EP1548280B1 - Piston compressor - Google Patents

Abstract

The reciprocating piston compressor, especially for the charging of an internal combustion engine, comprises a piston reciprocating inside a cylinder, a working chamber (10,12) on either side of the piston and with inlet and exhaust openings incorporating inlet (20,22) and exhaust (24,26) valves, and a housing enclosing the cylinder and provided with a suction port (34) and a delivery port (36). The space between the cylinder and the housing is divided by a partition (28,30) in such a way that the suction port is connected to the inlet openings and the delivery port is connected to the exhaust openings. A drive device is provided for the reciprocating movement of the piston whereby with a movement stroke of the piston the inlet valve of one working chamber opens and that of the other working chamber closes, and the exhaust valve of one chamber closes and that of the other opens.

Description

The invention relates to a reciprocating compressor, which is particularly suitable for charging an internal combustion engine.

The charging of internal combustion engines is not only a proven means of increasing torque and performance, but also to reduce consumption in part-load operation of an internal combustion engine with predetermined maximum power. The charging of diesel engines is particularly advantageous, since in diesel engines existing in gasoline engines knocking problems are not present.

For charging there are two fundamentally different options, which are also used in combination. In turbocharging, the energy contained in the exhaust gas of an internal combustion engine is used to drive a turbocharger, which drives a turbine that supplies compressed air to the internal combustion engine. In so-called external charging, the compressor is driven by its own drive, for example the crankshaft of the internal combustion engine to be supercharged, or another engine, for example an electric motor, in order to compress the air supplied to the internal combustion engine. Different types of externally driven compressors are known, for example Routs blower, spiral loader or reciprocating compressor.

In the preamble of claim 1 is based on a reciprocating compressor, as described in WO 03/087577 A1. In this reciprocating compressor, the pistons are arranged in a ring around a shaft with which a swash plate is rotatably connected, which causes the axial movement of the piston. Such swash plate drives are relatively complicated in structure and frictional. Furthermore, since the shaft is arranged centrally within the reciprocating compressor and extends in the axial direction of the reciprocating compressor or in the direction of movement of the piston, the delivery volume of the reciprocating compressor is limited relative to the diameter.

A reciprocating compressor is described in US Pat. No. 5,219,273, the pistons of which are driven by a swashplate for a reciprocating movement, similar to the aforementioned WO 03/087577 A1.

US 4,486,157 describes a reciprocating compressor with a double-acting piston whose wall connecting the piston crowns is formed with a transverse to the direction of movement of the piston slot in which a crank pin of a drive shaft engages. On each end face of the piston, a working chamber is formed within the cylinder, which is connected to the environment via each designed as a spring-loaded check valve inlet valve and exhaust valve.

The invention has for its object to provide a particular suitable for charging an internal combustion engine reciprocating compressor, which has a high efficiency with a simple structure.

This object is achieved with a reciprocating compressor according to claim 1.

In the reciprocating compressor according to the invention, two crankshafts extend transversely to the direction of movement of the piston between its bottoms, so that the area of the piston which is effective for compression or air delivery is not reduced by the crankshafts. Furthermore, the two crankshafts rotate in opposite directions and at the same speed, so that the oscillations emanating from a conventional crankshaft drive can be compensated for and the reciprocating compressor, despite its high delivery volume, runs with low vibration, which is advantageous for the supercharging of vehicle internal combustion engines.

The subclaims are directed to advantageous embodiments and developments of the inventive reciprocating compressor.

Fig. 1

einen schematischen Querschnitt durch einen Hubkolbenverdichter,

Fig. 2 und 3

unterschiedliche perspektivische Ansichten eines Kolbens mit den Kolben durchragenden Kurbelwellen,

Fig. 4

eine perspektivische Ansicht zweier Kurbelwellen für einen zweizylindrigen Hubkolbenverdichter,

Fig. 5

die Kurbelwellen gemäß Fig. 4 mit zugehörigen Kolben,

Fig. 6 bis 8

unterschiedliche perspektivische Ansichten eines an einer Seite der Kurbelwellen angeordneten, einem Zylinder zugehörenden Kurbel-/Ventiltriebs,

Fig. 9

ein Einlassventil im Zusammenwirken mit einem Ventilglied,

Fig. 10

ein Auslassventil im Zusammenwirken mit einem Ventilglied,

Fig. 11

eine perspektivische Ansicht eines Rollenstößels,

Fig. 12

eine perspektivische Ansicht des Rollenstößels gemäß Fig. 11 aus anderer Perspektive,

Fig. 13

Details des Nocken- und Kurbeltriebs, und

Fig. 14

eine perspektivische Ansicht eines am Zylinderkopf einer Brennkraftmaschine angeflanschten erfindungsgemäßen Verdichters.

The invention is explained below with reference to schematic drawings, for example, and with further details.
They show:

Fig. 1

a schematic cross section through a reciprocating compressor,

FIGS. 2 and 3

different perspective views of a piston with the piston protruding crankshafts,

Fig. 4

a perspective view of two crankshafts for a two-cylinder reciprocating compressor,

Fig. 5

the crankshafts according to FIG. 4 with associated pistons,

Fig. 6 to 8

different perspective views of a arranged on one side of the crankshafts, a cylinder associated crank / valve train,

Fig. 9

an inlet valve in cooperation with a valve member,

Fig. 10

an exhaust valve in cooperation with a valve member,

Fig. 11

a perspective view of a roller tappet,

Fig. 12

a perspective view of the roller tappet of FIG. 11 from a different perspective,

Fig. 13

Details of the cam and crank drive, and

Fig. 14

a perspective view of a flanged to the cylinder head of an internal combustion engine compressor according to the invention.

According to FIG. 1, a reciprocating compressor according to the invention has a double-sided cylinder 2 closed by end walls, in which a piston 4 can be moved back and forth. The piston 4 includes two mutually spaced piston bottoms 6 and 8, which are advantageously equipped at their peripheral edges for sealing with piston rings and the two inside the cylinder 2 working chambers 10 and 12 separate. The two piston plates 6 and 8 are connected by struts 14 rigidly together, for example screwed. On the mutually facing inner sides of the piston heads 6 and 8 guide surfaces 16 and 17 are formed, which serve to guide sliding blocks 18.

In the end walls of the cylinder 2 openings for each at least one inlet valve 20 and 22 and outlet valve 24 and 26 are formed.

The cylinder 2 is received in a housing 32 by means of brackets forming partitions 28 and 30. The housing 32 has at least one suction opening 34 and an ejection opening 36, wherein, as can be seen, between the outer housing 32 and the Cylinder 2 formed by the partition walls 28 and 30 is divided so that an inlet channel 38 is formed which connects the suction port 34 with the inlet valves 20 and 22 or of these selectively open or closed, leading into the working chambers 10 and 12 inlet openings, and an exhaust passage 40 is formed which connects the exhaust valves 24, 26, or selectively open or closed exhaust ports of the working chambers 10 and 12, to the exhaust port 36.

In Fig. 1, the direction of movement of the piston 4 is horizontal. In FIGS. 2 to 8, it is perpendicular, so that the representations of FIGS. 2 to 8 in accordance with the arrangement according to FIG. Fig. 1 are rotated by 90 °.

FIGS. 2 and 3 show perspective views of the piston 4, each with two crankshafts 42 and 44 traversing the pistons. The axles of the crankshafts which are stationary relative to the cylinder 2 and the housing 32 are designated A in FIG. Each crankshaft has at least one each eccentrically to its axis arranged crank pulley 46 and 48, which cooperates with the sliding blocks 18, along the guide surfaces 16, 17 of the piston heads 6 and 8 linearly perpendicular to the axes of the crankshafts are displaced, so that a Gleitstein- or gate guide is created, with the circumferential eccentric movement of the crank disks in a conventional manner in an oscillating movement of the guided inside the cylinder 2 piston can be converted. The sliding blocks are advantageously divided for easy mounting.

FIG. 4 shows the crankshafts 42 and 44 in a design for two respective cylinders 2 arranged behind one another within a housing 32 (FIG. 1), in each of which a piston 4 operates. In the example shown, each piston on the crankshaft 42 is associated with two crank disks 46 and on the crankshaft 44 a crank disk 48 which cooperates with corresponding sliding blocks 18. As can be seen, the crank disks 46 and 48 are axially offset from each other, so that their trajectories pass radially, whereby a smaller distance between the crankshafts 42 and 44 is possible. For mass balance of the oscillating forces, the crankshafts 42 and 44 are provided in a conventional manner with balancing weights 50 and 52, respectively.

The crankshafts 42 and 44 may be mounted, for example, in each case in the wall of the cylinder 2.

To drive the valves 20, 22, 24 and 26, the crankshafts cam 54 and 56, with which the valves are actuated via actuators. In order for only one of the crankshafts 42, 44 to be driven externally, a gearwheel 58 or 60 is connected in each case to one end of the crankshaft in a rotationally fixed manner to the respective crankshaft. The gears 58 and 60 are equal in size and mesh with each other, so that the crankshafts 42 and 44 rotate in opposite directions at the same speed. Advantageously, the gears 58, 60 serve as elements of a gear pump, which is arranged in a coolant and / or lubricant circuit of the compressor.

Fig. 5 shows the gem. Fig. 4 assembled piston.

6 shows a perspective view of sections of a left side of the crankshafts 42, 44 arranged according to the figure, a cylinder associated crank / valve train.

In the example shown, cams 54 and 56 are formed on each crankshaft 42 and 44 on both sides outside of the cylinder, with which roller tappets 62 and 64 cooperate, each actuating a cylinder-like cross-over valve member 66 and 68 respectively. The left valve member 66 shown in FIG. 6 actuates a plurality of inlet valves 20 (FIG. 1). The right valve member 68 actuates a plurality of exhaust valves 24. In the example shown, the valves are forcibly guided on the respective valve members. As can be seen, four intake valves and four exhaust valves are arranged on an end wall of the cylinder 2 in the illustrated example and are actuated by means of a respective valve member.

Since, as can be seen in FIG. 1, the inlet valves 20, 22 and the outlet valves 24, 26 are opposite each other, they are arranged on the left side or right side (FIG. 1) or above or below the piston (FIGS. 2 to 8) Valve drives arranged the same or mirror symmetry.

When the compressor is operated in two-stroke operation, the intake valves and the exhaust valves are each actuated by 180 ° out of phase with respect to the rotation of the crankshafts, so that in opposite directions rotation of the juxtaposed crankshafts 42, 44 at the same speed and appropriate design of the cam 54, 56 results in an in-phase actuation of the respective valves.

The valve drive will be explained in more detail below with reference to FIGS. 9 to 13:

The valve members 66 and 68 are guided in a linearly movable guides not shown in the housing and are reciprocated by the cams 54 and 56 against the force of the springs 70 and 72, which are supported between the housing 32 and the respective valve member ,

The bridge-type valve member 66 (FIG. 9) actuating the exhaust valves 20 includes for each exhaust valve a pilot passage 74 through which the stem of the exhaust valve 20 extends and which leads into a recess 76 in which the stem of the valve terminates. Between an end flange 78 of the valve stem and the valve member 66, a valve spring 80 is supported, which urges the exhaust valve 20 in the closed position. The end flange 28 opposite a threaded pin 82 is screwed into the valve member 66, which serves for clearance adjustment.

The valve member 68 actuating the exhaust valves 24 (Figure 10) also has, for each exhaust valve 24, a pilot passage 84 through which the valve stem extends. The valve stem 84 terminates in an example screwed with him stop 86, the distance from the valve disc to the game setting is adjustable. Between the valve member 68 and the valve, a valve spring 88 is supported.

With the construction described in FIGS. 9 and 10, which can be varied in many ways, it is achieved that no separate housing-fixed guide is required for the valve stems that the inlet valves 20 as shown in FIG. 9 in each case during a downward movement of the valve member 66 are opened and the exhaust valves 24 are opened as shown in FIG. 10 at a movement of the valve member 68 upwards. In addition, can be achieved by appropriate dimensioning of the springs 80 and 88, that the inlet valve 20 at strong Vacuum in the associated working chamber opens without the valve member 66 being moved and / or the exhaust valve 24 opening at high overpressure in the associated working chamber without the valve member 68 being moved.

11 and 12 show a roller tappet 62 with roller 88 mounted in it and housing-fixed guide 90.

FIG. 13 shows a section of the two crankshafts 42 and 44 with the cams 54 and 56. In contrast to the embodiment according to FIGS. 6 to 8, the crankshaft 42 has only one crank disk 46, whereas the crankshaft 44 has two crank disks 48. As can be seen, the cam 54, which actuates the inlet valves associated with the roller tappets or bridge members 66, as a "negative cam" is formed, the bridge member 66 is normally in the position gem. Fig. 9 urges against the springs 70 and causes only in its smaller diameter cam portion to take place as shown in Fig. 9 downward movement of the valve member 66 to open the inlet valve 20. The exhaust valves associated cam 56 of the crankshaft 44 is formed as a normal cam with a diameter enlarged cam lobe.

The assembly of the piston compressor described is done as follows:

First, the actual engine, as shown in Fig. 5, assembled by the crankshaft and the sliding blocks are arranged on each two adjacent piston crowns and the other piston heads are then mounted by means of the struts 14, so that the assembly according to FIG arises.

About the piston 4, the cylinder 2 are then attached, each consisting of two centrally divided halves. Subsequently, the valve trains are mounted in each mounted on the cylinders mounting surfaces and the entire assembly is assembled in the housing 32 also formed in two parts. The cylinder halves and the housing halves may be integrally formed with each other.

FIG. 14 shows a piston compressor 92 according to the invention flanged to the intake side of a motor housing or cylinder head 94 of an internal combustion engine. 96 denotes a pulley for driving one of the crankshafts.

At the intake opening 34 of the housing 32, an intake assembly, not shown, may be flanged in addition, which may include, for example, a throttle valve and / or a device for measuring the inflowing air amount, etc.

The function of the described compressor is the following:

Advantageously, the compressor is operated in two-stroke operation. When the piston 4 moves from left to right according to FIG. 1, above all the inlet valve 20 and the outlet valve 26 are actuated such that fresh air flows into the working chamber 10 and fresh air compressed from the working chamber 20 is ejected at a suitable pressure level. The inlet valve 22 and the outlet valve 24 are advantageously in the movement from left to right of the piston 4 to. As the piston moves from right to left, the actuations of the valves occur in opposite directions, i. the fresh charge flow is then determined by the inlet valve 22 and outlet valve 24, whereas valves 20 and 26 are preferred. It is understood that the intake valves and exhaust valves can be controlled by suitable, per se known, phase adjustment and / or Hubverstelleinrichtungen such that the delivered air flow (air mass flow) to the respective, required for an internal combustion engine operating conditions and the compressor by appropriate appropriate Setting the respective opening and closing times of the valves relative to the dead centers of the piston movement works with high efficiency.

In the following, functional features of the described reciprocating compressor are explained, whereby also examples of possible modifications and additional features are given:

1. Overall design:

The reciprocating compressor according to the invention works, even if it contains only one cylinder and arranged therein, a double-acting piston, with high efficiency and low pressure pulsations. The formation of the piston with two mutually spaced piston crowns, between which the crank mechanism is arranged, not only has the advantage that the crankshaft and its lubrication is completely separate from the work spaces, but also allows easy storage of the crankshaft (s) in the cylinder wall. The reciprocating compressor may include any number of cylinders having pistons therein, with the individual cylinders being operated out of phase so as to achieve minimum pressure pulsations. The possible small stroke / bore ratio allows low piston speeds, which favorably affects the durability.

The design allows for large cross-sections of the intake and exhaust valves relative to the cylinder cross-section, allowing the compressor to operate with low flow resistance.

The loader can be flange-mounted directly on the cylinder head or a suction pipe of an engine to be charged. When flanged directly to the cylinder head, the housing 32 may have along its length a plurality of discharge ports 36 connected within the housing that lead directly into the intake ports of the individual cylinders. On the suction side, a suction part can be flanged in front of the compressor, which contains, for example, a throttle cap, contains a connection for exhaust gas recirculation or from which a bypass line emanates, which leads bypassing the compressor directly into a suction pipe of the internal combustion engine.

The design allows for a high surface-to-volume ratio in relation to the stroke volume, whereby large charge exchange valves are possible.

Overall, the free paths between the walls of the housing and the cylinder are short, so that when cooling the walls and the compressed gas is effectively cooled.

2. To the crank drive:

The crank mechanism may include one or more crankshafts, wherein the implementation of the rotational movement of the crankshaft (s) in a reciprocating motion of the piston via a variety of known mechanisms can be done. The mechanism described by means of sliding or sliding blocks is easy to install, works friction and leads to a soft, sinusoidal movement of the piston.

The described embodiment with two counter-rotating crankshafts can work as Lancester compensation, with oscillating, sinusoidal mass forces of piston and sliding blocks in the crank mechanism of each piston are completely compensated. Furthermore, each individual cylinder is balanced, so that no cylinder dynamic mass forces are introduced into the housing. Furthermore, there are no outwardly acting mass forces outside of the housing, so that the compressor according to the invention operates very low vibration.

The described embodiment of the crankpin and the crank disks with mutual axial offset leads on the one hand to a compact design and on the other hand, to a low mechanical stress and thus high speed resistance of the crank mechanism.

Another advantage is that the piston or pistons move free of lateral force, which reduces the friction losses and increases the service life. The shirt-free piston bottoms contribute to weight reduction. There are no tilting forces.

The gears 58 and 60 at the ends of the crankshafts (FIG. 4) serve for synchronization and power transmission between the crankshafts. The gears can also be replaced by belting means, such as a toothed belt. Only one crankshaft has to be driven from one end, for example by means of the pulley 96 (FIG. 14).

3. Cooling / Lubrication:

The gears 58 and 60 (Figure 4) may be used as elements of a gear pump capable of delivering a cooling / lubricating fluid circulating in channels formed in the compressor. Advantageously, at least the working chamber 10 and 12 bounding walls of the cylinder are cooled, wherein the short Wärmeleitwege for a provide efficient cooling. The loader may additionally have an internal heat exchanger arranged in front of the discharge opening 36. Alternatively or additionally, the compressed air can flow through an external heat exchanger before it enters the internal combustion engine.

The advantageously integrally formed lubricant / coolant circuit of the supercharger can be connected to the internal combustion engine or be formed separately therefrom.

In general, an important aspect of the compressor according to the invention is that, on the one hand, the compressed air flowing through the discharge opening 36 is free of any lubricant and, on the other hand, is as cool as possible. It is advantageous for both that the two crankshafts, which are at the same time camshafts, are guided between the piston bottoms and are mounted in the cylinder 2 by means of easily sealable bearings, so that inside the piston an outwardly dense lubricant space is formed, the liquid lubricant serves as a coolant through which crankshafts can be supplied simultaneously. The lubricant / coolant can effectively cool the piston crowns from the inside. It will be understood that fluid return is formed through channels passing through the cylinder wall, the space between the cylinder and the housing and the housing, so that the coolant / lubricant circulates.

Shaft guides for the roller tappets 64 may be lubricated by wetting the crankshafts so that the lubricant does not enter the fresh air. Advantageous are very hard ram stem ends or contact surface combinations.

For the connection of the valves to valve lever or, as in the example shown, to the bridge-like valve members a friction and wear-favorable material pairing is advantageous.

For the guides of the roller tappet and valves material pairings are advantageous, which are provided in a conventional manner with solid lubricants or impregnated with lubricant. It is also possible to provide the seat rings with solid lubricant or soak with lubricant.

Because of the low operating temperatures, it is possible to work with solid lubricants or with impregnated guide bushings so that the circulation of liquid lubricant or coolant to the lubricant spaces within the pistons can be restricted.

The use of ceramic materials also makes it possible to minimize the need for liquid lubricants.

4. Charge change control:

As explained, the charger according to the invention advantageously operates in the two-stroke process. The intake and exhaust valves can be operated in a variety of ways. In the embodiment, they can not only be operated via the valve members with appropriate dimensioning of the springs, but also work as check valves, the intake valves open at negative pressure in the respective working chamber and open the exhaust valves at overpressure. In alternative embodiments, only the intake valves or only the exhaust valves may be formed as check valves and the other valves may be actuated by the one or more crankshafts.

Even with forced control of the valves, in particular the exhaust valves, a self-control function can be realized when the pressure drop across the valves exceeds a predetermined value.

The intake and / or exhaust valves can also be controlled by means of per se known valve actuation mechanisms, for example by changing the effective tap lever and / or the Abgriffswinkel that their opening or closing function is variable, and / or can in the open or closed position being held.

5. Control of the compressor:

The speed of the crankshaft of the compressor may be rigidly coupled to the crankshaft of an internal combustion engine. Between the supercharged internal combustion engine and the compressor, a transmission with stepwise or continuously adjustable ratio can be arranged be. By means of a clutch, the compressor can be completely disconnected from the internal combustion engine.

The delivery rate of the compressor can also be varied by variable actuation of the valves, with valves in the open position having a low-flow path from the intake opening 34 to the discharge opening 36 (FIG. 1).

Alternatively, when the compressor of the internal combustion engine is out of operation fresh air can be supplied via a bypass line.

Depending on requirements, individual cylinders can be switched off.

The delivery rate of the loader can be changed as required by controllable openings in the partitions 28 and 30. The inlet opening 34 may be preceded by a throttle valve.

It can be used in parallel or in series connected to an internal combustion engine more compressors.

To even less stress on the piston bottoms, each of the crankshafts may be provided with two or more crankshafts associated with each piston.

The valves can also be operated completely independently of the rotation of the crankshaft by its own drives, such as electromagnetic, hydraulic or other suitable drives. Instead of the two crankshafts, only one crankshaft can extend through each piston, etc.

In summary, the compressor offers numerous possibilities for controlling maximum compression of the air via light compression, no compression up to the recoil, in which the compressor is used for braking.

The compressor or supercharger according to the invention is suitable for charging all types of internal combustion engines, two-stroke engines, four-stroke engines or machines operating with different timing, gasoline engines, diesel engines, gas engines, etc.

It is explicitly pointed out that all features disclosed in the description and / or the claims are considered separate and independent of each other for the purpose of original disclosure as well as for the purpose of limiting the claimed invention independently of the feature combinations in the embodiments and / or the claims should. It is explicitly stated that all range indications or indications of groups of units disclose every possible intermediate value or subgroup of units for the purpose of the original disclosure as well as for the purpose of restricting the claimed invention, in particular also as the limit of a range indication.

LIST OF REFERENCE NUMBERS

2

cylinder

4

piston

6

piston crown

8th

piston crown

10

working chamber

12

working chamber

14

strut

16

guide surface

17

guide surface

18

slide

20

intake valve

22

intake valve

24

outlet valve

26

outlet valve

28

partition wall

30

partition wall

32

casing

34

suction

36

discharging port

38

inlet channel

40

exhaust port

42

crankshaft

44

crankshaft

46

crank

48

crank

50

Leveling compound

52

Leveling compound

54

cam

56

cam

58

gear

60

gear

62

roller plunger

64

roller plunger

66

valve member

68

valve member

70

feather

72

feather

74

Guide passage

76

recess

78

end flange

80

valve spring

82

grub screw

84

Guide passage

86

attack

88

role

90

guide

92

piston compressor

94

cylinder head

96

pulley

Claims (12)

1. Piston compressor, in particular for charging an internal combustion engine, comprising:

   at least one cylinder (2), inside of which two working chambers (10, 12) are formed by a reciprocally-moving piston (4) having two mutually-separated piston heads (6, 8), which working chambers (10, 12) are located on opposing sides of the piston and each includes at least one intake and one exhaust opening, in which an intake valve (20, 22) and an exhaust valve (24, 26), respectively, operates,

   a housing (32) surrounding the cylinder, the housing having a suction port (34) connected with the intake opening and an exhaust port (36) connected with the exhaust opening, and

   a drive apparatus for reciprocally moving the piston, wherein, during each stroke of the piston, the intake valve of one working chamber opens and the intake valve of the other working chamber closes, and the exhaust valve of the one working chamber closes and the exhaust valve of the other working chamber opens,

   characterized in that:

   the drive apparatus includes two crankshafts (42, 44) rotating in opposite directions with the same rotational speed, which crankshafts extend between the piston heads (6, 8) through the piston and the cylinder (2) traverse to the movement direction of the piston (4).
2. Piston compressor according to claim 1, characterized in that the crankshafts (42, 44), extend at least partially through the housing (32).
3. Piston compressor according to claim 1 or 2, characterized in that the crankshafts (42, 44) are borne in the cylinder (2) and/or the housing (32) and the transfer of movement between the piston (4) and the crankshafts (42, 44) takes place via slide elements (18) that are displaceable on the piston (4).
4. Piston compressor according to one of claims 1 to 3, characterized in that the stroke drives (18, 46; 18, 48) are axially offset relative to each other between the crankshafts (42, 44) and piston (4) and radially overlap each other.
5. Piston compressor according to one of claims 1 to 4, characterized in that one of the crankshafts (42, 44) is externally drivable and is engaged with the other crankshaft so as to rotate therewith.
6. Piston compressor according to one of claims 1 to 5, characterized in that at least one of the valves (20, 22, 24, 26) is actuated by a crankshaft (42, 44).
7. Piston compressor according to one of claims 1 to 6, characterized in that an actuating mechanism, which is controllable independently of the piston motion, is provided for at least one of the valves (20, 22, 24, 26).
8. Piston compressor according to one of claims 1 to 7, characterized in that a valve element (66, 68) guided on the housing (32) is moved by at least one cam (54, 56) formed on the crankshaft (42, 44), a shaft of at least one intake- or exhaust valve (20, 22) is guided in the valve element, which valve is supported on the valve element by a spring (80, 88) such that it is actuatable by the valve element and is movable independently of the valve element.
9. Piston compressor according to one of claims 1 to 8, characterized in that a toothed wheel (58, 60), which is connected with a crankshaft (42, 44) so as to rotate therewith, forms a pumping element of a cooling- and/or lubricating system of the compressor.
10. Piston compressor according to one of claims 1 to 9, characterized in that the housing (32) surrounding the cylinder (2) is formed with a separating wall (28, 30) that divides an intermediate space between the cylinder and the housing such that the suction port (34) is connected with the intake opening and the exhaust port (36) is connected with the exhaust opening.
11. Piston compressor according to claim 10, characterized in that the separating wall (28, 30) divides the intermediate space formed between the housing (32) and the cylinder (2) into two chambers (38, 40), one of which forms an inlet channel (38) connecting the suction port (34) with the intake opening and the other of which forms an outlet channel (40) connecting the exhaust port (36) with the exhaust opening.
12. Piston compressor according to one of claims 1 to 11, characterized by a plurality of cylinders (2) accomodated in a common housing (32) and with pistons (4) disposed therein, the pistons being reciprocally moved by at least one common crankshaft (42, 44).

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