TRANSMISSION INCLUDING A TWO-PART CLUTCH ARRANGEMENT

Abstract: The invention relates to a transmission including a two-part clutch arrangement (13) having one clutch part (8, 16) connected to a driven input shaft (7) of a working machine, for instance a screw compressor, which input shaft is rotatably journalled by means of a bearing (15), and the other clutch part (18) connected to a driving means, for instance a belt pulley (19), wherein a pressure plate (26) is axially movable in relation to the clutch parts and is arranged to exert an axial pressure to the clutch arrangement (13) for engagement of it. In order to achieve a smallest possible overall length said one clutch part (8, 16) is secured to the input shaft (7) the bearing arrangement (15) of which having not only a radial forces withstanding function but also a function to withstand axial forces adapted to the additional axial force from the pressure plate, and said second clutch part (18) with an end part facing the input shaft (7) is journalled by a radial bearing (33) in a recess (34) in a central part of said one clutch part (8, 16) connected to the input shaft (7) of the working machine.

Description: Transmission including a two part clutch arrangement. The present application relates to a transmission of the kind set forth in the preamble of the attached patent claim 1. A transmission of this kind usually is very space consuming in relation to the size of working machine with which the transmission is intended to cooperate. This is true especially in case the transmission is intended for driving a supercharger of an internal combustion engine. In most cases an electromagnetic clutch device is used, which is easy to build-in in the transmission. Such a clutch device is not suitable, however, in case of frequent engagements and disengagements of the clutch device. Therefore a mechanical clutch device is to be preferred. A drawback with this is that a comparatively high clutch pressure is required, which results in problems with the bearing devices. A clutch device of this type is shown in SE 9501501-2. A disadvantage with that design is, that the overall length of the clutch device will become comparatively long depending a.o.on the fact that large axial pressure forces from the pressure plate of the clutch device have to be withstanded by a heavy thrust bearing requiring a large axial space. A long overall length makes the incorporating of the transmission in the working machine difficult, and involves increased mechanical stresses. The object of the invention is to achieve a transmission of the kind mentioned in the introduction above, with which the above mentioned disadvantages are eliminated, and which, moreover, is specially uncomplicated to mount on the working machine. This is obtained, according to the invention, in that the transmission has got the characteristics set forth in claim 1. The axial forces of the clutch device are arranged to be withstood in a practical way by a present radial bearing for journalling of the driven input shaft of the working machine being replaced by an angular contact bearing designed to withstand also the additional axial force of the clutch device. By that, a separate space consuming thrust bearing for the clutch device is eliminated, and if, moreover, the necessary radial bearing for the inner end of the clutch device connected with the driving device is situated directly in a central recess in the clutch device connected with driven shaft, the overall length of the transmission will be smallest possible. A disc clutch of the design set forth in claim 2 is suitably used as clutch device, which, if the driving device, for instance a belt pulley, with the attached clutch part are journalled in an end wall part of the working machine, permits withdrawal of these parts together with the end wall part from the working machine due to the fact that the two parts of the clutch device are dismountable. Especially in a screw compressor which is provided with synchronizing wheels and possibly accompanying bearings the space for a clutch device will be very limited in radial direction. It is therefore advantageous at an ernbodi ent according to claim 2 to utilize the axial studs for placing return springs acting between the clutch parts as stated in claims 3 or 4. For operating the pressure plate of the clutch device this is suitably moved by a hydraulically or pneumatically controlled annular piston, as stated in claim 5. The transmission is particularly suitable for driving a mechanical supercharger for an internal combustion engine, in which case the pressure fluid suitably consists of oil from the pressure oil system of the engine, as stated in claim 6. The invention is described in more detail in the following with reference to the attached drawings, which show two examples of eπibodiments of a transmission according to the invention applied to a small screw compressor to be used as a supercharger for internal combustion engines, and in which Figure 1 is a longitudinal sectional view of a part of the compressor with accompanying transmission, Figure 2 is a cross sectional view through the clutch device, and Figure 3 is a longitudinal view through a part of the compressor in Fig.l but showing an alternative design of the transmission. The drawing shows a screw compressor 1 with a rotor housing 2 at one of which ends an end wall 3 is secured. In the end wall 3 and the opposite end wall 4 are a male rotor 5 and a female rotor 6 rotatably journalled. The compressor is driven by an input shaft 7 which is secured to a synchronizing gear 8 and which forms a part of the shaft 9 of the female rotor 6. The synchronizing gear of the male rotor is designed 10 and is secured to the shaft 11 of the male rotor. An end wall part 12 is secured to the end wall 3 forming a cap in which a clutch means 13 is journalled by two bearings 14 and 15. The clutch means 13 has two main parts: one part 16, which is integrated with the synchronizing gear 8, and one part 18, which extends out of the end wall part 12 and is secured to a belt pulley 19. The clutch part 16 is as usual provided with annular discs 20 which are positioned between corresponding discs 21 of the clutch part 18. A number of pressure springs 22 strive to keep the clutch parts and accordingly the discs 20,21 apart. A cylinder chamber 23 is designed in the end wall part 12, in which chamber an annular piston 24 is journalled axially displaceable. A pressure fluid channel extends through the wall of the end wall part 12 to the cylinder chamber 23. A thrust bearing 27 is positioned between the annular piston 24 and a pressure plate 26 located at an outer disc 20. At supply of pressure fluid having a requested pressure to the cylinder chamber 23 the annular piston 24 is displaced towards the thrust bearing 27, which in turn is displaced a short distance pushing the pressure plate 26 against the discs 20,21, which in a manner known per se are pressed together forming a fixed connection between the clutch parts 18 and 16. As shown in Fig.2 the clutch part 16 comprises six studs 28 extending axially away from the gear 8 with intermediate spaces 29. Axial borings 30 are made in the studs 28, in which borings the pressure springs 22 are located pushing against the periphery of the pressure plate 26. Projections 31 of the discs 20 protrude into the interspaces 29 preventing the discs 20 from turning in relation to the clutch part 16 but axially movable in relation to said clutch part. The discs 21 are by a splined coupling 32 prevented from turning in relation to the clutch part 18 which inner part, facing the gear 8, is journalled by a needle bearing 33 in a recess 34 in the centre of the gear 8. At supply of pressure fluid to the cylinder chamber 23 via channel 25, which, if the compressor is a supercharger of an internal combustion engine, suitably is connected via a valve device, not shown, to the pressure oil system of the engine, the annular piston 24 is pushed against the thrust bearing 27, which is displaced a short distance and pushes the pressure plate 26 against the discs 20,21. Thereby the gear 8 is pushed against the bearing 15 of the rotor 6, which bearing is dimensioned to withstand not only the radial forces from the rotor but also the axial forces from the clutch means 13. This arrangement together with the journalling of the inner end of the clutch part 18 in the recess 34 in the centre of the gear 8 reduces the overall length of the transmission considerably. In compressors with small rotor and synchronizing gear diameters there are problems with the radial space for the clutch means 13. In that case it is suitable to modify the studs 28 and springs 22 as shown in Fig.3. The studs 28 are designed essentially thinner, and the borings 35 for the springs 22 are made in the pressure plate 26. The protruding ends of the springs 22 are fixed by pins 36 inserted in fine borings 37 in the studs 28.

Claims: C L A I S 1. Transmission including a two part clutch arrangement (13) connecting a screw compressor (1) provided with synchronizing gears (8,10) with a driving means, for instance a belt pulley (19), characterized in that one of said synchronizing gears (8) is an integrated part of one part (16) of said two part clutch arrangement. 2. Transmission according to claim 1, characterized in that the clutch arrangement (13) is a disc clutch provided with a number of discs (20) with radial projections (31) round the periphery protruding between axial studs (28) located on the periphery of said one synchronizing gear (8). 3. Transmission according to claim 2, characterized in that axially positioned return springs (22) are located in borings (30) in at least some of the axial studs (28) acting against opposite parts of the periphery of a pressure plate (26) . 4. Transmission according to claim 2, charcterized in that axially positioned return springs (22) are located in borings (35) in the periphery of a pressure plate (26) acting against at least some of the axial studs (28), the end of each spring applied against a stud being guided by an axial pin (36) having one end inserted into an axial boring (37) in the stud and the other end inserted a bit into the centre of the spring (22). 5. Transmission according to any of claims 3-4, characterized in that the pressure plate (26) via a thrust bearing (27) is actuated by an annular piston (24), which is axially movable under the influence of a pressure fluid in a cylinder chamber (23) located in an end wall part (12) positioned on the screw compressor (1) . 6. Transmission, especially for driving a mechanical supercharger of an interior combustion engine, according to claim 5, characterized in that the pressure fluid consists of oil from the pressure oil system of the engine.

Inventors: ENGLUND ARNOLD, ENGLUND, ARNOLD
Applicants: ENGLUND ARNOLD, LYSHOLM TECHN AB, ENGLUND, ARNOLD, LYSHOLM TECHNOLOGIES AB
Application year: 1996
Main classification: F04C29
IPC codes: F02B39, F04B35, F04C18, F04C29, F16D25