Speed change control system for automatic transmission

Claim 2

A speed change control system for an automatic transmission comprising an output shaft, a first gear element selectively engageable with said output shaft, a second gear element selectively engageable with said output shaft for lower speed operation than said first gear element, at least a first friction engaging means and a second friction engaging means arranged in back-to-back relationship with one another, said first friction engaging means arranged to connect said first gear element to said output shaft, said second friction engaging means arranged to connect said second gear element to said output shaft, said first friction engaging means including a first servo oil chamber, said second friction engaging means including a second servo oil chamber, said first and second friction engaging means having at least one common member, control circuit means for supplying hydraulic oil to and for discharging hydraulic oil from said first servo oil chamber and said second servo chamber for providing a higher speed range by engaging said first friction engaging means for connecting said first gear element to said output shaft and by releasing said second friction engaging means for disconnecting said second gear element from said output shaft and for providing the lower speed range by engaging said second friction engaging means for connecting said second gear element to said output shaft and by releasing said first friction engaging means for disconnecting said first gear element from said output shaft, and said control circuit means including means associated with said first friction engaging means and said common member maintaining hydraulic oil pressure in said second servo oil chamber after hydraulic oil has been supplied to said first servo oil chamber and for effecting relative movement between said common member and a part of said friction engaging means for releasing oil from said second servo oil chamber so that said second friction engagement means are released after a predetermined progress has been aChieved in the engagement of said first friction engaging means.

Claim 3

A speed change control system, as set forth in claim 1, wherein said common member comprises a partition plate secured on said output shaft, said partition plate extends transversely of and outwardly from said output shaft, said first friction engaging means comprises a drum encircling said output shaft and spline-fitted to said partition plate, said drum disposed in radially spaced relationship to said output shaft, an assembly of alternating plates and discs extending transversely of said output shaft and arranged in juxtaposed relationship to one another, one of the plates and the discs is fixed to said drum and the other one is fixed to said first gear element, a piston assembly associated with said partition plate and having a surface disposed in juxtaposed relationship with said partition plate and defining therebetween said first servo oil chamber, said piston assembly is axially displaceable on said shaft into contact with said assembly of plates and discs, means for connecting said control circuit means to said first servo chamber for supplying hydraulic pressure thereto, the surface of said drum in engagement with said partition plate having a groove therein, said means associated with said first friction engaging means and said common member comprises spring means disposed within said groove for axially displacing said drum relative to said partition plate when a predetermined value is reached as hydraulic pressure within said first servo oil chamber displaces said piston assembly against said assembly of plates and discs, and a plug fitted in and extending through said drum in contact with said partition plate, said second friction engaging means positioned adjacent said partition plate and extending therefrom on said output shaft on the opposite side of said partition plate from said first friction engaging means, said second friction engaging means including a piston assembly associated with said partition plate and having a surface disposed in juxtaposed relationship with said partition plate and defining therebetween said second servo oil chamber, said second friction engaging means having an oil discharge port in communication with said second servo oil chamber, said plug arranged to close said oil discharge port when said first friction engaging means is in the released state for closing said second servo oil chamber and for opening said discharge port when said first engaging means is in the engaged state with said output shaft or discharging oil pressure from said second servo oil chamber, and said control circuit means including a shift valve arranged for shifting from operation by said second gear element to operation by said first gear element for guiding the flow of hydraulic oil into said first servo chamber and for shutting off the flow of hydraulic oil into said second oil chamber while said second friction engaging means remains engaged.

Claim 4

A speed change control system, as set forth in claim 2, wherein said second friction engaging means comprises a second drum secured to said partition portion plates and encircling said output shaft, said second drum extending in the axial direction of said output shaft on the opposite side of said partition plate from said first engaging means, and a second assembly of alternating plates and discs extending transversely of said shaft and arranged in juxtaposed relationship, one of the plates and discs is fixed to said second drum and the other one is fixed to said second gear element.

Claim 5

A speed change control system, as set forth in claim 2 wherein in a plane extending radially through said shaft said partition plate has an I-shaped cross-section, said partition plate comprising a radially inner boss positioned on said output shaft, a radially outwardly extending web, and a rim secured to and extending transversely of the radially outer end of said rim.

Claim 6

A speed change control system, as set forth in claim 4, wherein saiD piston assembly comprises a piston member disposed in juxtaposed relationship to said partition plate and extending between said boss and said rim of said partition plate, an annular seat member secured to the outer surface of said boss of said partition plate and spaced axially from said web of said partition plate, and a spring positioned between said seat and the adjacent surface of said piston member for biasing said piston member into contact with said web of said partition plate.