TORQUE VARIATION ABSORBING DEVICE

Abstract: The torque variation absorbing device comprises a driving plate (2), a flywheel (6), and a spring mecha­ nism (12), a torque limiting mechanism (15) and a hystere­ sis mechanism (18) installed between the driving plate (2) and the flywheel (6). The flywheel (6) is divided into a flywheel body and a driven plate. The spring mecha­ nism (12) comprises a coil spring (13) and spring seats (14) disposed at both ends of said coil spring (13). The torque limiting mechanism (15) comprises driven disks (16). A part of the spring seat (14), which is opposed to the driving plate (2) has a projection formed thereon, while a part of the spring seat (14), which is opposed to the driven disks (16) has a recess (14b) formed thereon.

Description: The present invention relates to a torque variation absorbing device for an engine according to the preamble of claim 1. An engine for an automobile or an aircraft is equipped with a torque variation absorbing device for power transmission. The generic prior art offers such torque variation absorbing device as disclosed in document JP-A-5520930. Referring to Fig. 5 and 6, a device of the prior art his two inertia members, i.e., a driving plate 101 which is connected to a crankshaft of an engine and a flywheel 102 which is connected to the follower means and is rotatable with respect to the driving plate. Between the driving plate 101 and the flywheel 102, a spring mechanism 103 and a torque limiting mechanism 104 are installed. In this device the rotation of the crankshaft is transmitted to the flywheel 102 through the driving plate 101, the spring mechanism 103 and the torque limiting mechanism 104. Thus the torque variation is absorbed by the vibration system of these members. The conventional spring seat 108 of said spring mechanism (103) is formed such that both the contact portion for contacting the driving member (flat members 109, 110) and the contact portion for contacting the driven member (driven plates 111, 112) possess an identical shape having a semi-circular projection 108a, but when a vehicle runs, the projection 108a in contact with the driven member (driven plates 111, 112) of the spring seat 108 wears so heavily that a spring 103 comes into direct contact with the peripheral member, thereby destabilizing the hysteresis torque, and the torque variations cannot be well absorbed. Conceivably these problems will be reduced (a) when the driven plate is fabricated thicker or (b) when the semi-circular part of the spring seat is elongated in the circumferential direction. However, other problems such as increase of an axial dimension in the case of (a) and decreased strength of the driven plate in the case of (b) will occur. Furthermore in document US-A-4 351 168 there has been disclosed a torque variation absorbing device in case of which the spring seat is laterally provided with tabs as well as with a recess which can be brought into contact with the driving member of the device via protrusions. The driven disks are arranged on both sides of the driving member and can brought into contact with the radial facing of the spring seat by means of their facings. By means of this construction a centering of the driving member and the driven disks on the spring seat is achieved in order to prevent contact and wear between the driving member and the driven disks. It is the object of the present invention to provide a torque variation absorbing device in which the wear of the spring seat is reduced in such a manner that the performance characteristics of the torque variation absorbing device are stabilized. This object is achieved by means of the features indicated in the characterizing part of claim 1. According to these features, a concave recess located in the central portion of the spring seat is formed on the part of the spring seat which is opposed to and is able to contact the driven disk of the torque variation absorbing device. Particularly, a projection is formed on the part of the spring seat which is opposed to and is able to contact the driving plate and a recess is formed on the part of the spring seat which is opposed to and is able to contact the driven disk. Desirably, a rib is formed on the spring seat between the projection and the recess. Because the shape of the part of the spring seat which is opposed to the driven disk is formed approximately like a semi-circular recess, the contact area of it with the projection of the driven disk is increased, with the result that the pressure of the plane subjected to a centrifugal force due to rotation can be reduced and the wear of the spring seat can be reduced. Further, because the driving side of the spring seat is shaped convex at a position of the coil spring diameter and the driven side of it is formed concave at a position inside of the coil diameter of the coil spring, the coil spring can be made longer with an enlarged gap against the driven disk and accordingly the relative angular displacement between the driving side and the driven side can be increased, with the result that the natural frequency of the torque variation absorbing device can be decreased and the vibration absorbing effect can be increased. Besides, a rib formed at both sides of the recess on the spring seat will prevent the projection of the driven disk from moving and disengaging from the spring seat in the axial direction of the flywheel. These and other objects and advantages of the present invention will become more apparent and more radily appreciated from the following detailed description of the preferred exemplary embodiments of the present invention taken in conjunction with the accompanying drawings; wherein: Figure 1 is a sectional view taken along I - I in Fig. 2 of a torque variation absorbing device constructed in accordance with a preferred embodiment of the present invention; Figure 2 is a partially sectional elevation view showing internal mechanisms of the device in Fig. 1; Figure 3 is a diagram showing the torque transmission characteristic of the device of Fig. 1; Figure 4 is an oblique view showing the detail of the spring seat in the device of Fig. 1; Figure 5 is a sectional view of a conventional torque variation absorbing device; and Figure 6 is an oblique view of the spring seat in the device of Fig. 5. A torque variation absorbing device constructed in accordance with a preferred embodiment of the present invention will be described with reference to the drawings. In Fig 1, a driving plate 2 is connected to a driving shaft of an engine crankshaft 1, and the driving plate 2 and the driving shaft 1 rotate together. The driving plate 2 comprises an outer body 2a shaped like a ring, an inner body 2b shaped like a ring, and steel side plates 2c and 2d which clamp the outer body 2a from both sides by a rivet 3. The inner body 2b is fixed to the side plate 2c by a screw 4. On the periphery of the body 2a is press-fitted or shrink-fitted a ring gear 5 for accommodating the starting of an engine. The side plate 2d which constitutes one part of the driving plate 2 and which is located close to a flywheel 6 has its periphery bent in the L-letter fashion to surround the flywheel 6. The bent portion 2d' covers a gap 11 extending straight in the radial direction between the driving plate 2 and the flywheel 6. Parallel to the driving plate 2 and coaxial with the driving plate 2, the flywheel 6 is installed rotatably with respect to the driving plate 2 and it is supported rotatably by the driving plate 2 by means of a bearing 7. A clutch-positioning pin 8 is provided for positioning a clutch not shown and a screw hole 9 is formed for fitting the clutch cover not shown. The flywheel 6 is divided into a flywheel body 6a and a driven plate 6b so that it can house a torque limiting mechanism 15 which will be described later. The flywheel body 6a and the driven plate 6b are connected together by means of a bolt 10. A bolt hole 23 into which the bolt 10 goes extends through the driven plate 6b, extends to the plane where a hysteresis mechanism 18 slides against the driven plate 6b, and opens to the part where the hysteresis mechanism 18 is located. The part of the bolt hole 23 extending to the sliding plane may be female screwed or may be not female screwed. A spring mechanism 12 (vibration supression mechanism by a spring) is provided between the driving plate 2 and the flywheel 6. The spring mechanism 12 comprises a plurality of coil springs 13 extending in the circumferential direction and spring seats 14 provided at both ends of each of the coil springs 13. The spring seats 14 have portions 14e which are deformable with a greater spring constant than the spring 13. The spring seats 14 at both ends of the coil spring 13 are identical in shape, but one of the spring seats 14 provided at both ends of each spring 13 is opposed to an end wall of a prolonged opening formed in the side plate 2c and a radially inward projection of the side plate 2d of the driving plate 2 so as to contact the driving plate 2, while another of the spring seats 14 is opposed to a radially outward projection 16b of a driven disk 16 of the torque limiting mechanism 15 which will be described later so as to contact the driven disk 16. Figure 4 is a detailed view of the spring seat 14. As seen from Fig. 4, the part of the spring seat 14 which is located approximately at the coil diameter of the spring 13 and contacts the driving plate 2, has a projection 14a formed so as to project against the driving plate 2, while the part of the spring seat 14 which contacts a circumferentially projecting projection 16c of the outwardly projecting projection 16b of the driven disk 16 and is located inside of the coil diameter of the coil spring 13, has a recess 14b formed to engage the projection 16c. The center R₂ of the semi-circular section of the recess 14b of the spring seat 14 at one end of the coil spring 13 is located nearer to the spring seat 14 at the other end of the coil spring 13 than the center R₁ of the semi-circular section of the projection 14a of the spring seat 14 at said one end of the coil Spring 13 as shown in Fig. 2. Between the projection 14a and the recess 14b there is formed a rib 14c, which constitutes a side wall of the recess 14b. On the opposite side of the recess 14b a projection 14d is formed on the spring seat 14. The projection 14d looks approximately like a short column and attached with a deformable portion 14e. A pair of spring seats 14 are arranged at both ends of the spring 13, with their projections 14d facing each other, serving as the seat of the spring 13. When no torque is acting, there is a gap between at least one of the spring seats 14 and at least one of the members 2c and 2d and 16b which the seat 14 is able to contact, thereby producing a torque-free characteristic A of Fig. 3. The characteristic A, however, has hysteresis on account of a hysteresis mechanism 18 which will be described later. The characteristic B in Fig. 3 is produced on account of a deformation of the spring 13 and the characteristic C is produced on account of a deformation of the deformable portion 14e of the spring seat 14 when the spring 13 is compressed to make the two spring seats 14 contact each other. Next, the action of the above-mentioned device of the present invention will be described referring to Figs. 3 and 4. The rotating torque of the engine crankshaft 1 is transmitted to the driving plate 2 which rotates together with the crankshaft 1, and then to the flywheel 6 via the spring mechanism 12, the torque limiting mechanism 15 and the hysteresis mechanism 18. Thereby a small variation of the torque of the crankshaft 1 and the engine vibration can be absorbed by a vibration system which comprises the spring mechanism 12, the torque limiting mechanism 15, the hystersis mechanism 18 and the inertia members, i. e., the driving plate 2 and the flywheel 6. As illustrated by the characteristics A, B, C, and D of Fig. 3, for the purpose of effectively absorbing the vibrations in an idling state of an engine, a soft spring characteristic is required when the relative rotational displacement between the driving plate 2 and the flywheel 6 is small and a hard spring characteristic is required for the purpose of making the spring mechanism 13 compact when the relative rotational displacement is large. Further, when a torque larger than required acts, it is necessary for the purpose of protecting the power train to limit the torque and transmit it to the clutch. For these purposes, when the torque is small, the gap between the spring seat 14 and the driven disk 16 and the low frictional force of the hysteresis mechanism 18 effectively act to produce the characteristic A. Next, when the spring seat 14 and the driven disk 16 come into contact, the spring 13 deforms under an increased torque, producing the characteristic B. When with a further increase of the torque the spring 13 deforms more largely to cause two spring seats 14 to contact each other, the deformable portions 14e of the spring seats 14 themselves deform under the increased torque, producing the characteristic C. When the torque increases and exceeds a specified torque, a slip develops between the torque limiting mechanism 15 and the flywheel 6, thereby releasing an excess of the torque and producing the characteristic D. In this way, the torque can be transmitted to the power train with its variations effectively absorbed. For the sake of the characteristic stability as described above, it is not desirable that the spring seat 14 of the spring mechanism 12 gets heavily worn and the performance of the spring mechanism 12 deteriorates. According to the present invention, the part, which contacts the driven disk 16, of the spring seat 14, i.e., the part subject to a particularly heavy wear, is designed to form an approximately elliptical recess 14b with an increased area of contact with the projection 16c of the driven disk, with the result that the plane pressure due to a centrifugal force of rotation is reduced and accordingly the wear can be reduced. And this is done without increasing the axial dimension or decreasing the strength of the driven disk. Meanwhile, a closer location of the center R₂ of the recess 14b than the center R₁ of the projection 14a to the opposite spring seat allows the coil spring 13 to be made longer, allows a play against the driven disk 16 to be made larger, and as a consequence allows the relative angular displacement between the driving side and the driven side to be made larger, thereby reducing the natural frequency of resonance of the device and enhancing the effect of vibration absorption. Meanwhile, a rib 14c provided on both sides of the recess 14b inhibits axial displacement and therefore the driven disk 16 is not likely to be axially dislocated against the spring seat 14. The rib 14c concurrently serves to reinforce the spring seat 14. The benefits originating from provision of a recess on the driving side of the spring seat and provision of a projection on the driven side include mitigation of wear of the spring seat on account of an increased area of contact, an increased effect of vibration absorption on account of an increase in the length and play of the spring, prevention of dislocation of spring seat from driven plate, and maintenance of spring seat strength when a rib is formed between the projection and the recess of the spring seat.

Claims: A torque variation absorbing device having a driving plate (2) coupled to a driving shaft (1), a flywheel (6) arranged coaxially with said driving plate (2) and rotatably supported via a bearing (7) on said driving plate (2), said flywheel (6) being divided into a flywheel body (6a) and a driven plate (6b), and a spring mechanism (12), a torque limiting mechanism (15) and a hysteresis mechanism (18) interposed between said driving plate (2) and said flywheel (6), said spring mechanism (12) comprising a coil spring (13) and spring seats (14) disposed at both ends of said coil spring (13), and said torque limiting mechanism (15) comprising driven disks (16), wherein each of said spring seats (14) has a convex projection (14a) formed thereon to engage with said driving plate (2), characterized in that each of said spring seat (14) has a concave recess (14b) located in the central portion of said spring seat (14) and formed therein to engage with said driven disks (16). A torque variation absorbing device according to claim 1, characterized in that the center (R₂) of said concave recess (14b) is located closer to said spring seat (14) on the other end of said coil spring (13) than the center (R₁) of said convex projection (14a). A torque variation absorbing device according to claim 1 or 2, characterized in that a rib (14c) is formed in said spring seat (14) between said convex projection (14a) and said concave recess (14b). A torque variation absorbing device according to claim 1 to 3, characterized in that said convex projection (14a) is formed on the part of said spring seat (14) which contacts the outer coil of said coil spring (13) and said concave recess (14b) is formed inside a projection (14d) of said spring seat (14) extending axially within the coil region of said coil spring (13).

Inventors: KAMIYA, MASAKAZU, KATO, SATOSHI, KOBAYASHI, KIYONORI
Applicants: AISIN SEIKI KABUSHIKI KAISHA, TOYOTA JIDOSHA KABUSHIKI KAISHA
Application year: 1985
Main classification: F16F15
IPC codes: F16F15, F16D47