US 4,476,748 A · Preselect shift control

Abstract

Disclosed is an automatic control system for a powershift, preselect transmission (10) including a plurality of power paths (36, 38) alternately connectable between input (12) and output (20) shafts by first engaging selected ones of synchronizer clutches (42, 74, 84) associated with each of a plurality speed ratio gears (44, 46, 76, 78, 80) in each path and then alternately engaging a powershift clutch (48, 82) associated with each path. The control system includes a hydraulic logic system (118) which may be electronic and a hydraulic and shift valve system which may be electrically controlled should the logic be electronic. The control system preselects ratio gears in a nondriving path and then alternately engages the powershift clutches to switch driving connections from one path to the other. The logic system includes an improved reverse sequence valve (132) and improved shift valves (124, 126, 128). The shift valve system includes the feature of trimmer valves (364, 370, 372, 374) to control the engagement rate of the synchronizer clutches and combination trimmer valves (360, 366) to control the engagement rate of the powershift clutches.

Claims9

Dependent claims

In a powershift, preselect transmission of the type including a plurality of power paths alternately connectable between input and output shafts by an automatic control system operative to effect preselective engagement of ones of synchronizer clutches associated with each of a plurality of step ratio gears in each path and then to effect alternate engagement of a powershift clutch associated with each path, the improvement comprising;

shift selector means defining a portion of said control system and including means moveable between forward, neutral, and reverse positions, said shift selector means operative in the forward and reverse positions to allow engagement of the powershift clutches and operative in the neutral position to prevent engagement of the powershift clutches;
synchro shift means operative at any given time to effect the preselective engagement of one of the synchronizer clutches in each path independent of said shift selector position.

In a powershift, preselect transmission of the type including a plurality of power paths alternately, connectable between input and output shafts by an automatic control system operative to effect preselective engagement of ones of synchronizer clutches associated with each of a plurality of forward speed ratio gears in each path and then operative to effect alternate engagement of a powershift clutch associated with each path to complete driving connections between the shafts, the improvement comprising:

shift selector means including means moveable between forward, neutral, and reverse positions;
powershift means operative in response to said shift selector forward position to effect said alternate engagements completing said driving connections in response to first predetermined amounts of increased and decreased output shaft speeds;
synchro shift means operative at any given time to effect said preselective engagements of ones of the synchronizer clutches in each path independent of said shift selector position, said synchro shift means including means responsive to second predetermined amounts of increased and decreased output shaft speeds spaced between said first predetermined amounts to effect said preselective engagements of the synchronizer clutch associated with the next upshift or downshift ratio gear in a nondrivingly connected path.

Dependencies are inferred from the claim text.

Preselect shift control

Life of this patent

Preselect shift control

Life of this patent

Abstract

Claims9