Trimmer valve

Claim 2

In a load driving transmission (10) of the type including a shaft mounted for rotation (36), first and second gears (44, 46) of different ratio mounted for rotation on the shaft and relative to each other, clutch means (42) selectively engagable to clutch either one of the gears to the shaft during a no-load driving state of the shaft, a powershift clutch (48) operative when engaged to frictionally connect the shaft into a load driving state while either one of the gears is clutched thereto, a control system operative to engage the clutch means to effect selective clutching of the gears to the shaft and operative thereafter to apply a force for engaging the powershift clutch, the improvement comprising: means (364) operative to vary the force to control the oncoming engagement rate of the powershift clutch, said means operative where first gear is clutched to the shaft to progressively increase the force along a first path and operative when the second gear is clutched to the shaft to progressively increase the force along a second path.

Claim 3

The transmission of Claim 1, wherein the control system includes fluid pressure means (140) for engaging the clutches and said means operative including: a trimmer valve (360) including: a first port (362a) which receives a first pressurized fluid from the control system for applying the force engaging the powershift clutch; a valving means (488, 490, 492) operative to dump decreasing amounts of the pressurized fluid from the port for controlling the pressure rise and therefore the oncoming engagement rate of the powershift clutch; a second port (364a) which receives a second pressurized fluid from the control system in response to clutching of the first gear by the clutch means; and control means (494) responsive to the absence and presences of said second pressurized fluid at said second port to vary the dumping rate of the valving means, said control means operative to vary the decreasing dumping rate of said valving means along said first path in response to the absence of said pressurized fluid at said second port and along said second path in response to the presence of said pressurized fluid at said second port.

Claim 4

The transmission of Claim 1 or 2, wherein said clutch means is a synchronizer clutch having friction and jaw clutch portions.

Claim 5

The transmission of Claim 2, wherein said clutch means is a synchronizer clutch having friction and jaw clutch portions and wherein said control means includes; a second trimmer valve (364) having a valving means (494, 504) operative to dump decreasing amounts of said pressurized fluid from said second port for controlling the pressure rise and therefore the synchronizing rate of said friction clutch portion.

Claim 6

The transmission of Claim 1, wherein the control system includes fluid pressure means (140) for engaging the clutches and said means operative comprises a trimmer valve (360) including: a bore (486); a first port (362a) which receives a first pressurized fluid from the control system for applying the force engaging the powershift clutch; an exhaust port (362b) axially spaced from the first port; a valving member (488) disposed in said bore with one end in direct communication with the first port and slidably moveable from a position blocking communication between the ports to a position allowing communication between the ports in response to the first pressure applying a fluid force to the surface area of the one end of said valving member; a first piston (490) slidably disposed in the bore at the other end of the valving member and defining thereith an expandable chamber communicating with the first port via an orifice (488d); a spring (492) having one end biasing the piston toward the valving member for moving the valving member to the blocking position with a spring force which yields to said fluid force and increases with said fluid force; a second port (364a) which receives a second pressurized fluid from the control system to effect clutching of the first gear by the clutch means; and a second piston (494) slidably disposed in the bore and providing a moveable reaction surface for the spring, said second piston moveable from a position allowing a maximum extension of the spring in the absence of said second pressure and moveable to a position allowing a minimum extension of the spring in response to the presence of said second pressure.

Claim 7

The transmission of Claim 5, wherein said clutch means is a synchronizer clutch having friction and jaw clutch portions and wherein said second port and piston combine with a second valving member (504), orifice (504e), and exhaust port (364b) to define a second trimmer valve substantially the same as the first defined trimmer valve and dipsosed in the bore in mirror image fashion with said second valving member operative to dump decreasing amounts of said pressurized fluid from said second port for controlling the pressure rise and therefore the synchronizing rate of said friction clutch portion and with said second piston and valving member defining a second expandable chamber operative when expanded and contracted to respectively effect said minimum and maximum extensions of the spring.