EP2708745B1 - Multi-stage piston type compressor with idler valves to create an idle running function - Google Patents

Description

FIELD OF THE INVENTION

The present invention relates to a multi-stage piston compressor for generating compressed air with at least two cylinders, in each of which a movable piston via a crank for compressing sucked by an air filter element equipped with air duct air is arranged, wherein in each case at least one designed as a louver valve, cylinder head side arranged Inlet valve is fluidly connected to the at least two cylinders to direct the air to be compressed in the at least two cylinders, further each at least one designed as a louver valve, cylinder head side arranged exhaust valve is fluidly connected to the at least two cylinders to the compressed air from the piston to let flow out of the at least two cylinders in each case a compressed air line.

The field of application of the present invention extends primarily to the rail vehicle and commercial vehicle sector, in which reciprocating compressor for compressing ambient air, in particular in the field of compressed air operated Brake systems are used. The reciprocating compressors draw their drive energy either directly from an internal combustion engine of the vehicle or are equipped with a separate drive, usually an electric motor. In the case of use in commercial vehicles, the compressed air generated by the piston compressor is increasingly used in addition to the operation of the brake system for the operation of the air suspension system. Due to the associated large compressed air demand with high system pressures here are particularly multi-stage reciprocating compressors.

BACKGROUND OF THE INVENTION

Piston compressors are used for the compression of gases, usually air, which are used as a working medium for the operation of various aggregates. In operation, reciprocating compressors are fluidly connected to a compressed air tank, for example, so that the compressed air tank is filled with compressed air until a predeterminable pressure level is reached. At this time, a control valve disposed between the reciprocating compressor and the compressed air tank opens, so that the air supplied from the reciprocating compressor escapes.

The reciprocating compressor itself often can not be shut down because it is fixedly coupled to, for example, the vehicle engine. However, there are generally longer pressure lines between the control valve and the reciprocating compressor, so that the piston compressor still has to work against the pipeline resistance or against a certain counterpressure when the regulating valve is open. In addition, in this case occurs in multi-stage reciprocating compressors due to the usually different stroke volumes of the individual stages of the effect that the lower compression stages must perform a significant indicated work.

From the EP 1 650 434 A2 is a multi-stage piston compressor for compressing compressible media with at least one upstream and at least one downstream compressor stage out. Each compressor stage has at least one piston guided in a cylinder chamber and one inlet valve chamber connected to the cylinder chamber through an inlet valve and one outlet valve chamber connected to the cylinder chamber through an outlet valve.

In at least one upstream compressor stage, the inlet valve chamber is connected by at least one additional valve with the cylinder chamber. The additional valve is in the idle state in an open position. Upon reaching or exceeding a certain differential pressure in the outlet valve chamber or a compressor stage located furthest downstream closes this additional valve and pressure generation is possible. Conversely, the auxiliary valve opens when due to the opening of the overflow valve to the compressed air tank, the pressure in the outlet valve chamber drops.

From the well-known prior art it is apparent that in the past idler mechanisms were used in which the valve louvers were kept open by means of valve lifter jaws which had been forced through the valve slots onto the valve louvers. As a result, the closing of the valve louvers was prevented, thus reducing the delivery rate and the power consumption. However, the mechanical intervention on the sensitive valve blades is a problem because it greatly reduces the life of the valve blades.

Another way to create idling while avoiding the problem of jaws acting on the sensitive valve blades is the use of by-pass means. A valve integrated in the cylinder head is activated in order to switch a bypass, with the compressed air flowing past the valve with as little power loss as possible. The disadvantage of this solution is that the space in the cylinder head is limited and can therefore generally realize only insufficient small cross-sections. This causes the pressure relief only is incomplete and remains in idle operation too high power consumption of the compressor remains.

In general, the function of an idler device is to reduce the delivery capacity to the smallest possible amount while the piston compressor is running and to further reduce the power consumption. Idling devices find application when the reciprocating compressor can not be disconnected from the drive unit or the drive unit can not be brought to a standstill. This is particularly the case when the compressor is driven by an internal combustion engine directly by means of gear, cardan shaft or belt.

Further examples of the use of idling devices is also the start unloading to relieve an electric motor serving as drive units. In particular, if system-related short-term delivery interruptions are necessary because, for example, the compressed air can not escape quickly enough or more compressed air is needed in the foreseeable future.

DISCLOSURE OF THE INVENTION

It is therefore an object of the present invention to provide a multi-stage reciprocating compressor comprising a simple and robust idling system, which does not mechanically affect the sensitive valve blades, as large cross-sections and thus ensures complete relief in terms of power consumption and flow rate and a simple yet cost-effective Bypass function represents.

The object is achieved on the basis of a multi-stage reciprocating compressor according to the preamble of claim 1 in conjunction with its characterizing features. Advantageous developments of the invention will become apparent from the following dependent claims.

According to the invention, at least one return line leads away from the respective compressed-air line, wherein in each case one idling valve is arranged in the at least one return line in order to realize an idling function of the multi-stage reciprocating compressor. Preferably, the at least one inlet valve arranged on the cylinder head side and the at least one outlet valve arranged on the cylinder head side continue to be in operation during the idling function.

The respective idle valve has no mechanical influence on the at least one cylinder valve side arranged inlet valve and the at least one cylinder head side arranged exhaust valve. Furthermore, the respective idle valve is not mounted in the region of the cylinder heads, so that the respective idle valve is not thermally stressed by the cylinder heads. Thus, the respective idle valve can also be designed as a seal made of a polymer, since it is not exposed to high thermal stress. In addition, due to the relatively large cross-sections of the respective idle valve, a complete and rapid relief in terms of power consumption and flow rate can be ensured. In idle mode, the at least two cylinders promote the compressed air, with no back pressure and thus not only the life of the multi-stage piston compressor is greatly increased, but also the energy consumption is greatly reduced.

It is further preferred that the at least one return line opens into the air line in the section downstream of the air filter element and upstream of the at least two cylinders. The air is ideally returned to the air line in the intake of the reciprocating compressor and conveyed in a circle. Thus, the already filtered compressed air is not blown off at idle, so that no unnecessary blow-off noise. Due to lower blow-off noise, additional silencers can be saved. Furthermore, due to the air circulation, the already existing, filtered air can be used to suction prevent unfiltered air through the air filter element, wherein the air filter element is not loaded in idle. This increases the life of the air filter element.

It is further proposed that the at least one return line at least partially consists of an elastic material. According to a preferred embodiment, the at least one return line comprises a tube of a polymeric material. The hose is ideally elastic or flexible and mounted with fittings on the at least one return line. As a result, the respective idling valve is decoupled from the pulsations of the compressed air generated by the piston compressor on the one hand and from the vehicle vibrations on the other hand. The function of the respective idle valve is not affected by the aforementioned parameters, whereby a reliable function and long life is achieved.

According to a measure further improving the invention, it is proposed that an actuating device for the pneumatic or electrical actuation of the respective idle valve is arranged on the respective idle valve. Advantageously, a control unit of the actuator is assigned or integrated in this.

The invention includes the technical teaching that a heating device for heating the respective idle valve is arranged on the respective idle valve. The heating device prevents, if necessary, a freezing of the respective idle valve. Furthermore, it is also conceivable to heat the respective idle valve via the compressed air in order to prevent freezing or icing.

A cooling unit for cooling the compressed air in or on the compressed air line is preferably arranged downstream of the at least two cylinders. The respective cooling unit should advantageously be so powerful that the Air at the outlet of the cooling unit at counter pressure in continuous operation is not more than 20 ° C above the cooling air temperature.

Furthermore, a check valve is preferably arranged at the end of the compressed air line in front of a compressed air outlet in order to prevent the compressed air from flowing out. The check valve is an important element to maintain the air circulation during the idle function. Further, the check valve allows the at least two cylinders to operate in idle mode not against pressure and thus reduce wear and energy consumption without preventing the cranking operation.

It is further proposed that the respective idle valve is mechanically fastened to a suction housing comprising the air filter element and the air line. Particularly advantageous is a screwing the respective idle valve to the intake. If necessary, thus, the idle valve can be exchanged in a simple way.

Preferably, at least one separator cartridge in the at least one return line between the respective cooling unit and the respective idle valve is arranged to retain the accumulated water in the idle air. During the compression of the air, water drops in the respective cooling unit as a matter of principle. This water should not reach the subsequent stage or the intake area. The at least one separator cartridge is designed in an advantageous embodiment as Umlenkabscheider. Advantageously, the at least one separator cartridge is filled with chaotically arranged pipe sections, preferably of a copper alloy. Furthermore, the pipe sections can also be made of a corrosion-resistant steel or aluminum. Advantageously, a height of the stratification of the pipe sections is greater than the inner diameter of the separator cartridge. As it flows through the chaotically arranged pipe sections, the air is swirled, whereby the water is separated.

Furthermore, the at least one separator cartridge can have a spring-loaded filling with Raschig rings, so that a relative movement between the Raschig rings and thus the noise emissions emanating therefrom are prevented. A diameter of the at least one separator cartridge is preferably twice the diameter of the at least one return line.

According to a measure which further improves the invention, it is proposed that at least one drainage valve be arranged for the targeted discharge of water at the respective cooling unit. The at least one drainage valve is preferably an automatic drainage valve, wherein an electrically actuated solenoid valve is also conceivable. Furthermore, in one advantageous embodiment, the automatic dewatering valve is designed as a lock valve which reacts to pressure differences, so that a lock outlet is closed when pressure is applied and a lock input is opened. This allows the water to collect in the lock.

BRIEF DESCRIPTION OF THE DRAWINGS

Further, measures improving the invention will be described in more detail below together with the description of a preferred embodiment of the invention with reference to the single figure. The single FIGURE shows a schematic representation of the multi-stage piston compressor according to the invention with idle function.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

According to the single figure, the multi-stage reciprocating compressor 1 has a suction air inlet 29, whereby the ambient air is sucked. The ambient air flows through an air filter element 6 arranged in an intake housing 28, whereby particles exceeding a certain size are filtered out. The air cleaned by the air filter element 6 flows through an air line 7 which is partially arranged in the intake housing 28 and flows into the cylinder 2 via an inlet valve 8 arranged as a lamellar valve and arranged on the cylinder head side. In the cylinder 2, a piston 4 moves up and down, after which the sucked air is compressed. The air previously compressed by the piston 4 flows out of the cylinder 2 out of the cylinder 2 and into a compressed air line 12 through an exhaust valve 10 which is likewise designed as a lamellar valve and is arranged on the cylinder head side. The compressed air line 12 passes through a cooling unit 24, in which the compressed air heated by the compression is cooled and thus relaxed.

After the cooling unit 24, a return line 14 is arranged on the compressed air line 12, so that the expanded air flows partly via this return line 14 into the air line 7 in the section downstream of the air filter element 6 and upstream of the cylinder 2. In the return line 14, an idle valve 16 is arranged to realize an idling function of the multi-stage piston compressor 1. The cylinder head side arranged inlet valve 8 and the cylinder head side arranged exhaust valve 10 are still in operation during the idling function. The idle valve 16 has an actuator 20 for electrical actuation. In addition, a heating device 22 for heating the elements of the idle valve 16 is arranged on the idle valve 16. As a result, a freezing of the attached to the suction housing 28 idle valve 16 is reliably prevented. Further, an elastic tube 18 made of a polymeric material is arranged on the return line 14 in order to decouple the idle valve 16 from the pulsations of the compressed air generated by the piston compressor on the one hand and from the compressor and vehicle vibrations on the other hand. Moreover, a trap cartridge 31a is disposed in the return passage 14 between the cooling unit 24 and the idle valve 16 to retain the accumulated water in the idle air.

The partially via the compressed air line 12 flowing compressed air passes through a designed as a lamellae valve, cylinder head side inlet valve 9 into the cylinder 3. This cylinder 3 represents the second compressor stage of the multi-stage piston compressor 1. A reciprocating piston 5 compresses the inflowing Air and via a likewise designed as a lamellae valve, cylinder head side arranged outlet valve 11 flows the previously compressed air from the cylinder 3 in a compressed air line 13. Downstream of the compressed air line 13 is arranged on the compressed air line 13, a cooling unit 25 for cooling the previously compressed and thus heated air flow. A drainage valve 30 for targeted removal of water is arranged on the cooling unit 25.

At the distal end of the compressed air line 13, a compressed air outlet 26 is arranged upstream of a - not shown here - compressed air tank. Further, upstream of the compressed air outlet 26, a check valve 27 is disposed in the compressed air line 13. The check valve 27 prevents outflow of the compressed air and allows idling of the multi-stage piston compressor. 1

When the check valve 27 is closed, the compressed air flows via an outgoing from the compressed air line 13 return line 15 in the intake housing 28 located in the air line 7. Thus, the cylinder 2 and 3 operate without back pressure, so that the life of the multi-stage piston compressor 1 is greatly increased. The structure of the second compressor stage downstream return line 15 is identical to the structure of the first compressor stage downstream return line 14. Thus, the return line 15 also comprises an elastic tube 19 made of a polymeric material and an idle valve 17 which an electric actuator 21 and a heating device 23rd having. Moreover, a separator cartridge 31b is disposed in the return passage 15 between the cooling unit 25 and the idle valve 17 to retain the accumulated water in the idling air

The invention is not limited to the preferred embodiments described above. On the contrary, modifications are conceivable which are included in the scope of protection of the following claims. For example, it is also possible to control the idle valve 16 pneumatically via the actuating device 20. Preferably, the pneumatic control in rail vehicles, especially in trains. Due to the concern of a control air, the idle valve 16 is opened and relieved the multi-stage piston compressor 1 in both compressor stages, the control air is used to control the idling of the multi-stage piston compressor 1. If there is a need for air for the train's brake system, there is no control air and the multistage piston compressor 1 delivers into the compressed air reservoir. If a system pressure of preferably 10 bar is reached, the control air is applied to the idling valve 16 and the compressor is relieved. The system pressure can preferably be controlled via a pressure monitor sensor.

LIST OF REFERENCE NUMBERS

1

multistage piston compressor

2, 3

cylinder

4, 5

piston

6

Air filter element

7

air line

8, 9

intake valve

10, 11

outlet valve

12, 13

Compressed air line

14, 15

Return line

16, 17

Idle valve

18, 19

tube

20, 21

actuator

22, 23

heating device

24, 25

cooling unit

26

Compressed air outlet

27

check valve

28

suction

29

Sauglufteintritt

30

SEPARATOR

31a, 31b

drain valve

Claims (12)

1. Multi-stage piston-type compressor (1) for generation of compressed air, comprising at least two cylinders (2, 3) in which a respective piston (4, 5) movable via a crank drive system is disposed for compressing air taken in through an air passage equipped with an air filter element (6), wherein at least one respective intake valve (8, 9), which is disposed on the side of the cylinder head and configured as reed valve, is connected in fluid technology with said at least two cylinders (2, 3) for passing the air to be compressed into said at least two cylinders (2, 3), with at least one respective discharge valve (10, 11), which is disposed on the side of the cylinder head and is configured as reed valve, being moreover connected in fluid technology to said at least two cylinders (2, 3) in order to let the air compressed by said piston (4, 5) out of said at least two cylinders (2, 3) into one respective compressed-air passage (12, 13),
   characterised in that at least one return passage (14, 15) passes away from the respective compressed-air passage (12, 13), with one respective idler valve (16, 17) being disposed in said at least one return passage (14, 15) for realization of no-load running function of the multi-stage piston-type compressor (1).
2. Multi-stage piston-type compressor (1) according to Claim 1,
   characterised in that said at least one intake valve (8, 9) disposed on the side of the cylinder head and said at least one discharge valve (10, 11) disposed on the side of the cylinder head continue their operation during the no-load running function.
3. Multi-stage piston-type compressor (1) according to Claim 1,
   characterised in that said at least one return passage (14, 15) opens into the air pipe (7) in the section downstream of said air filter element (6) and upstream of said at least two cylinders (2, 3).
4. Multi-stage piston-type compressor (1) according to Claim 1,
   characterised in that said at least one return passage (14, 15) consists, at least in parts, of an elastic material.
5. Multi-stage piston-type compressor (1) according to Claim 4,
   characterised in that said at least one return passage (14, 15) includes a tube (18, 19) made of a polymer material.
6. Multi-stage piston-type compressor (1) according to Claim 1,
   characterised in that an operating means (20, 21) for pneumatic or electric actuation of the respective idler valve (16, 17) is disposed at the respective idler valve (16, 17).
7. Multi-stage piston-type compressor (1) according to Claim 1,
   characterised in that a heating means (22, 23) is disposed on the respective idler valve (16, 17) for heating the respective idler valve (16, 17).
8. Multi-stage piston-type compressor (1) according to Claim 1,
   characterised in that one respective cooling unit (24, 25) is disposed in or on said compressed air passage downstream of said at least two cylinders (2, 3) for cooling the compressed air.
9. Multi-stage piston-type compressor (1) according to Claim 1,
   characterised in that a non-return valve (27) is disposed at the end of said compressed-air passage (12) in front of a compressed-air discharge opening (26) in order to prevent compressed air from being discharged.
10. Multi-stage piston-type compressor (1) according to Claim 1,
    characterised in that the respective idler valve (16, 17) is mechanically fastened on an intake housing (28) including said air filter element (6) and said air passage (7).
11. Multi-stage piston-type compressor (1) according to Claim 1,
    characterised in that at least one separator cartridge (31 a, 31 b) is disposed in said at least one return passage (14, 15) between the respective cooling unit (24, 25) and the respective idler valve (16, 17) for retaining the water produced there in the idling-function air.
12. Multi-stage piston-type compressor (1) according to Claim 1,
    characterised in that at least one draining valve (30) is disposed on the respective cooling unit (24, 25) for the targeted discharge of water.

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