Hydromechanical transmission and control

Claim 2

An engine driven transmission and control comprising: input means drivingly connected with the engine; output means; variable positive displacement hydrostatic transmission means drivingly connected with said input means including displacement control means for controlling the drive ratio of the hydrostatic transmission; gearing means drivingly connected between said hydrostatic transmission and said output means including selectively engagable drive ratio establishing means for selectively establishing low and high ratio drives; a source of fluid pressure; hydrostatic transmission control means including valve means in fluid communication with said source for providing a variable pressure source for selectively controlling the displacement control means between minimum and maximum values at a setting determined by the pressure level of the variable pressure source when the low ratio is established in said gearing means; and shift control means in fluid communication with said source of fluid pressure for controlling the interchange of said drive ratio establishing means including means for directing fluid pressure to said valve means to reduce the pressure level of the variable pressure source and the hydrostatic transmission displacement and for permitting the variable pressure to be repeated for selectively controlling the displacements between the minimum and maximum values when the high ratio is established in said gearing means.

Claim 3

An engine driven hydromechanical transmission and control comprising; input means; a variable displacement hydrostatic transmission drivingly connected to said input means including means for selectively controlling the displacement; gearing means drivingly connecting with said hydrostatic transmission including selectively operable friction drive establishing means for providing low and high ratio drives in said gearing means; output means drivingly connected with said gearing means; a source of fluid pressure; operator controlled valve means in fluid communication with said source for providing a drive ratio request signal; ratio governor means in fluid communication with said source and said operator controlled valve means for providing a governor signal in response to the drive ratio request signal and operating parameters of the engine; ratio signal means in fluid communication with said source and being responsive to the governor signal for providing a controlled variable pressure signal and being operatively connected to the displacement controlling means to establish drive ratios in said hydrostatic transmission at settings in accordance with the controlled variable pressure signal; and shift control valve means in fluid communication with said source for selectively establishing engagement of said friction drive establishing means, including means for communicating fluid pressure to said ratio signal means to reduce the controlled variable pressure signal and the hydrostatic drive ratio and for permitting the controlled variable pressure signal to repeat to reestablish the drive ratios in the hydrostatic transmission in accordance with the controlled variable pressure signal when the high ratio drive is established.

Claim 4

An engine driven hydromechanical transmission and control comprising; input means; a variable displacement hydrostatic transmission drivingly connected to said input means including means for selectively controlling the displacement; gearing means drivingly connecting with said hydrostatic transmission including selectively operable friction drive establishing means for providing low and high ratio drives in said gearing means; output means drivingly connected with said gearing means; a source of fluid pressure; operator controlled valve means in fluid communication with said source for providing a drive ratio request signal; ratio governor means in fluid communication with said source and said operator controlled valve means for providing a governor signal in response to the drive ratio request signal and operating parameters of the engine; ratio signal means in fluid communication with said source and being responsive to the governor signal for providing a controlled variable pressure signal and being operatively connected to the displacement controlling means to establish drive ratios in said hydrostatic transmission at settings in accordance with the controlled variable pressure signal; and shift control valve means in fluid communication with said source for selectively establishing engagement of said friction drive establishing means, including means for communicating fluid pressure to said ratio signal means to reduce the controlled variable pressure signal and the hydrostatic drive ratio and for permitting the controlled variable pressure signal to repeat to reestablish the drive ratios in the hydrostatic transmission in accordance with the controlled variable pressure signal when the high ratio drive is established.

Claim 5

An engine driven hydromechanical transmission and control for use with a vehicle comprising: engine throttle control means; engine speed signal means; vehicle brake means; input means; a variable displacement hydrostatic transmission drivingly connected to said input means including means for selectively controlling the displacement; gearing means drivingly connecting with said hydrostatic transmission including selectively operable friction drive establishing means for providing low and high ratio drives In said gearing means; output means drivingly connected with said gearing means; a source of fluid pressure; operator controlled valve means in fluid communication with said source for providing a variable drive ratio request signal; ratio governor means in fluid communication with said source and said operator controlled valve means for providing a governor signal in response to the drive ratio request signal, said engine throttle control means and said engine speed signal means; ratio signal means in fluid communication with said source and being responsive to the governor signal for providing a controlled variable pressure signal and being operatively connected to the displacement controlling means to establish drive ratios in said hydrostatic transmission at settings in accordance with the controlled variable pressure signal; shift control valve means in fluid communication with said source for selectively establishing engagement of said friction drive establishing means, including means for communicating fluid pressure to said ratio signal means to reduce the controlled variable pressure signal and the hydrostatic drive ratio and for permitting the controlled variable pressure signal to repeat to reestablish the drive ratios in the hydrostatic transmission in accordance with the controlled variable pressure signal when the high ratio drive is established; and brake signal valve means responsive to operation of said vehicle brake means for providing a brake signal to said operator controlled valve means to reduce the variable drive ratio request signal.

Claim 6

An engine driven hydromechanical transmission and control for use with a vehicle comprising: engine throttle control means; engine speed signal means; vehicle brake means; input means; a variable displacement hydrostatic transmission drivingly connected to said input means including means for selectively controlling the displacement; gearing means drivingly connecting with said hydrostatic transmission including selectively operable friction drive establishing means for providing low and high ratio drives In said gearing means; output means drivingly connected with said gearing means; a source of fluid pressure; operator controlled valve means in fluid communication with said source for providing a variable drive ratio request signal; ratio governor means in fluid communication with said source and said operator controlled valve means for providing a governor signal in response to the drive ratio request signal, said engine throttle control means and said engine speed signal means; ratio signal means in fluid communication with said source and being responsive to the governor signal for providing a controlled variable pressure signal and being operatively connected to the displacement controlling means to establish drive ratios in said hydrostatic transmission at settings in accordance with the controlled variable pressure signal; shift control valve means in fluid communication with said source for selectively establishing engagement of said friction drive establishing means, including means for communicating fluid pressure to said ratio signal means to reduce the controlled variable pressure signal and the hydrostatic drive ratio and for permitting the controlled variable pressure signal to repeat to reestablish the drive ratios in the hydrostatic transmission in accordance with the controlled variable pressure signal when the high ratio drive is established; and brake signal valve means responsive to operation of said vehicle brake means for providing a brake signal to said operator controlled valve means to reduce the variable drive ratio request signal.

Claim 7

In combination an engine driven hydromechanical transmission and control, said combination comprising; input means; a variable displacement hydrostatic transmission including a variable displacement hydraulic pump drivingly connected to said input means, a variable displacement hydraulic motor and means for selectively controllint the displacements of said pump and motor; gearing means drivingly connecting with said hydraulic motor including selectively operable friction drive establishing means for providing low and high ratio drives in said gearing means; output means drivingly connected with said gearing means; a source of fluid pressure; operator controlled valve means in fluid communication with said source for providing a drive ratio request signal including signal means in fluid communication with said hydraulic pump being operable to reduce the drive ratio request signal at a predetermined pressure level in said pump; ratio governor means in fluid communication with said source and said operator controlled valve means for providing a governor signal in response to the drive ratio request signal and operating parameters of the engine; ratio signal means in fluid communication with said source and being responsive to the governor signal for providing a controlled variable pressure signal and being operatively connected to the displacement controlling means to establish drive ratios in said hydrostatic transmission at settings in accordance with the controlled variable pressure signal; and shift control valve means in fluid communication with said source for selectively establishing engagement of said friction drive establishing means, including means for communicating substantially constant fluid pressure bias to said ratio signal means to reduce the controlled variable pressure signal and the hydrostatic drive ratio and for permitting the controlled variable pressure signal to repeat to reestablish the drive ratio in the hydrostatic transmission in accordance with the controlled variable pressure signal when the high ratio drive is established.

Claim 8

In combination an engine driven hydromechanical transmission and control, said combination comprising; input means; a variable displacement hydrostatic transmission including a variable displacement hydraulic pump drivingly connected to said input means, a variable displacement hydraulic motor and means for selectively controllint the displacements of said pump and motor; gearing means drivingly connecting with said hydraulic motor including selectively operable friction drive establishing means for providing low and high ratio drives in said gearing means; output means drivingly connected with said gearing means; a source of fluid pressure; operator controlled valve means in fluid communication with said source for providing a drive ratio request signal including signal means in fluid communication with said hydraulic pump being operable to reduce the drive ratio request signal at a predetermined pressure level in said pump; ratio governor means in fluid communication with said source and said operator controlled valve means for providing a governor signal in response to the drive ratio request signal and operating parameters of the engine; ratio signal means in fluid communication with said source and being responsive to the governor signal for providing a controlled variable pressure signal and being operatively connected to the displacement controlling means to establish drive ratios in said hydrostatic transmission at settings in accordance with the controlled variable pressure signal; and shift control valve means in fluid communication with said source for selectively establishing engagement of said friction drive establishing means, including means for communicating substantially constant fluid pressure bias to said ratio signal means to reduce the controlled variable pressure signal and the hydrostatic drive ratio and for permitting the controlled variable pressure signal to repeat to reestablish the drive ratio in the hydrostatic transmission in accordance with the controlled variable pressure signal when the high ratio drive is established.

Claim 9

An engine driven hydromechanical transmission and control comprising; input means; a variable displacement hydrostatic transmission drivingly connected to said input means including means for selectively controlling the displacement; gearing means drivingly connecting with said hydrostatic transmission including selectively operable friction drive establishing means for providing low and high ratio drives in said gearing means; output means drivingly connected with said gearing means; a source of fluid pressure; operator controlled valve means in fluid communication with said source for providing a drive ratio request signal; ratio governor means in fluid communication with said source and said operator controlled valve means for providing a governor signal in response to the drive ratio request signal and operating parameters of the engine; ratio signal means in fluid communication with said source and being responsive to the governor signal for providing a controlled variable pressure signal and being operatively connected to the displacement controlling means to establish drive ratios in said hydrostatic transmission in accordance with the controlled variable pressure signal, and being operatively connected with said operator controlled valve means for modifying the drive ratio request signal in accordance with the controlled variable pressure signal; and shift control valve means in fluid communication with said source for selectively establishing engagement of said friction drive establishing means, including means for communicating fluid pressure to said ratio signal means to reduce the controlled variable pressure signal and the hydrostatic drive ratio and for permitting the controlled variable pressure signal to repeat to reestablish the drive ratios in the hydrostatic transmission in accordance with the controlled variable pressure signal when the high ratio drive is established.

Claim 10

An engine driven hydromechanical transmission and control comprising; input means; a variable displacement hydrostatic transmission drivingly connected to said input means including means for selectively controlling the displacement; gearing means drivingly connecting with said hydrostatic transmission including selectively operable friction drive establishing means for providing low and high ratio drives in said gearing means; output means drivingly connected with said gearing means; a source of fluid pressure; operator controlled valve means in fluid communication with said source for providing a drive ratio request signal; ratio governor means in fluid communication with said source and said operator controlled valve means for providing a governor signal in response to the drive ratio request signal and operating parameters of the engine; ratio signal means in fluid communication with said source and being responsive to the governor signal for providing a controlled variable pressure signal and being operatively connected to the displacement controlling means to establish drive ratios in said hydrostatic transmission in accordance with the controlled variable pressure signal, and being operatively connected with said operator controlled valve means for modifying the drive ratio request signal in accordance with the controlled variable pressure signal; and shift control valve means in fluid communication with said source for selectively establishing engagement of said friction drive establishing means, including means for communicating fluid pressure to said ratio signal means to reduce the controlled variable pressure signal and the hydrostatic drive ratio and for permitting the controlled variable pressure signal to repeat to reestablish the drive ratios in the hydrostatic transmission in accordance with the controlled variable pressure signal when the high ratio drive is established.

Claim 11

In combination an engine driven hydromechanical transmission and control for use with a vehicle having vehicle brake means, said combination comprising; input means; a variable displacement hydrostatic transmission including a variable displacement hydraulic pump drivingly connected to said input means, a variable displacement hydraulic motor and means for selectively controlling the displacements of said pump and motor; gearing means drivingly connecting with said hydraulic motor including selectively operable friction drive establishing means for providing low and high ratio drives in said gearing means; output means drivingly connected with said gearing means; a source of fluid pressure; operator controlled valve means in fluid communication with said source for providing a drive ratio request signal including signal means in fluid communication with said hydraulic pump being operable to reduce the drive ratio request signal at a predetermined pressure level in said pump; ratio governor means in fluid communication with said source and said operator controlled valve means for providing a governor signal in response to the drive ratio request signal and operating parameters of the engine; ratio signal means in fluid communication with said source and being responsive to the governor signal for providing a controlled variable pressure signal and being operatively connected to the displacement controlling means to establish drive ratios in said hydrostatic transmission at settings in accordance with the controlled variable pressure signal; shift control valve means in fluid communication with said source for selectively establishing engagement of said friction drive establishing means, including means for communicating fluid pressure to said ratio signal means to reduce the controlled variable pressure signal and the hydrostatic drive ratio and for permitting the controlled variable pressure signal to repeat to reestablish the drive ratios in the hydrostatic transmission in accordance with the controlled variable pressure signal when the high ratio drive is established; and brake signal valve means responsive to operation of said vehicle brake means for providing a brake signal to said operator controlled valve means to reduce the variable drive ratio request signal.

Claim 12

In combination an engine driven hydromechanical transmission and control for use with a vehicle having vehicle brake means, said combination comprising; input means; a variable displacement hydrostatic transmission including a variable displacement hydraulic pump drivingly connected to said input means, a variable displacement hydraulic motor and means for selectively controlling the displacements of said pump and motor; gearing means drivingly connecting with said hydraulic motor including selectively operable friction drive establishing means for providing low and high ratio drives in said gearing means; output means drivingly connected with said gearing means; a source of fluid pressure; operator controlled valve means in fluid communication with said source for providing a drive ratio request signal including signal means in fluid communication with said hydraulic pump being operable to reduce the drive ratio request signal at a predetermined pressure level in said pump; ratio governor means in fluid communication with said source and said operator controlled valve means for providing a governor signal in response to the drive ratio request signal and operating parameters of the engine; ratio signal means in fluid communication with said source and being responsive to the governor signal for providing a controlled variable pressure signal and being operatively connected to the displacement controlling means to establish drive ratios in said hydrostatic transmission at settings in accordance with the controlled variable pressure signal; shift control valve means in fluid communication with said source for selectively establishing engagement of said friction drive establishing means, including means for communicating fluid pressure to said ratio signal means to reduce the controlled variable pressure signal and the hydrostatic drive ratio and for permitting the controlled variable pressure signal to repeat to reestablish the drive ratios in the hydrostatic transmission in accordance with the controlled variable pressure signal when the high ratio drive is established; and brake signal valve means responsive to operation of said vehicle brake means for providing a brake signal to said operator controlled valve means to reduce the variable drive ratio request signal.