DE102016201208B4 - Piston compressor with ventilation device - Google Patents

Abstract

Piston compressor for compressing a gas, which can optionally be separated from a drive device by means of a clutch (3), with 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). is 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, the piston compressor (10) having a ventilation device (31, 32, 33, 34, 35 , 36, 37, 39), through which compressed gas, which passes from the outlet line (27) back into the compression chamber (17) during the separation of the piston compressor (10) from the drive device, can be removed from the compression chamber (17), characterized in that the inlet valve (21) forms the ventilation device, the inlet valve (21) being designed in such a way that a connection between the inlet line (22) and the compression chamber (17) can only be closed from a predetermined pressure in the compression chamber (17). , wherein the predetermined pressure is at least 0.1 bar, preferably at least 0.2 bar and in particular at least 0.5 bar higher than the pressure in the inlet line (22).

Description

The invention relates to a piston compressor for compressing a gas, which can optionally be separated from a drive device by means of a clutch, 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 between the compression chamber of the piston compressor and an outlet line for compressed gas.

Such compressors are used, for example, for supplying compressed air to commercial vehicles, in particular for supplying compressed air to the brake system. The compressor is driven via the drive train of the combustion engine. Applications are known in which a clutch is arranged between the compressor and the drive connection in order to separate the compressor from the drive when the compressed air system of the commercial vehicle is filled with compressed air. In known embodiments, the outlet line of the compressor is emptied at the same time as the clutch is opened. When the compressor is put back into operation, the pressure in the then pressure-free outlet line must first be built up again before compressed air can be delivered into 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.

With piston compressors of the type mentioned, there is a risk that an outlet valve will leak due to contamination such as deposits from lubricating oil residues or, in particular, particles detached from them. The exhaust valves often have a valve tongue between which and the valve seat such contaminants can get and prevent the valve from closing completely. In the event of, for example, a resulting leak in an outlet valve in conjunction with a pressurized outlet line during the separation of the compressor from the drive, compressed air can get back into the compression chamber of the compressor. The pressure in the compression chamber of a piston compressor in a 12.5 bar system can then rise to up to 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 the gas in the compression chamber being compressed to approximately 60 bar. The resulting torque is far too high for the clutch, which in this case slips, overheats and suffers excessive wear. In addition, such high pressure in the compression chamber can also lead to damage to the compressor itself.

DE 43 21 013 A1 discloses a piston compressor according to the preamble of claim 1. Another piston compressor is from the DE 39 09 531 A1 known.

The invention is therefore based on the object of providing an improved piston compressor which avoids the aforementioned disadvantages and the resulting undesirable effects.

To solve this problem, a piston compressor according to claim 1 is proposed. Further developments of the piston compressor are the subject of the dependent claims.

To solve the problem, a piston compressor for compressing a gas is proposed, which can optionally be separated from a drive device by means of a clutch, 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 between the Compression chamber of the piston compressor and an outlet line for compressed gas is arranged. The piston compressor has a venting device through which compressed gas can be removed from the compression chamber, which returns from the outlet line into the compression chamber during the separation of the piston compressor from the drive device. The inlet valve forms the venting device, the inlet valve being designed in such a way that a connection between the inlet line and the compression chamber can only be closed from a predetermined pressure in the compression chamber, the predetermined pressure being at least 0.1 bar, preferably at least 0.2 bar and in particular is at least 0.5 bar higher than the pressure in the inlet line.

Such a piston compressor has an inlet line, which is in particular part of an inlet system and through which a gas to be compressed is led to a compression chamber of the piston compressor. An inlet valve is arranged between the inlet line and the compression chamber, which is opened during the suction of gas to be compressed into the compression chamber (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 (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.

An outlet valve is arranged between the compression chamber and the outlet line, which is opened when the compressed gas is ejected from the compression chamber (the pressure in the compression chamber is higher than the pressure in the outlet line) and thus defines a connection between the compression chamber and the outlet line. During the suction of gas to be compressed into the compression chamber, the outlet valve closes the connection between the compression chamber and the outlet line (the pressure in the compression chamber is lower than the pressure in the outlet line) in order to prevent compressed gas from flowing back from the outlet line into the compression chamber.

For both inlet and outlet valves of piston compressors, valves with a closing body are often used, which, depending on the pressure difference on both sides of the valve, is pressed onto the valve seat and thereby closes or is lifted from the valve seat, thereby opening the valve. A common design of such valves has a valve tongue that serves as a closing body.

The piston compressor according to the invention has a venting device through which compressed gas can be removed from the compression chamber in order to reduce the pressure therein. In particular, compressed gas can be removed, which, during a separation of the piston compressor from the drive device, returns from the pressurized outlet line back into the compression chamber, in particular through an outlet valve that does not close completely, and causes an increase in pressure there.

In one embodiment of the piston compressor, the compressed gas can be removed from the compression chamber into an area with lower pressure, in particular ambient pressure, by means of the venting device. This allows the compressed gas to escape into an area that has a lower pressure than the compression space into which compressed gas has penetrated from the outlet line. As the compressed gas is removed, the pressure in the compression chamber drops.

In one embodiment of the piston compressor, the area with the ambient pressure is formed by the environment itself, a gas space connected to the inlet system or the inlet line, or the interior of the crankcase of the piston compressor. An area with ambient pressure in the inlet system can be, for example, the inlet line or a gas space connected to it, which is formed, for example, in the cylinder head of the piston compressor and thus also represents part of the inlet line. In one embodiment, in which the area with the ambient pressure is formed by the interior of the crankcase of the piston compressor, the gas flowing through the ventilation device from the compression chamber of the piston compressor is guided into the crankcase, where in particular pressure equalization is first carried out in the crankcase and then via its ventilation system the surrounding area takes place.

Pressure fluctuations can occur both in a gas space connected to the inlet system and in the crankcase of the piston compressor: in the inlet system, in particular depending on the fresh gas intake - for example if the inlet system is in connection with the inlet system of a correspondingly large internal combustion engine - or due in particular to previous crank drive movements in the crankcase . However, since both the inlet system and the crankcase are connected to the environment and there is usually constant compensation of pressure fluctuations with the environment, the pressure prevailing in a gas space connected to the inlet system or in the crankcase is considered ambient pressure in the context of this invention .

In one embodiment of the piston compressor, a switchable valve device forms the venting device, by means of which compressed gas can be removed from the compression chamber by establishing a connection between the compression chamber and an area with lower pressure, in particular ambient pressure.

This can be a switchable valve device, by means of which the compression chamber of the piston compressor can optionally be connected to an area with lower pressure, in particular ambient pressure, via a vent opening arranged, for example, in the valve plate or in the cylinder wall. For this purpose, in particular, a 2/2-way valve can be used, which can be switched, for example, in such a way that it opens and closes in particular in parallel or offset with the actuation of the clutch and thus enables pressure equalization in the compression chamber by discharging compressed gas as long as the Piston compressor is not driven. However, it can also be provided to switch such a valve device depending on other parameters, such as the pressure actually prevailing in the compression chamber, which is detected via pressure sensors connected to it or in another suitable manner.

Another embodiment of the piston compressor has an unlockable check valve, which also takes on the function of the inlet valve. Such an unlockable check valve represents a switchable valve device which is arranged between the inlet line and the compression chamber of the compressor and in particular automatically opens and closes the connection between the inlet line and the compression chamber in accordance with the function of an inlet valve. In addition, such an unlockable check valve represents a switchable valve device, by means of which the connection between the inlet line and the compression chamber can optionally be opened and closed in order to enable a pressure reduction by discharging compressed gas from the compression chamber.

For example, such an unlockable check valve, like the previously described switching valve, can be switched in parallel or offset to the clutch actuation or depending on other parameters, in particular related to the pressure in the compression chamber, which are detected, for example, by means of sensors. By opening the inlet valve in the form of an unlockable check valve while the compressor is at a standstill, pressure equalization can take place between the compression chamber and the inlet system, so that no significant pressure build-up can take place in the compression chamber.

In a further embodiment of the piston compressor, a check valve forms the venting device, by means of which compressed gas can be removed from the compression chamber. Such a check valve is in particular designed so that it then opens and connects the compression chamber with a region with a lower pressure, in particular ambient pressure, when the pressure in the compression chamber is due to a compressed pressure that has returned from the outlet line to the compression chamber during a separation of the piston compressor from the drive device Gas rises so much during a first compression stroke that there is a risk of damage to the piston compressor or a device connected to the piston compressor. In this case, the check valve establishes a connection between the compression chamber and an area with a lower pressure, in particular ambient pressure, whereby the compressed gas, which has returned from the outlet line to the compression chamber during separation of the piston compressor from the drive device, can be removed. This means that the pressure in the compression chamber does not rise above a maximum value set by the check valve during the first compression stroke of the piston compressor after closing the clutch, despite an increased pressure in the compression chamber due to a compressed gas that has penetrated there.

In an embodiment according to the invention, the inlet valve forms the venting device. The inlet valve is designed in such a way that a connection between the inlet line and the compression chamber can only be closed from a pressure in the compression chamber that is at least 0.1 bar, preferably at least 0.2 bar and in particular at least 0.5 bar higher than that Pressure in the inlet line that is essentially equal to the ambient pressure. At a pressure in the compression chamber that is below the limit of at least 0.1 bar, preferably at least 0.2 bar and in particular at least 0.5 bar excess pressure, there is a continuous connection between the inlet line and the compression chamber. A compressed gas that enters the compression chamber during separation of the piston compressor from the drive device, 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 pressure building up in the compression chamber of the compressor.

In an embodiment of the piston compressor, in which the inlet valve can only be closed from a predetermined pressure in the compression chamber, the inlet valve has a concave valve seat, in particular on the valve plate, and a substantially flat valve tongue, so that the valve tongue only opens after a pressure elastic deformation caused in the compression chamber lies sealingly against the valve seat. In such an embodiment, the inlet valve only closes when a sufficiently high pressure acts in the compression chamber during the compression stroke, which deforms the valve tongue in such a way that it lies sealingly against the concave valve seat. As long as the pressure in the compression chamber has a lower value than the pressure that causes the inlet valve to close, the inlet valve is open. Compressed gas that returns from the outlet line to the compression chamber during the separation of the piston compressor from the drive device cannot cause pressure to build up in the compression chamber.

In another embodiment of the piston compressor, 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 tongue. The valve tongue therefore only lies sealingly against the valve seat after an elastic deformation caused by the pressure in the compression chamber. In this embodiment too, the inlet valve only closes when During a compression stroke, a sufficiently high pressure acts in the compression chamber, which deforms the curved valve tongue in such a way that it lies sealingly against the newly formed valve seat. Here too, the inlet valve remains open as long as the pressure in the compression chamber has a lower value than the pressure that leads to the inlet valve closing, particularly during a compression stroke. In this embodiment, too, a compressed gas that returns from the outlet line into the compression chamber during the separation of the piston compressor from the drive device cannot lead to a build-up of pressure in the compression chamber.

In another embodiment of the piston compressor, a ventilation channel forms the ventilation device. Through such a ventilation channel, which in particular establishes a permanent connection to an area with a lower pressure than the compression chamber, in particular ambient pressure, gas can flow from one end of the ventilation channel in the compression chamber, which is under a higher pressure, through the ventilation channel into an area with a lower pressure Pressure, in particular ambient pressure, is dissipated at the other end of the ventilation channel. This results in pressure equalization with the compression chamber. If, during a separation of the piston compressor from the drive device, gas from the pressurized outlet line returns to the compression chamber, no increased pressure can build up there because the gas is discharged through the ventilation channel.

In one embodiment, at least one end of the ventilation channel is arranged in the valve plate and in particular establishes a connection of the compression chamber to the environment of the piston compressor or to its inlet system. The disadvantage of a permanently open ventilation channel is that it allows the gas to escape from the compression chamber even during a compression stroke, which reduces the efficiency of the compressor. In one embodiment, however, the ventilation channel has such a small cross section that pressure equalization through the ventilation channel is possible, but the throttling effect of the small cross section of the ventilation channel prevents the pressure flow of a larger volume flow during a compression stroke.

An alternative design, which restricts the gas from escaping from the compression chamber during a compression stroke, has a suitable check valve in the ventilation channel, which closes it above a predetermined overpressure. A check valve suitable for this is, for example, a gravity ball valve. Such a check valve is advantageously designed to be robust against contamination by lubricating oil impurities.

In another embodiment, at least one end of the ventilation channel is arranged in the cylinder wall, which, for example, establishes a connection with the environment of the piston compressor. Starting from the outside of the cylinder wall, the ventilation channel can have a connecting device in the form of a line, which serves as an extension of the ventilation channel and connects it in particular to the inlet system or to the interior of the crankcase of the piston compressor. Such a ventilation 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 ventilation channel is therefore designed to be large enough in particular to ensure pressure equalization, so that the gas volume flow that can thereby be removed from the compression chamber during a separation of the compressor from the drive device is at least as large as that returned from the outlet line during this period of time Gas volume flow of compressed gas from the outlet line reached the compression chamber.

In one embodiment, the ventilation channel is arranged in the cylinder wall in such a way that one end passes through the piston during the compression stroke from a certain piston position and is therefore closed. This is particularly the case when the ventilation channel is arranged between a middle stroke position of the piston and its top dead center. This arrangement of the ventilation channel allows gas that has passed from the outlet channel back into the compression chamber while the piston compressor is at a standstill to be removed in order to prevent pressure from building up in the compression chamber. At the same time, gas escape from the compression chamber is prevented as soon as a piston ring has passed the opening of the ventilation channel during the movement towards top dead center.

In one embodiment of the piston compressor, a check valve or a check valve is arranged in the ventilation channel or in a connecting device connected thereto. On the one hand, such a check or check valve can prevent gas from escaping from the compression chamber during a compression stroke of the piston compressor, on the other hand, such a check or check valve can also serve to prevent the suction of potentially contaminated gas prevent gas from entering the compression chamber, especially from the crankcase.

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

Further advantages, features and possible applications of the present invention as well as examples that facilitate understanding of the invention result from the following description in connection with the figures.

• 1 eine schematische Darstellung eines beispielhaften Kolbenkompressors des Stands der Technik;
• 2 eine Darstellung eines beispielhaften Auslassventils wie es in Kolbenkompressoren im Stand der Technik verwendet wird;
• 3 eine schematische Darstellung eines ersten beispielhaften Kolbenkompressors, bei welchem die Entlüftungseinrichtung eine schaltbare Ventileinrichtung aufweist;
• 4 eine schematische Darstellung einer beispielhaften Ausführungsform eines erfindungsgemäßen Kolbenkompressors, bei welcher die Entlüftungseinrichtung eine schaltbare Ventileinrichtung aufweist;
• 5 eine schematische Darstellung eines zweitenbeispielhaften Kolbenkompressors, bei welchem die Entlüftungseinrichtung ein Rückschlagventil aufweist;
• 6 eine schematische Darstellung eines dritten beispielhaften Kolbenkompressors, bei welchem die Entlüftungseinrichtung einen Entlüftungskanal aufweist;
• 7 eine schematische Darstellung eines vierten beispielhaften Kolbenkompressors, bei welchem die Entlüftungseinrichtung einen Entlüftungskanal mit Sperrventil aufweist;
• 8 eine schematische Darstellung eines fünften beispielhaften Kolbenkompressors, bei welchem die Entlüftungseinrichtung einen Entlüftungskanal aufweist;
• 9 eine schematische Darstellung eines sechsten beispielhaften Kolbenkompressors, bei welchem die Entlüftungseinrichtung einen Entlüftungskanal aufweist;
• 10 eine schematische Darstellung eines siebten beispielhaften Kolbenkompressors, bei welchem die Entlüftungseinrichtung einen Entlüftungskanal aufweist; und
• 11 eine Darstellung eines Details einer beispielhaften Ausführungsform eines erfindungsgemäßen Kolbenkompressors, bei welcher das Einlassventil die Entlüftungseinrichtung bildet.

Show in the figures:

• 1 a schematic representation of an exemplary prior art piston compressor;
• 2 a representation of an exemplary exhaust valve as used in prior art reciprocating compressors;
• 3 a schematic representation of a first exemplary piston compressor, in which the venting device has a switchable valve device;
• 4 a schematic representation of an exemplary embodiment of a piston compressor according to the invention, in which the venting device has a switchable valve device;
• 5 a schematic representation of a second exemplary piston compressor in which the venting device has a check valve;
• 6 a schematic representation of a third exemplary piston compressor, in which the venting device has a venting channel;
• 7 a schematic representation of a fourth exemplary piston compressor, in which the venting device has a venting channel with a check valve;
• 8th a schematic representation of a fifth exemplary piston compressor, in which the venting device has a venting channel;
• 9 a schematic representation of a sixth exemplary piston compressor, in which the venting device has a venting channel;
• 10 a schematic representation of a seventh exemplary piston compressor, in which the venting device has a venting channel; and
• 11 a representation of a detail of an exemplary embodiment of a piston compressor according to the invention, in which the inlet valve forms the venting device.

1 shows a schematic representation of an exemplary piston compressor 10 as is known as prior art. The crankshaft 11 of the piston compressor 10 is connected via a clutch 3 to a drive device (not shown, here an internal combustion engine) and can be selectively separated from this drive device by means of the clutch 3. When the clutch 3 is open, no torque is transmitted to the crankshaft 11 of the piston compressor 10, so that the crankshaft 11 stands still while the piston compressor 10 is separated from the drive device.

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 a cylinder 14 of the piston compressor 10 so that it can move axially. The crank mechanism 15, which has at least one crankshaft 11, a connecting rod 12 and a piston 13, is arranged in a crankcase 16, which is firmly connected to the cylinder 14. By rotating the crankshaft 11, the piston 13 is moved by the connecting rod 12 in the cylinder 14 so that it carries out a lifting movement.

Above the piston 13, the cylinder 14 is closed by a valve plate 20. The cylinder 14, the piston 13 and the valve plate 20 thus define the compression space 17 in the cylinder 14. An inlet valve 21 is arranged on the valve plate 20 and is arranged between an inlet line 22 and the compression space 17. The inlet line 22 is part of an inlet system 23, which sucks in fresh air from the environment through a filter (not shown) and supplies it to the compression chamber 17 via the inlet line 22 through the cylinder head (not shown). 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 designed as a check valve, which enables fresh air to be sucked into the compression chamber 17, but prevents the air sucked in via the inlet line 22 into the compression chamber 17 from flowing back.

An outlet valve 26 is also arranged on the valve plate 20 and is arranged between the compression chamber 17 and an outlet line 27. Compressed via the outlet line 27 Gas, here air, is supplied to a compressed air reservoir, not shown here. The outlet valve 26, which is also designed as a check valve, prevents compressed air from flowing back from the outlet line 27 into the compression chamber 17.

2 shows a representation of an exemplary exhaust valve 26, as is often 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 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 outlet line 27.

The outlet valve 26 has a valve tongue 26a as a valve body, which detaches from the valve seat 26b from a predetermined pressure difference between the compression chamber 17 and the outlet line 27 and enables air to flow from the compression chamber 17 into the outlet line 27. The outlet valve 26 also has a contact element 26c arranged above the outlet opening 28, against which the valve tongue 26a rests in the open state. As soon as the valve tongue 26a detaches from the valve seat 26b, the pressurized air can flow from the compression chamber 17 through the open areas on the side past the valve tongue 26a and the contact element 26c into the outlet line 27.

If contaminants from the compression chamber 17 or from the cylinder head volume 27a, which are released, for example from deposits that form due to residues in the air flowing through from the hot top of the piston 13, the valve plate 20 or the cylinder head volume 27a, get between the valve tongue 26a and the valve seat 26b , there is a risk that the outlet valve 26 will no longer close completely. In this case, compressed air can flow back from the outlet line 27 into the compression chamber 17 as soon as the pressure in the compression chamber 17 drops below the pressure in the outlet line 27. In a 12.5 bar compressed air system of a commercial vehicle, the compression chamber 17 of the piston compressor 10 can be pressurized to a pressure of up to 6 bar, for example by the air flowing back there. If the piston compressor 10 is then reconnected to the drive device, the piston compressor 10 generates an internal pressure of approximately 60 bar during the first stroke. If the compression chamber 17 can withstand this enormous internal pressure, the torque generated on the crankshaft 11 is usually far too high for the clutch 3, so that it slips, overheats and wears out at an unacceptable rate.

3 shows a schematic representation of a first exemplary piston compressor 10. The structure of the piston compressor 10 in 3 largely corresponds to the structure of the in 1 illustrated and described piston compressor 10, so that the same elements of the piston compressors 10 are designated with the same reference numerals. The following only explains the differences between the piston compressor 10 3 compared to the piston compressor 10 1 explained.

The in 3 Piston compressor 10 shown has a ventilation 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 example in 3 the control line 31a of the 2/2-way valve 31 is signal-connected to the control of the clutch 3. If 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 into an open position in order to establish a connection through which air can flow between the compression chamber 17 and the inlet system 23.

If compressed air now enters the compression chamber 17 while the piston compressor 10 is at a standstill, for example in the case of an outlet valve 26 that no longer closes tightly, pressure equalization with the inlet line 22 can take place through the opened 2/2-way valve 31. This means that no pressure can build up in the compression chamber 17, which could lead to damage to the piston compressor 10 and/or the clutch 3, particularly during the first compression stroke of the piston compressor 10 when it is put back into operation.

4 shows a schematic representation of an exemplary embodiment of a piston compressor 10 according to the invention. The structure of the piston compressor 10 in 4 largely corresponds to the structure of the in 1 illustrated and described piston compressor 10, so that the same elements of the piston compressors 10 are designated with the same reference numerals. The following only explains the differences between the piston compressor 10 4 compared to the piston compressor 10 1 explained.

The in 4 Piston compressor 10 shown has a venting device in the form of an unlockable check valve 32, which also serves as an inlet valve. This means that the unlockable check valve 32 is between the compression chamber 17 and the inlet system 23 arranged. While fresh air is being sucked in from the inlet line 22 into the compression chamber 17, the unlockable check valve 32 opens automatically due to the pressure difference applied thereto. The unlockable check valve 32 is also a switchable valve device, which, in addition to opening automatically when fresh air is sucked in, can also be switched into an open position by means of a control signal. In the exemplary embodiment in 4 the control line 32a of the unlockable check valve 32 is signal-connected to a control device, not shown. Depending on at least one predetermined parameter, such as the pressure in the compression chamber 17, the unlockable check valve 32 can thus be opened in order to establish a connection between the compression chamber 17 and the inlet line 22.

If compressed air now enters the compression chamber 17 while the piston compressor 10 is at a standstill, for example in the case of an outlet valve 26 that no longer closes tightly, the unlockable check valve 32 can be opened in order to enable pressure equalization with the inlet line 22. This means that no pressure can build up in the compression chamber 17, which could lead to damage to the piston compressor 10 and/or the clutch 3, particularly during the first compression stroke of the piston compressor 10 when it is put back into operation.

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

5 shows a schematic representation of a second exemplary piston compressor 10. The structure of the piston compressor 10 in 5 largely corresponds to the structure of the in 1 illustrated and described piston compressor 10, so that the same elements of the piston compressors 10 are designated with the same reference numerals. The following only explains the differences between the piston compressor 10 5 compared to the piston compressor 10 1 explained.

The in 5 Piston compressor 10 shown has a ventilation 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 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, 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.

If with the in 5 In the example shown, while the piston compressor 10 is at a standstill, for example in the case of an outlet valve 26 that no longer closes tightly, compressed air enters the compression chamber 17, a pressure build-up first occurs in the compression chamber 17. The resulting pressure does not reach a higher value than during a compression stroke, so that no ventilation of the compression chamber 17 is initially required. Only during the first compression stroke of the piston compressor 10 after it is put back into operation 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 clutch 3. The check valve 33 is therefore designed so that it opens a connection between the compression chamber 17 and the inlet line 21 with a sufficiently large cross section to remove 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 approximately 16 and 19 bar. An exemplary check valve 33 is therefore designed in such a way that it opens, for example, at a pressure of 20 bar in the compression chamber 17 and thus removes compressed air from the compression chamber 17.

6 shows a schematic representation of a third exemplary piston compressor 10. The structure of the piston compressor 10 in 6 largely corresponds to the structure of the in 1 illustrated and described piston compressor 10, so that the same elements of the piston compressors 10 are designated with the same reference numerals. The following only explains the differences between the piston compressor 10 6 compared to the piston compressor 10 1 explained.

The in 6 Piston compressor 10 shown has a ventilation device in the form of a ventilation channel 34, which is arranged between the compression chamber 17 and the inlet system 23. The ventilation channel 34 establishes a connection through which air can flow between the compression chamber 17 and the inlet system 23, so that when the piston compressor is at a standstill, no pressure can build up in the compression chamber 17, which is significantly above the ambient pressure.

In the in 6 In the example shown, the ventilation 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 takes place through the ventilation channel 34. If compressed air from the outlet line 27 reaches the compression chamber 17 while the piston compressor 10 is at a standstill, pressure equalization with the inlet line 22 takes place through the ventilation channel 34, as a result of which no pressure can build up in the compression chamber 17. However, the disadvantage of such a ventilation channel 34 is that it is also open during a compression stroke of the piston compressor 10 and air to be compressed escapes from the compression chamber 17 in this phase. This reduces the efficiency of the piston compressor 10. The ventilation channel 34 is therefore designed in such a way that it only has a small cross section in order to enable sufficient pressure equalization while the piston compressor 10 is at a standstill with the inlet system 23, but on the other hand has a throttling effect at high pressures, to limit the volume flow of the air removed.

7 shows a schematic representation of a fourth exemplary piston compressor 10. The structure of the piston compressor 10 in 7 largely corresponds to the structure of the in 6 illustrated and described piston compressor 10, so that the same elements of the piston compressors 10 are designated with the same reference numerals. The following only explains the differences between the piston compressor 10 7 compared to the piston compressor 10 6 explained.

In 7 A piston compressor 10 is shown, which also has a ventilation device in the form of a ventilation channel 39 which is arranged between the compression chamber 17 and the inlet system 23. A check valve in the form of a gravity ball valve 40 is arranged in the ventilation channel 39, which closes the ventilation channel 39 when the pressure in the compression chamber 17 exceeds a predetermined value, which presses the ball of the gravity ball valve 40 against its gravity on a valve seat arranged at the top of the gravity ball valve 40. The check valve restricts the escape of compressed air from the compression chamber 17 during a compression stroke.

8th shows a schematic representation of a fifth exemplary piston compressor 10. The structure of the piston compressor 10 in 8th largely corresponds to the structure of the in 6 illustrated and described piston compressor 10, so that the same elements of the piston compressors 10 are designated with the same reference numerals. The following only explains the differences between the piston compressor 10 8th compared to the piston compressor 10 6 explained.

Also the one in 8th Piston compressor 10 shown has a ventilation device in the form of a ventilation channel 35, which is arranged between the compression chamber 17 and the inlet system 23. In contrast to the piston compressor 10 6 the ventilation channel 35 is arranged in the upper region of the wall of the cylinder 14. The ventilation channel 35 also creates a connection through which air can flow 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.

As in 8th is shown, the ventilation channel 35 can be arranged approximately in the area which the upper piston ring covers approximately 60 ° before the top dead center of the piston 13. As a result, while the piston compressor 10 is at a standstill, compressed air is removed from the compression chamber 17, which reaches there 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 during the final phase of the compression stroke.

9 shows a schematic representation of a sixth exemplary piston compressor 10. The structure of the piston compressor 10 in 9 largely corresponds to the structure of the in 8th illustrated and described piston compressor 10, so that the same elements of the piston compressors 10 are designated with the same reference numerals. The following only explains the differences between the piston compressor 10 9 compared to the piston compressor 10 8th explained.

The in 9 Piston compressor 10 shown has a ventilation device in the form of a ventilation channel 36, which is arranged between the compression chamber 17 and the interior of the crankcase 16. As with the piston compressor 10 8th the ventilation channel 36 is arranged in the upper region of the wall of the cylinder 14. This creates a connection through which air can flow between the compression chamber 17 and the crankcase 16. Since the crankcase 16 of the piston compressor 10 enables pressure equalization with respect to the surroundings, there is essentially ambient pressure in its interior. This can be done via the ventilation channel 36 Pressure equalization between the compression chamber 17 and the crankcase 16 takes place.

10 shows a schematic representation of a seventh exemplary piston compressor 10. The structure of the piston compressor 10 in 10 largely corresponds to the structure of the in 9 illustrated and described piston compressor 10, so that the same elements of the piston compressors 10 are designated with the same reference numerals. The following only explains the differences between the piston compressor 10 10 compared to the piston compressor 10 9 explained.

The in 10 Piston compressor 10 shown has a ventilation device in the form of a ventilation channel 37, which corresponds to the ventilation channel 36 9 between the compression chamber 17 and the interior of the crankcase 16 is arranged. Opposite the ventilation channel 36 9 A check valve 38 is arranged in the ventilation channel 37, which prevents air from flowing back from the crankcase 16 into the compression chamber 17. The check valve 38 can be designed so that it opens 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 a pressure build-up in the compression chamber 17 during a downtime of the piston compressor 10.

11 shows a representation of a detail of a further exemplary embodiment of a piston compressor 10 according to the invention, in which the inlet valve 21 forms the ventilation device. The elements of the inlet valve 21 are in 11 shown in exploded view. The inlet valve 21 forms the upper end of the compression chamber 17 in the cylinder 14. The valve tongue 21a is designed in one piece 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.

The valve tongue 21a has a curvature which is designed in such a way that the valve tongue 21a rests on the contact element 21b from a pressure in the compression chamber 22 (dashed representation of the valve tongue 21a) which in the exemplary embodiment is 0.4 bar higher than the pressure in the inlet system 23 ( Ambient pressure) and thereby closes the valve openings 21c. At a pressure difference of less than 0.4 bar, the valve tongue 21a always has a curvature so that there is a connection between the inlet system 23 and the compression chamber 17. A 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 pressure building up in the compression chamber 17 of the compressor 10.

In another embodiment of the piston compressor 10, not shown but acting 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 opens at a predetermined pressure in this embodiment Compression chamber 17 rests sealingly on the contact element 21b.

REFERENCE SYMBOL LIST

3

coupling

10

Piston compressor

11

crankshaft

12

connecting rod

13

Pistons

14

cylinder

15

crank drive

16

crankcase

17

compression space

20

Valve plate

21

Inlet valve

21a

valve tongue

21b

Investment element

21c

Valve opening

22

Inlet pipe

23

Intake system

24

Cylinder head volume (intake)

26

outlet valve

26a

valve tongue

26b

Valve seat

26c

Investment element

27

outlet line

27a

Cylinder head volume (exhaust)

28

Exhaust opening

31

2/2 way valve

31a

Control line

32

check valve

32a

Control line

33

check valve

34

vent channel

35

vent channel

36

vent channel

37

vent channel

38

check valve

39

check valve

40

Gravity ball valve

Claims (9)

Piston compressor for compressing a gas, which can optionally be separated from a drive device by means of a clutch (3), with 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). is 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, the piston compressor (10) having a ventilation device (31, 32, 33, 34, 35 , 36, 37, 39), through which compressed gas, which passes from the outlet line (27) back into the compression chamber (17) during the separation of the piston compressor (10) from the drive device, can be removed from the compression chamber (17), characterized in that the inlet valve (21) forms the ventilation device, the inlet valve (21) being designed in such a way that a connection between the inlet line (22) and the compression chamber (17) can only be closed from a predetermined pressure in the compression chamber (17). is, wherein the predetermined pressure is at least 0.1 bar, preferably at least 0.2 bar and in particular at least 0.5 bar higher than the pressure in the inlet line (22). Piston compressor after Claim 1 , characterized in that the compressed gas can be discharged from the compression chamber (17) into an area with ambient pressure, which is from the environment itself, a gas space (22, 24) connected to an inlet system (23) or the interior of a crankcase (16) is formed. Piston compressor according to one of the preceding claims, characterized in that a switchable valve device (31, 32) forms the venting device. Piston compressor according to one of the Claims 1 or 2 , characterized in that a check valve (33) forms the ventilation device. Piston compressor according to one of the Claims 1 until 4 , characterized in that the inlet valve (21) has a concave valve seat and a flat valve tongue, so that the valve tongue only lies sealingly against the valve seat after an elastic deformation caused by the pressure in the compression chamber (17). Piston compressor according to one of the Claims 1 until 4 , characterized in that the inlet valve (21) has a flat valve seat and a curved valve tongue, so that the valve tongue only lies sealingly against the valve seat after an elastic deformation caused by the pressure in the compression chamber (17). Piston compressor according to one of the Claims 1 or 2 , characterized in that a ventilation channel (34, 35, 36, 39) forms the ventilation device. Piston compressor after Claim 7 , characterized in that at least one end of the ventilation channel (34, 35, 36, 39) is arranged in a valve plate (20) or in a cylinder wall (14). Piston compressor according to one of the Claims 7 or 8th , characterized in that a check valve (38) or a check valve (40) is arranged in the ventilation channel (34, 35, 36, 39).

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