Piston Compressor with a Closing Device for the Outlet Line

Abstract

A piston compressor for compressing a gas, which optionally can be disconnected from a drive device by a clutch, has an inlet valve, which is arranged between an inlet line for gas to be compressed and a compression chamber of the piston compressor, and an outlet valve, which is arranged between the compression chamber of the piston compressor and an outlet line for compressed gas. The piston compressor includes a closing device which closes the outlet line with respect to the compression chamber.

Claims

1. A piston compressor for compressing a gas, comprising: an inlet valve, which is arranged between an inlet line for gas for compression and a compression chamber of the piston compressor; an outlet valve, which is arranged between the compression chamber of the piston compressor and an outlet line for compressed gas; a separate closing device, which is arranged downstream of the outlet valve in a flow direction of the gas by which the outlet line is closable with respect to the compression chamber; a clutch by which the piston compressor is separable from a drive device; and a control device which has a signal connection both to the clutch and to the separate closing device; wherein a switchable valve device forms the closing device, and the control device is configured to switch the switchable valve device into a closed position when the clutch between the piston compressor and the drive device is open.

2. The piston compressor as claimed in claim 1, wherein the switchable valve device closes the outlet line in a manner dependent on the pressure difference prevailing at the two sides of the switchable valve device.

3. The piston compressor as claimed in claim 2, wherein the switchable valve device is configured so as to switch into a closed position simultaneously with the opening of the clutch.

4. The piston compressor as claimed in claim 1, wherein a 2/2-way valve forms the switchable valve device.

5. The piston compressor as claimed in claim 1, wherein the switchable valve device is configured so as to switch into a closed position simultaneously with the opening of the clutch.

6. A method for operating a piston compressor for compressing a gas, the piston compressor having an inlet valve arranged between an inlet line for gas for compression and a compression chamber, and having an outlet valve arranged between the compression chamber and an outlet line for compressed gas, the method comprising the acts of: determining when a clutch arranged between the piston compressor and a drive device is open; and switching, via a control device having a signal connection both to the clutch and to a switchable valve device arranged downstream of the outlet valve in a flow direction of the gas, the switchable valve device into a closed position when the clutch between the piston compressor and the drive device is open.

7. The method for operating a piston compressor as claimed in claim 6, wherein the control device switches the switchable valve device into an open position when the clutch between the piston compressor and the drive device is closed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1 is a schematic illustration of an exemplary piston compressor of the prior art.

[0024] FIG. 2 is an illustration of an exemplary outlet valve as it is used in piston compressors in the prior art.

[0025] FIG. 3 is a schematic illustration of a first exemplary embodiment of a piston compressor according to the invention, in which a shut-off valve forms the closing device.

[0026] FIG. 4 is a schematic illustration of a second exemplary embodiment of a piston compressor according to the invention, in which a switchable valve device forms the closing device.

DETAILED DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 is a schematic illustration of an exemplary piston compressor 10 such as is known in the prior art. The crankshaft 11 of the piston compressor 10 is connected via a clutch 3 to a drive device (not illustrated, in this case an internal combustion engine) and is selectively separable from said drive device by way of the clutch 3. When the clutch 3 is open, it is thus the case that no torque is transmitted to the crankshaft 11 of the piston compressor 10, such that the crankshaft 11 is stationary during the separation of the piston compressor 10 from the drive device.

[0028] The crankshaft 11 is connected to a connecting rod 12 which is mounted eccentrically on said crankshaft, on which connecting rod there is mounted a piston 13. The piston 13 is mounted in axially movable fashion in a cylinder 14 of the piston compressor 10. The crank drive 15, which has at least one crankshaft 11, a connecting rod 12 and a piston 13, is arranged in a crankcase 16, which is fixedly connected to the cylinder 14. By means of a rotational movement of the crankshaft 11, the piston 13 is moved by the connecting rod 12 in the cylinder 14 so as to perform a reciprocating movement.

[0029] Above the piston 13, the cylinder 14 is closed off by a valve plate 20. Thus, the cylinder 14, the piston 13 and the valve plate 20 define the compression chamber 17 in the cylinder 14. On the valve plate 20, there is arranged an inlet valve 21 which is arranged between an inlet line 22 and the compression chamber 17. The inlet line 22 is part of an inlet system 23 which draws fresh air from the surroundings through a filter (not illustrated) and supplies said fresh air via the inlet line 22 through the cylinder head (not illustrated) to the compression chamber 17. The cylinder head is arranged above the valve plate 20 and has a cylinder head volume 24 which is connected via the inlet valve 21 to the compression chamber 17. Here, the inlet valve 21 is designed as a shut-off valve which allows fresh air to be drawn into the compression chamber 17 but prevents a backflow of the air that has been drawn into the compression chamber 17 via the inlet line 22.

[0030] Also arranged on the valve plate 20 is an outlet valve 26, which is arranged between the compression chamber 17 and an outlet line 27. Via the outlet line 27, compressed gas, in this case air, is supplied to a compressed-air accumulator (not illustrated here). Here, the outlet valve 26, which is likewise designed as a shut-off valve, prevents a backflow of compressed air from the outlet line 27 into the compression chamber 17.

[0031] FIG. 2 is an illustration of an exemplary outlet valve 26 such as is commonly used in piston compressors 10 in the prior art. The outlet valve 26 is arranged on the valve plate 20 of the piston compressor 10 above the compression chamber 17. The valve plate 20 has an outlet opening 28 which connects the compression chamber 17 to a cylinder head volume 27a arranged in the valve plate 20 and cylinder head of the piston compressor 10, which cylinder head volume is connected to the outlet line 27.

[0032] The outlet valve 26 has, as a valve body, a valve tongue 26a which, above a predetermined pressure difference between the compression chamber 17 and the outlet line 27, lifts off from the valve seat 26b and permits a throughflow of air from the compression chamber 17 into the outlet line 27. The outlet valve 26 furthermore has an abutment element 26c which is arranged above the outlet opening 28 and against which the valve tongue 26a bears in the open state. As soon as the valve tongue 26a lifts off from the valve seat 26b, the pressurized air can flow from the compression chamber 17 through the lateral open regions past the valve tongue 26a and the abutment element 26c into the outlet line 27.

[0033] If contaminants from the compression chamber 17 or from the cylinder head volume 27a, which contaminants detach for example from coatings that are formed by residues in the throughflowing air from the hot top side of the piston 13, from the valve plate 20 or from the cylinder head volume 27a, pass between the valve tongue 26a and the valve seat 26b, there is the risk that the outlet valve 26 no longer completely closes. In this case, compressed air can flow from the outlet line 27 back into the compression chamber 17 as soon as the pressure in the compression chamber 17 is lower than the pressure in the outlet line 27. In the case of a 12.5 bar compressed-air system of a commercial vehicle, the compression chamber 17 of the piston compressor 10 may for example be charged with a pressure of up to 6 bar by the air flowing back into it. If the piston compressor 10 is then connected to the drive device again, the piston compressor 10 generates an internal pressure of up to 60 bar during the first stroke. If the compression chamber 17 withstands this enormous internal pressure, the torque that is generated here at the crankshaft 11 is normally far too high for the clutch 3, such that the latter slips, overheats, and is subject to excessively rapid wear.

[0034] FIG. 3 is a schematic illustration of a first exemplary embodiment of a piston compressor 10 according to the invention. The construction of the piston compressor 10 in FIG. 3 corresponds substantially to the construction of the piston compressor 10 illustrated in FIG. 1 and described with regard thereto, such that identical elements of the piston compressors 10 are denoted by the same reference designations. Below, only the differences between the piston compressor 10 from FIG. 3 and the piston compressor 10 from FIG. 1 will be discussed.

[0035] The piston compressor 10 illustrated in FIG. 3 has a closing device in the form of a shut-off valve, which is arranged separately downstream of the outlet valve 26 in the flow direction. The shut-off valve is designed as a check valve 31 with preloaded valve body. This check valve 31 opens when the pressure of the air which is discharged by the piston compressor 10, and which flows out of the compression chamber 17 through the outlet valve 26, is higher, by a magnitude, than the pressure of the air that is situated in the outlet line 27. The magnitude of the pressure difference is at least so great that the preload of the check valve 31 is overcome, in order that the check valve 31 opens.

[0036] While the piston compressor 10 is at a standstill, no compressed air is situated in the compression chamber 17. Even if the outlet valve 26 does not reliably close, no compressed air can flow from the pressurized outlet line 27 back into the compression chamber 17, because the outlet line is closed off with respect to the compression chamber 17 by the check valve 31. During compression operation of the piston compressor 10, compressed air, which is at a higher pressure than the compressed air in the outlet line 27, is conveyed through the outlet valve 26. Owing to the pressure difference between the air discharged from the compression chamber 17 and the pressure in the outlet line 27, the check valve 31 opens, and the compressed air is supplied to the outlet line 27 and thus to the compressed-air system.

[0037] FIG. 4 is a schematic illustration of a second exemplary embodiment of a piston compressor 10 according to the invention. The construction of the piston compressor 10 in FIG. 4 also substantially corresponds to the construction of the piston compressor 10 illustrated in FIG. 1 and described with regard thereto, such that identical elements of the piston compressors 10 are denoted by the same reference designations. Only the differences between the piston compressor 10 from FIG. 4 and the piston compressor 10 from FIG. 1 will be discussed below.

[0038] The piston compressor 10 illustrated in FIG. 4 has a closing device in the form of a switchable valve device 32 which is arranged separately downstream of the outlet valve 26 in the flow direction. The switchable valve device 32 is, in the exemplary embodiment, designed as a 2/2-way valve, which is switchable from a closed position into the illustrated open position. The switchable valve device 32 is connected via a control line 32a to a control device 33, which opens and closes the switchable valve device 32 by means of switching signals transmitted via the control line 32a. In the exemplary embodiment, the control device 33 is furthermore connected via a control line 3a to the clutch 3, wherein signals regarding the switching position of the clutch 3 are transmitted by the control line 3a to the control device 33. The control device 33 is optionally connected via a control line 33a to the controller of the compressed-air system.

[0039] While the piston compressor 10 is at a standstillthe clutch between the drive device and the piston compressor 10 is openthe switchable valve device 32 is switched into the closed position. Even if the outlet valve 26 does not reliably close, no compressed air can flow from the pressurized outlet line 27 back into the compression chamber 17, because the outlet line 27 is closed off with respect to the compression chamber 17 when the switchable valve device 32 is in the closed position. Upon the closure of the clutch 3 at the start of compression operation of the piston compressor 10, the switchable valve device 32 is switched into the open position shown in FIG. 4. In this way, compressed air which is at a higher pressure than the compressed air in the outlet line 27 can be conveyed through the outlet valve 26, and through the switchable valve device 32 which is situated in the open position, into the outlet line 27, and supplied to the compressed-air system. Optionally, in a variant in which the control device 33 is connected to the controller of the compressed-air system, the opening of the clutch 3 may take place simultaneously with the switching of the switchable valve device 32 into the closed position, and the closing of the clutch 3 may take place simultaneously with the switching of the switchable valve device 32 into the open position.

LIST OF REFERENCE DESIGNATIONS

[0040] 3 Clutch [0041] 3a Control line [0042] 10 Piston compressor [0043] 11 Crankshaft [0044] 12 Connecting rod [0045] 13 Piston [0046] 14 Cylinder [0047] 15 Crank drive [0048] 16 Crankcase [0049] 17 Compression chamber [0050] 20 Valve plate [0051] 21 Inlet valve [0052] 22 Inlet line [0053] 23 Inlet system [0054] 24 Cylinder head volume (inlet) [0055] 26 Outlet valve [0056] 26a Valve tongue [0057] 26b Valve seat [0058] 26c Abutment element [0059] 27 Outlet line [0060] 28 Outlet opening [0061] 31 Shut-off valve [0062] 32 Switchable valve device [0063] 32a Control line [0064] 33 Control device [0065] 33a Control line

[0066] The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.