Torque transmission apparatus

A torque transmission apparatus including a first rotor, a second rotor, an elastic body deployed in a torque transmission path between the first rotor and the second rotor to absorb torque fluctuation between the first and second rotors, and a pair of seat members. The pair of seat members include holding portions for holding ends of the elastic body at one end surfaces and contact surfaces at the other end surfaces, and the contact surfaces are formed into convex curved surfaces so as to rollably contact concave curved lateral end surfaces of a housing of the first rotor and concave curved lateral end surfaces of projecting portions of the second rotor.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2015-252260 filed on Dec. 24, 2015, the content of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

This invention relates to a torque transmission apparatus having a function of absorbing torque fluctuation.

Description of the Related Art

Apparatuses are known that comprise a first rotor connected to a power source and a second rotor connected to the first rotor through an elastic body, wherein torque of the first rotor is transmitted to the second rotor through the elastic body and the elastic body absorbs torque fluctuation.

In an apparatus described in Japanese Laid-open Patent Publication No. 2015-86965 (JP2015-086965A), for example, the first rotor is connected to an engine and the second rotor is connected to a transmission through a clutch. Multiple springs are circumferentially disposed in housings formed inside the first rotor, seat members (spring seats) are deployed at opposite ends of every spring, and a part of the second rotor are further disposed between adjacent seat members. Therefore, torque of the first rotor is transmitted to the second rotor through the springs and seat members.

However, in the apparatus described in JP2015-086965A, since the seat members are deployed facing an outer circumferential surface of the housing, when large centrifugal force acts on the seat members, the seat members are apt to stick on the outer circumferential surface of the housing of the first rotor. As a result, the spring cannot provide appropriate elastic force between the first and second rotors, and thus vibration absorption performance of the apparatus declines.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, a torque transmission apparatus includes: a first rotor rotatable around a axial line; a second rotor rotatable relative to the first rotor around the axial line, facing the first rotor; an elastic body provided in a torque transmission path between the first rotor and the second rotor to transmit torque from one of the first rotor and the second rotor to the other of the first rotor and the second rotor and to absorb torque fluctuation between the first rotor and the second rotor; and seat members including holding portions configured to hold ends of the spring; wherein the first rotor includes a housing configured to accommodate the seat members in a circumferentially movable manner, the housing including an outer circumferential surface and lateral end surfaces, the lateral end surfaces being formed into concave curved surfaces so as to restrict the seat members from moving radially and circumferentially, the second rotor includes projecting portions formed so as to radially project, each of the projecting portions including lateral end surfaces, the lateral end surfaces being formed into concave curved surfaces so as to restrict the seat members from moving radially and circumferentially, the seat members include a pair of seat members deployed at opposite circumferential ends of the housing, each of the pair of seat members being interposed between the elastic body and both a lateral end surface of the lateral end surfaces of the housing and a lateral end surface of the lateral end surfaces of the projecting portion in the torque transmission path so as to be contactable with and separable from the lateral end surface of the housing and the lateral end surface of the projecting portion, and each of the pair of seat members includes the holding portion at one circumferential end surface thereof and a contact surface at the other circumferential end surface thereof, the contact surface being formed into a convex curved surface so as to rollably contact the lateral end surface of the housing and the lateral end surface of the projecting portion.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of the present invention is explained in the following with reference toFIGS. 1 to 6.FIG. 1is a diagram schematically illustrating an application example of a torque transmission apparatus100according to an embodiment of the present invention. The torque transmission apparatus100is interposed in a power transmission path between an engine101and a transmission102mounted on a vehicle via or not via a clutch (not shown).

The torque transmission apparatus100has a first rotor1and second rotor2both installed to be rotatable around an axially extending center line (axial line) CL0, and springs3installed in a torque transmission path TP between the first rotor1and the second rotor2. The first rotor1is connected to an output shaft (crankshaft)101aof the engine101, and the second rotor2is connected to an input shaft102aof the transmission102. Torque input to the first rotor1from the engine101is transmitted to the second rotor2through the springs3. At this time, torque fluctuation between the first rotor1and the second rotor2is absorbed by expansion or contraction of the springs3. As a result, transmission to the transmission102of vibration owing to rotational fluctuation of the engine101can be damped.

FIG. 2is a cross-sectional diagram (cross-sectional diagram taken along axial line CL0) illustrating a main part configuration of the torque transmission apparatus according to the embodiment of the present invention, andFIG. 3is a cross-sectional diagram taken along line ofFIG. 2(diagram of cross-section taken orthogonal to axial line CL0). As viewed inFIG. 3,FIG. 2corresponds to a sectional configuration taken along line II-II in the drawing. For convenience of explanation, a direction along the axial line CL0as shown inFIG. 2is defined as a forward-rearward direction, a direction radiating from the axial line CL0is defined as a radial direction, and a direction along a circle centered on the axial line CL0is defined as a circumferential direction. The structural components are explained in line with these definitions in the following.

As shown inFIG. 2, the first rotor1integrally includes a front plate11and a rear plate12, both of ring-like shape centered on the axial line CL0. Although not illustrated, the first rotor (for example, the front face of the front plate11) is provided with a torque input portion to which torque from the engine101is input.

The rear plate12includes a radially extending side plate part121and a circular annular part122bent forward from an outer radial edge of the side plate part121to extend axially. The front plate11includes a radially extending side plate part111. A front edge region of the circular annular part122of the rear plate12is joined to the outer radial edge of the front plate11by welding or fastened thereto by bolts. At this time, a ring-like space SP1whose outer circumferential side is covered by the circular annular part122is formed between the side plate part111of the front plate11and the side plate part121of the rear plate12.

FIG. 4is a plan diagram of the rear plate12(viewed from front). Some of the seat members4discussed later are included inFIG. 4. In addition, part of the second rotor2, discussed later, is indicated by a dotted line. As shown inFIG. 4, identically shaped depressions123are formed in a front face of the side plate part121at three equally spaced intervals. Each depression123has an arcuate outer circumferential surface51centered on the axial line CL0, an arcuate inner circumferential surface52facing the outer peripheral surface51, and a pair of lateral end surfaces53and54connecting the outer circumferential surface51and the inner circumferential surface52.

As shown inFIG. 2, the outer circumferential surface51is constituted by an inner circumferential surface122aof the circular annular part122. The depressions123are formed, for example, by swelling the side plate part121rearward using press-working. As shown inFIG. 4, border regions124where the depressions123are absent are provided between circumferentially adjacent pairs of the depressions123,123. As seen inFIG. 2, the border regions124have the sectional shape of the side plate part121before formation of the depressions123.

As indicated inFIG. 4, the outer circumferential surface51and the inner circumferential surfaces52are formed in the shape of concavely curved surfaces. In each depression123, a straight line CLa connecting a circumferential center point51aof the outer circumferential surface51and a circumferential center point52aof the inner circumferential surface52is defined as a center line of the depression123. The center line CLa intersects the axial line CL0, and the depression123exhibits symmetry with respect to the center line CLa. The paired lateral end surfaces53and54have respective concave curved surface portions531and541connected to the inner circumferential surface52and respective connecting surfaces532and542connecting the curved surface portions531,541and the outer circumferential surface51. The curved surface portions531and541are formed in the shape of arcs having a predetermined radius of curvature R. The connecting surfaces532and542are configured as flat surfaces or curved surfaces (for example, composite surfaces) which intersect the outer circumferential surface51at a predetermined angle. InFIG. 4, the connecting surfaces532and542are configured as convexly curved surfaces. Points P10and P20inFIG. 4are arc centers.

When lines TL1and TL2are drawn from the axial line CL0tangentially to the curved surface portions531and541respectively, intersection points P12and P22between the curved surface portions531and541and the connecting surfaces532and542are located inside the pair of tangent lines TL1and TL2. Therefore, parts of the border regions124, i.e., portions radially outward of intersection points (tangent points P11and P21) between the curved surface portions531and541and the tangent lines TL1and TL2, project more circumferentially inward than the pair of tangent lines TL1and TL2. Hereinafter, these are designated projections124aand124b.

The projection amount of the projections124aand124bfrom the tangent lines TL1and TL2can be defined as a function of angles α between line segments connecting the center points P10, P20and tangent points P11, P21and line segments connecting the center points P10, P20and intersection points P12, P22. As explained further later, the projections124aand124bwork to control radially outward movement of the seat members4. In the present embodiment, the angles α are set greater than at least 0° in order to provide the projections124aand124bin the border regions124.

Although not shown in a plan view in the drawings, the front plate11, similarly to the rear plate12, is formed at three locations with identically shaped depressions113(FIG. 2), and border regions114(FIG. 2) are formed between adjacent pairs of the depressions113,113. Specifically, in the rear face of the front plate11, forwardly bulged depressions113are formed opposite the depressions123of the rear plate12and border regions114are formed opposite the border regions124.

Similarly to the depressions123of the rear plate12, each depression113is also delineated by the outer circumferential surface51, the inner circumferential surface52and the paired inner circumferential surfaces52and54, and has the same shape as the depression123. The front plate11and rear plate12are joined with their circumferential phases adjusted to position the outer circumferential surface51, inner circumferential surfaces52and lateral end surfaces53,54of the rear plate12on axial extensions of the outer circumferential surface51, inner circumferential surfaces52and lateral end surfaces53,54of the front plate11. Therefore, as shown inFIG. 2, housings50for accommodating the springs3and the seat members4are formed between bottom surfaces55, the outer circumferential surface51, inner circumferential surfaces52and lateral end surfaces53,54of the depressions113, and bottom surfaces55, the outer circumferential surface51, inner circumferential surface52and lateral end surfaces53,54of the depressions123. The housings50are local axial expansions of the space SP1.

As shownFIG. 2, the second rotor2has a ring-shaped inner plate21deployed in the space SP1between the front plate11and rear plate12of the first rotor1to be rotatable around the axial line CL0. The inner plate21has an annular shaft22extending reward from its inner radial edge. A flange11ais provided on an inner radial edge of the front plate11and a bearing6is interposed between this flange11aand an outer circumferential surface of the shaft22to support the second rotor2rotatably relative to the first rotor1through the bearing6. Although not illustrated, the second rotor2(for example, its annular shaft22) is provided with a torque output portion for outputting torque to the transmission102.

As shown inFIG. 3, the inner plate21has projections23which project radially outward from the shaft22at three locations equidistantly spaced circumferentially. The projections23have outer circumferential surfaces24of arcuate shape centered on the axial line CL0, and the outer circumferential surfaces24are located radially inward by a predetermined distance from the outer circumferential surfaces51of the housings50(depressions113and123). Opposite lateral end surfaces25and26of the projections23connecting the outer circumferential surfaces24and the shaft22exhibit the same shape as opposite lateral surfaces of the border regions114and124, i.e., as the lateral end surfaces53and54of the depressions113and123. Therefore, the lateral end surfaces25and26have curved surface portions251and261of the same shape as the curved surface portions531and541. Curved surface portions252and262of the same shape as the inner circumferential surfaces52of the housings50are provided between the curved surface portions251and261and the shaft22.

FIG. 3shows an initial state in which the first rotor1and second rotor2are in non-rotated condition and no torque acts on the first rotor1and second rotor2. In the initial state, the circumferential positions of the projections23of the second rotor2, i.e., the position of the lateral end surfaces25and26, coincide with the circumferential position of the border regions114and124of the first rotor1, i.e., the position of the lateral end surfaces53and54.

As shown inFIG. 3, multiple springs3(two springs inFIG. 3) are tandemly installed in the respective housings50between the front plate11and rear plate12of the first rotor1. The springs3are, for example, coil springs which extend along cylindrical surfaces and whose opposite longitudinally ends are held by the seat members (spring seats)4. The seat members4include first seat members41and second seat members42deployed at opposite circumferential ends of the housings50and intermediate seat members43deployed between the first seat members41and second seat members42. The seat members4are, for example, constituted of resin material of lower specific weight than metal.

Rotation direction of the first rotor1rotationally driven by the engine101is indicated by arrow R1inFIG. 3. The first seat members41are positioned in the housings50rearmost in the direction of rotation R1and the second seat members42are positioned frontmost in the direction of rotation R1. As shown inFIG. 2, opposite forward-rearward ends of the seat members4are disposed in the depressions113and123.

As shown inFIG. 3, holding portions411and421for holding the springs3are formed on one end surfaces of the first seat members41and the second seat members42, and contact surfaces412and422which contact the curved surface portions531and541of the housings50(depressions113and123) at forward-rearward ends are formed on other end surfaces thereof. At their forward-rearward middle portions, the contact surfaces412and422are contactable also with the curved surface portions251and261of the projections23of the second rotor2. Holding portions431for holding the springs3are formed on opposite circumferential end surfaces of the intermediate seat members43. The holding portions411,421and431are, for example, constituted as circular grooves complementary to the outer shape of the springs3.

The contact surfaces412of the first seat members41and the contact surfaces422of the second seat members42are arcuately formed. The radius of curvature of the contact surfaces412is the same as that of the curved surface portions531of the first rotor1and the curved surface portions251of the second rotor2, and the radius of curvature of the contact surfaces422is the same as that of the curved surface portions541of the first rotor1and the curved surface portions261of the second rotor2. Therefore, the first seat members41can roll (or slide) along the curved surface portions531and251, and second seat members42can roll (or slide) along the curved surface portions541and261. The intermediate seat members43are accommodated in the housings50to be movable circumferentially and radially.

FIG. 5is an enlarged view of a main part ofFIG. 3. As shown inFIG. 5, the first seat member41and the second seat member42are symmetrically shaped with respect to a center line CL3bisecting the intermediate seat member43and passing through the axial line CL0, and are positioned symmetrically relative to the center line CL3. The intermediate seat member43is symmetrically shaped with respect to the center line CL3. Seats411a,421aand431aof the springs3are formed on bottom surfaces of the holding portions411,421and431of the seat members4.

Each seat431aof the intermediate seat member43is formed to incline with respect to the center line CL3so that the center line CL3and an extension of the seat431aintersect on an outer circumferential surface432side of the intermediate seat member43at a predetermined angle β (>0). The angle is called “seat angle.” In the initial state in which the first rotor1and second rotor2are in non-rotated condition and no centrifugal force acts on the intermediate seat members43, elastic force of the springs3keeps the intermediate seat member43in an initial orientation in which the seats411a,421aand the seat431alie parallel.

In the initial state, an intersection point P30of center lines CL31and CL32of the coil-shaped pair of springs3is located more radially inward than a reference line L3connecting a center of the seat411aof the first seat member41and a center of the seat421aof the second seat member42by a straight line. Therefore, the intermediate seat member43side of each spring of the pair of springs3is inclined with respect to the reference line L3so as to slope radially inward. In other words, the center lines CL31and CL32of the springs3do not lie on the same straight line, but cross at a predetermined angle smaller than 180°.

The initial orientation of each intermediate seat member43is determined as a function of the seat angle β of the intermediate seat member43. Specifically, in proportion as the seat angle β is larger, the inclination angle of the springs3with respect to the reference line L3increases and the initial position of the intermediate seat member43shifts radially inward. In the present embodiment, the initial position of the intermediate seat member43is established so that the intersection point P30of the center lines CL31and CL32is located on the reference line L3when, for example, the intermediate seat member43moves radially outward due to centrifugal force during idle rotation of the engine101, and the seat angle β is established in line with this initial position. In other words, the seat angle β is established so that during idle rotation the center lines CL31and CL32of the springs3lie on the same straight line (reference line L3).

The members of each pair of springs3are formed so that mass per unit length, i.e., density, of each spring decreases from the associated first or second seat members41,42toward the intermediate seat members43. In other words, the springs3are made with irregular pitch along the center lines CL31and CL32. The convex outer circumferential surface432of the intermediate seat member43is formed arcuately to have smaller radius of curvature than the outer circumferential surface51of the housing50.

Operation of the torque transmission apparatus100configured as set forth in the foregoing will be explained. As shown inFIG. 4, angle θ formed between a first center line CL1extending radially from the axial line CL0and passing through a circumferential middle of the border regions114and124of the first rotor1and a second center line CL2extending radially from the axial line CL0and passing through a circumferential middle of the projections23of second rotor2(dotted line) (called torsion angle θ) represents amount of rotation of the second rotor2with respect to the first rotor1. In the initial state (FIG. 3), the first center line CL1and the second center line CL2coincide. Torsion angle θ is therefore 0°.

When the first rotor1has rotated in a predetermined direction (direction of arrow R1) to make amount of rotation of the first rotor1greater than amount of rotation of the second rotor2, torsion angle θ is positive. Conversely, when amount of rotation of the first rotor1is smaller than amount of rotation of the second rotor2in R1direction, torsion angle θ is negative.

During ordinary driving for example, as shown inFIG. 6, torque T of the first rotor1passes from the lateral end surfaces53of the housings50(border regions114,124) through the first seat members41, springs3, intermediate seat members43, springs3and second seat members42and acts on the lateral end surfaces26of the projections23of the second rotor2. In this case, the torsion angle θ is positive and the second rotor2can be rotated in the direction of arrow R1by torque of the first rotor1.

In contrast, although not illustrated, during engine braking or the like activated by a shift-down, for example, amount of rotation the second rotor2becomes greater than that of the first rotor1, so that torque of the second rotor2passes from the lateral end surfaces25of the projections23through the second seat members42, springs3, intermediate seat members43, springs3and first seat members41and acts on the lateral end surfaces54of the housings50of the first rotor1. In this case, the torsion angle θ is negative and the first rotor1is rotated in the direction of arrow R1by torque of the second rotor2.

Irrespective of whether the torsion angle θ is positive or negative, any torque fluctuation arising between the first rotor1and second rotor2can be absorbed by expansion and contraction of the springs3. As a result, transmission to the transmission102of vibration due to rotational fluctuation of the engine101(combustion oscillation or the like) can be mitigated.

Behavior of the springs3and the seat members4constituting characteristic operation of the torque transmission apparatus100according to the present embodiment will now be explained in detail. In the initial state when the first rotor1and second rotor2are in non-rotated condition, no centrifugal force acts on the seat members4. Therefore, as shown inFIG. 5, the intersection point P30of the center lines CL31, CL32of each pair of springs3is located radially inward of the associated reference line L3. In other words, the intermediate seat members43are located radially inward of the associated first and second seat members41,42.

When, for example, the engine101rotates at idle speed starting from this state, the first rotor1rotates in the direction of arrow R1inFIG. 3in response to this engine rotational speed. In addition, torque of the first rotor1is transmitted to the second rotor2through the seat members4and the springs3, whereby the second rotor2also rotates in the direction of arrow R1. Centrifugal force therefore acts on the seat members4in proportion to the rotational speed of the first and second rotors1,2.

At this time, although the intermediate seat members43move radially outward from their initial positions, radial movement of the first and second seat members41,42is restricted by the border regions114,124of the first rotor1and the projections23of the second rotor2. In this state, elastic force of the springs3acts on the first and second seat members41,42in proportion to radial movement of the intermediate seat members43. Owing to this elastic force, the first and second seat members41,42roll (or slide) along the lateral end surfaces53and54(curved surface portions531and541) of the border regions114,124and the lateral end surfaces25,26(curved surface portions251,261) of the projections23in the direction of arrows R2inFIG. 3.

Owing to the rolling of the first and second seat members41,42accompanying radial movement of the intermediate seat members43in this manner, inclination of the center lines CL31and CL32of each pair of springs3with respect to the associated reference line L3changes. Therefore, the springs3of each pair are not bent but extend linearly. As a result, each pair of springs3can constantly produce suitable elastic force irrespective of the radial location of the associated intermediate seat member43, thus enabling the torque transmission apparatus100to achieve good vibration absorption performance.

When the engine101is idling, the intersection point P30of the center lines CL31and CL32of each pair of springs3moves to the associated reference line L3, so that the center lines CL31and CL32come to lie on the reference line L3. During idle rotation, torque from the engine is low, so that the torsion angle θ of the second rotor2with respect to the first rotor1is small.

When torque acting on the second rotor2from the first rotor1rises from this condition owing to increase in engine speed caused by, for example, depression of an accelerator pedal, torsion angle θ widens as shown inFIG. 6. Moreover, centrifugal force on the intermediate seat members43increases, so that the intermediate seat members43, specifically the intersection points P30of the center lines CL31and CL32of the springs3, move radially outward of the reference lines L3.

When the engine speed increases, along with radially outward movement of the intermediate seat members43, the first seat members41roll along the curved surface portions531of the first rotor1and the second seat members42roll along the curved surface portions261of the second rotor2, in the directions of arrows R2inFIG. 6. On the other hand, when centrifugal force declines owing to decreasing engine speed, along with radially inward movement of the intermediate seat members43, the first seat members41roll along the curved surface portions531of the first rotor1and the second seat members42roll along the curved surface portions261of the second rotor2, in the directions of arrows R3inFIG. 6. As a result, the springs3of each pair are kept straight irrespective of radial movement of the intermediate seat members43, whereby they can constantly produce suitable elastic force.

In the present embodiment, the angle3of the intermediate seat members43is set so that intersection points P30of the center lines CL31, CL32of the pairs of springs3are located radially inward of the reference lines L3in the initial state of the engine stop and the intersection points P30are located on the reference line L3during idle rotation of the engine101(FIG. 5). By initially positioning the intermediate seat members43radially inward of the first and second seat members41,42in this manner, distance between the outer circumferential surfaces432of the intermediate seat members and the outer circumferential surfaces51of the housings50can be enlarged.

Moreover, in the present embodiment, the springs3have irregular pitch by which density of the springs3on the side of the intermediate seat members43is smaller than that on the sides of the first and second seat members41,42. Since mass near the middle of each pair of springs3(on the side of the associated intermediate seat member43) is therefore relatively small, centrifugal force proportional to the weight of the springs3can be reduced. As a result, radially outward movement of the intermediate seat members43can be suppressed.

Therefore, it is possible in each housing50to prevent contact between the outer circumferential surface432of the intermediate seat member43and the outer circumferential surface51of the housing50when the intermediate seat member43moves radially outward due to centrifugal force. As a result, sticking of the intermediate seat member43to the outer circumferential surface51can be prevented, and smooth expansion and contraction of the springs3is ensured.

The arcuate outer circumferential surface432of each intermediate seat member43has smaller radius of curvature than the outer circumferential surface51of the housing50. Therefore, even if the outer circumferential surface432should come in contact with the outer circumferential surface51, the area of contact would be small. This further ensures that the intermediate seat members43can slide smoothly without sticking to the outer circumferential surfaces51.

According to the present embodiment, the following operations and effects can be achieved.

(1) The torque transmission apparatus100includes a first rotor1rotatable around an axial line CL0, a second rotor2both installed to be rotatable around a common axial line CL0, springs3deployed in a torque transmission path TP between the first rotor1and the second rotor2to transmit torque from one of the first rotor1and second rotor2to the other of the first rotor1and second rotor2and absorb torque fluctuation between the first rotor1and the second rotor2, and seat members4(41to43) having holding portions411,421,431for holding ends of the springs3(FIG. 3). The first rotor1includes housings50which circumferentially movably accommodate the seat members4, and the housings50include outer circumferential surfaces51and lateral end surfaces53,54formed into concave curved surfaces so as to restrict the seat members4from moving radially and circumferentially (FIG. 4). The second rotor2includes radially projecting projections23, and the projections23include lateral end surfaces25,26formed into concave curved surfaces so as to restrict the seat members4from moving radially and circumferentially (FIG. 3). The seat members4include pairs of seat members41,42whose paired members are deployed at opposite circumferential ends of the housings50, and the paired seat members41,42are interposed between the springs3and both the lateral end surfaces53,54of the housings50and the lateral end surfaces25,26of the projections23in the torque transmission TP so as to be contactable with and separable from the lateral end surfaces53,54of the housings50and the lateral end surfaces25,26of the projections23(FIG. 3). The pairs of first and second seat members41,42respectively include the holding portions411,421at one circumferential end surfaces thereof and contact surfaces412,422at the other circumferential end surfaces, and the contact surfaces412,422are formed into convex curved surfaces so as to rollably contact the lateral end surfaces53,54of the housings50and the lateral end surfaces25,26of the projections23(FIG. 3).

This configuration ensures that while the pairs of seat members41,42roll along the lateral end surfaces53,54of the housings50and the lateral end surfaces25,26of the projections23, their circumferential and radial positions are concomitantly restrained by these lateral end surfaces53,54and lateral end surfaces25and26. Therefore, the pairs of seat members41,42can be prevented from sticking to the outer circumferential surface51of the housings50. Moreover, the rolling of the seat members41,42enables the springs3to stay straight without bending during attitude (inclination) change, so that the springs3can produce suitable elastic force for enabling the torque transmission apparatus100to exhibit good vibration absorption performance.

(2) The seat members4include intermediate seat members43interposed one between the seat members (first and second seat members41,42) of each pair, and springs3are interposed between each of the first and second seat members41,42and the associated intermediate seat member43(FIG. 3). This results in multiple springs3being tandemly deployed in the housings50interrupted by the interposed intermediate seat members43. Therefore, it becomes possible to utilize short, straight springs3in the torque transmission apparatus100. In this configuration, although the intermediate seat members43move radially under centrifugal force, their movement is accompanied by rolling of the first and second seat members41,42, so that the springs3always expand and contract linearly irrespective of the radial position of the associated intermediate seat member43. This enables the torque transmission apparatus100to achieve reliable vibration absorption performance by continuously maintaining optimum spring force.

(3) The paired springs3are deployed at inclinations so at to position the intersection points P30of the center lines CL31, CL32of the paired springs3radially inward of reference lines L3connecting centers of holding portions411,421of the first and second seat members41,42with each other (FIG. 5). In the initial state, therefore, each intermediate seat member43is located radially inward of the associated first and second seat members41,42, thereby expanding distance between the outer circumferential surface51of the associated housing50and an outer circumferential surface432of the intermediate seat member43. As a result, contact between the outer circumferential surface51of the housing50and the outer circumferential surface432of the intermediate seat member43can be avoided.

(4) Density per unit length of each spring of the paired springs3decreases from a side of the first or second seat member41,42toward a side of the associated intermediate seat member43(FIG. 5). Mass of the springs3therefore grows lighter from the first and second seat members41,42toward the intermediate seat members43. As a result, centrifugal force proportional to the weight of the springs3can be reduced on the side of the intermediate seat members43, thereby suppressing radially outward movement of the intermediate seat members43.

(5) The outer circumferential surfaces432of the intermediate seat members43have smaller radius of curvature than the outer circumferential surfaces51of the housings50. Therefore, even if centrifugal force should cause the intermediate seat members43to contact the outer circumferential surfaces51of the housings50, sticking of the intermediate seat members43can be prevented because the area of contact between the intermediate seat members43and the outer circumferential surfaces51is small. Moreover, smooth sliding of the intermediate seat members43along the outer circumferential surfaces51is ensured because contact is between convex curved surfaces (outer circumferential surfaces432) of the intermediate seat members43and concave surfaces (outer circumferential surfaces51).

Modifications

Various modifications of the embodiment described above are possible. Some of these are explained in the following. Although in the above embodiment the seat angle of the intermediate seat members43is set larger than 0° so that in the initial state the intersection points P30of the center lines CL31, CL32of the paired springs3are located radially inside the reference lines L3, the value of the seat angle is not limited to this. For example, the seat angle β can be set at 0°. In such case, the intersection points P30lie on the reference lines L3in the initial state. Although in the above embodiment the springs3are given irregular pitch, they can have regular pitch instead. In other words, springs3which have constant density over their full length are also usable.

Although in the above embodiment the first rotor1is provided with the housings50at three circumferentially spaced locations and the second rotor2is provided with the projections23at three circumferentially spaced locations, the number of housings50and projections23is not limited to this. For example, they can each be provided at two circumferential locations or at four or more circumferential locations. Although in the above embodiment paired springs3are tandemly deployed on both sides of a single intermediate seat member43, it is alternatively possible to tandemly deploy three or more springs3interrupted by multiple intermediate seat members43. Although in the above embodiment the outer circumferential surfaces432of the intermediate seat members43are arcuately formed, the outer circumferential surfaces432are not limited to this the shape.

Although in the above embodiment the lateral end surfaces53and54of the housings50and the lateral end surfaces25,26of the projections23are formed with the arcuately curved surface portions531,541,251,261, respectively, and the end surfaces of the first seat members41and second seat members42are formed with the arcuate contact surfaces412,422of the same shape as the curved surface portions531,541,251,261, the curved surface portions531,541,251,261and the contact surfaces412,422are not limited to this configuration. Specifically, the radius of curvature of the contact surfaces412,422need not be the same as the radius of curvature of the curved surface portions531,541,251,261insofar as the curved surface portions531,541,251,261are respectively constituted as concavely curved surfaces, the contact surfaces412,422are constituted as convexly curved surfaces, and the seat members41,42rollably contact the curved surface portions531,541,251,261.

In the above embodiment, although the first rotor1is connected to the engine101and the second rotor2is connected to the transmission102, a reverse arrangement having the first rotor1connected to the transmission102and the second rotor2to the engine101is also feasible. In the above embodiment, although the springs3(coil springs) are interposed between the first rotor1and the second rotor2and torque is transmitted through the springs3, the elastic body configuration can be of any type insofar as it is deployed in the torque transmission path TP between the first rotor1and the second rotor2and while transmitting torque from one to the other of the first rotor1and the second rotor2also absorbs torque fluctuation between the first rotor1and the second rotor2.

In the above embodiment, the torque transmission path TP between the first rotor1and the second rotor2is configured by the seat members4and the springs3. Specifically, a configuration is adopted wherein when torque from the first rotor1acts on the second rotor2, torque from the contact surfaces (torque transmission portions)422of the second seat members42acts on the curved surface portions261(torque receiving portions) of the projections23of the second rotor2, and when torque from the second rotor2acts on the first rotor1, torque from the curved surface portions251(torque transmission portions) of the projections23acts on the contact surfaces (torque receiving portions)412of the first seat members41. However, the torque transmission path TP is not limited to this configuration.

Although in the above embodiment the depressions113and123are provided in the front plate11and the rear plate12, respectively, of the first rotor1and the housings50are configured by the depressions113and123, the housings50can be of any configuration insofar as the outer circumferential surfaces51and the lateral end surfaces53and54restricting radial and circumferential movements of the seat members4are present. For example, the housings50can be configured solely by the front plate11. Although in the above embodiment projections are projected radially outward from an annular shaft portion22, projecting portions are projected radially inward from inner circumferential surface of a ring-shaped plate, for example, and the configuration of the second rotor is not limited to aforesaid configuration.

Although the holding portions411,421and431of the springs3which are one example of elastic bodies are provided in the seat members4in the above embodiment, the shape of the seat members4can be modified variously in accordance with the shape of the elastic bodies. Therefore, the configuration of the seat member4is not limited to that stated above. More specifically, the paired seat members41and42can be of any configuration insofar as paired seat members are provided so as to be contactable with and separable from the first and second rotors1and2between the springs3and the first and second rotors1,2and include holding portions at one end surfaces and contact surfaces at the other end surfaces.

Although in the above embodiment the engine101mounted on a vehicle is used as the power source, the power source is not limited to a vehicle engine. Further, the driven unit which is driven by the torque generated by the power source can be one other than the transmission102. In other words, the torque transmission apparatus of the present invention can be applied to various torque transmission paths for transmitting torque generated by a power source to a driven unit. The torque transmission apparatus of the present invention can be applied to other than vehicles.

The above embodiment can be combined as desired with one or more of the aforesaid modifications. The modifications can also be combined with one another.

According to the present invention, since the pairs of seat members deployed in the housing include the convexly curved contact surfaces which rollably contact the lateral end surfaces of the housing and the lateral end surfaces of the projecting portions, it is possible to prevent sticking of the seat members owing to centrifugal force and to produce suitable elastic force of the spring by the rolling of the seat members, whereby good vibration absorption performance can be achieved.