Dual-mode electromechanical variable speed transmission apparatus and method of control

A dual-mode electro-mechanical variable speed transmission comprising a four-branch gear system, an input shaft, an output shaft system, a first electric machine, a second electric machine, and a first clutch and a second clutch;

• the output shaft system includes at least an output shaft;
• said four-branch gear system is a four-branch planetary gear set having four co-axial rotatable component branches wherein a first component branch, a second component branch, a third component branch, and a fourth component branch are represented by a small sun gear, a ring gear, a planet carrier, and a large sun gear, respectively;
• and wherein rotational speeds of any two of the four component branches define the speed for the remaining component branches;
• said first electric machine couples in a direct, coaxial, mechanical connection to the small sun gear;
• said input shaft couples directly, via a damping device, to the planet carrier;
• and
• said second electric machine couples only in selective connections to the ring gear with a first speed ratio via the first clutch, or to the large sun gear with a second gear ratio different from the first speed ratio via the second clutch;
• the rotational speeds of the four component branches are represented by a four-branch speed nomograph in which a nomograph distance between the first and third component branches measures Kb units in length, a nomograph distance between the second and third component branches measures Ka units in length, and a nomograph distance between the third and fourth component branches is 1.0 units in length;
• Ka and Kb are characteristic parameters of said four component branch gear system.

A dual-mode electro-mechanical variable speed transmission comprising a four-branch gear system, an input shaft, an output shaft system, a first electric machine, a second electric machine, and at least one clutch;

• said output shaft system includes at least one of an output shaft connected with at least one drive wheel and a differential connected to the output shaft;
• said four-branch gear system has four co-axial rotatable component branches including a first component branch, a second component branch, a third component branch, and a fourth component branch;
• and wherein rotational speeds of any two of the four component branches define the speed for the remaining component branches;
• said first electric machine couples in a clutch-less mechanical connection to the first component branch;
• said input shaft couples directly, via a damping device, to the third component branch;
• and
• said second electric machine couples only in selective connections to the second component branch with a first speed ratio via said at least one clutch, or to the fourth component branch with a second speed ratio different from the first speed ratio via said at least one clutch, whereby the dual-mode electro-mechanical variable speed transmission is switchable between an output power split mode of operation and a compound power split mode of operation solely by the at least one clutch;
• the rotational speeds of the four component branches are represented by a four-branch speed nomograph wherein the nomograph position of the first component branch is at one end of the speed nomograph, the nomograph position of the fourth component branch is at the other end of the speed nomograph;
• and wherein a nomograph distance between the first and third component branches measures Kb units in length, a nomograph distance between the second and third component branches measures Ka units in length, and a nomograph distance between the third and fourth component branches is 1.0 units in length;
• Ka and Kb are characteristic parameters of said four component branch gear system.