Abstract
A piston compressor is provided for compressing a gas, which optionally can be disconnected from a drive device by way of a clutch. The piston compressor 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 has a venting device, by which compressed gas can be led out of the compression chamber.
Claims
1. A piston compressor for compressing a gas, which compression is optionally separable from a drive device by way of a clutch, comprising: an inlet valve, which is arranged between an inlet line for the gas to be compressed 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; and a venting device, through which compressed gas, which passes from the outlet line back into the compression chamber during a separation of the piston compressor from the drive device, is able to be discharged from the compression chamber.
2. The piston compressor as claimed in claim 1, wherein the compressed gas is able to be discharged from the compression chamber into a region at ambient pressure, which is formed by an environment itself, a gas chamber connected to an inlet system, or an interior of the crankcase.
3. The piston compressor as claimed in claim 1, wherein a switchable valve device forms the venting device.
4. The piston compressor as claimed in claim 1, wherein a check valve forms the venting device.
5. The piston compressor as claimed in claim 1, wherein the inlet valve forms the venting device, the inlet valve is configured such that a connection between the inlet line and the compression chamber is closable thereby only from a predetermined pressure in the compression chamber, and the predetermined pressure is at least 0.1 bar higher than the pressure in the inlet line.
6. The piston compressor as claimed in claim 5, wherein the predetermined pressure is at least 0.2 bar higher than the pressure in the inlet line.
7. The piston compressor as claim in claim 5, wherein the predetermined pressure is at least 0.5 bar higher than the pressure in the inlet line.
8. The piston compressor as claimed in claim 5, wherein the inlet valve has a valve seat formed in a concave manner and a valve tongue formed in a substantially planar manner such that the valve tongue bears in a sealing manner against the valve seat only after an elastic deformation brought about by the pressure in the compression chamber.
9. The piston compressor as claimed in claim 5, wherein the inlet valve has a valve seat formed in a planar manner and a valve tongue formed in a curved manner, such that the valve tongue bears in a sealing manner against the valve seat only after an elastic deformation brought about by the pressure in the compression chamber.
10. The piston compressor as claimed in claim 1, wherein a venting duct forms the venting device.
11. The piston compressor as claimed in claim 10, wherein at least one end of the venting duct is arranged in a valve plate or in a cylinder wall.
12. The piston compressor as claimed in claim 10, wherein a check valve or a shut-off valve is arranged in the venting duct.
13. The piston compressor as claimed in claim 11, wherein a check valve or a shut-off valve is arranged in the venting duct.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 is a schematic illustration of an example of a prior art piston compressor.
[0031] FIG. 2 is an illustration of an example of an outlet valve as is used in piston compressors in the prior art.
[0032] FIG. 3 is a schematic illustration of a first exemplary embodiment of a piston compressor according to the invention, in which the venting device has a switchable valve device.
[0033] FIG. 4 is a schematic illustration of a second exemplary embodiment of a piston compressor according to the invention, in which the venting device has a switchable valve device.
[0034] FIG. 5 is a schematic illustration of a third exemplary embodiment of a piston compressor according to the invention, in which the venting device has a check valve.
[0035] FIG. 6 is a schematic illustration of a fourth exemplary embodiment of a piston compressor according to the invention, in which the venting device has a venting duct.
[0036] FIG. 7 is a schematic illustration of a fifth exemplary embodiment of a piston compressor according to the invention, in which the venting device has a venting duct with a shut-off valve.
[0037] FIG. 8 is a schematic illustration of a sixth exemplary embodiment of a piston compressor according to the invention, in which the venting device has a venting duct.
[0038] FIG. 9 is a schematic illustration of a seventh exemplary embodiment of a piston compressor according to the invention, in which the venting device has a venting duct.
[0039] FIG. 10 is a schematic illustration of an eighth exemplary embodiment of a piston compressor according to the invention, in which the venting device has a venting duct.
[0040] FIG. 11 is an illustration of a detail of a ninth exemplary embodiment of a piston compressor according to the invention, in which the inlet valve forms the venting device.
DETAILED DESCRIPTION OF THE DRAWINGS
[0041] FIG. 1 shows a schematic illustration of an example of a piston compressor 10 as is known from the prior art. The crankshaft 11 of the piston compressor 10 is connected to a drive device (not illustrated, in this case a combustion engine) via a clutch 3 and is separable selectively from this drive device by way of the clutch 3. Therefore, with the clutch 3 open, no torque is transmitted to the crankshaft 11 of the piston compressor 10, and so the crankshaft 11 is stationary during the separation of the piston compressor 10 from the drive device.
[0042] The crankshaft 11 is connected to a connecting rod 12, mounted eccentrically thereon, on which a piston 13 is mounted. The piston 13 is mounted in an axially movable manner in a cylinder 14 of the piston compressor 10. The crank drive 15 having at least one crankshaft 11, one connecting rod 12 and one piston 13 is arranged in a crankcase 16 which is firmly connected to the cylinder 14. As a result of a rotary movement of the crankshaft 11, the piston 13 is moved in the cylinder 14 by the connecting rod 12 such that it executes a stroke movement.
[0043] Above the piston 13, the cylinder 14 is closed 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. Arranged on the valve plate 20 is 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 in fresh air from the environment through a filter (not illustrated) and feeds it to the compression chamber 17 via the inlet line 22 through the cylinder head (not illustrated). The cylinder head is arranged above the valve plate 20 and has a cylinder-head volume 24 which is connected to the compression chamber 17 via the inlet valve 21. The inlet valve 21 is embodied in this case as a shut-off valve, which allows fresh air to be drawn into the compression chamber 17 but prevents the air drawn into the compression chamber 17 via the inlet line 22 from flowing back.
[0044] 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 fed to a compressed-air reservoir (not illustrated here). In this case, the outlet valve 26, which is likewise embodied as a shut-off valve, prevents compressed air from flowing back into the compression chamber 17 from the outlet line 27.
[0045] FIG. 2 shows an illustration of an example of an outlet valve 26 as is frequently 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, said cylinder-head volume 27a forming part of the outlet line 27.
[0046] The outlet valve 26 has, as valve body, a valve tongue 26a, which detaches from the valve seat 26b from a predetermined pressure difference between the compression chamber 17 and the outlet line 27 and allows air to flow through from the compression chamber 17 into the outlet line 27. The outlet valve 26 also has an abutment element 26c, arranged above the outlet opening 28, against which the valve tongue 26a bears in the open state. As soon as the valve tongue 26a detaches from the valve seat 26b, the pressurized air can flow out of the compression chamber 17, through the lateral open regions past the valve tongue 26a and the abutment element 26c, and into the outlet line 27.
[0047] If contaminants from the compression chamber 17 or from the cylinder-head volume 27a, which are detached for example by deposits formed by residues in the air flowing through 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 a risk of the outlet valve 26 no longer closing fully. In this case, compressed air can flow back into the compression chamber 17 from the outlet line 27 as soon as the pressure in the compression chamber 17 drops below 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 can be subjected to a pressure of up to 6 bar for example by the air flowing back thereto. If the piston compressor 10 is then connected to the drive device again, the piston compressor 10 generates an internal pressure of about 60 bar during the first stroke. If the compression chamber 17 withstands this enormous internal pressure, the resultant torque at the crankshaft 11 is usually much too high for the clutch 3 and so the latter slips, overheats and wears inadmissibly quickly.
[0048] FIG. 3 shows a schematic illustration of a first exemplary embodiment of a piston compressor 10 according to the invention. The structure of the piston compressor 10 in FIG. 3 corresponds largely to the structure of the piston compressor 10 illustrated in FIG. 1 and described in that regard, and so identical elements of the piston compressors 10 are denoted by identical reference signs. In the following text, only the differences of the piston compressor 10 in FIG. 3 from the piston compressor 10 in FIG. 1 are explained.
[0049] The piston compressor 10 illustrated in FIG. 3 has a venting device in the form of a 2/2-way valve 31, which is arranged between the compression chamber 17 and the inlet system 23. The 2/2-way valve is a switchable valve device. In the exemplary embodiment in FIG. 3, the control line 31a of the 2/2-way valve 31 is connected in terms of signaling to the controller of the clutch 3. If the clutch 3 is opened and the piston compressor 10 is thus no longer driven, the 2/2-way valve 31 is switched from the illustrated closed position into an open position in order to establish a connection, through which air is able to flow, between the compression chamber 17 and the inlet system 23.
[0050] If, while the piston compressor 10 is inoperative, for example in the case of an outlet valve 26 that no longer closes in a leaktight manner, compressed air now passes into the compression chamber 17, it is possible for pressure equalization with the inlet line 22 to take place by way of the open 2/2-way valve 31. Thus, no pressure buildup can take place in the compression chamber 17, which could result in damage to the piston compressor 10 and/or the clutch 3, in particular during the first compression stroke of the piston compressor 10 when the latter is restarted.
[0051] FIG. 4 shows a schematic illustration of a second exemplary embodiment of a piston compressor 10 according to the invention. The structure of the piston compressor 10 in FIG. 4 also corresponds largely to the structure of the piston compressor 10 illustrated in FIG. 1 and described in that regard, and so identical elements of the piston compressors 10 are denoted by identical reference signs. In the following text, only the differences of the piston compressor 10 in FIG. 4 from the piston compressor 10 in FIG. 1 are explained.
[0052] The piston compressor 10 illustrated in FIG. 4 has a venting device in the form of an unblockable check valve 32, which also serves at the same time as an inlet valve. Thus, the unblockable check valve 32 is arranged between the compression chamber 17 and the inlet system 23. While fresh air is being drawn into the compression chamber 17 from the inlet line 22, the unblockable check valve 32 opens automatically on account of the pressure difference prevailing there. The unblockable check valve 32 is also a switchable valve device, which, in addition to automatically opening when drawing in fresh air, is also switchable into an open position by means of a control signal. In the exemplary embodiment in FIG. 4, the control line 32a of the unblockable check valve 32 is connected in terms of signaling to a control device (not illustrated). Depending on at least one predetermined parameter, for example the pressure in the compression chamber 17, it is thus possible for the unblockable check valve 32 to be opened in order to establish a connection between the compression chamber 17 and the inlet line 22.
[0053] If, while the piston compressor 10 is inoperative, for example in the case of an outlet valve 26 that no longer closes in a leaktight manner, compressed air now passes into the compression chamber 17, the unblockable check valve 32 can be opened in order to allow pressure equalization with the inlet line 22. Thus, no pressure buildup can take place in the compression chamber 17, which could result in damage to the piston compressor 10 and/or the clutch 3, in particular during the first compression stroke of the piston compressor 10 when the latter is restarted.
[0054] When the piston compressor 10 is started again, the unblockable check valve 32 is switched by the control device back into the working position, in which it automatically opens, while fresh air is being drawn into the compression chamber 17 from the inlet line 22, on account of the pressure difference prevailing there.
[0055] FIG. 5 shows a schematic illustration of a third exemplary embodiment of a piston compressor 10 according to the invention. The structure of the piston compressor 10 in FIG. 5 also corresponds largely to the structure of the piston compressor 10 illustrated in FIG. 1 and described in that regard, and so identical elements of the piston compressors 10 are denoted by identical reference signs. In the following text, only the differences of the piston compressor 10 in FIG. 5 from the piston compressor 10 in FIG. 1 are explained.
[0056] The piston compressor 10 illustrated in FIG. 5 has a venting device in the form of a check valve 33, which is arranged between the compression chamber 17 and the inlet system 23. The check valve 33 arranged in addition to the inlet valve 21 between the compression chamber 17 and the inlet system 23 blocks in the opposite direction to the inlet valve 21, and so it is closed while fresh air is being drawn into the compression chamber 17 and during compression of the piston compressor 10 in normal operation.
[0057] If, in the embodiment shown in FIG. 5, while the piston compressor 10 is inoperative, for example in the case of an outlet valve 26 that no longer closes in a leaktight manner, compressed air passes into the compression chamber 17, first of all a pressure buildup in the compression chamber 17 takes place here. The pressure that is established in the process does not reach a higher value than during a compression stroke, and so initially no venting of the compression chamber 17 is necessary. It is only during the first compression stroke of the piston compressor 10 after it has been restarted that a much higher pressure arises on account of the precompressed air in the compression chamber 17, it being possible for this much higher pressure to result in damage to the piston compressor 10 and/or clutch 3. Therefore, the check valve 33 is designed such that it opens a connection between the compression chamber 17 and the inlet line 21 with a sufficiently large cross section in order to discharge air from the compression chamber 17 as soon as the pressure in the compression chamber 17 exceeds a critical value. In the exemplary piston compressor 10 for a commercial vehicle, the peak pressure in the compression chamber during normal operation is between about 16 and 19 bar. An exemplary check valve 33 is therefore embodied such that it opens for example at a pressure of 20 bar in the compression chamber 17 and thus discharges compressed air out of the compression chamber 17.
[0058] FIG. 6 shows a schematic illustration of a fourth exemplary embodiment of a piston compressor 10 according to the invention. The structure of the piston compressor 10 in FIG. 6 also corresponds largely to the structure of the piston compressor 10 illustrated in FIG. 1 and described in that regard, and so identical elements of the piston compressors 10 are denoted by identical reference signs. In the following text, only the differences of the piston compressor 10 in FIG. 6 from the piston compressor 10 in FIG. 1 are explained.
[0059] The piston compressor 10 illustrated in FIG. 6 has a venting device in the form of a venting duct 34, which is arranged between the compression chamber 17 and the inlet system 23. The venting duct 34 establishes a connection, through which air is able to flow, between the compression chamber 17 and the inlet system 23, such that, while the piston compressor is inoperative, a pressure which is significantly greater than ambient pressure cannot build up in the compression chamber 17.
[0060] In the embodiment shown in FIG. 6, the venting duct 34 is arranged in the region of the valve plate 20 on the top side of the cylinder 14, such that, by way of the venting duct 34, continuous pressure equalization with the inlet line 32 of the piston compressor 10 takes place. If, while the piston compressor 10 is inoperative, compressed air passes into the compression chamber 17 from the outlet line 27, pressure equalization with the inlet line 22 takes place by way of the venting duct 34, with the result that a pressure buildup in the compression chamber 17 cannot occur. A drawback of such a venting duct 34, however, is that it is also open during a compression stroke of the piston compressor 10 and air to be compressed in this phase escapes from the compression chamber 17. This reduces the efficiency of the piston compressor 10. The venting duct 34 is therefore designed such that it has only a small cross section in order to allow sufficient pressure equalization with the inlet system 23 while the piston compressor 10 is inoperative, but has a throttle action at high pressures in order to limit the volume flow of the discharged air.
[0061] FIG. 7 shows a schematic illustration of a sixth exemplary embodiment of a piston compressor 10 according to the invention. The structure of the piston compressor 10 in FIG. 7 corresponds largely to the structure of the piston compressor 10 illustrated in FIG. 6 and described in that regard, and so identical elements of the piston compressors 10 are denoted by identical reference signs. In the following text, only the differences of the piston compressor 10 in FIG. 7 from the piston compressor 10 in FIG. 6 are explained.
[0062] FIG. 7 shows a piston compressor 10 which has also a venting device in the form of a venting duct 39, which is arranged between the compression chamber 17 and the inlet system 23. Arranged in the venting duct 39 is a shut-off valve in the form of a gravity ball valve 40, which closes the venting duct 39 when the pressure in the compression chamber 17 exceeds a predetermined value which pushes the ball of the gravity ball valve 40 counter to the gravitational force thereof against a valve seat arranged above in the gravity ball valve 40. By way of the shut-off valve, any escape of compressed air from the compression chamber 17 during a compression stroke is limited.
[0063] FIG. 8 shows a schematic illustration of a sixth exemplary embodiment of a piston compressor 10 according to the invention. The structure of the piston compressor 10 in FIG. 8 corresponds largely to the structure of the piston compressor 10 illustrated in FIG. 6 and described in that regard, and so identical elements of the piston compressors 10 are denoted by identical reference signs. In the following text, only the differences of the piston compressor 10 in FIG. 8 from the piston compressor 10 in FIG. 6 are explained.
[0064] The piston compressor 10 illustrated in FIG. 8 also has a venting device in the form of a venting duct 35, which is arranged between the compression chamber 17 and the inlet system 23. In contrast to the piston compressor 10 in FIG. 6, the venting duct 35 is arranged in the upper region of the wall of the cylinder 14. The venting duct 35 also establishes a connection, through which air is able to flow, between the compression chamber 17 and the cylinder-head volume 24, which allows pressure equalization between the compression chamber 17 and the inlet system 23.
[0065] As is shown in FIG. 8, the venting duct 35 can be arranged approximately in the region swept by the upper piston ring approximately 60 before top dead center of the piston 13. As a result, while the piston compressor 10 is inoperative, compressed air is discharged from the compression chamber 17, said air passing thereto from the outlet line 27 while the piston compressor 10 is separated from the drive device. At the same time, however, the air in the compression chamber 17 is prevented from escaping therefrom during the end phase of the compression stroke.
[0066] FIG. 9 shows a schematic illustration of a seventh exemplary embodiment of a piston compressor 10 according to the invention. The structure of the piston compressor 10 in FIG. 9 corresponds largely to the structure of the piston compressor 10 illustrated in FIG. 8 and described in that regard, and so identical elements of the piston compressors 10 are denoted by identical reference signs. In the following text, only the differences of the piston compressor 10 in FIG. 9 from the piston compressor 10 in FIG. 8 are explained.
[0067] The piston compressor 10 illustrated in FIG. 9 has a venting device in the form of a venting duct 36, which is arranged between the compression chamber 17 and the interior of the crankcase 16. As in the case of the piston compressor 10 in FIG. 8, the venting duct 36 is arranged in the upper region of the wall of the cylinder 14. It establishes a connection, through which air is able to flow, between the compression chamber 17 and the crankcase 16. Since the crankcase 16 of the piston compressor 10 allows pressure equalization with respect to the environment, essentially ambient pressure prevails in the interior thereof. Thus, pressure equalization between the compression chamber 17 and the crankcase 16 can take place via the venting duct 36.
[0068] FIG. 10 shows a schematic illustration of an eighth exemplary embodiment of a piston compressor 10 according to the invention. The structure of the piston compressor 10 in FIG. 10 corresponds largely to the structure of the piston compressor 10 illustrated in FIG. 9 and described in that regard, and so identical elements of the piston compressors 10 are denoted by identical reference signs. In the following text, only the differences of the piston compressor 10 in FIG. 10 from the piston compressor 10 in FIG. 9 are explained.
[0069] The piston compressor 10 illustrated in FIG. 10 has a venting device in the form of a venting duct 37, which, in a manner corresponding to the venting duct 36 in FIG. 9, is arranged between the compression chamber 17 and the interior of the crankcase 16. Compared with the venting duct 36 in FIG. 9, a check valve 38 is arranged in the venting duct 37, said check valve 38 preventing air from flowing back into the compression chamber 17 from the crankcase 16. The check valve 38 can in this case be designed such that, even at a small pressure difference between the pressure in the compression chamber 17 and the pressure in the crankcase 16, it opens in order to prevent a pressure buildup in the compression chamber 17 during a down time of the piston compressor 10.
[0070] FIG. 11 shows an illustration of a detail of a ninth exemplary embodiment of a piston compressor 10 according to the invention, in which the inlet valve 21 forms the venting device. The elements of the inlet valve 21 are shown in an exploded illustration in FIG. 11. The inlet valve 21 forms the upper termination of the compression chamber 17 in the cylinder 14. The valve tongue 21a is embodied in one piece with a first element of the inlet valve 21, which is arranged between the cylinder 14 and an abutment element 21b of the inlet valve 21. The abutment element 21b, illustrated by way of example, has two valve openings 21c, which, depending on the pressure difference between the compression chamber 17 in the cylinder 14 and the pressure in the inlet system 23, are closed by the valve tongue 21a.
[0071] The valve tongue 21a has a curvature, which is designed such that the valve tongue 21a bears against the abutment element 21b (dashed illustration of the valve tongue 21a) from a pressure in the compression chamber 22 which is 0.4 bar higher than the pressure in the inlet system 23 (ambient pressure) in the exemplary embodiment and in this case closes the valve openings 21c. At a pressure difference of less than 0.4 bar, the valve tongue 21a always has a curvature, and so there is a connection between the inlet system 23 and the compression chamber 17. Thus, a compressed gas which has passed into the compression chamber 17 is able to be discharged through the valve openings 21c of the inlet valve 21 into the inlet line 22 without a pressure buildup in the compression chamber 17 of the compressor 10 occurring.
[0072] In another embodiment of the piston compressor 10 which is not shown but acts in the same way, the inlet valve 21 can also have an abutment element 21b which has a recess in the region of the valve openings 21c, such that the valve tongue 21a bears in a sealing manner against the abutment element 21b only from a predetermined pressure in the compression chamber 17 in this embodiment, too.
LIST OF REFERENCE SIGNS
[0073] 3 Clutch [0074] 10 Piston compressor [0075] 11 Crankshaft [0076] 12 Connecting rod [0077] 13 Piston [0078] 14 Cylinder [0079] 15 Crank drive [0080] 16 Crankcase [0081] 17 Compression chamber [0082] 20 Valve plate [0083] 21 Inlet valve [0084] 21a Valve tongue [0085] 21b Abutment element [0086] 21c Valve opening [0087] 22 Inlet line [0088] 23 Inlet system [0089] 24 Cylinder-head volume (inlet) [0090] 26 Outlet valve [0091] 26a Valve tongue [0092] 26b Valve seat [0093] 26c Abutment element [0094] 27 Outlet line [0095] 27a Cylinder-head volume (outlet) [0096] 28 Outlet opening [0097] 31 2/2-Way valve [0098] 31a Control line [0099] 32 Check valve [0100] 32a Control line [0101] 33 Check valve [0102] 34 Venting duct [0103] 35 Venting duct [0104] 36 Venting duct [0105] 37 Venting duct [0106] 38 Check valve [0107] 39 Check valve [0108] 40 Gravity ball valve
[0109] 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.
