Speed Change Gear System

1. Field of the Invention

The present invention relates generally to speed change gear systems and more particularly to a speed change gear system which is adapted for application with fluid couplings utilized within motor vehicles, especially automobiles.

2. Description of the Prior Art

It is preferable to utilize at least four gear sets within the speed change gear systems of large automotive vehicles, such as for example, trucks and buses, and in order to attain a speed change mechanism having more than four speed shifts, three, four or even more sets of simple, single-pinion or double-pinion type planetary gear sets have heretofore been combined. While the combination of these gears may be widely varied, it is preferable however that the following conditions be attained:

(1) The output shaft should be coupled to the same elements within each speed range.

(2) In order to reduce the circumferential speed of the bearings of each element of the planetary gear set, the number of its revolutions should be small.

(3) The tooth load, that is, the tangential force of each element, should be small so as to maintain the strength of the gear teeth.

(4) The gear set should always attain meshing conditions for the number of teeth required. For example, the sun gear, whose diameter is to be minimized, as well as each planetary pinion gear, should have the necessary number of teeth.

(5) Within each planetary gear set, the coupling relationship among the elements should be simple and the distance from each other should be small.

(6) During speed shifts, wherein frictional coupling means are utilized during forward drive, such speed shifts should be available through one coupling means alone.

Accordingly, it is an object of the present invention to provide a speed change gear system which provides at least four speed ranges for forward drive and one speed range for reverse drive by the use of three planetary gear sets of the single-pinion type, three clutches, and two brakes, whereby the movable members of each of the planetary gear sets are suitably coupled as a result of the coupling or uncoupling of the clutches and brakes so as to attain the various speed ranges.

Various other objects, features and attendant advantages of the present invention will be more fully appreciated as the same becomes better understood from the following detailed description when considered in conjunction with the accompanying drawings, in which like reference characters designate like or corresponding parts throughout the several views, and wherein:

FIG. 1 is a schematic view of one embodiment of a speed change gear system constructed in accordance with the present invention and disclosing its cooperative parts;

FIG. 2 is a schematic view similar to that of FIG. 1 showing however another embodiment of the present invention;

FIG. 3 is a schematic view similar to that of FIG. 1 showing however yet another embodiment of the present invention;

FIG. 4 is a schematic view similar to that of FIG. 1 showing however still another embodiment of the present invention;

FIG. 5 is a schematic view similar to that of FIG. 1 showing yet still another embodiment of the present invention;

FIG. 6 is a schematic view similar to that of FIG. 1 showing however a further embodiment of the present invention;

FIG. 7 is a schematic view similar to that of FIG. 1 showing however a yet further embodiment of the present invention;

FIG. 8 is a schematic view similar to that of FIG. 1 showing however a still further embodiment of the present invention; and

FIG. 9 is a schematic view similar to that of FIG. 1 showing however a yet still further embodiment of the present invention.

Referring now to the drawings and more particularly to FIG. 1 thereof, the disclosed speed change gear system includes a first planetary gear set, generally indicated by the reference character X.sub.1, of the single-pinion type, a second planetary gear set, generally indicated by the reference character X.sub.2, of the single-pinion type, and a third planetary gear set, generally indicated by the reference character X.sub.3, also of the single-pinion type, all of which are interposed between an input shaft and an output shaft.

The first planetary gear set X.sub.1 is seen to comprise a first sun gear S.sub.1, a first planetary gear P.sub.1 engaged with the first sun gear S.sub.1, a first ring gear RG.sub.1 enmeshed with the first planetary gear P.sub.1, and a first carrier C.sub.1 rotatably supporting the first planetary gear P.sub.1, while the second planetary gear set X.sub.2 similarly includes a second sun gear S.sub.2, a second planetary gear P.sub.2 engaged with the second sun gear S.sub.2, a second ring gear RG.sub.2 enmeshed with the second planetary gear P.sub.2, and a second carrier C.sub.2 rotatably supporting the second planetary gear P.sub.2.

The third planetary gear set X.sub.3 includes a third sun gear S.sub.3, a third planetary gear P.sub.3 engaged with the third sun gear S.sub.3, a third ring gear RG.sub.3 enmeshed with the third planetary gear P.sub.3, and a third carrier C.sub.3 rotatably supporting the third planetary gear P.sub.3. It will be further seen that the first sun gear S.sub.1 is drivingly connected with the third sun gear S.sub.3, as is the first ring gear RG.sub.1 with the second ring gear RG.sub.2, the second sun gear S.sub.2 with the third ring gear RG.sub.3, and the second carrier C.sub.2 with the third carrier C.sub.3 as well as with the output shaft. A first clutch CL.sub.1 serves to couple or uncouple the first sun gear S.sub.1 and the third sun gear S.sub.3 with the input shaft, while a second clutch CL.sub.2 serves to couple or uncouple the first carrier C.sub.1 with the input shaft, and a third clutch CL.sub. 3 serves to couple or uncouple the first ring gear RG.sub.1 and the second ring gear RG.sub.2 with the input shaft.

A first brake B.sub.1 is provided so as to be capable of locking the first ring gear RG.sub.1 and the second ring gear RG.sub.2 to the gear casing when the first brake is actuated, and similarly, a second brake B.sub.2 is provided so as to be capable of locking the second sun gear S.sub.2 and the third ring gear RG.sub.3 to the casing when the same is actuated.

The following equations are given as characteristic of the planetary gear sets X.sub.1, X.sub.2 and X.sub.3 :

wherein:

N.sub.RG.sbsb.1,N.sub.RG.sbsb.2, N.sub.RG.sbsb.3 =the number of revolutions of the first, second and third ring gears;

N.sub.C.sbsb.1, N.sub.C.sbsb.2 , N.sub.C.sbsb.3 =the number of revolutions of the first, second

and third carriers;

N.sub.S.sbsb.1, N.sub.S.sbsb.2, N.sub.S.sbsb.3 =the number of revolutions of the first, second and third sun gears; and

I.sub.1, I.sub.2, I.sub.3 =the radial ratios of each ring gear with respect to each sun gear.

Within this embodiment, the radial ratios within each speed range are I.sub.1 = 0.452, I.sub.2 = 0.484, I.sub.3 = 0.355, and Table 1A shows the relationship between the operation of clutches CL.sub.1, CL.sub.2 and CL.sub.3 and brakes B.sub.1, and B.sub.2 relative to the gear ratio within each speed range, wherein F.sub.n (n = 1, 2, 3, . . .) designates a forward speed range, such as, for example, F.sub.1 designates the first forward speed range, F.sub.2 designates the second forward speed range, and the like, and R.sub.n (n = 1, 2, . . .) designates a reverse speed range, such as, for example, R.sub.1 designates the first reverse speed range, and it may be seen that a reduction gear ratio of 1 : 1.00 can be obtained by desirably and selectively employing two of the clutches CL.sub.1, CL.sub.2 and CL.sub.3. Table 1B shows the relationship regarding the number or revolutions and the tangential forces of each of the elements of the planetary gear sets within each speed range, the ratio of the number of revolutions being based upon the assumption that the number of revolutions of the input shaft is 1, while the designated tangential forces are based upon the assumption that the input shaft torque exerted upon the ring gear is 1, the tangential forces of the planetary gears being equal to those of the sun gears and the ring gears.

Within Table 1B, like reference characters designate identical or corresponding parts shown within Table 1A, and in addition, A designates a particular speed range, B designates an element of the planetary gear set, N designates the number of revolutions of the elements, and W designates the tangential force thereof. As the reduction gear ratio of the fourth forward speed range F.sub.4 is 1 : 1.00, the number of revolutions N of each sun gear, ring gear, and carrier is 1.00, the number of revolutions N of an individual sun gear, ring gear and carrier is 1.00, and the number of revolutions N of each planetary gear is 0.00.

The tangential forces W are therefore considerably less than those produced within the other speed ranges wherein the torque of the input shaft is transmitted to all of the elements through means of only one engaged clutch, while to the contrary, the torque of the input shaft of the fourth speed range F.sub.4 is distributed to all elements as a result of engaging at least two clutches, and accordingly, it is clear that the resulting tangential forces of the elements of such speed range are smaller than those produced as a result of the transmission of torque from the input shaft as a result of coupling only one clutch. Hereinafter, a discussion of the number of revolutions N and the tangential forces W within the speed range having the reduction gear ratio of 1 : 1.00 will be omitted.

Referring now to FIG. 2, there is shown another embodiment of the present invention wherein a fourth planetary gear set, generally indicated by the reference character X.sub.4, of the single-pinion type is interposed between the third planetary gear set X.sub.3 and the output shaft, such fourth planetary gear set X.sub.4 including a fourth sun gear S.sub.4 connected to the output shaft as well as to the third carrier C.sub.3, a fourth planetary gear P.sub.4 engaged with the fourth sun gear S.sub.4, a fourth ring gear RG.sub.4 enmeshed with the fourth planetary gear P.sub.4, and a fourth carrier C.sub.4 rotatably supporting the fourth planetary gear P.sub.4. The fourth ring gear RG.sub.4 is also drivingly coupled with the third ring gear RG.sub.3 and the second sun gear S.sub.2, and is additionally locked to the gear casing when the second brake B2 is actuated. A third brake B3 is also interposed between the fourth carrier C.sub.4 and the gear casing so as to be capable of locking the former to the latter when the brake is actuated.

The following formula is given as characteristic of the fourth planetary gear set X.sub.4 :

wherein:

N.sub.rg.sbsb.4 = the number of revolutions of the fourth ring gear;

N.sub.c.sbsb.4 = the number of revolutions of the fourth carrier;

N.sub.s.sbsb.4 = the number of revolutions of the fourth sun gear; and

I.sub.4 = the radial ratio of the fourth ring gear to the fourth sun gear.

Within this embodiment, the radial ratio within each speed range is I.sub.4 = 0.562, and Table 2A shows the relationship between the operation of all of the clutches CL.sub.1, CL.sub.2, and CL.sub.3 and brakes B.sub.1, B.sub.2 and B.sub.3 with respect to the reduction gear ratio within each speed range, while Table 2B shows the relationship regarding the number of revolutions and the tangential forces of the elements of the planetary gear sets within each speed range.

Referring now to FIG. 3, yet another embodiment of the present invention is disclosed wherein the fourth planetary gear set X.sub.4 of the single-pinion type includes a fourth sun gear S.sub.4 drivingly engaged with the third ring gear RG.sub.3, while the fourth ring gear RG.sub.4 is drivingly engaged with the output shaft. The fourth sun gear S.sub.4 is thus capable of being locked to the gear casing when the second brake B2 is actuated, and a third brake B3 is interposed between the fourth carrier C.sub.4 and the gear casing so as to be capable of locking the same thereto when the brake B3 is actuated.

Within this embodiment, the radial ratio within each speed range is I.sub.4 = 0.562 and Table 3A shows the relationship between the operation of the clutches and brakes with respect to the reduction gear ratios within each speed range, while Table 3B shows the relationship regarding the number of revolutions and the tangential forces of the elements of the planetary gear sets within each speed range.

A fourth embodiment of a speed change gear system constructed in accordance with the present invention is illustrated within FIG. 4 and is seen to include a fourth planetary gear set X.sub.4 of the single-pinion type interposed between the third planetary gear set X.sub.3 and the output shaft, the fourth carrier C.sub.4 being drivingly engaged with the third ring gear RG.sub.3 and the second sun gear S.sub.2 so as to be capable of being locked to the gear casing when the second brake B2 is actuated. The third brake B3 is interposed between the fourth sun gear S4 and the gear casing so as to be capable of locking the same thereto when the brake B3 is actuated, and the fourth ring gear RG.sub.4 is drivingly engaged with the third carrier C.sub.3 as well as the output shaft.

Within this embodiment, the radial ratio within each speed range is I.sub.4 = 0.562, and Table 4A shows the relationship between the operation of the clutches and brakes with respect to the reduction gear ratio within each speed range, while Table 4B shows the relationship regarding the number of revolutions and the tangential forces of all of the elements of the planetary gear sets within each speed range.

Referring now to FIG. 5, a further embodiment of the invention is disclosed wherein the fourth planetary gear set X.sub.4, of the single-pinion type is interposed between the third planetary gear set X.sub.3 and the output shaft and wherein further the fourth carrier C.sub.4 is drivingly engaged with the third ring gear RG.sub.3 and the second sun gear S.sub.2 so as to be capable of being locked to the gear casing when the second brake B2 is actuated. The third brake B3 is is interposed between the fourth ring gear RG.sub.4 and the gear casing so as to be capable of locking the same thereto when the brake B3 is in fact actuated, and the fourth sun gear S.sub.4 is drivingly engaged with the output shaft.

Within this embodiment, the radial ratio within each speed range is I.sub.4 = 0.562, and Table 5A shows the relationship between the operation of the clutches and brakes with respect to the reduction gear ratio within each speed range, while Table 5B shows the relationship regarding the number of revolutions and the tangential forces of the elements within the planetary gear sets within each speed range.

Turning now to the embodiment illustrated within FIG. 6, the fourth planetary gear set X.sub.4 of the single-pinion type is seen to be interposed between the third planetary gear set X.sub.3 and the output shaft and is seen to include the fourth sun gear S.sub.4 drivingly engaged with the third ring gear RG.sub.3 and the second sun gear S.sub.2 so as to be capable of being locked therewith to the gear casing when the second brake B2 is actuated. The third brake B3 is interposed between the fourth ring gear RG.sub.4 and the casing so as to be capable of locking the fourth ring gear RG.sub.4 thereto when the brake B3 is actuated, and the fourth carrier C.sub.4 is drivingly engaged with the output shaft.

Within this embodiment, the radial ratio within each speed range is I.sub.4 = 0.437 and Table 6A shows the relationship between the operation of the clutches and brakes with respect to the reduction gear ratio within each speed range, while Table 6B shows the relationship regarding the number of revolutions and the tangential forces of the elements of the planetary gear sets within each speed range.

Referring now to the embodiment of the invention illustrated within FIG. 7, the fourth planetary gear set X.sub.4 of the single-pinion type is interposed between the third planetary gear set X.sub.3 and the output shaft and includes the fourth ring gear RG.sub.4 drivingly engaged with the third ring gear RG.sub.3 and the second sun gear S.sub.2 so as to be capable of being locked therewith to the gear casing when the second brake B2 is actuated. The third brake B3 is interposed between the fourth sun gear S.sub.4 and the casing so as to be capable of locking the fourth sun gear S.sub.4 thereto when the brake B3 is actuated, and the fourth carrier C.sub.4 is drivingly engaged with the output shaft.

Within this embodiment, the radial ratio within each speed range is I.sub.4 = 0.562, and Table 7A shows the relationship between the operation of the clutches and brakes with respect to the reduction gear ratio within each speed range, while Table 7B shows the relationship regarding the number of revolutions and the tangential forces of all of the elements of the planetary gear sets within each speed range.

Referring now to FIG. 8 still another embodiment of the present invention is disclosed wherein the fourth planetary gear set X.sub.4 of the single-pinion type is interposed between the third planetary gear set X.sub.3 and the output shaft and is seen to include the fourth ring gear RG.sub.4 drivingly engaged with the first and third sun gears S.sub.1 and S.sub.3, and the fourth sun gear S.sub.4 is operatively connected to the third brake B3. Consequently, as the third brake B3 is interposed between the fourth sun gear S.sub.4 and the gear casing, such is capable of locking the fourth sun gear S.sub.4 to the casing when the brake B3 is actuated, the fourth carrier C.sub.4 being drivingly engaged with the output shaft.

Within this embodiment, the radial ratio within each speed range is I.sub.4 = 0.280, and Table 8A shows the relationship between the operation of the clutches and brakes and the reduction gear ratio within each speed range, while Table 8B shows the relationship regarding the number of revolutions and the tangential forces of all the elements of the planetary gear sets within each speed range.

Turning now to FIG. 9, a still further embodiment of the present invention is illustrated wherein the fourth planetary gear set X.sub.4 of the single-pinion type is interposed between the third planetary gear set X.sub.3 and the output shaft, and the fourth sun gear S.sub.4 is drivingly engaged with the first and third sun gears S.sub.1 and S.sub.3. The third brake B3 is interposed between the fourth ring gear RG.sub.4 and the gear casing so as to be capable of locking the fourth ring gear RG.sub.4 thereto when the brake B3 is actuated, and the fourth carrier C.sub.4 is drivingly engaged with the output shaft.

Within this embodiment, the radial ratio within each speed range is I.sub.4 = 0.280 and Table 9A shows the relationship between the operation of the clutches and brakes and the reduction gear ratio within each speed range, while Table 9B shows the relationship regarding the number of revolutions and the tangential forces of all of the elements of planetary gear sets within each speed range.

Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described herein.