Piston compressor with venting device

Abstract

A piston compressor for compressing a gas, which can be separated from a drive unit by means of a coupling (3), comprising an inlet valve (21) arranged between an inlet line (22) for gas to be compressed and a compression chamber (17) of the piston compressor (10), and an outlet valve (26) arranged between the compression chamber (17) of the piston compressor (10) and an outlet line (27) for compressed gas, characterized in that the piston compressor (10) has a venting device (31, 32, 33, 34, 35, 36, 37, 39) through which compressed gas, which flows back into the compression chamber (17) from the outlet line (27) during the separation of the piston compressor (10) from the drive unit, can be discharged from the compression chamber (17), wherein the compressed gas is removed from the compression chamber (17) can be discharged into an area with ambient pressure which is independent of the environment itself,a gas space (22, 24) connected to the inlet system (23) or the interior of the crankcase (16), wherein a permanently open vent channel (34, 35, 36, 39) forms the venting device, wherein at least one end of the vent channel (34, 35, 36, 39) is arranged in the valve plate (20), wherein the vent channel has such a small cross-section that pressure equalization of the compression chamber 17 with the area at ambient pressure takes place through the vent channel such that the gas volume flow that can be discharged from the compression chamber during a separation of the compressor from the drive device is at least as large as the gas volume flow of compressed gas from the outlet line that returned to the compression chamber during this period.However, the throttling effect of the small cross-section of the venting channel limits the volume flow of air discharged through the venting channel into the area of ​​ambient pressure during a compression stroke.

Description

[0001] The invention relates to a piston compressor for compressing a gas, which can be separated from a drive device by means of a coupling, with 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.

[0002] Such compressors are used, for example, for supplying compressed air to commercial vehicles, particularly for the brake system. The compressor is driven by the internal combustion engine's drivetrain. Applications are known in which a coupling is arranged between the compressor and the drive connection to disconnect the compressor from the drive when the commercial vehicle's compressed air system is filled with compressed air. In known embodiments, the compressor's outlet line is emptied simultaneously with the opening of the coupling. When the compressor is restarted, the pressure in the now depressurized outlet line must first be rebuilt before compressed air can be supplied to the compressed air system. To avoid such efficiency losses, solutions are also known in which the outlet line is not depressurized while the piston compressor is not driven.

[0003] With piston compressors of the type mentioned, there is a risk that an exhaust valve may become leaky due to contaminants such as deposits from lubricating oil residue or, in particular, particles dissolved from such residue. These exhaust valves often have a valve reed, between which such contaminants can penetrate and prevent the valve from closing completely. If, for example, an exhaust valve leaks as a result of this, in conjunction with a pressurized exhaust line during the compressor's disconnection from the drive, compressed air can flow back into the compressor's compression chamber. The pressure in the compression chamber of a piston compressor in a 12.5 bar system can then rise to as high as 6 bar. When the piston compressor is restarted with such a high pressure in the compression chamber, the first compression stroke of the piston results in a compression of the gas in the compression chamber to approximately 60 bar.The resulting torque is far too high for the clutch, which in this case slips, overheats, and experiences excessive wear. Furthermore, such high pressure in the compression chamber can also damage the compressor itself.

[0004] From the publications DE 43 21 013 A1, DE 197 45 118 A1, AT 280461 B, CH 417 835 A, GB 829 060 A and CH 668 458 A5, pressure generation systems are all known in which overpressure from the compression chamber can be released into a separate chamber. However, the separate chamber has a limited volume, which means that it cannot be guaranteed that the pressure can be reduced to ambient pressure or a harmless lower pressure. Therefore, it cannot be ensured that the clutch will not be overloaded during engagement due to high pressure in the compression chamber, which can be caused by backflowing gas from the outlet line.

[0005] The invention is therefore based on the objective of providing an improved piston compressor which avoids the aforementioned disadvantages and the resulting undesirable effects, in particular reliably preventing an overload of a clutch when engaging the compressor due to an overload caused by high pressure in the compression chamber.

[0006] To solve this problem, a piston compressor according to claim 1 is proposed.

[0007] Through such a venting channel, which establishes a permanent connection to an area with a lower pressure than the compression chamber (namely, ambient pressure), gas can be discharged from one end of the venting channel in the compression chamber, which is under higher pressure, through the venting channel to an area of ​​lower pressure (ambient pressure) at the other end. This results in pressure equalization with the compression chamber. Therefore, if gas from the pressurized outlet line flows back into the compression chamber during a separation of the piston compressor from the drive unit, no increased pressure can build up there, as the gas is discharged through the venting channel.

[0008] Such a piston compressor has an inlet line, which is part of an intake system and through which a gas to be compressed is fed to a compression chamber of the piston compressor. An inlet valve is arranged between the inlet line and the compression chamber. This valve is open during the intake of gas to be compressed into the compression chamber (when the pressure in the compression chamber is lower than the pressure in the inlet line). During the compression of the gas in the compression chamber (when the pressure in the compression chamber is higher than the pressure in the inlet line), the inlet valve closes the compression chamber from the inlet line.

[0009] An exhaust valve is located between the compression chamber and the exhaust line. This valve is open when compressed gas is expelled from the compression chamber (the pressure in the compression chamber is higher than the pressure in the exhaust line), thus defining a connection between the compression chamber and the exhaust line. During the intake of gas to be compressed into the compression chamber, the exhaust valve closes the connection between the compression chamber and the exhaust line (the pressure in the compression chamber is lower than the pressure in the exhaust line) to prevent backflow of compressed gas from the exhaust line into the compression chamber.

[0010] Both the inlet and outlet valves of piston compressors often use valves with a closing element that, depending on the pressure differential on both sides of the valve, is either pressed against the valve seat, thus closing the valve, or lifted from the valve seat, thereby opening it. A common design of such valves features a valve tongue that serves as the closing element.

[0011] The piston compressor according to the invention has a venting device through which compressed gas can be discharged from the compression chamber in order to reduce the pressure therein. In particular, compressed gas can be discharged which, during separation of the piston compressor from the drive unit, especially through an incompletely closing discharge valve, escapes from the pressurized discharge line back into the compression chamber and causes a pressure increase there.

[0012] In one embodiment of the piston compressor, the compressed gas can be discharged from the compression chamber into an area at ambient pressure via the venting device. This allows the compressed gas to escape into an area with a lower pressure than the compression chamber, into which compressed gas from the outlet line has entered. As a result of the discharge of the compressed gas, the pressure in the compression chamber decreases.

[0013] In one embodiment of the piston compressor, the ambient pressure zone is formed by the environment itself, a gas space connected to the inlet system or inlet line, or the interior of the piston compressor's crankcase. An ambient pressure zone in the inlet system can, for example, be the inlet line or a gas space connected to it, which is formed, for instance, in the cylinder head of the piston compressor and thus also constitutes part of the inlet line. In an embodiment where the ambient pressure zone is formed by the interior of the piston compressor's crankcase, the gas flowing from the piston compressor's compression chamber through the venting device is directed into the crankcase, where, in particular, pressure equalization first occurs within the crankcase and then with the environment via its venting system.

[0014] Pressure fluctuations can occur both in a gas space connected to the intake system and in the crankcase of the piston compressor: in the intake system, particularly depending on the fresh gas intake – for example, if the intake system is connected to the intake system of a correspondingly large internal combustion engine – or due to, in particular, previous crankshaft movements in the crankcase. However, since both the intake system and the crankcase are connected to the environment, and pressure fluctuations are typically constantly equalized with the environment there, the pressure prevailing in a gas space connected to the intake system or in the crankcase is considered ambient pressure in connection with this invention.

[0015] In an embodiment of the piston compressor not belonging to the invention, a switchable valve device forms the venting device by means of which compressed gas can be discharged from the compression chamber by establishing a connection between the compression chamber and an area with lower pressure, in particular ambient pressure.

[0016] This can be a switchable valve device by means of which the compression chamber of the piston compressor can optionally be connected to a lower-pressure area, particularly ambient pressure, via a vent opening located, for example, in the valve plate or the cylinder wall. A 2 / 2-way valve can be used for this purpose, which can be switched, for example, to open and close in parallel or offset with the actuation of the clutch, thus enabling pressure equalization in the compression chamber by venting compressed gas as long as the piston compressor is not driven. However, it can also be provided that such a valve device can be switched depending on other parameters, such as the actual pressure prevailing in the compression chamber, which is detected by pressure sensors connected to it or by other suitable means.

[0017] Another embodiment of the piston compressor, not belonging to the invention, features a releasable check valve that also functions as an inlet valve. Such a releasable check valve is a switchable valve device located between the inlet line and the compressor's compression chamber. It opens and closes the connection between the inlet line and the compression chamber, particularly automatically, in accordance with the function of an inlet valve. Furthermore, such a releasable check valve is a switchable valve device by means of which the connection between the inlet line and the compression chamber can be optionally opened and closed to allow pressure reduction by venting compressed gas from the compression chamber.

[0018] For example, such a releasable check valve, like the previously described switching valve, can be switched in parallel or offset to the clutch actuation, or depending on other parameters, particularly those related to the pressure in the compression chamber, which are detected, for example, by sensors. Opening the inlet valve, in the form of a releasable check valve, while the compressor is at a standstill allows pressure equalization between the compression chamber and the inlet system, preventing a significant pressure build-up in the compression chamber.

[0019] In another embodiment of the piston compressor not belonging to the invention, a check valve forms the venting device by means of which compressed gas can be discharged from the compression chamber. Such a check valve is designed in particular to open and connect the compression chamber to an area of ​​lower pressure, especially ambient pressure, when the pressure in the compression chamber rises so sharply during a first compression stroke due to compressed gas that has flowed back into the compression chamber from the outlet line during a separation of the piston compressor from the drive unit, that damage to the piston compressor or to a device connected to the piston compressor is imminent.In this case, the check valve connects the compression chamber to an area of ​​lower pressure, particularly ambient pressure, allowing the compressed gas that has returned to the compression chamber from the discharge line during separation of the piston compressor from the drive unit to be discharged. This prevents the pressure in the compression chamber from rising above a maximum value set by the check valve during the first compression stroke of the piston compressor after the clutch engages, despite the increased pressure in the compression chamber caused by compressed gas that has entered.

[0020] In another embodiment not belonging to the invention, the inlet valve forms the venting device. The inlet valve is designed such that a connection between the inlet line and the compression chamber can only be closed when the pressure in the compression chamber is at least 0.1 bar, preferably at least 0.2 bar, and particularly at least 0.5 bar higher than the pressure in the inlet line, which essentially corresponds to the ambient pressure. At a pressure in the compression chamber below the threshold of at least 0.1 bar, preferably at least 0.2 bar, and particularly at least 0.5 bar overpressure, a continuous connection exists between the inlet line and the compression chamber.Thus, a compressed gas that enters the compression chamber during a separation of the piston compressor from the drive unit, i.e., when the piston compressor is at a standstill, can be discharged into the inlet line through this opening of the inlet valve without a pressure build-up occurring in the compression chamber of the compressor.

[0021] In an embodiment of the piston compressor not belonging to the invention, in which the inlet valve can only be closed above a predetermined pressure in the compression chamber, the inlet valve has a concave valve seat, particularly on the valve plate, and a substantially flat valve reed, such that the valve reed only seals against the valve seat after elastic deformation caused by pressure in the compression chamber. In such an embodiment, the inlet valve only closes when a sufficiently high pressure acts in the compression chamber during the compression stroke, deforming the valve reed in such a way that it seals against the concave valve seat. As long as the pressure in the compression chamber is lower than the pressure that causes the inlet valve to close, the inlet valve remains open.Thus, no pressure build-up can occur in the compression chamber due to compressed gas that escapes from the outlet line back into the compression chamber during the separation of the piston compressor from the drive unit.

[0022] In another embodiment of the piston compressor, not part of the invention, in which the inlet valve can only be closed above a predetermined pressure in the compression chamber, the inlet valve has a flat valve seat and a curved valve reed. Consequently, the valve reed only seals against the valve seat after elastic deformation caused by the pressure in the compression chamber. In this embodiment as well, the inlet valve only closes when a sufficiently high pressure acts in the compression chamber during a compression stroke, deforming the curved valve reed so that it seals against the flat valve seat. Here too, the inlet valve remains open as long as the pressure in the compression chamber is lower than the pressure that, particularly during a compression stroke, would cause the inlet valve to close.Thus, even in this embodiment, a compressed gas that returns from the outlet line to the compression chamber during the separation of the piston compressor from the drive unit cannot lead to a pressure build-up in the compression chamber.

[0023] According to the invention, one end of the vent channel is arranged in the valve plate and, in particular, establishes a connection between the compression chamber and the environment of the piston compressor or its inlet system. A disadvantage of a permanently open vent channel is that it allows gas to escape from the compression chamber even during a compression stroke, thereby reducing the compressor's efficiency. However, the vent channel has such a small cross-section that pressure equalization through the vent channel is possible; the throttling effect of the small cross-section of the vent channel, however, prevents the pressure flow of a larger volume flow during a compression stroke.

[0024] An alternative design, not part of the invention, which restricts the escape of gas from the compression chamber during a compression stroke, features a suitable shut-off valve in the vent channel that closes it at a predetermined overpressure. A suitable shut-off valve for this purpose is, for example, a gravity ball valve. Advantageously, such a shut-off valve is robust against contamination by lubricating oil impurities.

[0025] In another embodiment not belonging to the invention, at least one end of the vent channel is arranged in the cylinder wall, establishing, for example, a connection with the environment of the piston compressor. Starting from the outside of the cylinder wall, the vent channel can have a connecting device in the form of a pipe, which serves as an extension of the vent channel and connects it, in particular, to the intake system or to the interior of the crankcase of the piston compressor. Such a vent channel also forms an opening in the compression chamber through which gas can escape from the compression chamber even during the compression stroke, thereby reducing the efficiency of the piston compressor.The venting channel is therefore designed to be particularly large enough to ensure pressure equalization, so that the gas volume flow that can be discharged from the compression chamber during a separation of the compressor from the drive unit is at least as large as the gas volume flow of compressed gas from the outlet line that returned to the compression chamber during this period.

[0026] In an embodiment not belonging to the invention, the vent channel is arranged in the cylinder wall such that one end is passed by the piston during the compression stroke from a certain piston position and is thus closed. This is particularly the case when the vent channel is located between a mid-stroke position of the piston and its top dead center. This arrangement of the vent channel allows gas that has returned from the exhaust port to the compression chamber during a standstill of the piston compressor to be discharged, thus preventing a pressure build-up in the compression chamber. Simultaneously, it prevents gas from escaping the compression chamber as soon as a piston ring passes the opening of the vent channel during its movement towards top dead center.

[0027] In an embodiment of the piston compressor not belonging to the invention, a check valve or a shut-off valve is arranged in the vent channel or in a connecting device connected thereto. Such a check or shut-off valve can, on the one hand, prevent gas from escaping from the compression chamber during a compression stroke of the piston compressor, and on the other hand, it can also serve to prevent the intake of potentially contaminated gas, particularly from the crankcase, into the compression chamber.

[0028] Although the piston, cylinder, cylinder head, etc., have been addressed in connection with the components of the piston compressor in the preceding text, the properties described here also apply to a piston compressor with two or more of these elements, since the present invention can be used not only for single-stage piston compressors but also for multi-stage piston compressors.

[0029] Further advantages, features and possible applications of the present invention will become apparent from the following description in conjunction with the figures.

[0030] The figures show: Fig. 1 a schematic representation of an exemplary piston compressor of the state of the art; Fig. 2. A representation of an exemplary exhaust valve as used in piston compressors in the prior art; Fig. 3 a schematic representation of a first exemplary embodiment of a piston compressor not belonging to the invention, in which the venting device has a switchable valve device; Fig. 4 a schematic representation of a second exemplary embodiment of a piston compressor not belonging to the invention, in which the venting device has a switchable valve device; Fig. 5 a schematic representation of a third exemplary embodiment of a piston compressor not belonging to the invention, in which the venting device has a check valve; Fig. 6 a schematic representation of a piston compressor according to the invention, in which the venting device is formed by a venting channel; Fig. 7 a schematic representation of a further exemplary embodiment of a piston compressor not belonging to the invention, in which the venting device has a venting channel with a shut-off valve; Fig. 8 a schematic representation of a further exemplary embodiment of a piston compressor not belonging to the invention, in which the venting device has a venting channel; Fig. 9 a schematic representation of a further exemplary embodiment of a piston compressor not belonging to the invention, in which the venting device has a venting channel; Fig. 10 a schematic representation of a further exemplary embodiment of a piston compressor not belonging to the invention in which the venting device has a venting channel; and Fig. 11 a representation of a detail of a further exemplary embodiment not belonging to the invention of a piston compressor according to the invention, in which the inlet valve forms the venting device.

[0031] Fig. Figure 1 shows a schematic representation of an exemplary piston compressor 10 as known in the prior art. The crankshaft 11 of the piston compressor 10 is connected to a drive unit (not shown, here an internal combustion engine) via a coupling 3 and can be selectively disconnected from this drive unit by means of the coupling 3. When the coupling 3 is open, no torque is transmitted to the crankshaft 11 of the piston compressor 10, so that the crankshaft 11 is stationary during the disconnection of the piston compressor 10 from the drive unit.

[0032] The crankshaft 11 is connected to an eccentrically mounted connecting rod 12, on which a piston 13 is mounted. The piston 13 is axially movable within a cylinder 14 of the piston compressor 10. The crankshaft assembly 15, comprising at least one crankshaft 11, one connecting rod 12, and one piston 13, is arranged in a crankcase 16, which is rigidly connected to the cylinder 14. A rotary movement of the crankshaft 11 causes the connecting rod 12 to move the piston 13 within the cylinder 14, resulting in a reciprocating motion.

[0033] 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. An inlet valve 21 is arranged on the valve plate 20, positioned between an inlet line 22 and the compression chamber 17. The inlet line 22 is part of an intake system 23, which draws fresh air from the environment through a filter (not shown) and supplies it to the compression chamber 17 via the inlet line 22 and through the cylinder head (not shown). The cylinder head is located 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 designed as a shut-off valve, which allows fresh air to be drawn into the compression chamber 17, but prevents the backflow of air drawn into the compression chamber 17 via the inlet line 22.

[0034] Furthermore, an outlet valve 26 is arranged on the valve plate 20, which is located between the compression chamber 17 and an outlet line 27. Compressed gas, in this case air, is supplied via the outlet line 27 to a compressed air storage tank (not shown). The outlet valve 26, which is also designed as a shut-off valve, prevents compressed air from flowing back from the outlet line 27 into the compression chamber 17.

[0035] Fig. Figure 2 shows an illustration of an exemplary exhaust valve 26, as is frequently used in piston compressors 10 in the prior art. The exhaust 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 exhaust opening 28, which connects the compression chamber 17 with a cylinder head volume 27a arranged in the valve plate 20 and cylinder head of the piston compressor 10, which forms part of the exhaust line 27.

[0036] The exhaust valve 26 has a valve reed 26a as its valve body, which, upon reaching a predetermined pressure difference between the compression chamber 17 and the exhaust line 27, releases from the valve seat 26b and allows air to flow from the compression chamber 17 into the exhaust line 27. The exhaust valve 26 also has a contact element 26c arranged above the exhaust opening 28, against which the valve reed 26a rests when open. As soon as the valve reed 26a releases from the valve seat 26b, the pressurized air from the compression chamber 17 can flow through the lateral open areas past the valve reed 26a and the contact element 26c into the exhaust line 27.

[0037] If contaminants from the compression chamber 17 or from the cylinder head volume 27a, which may be detached, for example, from deposits forming due to residues in the flowing air from the hot upper surface of the piston 13, the valve plate 20, or the cylinder head volume 27a, enter the space between the valve tongue 26a and the valve seat 26b, there is a risk that the exhaust valve 26 will no longer close completely. In this case, compressed air from the exhaust line 27 can flow back into the compression chamber 17 as soon as the pressure in the compression chamber 17 drops below the pressure in the exhaust line 27. In a 12.5 bar compressed air system of a commercial vehicle, for example, the compression chamber 17 of the piston compressor 10 can be pressurized to up to 6 bar by the backflowing air. When the piston compressor 10 is then reconnected to the drive unit, the piston compressor 10 generates an internal pressure of approximately 60 bar on the first stroke.If the compression chamber 17 can withstand this enormous internal pressure, the torque generated at the crankshaft 11 is usually far too high for the clutch 3, causing it to slip, overheat, and wear out unacceptably quickly.

[0038] Fig. Figure 3 shows a schematic representation of a first exemplary embodiment of a piston compressor 10. The structure of the piston compressor 10 in Fig. 3 largely corresponds to the structure of the one in Fig. The piston compressor 10 shown and described in Figure 1 is used so that identical elements of the piston compressors 10 are designated with the same reference numerals. In the following, only the differences of the piston compressor 10 from Figure 1 are discussed. Fig. 3 compared to the piston compressor 10 from Fig. 1 explained.

[0039] The in Fig. The piston compressor 10 shown in Figure 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. The control line 31a of the 2 / 2-way valve 31 is connected to the control of the clutch 3 via a signal. When the clutch 3 is opened and the piston compressor 10 is no longer driven, the 2 / 2-way valve 31 is switched from the closed position shown to an open position in order to establish an airflow connection between the compression chamber 17 and the inlet system 23.

[0040] If, for example, compressed air enters the compression chamber 17 during the standstill of the piston compressor 10 due to a leaking exhaust valve 26, pressure equalization with the inlet line 22 can occur via the open 2 / 2-way valve 31. This prevents a pressure build-up in the compression chamber 17, which could lead to damage to the piston compressor 10 and / or the coupling 3, particularly during the first compression stroke when the piston compressor 10 is restarted.

[0041] Fig. Figure 4 shows a schematic representation of a second exemplary embodiment of a piston compressor 10. The construction of the piston compressor 10 is also shown in Fig. 4 largely corresponds to the structure of the one in Fig. The piston compressor 10 shown and described in Figure 1 is used so that identical elements of the piston compressors 10 are designated with the same reference numerals. In the following, only the differences of the piston compressor 10 from Figure 1 are discussed. Fig. 4 compared to the piston compressor 10 from Fig. 1 explained.

[0042] The in Fig. The piston compressor 10 shown in Figure 4 has a venting device in the form of a releasable check valve 32, which also serves as an inlet valve. The releasable check valve 32 is thus arranged between the compression chamber 17 and the inlet system 23. During the intake of fresh air from the inlet line 22 into the compression chamber 17, the releasable check valve 32 opens automatically due to the pressure differential across it. The releasable check valve 32 is also a switchable valve device, which, in addition to opening automatically during the intake of fresh air, can also be switched to an open position by means of a control signal. In the exemplary embodiment shown in Fig. 4 The control line 32a of the unlockable check valve 32 is connected to a control device (not shown) via a signal. Depending on at least one predetermined parameter, such as the pressure in the compression chamber 17, the unlockable check valve 32 can be opened to establish a connection between the compression chamber 17 and the inlet line 22.

[0043] If, for example, compressed air enters the compression chamber 17 during the standstill of the piston compressor 10 due to a leaking exhaust valve 26, the unlockable check valve 32 can be opened to allow pressure equalization with the inlet line 22. This prevents a pressure build-up in the compression chamber 17, which could lead to damage to the piston compressor 10 and / or the coupling 3, particularly during the first compression stroke when the piston compressor 10 is restarted.

[0044] When the piston compressor 10 is restarted, the unlockable check valve 32 is switched back into the working position by the control device, in which it opens automatically when fresh air is drawn from the inlet line 22 into the compression chamber 17 due to the pressure difference applied thereto.

[0045] Fig. Figure 5 shows a schematic representation of a third exemplary embodiment of a piston compressor 10. The construction of the piston compressor 10 is also shown in Fig. 5 largely corresponds to the structure of the one in Fig. The piston compressor 10 shown and described in Figure 1 is used so that identical elements of the piston compressors 10 are designated with the same reference numerals. In the following, only the differences of the piston compressor 10 from Figure 1 are discussed. Fig. 5 compared to the piston compressor 10 from Fig. 1 explained.

[0046] The in Fig. The piston compressor 10 shown in Figure 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, which is arranged between the compression chamber 17 and the inlet system 23 in addition to the inlet valve 21, blocks in the opposite direction to the inlet valve 21, so that it is closed during the intake of fresh air into the compression chamber 17 and during compression in normal operation of the piston compressor 10.

[0047] If at the in Fig. In the embodiment shown in Figure 5, if, for example, compressed air enters the compression chamber 17 during the standstill of the piston compressor 10 due to a leaking outlet valve 26, a pressure build-up initially occurs in the compression chamber 17. The resulting pressure does not exceed the value achieved during a compression stroke, so venting of the compression chamber 17 is not initially necessary. Only during the first compression stroke of the piston compressor 10 after its restart does a significantly increased pressure arise due to the pre-compressed air in the compression chamber 17, which can lead to damage to the piston compressor 10 and / or the coupling 3.The check valve 33 is therefore designed to open a connection between the compression chamber 17 and the inlet line 21 with a sufficiently large cross-section to discharge air from the compression chamber 17 as soon as the pressure in the compression chamber 17 exceeds a critical value. In the case of the exemplary piston compressor 10 for a commercial vehicle, the peak pressure in the compression chamber during normal operation is between approximately 16 and 19 bar. An exemplary check valve 33 is therefore designed to open, for example, at a pressure of 20 bar in the compression chamber 17 and thus discharge compressed air from the compression chamber 17.

[0048] Fig. Figure 6 shows a schematic representation of an embodiment of a piston compressor 10 according to the invention. The construction of the piston compressor 10 is also shown. Fig. 6 largely corresponds to the structure of the one in Fig. The piston compressor 10 shown and described in Figure 1 is used so that identical elements of the piston compressors 10 are designated with the same reference numerals. In the following, only the differences of the piston compressor 10 from Figure 1 are discussed. Fig. 6 compared to the piston compressor 10 from Fig. 1 explained.

[0049] The in Fig. The piston compressor 10 shown in Figure 6 has a venting device in the form of a venting channel 34, which is arranged between the compression chamber 17 and the inlet system 23. The venting channel 34 provides an air-permeable connection between the compression chamber 17 and the inlet system 23, so that no pressure can build up in the compression chamber 17 during a standstill of the piston compressor that is significantly higher than the ambient pressure.

[0050] In the Fig. In the embodiment shown in Figure 6, the vent channel 34 is arranged in the area of ​​the valve plate 20 on the top of the cylinder 14, so that a constant pressure equalization with the inlet line 32 of the piston compressor 10 occurs via the vent channel 34. If compressed air from the outlet line 27 enters the compression chamber 17 while the piston compressor 10 is at rest, a pressure equalization with the inlet line 22 occurs via the vent channel 34, thus preventing a pressure build-up in the compression chamber 17. A disadvantage of such a vent channel 34, however, is that it remains open even during a compression stroke of the piston compressor 10, and air to be compressed escapes from the compression chamber 17 during this phase. This reduces the efficiency of the piston compressor 10.The vent channel 34 is therefore designed to have only a small cross-section in order to allow sufficient pressure equalization during the standstill of the piston compressor 10 with the inlet system 23, but on the other hand to have a throttling effect at high pressures in order to limit the volume flow of the discharged air.

[0051] Fig. Figure 7 shows a schematic representation of a sixth exemplary embodiment of a piston compressor 10. The structure of the piston compressor 10 in Fig. 7 largely corresponds to the structure of the one in Fig. The piston compressor 10 shown and described in Figure 6 is used so that identical elements of the piston compressor 10 are designated with the same reference numerals. In the following, only the differences of the piston compressor 10 from Figure 6 are discussed. Fig. 7 compared to the piston compressor 10 from Fig. 6 explained.

[0052] In Fig. Figure 7 shows a piston compressor 10, which also has a venting device in the form of a vent channel 39 arranged between the compression chamber 17 and the inlet system 23. A shut-off valve in the form of a gravity ball valve 40 is arranged in the vent channel 39. This valve closes the vent channel 39 when the pressure in the compression chamber 17 exceeds a predetermined value, which forces the ball of the gravity ball valve 40 against gravity against a valve seat located at the top of the gravity ball valve 40. The shut-off valve thus restricts the escape of compressed air from the compression chamber 17 during a compression stroke.

[0053] Fig. Figure 8 shows a schematic representation of another exemplary embodiment of a piston compressor 10. The structure of the piston compressor 10 in Fig. 8 largely corresponds to the structure of the one in Fig. The piston compressor 10 shown and described in Figure 6 is used so that identical elements of the piston compressor 10 are designated with the same reference numerals. In the following, only the differences of the piston compressor 10 from Figure 6 are discussed. Fig. 8 compared to the piston compressor 10 from Fig. 6 explained.

[0054] Also the one in Fig. The piston compressor 10 shown in Figure 8 has a venting device in the form of a venting channel 35, which is arranged between the compression chamber 17 and the inlet system 23. In contrast to the piston compressor 10 from Figure 8, the piston compressor 10 has a venting device in the form of a venting channel 35, which is arranged between the compression chamber 17 and the inlet system 23. Fig. 6 The vent channel 35 is located in the upper area of ​​the wall of the cylinder 14. The vent channel 35 also provides an air-flowable connection between the compression chamber 17 and the cylinder head volume 24, which enables pressure equalization between the compression chamber 17 and the intake system 23.

[0055] As in Fig. As shown in Figure 8, the vent channel 35 can be located approximately in the area over which the upper piston ring sweeps about 60° before the top dead center of the piston 13. This allows compressed air to be discharged from the compression chamber 17 during the standstill of the piston compressor 10. This air enters the compression chamber from the outlet line 27 while the piston compressor 10 is disconnected from the drive unit. At the same time, however, it prevents the air from escaping from the compression chamber 17 during the final phase of the compression stroke.

[0056] Fig. Figure 9 shows a schematic representation of another exemplary embodiment of a piston compressor 10. The construction of the piston compressor 10 in Fig. 9 largely corresponds to the structure of the one in Fig. The piston compressor 10 shown and described in Figure 8 is used so that identical elements of the piston compressor 10 are designated with the same reference numerals. In the following, only the differences of the piston compressor 10 from Figure 8 are discussed. Fig. 9 compared to the piston compressor 10 from Fig. 8 explained.

[0057] The in Fig. The piston compressor 10 shown in Figure 9 has a venting device in the form of a venting channel 36, which is arranged between the compression chamber 17 and the interior of the crankcase 16. As with the piston compressor 10 from Fig. The vent channel 36 is located in the upper part of the cylinder wall 14. This channel provides an airflow connection between the compression chamber 17 and the crankcase 16. Since the crankcase 16 of the piston compressor 10 allows pressure equalization with the surroundings, the internal pressure is essentially at ambient level. Therefore, pressure equalization between the compression chamber 17 and the crankcase 16 can occur via the vent channel 36.

[0058] Fig. Figure 10 shows a schematic representation of another exemplary embodiment of a piston compressor 10. The structure of the piston compressor 10 in Fig. 10 largely corresponds to the structure of the one in Fig. The piston compressor 10 shown and described in Figure 9 is designated by the same reference numerals, so that identical elements of the piston compressors 10 are designated by the same reference numerals. In the following, only the differences of the piston compressor 10 from Figure 9 are discussed. Fig. 10 compared to the piston compressor 10 from Fig. 9 explained.

[0059] The in Fig. The piston compressor 10 shown in Figure 10 has a venting device in the form of a venting channel 37, which corresponds to the venting channel 36 made of Fig. 9 is located between the compression chamber 17 and the interior of the crankcase 16. Opposite the ventilation channel 36 Fig. 9 A check valve 38 is arranged in the vent channel 37, which prevents air from flowing back from the crankcase 16 into the compression chamber 17. The check valve 38 can be designed to open even at a small pressure difference between the pressure in the compression chamber 17 and the pressure in the crankcase 16, in order to prevent pressure build-up in the compression chamber 17 during a period of inactivity of the piston compressor 10.

[0060] Fig. Figure 11 shows a detail of another exemplary embodiment of a piston compressor 10, in which the inlet valve 21 forms the venting device. The elements of the inlet valve 21 are shown in Fig. Figure 11 shows an exploded view. The inlet valve 21 forms the upper end of the compression chamber 17 in the cylinder 14. The valve tongue 21a is integrally formed with a first element of the inlet valve 21, which is arranged between the cylinder 14 and a contact element 21b of the inlet valve 21. The contact element 21b, shown as an example, has two valve openings 21c, which are closed by the valve tongue 21a depending on the pressure difference between the compression chamber 17 in the cylinder 14 and the pressure in the inlet system 23.

[0061] The valve tongue 21a has a curvature designed such that, at a pressure in the compression chamber 22, the valve tongue 21a rests against the mounting element 21b (dashed line representing the valve tongue 21a) which, in the exemplary embodiment, is 0.4 bar higher than the pressure in the inlet system 23 (ambient pressure), thereby closing the valve openings 21c. At a pressure difference of less than 0.4 bar, the valve tongue 21a always has a curvature such that a connection exists between the inlet system 23 and the compression chamber 17. Thus, compressed gas that has entered the compression chamber 17 can be discharged through the valve openings 21c of the inlet valve 21 into the inlet line 22 without a pressure build-up occurring in the compression chamber 17 of the compressor 10.

[0062] In another embodiment of the piston compressor 10, not shown but functioning in the same way, the inlet valve 21 can also have a contact element 21b which has a recess in the area of ​​the valve openings 21c, so that the valve tongue 21a only seals against the contact element 21b in this embodiment as well from a predetermined pressure in the compression chamber 17. REFERENCE MARK LIST 3 Clutch 10 piston compressor 11 Crankshaft 12 connecting rods 13 pistons 14 cylinders 15 Crankshaft 16 Crankcase 17 Congestion area 20 Valve plate 21 Inlet valve 21a Valve tongue 21b Plant element 21c Valve opening 22 Admission Management 23 Inlet system 24 cylinder head volume (intake) 26 Exhaust valve 26a Valve tongue 26b Valve seat 26c Plant element 27 Outlet pipe 27a Cylinder head volume (exhaust) 28 Outlet opening 31 2 / 2-way valve 31a Control line 32 Check valve 32a Control line 33 Check valve 34 Ventilation duct 35 Ventilation duct 36 Ventilation duct 37 Ventilation duct 38 Check valve 39 Check valve 40 Gravity ball valve

Claims

[1] Piston compressor for compressing a gas, which can be separated from a drive unit by means of a coupling (3), comprising an inlet valve (21) which is arranged between an inlet line (22) for gas to be compressed and a compression chamber (17) of the piston compressor (10), and an outlet valve (26) which is arranged between the compression chamber (17) of the piston compressor (10) and an outlet line (27) for compressed gas, characterized bythat the piston compressor (10) has a venting device (31, 32, 33, 34, 35, 36, 37, 39) through which compressed gas, which during the separation of the piston compressor (10) from the drive device returns from the outlet line (27) to the compression chamber (17), can be discharged from the compression chamber (17), wherein the compressed gas can be discharged from the compression chamber (17) into an area at ambient pressure, which is formed by the environment itself, a gas space (22, 24) connected to the inlet system (23), or the interior of the crankcase (16), wherein a permanently open venting channel (34, 35, 36, 39) forms the venting device, wherein at least one end of the venting channel (34, 35, 36, 39) is located in the valve plate (20) is arranged, wherein the vent channel has such a small cross-section that pressure equalization of the compression chamber 17 with the area with ambient pressure takes place through the vent channel in such a way thatthat the gas volume flow rate that can be discharged from the compression chamber during a separation of the compressor from the drive device is at least as large as the gas volume flow rate of compressed gas from the outlet line back into the compression chamber during this period, whereby the throttling effect of the small cross-section of the venting channel limits the volume flow rate of the air discharged through the venting channel into the area of ​​ambient pressure during a compression stroke.

Images