Pressure controls for inching clutches

Claim 2

A transmission control system for a vehicle having fluid actuated frictional engaging means, said system comprising: a fluid pressure generating source; a first fluid conduit means for connecting said source to said frictional engaging means; a regulator valve assembly connected with said first conduit means for controlling automatically fluid pressure supplied from said source and for delivering the controlled fluid pressure to said frictional engaging means; said regulator valve assembly including a first stepped spool valve slidably fitted in a housing for defining a first, a second and a third chambers with a spring means interposed in said first chamber for urging said spool valve in one direction, said second chamber constantly being in fluid communication with said first fluid conduit means; a second fluid conduit means for conveying fluid pressure from said source to said third chamber for urging said spool valve to move against said spring means; and an inching valve means provided in said first and second conduit means and including a housing and a second spool valve slidably fitted therein and being operatively connected to a manually operable pedal, said second spool valve comprising a first land for opening said second conduit means upon depression of said pedal and flow restricting means for controlling fluid pressure to be supplied to said frictional engaging means in response to the sliding movement of said second valve of said inching valve means, whereby said controlled fluid pressure is rapidly lowered, and said lowered fluid pressure is gradually regulated in response to the degree of depression of said pedal.

Claim 3

A transmission control system as set forth in claim 1, wherein said frictional engaging means comprises: a forward and a reverse fluid actuated clutch means; and a shift control valve unit being connected with said first fluid conduit means for selectively controlling a pair of fluid conduits connecting an outlet port of said regulator valve assembly, respectively, to said forward and reverse clutch means.

Claim 4

A transmission control system as set forth in claim 1, wherein said regulator valve assembly comprises a drain port provided in the housing, said drain port being normally closed by a land of said first stepped spool valve and being opened to communicate with said second chamber thereof according to the sliding movement of said first stepped spool valve when a predetermined pressure is applied to said third chamber.

Claim 5

A transmission control system as set forth in claim 1, wherein said housing of the inching valve means further comprises a drain port normally closed by a second land of said second spool valve.

Claim 6

A transmission control system as set forth in claim 4, wherein said flow restricting means comprises two smaller diameter lands connected to each other, one of said lands being for throttling the fluid pressure to be supplied from said source in response to the slidable movement of said second spool valve of said inching valve means, and the other land being for throttling the fluid pressure to be drained through said drain port normally closed by said second land in response to the movement of said second spool valve.

Claim 7

A transmission control system for a vehicle having fluid actuated frictional engaging means, said system comprising: a fluid pressure generating source adapted for providing pressurized fluid of an amount in proportion to the revolution rate of an engine of the vehicle; a first fluid Conduit means for connecting said source to said frictional engaging means; a regulator valve assembly connected with said first conduit means for controlling automatically fluid pressure supplied from said source and for delivering the controlled fluid pressure to said frictional engaging means; said regulator valve assembly including a stepped spool valve slidably fitted in a housing for defining a first, a second and a third chambers with a spring means interposed in said first chamber for urging said spool valve in one direction, said second chamber constantly being in fluid communication with said first fluid conduit means; a second fluid conduit means for conveying fluid pressure from said source to said third chamber for urging said spool valve to move against said spring means; said fluid pressure being conveyed to said third chamber being constantly drained through an orifice in said spool valve; and an inching valve means provided in said first and second conduit means and being cooperatively connected to a manually operable pedal for opening said second conduit means upon depression of said pedal, whereby said controlled fluid pressure is rapidly lowered, and for then gradually regulating said lowered fluid pressure in response to the degree of depression of said pedal.

Claim 8

A transmission control system for a vehicle having fluid actuated frictional engaging means, said system comprising: a fluid pressure generating source adapted for providing pressurized fluid of an amount in proportion to the revolution rate of an engine of the vehicle; a first fluid Conduit means for connecting said source to said frictional engaging means; a regulator valve assembly connected with said first conduit means for controlling automatically fluid pressure supplied from said source and for delivering the controlled fluid pressure to said frictional engaging means; said regulator valve assembly including a stepped spool valve slidably fitted in a housing for defining a first, a second and a third chambers with a spring means interposed in said first chamber for urging said spool valve in one direction, said second chamber constantly being in fluid communication with said first fluid conduit means; a second fluid conduit means for conveying fluid pressure from said source to said third chamber for urging said spool valve to move against said spring means; said fluid pressure being conveyed to said third chamber being constantly drained through an orifice in said spool valve; and an inching valve means provided in said first and second conduit means and being cooperatively connected to a manually operable pedal for opening said second conduit means upon depression of said pedal, whereby said controlled fluid pressure is rapidly lowered, and for then gradually regulating said lowered fluid pressure in response to the degree of depression of said pedal.

Claim 9

A transmission control system as set forth in claim 6, wherein said spool valve is formed with a passage in which is provided said orifice for fluidically connecting said first chamber to said third chamber, said first chamber being always open to a drain port.

Claim 10

A transmission control system for a vehicle having fluid actuated frictional engaging means, said system comprising: a fluid pressure generating source; a first fluid conduit means for connecting said source to said frictional engaging means; a regulator valve assembly connected with said first conduit means for controlling automatically fluid pressure supplied from said source and for delivering the controlled fluid pressure to said frictional engaging means; said regulator valve assembly including a stepped spool valve slidably fitted in a housing for defining a first, a second and a third chambers with a spring means interposed in said first chamber for urging said spool valve in one direction, said second chamber constantly being in fluid communication with said first fluid conduit means; a second fluid conduit means for conveying fluid pressure from said source to said third chamber for urging said spool valve to move against said spring means; and an inching valve means provided in said first and second conduit means and being cooperatively connected to a manually operable pedal for opening said second conduit means upon depression of said pedal, whereby said controlled fluid pressure is rapidly lowered, and for then gradually regulating said lowered fluid pressure in response to the degree of depression of said pedal, wherein said inching valve means comprises: a housing having a bore formed therein and an inside end wall; a spool valve slidably mounted in said bore and having first, second and third lands thereon and first and second smaller diameter lands thereon, said first and second smaller diameter lands being adapted for forming a first and second orifices, respectively, with respect to the inside wall of the housing; a first drain chamber formed between the first land and the inside end wall of said housing; a second hydraulic chamber formed between the first and second lands being normally interconnected to said first conduit means; a drain port normally closed by said first land; and a third chamber provided between said second and third lands being normally interrupted from said second conduit means by said second land, whereby when the spool valve of said inching valve means is moved by said pedal said second conduit means is opened for establishing fluid communication between said source and said third chamber of sAid regulator valve assembly, and when the spool valve is further moved fluid under pressure conveyed to said second chamber of said inching valve means is throttled by said second orifice while at the same time said second chamber of said inching valve means is connected to said drain port of said inching valve means via said first orifice.

Claim 11

A transmission control system for a vehicle having fluid actuated frictional engaging means, said system comprising: a fluid pressure generating source; a first fluid conduit means for connecting said source to said frictional engaging means; a regulator valve assembly connected with said first conduit means for controlling automatically fluid pressure supplied from said source and for delivering the controlled fluid pressure to said frictional engaging means; said regulator valve assembly including a stepped spool valve slidably fitted in a housing for defining a first, a second and a third chambers with a spring means interposed in said first chamber for urging said spool valve in one direction, said second chamber constantly being in fluid communication with said first fluid conduit means; a second fluid conduit means for conveying fluid pressure from said source to said third chamber for urging said spool valve to move against said spring means; and an inching valve means provided in said first and second conduit means and being cooperatively connected to a manually operable pedal for opening said second conduit means upon depression of said pedal, whereby said controlled fluid pressure is rapidly lowered, and for then gradually regulating said lowered fluid pressure in response to the degree of depression of said pedal, wherein said inching valve means comprises: a housing having a bore formed therein and an inside end wall; a spool valve slidably mounted in said bore and having first, second and third lands thereon and first and second smaller diameter lands thereon, said first and second smaller diameter lands being adapted for forming a first and second orifices, respectively, with respect to the inside wall of the housing; a first drain chamber formed between the first land and the inside end wall of said housing; a second hydraulic chamber formed between the first and second lands being normally interconnected to said first conduit means; a drain port normally closed by said first land; and a third chamber provided between said second and third lands being normally interrupted from said second conduit means by said second land, whereby when the spool valve of said inching valve means is moved by said pedal said second conduit means is opened for establishing fluid communication between said source and said third chamber of sAid regulator valve assembly, and when the spool valve is further moved fluid under pressure conveyed to said second chamber of said inching valve means is throttled by said second orifice while at the same time said second chamber of said inching valve means is connected to said drain port of said inching valve means via said first orifice.

Claim 12

A transmission control system as set forth in claim 8, wherein a further drain port is formed on the housing of the inching valve means being always connected to said third chamber of said inching valve and further orifice is provided in said further drain port.

Claim 13

A transmission control system as set forth in claim 8, wherein said regulator valve assembly further comprises a normally closed drain port cooperable with a small diameter portion of said stepped spool valve for regulating fluid under pressure supplied to said third chamber of said regulator valve assembly when said first conduit means is interrupted by said inching valve means.

Claim 14

A transmission control system for a vehicle having fluid actuated frictional engaging means, said system comprising: a fluid pressure generating source; an inching valve having a first inlet connected to said pressure source normally being open to a first outlet and a second inlet connected to said pressure source normally being closed to a second outlet; a regulator valve assembly having a stepped spool valve slidably fitted in a housing for defining first, second and third chambers with a spring means interposed in said first chamber for urging said spool valve in one direction; means fluidically connecting said second chamber of said regulator valve with said first outlet of said inching valve; means fluidically connecting said third chamber of said regulator valve with said second outlet of said inching valve; means fluidically connecting said second chamber of said regulator valve with said frictional engaging means; means for selectively fluidically connecting said second inlet of said inching valve to said second outlet and simultaneously restricting the flow between said first inlet and said first outlet, and for selectively closing said first inlet while maintaining the fluidic connection between said second inlet and said second outlet; means for fluidically connecting said first and third chambers of said regulator valve assembly having flow throttling means therein; and means fluidically connecting said first chamber of said regulator valve assembly with a reservoir.

Claim 15

A transmission control system for a vehicle having fluid actuated frictional engaging means, said system comprising: a fluid pressure generating source; an inching valve having a first inlet connected to said pressure source normally being open to a first outlet and a second inlet connected to said pressure source normally being closed to a second outlet; a regulator valve assembly having a stepped spool valve slidably fitted in a housing for defining first, second and third chambers with a spring means interposed in said first chamber for urging said spool valve in one direction; means fluidically connecting said second chamber of said regulator valve with said first outlet of said inching valve; means fluidically connecting said third chamber of said regulator valve with said second outlet of said inching valve; means fluidically connecting said second chamber of said regulator valve with said frictional engaging means; means for selectively fluidically connecting said second inlet of said inching valve to said second outlet and simultaneously restricting the flow between said first inlet and said first outlet, and for selectively closing said first inlet while maintaining the fluidic connection between said second inlet and said second outlet; means for fluidically connecting said first and third chambers of said regulator valve assembly having flow throttling means therein; and means fluidically connecting said first chamber of said regulator valve assembly with a reservoir.

Claim 16

A transmission control system as set forth in claim 11, wherein said frictional engaging means comprises; a forward and a reverse fluid actuated clutch means; and a shaft control valve unit being connected with said means fluidically connecting said second chamber of said regulator valve with said frictional engaging means for selectively controlling a pair of fluid conduits connected with said forward and reverse clutch means.