Screw Compressor for a Utility Vehicle

Abstract

A screw compressor for a utility vehicle has a rotor housing, in which screw rotors of the screw compressor are arranged, a housing cover, and an air outlet pipe arranged on an output side of the housing cover and having a riser. The air outlet pipe has at least one oil separator.

Description

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to a screw compressor for a utility vehicle.

Screw compressors for utility vehicles are already known from the prior art. Such screw compressors are used to provide the compressed air required for the brake system of the utility vehicle, for example.

In this context, in particular oil-filled compressors, in particular also screw compressors, are known, in the case of which it is necessary to regulate the oil temperature. This is generally realized by virtue of an external oil cooler being provided which is connected to the oil-filled compressor and to the oil circuit via a thermostat valve. Here, the oil cooler is a heat exchanger which has two mutually separate circuits, wherein the first circuit is provided for the hot liquid, that is to say the compressor oil, and the second circuit is provided for the cooling liquid. As cooling liquid, use may for example be made of air, water mixtures with an antifreeze, or another oil.

This oil cooler must then be connected to the compressor oil circuit by means of pipes or hoses, and the oil circuit must be safeguarded against leakage.

This external volume must furthermore be filled with oil, such that the total quantity of oil is also increased. The system inertia is thus increased. Furthermore, the oil cooler must be mechanically accommodated and fastened, either by means of brackets situated in the surroundings or by means of a separate bracket, which necessitates additional fastening means and also structural space.

U.S. Pat. No. 4,780,061 has already disclosed a screw compressor with an integrated oil cooling arrangement.

Furthermore, DE 37 17 493 A1 discloses a screw compressor installation which is arranged in a compact housing and which has an oil cooler on the electric motor of the screw compressor.

A generic screw compressor is already known for example from DE 10 2004 060 417 B4.

It is therefore the object of the present invention to advantageously further develop a screw compressor for a utility vehicle of the type mentioned in the introduction, in particular such that an initial oil separation can take place already before the fluid, in particular air, compressed by the screw compressor reaches the oil separator.

This object is achieved according to the invention by a screw compressor for a utility vehicle equipped with a rotor housing in which the screws of the screw compressor are arranged. An air outlet pipe is arranged at the outlet side of the housing cover and has a riser line, wherein the air outlet pipe has at least one oil separator.

The invention is based on the underlying concept, in the case of a screw compressor, of performing an initial oil separation already at the outlet side of the housing cover and of the screws which serve for the compression for example of the air or of some other fluid. This initial oil separation is realized not by way of a conventional oil separator but rather already by way of the air outlet pipe through which the compressed fluid, in particular the compressed air, is discharged out of the rotor housing or, after the compression by the screws, onward in the screw compressor.

By means of this oil separation that takes place already in the air outlet pipe, it is made possible for the efficiency of the oil separation to be considerably improved. In this way, it is also achieved that the oil separator may possibly be dimensioned and configured differently, because an initial oil separation takes place already upstream thereof.

Provision may furthermore be made for the oil separator means to have an oil return opening. Such an oil return opening may for example be an opening in a wall of the air outlet pipe, through which opening the oil that precipitates on the walls of the air outlet pipe can run out.

In particular, provision may be made for the oil return opening to connect the interior of the air outlet pipe to the oil sump. By means of this alone, a simple return of oil is achieved.

Provision may furthermore be made for the air outlet pipe to have an attachment piece by means of which the air outlet pipe is connected to the housing cover, wherein the oil return opening is arranged in the region of the attachment piece or adjacent to the attachment piece. It is thus made possible for the oil return opening to be arranged so as to relatively directly follow the outlet of the housing cover, that is to say at the location adjoined by the air outlet pipe. Any oil that has already precipitated there can thus be directly discharged out of the air outlet pipe.

The oil return opening may be formed by a simple bore. This permits simple assembly and at the same time also simple positioning of the oil return opening.

Provision may furthermore be made for the air outlet pipe to be at least partially of conical form. By means of a conical form of the air outlet pipe, it is made possible for oil particles to be separated out of the air, and for these to be prevented from exiting the air outlet pipe, owing to the action of gravitational force.

In particular, provision may be made for the riser line to be of conical form at an end side. By means of such a conical widening of the riser line, it is made possible for the effect of separating oil particles and droplets out of the air under the action of gravitational force to be improved. The oil particles separated out in this way fall back into the air outlet pipe and collect in the region adjacent to the attachment piece of the air outlet pipe, and there, can flow via the oil return opening back into the oil sump.

Further details and advantages of the invention will now be discussed in more detail on the basis of an exemplary embodiment illustrated in the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic sectional drawing through a screw compressor according to the invention;

FIG. 2 shows a perspective detail view of the rotor housing of the screw compressor, with air outlet pipe of the screw compressor, as per FIG. 1, and

FIG. 3 shows a perspective sectional drawing through the air outlet pipe as per FIG. 2.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows, in a schematic sectional illustration, a screw compressor 10 in the context of an exemplary embodiment of the present invention.

The screw compressor 10 has a fastening flange 12 for the mechanical fastening of the screw compressor 10 to an electric motor (not shown in any more detail here).

What is shown, however, is the input shaft 14, by which the torque from the electric motor is transmitted to one of the two screws 16 and 18, specifically the screw 16.

The screw 18 meshes with the screw 16 and is driven by means of the latter.

The screw compressor 10 has a housing 20 in which the main components of the screw compressor 10 are accommodated.

The housing 20 is filled with oil 22.

At the air inlet side, an inlet connector 24 is provided on the housing 20 of the screw compressor 10. The inlet connector 24 is in this case designed such that an air filter 26 is arranged at said inlet connector. Furthermore, an air inlet 28 is provided radially on the air inlet connector 24.

In the region between the inlet connector 24 and the point at which the inlet connector 24 joins to the housing 20, there is provided a spring-loaded valve insert 30, which is designed here as an axial seal.

This valve insert 30 serves as a check valve.

Downstream of the valve insert 30, there is provided an air feed channel 32 which feeds the air to the two screws 16, 18.

At the outlet side of the two screws 16, 18, there is provided an air outlet pipe 34 with a riser line 36.

In the region of the end of the riser line 36, there is provided a temperature sensor 38 by means of which the oil temperature can be monitored.

Also provided in the air outlet region is a holder 40 for an air deoiling element 42.

In the assembled state, the holder 40 for the air deoiling element has the air deoiling element 42 in the region facing toward the base (as also shown in FIG. 1).

Also provided, in the interior of the air deoiling element 42, is a corresponding filter screen or known filter and oil separation devices 44, which will not be specified in any more detail.

In the central upper region in relation to the assembled and operationally ready state (that is to say as shown in FIG. 1), the holder for the air deoiling element 42 has an air outlet opening 46 which leads to a check valve 48 and a minimum pressure valve 50. The check valve 48 and the minimum pressure valve 50 may also be formed in one common combined valve.

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

The air outlet 51 is generally connected to correspondingly known compressed-air consumers.

In order for the oil 22 that is situated and separated off in the air deoiling element 42 to be returned again 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 deoiling element 42 at the transition into the housing 20.

A nozzle 56 is provided, downstream of the filter and check valve 54, in a housing bore. The oil return line 58 leads back into approximately the central region of the screw 16 or of the screw 18 in order to feed oil 22 thereto again.

An oil drain screw 59 is provided in the base region, in the assembled state, of the housing 20. By means of the oil drain screw 59, a corresponding oil outflow opening can be opened, via which the oil 22 can be drained.

Also provided in the lower region of the housing 20 is the attachment piece 60 to which the oil filter 62 is fastened. Via an oil filter inlet channel 64, which is arranged in the housing 20, the oil 22 is conducted firstly to a thermostat valve 66.

Instead of the thermostat valve 66, it is possible for an open-loop and/or closed-loop control device to be provided by means of which the oil temperature of the oil 22 situated in the housing 20 can be monitored and set to a setpoint value.

Downstream of the thermostat valve 66, there is then the oil inlet of the oil filter 62, which, via a central return line 68, conducts the oil 22 back to the screw 18 or to the screw 16 again, and also to the oil-lubricated bearing 70 of the shaft 14. Also provided in the region of the bearing 70 is a nozzle 72, which is provided in the housing 20 in conjunction with the return line 68.

The cooler 74 is connected to the attachment piece 60, as will be discussed in more detail below in FIGS. 2 to 4.

In the upper region of the housing 20 (in relation to the assembled state), there is situated a safety valve 76, by means of which an excessively high pressure in the housing 20 can be dissipated.

Upstream of the minimum pressure valve 50, there is situated a bypass line 78, which leads to a relief valve 80. Via said relief valve 80, which is activated by means of a connection to the air feed 32, air can be returned into the region of the air inlet 28. In this region, there may be provided a ventilation valve (not shown in any more detail) and also a nozzle (diameter constriction of the feeding line).

Furthermore, approximately at the level of the line 34, an oil level sensor 82 may be provided in the outer wall of the housing 20. Said oil level sensor 82 may for example be an optical sensor, and may be designed and configured such that, on the basis of the sensor signal, it can be identified whether the oil level during operation is above the oil level sensor 82 or whether the oil level sensor 82 is exposed, and thus the oil level has correspondingly fallen.

In conjunction with this monitoring, it is also possible for an alarm unit to be provided which outputs or transmits a corresponding error message or warning message to the user of the system.

The function of the screw compressor 10 shown in FIG. 1 is as follows.

Air is fed via the air inlet 28 and passes via the check valve 30 to the screws 16, 18, where the air is compressed. The compressed air-oil mixture, which, having been compressed by a factor of between 5 and 16 downstream of the screws 16 and 18, rises through the outlet line 34 via the riser pipe 36, is blown directly onto the temperature sensor 38.

The air, which still partially carries oil particles, is then conducted via the holder 40 into the air deoiling element 42 and, if the corresponding minimum pressure is attained, passes into the air outlet line 51.

The oil 22 situated in the housing 20 is kept at operating temperature via the oil filter 62 and possibly via the heat exchanger 74.

If no cooling is necessary, the heat exchanger 74 is not used and is also not activated.

The corresponding activation is performed by means of the thermostat valve 66. After purification in the oil filter 62, oil is fed via the line 68 to the screw 18 or to the screw 16, and also to the bearing 70. The screw 16 or the screw 18 is supplied with oil 22 via the return line 52, 58, and the purification of the oil 22 takes place here in the air deoiling element 42.

By means of the electric motor (not shown in any more detail), which transmits its torque via the shaft 14 to the screw 16, which in turn meshes with the screw 18, the screws 16 and 18 of the screw compressor 10 are driven.

By means of the relief valve 80 (not shown in any more detail), it is ensured that the high pressure that prevails for example at the outlet side of the screws 16, 18 in the operational state cannot be enclosed in the region of the feed line 32, and that, instead, in particular during the start-up of the compressor, there is always a low inlet pressure, in particular atmospheric pressure, prevailing in the region of the feed line 32. Otherwise, upon a start-up of the compressor, a very high pressure would initially be generated at the outlet side of the screws 16 and 18, which would overload the drive motor.

FIG. 2 shows, in a perspective view, the housing cover 20a of the screw compressor 10 as shown in FIG. 1.

The housing cover 20a has an outlet which is adjoined by the air outlet pipe 34.

Here, the air outlet pipe 34 has an attachment piece 34a, by means of which the air outlet pipe 34 is connected to the housing cover 20a.

The air outlet pipe 34 furthermore has a riser line 36.

Here, the riser line 36 is of conically widened form, specifically in the end-side region 36a.

The air outlet pipe 34 furthermore has an oil return opening 100 in the region of its attachment piece 34a.

Here, the oil return opening 100 is formed as a bore.

The oil return opening 100 connects the interior of the air outlet pipe 34 to the oil sump 22a.

By means of the conical widening and the oil return opening 100, the air outlet pipe 34 has, altogether, an oil separator which serves for the initial oil separation even before the air compressed by the screw compressor 10 is conducted through the oil separator.

Here, the oil separation occurs in that, owing to the conical widening and the reduction of the flow speed that is also achieved as a result in this region, oil particles situated in the air stream can fall back again owing to the action of gravitational force, can precipitate on the walls in the interior of the air outlet pipe 34, and can then flow back through the oil return opening 100 into the oil sump 22a.

FIG. 3 shows a perspective sectional drawing through the air outlet pipe as per FIG. 2.

LIST OF REFERENCE DESIGNATIONS

• 10 Screw compressor
• 12 Fastening flange
• 14 Input shaft
• 16 Screws
• 18 Screws
• 20 Housing
• 20a Housing cover
• 22a Oil sump
• 22 Oil
• 24 Inlet connector
• 26 Air filter
• 28 Air inlet
• 30 Valve insert
• 32 Air feed channel
• 34 Air outlet pipe
• 34a Attachment piece
• 36 Riser line
• 36a End-side region
• 38 Temperature sensor
• 40 Holder for an air deoiling element
• 42 Air deoiling element
• 44 Filter screen or known filter or oil separation devices
• 46 Air outlet opening
• 48 Check valve
• 50 Minimum pressure valve
• 51 Air outlet
• 52 Riser line
• 54 Filter and check valve
• 56 Nozzle
• 58 Oil return line
• 59 Oil drain screw
• 60 Attachment piece
• 60a Outer ring
• 60b Inner ring
• 62 Oil filter
• 64 Oil filter inlet channel
• 66 Thermostat valve
• 68 Return line
• 70 Bearing
• 72 Nozzle
• 76 Safety valve
• 78 Bypass line
• 80 Relief valve
• 82 Oil level sensor
• 100 Oil return opening

Claims

1-7. (canceled)

8. A screw compressor for a utility vehicle, comprising:

a housing cover in which screws of the screw compressor are arranged; and

an air outlet pipe which is arranged at an outlet side of the housing cover and includes a riser line, wherein

the air outlet pipe has at least one oil separator.

9. The screw compressor as claimed in claim 8, wherein

the oil separator comprises an oil return opening.

10. The screw compressor as claimed in claim 9, wherein

the oil return opening connects an interior of the air outlet pipe to the oil sump.

11. The screw compressor as claimed in claim 10, wherein

the air outlet pipe has an attachment piece by which the air outlet pipe is connected to the housing cover, and

the oil return opening is arranged in a region of the attachment piece or adjacent to the attachment piece.

12. The screw compressor as claimed in claim 9, wherein

the oil return opening is a bore.

13. The screw compressor as claimed in claim 10, wherein

the air outlet pipe is at least partially of conical form.

14. The screw compressor as claimed in claim 13, wherein

the riser line is of conical form at an end side.