bypass line 80Relief valve 82Oil level sensor 90Receptacle 92Banjo bolt 92aBanjo bolt inner channel 94Connection 96Connection 98Area

Claims

1. A screw compressor (10) for a utility vehicle, having a housing (20), wherein the housing (20) is filled with oil (22), having at least one pair of compressor screws (16, 18) which are mounted in the housing (20) and which serve for compressing air which is fed to the screw compressor (10), wherein, in the assembled state, a heat exchanger (74) is mounted and installed directly onto the housing (20), by means of which heat exchanger the temperature of the oil (22) contained in the housing (20) can be regulated, wherein a thermostat valve (66) and a controlling and / or regulating apparatus is provided in the housing (20), by means of which controlling and / or regulating apparatus the oil temperature of the oil (22) contained in the housing (20) is kept at operating temperature via an oil filter (62) and optionally via the heat exchanger (74), wherein when cooling is not required, the oil is introduced directly from the screw compressor into the heat exchanger (74).

2. The screw compressor (10) as claimed in claim 1, characterized in that, for the fastening of the heat exchanger (74), a ring-shaped attachment piece (60) is provided on the housing (20).

3. The screw compressor (10) as claimed in claim 2, characterized in that two ring-shaped attachment pieces (60a, 60b) are provided on the housing (20).

4. The screw compressor (10) as claimed in claim 3, characterized in that the ring-shaped attachment pieces (60a, 60b) are arranged concentrically with respect to one another.

5. The screw compressor (10) as claimed in any of the preceding claims, characterized in that the housing has a receptacle for a screw (92) for the fastening of the heat exchanger (74).

6. The screw compressor (10) as claimed in claim 5 and either of claims 3 and 4, characterized in that the receptacle (90) for the screw (92) is received in the interior of the two ring-shaped attachment pieces (60a, 60b).

7. The screw compressor (10) as claimed in either of claims 5 and 6, characterized in that the screw (92) is a hollow screw.

8. The screw compressor (10) as claimed in claim 7, characterized in that the hollow screw (92) serves as a fluid channel for the oil (22) conducted to the heat exchanger (74) and / or the oil (22) conducted from the heat exchanger (74) back into the housing (20).

9. The screw compressor (10) as claimed in any of the preceding claims, characterized in that the heat exchanger (74) is water-cooled, in particular is cooled by means of a water-antifreeze mixture.

10. The screw compressor (10) as claimed in any of claims 1 to 8, characterized in that the heat exchanger (74) is air-cooled.