EP2483541A1

EP2483541A1 - A supercharger with two intermeshing rotors and disc clutch

Info

Publication number: EP2483541A1
Application number: EP10820908A
Authority: EP
Inventors: Robert Pettersson; Henrik Hägglund
Original assignee: Svenska Rotor Maskiner AB
Current assignee: Svenska Rotor Maskiner AB
Priority date: 2009-10-02
Filing date: 2010-09-28
Publication date: 2012-08-08
Also published as: WO2011040869A1; BR112012007287A2; CN102686847A; SE534205C2; EP2483541A4; RU2012117758A; KR20120092620A; JP2013506784A; AU2010301163A1; SE0950723A1

Abstract

The invention concerns a supercharger that has two rotors engaging into each other and is provided with a disc clutch. The disc clutch has driving (9) and driven (12) clutches connected with a drive shaft (7) and with one of the rotors, respectively. Furthermore, there is an axially displaceable pressing body (15) as well as actuation device (13) for the same and a deactuation spring (17). According to the invention, the disc clutch comprises a stop device (18, 19) that limits the axial movement of the pressing body (15) in the deactuation direction. The stop device (18, 19) consists of an impact means (18) on the pressing body (15) or on the driven clutch holder (11) and a stop means (19) on the other component. The impact means (18) is axially fixed while the stop means (19) is attached by a friction joint.

Description

A SUPERCHARGER WITH TWO INTERMESHING ROTORS AND DISC

CLUTCH

Field of the Invention

The present invention relates to a supercharger that has two intermeshing rotors and is provided with a disc clutch, which disc clutch comprises

- driving clutches having a driving clutch holder connected with a drive shaft,

- driven clutches having a driven clutch holder connected with one of the rotors,

- An axially displaceable pressing body arranged for the compression of the clutches upon actuation,

- actuation device for the actuation of the pressing body, and

- spring means for the deactuation of the pressing body.

Background of the Invention

By SE 51 1 761 , a supercharger of the above-mentioned kind is previously known. The supercharger is engaged by the disc clutch when there is a need to supply air at positive pressure to the internal combustion engine, e.g., upon acceleration.

When engagement of the supercharger is effected, a certain delay arises from the fact that engagement manoeuvring is initiated, e.g., via the accelerator pedal or via electronically controlled engagement, until the supercharging becomes active. The delay comprises, among other things, the time it takes for the piston that manoeuvres the disc clutch to move from the initial position until the clutches are fully meshed into each other. The move should bridge, on one hand, the distance that corresponds to the movement until the pressing body that presses the clutches, and that is a consequence of necessary manufacturing tolerances, against each other reaches the clutch pack, and on the other hand the distance that is required to press together the clutches into complete meshing with each other. In a non-actuated state, the driving and driven clutches must of course have a certain clearance in relation to each other. It is important to reduce the time for the mentioned delay as much as possible.

By US 5 749 451 , a disc clutch is furthermore previously known, in which there is a device to limit the movement of the clutch plate in the deactuation direction with the purpose of limiting the stroke length and thereby the engaging time. The device comprises spring-loaded balls that co-operate with cam surfaces. It is therefore complicated in its design and thereby costly to manufacture.

Furthermore, a device of this type is susceptible to operational disturbances. The known disc clutch is not intended for engagement of a supercharger and is thereby not adapted to the special conditions in the manoeuvring of such a one.

For a disc clutch for the engagement of a supercharger, the need of a quick engagement is particularly accentuated. It is important that the supercharger as promptly as possible responds on initiation of its engagement, e.g., upon overtaking, when a supercharger in a car is concerned.

The object of the present invention is to reduce the engaging time for a

supercharger of an internal combustion engine in a simple and reliable way.

Description of the Invention

In accordance with the invention, the object set forth is attained by the fact that a supercharger of the kind mentioned by way of introduction has the special features that the disc clutch comprises a stop device for the limitation of the axial movement of the pressing body in the deactuation direction, which stop device comprises impact means and stop means, one of the impact means and the stop means being connected with the driven clutch holder and the other one of the impact means and the stop means being connected with the pressing body, the connection of the impact means being axially fixing and the connection of the stop means being provided by a friction joint.

By the fact that the stop device limits the axial movement of the pressing body, an optimized axial positioning of the impact means and the stop means can be accomplished so that the axial movement is limited to what is required to bridge the clearance of the clutches.

The part of the stroke length that is required to bridge the requisite manufacturing tolerances is thus eliminated. Furthermore, the clearance of the clutches can be kept at a minimum. Since there are several, usually about fifteen, co-operating components, tolerance elimination and clearance reduction lead to considerable shortening of the stroke length upon engagement. Thanks to the fact that the connection of the stop means is provided by a friction joint, it is easy to axially adjust the positioning of the stop means to a situation corresponding to said optimal positioning. Thereby, the distance that the pressing body needs to be displaced before it begins to press together the clutches is eliminated. Accordingly, the stroke length of the pressing body corresponds only to the clearance of the clutches. The stroke length of the manoeuvring means becomes limited to a corresponding degree. The engaging time can thereby be reduced from approx. 0,5 s down to 0,2 s, i.e., about half the value.

The special solution of a friction joint between the stop means and its related component entails that the stop device becomes very easy to produce and adjust. Moreover, the design entails that the reliability becomes very high.

Although the advantages of the invention primarily are interesting to use by reducing the engaging time, these advantages may alternatively be utilized by accepting a maintained engaging time but instead use a manoeuvring device that is dimensionally reduced. In, e.g., hydraulic piston manoeuvring, where the oil pressure of the engine is used as hydraulic source, the flow can thus be throttled. If the oil instead is supplied by a pump, it is possible to select one having lower pressure and/or volume. According to a preferred embodiment, the stop means comprises at least one stop ring.

Forming this means as a ring entails constructive advantages and facilitates the formation of the friction joint in an expedient way. Suitably, the ring is coaxial with the principal axis of the disc clutch. Also the impact means is suitably ring-shaped and preferably coaxial. The stop ring may alternatively be laterally displaced in parallel to the principal axis of the disc clutch, wherein it may be suitable to have a plurality of stop rings, preferably arranged on a circular line that is concentric with the principal axis of the disc clutch.

According to an additional preferred embodiment, the friction joint of each stop ring is formed between a radial outside or inside of the stop ring and a radial inside or outside, respectively, of the one of the driven clutch holder and the pressing body with which the stop ring is connected.

Thereby, in a relatively easy way, a sufficiently adapted frictional force without unnecessary high requirements on manufacturing precision can be provided. According to an additional preferred embodiment, the stop ring is provided with means for the provision of differently strong frictional force in different axial directions, where the force that keeps the stop ring from being displaced in the motion direction of the pressing body upon actuation is smaller than the frictional force that keeps the stop ring from being displaced in the opposite direction.

Thereby, the stop ring can easily be adjusted to an optimal axial situation by the fact that there is very little resistance to being displaced in the pressing direction so that the stop ring limits the displacement of the pressing body during the deactuation movement to what corresponds to only the clearance of the clutches. The greater frictional force in the opposite direction entails that stop action is guaranteed when the impact ring impacts on the stop ring in the deactuation movement.

According to an additional preferred embodiment, the radial side of each stop ring that constitutes one part of the friction joint is asymmetrical for the provision of said differently great frictional force.

The provision of the inequality in the frictional force by the design of the stop ring is a relatively simple and expedient solution. According to an additional preferred embodiment, the radial side of each stop ring that constitutes one part of the friction joint is provided with obliquely directed projections, which are inclined in the motion direction of the pressing body upon deactuation.

The inclined projections function as a kind of barbs that are pressed inward against the material of the driven clutch holder or the pressing body, thereby creating a strong frictional force that counteracts movement in the deactuation direction. In the other direction, the projections will be able to draggingly slide with ensuing low frictional force, which allows the positioning thereof. The alternative wherein the projections are directed outward toward the pressing body is particularly advantageous, since the pressing body can be made from aluminium, which gives good gripping conditions.

According to an alternative embodiment to the ones mentioned right above, the friction joint is a compression joint having a pressing force that is greater than the maximum axial force of the spring means. The stop ring can thereby be formed as a plain ring that is fixedly shrunk to the one of the driven clutch holder and the pressing body with which it is connected. While the stop ring in the embodiments mentioned right above had different resistance to movement in different axial directions, here the frictional force counteracting movement is instead the same in both directions.

Here, possibility of movement in one direction and resistance to movement in the other direction are instead provided by adapting the frictional force to the differently strong external forces that act on the ring in the respective direction. According to an additional preferred embodiment, the manoeuvring means comprises a hydraulic piston.

This is the generally most used type of manoeuvring means in a disc clutch of a supercharger, and therefore the invention is particularly interesting to utilize in such a manoeuvring means. As has been pointed out initially, in this embodiment the invention allows the use of hydraulic medium supply of lower performance without the engaging time becoming smaller in comparison with conventional technique.

According to an additional preferred embodiment, the supercharger comprises a screw compressor.

The invention is per se applicable to other kinds of supercharger types in the form of, e.g., a Roots blower, but is particularly suited to be applied to a screw compressor, thereby utilizing the general advantages that such a one entails.

The above-mentioned preferred embodiments are defined in the claims depending on claim 1. It should be emphasized that additional preferred embodiments naturally may consist of all feasible combinations of the above-mentioned preferred embodiments.

In a second aspect, the invention also concerns a disc clutch of a corresponding design as the disc clutch included in the invented supercharger, particularly according to anyone of the preferred embodiments of the same.

The invented disc clutch and the preferred embodiments of the same have advantages of the corresponding kind as the invented supercharger and which have been accounted for above.

The invention is explained in more detail by the subsequent detailed description of embodiment examples of the same, reference being made to the appended drawing figures.

Brief Description of the Figures

Fig. 1 is a perspective view of a supercharger of the type the invention relates to. Fig. 2 is an axial section through the disc clutch of the supercharger in Fig. 1 in the disengaged position. Fig. 3 is a detailed enlargement in Fig. 2

Fig. 4 is an axial section corresponding to the one in Fig. 2 in the engaged

position.

Fig. 5 is a partial enlargement in Fig. 4.

Fig. 6 is an end view of a part of a detail of the disc clutch in Figs. 2-5.

Fig. 7 is a side view of the detail in Fig. 6.

Figs. 8 and 9 are axial sections corresponding to the ones in Fig. 3 and Fig. 4, respectively, illustrating alternative embodiment examples.

Figs. 10 and 11 are axial sections corresponding to the ones in Figs. 3 and 4, respectively, illustrating an additional embodiment example.

Figs. 12 and 13 are an end view and a side view, respectively, of a detail of the disc clutch in Figs. 10-11.

Figs. 14 and 15 are axial sections corresponding to the ones in Figs. 3 and 4, respectively, illustrating an additional embodiment example.

Description of Embodiment Examples

The supercharger illustrated in a perspective view in Fig. 1 comprises a screw compressor arranged in a compressor housing 1 and a disc clutch provided with driving connection 6 and arranged in a clutch housing 2, which housings are joined to each other. The screw compressor has two screw rotors 4, 5 engaging into each other, one of which being a male rotor, the other one a female rotor. Through the compressor outlet 3, air is delivered that has been compressed by the chambers formed between the rotors 4, 5 and the compressor housing of an internal combustion engine. An inlet (not shown) is arranged in the other end of the rotors for the intake of the air. The invention is also applicable to similar rotors, e.g., of the Roots type.

In normal operation, the supercharger does not work. At temporarily increased power requirement, the disc clutch is actuated to drive the supercharger.

The disc clutch shown in more detail in Figs. 2 and 3 has a driving part and a driven part. The driving part comprises a driving shaft 7 that, via driving connection 6 (see Fig. 1 ), is connected with an input drive shaft. By a driving clutch holder 8, the driving shaft 7 is spline-connected with the driving clutches 9.

The driven part comprises a driven hub 10 that, by a driven clutch holder, is spline- connected with the driven clutches 12. The driven hub 10 is drivingly connected with a driven shaft that consists of one of the screw rotors, suitably the female rotor. For the sake of clarity, connection of the driven hub 10 with rotor shaft is omitted in the figure, but may be of conventional kind. In Fig. 2, the disc clutch is deactuated, i.e., no driving power is transferred from the driving clutches 9 to the driven clutches 12 and the supercharger is thus not active.

For the engagement of the supercharger, there is a hydraulic piston 13 having a sealed space 14 for the supply of hydraulic medium. On a sleeve-shaped extension 13a of the hydraulic piston 13, a pressing body 15 is journalled via a ball bearing 16. A spring 17 is arranged between the pressing body 15 and the driven clutch holder 11 and provides a distancing action between these. When the supercharger is to be engaged, hydraulic medium is introduced into the sealed space 14, the piston 13 being displaced to the right in the figure and thereby also the pressing body 15 while overcoming the counter force from the spring 17. When the clutch pack has been compressed, driving torque is

transferred to the driven hub 10 and further to the supercharger. This state is illustrated in Figs. 4 and 5.

Upon disengagement, the pressure in the sealed space 14 is released, the pressing body 15 being pressed back to the left in the figures by virtue of the spring and thereby also the hydraulic piston 13 being pushed back leftward.

What have been described hitherto are essentially such things that the present invention has in common with a conventional disc clutch of a supercharger. The special with the present invention is a stop device that limits the movement of the pressing body upon deactuation, i.e., disengagement of the disc clutch. The stop device consists of an impact ring 18 and a stop ring 19. The impact ring 18 is fixed in a groove 20 on the inside of an axially projecting flange 21 of the pressing body 15. The stop ring 19 is attached on the outside of the driven clutch holder 11. The function of the stop device is most clearly seen in Figs. 3 and 5.

When the disc clutch is to be disengaged from the situation illustrated in Figs. 4 and 5, the pressing body 15 is moved leftward by the spring 17 and thereby also the impact ring 18. When the impact ring 18 in that connection has reached up to the stop ring 19, as is shown in Figs. 2 and 3, continued movement is prevented and the pressing body 15 and the hydraulic piston 13 assume an axial position defined by the stop means 18, 19. Without the stop ring 19, the pressing body 15 and the hydraulic piston 13 would have, by virtue of the force from the spring 17, continued to be displaced leftward as far as allowed by the stroke length of the hydraulic piston.

By the fact that the stop means 18, 19 thus limits the return movement of the hydraulic piston, the stroke length required when the disc clutch is to be

reactuated becomes shorter than what would be the case without the stop means 18, 19. Thereby, the engaging time becomes correspondingly shorter.

The distance between the impact ring 18 and the stop ring 19 in the engaged state (Figs. 4 and 5) is adjusted so that it corresponds to the distance required to bridge the clearance of the clutch pack. The adjustment of the distance is provided by adjustment of the axial position of the stop ring 19 on the driven clutch holder 11.

In order to allow such an adjustment and simultaneously ensure the stopping function of the stop ring 19, the stop ring is 19 designed so that its connection with the driven clutch holder 11 allows axial displacement in one direction but not in the other one. This is provided by the fact that the stop ring 19, as is seen in Figs. 6 and 7, has a number of inwardly directed projections 22, which are directed obliquely inward.

As is seen in Figs. 3 and 5, the stop ring is 19 applied to the driven clutch holder 11 with the oblique direction to the left as seen from the outside and in. The oblique direction entails that the inner edge of the respective projection 22 in a barb-like way is pressed against the outside of the clutch holder 11 , which results in great resistance to leftward movement of the stop ring. In the other direction, the resistance to movement is considerably lower since the projections 22 then can slide against the outside of the clutch holder 11. The outside of the stop ring 19 abuts against the inside of the flange 21 of the pressing body 15 so that the ring is clamped between the flange 21 and the driven clutch holder 11.

Adjustment of the axial position of the stop ring 19 is effected by the stop ring 19, upon mounting of the disc clutch, being preliminary placed further out to the left on the driven clutch holder 11 than what is shown in the figures. Upon initial actuation of the disc clutch, in that connection, also the pressing body 15, by virtue of the force from the spring 17, is situated further to the left than what is shown in the figures, and the hydraulic piston 13 starts from a position situated correspondingly further to the left at a principally full stroke length. When the chamber 14, upon this initial engagement movement, is pressurized and the hydraulic piston 13 is displaced rightward, a shoulder 24 on the inside of the flange 23 will displace the stop ring 19 in the same direction, i.e., the direction in which the stop ring is easily displaceable. Also the impact ring 18 is naturally displaced rightward together with the pressing body 15. Upon completed engagement movement, the position shown in Figs. 4 and 5 is reached.

Then, when disengagement occurs as the chamber 14 is pressure-released and the pressing body 15 is displaced leftward due to the spring 17, the impact ring 18 follows in the return movement, but not the stop ring 19. When the impact ring 18 reaches the stop ring 19 and contacts the same, continued movement of the impact ring 18 is blocked and thereby also that of the pressing body. This is due to the strong resistance of the stop ring 19 described above to move in the direction that the spring force from the spring 17 cannot overcome. The disc clutch is now in the disengaged position (Figs. 2 and 3).

The thus adjusted position of the stop ring 19 defines the stroke length upon further engagements. The stroke length will then be limited to the clearance of the clutch pack.

The device entails furthermore an automatic readjustment as the clutches are wearing down. This is due to the fact that increased wearing down of the clutches causes the stroke movement to proceed somewhat further rightward and thereby displace the stop ring 19 correspondingly in this direction.

An alternative embodiment of the stop ring 19 is illustrated in Figs. 8 and 9. Here, the stop ring is formed as a shrink ring 19a. The shrink ring 19a forms a

compression joint with the driven clutch holder 11. The compression joint is adapted so that the frictional force becomes greater than what can be overcome by the force from the spring 17, but sufficiently limited to be possible to be overcome by the manoeuvring force from the hydraulic piston 13. Thus, upon disengagement movement, the stop ring 19a will stop the leftward movement of the impact ring 18 and thereby limit the return stroke length.

An initial axial positioning of the stop ring 19a is made to limit the stroke length to only what is required as regards the clearance of the clutch pack. In that connection, the stop ring 19a is applied to the driven clutch holder 11 and pushed into place by a mounting press. The engaged situation is shown in Fig. 9.

Alternatively, it is possible to push the stop ring into place by the manoeuvring piston upon an initial engagement. This presupposes that the pressing force of the joint is smaller than the force attainable by the manoeuvring piston.

Upon disengagement, the impact ring will be displaced leftward until it is prevented from moving further when it is abutting against the stop ring 19a. The stop ring is blocked from being moved leftward thanks to the frictional force that keeps it in place being greater than the spring force. The disengaged position is shown in Fig. 8.

In this way, the stop ring 19a obtains an axial position that limits the stroke length to what is necessary.

An additional alternative embodiment is illustrated in Figs. 10 and 11 , where Fig. 10 shows the disc clutch in the disengaged position and Fig. 11 in the engaged position.

The stop ring 19b shown in more detail in Figs. 12 and 13 has, in this example, the inclined projections 22b thereof directed radially outward and abuts against the inside of the axially directed flange 21 of the pressing body 15. Here, the impact ring 18b is formed as a ring-shaped radial flange of the driven clutch holder 11. In the disengaged position in Fig. 10, the stop ring 19b abuts against the impact ring 18b on the driven clutch holder 11 and thus limits the return movement of the pressing body 15.

As is seen in Figs. 10 and 11 , the stop ring 19b is applied to the inside of the flange 21 of the pressing body 15 with the oblique direction of the projections 22b to the right as seen from the inside and out. The oblique direction entails that the inner edge of the respective projection 22b in a barb-like way is pressed against the inside of the flange 21 , which results in great resistance to rightward

movement of the stop ring. In the other direction, the resistance to movement is considerably lower since the projections 22b then can slide against the inside of the flange 21. The inside of the stop ring 19b abuts against the outside of the driven clutch holder 11 so that the ring is clamped between the flange 21 and the driven clutch holder 11. Adjustment of the axial position of the stop ring 19b is effected by the stop ring 19b, upon mounting of the disc clutch, being preliminary placed further out to the right in the flange 21 than what is shown in the figures. Upon initial actuation of the disc clutch, the pressing body 15, by virtue of the force from the spring 17, is situated further to the left than what is shown in the figures, and the hydraulic piston 13 starts from a position situated correspondingly further to the left at a principally full stroke length. When the chamber 14, upon this initial engagement movement, is pressurized and the hydraulic piston 13 is displaced rightward, a carrier ring 24b on the driven clutch holder will limit the movement of the stop ring 19b, i.e., so that a relative motion between the flange 21 and the stop ring 19b occurs in the direction that the stop ring 19b is easily displaceable. Upon completed engagement movement, the position shown in Fig. 11 is reached.

Then, when disengagement occurs as the chamber 14 is pressure-released and the pressing body 15 is displaced leftward due to the spring 17, the stop ring 19b follows in the return movement. When the stop ring 19b reaches the impact ring 18b and contacts the same, continued movement of the stop ring 19b is blocked and thereby also that of the pressing body. This is due to the strong resistance of the stop ring 19b described above to move leftward in relation to the flange 21 , which the spring force from the spring 17 cannot overcome. The disc clutch is now in the disengaged position (Fig. 10).

Yet an alternative is illustrated in Figs. 14 and 15, where Fig. 14 shows the disc clutch in the disengaged position and Fig. 15 in the engaged position.

In this example, the stop means has a plurality of stop rings 19c, e.g., eight, arranged along a circle concentric with the principal axis of the disc clutch. Each stop ring 19c is attached to a cylindrical pin 25 by a friction joint of the similar kind as the one described in connection with Figs. 3 and 5, and the stop ring 19c has the corresponding inwardly directed projections as the stop ring 19 of Figs. 3 and 5 that is illustrated in more detail in Figs. 6 and 7. However, it should be appreciated that the stop ring 19c has a considerably smaller diameter than the stop ring 19 in Figs. 6 and 7. The oblique direction of the projections on each stop ring 19c is such that the resistance to relative motion of the stop ring 19c to the left in the figures in relation to the pin 25 is considerably greater than such a relative motion to the right, thanks to the previously described barb action.

Each pin 25 is fixedly connected with the driven clutch holder 11 and can thereby be regarded as a part of the same. The pins 25 extend through openings 26 in the pressing body 15. Furthermore, the pressing body 15 has a radial circumferential groove 27 on the side turned away from the clutch pack, whereby a radial flange 24c is formed, and in which flange each opening 26 has a continuation 28. Accordingly, in one direction, the groove 27 is limited by the flange 24c and in the other one by an opposite wall 18c of the pressing body. The ring-shaped wall 18c constitutes impact means 18c for the co-operation with the stop rings 19c.

When the disc clutch is to be disengaged from the situation illustrated in Fig. 15, the pressing body 15 is moved leftward by the spring 17 and thereby also the impact means 18c. When the impact means 18c in that connection has reached up to the stop ring 19c, as is shown in Fig. 14, continued movement is prevented and the pressing body 15 and the hydraulic piston 13 assume an axial position defined by the stop device 18c, 19c. Without the stop ring 19c, the pressing body 15 and the hydraulic piston 13 would have, because of the force from the spring 17, continued to be displaced leftward as far as allowed by the stroke length of the hydraulic piston.

By the fact that the stop device 18c, 19c thus limits the return movement of the hydraulic piston, the stroke length required when the disc clutch is to be

reactuated becomes shorter than what would be the case without the stop device 8c, 19c. Thereby, the engaging time becomes correspondingly shorter.

The distance between the impact means 18c and each stop ring 19c in the engaged state (Fig. 15) is adjusted so that it corresponds to the distance required to bridge the clearance of the clutch pack. The adjustment of the distance is provided by adjustment of the axial position of each stop ring 19c on the pins 25 of the driven clutch holder 11.

Adjustment of the axial position of each stop ring 19c is effected by each stop ring 19c, upon mounting of the disc clutch, being preliminary placed further out to the left on the respective pin 25 than what is shown in the figures. Upon initial actuation of the disc clutch, in that connection, also the pressing body 15, by virtue of the force from the spring 17, is situated further to the left than what is shown in the figures, and the hydraulic piston 13 starts from a position situated correspondingly further to the left at a principally full stroke length. When the chamber 14, upon this initial engagement movement, is pressurized and the hydraulic piston 13 is displaced rightward, the flange 24c will displace each stop ring 19c in the same direction, i.e., the direction in which the stop ring is easily displaceable. Upon completed engagement movement, the position shown in Fig. 15 is reached.

Then, when disengagement occurs as the chamber 14 is pressure-released, the pressing body 15 is displaced leftward due to the spring 17. When the impact means 18c reaches the stop rings 19c and contacts the same, continued movement of the pressing body 15 is blocked. This is due to the strong resistance of each stop ring 19 described above to move in the direction that the spring force from the spring 17 cannot overcome. The disc clutch is now in the disengaged position (Fig. 14).

Claims

1. Supercharger having two rotors (4, 5) engaging into each other and provided with a disc clutch, which disc clutch comprises:

- driving clutches (9) having a driving clutch holder (8) connected with a drive shaft (7)

- driven clutches (12) having a driven clutch holder (11 ) connected with one of the rotors (4, 5)

- an axially displaceable pressing body (15) arranged for the

compression of the clutches (9, 12) upon actuation,

- actuation device (13) for the actuation of the pressing body (15), and

- spring means (17) for the deactuation of the pressing body (15) characterized in that the disc clutch comprises a stop device (18, 18b, 18c,19, 19a, 19b, 19c) for the limitation of the axial movement of the pressing body (15) in the deactuation direction, which stop device (18, 18b, 18c, 19, 19a, 19b, 19c) comprises impact means (18, 18b, 18c) and stop means (19, 19a, 19b, 19c), one of the impact means and the stop means being connected with the driven clutch holder (11 ) and the other one of the impact means and the stop means being connected with the pressing body (15), the connection of the impact means (18, 18b, 18c) being axially fixing and the connection of the stop means (19, 19a, 19b, 19c) being provided by a friction joint.

2. Supercharger according to claim 1 , characterized in that the stop means (19, 19a, 19b, 19c) comprises at least one stop ring (19, 19a, 19b, 19c).

3. Supercharger according to claim 2, characterized in that the friction joint of each stop ring (19, 19a, 19b 19c) is formed between a radial outside or inside of the stop ring (19, 19a, 19b, 19c) and a radial inside or outside, respectively, of the one of the driven clutch holder (11 ) and the pressing body (15) with which the stop ring (19, 19a, 19b, 19c) is connected.

4. Supercharger according to claim 2 or 3, characterized in that the stop ring (19, 19b, 19c) is provided with means (22, 22b) for the provision of differently strong frictional force in different axial directions, where the frictional force that keeps the stop ring (19, 19b, 19c) from being displaced in the motion direction of the pressing body (15) upon actuation is smaller than the frictional force that keeps the stop ring (19, 19b, 19c) from being displaced in the opposite direction.

5. Supercharger according to claim 4, characterized in that the radial side of each stop ring (19, 19b, 19c) that constitutes one part of the friction joint is asymmetrical for the provision of said differently great frictional force.

6. Supercharger according to claim 5, characterized in that the radial side of each stop ring (19, 19b, 19c) that constitutes one part of the friction joint is provided with obliquely directed projections (22, 22b), which are inclined in the motion direction of the pressing body (15) upon deactuation.

7. Supercharger according to claim 2 or 3, characterized in that the friction joint is a compression joint having a pressing force that is greater than the maximum axial force of the spring means (17).

8. Supercharger according to any one of claims 1-7, characterized in that the actuation device (13) comprises a hydraulic piston (13).

9. Supercharger according to anyone of claims 1-8, characterized in that the supercharger comprises a screw compressor.

10. Disc clutch comprising

- driving clutches (9) having a driving clutch holder (8)

- driven clutches (12) having a driven clutch holder (11 )

- an axially displaceable pressing body (15) arranged for the

compression of the clutches (9, 12) upon actuation,

- actuation device (13) for the actuation of the pressing body (15), and

- spring means (17) for the deactuation of the pressing body (15) characterized in that the disc clutch comprises a stop device (18, 18b, 18c, 19, 19a, 19b, 19c) for the limitation of the axial movement of the pressing body (15) in the deactuation direction, which stop device (18, 18b, 18c, 19, 19a, 19b, 19c) comprises impact means (18, 18b, 18c) and stop means (19, 19a, 19b, 19c), one of the impact means and the stop means being connected with the driven clutch holder (11 ) and the other one of the impact means and the stop means being connected with the pressing body (15), the connection of the impact means (18, 18b, 18c) being axially fixing and the connection of the stop means (19, 19a, 19b, 19c) being provided by a friction joint.

11. Disc clutch according to claim 10, characterized in that the disc clutch comprises the features defined for the disc clutch according to any one of claims 2-8.