Lock-Up Torque Converter With Damper

The present invention relates to a lock-up torque converter and more particularly to a compact arrangement of a damper which provides a driving connection between a lock-up clutch piston and a turbine runner.

A vehicle installed with a torque converter will show a poor fuel economy because of the fact that any fluid coupling experiences some degree of slip. A various kinds of lock-up torque converters have been proposed in which a torque converter locks up by means of a built-in clutch in a predetermined (high speed) operating range of a vehicle when torque variation of an engine is not experienced as a problem.

In a known lock-up torque converter, a damper for providing a driving connection between a clutch piston and a turbine runner is located in a space available between an outer periphery of the clutch piston and an outer periphery of the turbine runner and it is drivably connected at an inlet element thereof to the clutch piston and at an outlet element thereof to the turbine runner.

A problem with this damper arrangement is that since the damper is spaced radially outwardly from the axis of rotation about which the clutch piston and the turbine runner rotate by a considerable amount, the damper is thrown outwardly with such a large centrifugal force as to induce malfunction of the damper when the vehicle operates at high speeds.

In another known lock-up torque converter, a damper is located between an inner periphery of a clutch piston and an inner periphery of a turbine runner.

A problem with this known arrangement is that since the damper is spaced radially outwardly from the rotation axis by a relatively small amount as compared to the damper arrangement mentioned before, a large damper has to be provided so as to afford to carry or transmit a large amount of torque and it requires complicated construction to drivably connect the damper to the turbine runner, as a result of which the entire axial length of this known arrangement becomes long.

It is therefore an object of the invention to provide a simple and space saving construction for drivably connecting a damper to a turbine runner.

In the accompanying drawings:

FIG. 1 is a longitudinal sectional view of a lockup torque converter according to the present invention;

FIG. 2 is a cross sectional view of a clutch piston and an annular mounting member secured thereto;

FIG. 3 is a top plan view, only half shown, of the clutch piston as viewed from the right hand side of FIG. 2;

FIG. 4 is a sectional view taken through line A--A of FIG. 5; and

FIG. 5 is a top plan view, partly broken away, of a damper used in FIG. 1.

Referring to FIG. 1, the reference numeral 1 designates a converter housing and the reference numeral 2 a crankshaft. A boss 3 and a drive plate 4 are concentrically secured to the end of the crankshaft 2, such as, by means of a plurality of fasteners 5. Drive plate 4 carries at its outer periphery of a ring gear 6. Drive plate 4 is drivably connected to a converter cover 9 concentrically by means of a plurality of fasteners 8 using the corresponding number of spacers 7. A sleeve 10 is secured to the central portion of the converter cover 9. Sleeve 10 is received in boss member 3 and thus the converter cover 9 is centered with respect to crankshaft 2. Converter cover 9 has a cylindrical shape having a closed end wall adjacent the drive plate 4 and an open end. To the outer periphery of the converter cover 9 adjacent the axial end defining the open end thereof, a pump impeller 11 is secured by welding so as to be coupled with the converter cover 9. A turbine runner 12 is secured to a hub 13 at a flange thereof by rivetting. A stator 14 is situated between the pump impeller 11 and the turbine runner 12 to form a torque converter. Stator 14 is mounted to a hollow stationary sleeve 16 through a one-way clutch 15.

The stationary sleeve 16 permits an output shaft 17, which may be a transmission input shaft, to extend therethrough with an annular space or play between them. Between the stationary sleeve 16 and the output shaft 17 three spacers (bushings) 18, 19 and 20 are disposed axially spaced one after another to divide the annular space into two annular chambers 21 and 22. The hub 13 for the turbine runner 12 is splined to the output shaft 17. Between the closed end wall of the converter cover 9 and its adjacent axial end of the hub 13, an annular member of spacer 23 is disposed to define a chamber 24. This chamber 24 communicates with the annular chamber 22 through an axial opening 25 formed in the output shaft 17 and through a radial opening 25a.

A generally annular clutch piston 26 is slidably mounted on the hub 13 on an annular portion thereof. An annular clutch facing 27 is attached to the adjacent surface of the clutch piston 26 to the converter cover 9. When the clutch facing 27 of the clutch piston 26 engages with the adjacent surface of the end wall of the converter cover 9 upon engagement of the clutch, a chamber 28 is formed between the converter cover 9 and the clutch piston 26. This chamber 28 communicates with the chamber 24 through radial grooves 29 formed at one axial end of the hub 13. Secured to the remote end wall of the clutch piston 26 is an annular mounting member 30. Within a limited space available between the inner periphery of the turbine runner 12 and the inner periphery of the clutch piston 26 a damper 31 is operatively connected between the clutch piston 26 and the hub 13 to provide a driving connection.

Referring to FIGS. 2 and 3, the construction of the clutch piston 26 and that of the annular mounting member 30 will be described hereinafter. The clutch piston 26 is die formed from a piece of plate metal and includes a inner axially extending flange 26a and an outer axially extending, in the same direction, flange 26b. The clutch piston 26 is slidably mounted by the inner axially extending flange 26a on the hub 13. The outer axially extending flange 26b is formed for reinforcement purpose of the annular portion of the clutch piston 26 which will be subjected to difference, in pressure, upon engagement of the lock-up clutch. The annular mounting member 30 has a plurality of inner axially extending circumferentially spaced mounting legs 30a.

Referring to the ratio (1/t, see FIG. 2) of length (l) of the outer axially extending flange 26b to thickness (t) thereof, it is preferable that this ratio is from 2 to 8 for reducing the amount of bending of the clutch piston 26 under the influence of difference in pressure on the opposite sides of the clutch piston 26.

Preferably, the clutch piston 26 is axially offset to provide a generally cylindrical shoulder portion 26d (see FIGS. 1 and 2) for reinforcement purpose. It is preferable that the ratio of length of this shoulder portion 26d to thickness thereof is from 2 to 8.

The damper 31 includes a sleeve 32 and a flange 32a radially extending from the sleeve 32. It also includes a plate assembly including a pair of plates 33 and 34 disposed on opposite sides of the flange 32a and spaced therefrom. The flange 32a and plates 33 and 34 have a plurality of openings 32b, 33a and 34a (see FIGS. 1 and 4) and a spring 35 is disposed in each set of these openings. The flange 32a has a plurality of second openings 32c (see FIGS. 1 and 4). A plurality of torque transmitting fasteners in the form of rivets 36 provide a driving connection between the plates 33 and 34. One of these rivets 36 extends through each of the second openings 32c of the flange 32a to act as a limit stop between the flange 32a and the plates 33 and 34.

The sleeve 32 and the plates 33 and 34 have openings receiving the inner axially extending flange 26a of the clutch piston 26, as best seen in FIG. 1. It will be noted that the damper 31 is arranged concentrically with and above the inner axially extending flange 26a of the clutch piston 26.

The damper 31 includes the annular mounting member 30 secured to the clutch piston 26. The flange 32a of the damper 31 has a plurality of circumferentially spaced outwardly opening notches 32d, one receiving each of the mounting legs 30a of the annular mounting member 30 (see FIGS. 1 and 4). If desired, some or all of the notches 32d may open to the second openings 32c, as shown in FIG. 4.

The plate 34 has an annular mounting portion extending radially outwardly and formed with a plurality of holes 34b as shown in FIGS. 4 and 5. This annular mounting portion is contoured to conform with the shape of that portion of the outer shell 12a to which the mounting portion is secured by welding, as shown in FIG. 1. The holes 34b are formed for receiving welding material upon securing the annular mounting portion to the outer shell 12a by welding.

The remote open end of the converter housing 1 from the crankshaft 2 is secured to a pump housing 38 which in turn is secured to a pump cover 39 secured to a transmission case 40 by means of fasteners 37. The pump cover 39 extends radially from the stationary sleeve 16. Within the pump housing 38, oil pump elements including an outer gear 41 and an inner gear 42 are operatively disposed. A pump driving sleeve 43 extends into the pump housing 38 and journalled thereby by means of a bushing 44. The pump driving sleeve 43 permits the stationary sleeve 16 to extend therethrough, and has one axial end drivingly connected to the pump impeller 11 and has an opposite end splined to the inner gear pump element 42. Since the pump driving sleeve 43 is spaced from the stationary sleeve 16, an annular oil passage 45 is formed between them. This passage 45 at its one end communicates with the inside of the torque converter assembly and at an opposite end thereof communicates with a source of torque converter operating oil via a suitable passage structure formed in the pump cover 39.

The inside of the turbine runner 12 communicates with the annular chamber 21 by a radial passage 46 formed through the stationary sleeve 16. This annular chamber 21 communicates with a pressure maintaining valve 47 which in turn communicates with an oil cooler 48 communicating in turn with an oil reservoir 50 via various parts 49 which require lubrication. The annular chamber 22 communicates with a lock-up control valve 52 through an oil passage 51 (where the reference numerals 51a and 51b designate fit-in balls). The lock-up control valve 52 has the function to selectively connect the oil passage 51 to the source of torque converter operating oil or the oil reservoir 50.

The torque converter constructed thus far will operate as follows:

The rotation of the crankshaft 2 is always delivered to the pump impeller 11 through the drive plate 4, the fasteners 8 and the converter cover 9. The rotation of the pump impeller 11 is delivered through the pump driving sleeve 43 to the pump element inner gear 42. Thus the oil pump operates as long as the engine operates.

When the vehicle operating condition does not satisfy a predetermined condition in which lock-up clutch engagement is required, the lock-up control valve 52 permits the oil passage 51 to communicate with the discharge side of the source of torque converter operating oil. Meanwhile oil is supplied from the source of torque converter operating oil to the inside of the pump impeller 11. The source of torque converter operating oil includes the oil pump 41, 42 and the pressure regulator valve, not shown. The oil in the inside of the torque converter assembly flows out of the turbine runner 12. The oil discharged from the turbine runner 12 flows through the radial passage 46 and the annular chamber 21 to the pressure maintaining valve 47 thus the pressure within the torque converter assembly being maintained at a certain level determined by the pressure maintaining valve 47. This pressure, i.e., the pressure within the torque converter assembly, is transmitted through the lock-up control valve 52, the passages 51 and 25, the chamber 24 and radial passage 29 to the clutch chamber 28. Thus, the clutch piston 26 is held disengaged from the converter cover 9 when the chamber 24 is pressurized.

Under this condition, the torque converter will perform its torque multifying function because the oil maintained at the certain pressure will transmit the torque under the reaction of the stator 14 from the pump impeller 11 to the turbine runner 12. The rotation of the turbine runner 12 is transmitted to the output shaft 17 so that the engine power may be delivered to the gear train of the associated transmission.

The oil after flowing through the pressure maintaining valve 47 will flow to the oil cooler 48 installed within the lower tank of the radiator. After being cooled by the oil cooler 48, the oil will be distributed to the various parts or portions to be lubricated in the transmission and thereafter flow back to the oil reservoir 50, i.e., the oil pan of the transmission. The oil pump including the gears 41 and 42 will draw oil from this oil reservoir 50.

When the vehicle operating condition satisfies the predetermined condition, for example when the vehicles operates at speeds above a predetermined speed in the highest gear, the lock-up control valve 52 will change over the cause the oil passage 51 to connect with the drain passage 67 that leads to the oil reservoir 50. This connection will cause the oil within the clutch chamber 28 to be exhausted through the radial passage 29, the chamber 24, the oil passage 25, the oil passage 51 and through the lock-up control valve 52 so that the clutch piston 26 will be urged toward the left (viewing in FIG. 1) to engage with the converter cover 9 under the influence of the difference in pressure crated between the both sides of the clutch piston 26. When the clutch facing 27 attached to the clutch piston 26 firmly engages with the converter cover 9, the piston 26 will be directly connected to the converter cover 9 which in turn is connected to the crankshaft 2 and the pump impeller 11 to rotate with them as a unit. The rotation of the clutch piston 26 is transmitted to the turbine runner 12 mechanically through the annular mounting member 30, the legs 30a, flange 32a, the springs 35 and the plates 33 and 34. The impact upon initiation of the transmission of the rotational torque will be absorbed by the springs 35. Thus, the damper 31 will transmit the torque while suppressing the impact which otherwise would take place upon change in magnitude of the torque transmitted therethrough. In this manner, the turbine runner 12 is directly connected to the crankshaft 2 and the pump impeller 11 through the damper 31, the clutch piston 26 and the converter cover 9.

Since the damper 31 is operatively disposed within a limited space available adjacent the inner periphery of the clutch piston 26, the problem that a damper will not perform its designated function under the influence of the centrifugal force under high speed engine speeds will be avoided.

Since the damper 31 is secured, by welding, to the outer shell 12a of the turbine runner 12, a driving connection between the damper 31 and the turbine runner 12 has been greatly simplified.