PARKING LOCK MECHANISM FOR AUTOMATIC TRANSMISSION

Abstract

An automatic transmission includes primary drive gears that are fixed on main-shaft sleeve provided on a main shaft; primary driven gears which are rotatably provided on a countershaft, which constantly mesh with the primary drive gears, and which are selectively connected to the countershaft. Further, a first clutch engages and disengages power between the main shaft and the main-shaft sleeve; and secondary drive gears are rotatably provided on the main shaft, and are selectively connected to the main shaft. Secondary driven gears which are fixed on a countershaft sleeve provided on the countershaft, and which constantly mesh with the secondary drive gears. A second clutch engages and disengages power between the countershaft and the countershaft sleeve. A parking lock position is established when clutches are disengaged and one forward gear and a reverse gear are concurrently connected to the countershaft.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an expanded schematic diagram showing the configuration of a power unit 1A according to a first embodiment of the present invention, with each of rotating shafts thereof being included;

FIG. 2 is a schematic diagram describing the operation at the time when the vehicle starts in the first-speed gear;

FIG. 3 is a schematic diagram describing the operation at the time when the gear is shifted from the first-speed gear to the second-speed gear;

FIG. 4 is a schematic diagram describing the operation at the time when the gear is shifted from the second-speed gear to the third-speed gear;

FIG. 5 is a schematic diagram describing the operation at the time when the gear is shifted from the third-speed gear to the fourth-speed gear;

FIG. 6 is a schematic diagram describing the operation at the time when the gear is in the reverse gear;

FIG. 7 is a schematic diagram describing the parking-lock operation; and

FIG. 8 is a diagram for describing a power unit 1B according to a second embodiment, with a transmission of the power unit 1B in the second embodiment being described side by side with a transmission of the power unit 1A in the first embodiment.

Claims

1. A parking lock mechanism for an automatic transmission, comprising: a main shaft having a main shaft sleeve rotatable and coaxial with respect thereto;a countershaft substantially parallel to said main shaft, and having a countershaft sleeve rotatable and coaxial with respect to said countershaft;primary drive gears fixed on said main-shaft sleeve;primary driven gears rotatably provided on said countershaft, which constantly mesh with corresponding primary drive gears, and which are selectively connected to said countershaft;a first clutch that engages and disengages power between said main shaft and said main-shaft sleeve;secondary drive gears rotatably provided on said main shaft, and which are selectively connected to said main shaft;secondary driven gears fixed on said countershaft sleeve, and which constantly mesh with corresponding secondary drive gears;a second clutch that engages and disengages power between said countershaft and said countershaft sleeve;a reverse drive gear fixed on said main-shaft sleeve; anda reverse driven gear rotatably provided on said countershaft, which constantly meshes with an intermediate gear meshing constantly with said reverse drive gear, and which is selectively connected to said countershaft,wherein, in a parking lock position, said first and second clutches are in a neutral position, and one of said forward driven gears fixed on said countershaft, as well as said reverse driven gear fixed on said countershaft are concurrently connected to said countershaft.

2. The parking lock mechanism for an automatic transmission as recited in claim 1, further comprising: a shift drum driven by an electric motor;a cam groove programmed in advance and formed in said shift drum;a shifter slideable in an axial direction in response to movement of said cam groove; andengaging means, slideable in an axial direction in response to movement of said shifter, for engaging and disengaging said gears that are rotatable relatively to said main shaft and said countershaft,wherein, in said parking lock position, said one forward driven gear on said countershaft and said reverse driven gear on said countershaft are concurrently connected to said countershaft in response to movement of said shift drum.