DE102017219341A1 - piston compressor - Google Patents

Abstract

The invention relates to a reciprocating compressor (1) for compressing a working fluid, in particular a liquid or gaseous fuel, comprising a piston (4) reciprocating in a bore (2) of a cylinder (3) and forming a piston within the bore (2) limited with the working fluid fillable compression chamber (5). According to the invention, an encircling annular groove (6) is formed on the inner circumference side in the cylinder (3), in which a leakage minimizing sleeve (7) is accommodated, which together with the cylinder (3) defines an annular pressure chamber (8) which is hydraulically connected to the compression space (5) is connected, so that in the pressure chamber (8) the same pressure as in the compression chamber (5) prevails and between the piston (4) and the Leckageminimierungshülse (7) across the entire pressure range across a gap and thus maintain a certain flow in the gap ,

Description

The invention relates to a reciprocating compressor for compressing a working fluid having the features of the preamble of claim 1.

The working fluid may in particular be a liquid or leakage minimizing sleeve fuel, such as natural gas (NG). If the natural gas is used for operating an internal combustion engine of a motor vehicle, it is usually carried on board the motor vehicle in liquid form ("liquefied natural gas" = LNG) in a tank. Before the natural gas is injected into a combustion chamber of the internal combustion engine, it is compressed. Here is a preferred application of the presently proposed reciprocating compressor to see.

In addition, the proposed reciprocating compressor can be used for compressing any gaseous and / or liquid media, so that the presently selected term "reciprocating compressor" also includes piston pumps.

State of the art

From the WO 2003/010446 A1 For example, a reciprocating compressor for compressing a refrigerant gas, which comprises a cylinder and a reciprocating piston in the cylinder. The cylinder and the piston define a compression chamber. The piston is connected to a drive mechanism, the connection being via pins received in radial holes of the piston. Since the radial holes are hydraulically connected to the compression chamber via a radial gap remaining between the piston and the cylinder, it is necessary to seal the radial holes. The sealing takes place via sealing elements received in the radial holes. In this way, a leakage of the cooling gas through the radial holes is counteracted.

The present invention has for its object to provide a reciprocating compressor, which has an improved efficiency. To achieve this, the leakage in the region of an annular gap between the piston and the cylinder of the reciprocating compressor should be minimized. The reciprocating compressor should in this way also be suitable for compressing a liquid or gaseous fuel, such as natural gas, to high pressure (preferably about 600 bar).

To solve the problem, the reciprocating compressor is proposed with the features of claim 1. Advantageous developments of the invention can be found in the dependent claims.

Disclosure of the invention

The piston compressor proposed for compressing a working fluid, in particular a liquid or gaseous fuel, comprises a piston which can be moved back and forth in a bore of a cylinder and which delimits within the bore a compression space which can be filled with the working fluid. According to the invention, an encircling annular groove is formed on the inner circumference side in the cylinder, in which a leakage minimizing sleeve is accommodated, which together with the cylinder defines an annular pressure chamber which is hydraulically connected to the compression space. The pressure in the pressure chamber is therefore the same as in the compression chamber. Between the piston and the leakage minimizing sleeve a gap and thus a certain flow in the gap is maintained over the entire pressure range.

The stroke of the piston causes compression of the trapped working fluid in the compression space. This means that the pressure in the compression chamber increases. At the same time, the pressure in the pressure chamber hydraulically connected to the pressure chamber increases. Since the pressure on the outside of the leakage minimizing sleeve is greater than the inside, the sleeve contracts, causing the gap remaining between the piston and the leakage minimizing sleeve to decrease. With the reduction of the gap also decreases the leakage over the gap, so that in this way an increase in the efficiency of the reciprocating compressor is achieved.

The contraction of the leakage minimization sleeve is proportional to the pressure increase in the compression chamber or in the pressure chamber. This means that as the pressure increases, so does the contraction. This is due to the constant pressure in the longitudinal direction in the pressure chamber, while in the gap between the Leckageminimierungshülse and the piston in the longitudinal direction sets an (approximately) linear pressure drop. The desired effect of gap minimization is thus given over the entire pressure range.

The contraction of the leakage minimization sleeve is further facilitated by the fact that the inner peripheral surface is smaller than the outer peripheral surface of the sleeve, so that radially outward on the leakage minimization sleeve already due to the larger area a larger pressure force acts.

The leakage minimization sleeve is to be distinguished from a conventional sealing sleeve. Because through the sleeve no seal, but only a gap minimization is achieved. This means that a certain flow is maintained in the gap. That way you can Friction losses are minimized. Preferably, therefore, the inner diameter of the Leckageminimierungshülse is chosen over the entire length greater than the outer diameter of the piston, so that wear and clamps are reduced to a minimum.

In addition, the leakage minimization sleeve allows compensation of any production-related diameter tolerances, so that at the same time the production of the reciprocating compressor is simplified.

Preferably, the annular groove is arranged at least in sections at the level of the piston on the inner circumference side in the cylinder in order to effect the desired minimization of leakage by minimizing the gap between the piston and the leakage minimizing sleeve accommodated in the annular groove.

Further preferably, the annular groove has a height H ₁ , which is greater than a height H _{2 of} the leakage minimization sleeve. This means that an axial gap remains between the leakage minimization sleeve and the cylinder, via which the required hydraulic connection of the pressure chamber with the compression space can be established. At the other end, the leakage minimizing sleeve preferably rests sealingly against the cylinder, so that circumvention of the leakage minimizing sleeve is precluded.

In a further development of the invention, it is proposed that a spring element be received in the annular groove, by means of which the leakage minimizing sleeve is axially biased against the cylinder. Due to the axial bias, the leakage minimizing sleeve is fixed in position in the axial direction, so that circumvention of the leakage minimization sleeve is permanently excluded. The biasing force also serves as an initial sealing force in the axial direction.

For axial prestressing of the leakage minimizing sleeve, it is proposed that the spring element is supported on an end face of the leakage minimizing sleeve. As a spring element, for example, a helical compression spring, a wave spring or a plate spring can be used which is inserted into the annular groove, and preferably in the remaining between the leakage minimization sleeve and the cylinder axial gap. On the specific design of the spring element is to ensure that the required hydraulic connection of the pressure chamber is not interrupted or impaired with the compression space.

Alternatively, the spring element may be formed as a double collar sleeve having a radially outwardly projecting first collar for axial support on the cylinder and a radially inwardly projecting second collar for axial support on the Leckageminimierungshülse. About the collar bush, the leakage minimization sleeve is also fixed in its axial position. In order to achieve at the same time an axial bias of the leakage minimization sleeve, it is proposed that the second collar of the collar bush is designed in the manner of a spring arm and rests only on an annular contour on the end face of the Leckageminimierungshülse. About the Federarmartig formed second collar then the axial biasing force can be applied.

Preferably, the leakage minimization sleeve for support on the cylinder has a frontally arranged, substantially planar annular contact surface, which is adjoined radially inwardly by a cone. Via the cone, the footprint is reduced, which is thus smaller than the end face at the other end of the Leckageminimierungshülse. By reducing the footprint an improved sealing effect can be achieved. Preferably, the cone in the radial direction has a width b which is greater than a width a of the contact surface, so that the contact surface is significantly reduced. The ratio of the width a to the width b is preferably 3: 1. In this way, a defined local footprint is created.

In addition, the area opposite the footprint of the leakage minimizing sleeve may be formed on the cylinder such that the contact area between the leakage minimizing sleeve and the cylinder is reduced. In this case, the end face of the leakage minimizing sleeve can also be made flat.

The pressure applied to the end face of the leakage minimization sleeve facing the compression space leads to a hydraulic pressure force which presses the leakage minimization sleeve against the cylinder. Since no compression space pressure is applied to the other end face of the leakage minimizing sleeve, at least in the area radially inside the contact area with the cylinder or the contact area, the leakage minimization sleeve is held in contact with the cylinder in this manner. Due to the force difference existing in the axial direction, a spring element for axial prestressing of the leakage minimizing sleeve may possibly be dispensed with altogether.

Advantageously, the cylinder is designed in several parts and comprises at least one upper part and a lower part, which are preferably placed axially in the region of the annular groove. The multi-part design facilitates the production of the annular groove, in particular, when the annular groove in only one part, preferably in the upper part, must be formed. In addition, the annular groove can be formed as a frontally open groove, by attaching the other part, preferably the lower part in the axial Direction is closed. Before joining the two parts, the spring element and the leakage minimizing sleeve are inserted into the annular groove. The multi-part design of the cylinder thus simplifies the assembly of the reciprocating compressor.

Furthermore, it is proposed that the compression space can be connected via an inlet valve to a fluid supply and / or via an outlet valve to a pressure line. The working fluid enters the compression chamber via the inlet valve, where it is compressed by means of the piston stroke. The compressed working fluid can then be fed via the outlet valve and the subsequent pressure line to a fluid reservoir, which is preferably a high-pressure accumulator for a liquid or gaseous fuel, such as natural gas, which is injected under high pressure into the combustion chamber of an internal combustion engine. Because of the reduced leakage over the remaining between the piston and the cylinder annular gap high pressures in the compression chamber can be achieved, so that the proposed reciprocating compressor is particularly suitable as an LNG compressor for mobile application in a motor vehicle.

• 1 eine schematische Schnittansicht eines erfindungsgemäßen Kolbenverdichters gemäß einer ersten bevorzugten Ausführungsform,
• 2 einen vergrößerten Ausschnitt der 1 im Bereich der im Zylinder ausgebildeten Ringnut,
• 3 einen vergrößerten Ausschnitt der 2 im Bereich der Abstützung des Federelements an der Leckageminimierungshülse,
• 4 einen vergrößerten Ausschnitt der 2 im Bereich der Abstützung der Leckageminimierungshülse am Zylinder,
• 5 einen schematischen Längsschnitt durch einen erfindungsgemäßen Kolbenverdichter gemäß einer zweiten bevorzugten Ausführungsform (beschränkt auf den Bereich der Ringnut),
• 6 einen schematischen Längsschnitt durch einen erfindungsgemäßen Kolbenverdichter gemäß einer dritten bevorzugten Ausführungsform (beschränkt auf den Bereich der Ringnut) und
• 7 einen schematischen Längsschnitt durch einen erfindungsgemäßen Kolbenverdichter gemäß einer vierten bevorzugten Ausführungsform.

Preferred embodiments of the invention are explained below with reference to the accompanying drawings. These show:

• 1 a schematic sectional view of a piston compressor according to the invention according to a first preferred embodiment,
• 2 an enlarged section of the 1 in the region of the annular groove formed in the cylinder,
• 3 an enlarged section of the 2 in the area of support of the spring element on the leakage minimizing sleeve,
• 4 an enlarged section of the 2 in the area of support of the leakage minimizing sleeve on the cylinder,
• 5 a schematic longitudinal section through a piston compressor according to the invention according to a second preferred embodiment (limited to the region of the annular groove),
• 6 a schematic longitudinal section through a piston compressor according to the invention according to a third preferred embodiment (limited to the region of the annular groove) and
• 7 a schematic longitudinal section through a piston compressor according to the invention according to a fourth preferred embodiment.

Detailed description of the drawings

The Indian 1 illustrated piston compressor according to the invention 1 includes a cylinder 3 with a hole 2 in which a piston 4 is moved back and forth (see arrow 20 ). The piston 4 limited within the hole 2 a compression room 5 that has an inlet valve 16 with a fluid supply 17 can be connected or filled with a working medium. After the working fluid in the compression chamber 5 through a stroke of the piston 4 It can be compressed via an outlet valve 18 a pressure line 19 be supplied. To the pressure line 13 a fluid reservoir (not shown) may be connected.

To the leakage from the compression space 5 over an annular gap 24 to reduce that between the piston 4 and the cylinder 3 remains, the cylinder points 3 at the height of the piston 4 inner circumferential side a circumferential annular groove 6 in which a leakage minimization sleeve 7 is included. The leakage minimization sleeve 7 limited to the cylinder 3 an annular pressure chamber 8th that with the compression space 5 is hydraulically connected, so that radially outward on the Leckageminimierungshülse 7 the same pressure as in the compression chamber 5 is applied. At a pressure increase in the compression space 5 the pressure also rises radially on the outside of the leakage minimizing sleeve 7 which then contracts and seals against the piston 4 sets.

How the particular 2 it can be seen, the annular pressure chamber 8th over the annular gap 24 filled with working fluid (see arrow 22 ). At a compression stroke of the piston 4 increase the pressure in the compression chamber and at the same time the pressure in the pressure chamber 8th on. Due to the area ratio outer circumferential surface of the leakage minimization sleeve 7 to the inner circumferential surface of the leakage minimization sleeve 7 and due to the pressure differential between the pressures on both sides of the leakage minimizing sleeve 7 the leakage minimizing sleeve is in the radial direction (see arrow 21 ) and in the axial direction (see arrow 23 ) pressed together. It passes radially inwards over a contact area 25 for sealing engagement with the piston 4 and the front side for sealing contact with the cylinder 3 , The sealing contact with the cylinder 3 prevents the leakage through the minimization sleeve 7 caused seal can be circumvented.

In the present case, the sealing effect is enhanced by the fact that the leakage minimizing sleeve 7 via a spring element 9 against the cylinder 3 is axially biased. The spring element 9 has the shape of a collar sleeve with a first collar 11 that's on the cylinder 3 supported, and a second fret 12 who was interested in the leakage minimization sleeve 7 is supported. The second fret 12 is like one Spring arm executed and is only about an annular contour 13 on an end face 10 the leakage minimization sleeve 7 on (see 3 ). About the federal government 12 Thus, an axial biasing force can be applied. Andernends is the leakage minimization sleeve 7 over a footprint 14 on the cylinder 3 supported. The footprint 14 is smaller than the face 10 because of the footprint 14 a cone 15 connects (see 4 ). Due to the reduced footprint 14 the sealing effect can be further improved. In the present case, the cone indicates 15 a width b greater than a width a of the footprint 14 is.

Again 2 can be seen, has the spring element 9 a recess on the circumference 26 on. The recess 26 serves to create a pressure equalization within the pressure chamber 8th , The first fret 11 of the spring element 9 is also between a top 3.1 and a lower part 3.2 of the cylinder 3 clamped. The multipart design of the cylinder 3 facilitates the production of the annular groove 6 as well as the installation of the leakage minimization sleeve 7 and the spring element 9 ,

The 5 and 6 are alternative embodiments of a spring element 9 for a piston compressor according to the invention 1 refer to. In the 5 is the spring element 9 designed as a helical compression spring. This requires a larger space than that in the 6 illustrated wave spring, so that the height H ₁ the ring groove 6 can vary significantly. The height H ₂ on the other hand gives the height of the leakage minimization sleeve 7 which is smaller than the height H ₁ the ring groove 6 is. In this way, the required hydraulic connection of the pressure chamber 8th with the compression space 5 manufactured. The width B ₁ the ring groove 6 is also greater than the width B _{2 of} the leakage minimization sleeve 7 , so that the difference in the width of the width of the pressure chamber 8th benefit.

As the embodiment of 7 can be seen, moreover, on a spring element 9 be completely dispensed with. Because due to the surface difference of the acted upon in the axial direction with compression space pressure surfaces (end face 10 on the one hand and the footprint on the other 14 forming end faces on the other hand) act on the leakage minimization sleeve 7 hydraulic pressure forces the sleeve 7 in contact with the cylinder 3 hold.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2003/010446 A1 [0004]

Claims (9)

Piston compressor (1) for compressing a working fluid, in particular a liquid or gaseous fuel, comprising a piston (4) which can reciprocate in a bore (2) of a cylinder (3) and which can be filled with the working fluid within the bore (2) Compression space (5) limited, characterized in that the inner circumference side in the cylinder (3) is formed a circumferential annular groove (6) in which a Leckageminimierungshülse (7) is received, which defines an annular pressure chamber (8) together with the cylinder (3) , which is hydraulically connected to the compression space (5), so that in the pressure chamber (8) the same pressure as in the compression chamber (5) prevails and between the piston (4) and the Leckageminimierungshülse (7) over the entire pressure range across a gap and thus a certain flow is maintained in the gap. Piston compressor (1) after Claim 1 , characterized in that the annular groove (6) is arranged at least in sections at the level of the piston (4). Piston compressor (1) after Claim 1 or 2 , characterized in that the annular groove (6) has a height (H ₁ ) which is greater than a height (H ₂ ) of the Leckageminimierungshülse (7). Piston compressor (1) according to one of the preceding claims, characterized in that in the annular groove (6) a spring element (9) is received, by means of which the Leckageminimierungshülse (7) against the cylinder (3) is axially biased. Piston compressor (1) after Claim 4 , characterized in that the spring element (9) on one end face (10) of the Leckageminimierungshülse (7) is supported and is preferably a helical compression spring, a wave spring or a plate spring. Piston compressor (1) after Claim 4 or 5 , characterized in that the spring element (9) is designed as a double collar sleeve and a radially outwardly projecting first collar (11) for axial support on the cylinder (3) and a radially inwardly projecting second collar (12) for axial support on the Leak minimization sleeve (7), wherein preferably the second collar (12) is designed in the manner of a spring arm and only via an annular contour (13) on the end face (10) of the Leckageminimierungshülse (7). Piston compressor (1) according to one of the preceding claims, characterized in that the leakage minimizing sleeve (7) for supporting on the cylinder (3) has a frontally arranged, substantially planar annular contact surface (14), to which radially inwardly a cone (15) connects, wherein preferably the cone in the radial direction has a width (b) which is greater than a width (a) of the footprint (14). Piston compressor (1) according to one of the preceding claims, characterized in that the cylinder (3) is designed in several parts and at least one upper part (3.1) and a lower part (3.2) comprises, which are preferably placed axially against each other in the region of the annular groove (6). Piston compressor (1) according to one of the preceding claims, characterized in that the compression chamber (5) via an inlet valve (16) with a fluid supply (17) and / or via an outlet valve (18) with a pressure line (19) is connectable.

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