Valve device for a reciprocating piston compressor

Abstract

An embodiment according to the invention is a reciprocating piston compressor for a compressed air supply system in a motor vehicle, which has a cylinder head in which a pressure relief system is integrated, and by means of which a pressure relief passage in a valve seat plate can be switched, the pressure relief passage connecting the working chamber of the reciprocating piston compressor to a space in the cylinder head. In order to improve the efficiency of the reciprocating piston compressor, it is proposed here that the pressure relief system includes a switching device and a plate, wherein the plate is fixed to the valve seat plate on the working chamber side and is designed to be lifted from the valve seat plate in order to open the pressure relief passage, and wherein the lifting of the plate can be carried out automatically and / or controlled by the pressure relief system.

Description

Technical Field

[0001] The present invention relates to a reciprocating piston compressor for a compressed air supply system in a motor vehicle such as a truck, a bus or a rail vehicle. The reciprocating piston compressor mainly comprises two regions, namely a cylinder head region in which valves are arranged and a crankcase having at least one cylinder, and the cylinder can move in a working chamber, thereby generating a suction stroke motion and a compression stroke motion. The reciprocating piston compressor can be designed as single-stage or multi-stage, in particular two-stage. Background Art

[0002] Valve devices for controlling the air flow are usually assigned to the cylinder head and comprise automatically effective suction valves and pressure valves, which are opened and closed by the pressure present in the working chamber due to the reciprocating movement of the piston.

[0003] The suction stroke of the piston generates a negative pressure in the working chamber of the corresponding cylinder, so that the associated suction valve is opened and the associated pressure valve is closed. Air enters the working chamber of the cylinder or is sucked into the working chamber through an intake chamber and an intake passage in the valve seat plate.

[0004] The compression stroke of the piston causes an overpressure in the working chamber of the corresponding cylinder, so that the associated suction valve closes and the associated pressure valve opens, whereby compressed air is conveyed from the working chamber of the cylinder to a downstream compressed air system through a pressure passage.

[0005] It is also known from document DE 10 2016 006 358 A1 that the suction valve is usually designed as a valve disc, the valve tongue of which is clamped on one side between the cylinder housing and the cylinder head of a reciprocating piston compressor and is guided in a cutout of the cylinder housing at its free end by means of at least one connecting plate. The intake port in the valve seat plate, which connects the intake chamber to the working chamber of the cylinder, can be closed by the valve tongue. In addition, the valve disc is designed such that at least one exhaust port is left free in the valve seat plate, which is arranged between the working chamber of the cylinder and the pressure passage. The pressure valve is usually located in the cylinder head region, and the exhaust port can be closed by means of this pressure valve.

[0006] The delivery operation of the reciprocating piston compressor is carried out for so long until the pressure in the main pressure line has reached a predetermined cut-off pressure. Subsequently, the compressor is switched to idling operation, thereby reducing the power consumption during idling operation. Such a system is also referred to as a pressure relief system or an idling system.

[0007] An unload valve is known, for example, from document EP 1 650 434 A2, which automatically opens once the system pressure has been reached and the pressure relief valve has opened. This cancels the back pressure in the compressed air system that holds the unload valve in the closed position. The opened unload valve connects the working chamber to the intake chamber, so that no compression occurs during the compression stroke. The advantage of such a piston compressor is that it automatically switches off when the target filling pressure in the pressure vessel has been reached.

[0008] For example, a further unload valve is known from document DE 10 2013 001 147 A1. An unload valve for a pressure relief system is proposed here, which is held in the closed position by a spring and can optionally be switched to the open position by applying pressure. Such a system is also referred to as an "external control system".

[0009] An unload valve device is also known from document EP 0091 994. The unload valve device is arranged so as not to protrude into the area beyond the compressor piston.

[0010] The common feature of all unload systems is that during unload operation, the working chamber is connected to another space via a pressure relief passage, so that no compression or reduced compression occurs. Summary of the Invention

[0011] The technical problem to be solved by the present invention is to provide a pressure relief system by means of which the energy consumption of a reciprocating piston compressor can be further reduced.

[0012] This technical problem is solved according to the invention by a reciprocating piston compressor for a compressed air supply system in a motor vehicle. The reciprocating piston compressor has a cylinder head and a pressure relief system integrated in the cylinder head. The cylinder head includes a valve seat plate and an intake valve plate. The intake chamber can be connected to the working chamber via the intake valve plate through a plurality of intake channels in the valve seat plate. The pressure relief channels in the valve seat plate can be switched by the pressure relief system. The pressure relief channels connect the working chamber to a space in the cylinder head. Wherein, the pressure relief system includes a switching device and a plate. And wherein, the plate is fixed to the valve seat plate on the working chamber side and can be lifted from the valve seat plate to open the pressure relief channels. It is stipulated that the pressure relief channels establish an air-conducting connection between the intake chamber and the working chamber, and the lifting of the plate can be carried out automatically and / or controlled by the pressure relief system. Wherein, a part of the plurality of channel openings passing through the valve seat plate in the region of the intake chamber, namely the outer semi-circle, are the intake channels. These intake channels belong to the intake valve with the intake valve plate. During the intake stroke, air is sucked into the working chamber through the intake channels, and the intake valve plate moves to the open position. And during the compression stroke, the intake valve plate closes the intake channels. The passage of the pressure relief channels arranged within the semi-circle of the intake channels can be switched by the plate of the pressure relief system.

[0013] An embodiment according to the invention is a reciprocating piston compressor for a compressed air supply system in a motor vehicle, which has a cylinder head in which a pressure relief system is integrated. The pressure relief channels in the valve seat plate of the cylinder head can be switched by the pressure relief system. The pressure relief channels connect the working chamber of the reciprocating piston compressor to a space in the cylinder head.

[0014] In order to improve the efficiency of the reciprocating piston compressor, it is proposed here that the pressure relief system includes a switching device and a plate. Wherein, the plate is fixed to the valve seat plate on the working chamber side and is designed to be able to be lifted from the valve seat plate to open the pressure relief channels. The lifting of the plate can be carried out automatically and / or controlled by the pressure relief system.

[0015] The effective channel cross-section is enlarged by the automatic lifting of the plate. The inflow resistance of air entering the working chamber during the intake stroke of the cylinder is reduced by this enlarged effective channel cross-section.

[0016] The controlled lifting of the plate enables the compressor to be switched to no-load operation without compression.

[0017] Preferred embodiments may provide that the cylinder head has an intake chamber which can be connected to the working chamber via a valve seat plate and a plurality of intake channels in an automatically actuating intake valve designed as a reed valve, wherein at least one pressure relief channel is arranged in the intake channel. In other words, at least one pressure relief channel is surrounded by the intake channel.

[0018] Here, the plate can preferably be designed as a reed valve, where a reed valve is understood to be such a plate which is clamped on one side and closes the channel in the non-actuated position and opens a passage through the channel in the actuated position.

[0019] Preferably, the intake chamber can be connected to the working chamber via the intake channel and the pressure relief channel. The intake chamber is connected to an air inlet, in particular ambient air enters the intake chamber through this air inlet. In the intake chamber, the air is distributed over the intake channel and at least one pressure relief channel and is sucked into the working chamber through the intake channel and the pressure relief channel. The suction stroke movement of the piston is facilitated by the enlarged cross-section, thereby reducing the energy consumption.

[0020] Furthermore, the pressure relief system for supporting the plate can include means for restricting the lifting of the plate. In particular, in the case where a large amount of air is sucked into the working chamber due to the negative pressure generated during the suction stroke, it may be necessary to restrict the movement of the plate, which is also necessary for valve plates according to the prior art. In order to restrict the lifting of the plate, for example, a limiting piece protruding into the working chamber can be used. In order to still keep the dead zone relatively small, the cylinder can have a corresponding clearance for the limiting piece. Alternatively, this clearance can also directly serve as a means for restriction, such that the plate hits the clearance at least at the beginning of the lifting movement.

[0021] Furthermore, the pressure relief system can include a pressure relief piston which can be reset by a spring element and which can be actuated by means of a control pressure.

[0022] In a further embodiment, the reciprocating piston compressor can be designed as a two-stage compressor having a low-pressure stage and a high-pressure stage, wherein in the cylinder head a pressure relief system and a connecting channel are provided for each stage, and the connecting channel connects the pressure relief channel of the high-pressure stage to the intake chamber of the low-pressure stage. For a multi-stage compressor, the pressure relief during the compression stroke of all stages is achieved by such a connecting device which connects the respective working chamber to the intake chamber in a controlled manner via a pressure relief channel. Thus, in the pressure relief position of the plate, even during the suction stroke of the high-pressure stage, ambient air can directly enter the working chamber.

[0023] The plates of the pressure relief system of the high-pressure stage are designed such that, compared to the plates of the pre-stage, they remain in the closed position during the suction stroke during operation. The plates of this high-pressure stage or of subsequent high-pressure stages are thus designed such that the plates can only be actively moved into the open position by the pistons of the pressure relief system.

[0024] Furthermore, a method for operating a reciprocating piston compressor in order to generate compressed air for a commercial vehicle is proposed. The reciprocating piston compressor has a cylinder head in which a pressure relief system is integrated, by means of which a pressure relief passage in a valve seat plate of the cylinder head can be switched, the pressure relief passage connecting the working chamber of the reciprocating piston compressor to a space in the cylinder head.

[0025] The method is characterized in that a negative pressure is generated in the working chamber during the suction stroke, during which the plate of the pressure relief system is automatically or forcibly moved into the open position when the pressure relief system is actuated, so that additional air is sucked into the working chamber through the intake chamber and the pressure relief passage, or air can be pressed out of the working chamber through the pressure relief passage when the pressure relief system is operated. The method is applied to a single-stage reciprocating piston compressor or to the pre-stage or first stage of a multi-stage reciprocating piston compressor.

[0026] In the case of a reciprocating piston compressor designed as a two-stage compressor, the pre-stage and the high-pressure stage are connected in series, wherein a pressure relief system is provided for each stage in the cylinder head. In this configuration, the plate of the pre-stage is automatically moved into the open position during the suction stroke, and the plate of the high-pressure stage is designed such that the high-pressure stage remains in the closed position during the suction stroke.

[0027] Furthermore, a connection passage for connecting a plurality of pressure relief systems is provided in the cylinder head of the two-stage compressor, wherein the pressure relief passage of the high-pressure stage is connected to the intake chamber of the pre-stage through the connection passage, and wherein, in order to relieve the pressure of the reciprocating piston compressor or to switch to the no-load operation of the reciprocating piston compressor, the pressure relief pistons of the two pressure relief systems are switched such that the plates of the two stages are moved into the open position. Description of the Drawings

[0028] The invention is explained in detail below on the basis of embodiments. In the drawings:

[0029] Figure 1 A piston-side view of the valve plate of a two-stage reciprocating piston compressor with a pressure relief system is shown;

[0030] Figure 2 A cylinder head-side view of the valve plate of a two-stage reciprocating piston compressor with a pressure relief system is shown;

[0031] Figure 3Cross-sectional view of a pressure relief system for a first compressor stage;

[0032] Figure 4 Cross-sectional view of a pressure relief system for a second compressor stage. DETAILED DESCRIPTION

[0033] Figure 1 View of the valve seat plate 4 of a two-stage reciprocating piston compressor with a pressure relief system on the piston side, which valve seat plate is assigned to the cylinder head 12. The two compressor stages, namely the front stage 2 and the high-pressure stage 3, are constructed similarly, but slightly different in terms of size and function. The basic structure is the same. Both compressor stages have intake valves 5a, b, which are fixed on one side and have a stop surface on the opposite side. In the crankcase 11, there are cutouts (not shown here) for the stop surfaces, and the opening movement of the intake valves 5a, b is limited by these cutouts. The exhaust channels 23 are arranged within the outer contour of the intake valves 5a, b and partly extend through the cutouts in the intake valves 5a, b. The plates 9a, b belonging to the pressure relief systems 7a, b are arranged approximately in the middle of the intake valves 5a, b, i.e., approximately in the middle of the working chambers of the cylinders 20a, b, where the intake valves 5a, b have cutouts. The plates 9a, b are also clamped on one side.

[0034] Due to the different functions of the pressure relief systems 7a, b, the valves of the front stage 2 and the high-pressure stage 3 are slightly different. Since the volume of air to be inhaled during the suction stroke of the cylinder 20a of the front stage 2 is larger, the plate 9a is designed such that it automatically opens during each suction stroke of the cylinder 20a of the front stage 2. A limiting piece 22 is provided to limit the opening movement, which limiting piece represents a stop for the plate 9a.

[0035] Figure 2 View of the valve seat plate 4 of a two-stage reciprocating piston compressor with a pressure relief system on the cylinder head side. In this view, the channels and chambers of these compressor stages can be clearly seen. The two stages 2, 3 each have an intake chamber 14a, b and an exhaust chamber 15a, b. In the exhaust chambers, automatically acting exhaust valves 6a, b are arranged, which close the exhaust channels 23 in the valve seat plate in the closed position and are moved to the open position when a determinable pressure in the working chamber is exceeded.

[0036] In the region of the intake chamber 14a of the pre-stage 2, a plurality of channel openings passing through the valve seat plate 4 are shown. A part of these openings, namely the outer semi-circle, are the intake channels 21a, and these intake channels are assigned to the intake valve 5a having the intake valve flap 18a. During the intake stroke, air is drawn into the working chamber through the intake channels 21a, and the intake valve flap 18a moves to the open position. During the compression stroke, the intake valve flap 18a closes the intake channels 21a. The pressure relief channel 19a is arranged within the semi-circle of the intake channel 21a. The passage of the pressure relief channel is switched by the plate 9a of the pressure relief system 7a.

[0037] The design of the high-pressure stage is slightly different. Here, the pressure relief channel 19b of the pressure relief system 7b is arranged in a separate chamber, and this chamber is connected to the intake chamber 14a of the pre-stage 2 through the connecting channel 13. The separate channel connection between the exhaust chamber 15a of the pre-stage 2 and the intake chamber 14b of the high-pressure stage 3 is not shown.

[0038] Figure 3 and Figure 4 A sectional view of the pressure relief systems 7a, b of the pre-stage 2 and the high-pressure stage 3 is shown. The general layered structure of the cylinder head 12 is known in the prior art, so only the channels and chambers important for the present invention are further considered here. The pressure relief system 7a for the pre-stage according to the present invention is shown in Figure 3 and the pressure relief system 7b for the high-pressure stage 3 is shown in Figure 4 .

[0039] The pressure relief system 7a of the pre-stage described above and shown in Figure 3 can be used in a single-stage compressor. In the case of a multi-stage, i.e., more than two stages, all stages after the pre-stage obtain the pressure relief system 7b of the high-pressure stage 2, and in a preferred embodiment, a connecting channel can be provided through which all stages can be connected to the intake chamber of the pre-stage. Alternatively, each stage can also include a separate channel connected to the environment.

[0040] The special feature of the pressure relief valve of the pre-stage 2 is the limiting piece 22, which is designed as a solid member and supports the plate 9a, so that the plate 9a does not bend too much into the working chamber and thus generate excessive bending stress. The cylinder 20a has a void on the end face, and when the cylinder is at the top dead center, the limiting piece 22 is immersed in this void, so that the harmful space becomes as small as possible.

[0041] The size of the void exactly accommodates the limiting piece 22 and the plate 9a located on the limiting piece in the open state.

[0042] Furthermore, the pressure relief piston 10a can be seen, which is guided in the cylinder head 12. In the position shown, the pressure relief piston is in the rest position and is held in this position by a spring. By means of the control pressure channel 16 shown, a pressure action can be exerted on the pressure relief piston 10a, so that the pressure relief piston is moved into the pressure relief position and the plate 9a is moved into the open position.

[0043] What is special about the pressure relief system 8b shown in Figure 4 the high-pressure stage 3 is the design of the plate 9b, which is designed so spring-rigidly that the plate can only be moved into the open position by means of the pressure relief piston 10b. The suction stroke of the piston 20b of the high-pressure stage 2 does not cause the plate 9b to automatically move into the open position. The two pressure relief pistons 10a, b are simultaneously acted upon with compressed air via the control pressure channel 16 shown. The piston 20b also has a recess in which the plate 9b is received in the open position.

[0044] List of reference numerals

[0045] 1 Reciprocating piston compressor

[0046] 2 Low-pressure stage

[0047] 3 High-pressure stage

[0048] 4 Valve seat plate

[0049] 5a, b Intake valve

[0050] 6a, b Exhaust valve

[0051] 7a, b Pressure relief system

[0052] 8a, b Switching device

[0053] 9a, b Plate

[0054] 10a, b Pressure relief piston

[0055] 11 Crankcase

[0056] 12 Cylinder head

[0057] 13 Connecting channel

[0058] 14a, b Intake chamber

[0059] 15a, b Exhaust chamber

[0060] 16 Control pressure channel

[0061] 17 Cooling channel

[0062] 18a, b Intake valve plate

[0063] 19a, b Pressure relief channel

[0064] Pistons in working chambers 20a and 20b

[0065] Intake channels 21a and 21b

[0066] Restricting plates 22

[0067] Exhaust channels 23

[0068] Inlets for ambient air 24

Claims

1. A reciprocating piston compressor (1) for a compressed air supply system in a motor vehicle, the reciprocating piston compressor having a cylinder head (12) and a pressure relief system (7a, b) integrated in the cylinder head (12), the cylinder head including a valve seat plate (4) and intake valve plates (18a, b), an intake chamber (14a, b) being connectable to a working chamber via the intake valve plates through a plurality of intake channels (21a, b) in the valve seat plate (4), and a pressure relief channel (19a, b) in the valve seat plate (4) being switchable by the pressure relief system, the pressure relief channel connecting the working chamber to a space in the cylinder head (12). Wherein, the pressure relief system (7a, b) includes switching means (8a, b) and plates (9a, b), and wherein the plates (9a, b) are fixed on the valve seat plate (4) on the working chamber side and can be lifted from the valve seat plate (4) to open the pressure relief channels (19a, b), characterized in that the pressure relief channels (19a, b) establish an air-conducting connection between the intake chamber (14a, b) and the working chamber, and the lifting of the plates (9a, b) can be carried out automatically and / or controlled by the pressure relief system (7a, b), wherein a part of a plurality of channel openings passing through the valve seat plate (4) in the region of the intake chamber (14a), namely the outer semi-circle, are the intake channels (21a), these intake channels being assigned to an intake valve (5a) having an intake valve plate (18a), wherein during the suction stroke, air is sucked into the working chamber through the intake channels (21a), the intake valve plate (18a) moving to an open position, and wherein during the compression stroke, the intake valve plate (18a) closes the intake channels (21a), and wherein the passage of the pressure relief channel (19a) arranged within the semi-circle of the intake channel (21a) can be switched by the plate (9a) of the pressure relief system (7a).

2. The reciprocating piston compressor (1) according to claim 1, characterized in that, the intake valve plates (18a, b) have cut-outs, and at least one pressure relief channel (19a, b) and a plate (9a, b) are arranged within the cut-outs.

3. The reciprocating piston compressor (1) according to claim 2, characterized in that, the plates (9a, b) are designed as reed valves.

4. The reciprocating piston compressor (1) according to claim 2, characterized in that, the pressure relief system (7a, b) for supporting the plates (9a, b) includes means for restricting the lifting of the plates (9a, b).

5. The reciprocating piston compressor (1) according to claim 4, characterized in that, the means for restricting the lifting of the plate (9a) is a limiting piece (22) protruding into the working chamber.

6. The reciprocating piston compressor (1) according to claim 1, characterized in that, the pressure relief system (7a, b) includes pressure relief pistons (10a, b) which are resettable by spring elements, and the pressure relief pistons can be actuated by means of a control pressure.

7. The reciprocating piston compressor (1) according to claim 1, characterized in that, the reciprocating piston compressor (1) is designed as a two-stage compressor having a pre-stage (2) and a high-pressure stage (3), wherein in the cylinder head (12) a pressure relief system (7a, b) and a connection passage (13) are provided for each stage, and the connection passage connects the pressure relief passage (19b) of the high-pressure stage (3) to the intake chamber (14a) of the pre-stage (2).

8. The reciprocating piston compressor (1) according to claim 7, characterized in that, the pressure relief system (7b) of the high-pressure stage (3) has a plate (9b) which is designed such that the plate (9b) remains in the closed position during the suction stroke during operation.

9. A method of operating a reciprocating piston compressor (1) according to any one of claims 1 to 8 for generating compressed air for a commercial vehicle, wherein, the reciprocating piston compressor (1) has a cylinder head (12) in which a pressure relief system (7a, b) is integrated, and the pressure relief passages (19a, b) in the valve seat plate (4) of the cylinder head (12) can be switched by means of the pressure relief system, and the pressure relief passages connect the working chamber of the reciprocating piston compressor (1) to a space in the cylinder head (12), characterized in that a negative pressure is generated in the working chamber during the suction stroke, and during this suction stroke the plate (9a) of the pressure relief system (7a) is automatically or forcibly moved to the open position when the pressure relief system (7a) is actuated, so that air is sucked into the working chamber through the intake chamber (14a) and the pressure relief passage (19a), or during the compression stroke the air can be pressed out of the working chamber through the pressure relief passage (19a) and into the intake chamber (14a).

10. The method according to claim 9, characterized in that, the reciprocating piston compressor (1) is designed as a two-stage compressor having a pre-stage (2) and a high-pressure stage (3), wherein in the cylinder head (12) a pressure relief system (7a, b) is provided for each stage (2, 3), wherein the plate (9a) of the pre-stage (2) is automatically moved to the open position during the suction stroke, and the plate (9b) of the high-pressure stage (3) is designed such that the high-pressure stage remains in the closed position during the suction stroke.

11. The method according to claim 10, characterized in that, this two-stage compressor is provided in the cylinder head (12) with a connection passage (13) for connecting a plurality of pressure relief systems (7a, b), wherein the pressure relief passage (19b) of the high-pressure stage (3) is connected to the intake chamber (14a) of the pre-stage (2) through the connection passage (13), and wherein in order to relieve the pressure of the reciprocating piston compressor (1), the pressure relief pistons (10a, b) of the two pressure relief systems (7a, b) are switched such that the plates (9a, b) of the two stages (2, 3) are moved to the open position.

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