Power transmitting apparatus

Abstract: An apparatus for transmitting power from a driving side to a driven side, having a fluid joint means and a rolling bearing clutch (C L ) in parallel, the power being transmittable via said fluid joint means and/or said clutch (C L ), wherein said clutch (C L ) includes an inner and an outer ring (58, 59) having track surfaces (58a, 59a) of hyperboloidal contour, and a plurality of rollers (60) interposed between the outer periphery of said inner ring (58) and the inner periphery of said outer ring (59) at an inclination to the center axis of said rings (58, 59), said clutch (C L ) being operated by moving the track surfaces (58a, 59a) near to each other with thrusting means or away from each other, so that when said rings (58, 59) are relatively rotated in one direction, said clutch (C L ) is held locked, while it is freely rotatable in the opposite direction. For transmitting power without slip loss, said rings (58, 59) are locked by a thrust while being relatively rotated opposite to the locking direction, said rings (58, 59) becoming freely rotatable by releasing said thrusting means, whereby said clutch (C L ) is held in the OFF position.

Description: The present invention relates to a power transmitting apparatus according to the preamble of patent claim 1. The power transmitting apparatus, such as a fluid coupling, a torque converter or the like for transmitting power from a driving side to a driven side using fluid joint means, of the present invention can mechanically connect a driving side to a driven side with a clutch mechanism interposed therebetween and assures that a power transmitting efficiency can be improved, without any slip loss, by equalizing the rotational speed of input from a prime mover to the rotational speed of a unit to be driven. A power transmitting apparatus such as a fluid coupling, a torque converter or the like, for transmitting power from a driving shaft to a driven shaft via fluid filled in a casing where a pump impeller is connected to a driving shaft and a turbine impeller is connected to a driven shaft, is known. The Document DE-A-3144194 describes a hydraulic torque converter for motor vehicles for transmitting the engine torque to a driven wheel by means of a hydraulic fluid and/or a mechanical overrunning clutch. The mechanical clutch has an annular driving clutch member with a conical track on the inner periphery and a driven clutch member with a conical track on the outer periphery, the two tracks being parallel to and facing each other. A roller cage supporting a plurality of shock-absorbing, tapered, cylindrical rollers of a resilient material is arranged between the two tracks. When the clutch is not in operation, each roller is at a predetermined angle of inclination to the generatrix of a conical surface having the same angle as the conical tracks and passing through the middle of the roller. The driven clutch member is connected to a piston which is slidingly seated in a hydraulic chamber and urged in a direction away from the driving clutch member by the force of a spring. The introduction of hydraulic fluid into the chamber causes the piston to urge the driven clutch member close to the driving clutch member against the force of the spring, bringing the rollers into pressure contact with the track surfaces. When the driving clutch member is driven in one direction relative to the driven member, the rollers are rotated and increase their angles of inclination to the generatrix, causing the two clutch members to be mechanically connected. When the driving clutch member is driven in the opposite direction, the rollers are rotated in a direction to decrease the angles of inclination. As the angles become zero, a clearance is formed between the rollers and the track surfaces, so that the transmission of torque is interrupted. A description of prior art will be made below with respect to a power transmitting apparatus which is exemplified by a fluid coupling. When the rotational speed of a unit or a driven shaft is to be controlled by means of a fluid coupling, the rotational speed on a loading side or a driven shaft can be steplessly changed from a minimum rotational speed to a maximum rotational speed by shifting a scoop tube, or the minimum rotational speed or the maximum rotational speed of the driven shaft can be obtained by feeding working oil to the fluid coupling formed by an impeller, a runner and an impeller casing or by interrupting the feeding of the working oil to the fluid coupling. In any case, when the driven shaft is rotated at a maximum rotational speed, the maximum rotational speed of the driven shaft is lower than that of the driving shaft or an input rotational speed of the prime mover such as a motor or an engine usually by about 3 % owing to slippage. This slippage can not be avoided when the rotational speed is controlled by a fluid coupling. Therefore, the fluid coupling efficiency is reduced owing to slippage by a quantity corresponding to the slip percentage and the larger the transmitting power, the larger the loss of power. The present invention was made to overcome the aforementioned problems and its object resides in providing a power transmitting apparatus which includes a clutch mechanism for mechanically connecting the driving side to the driven side and which assures that slip loss is eliminated by equalizing the rotational speed of input from a prime mover to the rotational speed of a unit to be driven, resulting in an improved power transmitting efficiency. According to the invention this object is achieved with a power transmitting apparatus having the features of patent claim 1. The present invention provides a power transmitting apparatus for transmitting power from a driving side to a driven side using fluid joint means, wherein a rolling bearing clutch including an inner ring, an outer ring and a plurality of rollers interposed between the outer periphery of the inner ring and the inner periphery of the outer ring is disposed between the driving side and the driven side, the rolling bearing clutch being ON/OFF operated by allowing the track surfaces of the inner ring and the outer ring to move close to each other or away from each other, whereby the driving side and the driven side can be mechanically connected to each other not via fluid joint means by shifting the rolling bearing clutch to the ON position. The rolling bearing clutch is constructed in such a way that the inner and outer rings are locked by imparting a thrust force to the inner or outer ring with the thrusting means while the inner and outer rings are relatively rotated in the rolling direction opposite to the locking direction, whereby the rolling bearing clutch is held in the ON position. The inner and outer rings are freely rotatable by releasing the thrusting means from the thrust position, whereby the rolling bearing clutch is held in the OFF position. According to the present invention, a power transmitting apparatus such as a fluid coupling, a torque converter or the like for transmitting power from a driving side to a driven side makes it possible to mechanically connect the driving side to the driven side not via fluid joint means because the rolling bearing clutch is disposed between the driving side and the driven side. Thus, slip loss of the fluid joint means can be eliminated by equalizing the rotational speed of input from the prime mover to the rotational speed of a unit to be driven, resulting in improved power transmitting efficiency. The above and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which preferred embodiments of the present invention are shown by way of illustrative examples. Fig. 1 is a sectional view which shows an embodiment of a power transmitting apparatus according to the present invention. Fig. 2 is a diagram of the working oil circuit in the power transmitting apparatus shown in Fig. 1. Figs. 3(a) to 3(c) are illustrative views of a known rolling bearing clutch, wherein Fig. 3(a) is a partially sectioned perspective view of the rolling bearing clutch and Figs. 3(b) and 3(c) are diagrams showing the operation of the rolling bearing clutch. The present invention will now be described in detail hereinafter with reference to the accompanying drawings which illustrate preferred embodiments thereof. In these embodiments, description will be made on the power transmitting apparatus exemplified by a fluid coupling. Fig. 1 is a sectional view which shows the entire structure of the fluid coupling. In Fig. 1 reference numeral 1 denotes a driving shaft, and driven shaft 4 is arranged adjacent to the driving shaft 1. The driving shaft 1 is rotatably supported in a bearing metal sleeve 13 disposed in a bearing casing 18, whereas the driven shaft 4 is rotatably supported in bearing metal sleeves 15, 16 disposed in a bearing casing 19. The bearing casings 18 and 19 are held in position by a bearing casing retainer 20. An impeller 2 is connected to the driving shaft 1, and a runner 3 is connected to the driven shaft 4. An impeller casing 5 is fixed to the impeller 2, and an outer annulus 24 is fixed to the impeller casing 5. An outer sleeve 25 is attached to the outer annulus 24, and an inner annulus 6 is attached to the outer sleeve 25. A rolling bearing clutch C L is disposed in the space surrounded by the impeller casing 5, the outer annulus 24 and the inner annulus 6. A ball spline mechanism 26 allows the axial relative movement between the outer ring 9 and the outer sleeve 25 while preventing relative rotational movement therebetween. A space surrounded by the outer sleave 25 and the inner annulus 6 constitutes a cylinder portion, and a piston 7 is axially displaceably disposed in the cylinder portion. A clutch ON/OFF working oil chamber is defined between the inner surface of the cylinder portion and the piston 7 so that working oil is fed to the working oil chamber via working oil feeding passages 31a, 31b, 31c and 31d, each formed in the bearing casing 19 and the inner annulus 6. The working oil feeding passage 31a is hydraulically connected via a pipe to a hydraulic pump (as will be described later). A plurality of balls 23 are interposed between the piston 7 and the outer ring 9 which allow the relative rotational movement therebetween. A radial bearing 32 is interposed between the outer annulus 24 and the inner ring 8. The thrust force of the driving shaft 1 is borne by a thrust bearing 14, and the thrust force of the driven shaft 4 is borne by a thrust bearing 17. In addition, a plurality of nozzles 21 are disposed along the outer periphery of the impeller casing 5. A working oil chamber of the fluid coupling impeller is constituted by the impeller 2, the runner 3 and the impeller casing 5. The working oil is fed to the fluid coupling impeller working oil chamber via a working oil feeding passage 18a of the bearing casing 18 and an oil feeding hole 2a of the impeller 2. As shown in Fig. 2, the passage for feeding the working oil to the fluid coupling impeller working oil chamber comprises a passage I 1 which includes an opening/closing control valve f 1 adapted to quickly perform full opening and full closing and a maximum oil flow rate adjusting orifice j, and a passage I 2 which includes an opening/closing control valve f 2 disposed in parallel with the control valve f 1 to bypass the latter and a minimum oil flow rate adjusting orifice h. As an oil pump c is driven, the working oil is fed to the working oil chamber from an oil tank a via a strainer b through the passage I 1 or I 2 , the oil feeding passage 18a of the bearing casing 18 on the driving side and the oil feeding hole 2a of the impeller 2. The working oil in the working oil chamber is discharged to the outside via the nozzles 21. As desired, a hydraulic pressure adjusting relief valve d and an oil cooler e are arranged. A flow rate of working oil fed to the working oil chamber is determined by the maximum oil flow rate adjusting orifice j when the control valve f 1 is fully opened, and a minimum flow rate is determined by the minimum oil flow rate adjusting orifice h when the control valve f 1 is fully closed and the control valve f 2 is fully opened. Thus, the rotational speed of the unit is driven at a maximum rotational speed when the control valve f 1 is fully opened, and it is driven at a minimum rotational speed when the control valve f 1 is fully closed and the control valve f 2 is fully opened. On the other hand, the feeding of the working oil to the clutch ON/OFF working oil chamber 30 is achieved by the oil pump c through a passage I 3 , a control valve k and communication passages 31a to 31d (see Fig. 1). Next, a known rolling bearing clutch will be described below in detail. For example, the structure as shown in Fig. 3 is known as a rolling bearing clutch. Specifically, the rolling bearing clutch includes an inner ring 100, an outer ring 101 and a number of rollers 104 interposed between the outer periphery of the inner ring 100 and the inner periphery of the outer ring 101 as shown in Fig. 3(a). The rollers 104 are arranged with a predetermined twist angle β relative to a center axis X of the inner and outer rings 100 and 101 as shown in Fig. 3(b). A track surface 102 of the outer periphery of the inner ring 100 is convergent in the form of a substantially circular conical taper surface, and a track surface 103 of the inner periphery of the outer ring 101 is designed also in the form of a substantially circular conical taper surface corresponding to the track surface 102 of the inner ring 100. More precisely, since the track surfaces 102 and 103 are under a condition that the rollers 104 come into line contact with them, they respectively assume a single hyperboloid contour that is a locus which is scribed by turning the rollers 104 about the center axis X. The track surfaces 102 and 103 of the inner and outer rings 100 and 101 are inclined at a predetermined socket angle  relative to the center axis X. The rollers 104 come into contact with the track surfaces 102 and 103 of the inner and outer rings 100 and 101 with a predetermined twist angle β so that as the inner and outer rings 100 and 101 are rotated, the rollers 104 spirally roll between the inner and outer rings 100 and 101. As shown in Fig. 3(b), when the inner ring 100 is rotated in such a direction that it is squeezed or advanced in the outer ring 101, a clutch component F1 which serves to allow the inner ring 100 and the outer ring 101 to move near to each other in the axial direction due to the rolling of the rollers 104 appears so that the rollers 104 between the inner ring 100 and the outer ring 101 are brought into a locked position, enabling torque to be transmitted. On the other hand, when the inner ring 100 is rotated in the reverse direction as shown in Fig. 3(c), a component F2 which serves to allow the inner and outer rings 100 and 101 to be parted away from each other appears so that the rollers 104 can rotate freely. The known rolling bearing clutch explained above is utilized as a one-way clutch which transmits torque in one direction and freely rotates in the other direction by utilizing the aforementioned characteristics. It should be noted that a plurality of preliminary pressure springs 105 for imparting light preliminary pressure between the inner ring 100 and the outer ring 101 are arranged between the inner ring 100 and the outer ring 101 so as to allow the rollers 104 to come into initial contact with the inner and outer rings 100 and 101. Next, operation of the fluid coupling constructed as above will be explained. When the control valve f 1 and a control valve K are closed and the control valve f 2 in Fig. 2 is opened while the prime mover is rotated at a rated rotational speed, working oil is fed at a specific flow rate via a minimum oil flow rate adjusting orifice h to the fluid coupling impeller working oil chamber formed by the impeller 2, the runner 3 and the impeller casing 5, which causes a unit to be driven at a minimum rotational speed. When the control valve f 1 is opened and the control valve k is closed, working oil is fed at a fixed rate defined by a maximum oil flow rate adjusting orifice j to the fluid coupling impeller working oil chamber so that the rotational speed of the unit is driven at a maximum rotational speed while including a slippage caused by the fluid coupling. A centrifugal force Px in the working oil in the chamber 30 for actuating the rolling bearing clutch C L is represented by the following formula. Px = γω 2 (r 2 -r x 2 )/2g Here, γ denotes a specific weight of the working oil, and ω denotes a rotational angular speed. When the working oil is fed by a flow rate Q o , an oil film having an innermost peripheral radius r x and an outermost peripheral radius r is formed in the working oil chamber 30. The outermost peripheral radius r is determined by the outer peripheral wall of the working oil chamber 30. When the working oil feeding flow rate Q o is increased, r x is decreased, and when Q o is decreased, r x is increased. As is apparent from the above description, it is possible for the necessary centrifugal pressure P x to be established by controlling the working oil feeding flow rate Q o . In the embodiment shown in Fig. 1, the rolling bearing clutch C L is constructed such that the clutch is shifted to the ON position by imparting a thrust force to the outer ring by thrusting means while the inner and outer rings are relatively rotated in the opposite rolling direction to the locking direction, and it is used as a one-way clutch. The structure of the track surfaces of the inner and outer rings is entirely the same as the conventional one but in contrast thereto, an untwisting operation is not required. That is, in the conventional rolling bearing clutch, since the rollers squeeze between the inner and outer rings in the clutch ON position, an untwisting operation is necessary to shift the clutch from the clutch ON position to the clutch OFF position. The rolling bearing clutch C L includes an inner ring 58, an outer ring 59, a plurality of cylindrical rollers 60, and a retainer 62 for holding the rollers 60 at predetermined positions. The inner ring 58 is connected directly to the runner 3. The outer ring 59 is connected to the outer sleeve 25 via the ball spline mechanism 26, and the outer ring 59 is displaceable relative to the outer sleeve 25 in the axial direction while it is rotated together with the outer sleeve 25. In addition, the outer annulus 24 is fixed to the impeller casing 5. A plurality of preliminary pressure springs 61 are interposed between the opposing surfaces of the outer ring 59 and the outer sleeve 25 so that the outer ring 59 is thrust to the inner ring 58 in the axial direction so as to impart preliminary pressure to each roller 60. The structure of track surfaces 58a and 59a of the inner ring 58 and the outer ring 59 is entirely the same as that of the conventional ones having a hyperboloid contour and description of the structure of the track surface is herein omitted. In this embodiment, the driving shaft 1 is relatively rotated only in the rolling direction opposite to the locking direction of the inner and outer rings of the rolling bearing clutch C L . When the rolling bearing clutch C L is held in the OFF position, even though the driving shaft 1 is rotated, the outer ring 59 is rotated together with the outer annulus 24. However, as the rollers 60 roll, since a rolling component effective for parting the inner and outer rings 58 and 59 away from each other is caused, the rollers 60 are rotated freely without causing any rotation of the inner ring 58. When the control valve k is opened while the foregoing position is maintained, the working oil is fed to the working oil chamber 30 so that the pressure is caused in the working oil in the working oil chamber 30 by the centrifugal force. The piston 7 is thus thrust in the leftward direction by the pressure and the track surfaces of the outer ring 59 and the inner ring 58 come near to each other, causing the rolling bearing clutch C L to be shifted to the ON position so that the driving shaft 1 and the shaft 4 of a unit to be driven are mechanically coupled to each other. When the feeding of the working oil to the working oil chamber 30 is interrupted by closing the control valve k during torque loading, the working oil in the working oil chamber 30 is discharged from the nozzles 28 by the centrifugal force so that the piston 7 is released from the thrusting force. Thus, as the rollers 60 roll, a component effective for parting the inner and outer rings 58 and 59 away from each other appears, causing the rollers 60 to be rotated freely, whereby the rolling bearing clutch C L is immediately shifted to the OFF position. When the fluid coupling shown in Figs. 1 and 2 is applied to a pump for a descaling apparatus adapted to repeat high speed operation (loading operation) and low speed operation (no loading operation) for removing scale on the surface of a steel in a steel plant, operation can be performed at a minimum rotational speed at the time of no loading, and operation can be performed at the same rated rotational speed as that of a prime mover without including slip loss because of the use of a fluid coupling at the time of loading. Consequently, a large saving in energy can be obtained by simple control. In the embodiments shown in Figs. 1 and 2, an example where the power transmitting apparatus of the present invention is applied to the fluid coupling is shown. However, the present invention should not be limited only to a fluid coupling but it can equally be a torque converter. As described above, according to the present invention, a power transmitting efficiency can be improved without any slip loss by mechanically connecting the driving side to the driven side. When a fluid coupling is applied to a pump for a descaling apparatus in a steel plant as one example of the present invention, operation can be performed at a minimum rotational speed at the time of no loading, and operation can be performed at the same rated rotational speed as that of a prime mover without including slip loss at the time of loading. Consequently, a large saving in energy can be obtained by simple control. Note: Performance of the present invention involves performance of the invention of the copending application EP 98 114 814.1 of even date.

Claims: A power transmitting apparatus for transmitting power from a driving side to a driven side, and having a fluid joint means and a rolling bearing clutch (C L ) provided in parallel therebetween for transmitting power from said driving side to said driven side via said fluid joint means and/ or said bearing clutch means, said rolling bearing clutch (C L ) including an inner ring (58), an outer ring (59), and a plurality of rollers (60) interposed between the outer periphery of said inner ring (58) and the inner periphery of said outer ring (59), and being disposed between the driving side and the driven side for performing ON/OFF operations by allowing the track surfaces (58a, 59a) of said inner ring (58) and said outer ring (59) to move near to each other or away from each other, the driving side and the driven side being mechanically connectable to each other not via fluid joint means by shifting said rolling bearing clutch (C L ) to an ON position, wherein said power transmitting apparatus is provided with thrusting means for shifting the track surfaces (58a, 59a) of said inner ring (58) and said outer ring (59) in said rolling bearing clutch (C L ) to move near to each other, wherein said rolling bearing clutch (C L ) is constructed in such a way that said rollers (60) are inclined with a predetermined twist angle (β) relative to the center axis of said inner and outer rings (58, 59), each of the track surfaces (58a, 59a) of said inner ring (58) and said outer ring (59) exhibits a hyperboloid contour that is a revolving locus scribed when said rollers (60) are turned about the center axis, and when said inner and outer rings (58, 59) are relatively rotated in one direction, said rolling bearing clutch (C L ) is held in the locked position while it is freely rotatable in the opposite direction, characterized in that said inner and outer rings (58, 59) are locked by thrusting said inner or outer ring (58, 59) with said thrusting means while said inner and outer rings (58, 59) are relatively rotated in the rolling direction opposite to the locking direction, whereby said rolling bearing clutch (C L ) is held in the ON position, and said inner and outer rings (58, 59) are freely rotatable by releasing said thrusting means from the thrust position, whereby said rolling bearing clutch (C L ) is held in the OFF position. The power transmitting apparatus as claimed in claim 1, wherein said thrusting means comprises a piston (7) that is engageable with said outer ring (59) and means for applying fluid pressure to the pressure receiving surface of said piston (7). The power transmitting apparatus as claimed in claim 2, wherein said means for applying fluid pressure comprises a working oil chamber (30) defined between the pressure receiving surface of said piston (7) and a cylinder portion adapted to receive said piston (7), a working oil feeding portion for feeding working oil to said working oil chamber (30), and a nozzle (28) for discharging the working oil from said working oil chamber (30), said fluid pressure being caused by the centrifugal force applied to the working oil in said working oil chamber (30). The power transmitting apparatus as claimed in claim 2, wherein a plurality of balls (23) are interposed between said outer ring (59) of said rolling bearing clutch (C L ) and said piston (7).

Inventors: EBISUI MASAHIKO, HATTORI KAZUO, KIMURA KATSUMI, OGATA HIROSHI, OTSUKA MICHIO, EBISUI, MASAHIKO, HATTORI, KAZUO, KIMURA, KATSUMI, OGATA, HIROSHI, OTSUKA, MICHIO
Applicants: EBARA CORP, EBARA CORPORATION
Application year: 1996
Main classification: F16D41
IPC codes: F16H45, F16D41