Apparatus for controlling vehicle drive system including engine with turbocharger, and lock-up clutch

#This application is based on Japanese Patent Application Nos. 2000-209659 and 2000-209660 both filed on July 21, 2000, 2001-143321 on filed May 14, 2001, and 2001-144259 filed on May 15, 2001, the contents of which are incorporated hereinto by reference.

#1. Field of the Invention

#The present invention relates to a control apparatus for controlling a lock-up clutch provided on an automotive vehicle, and more particularly to techniques for improving fuel economy of a lean-burn engine provided with a turbocharger (turbo-supercharger), by holding the lock-up clutch in an engaged or slipping state in a relatively wide range or area of running condition of the vehicle while the engine is placed in a relatively stable combustion state. The present invention is also concerned with a control apparatus for controlling such a lean-burn engine provided with a turbocharger.

#The above and other objects, features, advantages and technical and industrial significance of the present invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings, in which:

#FIG. 1 is a schematic view showing a part of a drive system of an automotive vehicle having a lock-up clutch control apparatus, which is constructed according to a first embodiment of this invention;

#FIG. 2 is a table indicating a relationship between combinations of frictional coupling devices placed in the engaged state in an automatic transmission of the vehicle drive system of FIG. 1, and operating positions of the automatic transmission which are established by the respective combinations;

#Referring first to the schematic view of FIG. 1, there is shown an arrangement of a drive system of an automotive vehicle having a lock-up clutch control apparatus constructed according to a first embodiment of this invention. The drive system includes a drive source in the form of an engine 10, a clutch 12, a torque converter 14 and an automatic transmission 16. The output of the engine 10 is transmitted to the automatic transmission 16 through the clutch 12 and torque converter 14, and is transmitted from the automatic transmission 16 to drive wheels through a differential gear device and a drive axle, which are well known in the art and are not shown. Between the clutch 12 and the torque converter 14, there is disposed a first motor/generator MG1 which functions as an electric motor and an electric generator. The torque converter 14 includes: a pump impeller 20 connected to the clutch 12; a turbine impeller 24 connected to an input shaft 22 of the automatic transmission 16; a lock-up clutch 26 for directly connecting the pump and turbine impellers 20, 24; a one-way clutch 28; and a stator impeller 30 which is prevented by the one-way clutch from rotating in one of opposite directions.

#The automatic transmission 16 includes a first transmission unit 32 having two speed positions, that is, a high-speed position and a low-speed position, and a second transmission unit 34 having five operating positions, that is, one reverse drive position and four forward drive positions. The first transmission unit 32 includes a high-low planetary gear device 36 having a sun gear S0, a ring gear R0, a carrier K0, and planetary gears P0 which are rotatably supported by the carrier K0 and which mesh with the sun gear S0 and ring gear R0. The first transmission unit 32 further includes a clutch C0 disposed between the sun gear S0 and the carrier K0, and a brake B0 disposed between the sun gear S0 and a housing 38.

#The second transmission unit 34 includes a first planetary gear set 40, a second planetary gear set 42, and a third planetary gear set 44. The first planetary gear set 40 includes a sun gear S1, a ring gear R1, a carrier K1, and planetary gears P1 which are rotatably supported by the carrier K1 and which mesh with the sun gear S1 and ring gear R1. The second planetary gear set 42 includes a sun gear S2, a ring gear R2, a carrier K2, and planetary gears P2 which are rotatably supported by the carrier K2 and which mesh with the sun gear S2 and ring gear R2. The third planetary gear set 44 includes a sung gear S3, a ring gear R3, a carrier K3, and planetary gears P3 which are rotatably supported by the carrier K3 and which mesh with the sun gear S3 and ring gear R3.